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The present paper investigates the effect of carbon nanofibers (CNFs) on the microstructure and mechanical properties of Carbon fiber reinforced carbon and silicon carbide binary matrix (C/C–SiC) composite prepared by using the reactive melt infiltration technique. The CNFs used in this paper were generated through in-situ reaction in the pores of C/C preforms using the chemical vapor deposition. Results indicate introducing additional carbon sources in the form of CNFs in the C/C preform can remarkably improve the permeability of molten Si, resulting in higher density and more uniform microstructure of the RMI-deriver C/C–SiC composites. Consequently, the in-situ formation of CNFs reduces the residual Si content by 64.71% and increases the mechanical strength and modulus at room temperature by [22.31% and 17.89%] and after heat treatment at 1500 °C by [35.6% and 47.48%] with respect to no-CNF containing composites due to a lower amount of residual Si content and additional reinforcement effect of the unreacted CNFs. [ABSTRACT FROM AUTHOR]

Lightweight bent aluminum profiles are widely utilized in transportation fields. In this paper, the torsional channel self-bending extrusion process (TCSE) was adopted to machine AA6063 bent aluminum profiles in a single operation to verify the process's feasibility. Effects of extrusion parameters on the curvature, microstructure, and mechanical properties of the profiles were researched, and the extrusion process was simulated. The results show that the extruded profiles had good curvature stability. The grains were equiaxed in the cross longitudinal section, and the grain size at the outside diameter (OD) position was smaller than the inside diameter (ID) position. When the difference in deformation temperature at the OD edge was above 31 K, a smaller peripheral coarse grain (PCG) layer was formed at the OD edge with a thickness of about 400 μm, resulting in reduced hardness. The Mg2Si particles served as the main strengthening phase, which increased in number and decreased in size with increasing billet temperature and extrusion speed. Increasing the billet temperature and speed improved the mechanical properties of the material, with an increase in average hardness of 55.9% and 19.5%, and ultimate tensile strength (UTS) of 12.5% and 7.1%, respectively. By comprehensively considering the factors of extrusion load, microstructure, and mechanical properties, the optimum bent profile for different curvatures was determined. When a large curvature (≥328.67 mm) was required, it was preferred to increase the billet temperature. When a smaller curvature (≤328.67 mm) was required, it was advisable to increase extrusion speed. [ABSTRACT FROM AUTHOR]

TiAl-based alloys represent a novel class of lightweight, high-temperature structural materials that exhibit exceptional properties, including low densities, high specific strength, and remarkable thermal resistance. These properties make them exceedingly promising for supplanting nickel-based superalloy in the production of pivotal components for aerospace, marine, and automotive engines. Regrettably, like most intermetallic compounds, TiAl-based alloys are subject to certain shortcomings, such as room-temperature brittleness, deformation difficulties, and susceptibility to cracking, which present challenges for shaping these materials into intricate forms using traditional processing methods. In this regard, additive manufacturing (AM), with its high processing freedom and energy, has emerged as a revolutionary technology for the fabrication of complex structural components of TiAl-based alloys. However, AM TiAl-based alloys are still plagued by issues such as cracking, porosity, and uneven microstructure. Therefore, various post-processing techniques were employed to tune the microstructure, and thus enhance the performance of AM TiAl-based alloys. This paper reviews the research progress of AM TiAl-based alloys, summarizing the effects of process parameters, alloying, heat treatment, and surface treatment on the microstructure and mechanical properties of these alloys. Additionally, it discusses the challenges and prospects for the future development of AM TiAl-based alloys. [ABSTRACT FROM AUTHOR]

