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In the present study, a biomimetic strategy concerning to surmount the predicament of strength-toughness tradeoff in the Ni matrix composite was carried out. By assembling Ti 3 AlC 2 -based preceramic papers with pure Ni foils alternatively, a novel kind of in-situ TiC/Ni-Ni 3 (Al,Ti) composite with a mimicking nacre architecture was successfully fabricated. The results show that the grain gradient of in-situ TiC combined with γ'-Ni 3 (Al,Ti) was generated in the composite layer and alloy layer, respectively. The interlayer interface was well-bonded without microvoids, flaws, or other defects. Ascribed to an excellent combination of hard-soft laminate architecture, grain gradient as well as superior interfacial bonding, a synergy of mechanical strength and toughness in the laminated TiC/Ni-Ni 3 (Al,Ti) composites was achieved. The Vickers hardness increases gradually along alloy layer, interface, and composite layer. The flexural strength and fracture toughness were ∼18 % and ∼92 % higher than the counterpart of homogeneous TiC/Ni-Ni 3 (Al,Ti) composite. The laminated architecture enhances the efficiencies of gradient TiC grains in mechanical strengthening for required bearing and loading transmission, and toughens composite materials by interfacial delamination, cracks deflection, bridging and blunting. • Inspired by natural nacre, an in-situ laminated Ni matrix composite was successfully fabricated. • Grain gradient of TiC and Ni 3 (Al,Ti) appears in composite and alloy layers, respectively. • Gradient interface was built through mutual diffusion of Ni-Al-Ti atoms. • Laminated TiC/Ni-Ni 3 (Al,Ti) composite shows excellent combination of strength and toughness. [ABSTRACT FROM AUTHOR]

Zn has garnered increasing attention in the realm of biodegradable materials due to its moderate degradation rate and no harmful gas released during degradation. However, the poor mechanical properties of Zn necessitate improvement by alloying and deformation processing. Currently, the primary studied Zn-based alloy systems include Zn-Mg, Zn-Li, Zn-Cu, Zn-Mn, Zn-Ag, and Zn-Ca alloys. Among these alloy systems, Mg is an essential element for the human body with advantages of low cost and good ability to enhance mechanical properties of Zn. Consequently, biodegradable Zn-Mg alloy exhibits fascinating application potential. This paper provides a comprehensive overview of research progress on Zn-Mg alloys by summarizing the effects of composition and deformation processing on degradation properties, biocompatibility, and mechanical properties. Additionally, this paper highlights existing challenges and hopes to offer new perspectives and ideas for researchers engaged in the study of degradable materials. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, Ti-5Al-2.5Sn-xMo (TASxM, x = 0,5,10,15 wt%) alloys were designed and prepared. Phase compositon and microstructure analysis results indicate that the addition of Mo reduces the phase transition point of TASxM alloys, stabilizes more β phase to room temperature, and refines the α grains. The strength of the TASxM alloys exhibits a positive correlation with the increasing Mo content within 10 wt%, and the highest ultimate tensile strength (UTS) can be obtained in TAS10M (1260 MPa), which can be primarily attributed to the synergistic effects of phase transition, solid solution strengthening, and fine grain strengthening. Interestingly, the UTS of TAS15M unexpectedly decreases to 724 MPa, which is strongly influenced by the altered slip system numbers resulting from the β/α phase ratio. Even more intriguing is the observation of stress-induced martensitic transformation in the deformed TAS15M alloy, often resulting in a substantial influence on elongation. The corrosion resistance of the TASxM alloy has also been investigated through electrochemical experiments. The findings reveal that the corrosion resistance of the TASxM alloy is enhanced with the elevation of Mo content, peaking at TAS15M. This improved resistance is attributed to the augmented β phase content and the formation of protective MoO 2 and MoO 3 oxide films on the surface of alloy. • Described the evolution process of the microstructure of Ti alloys with different Mo contents. • The mechanical mechanism of TASxM alloys with different Mo contents has been analyzed. • The TAS10M sample has the best combination of UTS (∼1260 MPa) and ε f (∼8.4 %). • The TAS15M sample exhibits a dual yield phenomenon due to stress-induced martensitic transformation. • The corrosion resistance mechanism of TASxM alloys has been analyzed in combination with XPS. [ABSTRACT FROM AUTHOR]

It is difficult to fabricate dense and high-performance pure copper with most commercial medium-power fiber laser additive manufacturing machines due to its high laser reflection and thermal conductivity. The modification of the copper surface with high laser absorptance particles is an economical and effective way. However, the additions of high laser absorptance particles improve mechanical performance but worsen the conductivity of copper, and the mechanism is unclear. In this work, a comprehensive investigation of the effect of TiC nanoparticles and different copper powder sizes on the densification behavior, microstructures, mechanical properties, and electrical conductivity of LPBF-processed copper was completed. The results showed that the coarse copper powder (CCP) with TiC nanoparticles had a better adaption to processing parameters. Under the same process condition, a relative density of 98.8 ± 0.3%, ultimate tensile strength of 213 ± 1 MPa, elongation of 30.9 ± 2.9%, and electrical conductivity of 67.9 ± 0.2% IACS were achieved in CCP composite which was all superior to the fine one. The paper provides a new strategy to fabricate balanced-performance copper by common commercial LPBF devices. [Display omitted] • A new strategy to fabricate balanced-performance copper by common commercial LPBF devices. • To improve the laser absorptivity without increasing the content of the second phase. • The electrical conductivity and elongation have been both enhanced. • The defects were reduced and the twisty grains appeared after the implementation of the strategy. [ABSTRACT FROM AUTHOR]

In this paper, the effect of nitrogen doping on the mechanical properties of Zr-based bulk metallic glasses (BMGs) was studied by nano indentation experiment, and the correlation mechanism between microstructure evolution and mechanical properties was analyzed. The results show that the serrations events exhibited by metallic glasses during nanoindentation are related to the loading rates. With the decreasing loading rate, more obvious serrations events occur in the loading segment, which is attributed to the sufficient time for shear bands to multiply and propagate at low rates. The addition of nitrogen will induce the generation of more flow defects. Compared with BMGs without nitrogen, the nitrogen-doped Zr-based BMGs exhibit more serration events due to introducing more flow defects to form the shear transformation zones (STZs) and subsequently facilitating the shear bands to multiply. The possible relationships between the structural evolution, shear band initiation and propagation, and relaxation behavior of nitrogen doped and non doped metallic glasses were discussed. • Nanoindentation and relaxation behavior of nitrogen doped zirconium based bulk metallic glass was studied. • The insufficiency of transformation rate from anelastic to plastic deformation results in the serration-event disappearance. • Doping nitrogen can induce the generation of more flow defects and increase structural heterogeneity in Zr based BMG. • After doping with N, BMG will be in a more relaxed state and exhibit better creep performance. [ABSTRACT FROM AUTHOR]

The present paper comprises a detailed structural analysis of two novel compounds in the Sc-Co-Ga system: τ 3 -Sc 50 Co 13 Ga 3 (space group Fm -3; ε-Mg 26-x Ag 7+x type), and τ 4 -Sc 6 Co 1.73+x+y Ga 1-x (space group Immm; x=0.43; y=0.14; Ho 6 Co 2 Ga derivative type). Although alloys in the isothermal section are oxygen-free, the alloy of τ 3, prepared for single crystal growth via partial melting in an alumina crucible, contained a minor amount of oxygen and can be considered as oxygen-stabilized Sc 50 Co 13 Ga 3 O 1.1 (WDX-data). A search for homologous compounds in the systems Sc-{Pd,Pt}-Ga prompted the existence of two compounds Sc 54 {Pd,Pt,Ga} 17 , which from X-ray single crystal analyses proved both to be isotypic with the Hf 54 Os 17 -type structure (space group Immm). Whereas Sc 54 (Pd 0.652 Ga 0.348) 17 has a very limited homogeneity region at 850°C, Sc 54 (Pt 1-x Ga x) 17 exhibits at 850°C a large homogeneity region (0

As one of the most important additive manufacturing (AM) techniques, laser metal deposition (LMD) has been extensively studied specially during the last few years. Similar to other AM techniques, the quality of LMD parts is highly dependent on the processing parameters that need to be optimized so as to obtain geometrically accurate parts as well as favorable microstructures and, thus, mechanical properties. The present review paper therefore aims to present a critical analysis and overview of the relationship between processing parameters, microstructure, and mechanical properties of LMD components made from the Ti–6Al–4V alloy. Moreover, we discuss the applications of LMD parts in the aerospace and biomedical industries as well as the potential of LMD techniques for fabrication of more complex parts such as cellular structures. The paper concludes with a summary of the most important findings and suggestions for future research. Image 1 [ABSTRACT FROM AUTHOR]