In industrial production, the deformation inhomogeneity after metal forging affects the mechanical properties of various parts of the forgings. The question of whether the organization and mechanical properties of β-titanium alloy can be improved by controlling the amount of forging deformation needs to be answered. Therefore, in this paper, a new sub-stable β-Ti alloy TB 18 (Ti-5.3Cr-4.9Mo4.9V-4.3Al-0.9Nb-0.3Fe) was subjected to three different levels of deformation, as well as solid solution-aging treatments, and the variation rules of microstructure and mechanical properties were investigated. During the solid solution process, the texture evolution pattern of the TB18 alloy at low deformation (20–40%) is mainly rotational cubic texture deviated into α-fiber texture; at high deformation (60%), the main components of the deformed texture are α-fiber texture with a specific orientation of (114)<1 13 - 3>. After subsequent static recrystallization, the α-fiber texture is deviated to an α*-fiber texture, while the specific orientation (114)<1 13 - 3> can still be inherited as a major component of the recrystallized texture. The plasticity of the alloy in the normal direction (ND) after the solid solution is influenced by the existence of the <110>//ND texture, and the plasticity of the alloy in the ND direction after aging is determined by a combination of the volume fraction of the <110>//ND texture in the matrix phase and the volume fraction of [11 2 - 0]α//ND in the α phase. The results show that it is feasible to change the characteristics of the recrystallization texture of TB18 by controlling the deformation level of hot forging, thus realizing the modulation of the mechanical properties. [ABSTRACT FROM AUTHOR]

The study of alkali-activated materials as a replacement for portland cement has been growing in recent years due to the sustainable nature of these materials. Nevertheless, ternary alkali-activated pastes using waste glass as a precursor have been insufficiently studied concerning their rheological, mechanical, and microstructural properties. In addition, there is a lack of research studying alkali-activated mixtures using basic oxygen furnace (BOF) slag and glass waste as precursors. Therefore, this paper aims to study the effect of glass powder (GP) content as a precursor, the effect of the activator ratio in alkali-activated ternary pastes of BOF slag, metakaolin (MK), and GP, and the influence of the Na2SiO3/NaOH ratio on its mixtures. The activator solutions of NaOH and Na2SiO3/NaOH were used in the production of the pastes. The liquid/solid ratio was kept fixed at 0.6 and the molarity of the NaOH solution was fixed at 12 M, seeking to analyze the impact of the Na2SiO3/NaOH ratio, with adopted values of 0.75, 1.5, and 2.5. We also aimed to study the impact of the glass content in the mixture for the values of 10%, 20%, and 25%, replacing the BOF slag. The workability by the minislump test, rheology, compressive strength for 1 and 28 days, and microstructural parameters were analyzed. ANOVA was performed to determine the significance of variables in the workability and compressive strength parameters. Pastes with the highest activator ratio (Na2SiO3/NaOH=2.5) produced better compressive strength (34.74 to 36.11 MPa) and lower minislump spreads (90 to 98 mm) compared with the mixtures with Na2SiO3/NaOH=1.5 and 0.75, besides indicating a denser microstructure, linked to higher production of aluminosilicate gels. Higher GP contents generated pastes with lower mechanical performance (16.7 MPa for Na2SiO3/NaOH=0.75) and microstructural qualities, albeit with better workability (124-mm minislump spread). [ABSTRACT FROM AUTHOR]

This paper is a study of the mechanical properties and microstructures of the similar friction weld joints (TiAl6V4 and AA2024) using a servo-controlled Rotary Friction Welding (RFW) system. The friction welding operations were performed with seven different values of the friction pressure in the range of 2–14 MPa. The temperature is recorded during friction welding tests using k-type thermocouples. Tensile tests and microhardness measurements were carried out to obtain the mechanical properties of the friction weld joints. Microstructural changes of individual zone of the friction welds were investigated using an optical microscope (OM), and the fracture surfaces were observed using a scanning electron microscope (SEM). For AA2024, the fracture occurs most frequently in the central zone, resulting in lower tensile strength values, while for TiAl6V4, the fracture is occurs outside the friction weld interface, indicating that the friction weld joint is more resistant than the base metal. Microscopic analysis of the fracture surfaces of the AA2024 samples revealed diverse morphologies, with rough cupular surfaces predominating, indicating a dominant ductile fracture mode. Similarly, TiAl6V4's friction welded specimen also exhibited cupules of various sizes across its surface, primarily associated with a ductile fracture mode. Overall, the optimal friction pressure values (respectively 8 and 10 MPa for TiAl6V4 and AA2024) correspond to the highest values of the mechanical properties. [ABSTRACT FROM AUTHOR]

This paper presents a study on the combined use of two by-products, namely quarry dust (QD) and ferronickel slag (FNS), as a full substitute for natural sand to improve the greenness of concrete production. Quarry dust was used in increments of 25% to a maximum of 75% substitution, where nickel slag was used as the remaining proportion of fine aggregate. All the combinations of quarry dust and nickel slag were found to be compliant with AS 2758.1 and they showed notably better grading than 100% sand. In this research, standard concrete tests, such as the slump test for fresh concrete, and compression, tensile and shrinkage tests for hardened concrete, were conducted. Scanning electron microscopy and X-ray diffraction analysis were also conducted for microstructural investigation. The results concluded that the combinations of quarry dust and nickel slag in concrete as a whole substitution of sand provide similar results for these properties. Specifically, 25% quarry dust with 75% nickel slag proved to be the most promising alternative to sand, with compressive and splitting tensile strengths of 62 and 4.29 MPa, respectively, which were 16% and 20% higher than those of the control mix. Also, lower drying shrinkage was observed for this combination compared to the control mix. The higher strength is attributed to the rough texture and angular shape of both quarry dust and nickel slag providing a better mechanical interlocking. The validity of this result has also been confirmed through image analysis of micrographs from various specimens. In microstructural investigations, specimens with QD and FNS exhibited fewer voids and a more compact surface compared to the control specimen. This shows the potential for further research into the use of quarry dust and nickel slag in the production of green concrete. [ABSTRACT FROM AUTHOR]

The primary focus of the current paper centers on the microstructures and mechanical properties exhibited by a Ti-30Nb-12Zr-5Ta-2Sn-1.25Fe (wt. %) (TNZTSF) alloy that has been produced through an intricate synthesis process comprising cold-crucible induction in levitation, carried out in an atmosphere controlled by argon, and cold-rolling deformation (CR), applying systematic adjustments in the total deformation degree (total applied thickness reduction), spanning from 10% to 60%. The microstructural characteristics of the processed specimens were investigated by SEM and XRD techniques, and the mechanical properties by tensile and microhardness testing. The collected data indicate that the TNZTSF alloy's microstructure, in the as-received condition, consists of a β-Ti phase, which shows polyhedral equiaxed grains with an average grain size close to 82.5 µm. During the cold-deformation processing, the microstructure accommodates the increased applied deformation degree by increasing crystal defects such as sub-grain boundaries, dislocation cells, dislocation lines, and other crystal defects, powerfully affecting the morphological characteristics. The as-received TNZTSF alloy showed both high strength (i.e., ultimate tensile strength close to σUTS = 705.6 MPa) and high ductility (i.e., elongation to fracture close to εf = 11.1%) properties, and the computed β-Ti phase had the lattice parameter a = 3.304(7) Å and the average lattice microstrain ε = 0.101(3)%, which are drastically influenced by the applied cold deformation, increasing the strength properties and decreasing the ductility properties due to the increased crystal defects density. Applying a deformation degree close to 60% leads to an ultimate tensile strength close to σUTS = 1192.1 MPa, an elongation to fracture close to εf = 7.9%, and an elastic modulus close to 54.9 GPa, while the computed β-Ti phase lattice parameter becomes a = 3.302(1) Å. [ABSTRACT FROM AUTHOR]