As a duplex Mg–Li alloy, Mg–9Li–1Zn (LZ91) has attracted increasing attention, but its strength needs to be further improved. This paper aims to explore the effect of Y and Ce in different proportions on microstructures and mechanical properties of LZ91. The microstructures and mechanical properties of as-cast and cold-rolled LZ91 alloys with Y and Ce addition were investigated. The grain size of the LZ91 was refined due to the addition of Y and Ce. Y significantly strengthened LZ91 while Ce weakened the strengthening effect of Y. The mechanical properties increased first and then decreased with the content of Y and Ce, however, it still showed a strengthening effect compared to LZ91 alloys. The addition of Y caused the formation of Mg 24 Y 5 and Mg 12 ZnY. With the addition of Ce, Mg 12 Ce and CeZn 5 formed with a continuous-network distribution. Mg–9Li–1Zn-1.5Y exhibited the most excellent microstructure and mechanical properties in as-cast state (UTS, YS, and elongation are162MPa, 130 MPa and 49.6%, respectively) and cold-rolled state (UTS, YS, and elongation are 255 MPa, 231 MPa and 31.9%, respectively) states because of the prominent refinement effect of Y on α phase and the dispersion strengthening by Mg 24 Y 5. Meanwhile, the elongation of Mg–9Li–1Zn-1.5Ce after cold rolling was abnormally enhanced. This was explained that the coarse Mg 12 Ce in the as-cast state was broken into fine dispersed particles after cold rolling. This paper provides a reference for the selection and quantification of rare earth elements in duplex Mg–Li alloys. It also provides a reference way to refine large-size second phases in duplex Mg–Li alloys. • Y significantly strengthens LZ91 while Ce weakens the strengthening effect of Y. • Under cast state, Mg 24 Y5 is beneficial second phase while Mg 12 Ce is harmful phase. • The coarse Mg 12 Ce can be crushed by rolling and Ce promotes DRX during cold-rolling. [ABSTRACT FROM AUTHOR]

Al matrix composites reinforced by dual particles have attracted much attention recently. In this paper, utilizing liquid–solid reaction between ZrN powder and Al matrix, a (ZrAl 3 +AlN)/Al composite has been prepared. The in–situ synthesized ZrAl 3 and AlN particles exhibit sub–micron and nano–sized, respectively. Based on the analysis of electron back–scattered diffraction detector (EBSD) and X–ray diffraction (XRD), the extruded Al–5ZrN, Al–10ZrN and Al–4Cu–10ZrN composites all prefer to form sheet texture in the longitudinal section and can be marked as {110}<111>. It was found that the increase of particles content leads to the increase of hardness and tensile strength at both room temperature (25 °C) and elevated temperature (350 °C), whereas the introduction of Cu element results in the increase of tensile strength at room temperature but decrease at elevated temperature. It is regarded that the formation of Al 2 Cu surrounding ZrAl 3 and AlN particles may be responsible for the decreasing of tensile strength at 350 °C. This paper may be referred for designing dual–particles strengthened composites. • A (ZrAl 3 +AlN)/Al composite has been synthesizing through the reaction between Al and ZrN. • The average size of in–situ formed ZrAl 3 is less than 1 μm and the AlN is less than 50 nm. • High particles content lead to improved hardness and mechanical properties. • Cu alloying plays negative role for the tensile strength at 350 °C. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a systematic study on the interaction between particle strength, matrix ductility and the deformation mechanism in metallic syntactic foam (MSF). Packed beds of near-spherical NaCl particles (ø2-2.8 mm) were infiltrated with liquid metal to produce the required samples. The brittle zinc alloy ZA-27 and ductile Aluminium (99% Al) were used as matrix materials. NaCl particles were retained inside half of these samples to replicate MSF containing high-strength particles. NaCl was leached from the remaining samples to investigate MSF with weak particles. This procedure ensured that all samples had a near-identical matrix geometry and microstructure, thus isolating the effect of particle strength. Quasi-static compression tests were conducted and significant changes in the deformation behaviour were observed. Samples containing NaCl particles deformed in a shear-band dominated mode, whilst the ductile foam underwent layer-by-layer deformation. Highlights • The paper presents a systematic study of metallic syntactic foams. • Syntactic foam particles strongly affect the initial foam strength. • Foams with weak particles are susceptible to density gradients. • Brittle matrices or strong particles increase the likelihood of shear fracture. [ABSTRACT FROM AUTHOR]

To address the challenges of poor forming quality in the laser additive manufacturing of lightweight alloys, this paper explores an approach that integrates a laser additive manufacturing strategy for lightweight alloys with surface deformation strengthening. The study investigates the combined effects of build direction (BD) and ultrasonic surface rolling (USR) on the microstructure, residual stress, and mechanical properties of 2195 Al-Li alloy processed by laser powder bed fusion (LPBF). The results indicate that changes in BD significantly affect the growth direction of columnar grains (CGs) in the formed specimens and lead to the formation of a gradient microstructure with different characteristics under the influence of USR. When BD is 0°, the post-USR specimen exhibits the most significant deformation strengthening effect, with the high dislocation density reaching depths of up to 720 μm and compressive residual stress amplitudes up to −159 MPa. When BD is 90°, the sample shows excellent tensile performance with an ultimate tensile strength (UTS) of 386 MPa and an elongation (EL) of 8.2 %. After USR treatment, the UTS of the sample increases to 438 MPa, but the EL decreases to 5.1 %. CGs exhibit varying deformation resistances in different directions, thereby influencing the deformation strengthening effect of USR and altering the crack propagation mechanism during the tensile process. • The specimen with a building direction of 0° exhibits the most significant deformation strengthening effect. • Forces aligned along the long axis of columnar grains transmit more effectively along grain boundaries. • The combined effects of building direction and ultrasonic surface rolling can alter the tensile crack propagation path. [ABSTRACT FROM AUTHOR]

Fracturing tools for oil and gas exploitation require high mechanical properties and degradability. Zn alloys are possible to have good mechanical properties and much lower cost than widely used rare-earth Mg alloys, so it is worthy to develop Zn alloys as alternative materials. In this paper, a novel shell-like microstructure of Zn-5Mn alloy has been realized by bottom circulating water cooling. MnZn 9 phase appears by the first time in Zn-Mn alloys with Mn < 6.4 wt%. This phase leads to the formation of hard MnZn 9 /MnZn 13 core/shell structure with a high volume fraction of 76 %, dispersed uniformly in soft Zn phase. The alloy has excellent compressive properties without fracture even when stress and strain reach 2776 MPa and 80 %, respectively. Its ultimate uniform compressive stress and strain are 865 MPa and 56 % respectively, beyond widely used dissoluble Mg alloys. Weight loss rate of the Zn-5Mn alloy is two times that of pure Zn, immersed in 3 wt% KCl solution at 93°C. The shell-like Zn-5Mn alloy provides guiding significance of applying Zn alloys in fracturing tools for oil and gas exploitation. [Display omitted] • MnZn 9 phase appears by the first time in Zn-Mn alloys with Mn < 6.4 wt%. • A novel MnZn 9 /MnZn 13 core/shell structure is dispersed uniformly in Zn phase. • Zn-5Mn alloy has the best compressive mechanical properties in degradable materials. • Weight loss rate of the alloy in 3 wt% KCl at 93°C is twice that of pure Zn. [ABSTRACT FROM AUTHOR]

Aluminum matrix composites (AMCs) reinforced by Ti 3 C 2 T x are receiving increasing attention. However, the key constraints to its application breadth are the poor thermal stability and its poor interfacial bonding with aluminum (Al). In this paper, the surface modification of Ti 3 C 2 T x is carried out by chemical Ni coating, and the effects of such reinforcement on the microstructure and interfacial architecture, as well as the mechanical properties of the Al6061 composites before and after Ni-coated are compared. The results show that Ni-coated Ti 3 C 2 T x improves its dispersion in the Al melts and blocks the interfacial reaction between Al and Ti 3 C 2 T x. HRTEM analysis shows that the dense Ni nanoparticles on the surface of Ti 3 C 2 T x optimize its interfacial structure with Al. The mismatch of (102) Al3Ni //(1−11) Al is 4.3 %, indicating that the Al6061–2.5 wt% Ti 3 C 2 T x @Ni (AT2.5@Ni) composites are strengthened by the form of Al 3 Ni-Al interfacial coherence. The yield strength, tensile strength, and elongation of AT2.5@Ni composites are 122.1 MPa, 223.4 MPa, and 5.2 %, which are 53.0 %, 57.9 %, and 2.0 % higher than that of Al6061 matrix, respectively. The better mechanical properties are mainly attributed to the strong Ti 3 C 2 T x -Ni-Al 3 Ni-Al interfacial architecture formed in the composites, resulting in the effective load transfer from matrix to Ti 3 C 2 T x. • The α-Al grain size of AT2.5@Ni composites is reduced by 57.9 % compared to Al6061. • Ni nanoparticles on the Ti 3 C 2 T x surface block the interfacial reaction of Al-Ti 3 C 2 T x. • A strong Ti 3 C 2 T x -Ni-Al 3 Ni-Al interfacial bonding is constructed in the AT2.5@Ni composites. • The toughening effect of Ti 3 C 2 T x @Ni is superior to that of Ti 3 C 2 T x. [ABSTRACT FROM AUTHOR]

This paper elucidates the softening kinetics during isothermal annealing of an AlSi11 alloy manufactured by laser powder bed fusion (L-PBF) by using in situ high-energy synchrotron X-ray diffraction complemented by microstructure microscopy analysis. Annealing in the temperature range of 20 °C to 500 °C for one hour led to evolutions in the as-built L-PBF cellular structure, including partial fragmentation of the cell boundaries between 20 °C and 300 °C; the breakdown and transformation into ultrafine Si-enriched particles in the range of 300 °C to 400 °C; and subsequently coarsening at temperatures exceeding 400 °C. The evolution of the crystallite size for Si is consistent with the Ostwald ripening equation with an activation energy of 75.8 kJ mol−1, while the Al peaks registered only marginal variations through all the thermal cycle. The examination of dislocation densities and grain sizes, which varied from 4 × 1014 m−2 to 1 × 1014 m−2 and 15 µm to 13 µm respectively, in the temperature range of 20 °C to 500 °C, revealed a practical absence of recovery and recrystallization phenomena in the Al matrix. On the other hand, Si diffusion from the supersaturated Al matrix and the coalescence of particles assisted the cellular structure transformation. Thus, the decrease in yield strength observed in the AlSi11 alloy subjected to annealing treatments is primarily driven by a thermally assisted softening process, which is controlled by the diffusion of Si, rather than the annihilation of dislocations and grain growth in the Al matrix. [Display omitted] • Laser powder bed fusion produced a hierarchical microstructure in an Al-Si alloy. • High-energy synchrotron radiation revealed the softening kinetics of the alloy during in situ annealing heat treatments. • Si diffusion and the Ostwald ripening mechanism control the cellular structure transformation. • The activation energy for the cellular structure coarsening is lower than the Al grain growth. [ABSTRACT FROM AUTHOR]

In this paper, 30% Si 3 N 4 /6061Al composites were prepared by SPS process to study the influence of different pulses on the microstructure and mechanical properties of the composites. The results showed that there was a sintered connection of the reinforcement Si 3 N 4 in the composite. Moreover, with the decrease of the value of pulse condition t on : t off , the increased current would lead a rise of the local temperature in the composites, thus the connection of the Si 3 N 4 particles became serious. At the same time, the interfacial reaction became serious, and the interface morphology changed from smooth to steep and then to serration. The results of mechanical properties analysis showed that different pulse conditions had little effect on the tensile strength of composites, but they had a greater effect on the elastic modulus and plasticity. When the pulse condition was t on : t off  = 2:1, the composite had the best mechanical properties and was superior to the performance given in many literature currently. This paper attempts to provide a certain experimental basis for the preparation of aluminum matrix composites by SPS. [ABSTRACT FROM AUTHOR]

Laminated metal composites have become a key strategy for the design and manufacture of metal parts with multiple combinations of excellent properties. This paper utilizes the differences in mechanical properties and recrystallization behavior of component metals to prepare a novel 316 L/(316 L-2.5 wt%Gd)/316 L neutron shielding laminated metal composites (LMCs) through composite rolling and solution treatment processes. LMCs have an excellent combination of properties: high strength (tensile strength: 571.36 MPa), sufficient tensile ductility (fracture elongation: 60 %) and high neutron shielding properties (thermal neutron shielding rate: > 90 %). Specifically, compared to the non-composite 316 L-2.5 wt%Gd neutron shielding material, the strength of the hot-rolled LMCs has increased by 2.0 times, and the elongation at fracture has improved by 3.3 times. After solid solution treatment, the elongation of LMCs is further increased, which is 6 times higher than non-composite 316 L-2.5 wt%Gd neutron shielding materials. The specially designed soft-hard matched 316 L/(316 L-2.5 wt%Gd) heterogeneous interfaces achieved good metallurgical bonding, with significant differences in grain sizes and strains. The main reasons for the enhanced strength and plasticity of LMCs are the geometric constraints caused by the layered structure composed of ductile and brittle metallic components, as well as the back-stress strengthening and strain hardening induced by deformation incompatibility at the heterogeneous interface. • 316 L/(316 L-2.5 wt%Gd) heterogeneous interfaces with different grain sizes and obvious differences in strains were constructed. • Heterogeneous structure and interfacial constraints synergistically enhance the strength and plasticity of 316 L/(316 L-2.5 wt%Gd)/316 L laminated composites. • Provides a promising solution to the difficult problem of mutual constraints between neutron shielding properties and mechanical properties. [ABSTRACT FROM AUTHOR]

The high entropy alloys (HEAs) are widely used in high temperature service environment (such as aviation engine blades) with bright application potential in additive manufacturing. Laser powder bed fusion (LPBF) is technology currently offers the best reproducibility and dimensional accuracy for part production. The unique atomic lattice structure of HEA makes its plastic deformation mechanism different from that of traditional dilution alloy, resulting in the strengthening effect of face-centered cubic high-entropy alloy different from that of traditional metal alloy materials. In this paper, Ni 8 Cr 4 Co 4 Fe 6 W 2 was designed by means of composition control. Its spherical powders with uniform composition were successfully prepared by high temperature remelting spheroidization (PHTR) method, compared with gas atomization (GA) method. The strain rate sensitivity m values of GA-Selective Laser Melting and PHTR-Selective Laser Melting samples were 0.030 and 0.027, respectively. The hardness of Ni 8 Cr 4 Co 4 Fe 6 W 2 high-entropy alloy showed a trend of continuous increase with the decrease of grain size, while the elastic modulus didn't change much (PHTR-SLM is 193 Gpa and GA-SLM is 189 Gpa). The simulated value of the contact stress decreased by 23 % compared with the theoretical value. The contact radius increased with the increase of plastic deformation in addition to the reduction of contact pressure. The printing sample value of the elongation, yield strength (YS) and Ultimate Tensile Strength (UTS) on PHTR-SLM has increased by 39.6 %, 33.7 % and 25.9 %, respectively in additive manufacturing, compared to GA-SLM. The ability to produce refractory HEAs through PHTR method will make it possible to manufacture complex geometry shapes at a reasonable cost. ● The alloy specimens have extremely small size and obtain single FCC solid solution by SLM process. ● The strain rate sensitivity index m of PHTR-SLM sample is 0.027. ● Ni 8 Cr 4 Co 4 Fe 6 W 2 alloy shows high strength and ductility in additive manufacturing. ● The simulated value of the contact stress decreases by 23% compared with the theoretical value. [ABSTRACT FROM AUTHOR]

Heat treatment is necessary for GW63K (Mg-6Gd-3Y-0.5Zr, wt%) alloy fabricated by wire are additive manufacturing (WAAM) to improve the mechanical properties before final applications. Considering the unique solidification process and microstructure of WAAMed GW63K alloys, the heat treatment parameters must be different from the cast or forged ones. Thus, the present paper investigated the influence of solution temperature and time on the microstructure and mechanical properties of WAAMed GW63K, as well as the aging temperature and time. It was found that the as-deposited alloy exhibited fine equiaxed α-Mg grains with an average size of 13 μm and few eutectic phase Mg 24 (Gd, Y) 5 around the grains. The proper temperature of solution treatment was 480℃ and the proper time was 0.5 h, lower and shorter than cast ones. After solution treatment, the average size of α-Mg grains almost remained the same and nearly all of the eutectic phase dissolved. To exert precipitation strengthening to a larger extent, we conduct aging treatment at 175°C, 200°C, and 225°C and draw their age-hardening curves. Besides, a superior strength /ductility trade-off was obtained peak aging at 200°C for 80 h, with the ultimate tensile strength of 337±8 MPa, yielding strength of 231±2 MPa, and elongation of 8.9±1.0%. This outstanding strength can be accounted for by the refinement strengthening of fine microstructure inherited from as-deposited GW63K alloy and precipitation strengthening from dense β′ precipitates with a remarkable plate aspect ratio. Besides, suitable β′ precipitates could support a favorable work hardening effect and compatible deformation capability. • The Mg-6Gd-3Y-0.5Zr alloy with low rare earth content fabricated by WAAM has obtained fine microstructure. • The refinement of microstructure would be retained under an optimal solution treatment (480°C×0.5 h). • A superior strength /ductility trade-off with UTS of 337±8 MPa, YS of 231±2 MPa and EL of 8.9±2.0% was obtained. [ABSTRACT FROM AUTHOR]

Although copper has excellent thermal conductivity, poor wear resistance seriously limits its development. In this paper, a Cu matrix surface composite material reinforced by FeCoNiCrAl high-entropy alloy particles was prepared by friction stir processing. The microstructure and properties of the composite were investigated. The results showed that both the FSP process and the addition of HEA particles contributed to the refinement of the Cu-matrix grains. A diffusion layer with a width of about 0.8 µm was formed at the interface between the HEA particles and the Cu matrix. Compared with received Cu, the microhardness of Cu matrix in the composites was increased by 69.8%, the wear rate was reduced by 29.7%, and the wear resistance was significantly improved. Mean while, the ductility of the composite was consistent with that of the received Cu, and the thermal conductivity reached 87% of the received Cu. Therefore, this paper provided a new possibility for developing multifunctional structural materials with high wear resistance, high ductility, and high thermal conductivity. • HEA particle reinforced Cu-matrix surface composites were successfully prepared via FSP, and the grain size of the matrix was significantly reduced. • HEA particles and Cu matrix formed a diffusion layer continuous with good interfacial bonding. • Compared with traditional particle reinforcement, HEA particle was an excellent reinforcement particle. • The prepared surface composite has significantly improved wear resistance, while maintaining good ductility and thermal conductivity. [ABSTRACT FROM AUTHOR]