The early strength of geopolymers (GPs) and their composites is higher, and the hardening speed is faster than that of ordinary cementitious materials. Due to their wide source of raw materials, low energy consumption in the production process, and lower emissions of pollutants, they are considered to have the most potential to replace ordinary Portland cement. However, similar to other inorganic materials, the GPs themselves have weak flexural and tensile strength and are sensitive to micro-cracks. Improving the toughness of GP materials can be achieved by adding an appropriate amount of fiber materials into the matrix. The use of discrete staple fibers shows great potential in improving the toughness of GPs. Sisal is a natural fiber that is reproducible and easy to obtain. Due to its good mechanical properties, low cost, and low carbon energy usage, sisal fiber (SF) is a GP composite reinforcement with potential development. In this paper, the research progress on the effect of SF on the properties of GP composites in recent decades is reviewed. It mainly includes the chemical composition and physical properties of SFs, the preparation technology of sisal-reinforced geopolymers (SFRGs), the microstructure analysis of the interface of SFs and the GP matrix, and the macroscopic mechanical properties of SFRGs. The properties of SFs make them have good bonding properties with the GP matrix. The addition of SFs can improve the flexural strength and tensile strength of GP composites, and SFRGs have good engineering application prospects. [ABSTRACT FROM AUTHOR]

The poor mechanical and tribological properties limit the higher requirements of aluminum alloys in engineering and industrial applications, which leads to the rapid development of aluminum matrix composites (AMCs). Particulate reinforced AMCs have attracted extensive attention in automobile, electronics and military industries due to their low density, high strength, and excellent wear resistance. However, the interfacial reaction between reinforcements and the Al matrix tends to occur in conventional preparation processes owing to the higher reaction temperatures. The spark plasma sintering (SPS) technique is considered to be an efficient method for the fabrication of metal matrix composites, which can achieve rapid sintering, lower sintering temperatures, and higher densities than conventional fabrication processes. In addition, SPS can produce AMCs with excellent non-porous microstructure, fine grain size, and a strong bonding interface between reinforcement and Al matrix. Therefore, the interfacial reaction is effectively controlled and the structural integrity is maintained, resulting in enhanced strength and ductility. Based on the advantages of particulate reinforced AMCs and the SPS technique, the particulate reinforced AMCs fabricated by SPS have been extensively studied in recent decades, but have not been systematically evaluated. Therefore, this paper reviews the state-of-the-art particulate reinforced AMCs fabricated by SPS, focusing on the microstructure characterization, strengthening mechanisms, and mechanical and physical properties. Furthermore, the future research priorities and challenges of the high-performance particulate reinforced AMCs fabricated by SPS are also prospected. [ABSTRACT FROM AUTHOR]

In this paper, the contact heating technology was combined with the warm and hot stamping process of high-strength aluminum alloy, and the corresponding experimental device was developed. For the contact heating-warm stamping process, it's found that as the heating temperature increases, the mechanical properties of the parts first decrease and then increase, while the springback decreases. Meanwhile, for the contact heating-hot stamping process, it's found that the aluminum alloy sheets experience large plastic deformation during contact heating, resulting in the refinement of microstructure and the increase in dislocation density, and the performance of the formed parts is improved. [ABSTRACT FROM AUTHOR]

Laser cladding technology can obtain a cladding layer with good metallurgical bonding with the substrate and excellent performance. In situ growth of hard phase can effectively solve the problem of uneven distribution of reinforcements directly doped with hard particles. In this paper, 45# steel was adopted as the matrix material, WO3, B4C, Al, and Ni60 powder were used to prepare laser cladding and in situ synthesized WC (Tungsten Carbide) hard phase reinforced Ni‐based cladding layers. The effects of different laser cladding parameters, powder particle size, hard phase content on the microstructures and electrochemical properties of in situ synthesized WC hard phase reinforced Ni‐based cladding layer were analyzed. The results revealed that when the (WO3 + B4C + Al) mixed powder content was 25%, the bulk particles of WC phase in the cladding layer were most uniformly distributed in the cladding layer, which enhances the mechanical properties of the cladding layer. When the B4C particle size was 5 μm, the microhardness of the cladding layer was significantly higher than other cladding layers, and the enhancement mechanism of hardness by B4C is due to the Orowan strengthening caused by too small particle size of B4C. [ABSTRACT FROM AUTHOR]

Pearlite is a very important microstructure. Therefore, a model of the ferrite - cementite phase inter- face is constructed in this paper, and the process of nano - intrusion is simulated by molecular dynamics simulation method. By analyzing the mechanical properties and microstructure of the simulation results, the ferrite - ce- mentite phase interface effect was explored. It is found that the indenter load increases with the increase of the distance between the indenter and the grain boundary at different distances (positions of indentation) from the ferrite cementite grain boundary. When the indentation depth reaches a certain depth, the load decreases with the increasing distance. Young's modulus and maximum shear modulus are directly affected by the atomic structure below the indenter tip, and hardness is affected by both the structural integrity and type. The cementite phase interface affects the nucleation, proliferation and expansion of dislocations during the nano indentation process, and the macroscopic performance is the difference of the indenter load at different indentation positions under the same indentation depth. [ABSTRACT FROM AUTHOR]

This article discusses the use of Additive Manufacturing (AM) in automotive engineering, specifically focusing on the reliability of AM for advanced powertrain components. The study evaluates the mechanical behavior and microstructure features of samples made of AM 17-4PH steel, including engine exhausts, drive shafts, gearbox components, braking systems, and conrods. The researchers analyze the effects of sample geometry, size, and heat treatments on the properties of the samples. The study aims to provide insights for designing efficient prototypes using AM alloys and technology. The article also includes a list of references to other research papers and theses related to the fabrication and properties of stainless steel using AM techniques, providing valuable insights for researchers and engineers in the field. [Extracted from the article]

In this paper, the microstructure, mechanical properties, and corrosion behavior of friction stir welded (FSW) joints of the two aluminum alloys 6005A‐5083 were investigated and their correlation was discussed. In contrast to FSW joints of the same aluminum material, this results in a "V" shape curve of hardness distributed nonsymmetrically along the weld. The lowest hardness area occurs at the interface between the heat‐affected zone and the thermo‐mechanically affected zone of 6005A (6‐HAZ and 6‐TMAZ) due to the transformation of the β" phase under the influence of heat input during the stir friction process. This also leads to all tensile specimens fracturing in this area. The corrosion behavior of the FSW joint in acidic solution containing Cl− was determined by an exfoliation corrosion (EXCO) test, an intergranular corrosion (IGC) test, and potentiodynamic polarization measurements, based on the potential application in acid rain environment. The results showed that the corrosion resistance order in the acidic solution is: 6‐HAZ > NZ > 6‐BM > 5‐HAZ > 5‐BM. The 5‐BM has the worst corrosion resistance due to the high corrosion sensitivity of Al3Mg2 in acidic solution. However, good corrosion resistances are shown in NZ and 6‐HAZ, which is related to a relatively homogeneous microstructure in NZ and a dissolution or coarsening of β" phases in 6‐HAZ because of frictional heat input. [ABSTRACT FROM AUTHOR]

Skew rolling is a manufacturing process in which two or three rolls are used to reduce the diameter or modify the shape of a cylindrical workpiece, which is used to manufacture mechanical components such as shafts, rods or balls. Hot conditions are used to overcome limitations related to material ductility, residual stress and machine capacity. In this paper, the warm skew rolling (WSR) process of 42CrMo4 rods is modeled by the finite element method. The effects of forming parameters, namely initial temperature and roll rotational velocity, on the material strain rate, thermal properties, microstructure and hardness were analyzed. Simulation results were validated by experimental process data, while hardness tests and SEM-EBSD microscopy were used to assess mechanical properties and microstructure, respectively. The WSR resulting microstructure is different from the normalized ferritic–pearlitic initial one. The degree of spheroidization (DoS) of cementite increases with temperature. The maximum DoS of 86.5% occurs at the initial temperature of 750 °C, leading to the highest material softening. Rolling from lower temperatures favors grain fragmentation and the achievement of incomplete spheroidization, which, in combination with the highest proportion of high-angle boundaries, contributes to a higher hardness of the rods with respect to those rolled at higher temperatures. The highest reduction in hardness takes place at 750 °C and 30 rpm, leading to 209.4 HV1 (30.7% reduction) and 194.1 HV1 (35.7% reduction) in the near-surface and internal regions, respectively. The driving factor is the transformation of cementite precipitates into a spheroidal form characterized by the greatest degree of dispersion. [ABSTRACT FROM AUTHOR]