Over the last decade, there has been a steady increase in the amount of magnesium scrap sourced from manufacturing processes due to the rapidly growing market for magnesium alloys in various industries. As a result, the reuse of magnesium becomes extremely beneficial for cost reduction, natural resource preservation, and environmental protection, as it gives scrap magnesium a new lease on life. The reuse of AZ91 magnesium alloy chips for producing functionally graded composites reinforced with yttrium oxide (Y 2 O 3) to enhance microstructure and mechanical properties was investigated in this paper. The manufacturing method for this study involves: (1) collecting and cleaning magnesium chips, (2) pre-mixing them with Y 2 O 3 particles, (3) melting and blending the compositions using a stir casting method, and (4) finally pouring it into a centrifugal casting to produce the functionally graded composite. The microstructure of the AZ91 matrix was examined, and it indicated a well-distributed gradient of Y 2 O 3 particles with little agglomeration. The estimated concentration of particles (which ranged from 40.35% to 32.1% area) closely matched the experimental data (which ranged from 43% ± 1.5% to 28% ± 1.5% area). The study also revealed that particle concentration had a substantial influence on the mechanical properties, with the outer zone outperforming both the middle and inner zones. In the outer zone, the gradient composite had a hardness of 106.89 ± 1.25 HV, a tensile strength of 197.39 ± 2 MPa, and a compressive strength of 335.29 ± 5 MPa. Furthermore, the findings demonstrated the feasibility of employing chip waste to make graded composites, providing a feasible technique for reusing magnesium chips created during machining procedures. This research sheds new light on the use of magnesium chips as a matrix material in the casting of functionally graded composites. [Display omitted] • ·Functionally graded AZ91/ Y 2 O 3 composite using magnesium chips as matrix was produced successfully via centrifugal casting. • Microstructure analysis showed a well-distributed Y 2 O 3 particle gradient, indicating successful reinforcement integration. • The outer zone showed superior mechanical properties, with increased hardness, tensile strength, and compressive strength. • Excellent agreement of particle concentration in AZ91 matrix alloy was achieved for theoretical and experimental results. • The effect of the capture and pushing of particles during the solidification process was discussed in detail. [ABSTRACT FROM AUTHOR]

The more alloys we can make from metal scrap, the better. The present paper examines the prospect of making high entropy alloys (HEA) completely from existing commercial alloys. Three HEAs were fabricated from pure elemental billets and from scrap ingots with two different levels of impurities (2 wt% and 9 wt%): a Al 0.3 CoCrFeNi alloy with a single-phase FCC structure, a Al 0.6 CoCrFeNi alloy with a multi-phase FCC/BCC structure and a Al 0.9 CoCrFeNi alloy with a spinodal BCC/B2 structure. The effect of various impurity levels on the microstructure and mechanical properties was analysed and compared to the commercially pure HEAs in the as-cast and homogenised heat-treated conditions. The HEAs with low impurities (2 wt%) exhibited microstructural features and mechanical properties similar to that of the commercially pure HEAs. On the other hand, the HEAs with high levels of impurities (9 wt%) exhibited high strength and reduced plasticity which resulted from the refined grain structure and the precipitation of hard phases (such as Laves and carbides). This strategy shows the potential to eliminate or reduce high-cost raw materials for the fabrication of HEAs with a refined microstructure and improved mechanical properties by suitably selecting the scrap ingot streams. • Fabrication of high entropy alloys from different traditional metal scrap streams. • Effect of impurity levels on the microstructure and mechanical properties. • Lower impurity levels retain the microstructure and mechanical properties as its counterparts from pure elemental ingots. • Higher impurity levels (∼9 wt%) causes brittle phase formation with high strength and reduced plasticity. [ABSTRACT FROM AUTHOR]

In this paper, CoCrCu 1.2 FeNi high entropy alloy (HEA) was prepared by vacuum suspension melting. After 50 % cold-deformation, recrystallization annealing experiments involving the annealing temperatures of 650–950 ℃ and the annealing times of 30–120 min were carried out on the cold-deformed HEA. The microstructure and properties of the alloy were compared before and after annealing. The results showed that with the extension of annealing time and temperature, the microstructure of the alloy was gradually uniform and coarsening occurred after spheroidization. In addition, fusion and engulfment occurred in the microstructure and the microstructure size decreased first and then increased. Both the fracture strength and fracture strain of the alloy increased first and then decreased. The alloy had the best compression performance at 850 ℃/60 min. Compared with the alloy after cold-deformation, the fracture strength was increased by 79.3 %, the fracture strain was increased by more than 1 time, and the comprehensive mechanical properties were the best at 750–850 ℃. The average hardness decreased with the increase of temperature and annealing time, and the initial recrystallization temperature of the alloy was determined to be about 650 ℃. The formation of annealing twins refined the microstructure and improved the properties of the alloy. • The yield strength of cold-deformed CoCrCu 1.2 FeNi is not sensitive to the change of annealed time. • The microstructure and properties of cold-deformed CoCrCu 1.2 FeNi are sensitive to annealed temperature. • The mechanical properties of cold-deformed CoCrCu 1.2 FeNi has been effectively improved after recrystallization annealing. • Dislocation strengthening is the main strengthening mechanism of cold-deformed CoCrCu1.2FeNi. [ABSTRACT FROM AUTHOR]

Effects of different post treatments on microstructure and properties of WC–11 wt.% Co cemented carbides were investigated in this paper. The different post treatments that are carried out to the cemented carbides are (a) heating and quenching in oil bath, (b) controlled cryogenic treatment. Various mechanical and microstructural characterization of these alloys including density, coercive force, hardness, transverse rupture strength, phase composition, W solubility of the cobalt phase, martensitic phase transformation of the cobalt phase and WC grain shape were analyzed before and after post treatments. The experimental results show that post treatments have a significant influence on WC–Co cemented carbides and the details of the experimental study are presented in this paper. [ABSTRACT FROM AUTHOR]

A method for predicting fatigue life using damage variables coupled with multi-modal microstructure damage evolution was proposed after analyzing the weights of the multi-modal microstructure of directionally solidified Ni-based superalloys DZ125 in this paper. Mechanical property tests and metallographic observation tests were carried out, and the microstructure weights of the superalloys were quantified using principal component analysis (PCA) and entropy-based inter-criteria correlation (CRITIC) weight analysis. The relationship between mechanical properties and multi-modal microstructures of the superalloys was analyzed, and fatigue life was predicted using damage variables coupled with multi-modal microstructure damage evolution. The weights of multi-modal microstructures of Ni-based superalloys and the influence of multi-modal microstructural damage evolution on mechanical properties were quantified by taking into account the interactions among the microstructural factors and their combined effects, which were important references for the design and processing of the superalloy as well as the prediction of mechanical properties. [Display omitted] • Quantifying the weights of multi-modal microstructure morphology parameters. • Quantifying the weights of multi-modal microstructure. • Proposed damage variables coupled with multi-modal microstructure damage evolution. • A fatigue life prediction method coupled with multi-modal microstructure damage was proposed. [ABSTRACT FROM AUTHOR]

Yttrium silicate (Y 2 SiO 5) is considered as one of the most promising candidate materials for environmental barrier coatings. In this paper, Y 2 SiO 5 powder with a single phase were successfully prepared by high-temperature solid phase reaction method. The influence of sintering behavior on the microstructure, phase composition and mechanical properties of Y 2 SiO 5 ceramics was studied at 1400 °C. In addition, the corrosion behavior and mechanism of Y 2 SiO 5 against CMAS at 1250 °C and 1350 °C were also investigated. The results showed that the grain size of the prepared Y 2 SiO 5 ceramic was about 1.28 µm with relatively uniform, and there were many pore structures. Although Y 2 SiO 5 was still the main phase, a new small amount of Y 4.67 (SiO 4) 3 O phase was formed in Y 2 SiO 5 ceramics after sintering at 1400 °C for 25 h. The sintering phenomenon of Y 2 SiO 5 ceramics occurred at 1400 °C: the porosity decreased and the grain size grew. With the increase of sintering time, fracture toughness first increased and then decreased. The maximum fracture toughness was 4.84 MPa m1/2 after 50 h sintering. Part of Y 2 SiO 5 was dissolved in CMAS melt and Ca 4 Y 6 (SiO 4) 6 O rare-earth oxyapatite phase was generated after CMAS corrosion for 24 h. The corrosion zone could be divided into loose corrosion area (about 93 µm thickness) and dense reaction layer with Ca 4 Y 6 (SiO 4) 6 O phase (about 16 µm thickness) at 1250 °C for 24 h. With the increase of corrosion time and corrosion temperature, both the corrosion depth of CMAS and the thickness of dense reaction layer increases. The dense Ca 4 Y 6 (SiO 4) 6 O layer can effectively resist the further corrosion of CMAS melt. • Y 2 SiO 5 powder with a single phase were successfully prepared. • Y 2 SiO 5 sintered with decreasing porosity and increasing grain size at 1400 °C. • The fracture toughness of Y 2 SiO 5 was 4.84 MPa m1/2 after 50 h sintering at 1400 °C. • The loose corrosion layer and dense reaction layer are formed after CMAS corrosion. • Dense Ca 4 Y 6 (SiO 4) 6 O layer can effectively prevent further the CMAS melt corrosion. [ABSTRACT FROM AUTHOR]

The plastic deformation-assisted wire arc additive manufacturing (WAAM) technology based on the hammer-forging method has essential application prospects in preparing high-dense fine-grain aluminum alloy components. However, the existing interlayer hammer-forging method has limitations, such as insufficient hammering force and high demand for hammering times when obtaining large plastic deformation. To effectively solve these problems, this paper proposed synchronous-hammer-forging-assisted WAAM technology and systematically studied its effects on the macroscopic morphology, microstructure, pores evolution, and mechanical properties of WAAM Al-Mg alloy specimens. The results show that under the synchronous hammer-forging (SHF) condition, a large plastic deformation of 33.97% can be achieved by the 80 N hammer forging force, and the surface flatness of the specimen was significantly improved. The grain size of the specimen was reduced from 105.92 µm in the deposited state to 37.15 µm in the hammered specimen by 64.93% with a significant equiaxed effect. Simultaneously, with the application of SHF technology and the increasing hammer-forging force, the precipitated phase dominated by Al 3 Mg 2 was broken. The pores in the specimen changed from round to narrow and elongated shape with only 0.0065% porosity. The number of pores, equivalent diameter, and surface area were reduced by 68.33%, 13.75%, and 67.24%, respectively. The yield strength and ultimate tensile strength of the hammer-forged specimens reached 250.37 MPa and 315.03 MPa, respectively, which were 36.28% and 8.95% higher than those of the deposited specimens, and still maintained a high elongation rate of 36.11%. • A synchronous-hammer-forging-assisted WAAM device was developed. • 33.97% large plastic deformation was achieved using 80 N hammer-forging force. • The grain size is refined by 64.93% and accompanied by an equiaxed effect. • The porosity is decreased by an order of magnitude to only 0.0065%. • The yield and tensile strength are improved by 36.25% and 8.95% respectively. [ABSTRACT FROM AUTHOR]

Novel high-entropy alloys (HEAs) coatings deposited using physical vapour deposition technique are potential candidates of protective coatings due to their excellent performance. However, the correlation between properties and microstructure of HEAs coatings has not been completely established and the hardening mechanism remains unclear. In this paper, the AlCrNbSiTi HEA coatings were deposited under different bias voltages by radio-frequency magnetron sputtering. The morphology, chemical composition, structure, mechanical properties and thermal stability are discussed in detail. All coatings exhibit smooth surface without obvious elemental segregation and the columnar structure tends to densify with increasing bias. The coatings possess a nanocomposite structure of amorphous-nanocrystalline silicides, in agreement with the results calculated based on three phase prediction parameters (ΔH mix : enthalpy of mixing, δ: atomic size difference and Ω: ratio of entropy of mixing ΔS mix to ΔH mix). The coating deposited at bias of − 50 V presents optimal mechanical properties with nanohardness of ∼15.2 GPa, scratch crack propagation resistance of 1042 N2 and wear rate of 5.4 × 10−8 mm3N−1m−1. Annealing treatment further unravels that the presence of hard silicides is the hardening mechanism of coatings with super-hardness of ∼24 GPa. The results indicate that the AlCrNbSiTi coating is a promising protective coating with broad industrial application prospects. • Structure of coatings is a nanocomposite of amorphous-nanocrystalline silicides. • Annealing unravels hardening mechanism of coatings is presence of hard silicides. • Coating deposited at − 50 V exhibits a super-hardness of 24 GPa after annealing. • Wear mechanism of coatings is revealed with a lowest wear rate of 5.4 × 10−8 mm3/Nm. [ABSTRACT FROM AUTHOR]

In this paper, the microstructural evolution, precipitation behavior and mechanical properties of 2195 Al-Li alloys prepared by powder metallurgy (PM) combined with hot extrusion were investigated systematically. The results show that the deformation of PM 2195 Al-Li alloys during hot extrusion is dominated by the coupling of dynamic recovery with continuous dynamic recrystallization. The homogeneously distributed needle-like T 1 phase is precipitated in the matrix after T6 treatment. The T6-treated sample exhibits a perfect combination of strength and ductility, that is, ultimate tensile strength of 662 MPa, yield strength of 617 MPa and uniform elongation of 6.6 %. The strengthening of heat-treated alloys originates from densification, work hardening, grain refinement and precipitation strengthening. It is noted that the precipitation strengthening of T 1 phase is the dominant mechanism. Therefore, this work should suggest a strategy for developing novel Al-Li alloys with excellent mechanical properties. • The 2195 Al-Li alloys were successfully prepared by powder metallurgy and hot extrusion. • The tensile strength, yield strength and elongation of the 2195 Al-Li alloy were 662 MPa, 617 MPa and 6.6 %, respectively. • Mechanical properties of the alloy were enhanced by densification, work hardening, grain refinement and precipitation. • The precipitation strengthening of T 1 phase is the dominant mechanism. [ABSTRACT FROM AUTHOR]

One of the major challenges of equiatomic CoCrFeMnNi HEA is to manufacture parts with complex geometry that have higher yield strength. Equiatomic CoCrFeMnNi HEA was successfully fabricated in the present study with selective laser melting. The unique microstructure and mechanical anisotropy that generally appear in additive manufactured materials were investigated. SLM-built HEA has strongly oriented grains, dislocation networks, and nano-sized oxides. In addition, the average grain sizes were measured as 15.66 μm, 12.93 μm, and 5.98 μm on the plane perpendicular to the scanning direction (SD), transverse direction (TD), and building direction (BD), respectively. A compressive test measured outstanding yield strengths (YS) of 778.4 MPa, 766.4 MPa, and 703.5 MPa in the loading axis of SD, TD, and BD, respectively. These outstanding YSs are the result of a combination of fine grain sizes, high dislocation density and nano-sized oxides. In addition, anisotropy in mechanical properties are result from different values of Taylor factor and grain size according to the loading axis. After a compression test, the geometrically necessary dislocation density was found to differ about 2.5 times on each plane parallel to the loading axis in the same macro strain. Based on such findings, the relationship among microstructure, mechanical anisotropy and deformation mechanism are discussed in the present paper. Furthermore, the mechanical properties of SLM-built equiatomic CoCrFeMnNi HEA are predicted by using multiple strengthening mechanisms considering the microstructural characteristics. Image 1 • SLM-built HEA shows hierarchical microstructure, dislocation network, and nano-sized oxides. • SLM-built HEA shows outstanding yield strength about ∼778.4 MPa. • Anisotropic mechanical response was observed in SLM-built HEA. • Mechanical properties of SLM-built HEA was predicted by using multiple strengthening mechanism. [ABSTRACT FROM AUTHOR]

This paper reports a systematic investigation of Hastelloy-X (Hast-X) structures built by Laser Directed Energy Deposition in as-built and post heat-treated conditions. The optical microscopy shows microstructures with fine dendrites in as-built condition due to higher cooling rate during deposition, while recrystallized equiaxed grains are observed after post heat-treatment (at 1177 °C) due to recrystallization. X-ray diffraction studies reveal nickel γ-matrix with variation in crystallite size and a peak shift after post heat-treatment, primarily due to change in surface residual stress. Surface topography reveals the reduction in average roughness with post heat-treatment. Further, the maximum compressive residual stress of 350 MPa and maximum tensile residual stress of 252 MPa are observed at the surfaces of post heat-treated and as-built samples, respectively. The average micro-hardness changed from 239 HV 1.96N to 208 HV 1.96N after post heat-treatment. Single Cycle Ball Indentation studies indicated increase in energy storage capacity by a factor of 1.55 after post heat-treatment. Automated Ball Indentation studies quantify yield strength and ultimate strength as 478 MPa and 765 MPa in as-built samples, while 393 MPa and 630 MPa in post heat-treated samples, respectively. Further, crack propagation studies indicate an improvement in the fatigue life after post heat-treatment, while the specific wear rate increased by a factor of 1.72 with increased delamination in heat-treated samples. Thus, post heat-treatment of Hast-X samples changes the material properties significantly. • Post heat-treatment of Laser Directed Energy Deposited Hastelloy-X structures. • Dendritic microstructure with fine crystallites observed in as-built samples. • Homogenized microstructure and surface compressive stress after heat-treatment. • Improved fatigue behavior, energy storage and ductility after heat-treatment. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to design a new generation of FeAl-based intermetallic compounds with improved mechanical and oxidation properties. Synthesis of powders of FeAl, (Fe,Cr)Al and (Fe,Cr)Al in situ composites with 5 and 10% Al 2 O 3 contents was reported elsewhere. In this paper the sintering behavior is reported. FeAl, (Fe,Cr)Al and (Fe,Cr)Al - Al 2 O 3 powders were sintered by a hot-pressing method at 1600 °C and 5.5 GPa for 15 min to produce bulk specimens for mechanical and microstructural characterization. Microstructural characterization by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of theses nanocomposites disclosed uniform distribution of Al 2 O 3 nano-particles. XRD analysis indicated the presence of FeAl, (Fe,Cr)Al and Al 2 O 3 phases. The presence of nano-sized Al 2 O 3 particles effectively retarded grain growth by pinning the grain boundary during hot pressing. Nanoindentation tests indicated that with increasing content of Cr and Al 2 O 3 reinforcement, the hardness and Young's modulus increased, and the fracture toughness reaches a high value of 19.6 ± 0.4 MPa m1/2 for the (Fe,Cr)Al-10%Al 2 O 3 composition, with a hardness value of 21.7 ± 1.8 GPa. Nanoindentation creep tests at room temperature showed that composites with Al 2 O 3 nanoparticles had higher creep rate than FeAl and (Fe,Cr)Al. It was found that improvements in the mechanical properties of FeAl intermetallic compound can be achieved by adding Cr and uniform distribution of Al 2 O 3 nanoparticles. • Fully dense (Fe,Cr)Al-Al 2 O 3 nanocomposite was obtained by hot-pressing of MA powder. • Uniform distribution of Al 2 O 3 particles, having nanometer size, was attained in this route. • Designed nanocomposite exhibited enhanced hardness, creep resistance and fracture toughness. [ABSTRACT FROM AUTHOR]