TiCp/steel composites are conventionally produced via powder metallurgy. In this paper, a liquid pressure infiltration method was developed to prepare a kind of spherical hierarchical architectured composite, in which spherical TiCp-rich hard phase regions were uniformly dispersed in TiCp-free soft phase region. The microstructure and mechanical properties of the architectured composites were carefully studied and compared with the common composite, as well as the effect of TiCp fraction on the properties. The results show that architecturual design can effectively improve both the toughness and strength of the composites. With TiCp content increasing from 30% to 50%, both the bending strength and the impact toughness of the architectured composites first increase, then decrease, and reach the highest at 40% TiCp. The highest impact toughness reaches 21.2 J/cm2, being 6.2 times that of the common composite and the highest strength being 67% higher. The pressure infiltration method possesses adaptability to varying shapes and sizes of the products, allowing for large-scale preparation. Therefore, for the first time, the combination of pressure infiltration preparation and architectural design was applied to TiCp/steel composites. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effect of hot deformation on commercially available Ti-6246 alloy below its β-transus transition temperature at 900 °C, knowing that the α → β transition temperature of Ti-6246 alloy is about 935 °C. The study systematically applies a thermomechanical processing cycle, including hot rolling at 900 °C and solution and ageing treatments at various temperatures, to investigate microstructural and mechanical alterations. The solution treatments are performed at temperatures of 800 °C, 900 °C and 1000 °C, i.e., below and above the β-transus transition temperature, for 9 min, followed by oil quenching. The ageing treatment is performed at 600 °C for 6 h, followed by air quenching. Employing various techniques, such as X-ray diffraction, scanning electron microscopy, optical microscopy, tensile strength and microhardness testing, the research identifies crucial changes in the alloy's constituent phases and morphology during thermomechanical processing. In solution treatment conditions, it was found that at temperatures of 800 °C and 900 °C, the α′-Ti martensite phase was generated in the primary α-Ti phase according to Burger's relation, but the recrystallization process was preferred at a temperature of 900 °C, while at a temperature of 1000 °C, the α″-Ti martensite phase was generated in the primary β-Ti phase according to Burger's relation. The ageing treatment conditions cause the α′-Ti/α″-Ti martensite phases to revert to their α-Ti/β-Ti primary phases. The mechanical properties, in terms of strength and ductility, underwent an important beneficial evolution when applying solution treatment, followed by ageing treatment, which provided an optimal mixture of strength and ductility. This paper provides engineers with the opportunity to understand the mechanical performance of Ti-6246 alloy under applied stresses and to improve its applications by designing highly efficient components, particularly military engine components, ultimately contributing to advances in technology and materials science. [ABSTRACT FROM AUTHOR]

Steel matrix composites are widely used in automotive, aerospace, wear, and cutting applications due to their superior mechanical properties, ease of manufacture, and low cost. However, there are still some limitations in the strength, reinforcement dispersion, and interface control of steel matrix composites, which are mainly achieved through different preparation processes and the addition of reinforced particles with mixed metal powders. Previous studies have demonstrated the enhanced ability of various reinforcing particles such as titanium carbide, silicon carbide, and alumina to enhance the wear performance of steel substrates, but there are still some challenges, such as uneven particle distribution, interface cracks, and unsatisfactory wettability. In this paper, the preparation methods of ceramic-reinforced metal matrix, ceramic reinforcement, steel matrix composition, microstructure, mechanical properties, and wear properties, as well as the parameters affecting their properties, are reviewed. The preparation processes of different ceramic-reinforced steel matrix composites are introduced, which are very suitable for overcoming challenges such as insufficient strength, poor dispersion, uneven distribution, and poor interfacial wettability. The influence of the morphology distribution and volume fraction of reinforcement on the wear rate of steel matrix composites was discussed. The importance of the microstructure of ceramic reinforcement in steel matrix and the interface between ceramic and matrix to improve the mechanical properties of steel matrix composites were emphasized. This review identifies the development trends in the field of research to fully illustrate the importance of more in-depth scientific research in steel matrix composites. [ABSTRACT FROM AUTHOR]

In this paper, a series of AlN–Al nanocomposite films are prepared by reactive magnetron sputtering. The effects of N 2 flow rate on the microstructure and mechanical properties of the films are studied. The formation and evolution mechanism of the nanocomposite structure are revealed. The results show that with the decrease of N 2 flow rate, the microstructure goes through three stages: pure AlN, amorphous Al surrounded nanocrystalline AlN and AlN nanoparticle reinforced Al matrix composite. Benefiting from the good wettability of Al on AlN ceramics, the film deposited at 6 sccm N 2 flow rate forms a nanocomposite structure of about 8 nm AlN grains wrapped by 1–2 nm amorphous Al. The hardness of the films increases first and then decreases with the decrease of N 2 flow rate, ranging from 4 GPa to 25 GPa. The toughness of the films is analyzed by the ratio of H/E, H3/E2, the normalized plastic depth (δ H) and the morphology of large load indentation. The results show that the toughness of the nanocomposite film obtained at 6 sccm N 2 flow rate is significantly improved while maintaining the hardness equivalent to that of pure AlN film. The improvement in toughness comes from the microcracks initiated in AlN hindered by the surrounding Al phase. [ABSTRACT FROM AUTHOR]

This literature review indicates that the basic microstructure of Ti6Al4V is bimodal, consisting of two phases, namely α + β, and it occurs after fabrication using conventional methods such as casting, plastic forming or machining processes. The fabrication of components via an additive manufacturing process significantly changes the microstructure and properties of Ti6Al4V. Due to the rapid heat exchange during heat treatment, the bimodal microstructure transforms into a lamellar microstructure, which consists of two phases: α′ + β. Despite the application of optimum printing parameters, 3D printed products exhibit typical surface defects and discontinuities, and in turn, surface finishing using shot peening is recommended. A literature review signalizes that shot peening and electropolishing processes positively impact the corrosion behavior, the mechanical properties and the condition of the surface layer of conventionally manufactured titanium alloy. On the other hand, there is a lack of studies combining shot peening and electropolishing in one hybrid process for additively manufactured titanium alloys, which could synthesize the benefits of both processes. Therefore, this review paper clarifies the effects of shot peening and electropolishing treatment on the properties of both additively and conventionally manufactured Ti6Al4V alloys and shows the effect process on the microstructure and properties of Ti6Al4V titanium alloy. [ABSTRACT FROM AUTHOR]

Calcium-magnesium-alumina-silicate (CMAS) resistance has become a key parameter to evaluate the properties of thermal barrier coating (TBC) materials. The CMAS corrosion behavior of BMT ceramic as a novel candidate material for TBC is poorly understood. In this paper, the solid-state sintering process was used to prepare the BMT bulks, and the evolution of microstructure, phase composition, thermophysical properties, and mechanical properties of the BMT bulks exposed to CMAS corrosion were studied. The results indicate that obvious elemental interdiffusion between the CMAS melt and BMT occurred at 1250 °C, which changed the original phase composition and formed multiple substances including Ba(Al, Ca)Si 2 O 8 , Ba 2 MgSi 2 O 7 , BaTa 2 O 6 , Ba 2 Si 4 O 10 , etc. The microstructure of BMT also underwent changes due to differences in the diffusion coefficients of different elements. As corrosion time prolongs, an obvious porous columnar reaction layer formed on the sample surface, causing the CMAS melt to sustainably corrode the deep BMT, resulting in intragranular corrosion. In terms of properties, the thermophysical and mechanical properties of the BMT bulks corroded by CMAS deteriorated. The thermal conductivity at 1100 °C increased from 1.43 W m−1 · k−1 to 1.67 W m−1 · k−1. The average coefficient of thermal expansion at 200–1400 °C decreased from 11.60 × 10−6 K−1 to 10.95 × 10−6 K−1. The hardness dropped by 21 % compared to the original BMT bulk. Therefore, it is necessary to improve the CMAS resistance of BMT ceramic in future studies. [ABSTRACT FROM AUTHOR]