In theory, selective laser melting (SLM) technology can fabricate various materials, including numerous metals. The mechanical properties of parts exhibit comprehensive performance, affected by many influence parameters, which are not independent, but rather demonstrate unclear and complex interactions. This paper focuses on two influence parameters, namely the placement orientation and hatch scanning angle, to explore the comprehensive effects on the mechanical properties and behaviors of 316L stainless steel. Based on the SLM process, two relevant experiments are conducted to determine the optimal placement orientation and hatch scanning angle sequentially. The results and analyses of the tensile strength, microhardness, phase constitution, and microstructure, are reported to provide reasonable explanations. The research indicates that optimal placement orientation can be obtained when the fabrication direction is perpendicular to the tensile direction. Moreover, the optimal hatch scanning angle for each slice layer is approximately 30 ° based on the optimal placement orientation, which can enhance the mechanical properties of SLM-based printed parts. • Comprehensive effects on mechanical properties and behaviors are explored. • Fracture zone, morphology, and angle are studied by means of real experiments. • Optimal placement orientation and hatch scanning angle are investigated. • This work can enhance the mechanical properties of SLM-fabricated parts. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the effects of carbon nanotubes (CNT) addition on the structure and mechanical properties of Ni 3 Al- x B (0.0 < x < 1.5 at%) intermetallic compound. Ni 3 Al- x B-1wt%CNT nanocomposite powders were first synthesized by mechanical alloying. Effects of CNT addition on the lattice strain and crystallite size of synthesized powders were investigated by means of X-ray diffraction (XRD) analysis. Scanning electron microscope (SEM) was used to study powder morphologies. Powders, synthesized by mechanical alloying, were then consolidated using spark plasma sintering (SPS), conducted at 950 °C under pressure 50 MPa. Microhardness and shear punch tests were employed to study the mechanical properties of sintered samples. Results show that CNT addition is accompanied by a decrease in crystallite size and a significant improvement of mechanical properties of Ni 3 Al- x B (0.0 < x < 1.5 at%) intermetallic compounds. Highlights • Spark plasma sintering of Ni 3 Al- x B-1wt% CNT (0.0 < x < 1.5 at%) is investigated. • Effects of CNT addition on the structure of synthesized powders is investigated. • CNT addition is accompanied with a significant improvement of mechanical properties. • Correlations between microstructure and sintering parameters are discussed. [ABSTRACT FROM AUTHOR]

Abstract A high-strength AZ80 alloy (with a tensile strength of 285 MPa, an ultimate strength of 388 MPa, and an elongation of 6.8%) has been fabricated by multidirectional forging (MDF) under air-cooling condition, at an initial temperature of 360 °C, with an accumulative strain of 1.8, with no need of ageing treatment. Extensive dynamic precipitation occurs in this sample, which deteriorates the subsequent age-hardening response but still contributes to improving the strength. In addition to the precipitation hardening caused by numerous nano-scale dynamic precipitates, the outstanding strength should also be attributed to the combined effects of other microstructural characteristics resulting from the increase of accumulative strain and decrease of forging temperature. They are 1) grain boundary strengthening by fine recrystallized grains, 2) strain hardening by the large dislocation density, and 3) texture strengthening by the low Schmid factor of basal slip. This paper provides a method of short process to manufacture high-performance large-scale AZ80 components for industrial production. Graphical abstract Image 1 Highlights • A high-strength AZ80 alloy is fabricated by multidirectional forging in air. • Dynamic precipitation extensively occurs as the accumulative strain increases. • Dynamic precipitates have advantage in maintaining the ductility compared with ageing precipitates. • Forging along two orthogonal directions shares a similar texture characteristic to extrusion. [ABSTRACT FROM AUTHOR]

Abstract This paper investigated the influences of Mg level (0.3 wt%-0.6 wt%) and heat treatment process on the phase transformation of Mg-Si phase and Fe-rich intermetallics of low pressure die-cast Al-7Si-xMg alloys. Their corresponding mechanical properties were also studied. The results indicated that at as-cast state, the addition of Mg element accelerated the formation of π-Fe phase while the mechanical properties decreased correspondingly. During the heat treatment process, the transformation of Mg-Si phase and π-Fe intermetallics were determined by the Mg content. In the alloys with low level of 0.3 wt%∼0.45 wt% Mg, the diffusion of Mg element from π-Fe phase into α-Al matrix prompted the formation of more Mg 2 Si strengthening phase, which was beneficial to the improvement of tensile properties. However, in the alloys with high level of 0.6 wt% Mg, the diffusion kinetic of Mg element from π-Fe phase into α-Al matrix was repressed due to the saturated Mg in the matrix. The π-Fe phase consumed large amount of Mg element and facilitated crack initiation which definitely weakened the strengthening effect. The mechanical properties, especially the ductility, were strongly deteriorated. In this study, the best comprehensive mechanical properties were obtained from the Al-7Si-0.45 Mg alloy, which was 267.3 MPa and 333.7 MPa, 9% for YS, UTS and Elongation, respectively. Highlights • The interaction of Mg-Si phase and Fe-rich intermetallics were deeply investigated in alloys with different Mg contents. • In the alloy with low Mg content (0.3–0.45 wt%), the strengthening was controlled by Mg 2 Si phase. • In the alloy with high Mg content (0.6 wt%), the mechanical properties were deteriorated by large amount of π-Fe intermetallics. • High Mg in the matrix depressed the dissolution of π-Fe intermetallics. [ABSTRACT FROM AUTHOR]

Abstract This paper aims at studying microstructure and mechanical properties of spark plasma sintered (SPSed) Stellite®-6 cobalt-based superalloy. SPS is a sintering technique, based on a relatively fast resistance heating using a pulsed current. Fast sintering process, associated with minimum grain growth, results in excellent mechanical properties. Samples were sintered at temperatures ranging from 950 to 1100 °C. Microstructure of samples were studied using scanning electron microscope (SEM), energy-dispersive X-ray spectroscope (EDS), X-Ray diffraction (XRD), and optical microscope. Hardness, impact test, as well as room and high temperature compression tests were used to evaluate the effects of sintering temperature and duration on the mechanical properties of SPSed samples. Results show that optimum mechanical properties can be obtained after sintering at 1050 °C for 10 min. The correlation between sintering parameters, microstructure, and mechanical properties are discussed. Highlights • Spark plasma sintering of Stellite superalloy is investigated. • Optimum mechanical properties can be obtained after sintering at 1050 °C for 10 min. • Correlations between microstructure and sintering parameters are discussed. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the crystallographic orientation relationship between TiB 2 particles and α-Mg phase is identified by TEM to clarify the grain refinement mechanism of TiB 2 particulate reinforced AZ91 composites. The influence of the content of TiB 2 particles on the grain size and mechanical properties of TiB 2 /AZ91 composites is investigated. The experimental result reveals that the TiB 2 particles can refine α-Mg grains in the AZ91 matrix, and with TiB 2 particles increased, the size of α-Mg grains in the composite decreases significantly. There exists a well-defined crystallographic orientation relationship between TiB 2 and α-Mg matrix, which is (0001) TiB 2 ∕ ∕ (10 1 ¯ 1) α − Mg , [ 1 ¯ 2 1 ¯ 0 ] TiB 2 ∕ ∕ [ 1 ¯ 2 1 ¯ 0 ] α − Mg in the present study. In the meanwhile, the lattice disregistry along the specific orientation relationship is 8.30% based on the theoretical calculation, confirming that TiB 2 particles can act as the effective heterogeneous nucleation site of α-Mg grains in TiB 2 /AZ91 composites. Furthermore, the Brinell hardness, ultimate tensile strength and elongation of the composite are increased simultaneously with the increase of TiB 2 particles, which are attributed to the uniform TiB 2 particles dispersion, grain refinement strengthening and particles strengthening. Highlights • α-Mg grains size decreases with increasing TiB 2 particles. • The OR between TiB 2 particles and α-Mg phase is identified experimentally. • Nucleation mechanism of TiB 2 /AZ91 composites is clarified. • The hardness, strength and elongation of composites are improved simultaneously. [ABSTRACT FROM AUTHOR]

Abstract Al-6Cu-6Mg-5Sn-3Ga- x In (x = 0, 0.5, 1, 3, 5. mass. fraction) alloys were prepared using melting and casting technique. The microstructures and properties of the alloys were investigated by X-ray diffraction, scanning electronic microscope/EDX, electron microprobe analysis, Vickers hardness, compression properties, immersion tests and electrochemical measurements. The results show that the main phases of the alloys with the indium element consist of α -Al, Al 2 MgCu, Mg 2 Sn and Al-In eutectic phases. The Al-In phases segregates in α -Al grain boundaries. The gallium elements solid solution in the matrix alloys. When the addition of In contents is 1 mass.%, the hardness of the Al-6Cu-6Mg-5Sn-3Ga-1In alloy reaches to 142HV, and the compressive strength up to 582 MPa. The Mg 2 Sn and the Al-In eutectic phases are the source of the degradation reaction, and the driving force to continue is the concentration of Al in the eutectic phase. The relationship between the degradation corrosion rate and temperature, indium element content and other factors were also discussed in this paper. Graphical abstract Image 1 Highlights • Microstructure, mechanical properties and corrosion behavior of Al-6Mg-6Cu-5Sn-3Ga- x In alloys were firstly investigated. • The investigated alloys mainly consist of α -Al matrix, Al 2 MgCu, Mg 2 Sn and Al-In eutectic phase. • The investigated alloy has a maximum degradation rate reaches 98.51 mg/(cm2 h) at 93 °C. [ABSTRACT FROM AUTHOR]

Abstract The study concerning the second phase reinforced YAG matrix composites is few although YAG is well known as a desirable thermo structural ceramic. In this paper, low-cost 3D carbon fiber needled felt was used as reinforcement to improve the fracture toughness of YAG, and the carbon fiber needled felt reinforced YAG (C/YAG) composite was fabricated through vacuum impregnation-drying-heat treatment, using the Y 2 O 3 -Al 2 O 3 sol with a high solid content as raw material. The microstructure, mechanical properties, thermal stability and oxidation resistance of C/YAG composite were carefully investigated. Due to the characteristics of reinforcement and the microstructure, the as-fabricated C/YAG composite showed non-catastrophic failure behavior and much higher fracture toughness compared with monolithic YAG ceramic. The flexural strength of C/YAG composite was well retained after annealed at 1700 °C and 1800 °C under inert atmosphere. Although the chemical inertness between carbon fiber and YAG was confirmed up to 1800 °C, the physical bonding of interface was enhanced during annealing, which led to the decrease of fracture work, especially at 1800 °C. The oxidation resistance of C/YAG composite was related to the cracks and pores since YAG is immune to oxidation. The changes of microstructure and flexural strength after oxidation at 1200 °C, 1400 °C and 1600 °C were characterized and analyzed. Highlights • Low-cost 3D carbon fiber needled felt reinforced YAG composite is fabricated. • The fracture toughness of composite is twice more than that of monolithic YAG. • The composite shows favorable thermal stability and oxidation resistance. [ABSTRACT FROM AUTHOR]

Abstract In this paper, oxidized-silicon carbide particle/aluminum 6061 (oxidized-SiC p /Al6061) composites were fabricated using a spark plasma sintering technique. The microstructure, mechanical properties, and wear behavior of oxidized-SiC p /Al6061 composites were investigated. The results revealed an improvement in interfacial bond strength between Al6061 and oxidized SiC p due to the formation of an MgAl 2 O 4 continuous phase and suppression of brittle Al 4 C 3 formation at the interfacial layer. Hardness (∼145 HV), ultimate tensile strength (∼226 MPa), and elongation (10.8%) were enhanced by 75%, 26%, and 32%, respectively, for the composite containing 1400°C-oxidized SiC p , compared with those reinforced with as-received SiC p. The friction coefficient and specific wear rate of oxidized-SiC p /Al6061 composites were reduced by 7% and 17%, respectively; this is attributable to the improved hardness and strength of the composite and the transition of wear mechanisms from a combination of adhesive and fatigue wear to abrasive wear. Quantitative correlations among yield strength, ultimate tensile strength, and interfacial bond strength in SiC p /Al6061 composites were analyzed for the first time. Highlights • Oxidized-SiC p /Al6061 composites were prepared by spark plasma sintering. • Interfacial layer between oxidized-SiC p and Al6061 matrix was investigated. • The interfacial bond strength between oxidized SiC p and Al6061 matrix was estimated. • Mechanical properties and wear resistance of the composites were improved. • New quantitative correlations among the strengths of the composites was analyzed. [ABSTRACT FROM AUTHOR]

Abstract The paper presents the fabrication of (0.6–3.0 wt%) Y 2 O 3 -Ti6Al4V composites by spark plasma sintering (SPS) with the sintering heating rate of 100 °C/min and the sintering temperature of 900 °C. Ti6Al4V powders and Y 2 O 3 powders were admixed by rocking mill for 8 h at 30 Hz. Scanning electron microscopy (SEM) equipped with complete energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) were used to characterize the as-received Ti6Al4V powders, Y 2 O 3 powders, the admixed composite powders and the sintered samples. The microhardness, the compressive yield strength and the ultimate strength of as-sintered samples at room temperature were enhanced up to 464.1HV, 1346 MPa and 1583 MPa respectively with a plastic strain of 19.1%, when 2.0 wt% Y 2 O 3 was introduced. The mechanical behaviors of 2.0 wt% Y 2 O 3 -Ti6Al4V composite at 450 °C were also carried out with the yield strength of 832 MPa and the ultimate strength of 1088 MPa. Compared with the sintered Ti6Al4V, the 2.0 wt% Y 2 O 3 -Ti6Al4V composite has higher yield strength and ultimate strength at elevated temperature with the increment of 54% and 37%, respectively. The mode of fracture was transformed from ductile fracture to a combination of ductile and brittle fractures with the increase of Y 2 O 3 content. Highlights • The Y 2 O 3 -Ti6Al4V composite was fabricated by spark plasma sintering. • 2.0 wt% Y 2 O 3 -Ti6Al4V composite demonstrated superior mechanical properties. • The compression fracture type of Y 2 O 3 -Ti6Al4V composite was under discussion. [ABSTRACT FROM AUTHOR]

Microstructures and mechanical properties of Ni matrix composites reinforced with amorphous SiO 2 particles by in-situ pyrolysis of polycarbosilane (PCS) coated on Ni powders were studied in this paper. The submicron spherical amorphous SiO 2 particles instead of traditional SiC uniformly distributing in the composites result from the generated silicon source by PCS pyrolysis combined with oxygen impurity in the preparation. The prepared composites achieve high yield strength, 172 MPa, and ultimate tensile strength, 494 MPa, as well as outstanding ductility, total elongation 28.4 %, which is improved 13.9 %, 50.6 % and 160.6 % compared with those for pure Ni samples, respectively. The effects of solid solution strengthening, grain refinement strengthening, reinforcement particle strengthening and dislocations behavior of at amorphous/crystalline interface on the combination of high strength and ductility of the composites were discussed. [Display omitted] • Amorphous SiO 2 reinforced Ni matrix composites were fabricated by in-situ pyrolysis of polycarbosilane coated on Ni powders. • Amorphous SiO 2 instead of crystalline SiC formed by the combination of silicon generated in the pyrolysis with oxygen. • The composites exhibit a combination of excellent tensile strength and ductility. [ABSTRACT FROM AUTHOR]

Copper-tungsten (Cu-W) composites with a copper content larger than 50 vol% are expected to have a good combination of electrical conductivity and mechanical properties. However, it is difficult to synthesize these types of composites using the conventional manufacturing routes. In this paper, W skeletons with a high porosity up to 80 ± 0.8% and well-aligned microstructures were prepared by directional solidification of aqueous slurries of W followed by ice sublimation and heat treatment. Tungsten reinforced copper matrix composites (e.g., Cu-15 vol% W composites) were fabricated by infiltration of Cu into the W skeleton structures, and their microstructure, electrical conductivity and mechanical properties were studied. The synthesized Cu-15 vol% W composites exhibited alternately patterned Cu and W microstructures and showed a good combination of electrical conductivity of 78 ± 2% IACS and hardness of 136 ± 6HV. The strengthening mechanisms of these Cu-15 vol% W composites were identified as the formation of tungsten network structures which support and strengthen the copper matrix. Residual pores in the W lamellae and weak interfaces of copper-tungsten caused the initiation and propagation of cracks, and the fracture mode of Cu-15 vol% W composite was polymerization induced ductile fracture. • Cu–W composites with high hardness and electrical conductivity were fabricated. • Freeze-casting method combined with infiltration sintering was applied. • The tungsten network structure supports and strengthens the copper matrix. [ABSTRACT FROM AUTHOR]

This paper takes the recycled 7075 aluminum alloy as the object to study its smelting, extrusion and heat treatment processes. The composition, microstructure, mechanical properties and corrosion properties of recycled 7075 aluminum alloys were characterized by spectrometer, optical metallographic microscope, universal tensile testing machine, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results showed that the composition distribution of recycled 7075 aluminum alloy ingots was more uniform and the microstructure was more optimized. The tensile strength, yield strength and elongation of recycled 7075 aluminum alloy plates were higher than American Society of Testing Materials (ASTM) standard. The recycled 7075-T6 aluminum alloy plates had good corrosion resistance to salt spray. This paper aims to provide guidance for the smelting, extrusion and heat treatment processes of scrap aircraft aluminum alloy regeneration process, and to lay the foundation of the recovery and reutilization of scrap aircraft aluminum alloys. • We obtain the recycled 7075 aluminum alloy using scrap aircraft aluminum alloys. • A method is proposed to prepare the recycled 7075 aluminum alloy ingot. • The level-maintained reuse of scrap aircraft aluminum alloys is realized. • The extruded plates are obtained with one-step extrusion. • The mechanical properties of the extruded plates are better than ASTM standard. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we have developed a cyan mechanoluminescence material Ba 2 Zr 2 Si 3 O 12 : Eu2+, Dy3+ via a solid-state reaction. The crystal structure, photoluminescence and mechanoluminescence (ML) of this phosphor have been systematically investigated. The results showed that the ML intensity increased with Dy3+ concentration from 0.5 to 3 at.% and then reduced following a further increase in Dy3+ content. In addition, the maximum ML intensity was obtained for Ba 2 Zr 2 Si 3 O 12 : 0.02Eu2+, 0.03Dy3+. In particular, the ML spectrum was similar to the PL and afterglow emission spectra with a slight red shift, showing a dominant peak at approximately 508 nm that was generated from the 5d-4f transition of Eu2+. Furthermore, when the decay time was less than 1 h, the ML intensity rapidly decreased following an increase in the load circle. Following an increase in decay time, the ML intensity was stable and was hardly affected by the load circles. The thermoluminescence (ThL) results have shown that the addition of Dy3+ can create three types of traps with trap depths of 0.682, 0.742 and 0.79 eV. Through combination of the ML and ThL results, the ML mechanism can be explained by the detrapping process of the electrons in shallow and deep traps that were induced by piezoelectricity. The relation between the ML intensity and compressive stress was nearly linear in the test range, indicating that the sample can be used as sensors to detect stress. Furthermore, a cyan ML light can clearly be observed by the naked eye in the dark, which suggested that Ba 2 Zr 2 Si 3 O 12 : Eu2+, Dy3+ can visualize the stress in an object. Highlights • A cyan mechanoluminescence material was prepared by solid-state reaction. • A cyan mechanoluminescence light can be observed by the naked eye. • The persistent luminescence of material is related with trap concentration. • Different traps affect the mechanoluminescence properties. • The ML mechanism can be explained by the detrapping process of the electrons. [ABSTRACT FROM AUTHOR]

In this paper, in-situ submicron TiB 2 particles (2.5 wt.%) reinforced AZ91 matrix composites are processed by the master alloy method combined with an optimized SHS technique. The effect of TiB 2 particles on the microstructure, ageing behavior and mechanical properties of Mg matrix composites is investigated. The results reveal that only TiB 2 phase is in-situ formed in the Al-TiB 2 master alloy and exhibits the size distribution of 100 nm–700 nm. Compared with the unreinforced AZ91 alloy, the grain size and morphology of Mg 17 Al 12 phase in as-cast composites are much refined. The ageing process of composites is accelerated and the peak-aged time of composites decreases from 42 h to 22 h significantly with the introduction of TiB 2 particles. Large numbers of fine Mg 17 Al 12 in composites preferentially precipitate at grain boundaries and near TiB 2 particles regions. In addition, the hardness, yield strength, ultimate tensile strength and elongation of as-cast composites are improved by 16.1%, 53.0%, 26.3% and 25.6%, respectively. After T6 heat treatment, the strength of composites is increased further due to large amounts of submicron Mg 17 Al 12 phase, and the age hardening efficiency of composites is higher than that of AZ91 alloy. [ABSTRACT FROM AUTHOR]

This paper is focused on the analysis of the changes in the structure and properties of metal matrix composites (MMCs) based on iron (Fe) material with tungsten carbide (WC), silicon carbide (SiC) and graphite microadditives. The synergy effect of the content of different carbides and graphite on MMCs properties was investigated using the simplex lattice design method. It was found that with the addition of carbides, namely WC and SiC, the ferrite content increases from 5 to 8% in the base material to 45% and 70% respectively. Depending on the percentage and the composition of reinforcing particulates MMCs hardness may decrease up to 25% or increase up to 30% in comparison with the base material. The residual porosity changes slightly, no more than 10%, even with an increased content of carbides and graphite, and relative volume changes of samples are between −2 to +1%. [ABSTRACT FROM AUTHOR]

This paper studies the sintering, microstructure, mechanical, and oxidation properties of TiC-Ni-Mo cermets obtained from ultra-fine TiC powders. The TiC powders were synthesized from a novel carbon coated precursors carbothermal reduction method. The weight percentage of TiC was 75 wt%, the Mo phase increased from 0 to 20 wt%, and the Ni phase balanced the composition. At a sintering temperature of ∼1500 °C for 1 h with argon flowing, the utilization of the ultra-fine TiC powders results in high relative density (>98%), fine microstructure, and good mechanical properties. The Mo substitution can further: (1) enhance the relative density to above 99.5%; (2) lead to the formation of core-rim structure; (3) refine the grain size from ∼1.3 ± 0.1 to ∼1.0 ± 0.1 μm with Mo content at 10 wt%; (4) enhance the hardness and fracture toughness to 14.9 ± 1.2 GPa and 15.4 ± 1.1 MPa m 1/2 with Mo content at 10 wt%; (5) greatly enhance the oxidation resistance with 20 wt% Mo substitution. [ABSTRACT FROM AUTHOR]

Selective electron beam melting (SEBM) is a promising manufacturing technology, which offers several processing parameters to select to change microstructure and even to tailor the microstructure. In this paper, the influence of beam current on microstructure, phase composition, grain boundary misorientation and mechanical performances of a Ti-47Al-2Cr-2Nb alloy produced by SEBM was investigated. The results illustrated that with enhancing the beam current, the microstructure changed from fine duplex with the average grain size of 3.02 μm to near gamma structure with the average grain size of 6.28 μm. The volume fraction of B2 phase gradually increased from 2.8% to 18.8% with increasing beam current from 4.5 mA to 8.5 mA. The high angle grain boundary (89 ± 3°) gradually increased and the low angle grain boundary (1–5°) continuously decreased with the enhancing beam current. The ultimate compression strength (UCS) of SEBM-processed TiAl alloy decreased from 2930.95 MPa to 2456.82 MPa and the strain (δ) decreased from 34.82% to 27.44% with increasing the beam current from 4.5 mA to 8.5 mA. Recovery and recrystallization could be observed within the as-built samples, and the effect of beam current on these processes was investigated. [ABSTRACT FROM AUTHOR]

Effect of molybdenum on phases, microstructure and mechanical properties of Al 0.5 CoCrFeMo x Ni ( x  = 0–0.5 mol) high entropy alloys has been investigated in this paper. The microstructure, phase constituents and mechanical properties of the alloys have been studied using scanning electron microscopy, X-ray diffraction, transmission electron microscopy, compressive and hardness tests. The possible equilibrium phases existing in the alloys have also been evaluated using the Thermo-Calc program. The as-cast Al 0.5 CoCrFeMo x Ni alloys have typical dendrite microstructure. The alloys with x  = 0 and 0.1 consist of FCC and (Ni,Al)-rich ordered BCC phase, while the other four alloys are composed of FCC, (Ni,Al)-rich ordered BCC phase and (Cr,Mo)-rich σ phase. The thermodynamic calculation shows that Mo changes the phase formation order, mole fraction and composition of the equilibrium phases in the Al 0.5 CoCrFeMo x Ni alloys. The addition of Mo enhances formation of σ phase in the Al 0.5 CoCrFeMo x Ni alloys, improves the hardness and compressive strength of as-cast alloys, and reduces the ductility of the alloys. The Al 0.5 CoCrFeMo 0.3 Ni and Al 0.5 CoCrFeMo 0.4 Ni alloys have balanced properties of compressive strength and ductility. Al 0.5 CoCrFeMo 0.3 Ni alloy has a σ 0.2 of 814 MPa, an ultimate strength of 2101 MPa, and a fracture strain of 31%, while Al 0.5 CoCrFeMo 0.4 Ni alloy has a σ 0.2 of 1091 MPa, an ultimate strength of 2117 MPa, and a fracture strain of 18%. [ABSTRACT FROM AUTHOR]