Tailings from gold mines gradually approach ultra-fine, making mine backfill costs higher and strength lower, which poses a serious threat to the safety of underground personnel and equipment. It is well known that suitable chemical admixtures can enhance the working properties of mortar materials. Therefore, in order to achieve the purpose of reducing the cost of ultra-fine tailings backfill and improving the working performance of ultra-fine tailings filling slurry, this paper provides a study on the effect of sodium silicate and calcium chloride on the properties of ultra-fine tailings cemented backfill materials. The results of experimental studies through rheology, strength, and microstructural tests, etc., showed that the optimal proportioning parameters of cementitious materials are 76.92% blast furnace slag, 19.24% carbide slag, and admixtures of 2.88% sodium silicate and 0.96% calcium chloride. The 3, 7, and 28-day uniaxial compressive strength of the ultra-fine tailings cemented paste backfill with the newly formulated blast furnace slag-based cementitious material increased by 124%, 142%, and 14%, respectively, compared to that of the ultra-fine tailings cemented paste backfill with the P. O42.5 cement. The setting time for ultra-fine tailings cemented backfill slurry is shortened by the addition of admixtures, and the shear stress of the slurry is correlated with the amount of hydration product generation and its formation of flocculating structure. Moreover, the cost of the newly prepared cementitious material is much lower than that of traditional cement, which lays a good foundation for the cemented filling of ultra-fine tailings. [ABSTRACT FROM AUTHOR]

Calcium-magnesium-alumina-silicate (CMAS) resistance has become a key parameter to evaluate the properties of thermal barrier coating (TBC) materials. The CMAS corrosion behavior of BMT ceramic as a novel candidate material for TBC is poorly understood. In this paper, the solid-state sintering process was used to prepare the BMT bulks, and the evolution of microstructure, phase composition, thermophysical properties, and mechanical properties of the BMT bulks exposed to CMAS corrosion were studied. The results indicate that obvious elemental interdiffusion between the CMAS melt and BMT occurred at 1250 °C, which changed the original phase composition and formed multiple substances including Ba(Al, Ca)Si 2 O 8 , Ba 2 MgSi 2 O 7 , BaTa 2 O 6 , Ba 2 Si 4 O 10 , etc. The microstructure of BMT also underwent changes due to differences in the diffusion coefficients of different elements. As corrosion time prolongs, an obvious porous columnar reaction layer formed on the sample surface, causing the CMAS melt to sustainably corrode the deep BMT, resulting in intragranular corrosion. In terms of properties, the thermophysical and mechanical properties of the BMT bulks corroded by CMAS deteriorated. The thermal conductivity at 1100 °C increased from 1.43 W m−1 · k−1 to 1.67 W m−1 · k−1. The average coefficient of thermal expansion at 200–1400 °C decreased from 11.60 × 10−6 K−1 to 10.95 × 10−6 K−1. The hardness dropped by 21 % compared to the original BMT bulk. Therefore, it is necessary to improve the CMAS resistance of BMT ceramic in future studies. [ABSTRACT FROM AUTHOR]

With the rapid development of industrial manufacturing, traditional WC–Co cemented carbides have exposed more and more problems. Therefore, the preparation of ultrafine/nanocrystalline-grained cemented carbides and the development of new binders have become a hot issue in the field of cemented carbides. Due to the unique design concept, the high-entropy alloys (HEA) binder not only has the unique properties of the HEA itself, but also can replace the traditional Co element as the binder of cemented carbide, which opens up the possibility for industrial manufacturing. The stable chemical properties of WC are coupled with the multi-principal element characteristics of HEA binder, which makes novel WC-HEA cemented carbides have the characteristics of grain refinement, compact structure, stable structure, and excellent capability. A multitude of studies have found that the new WC-HEA cemented carbide exhibits better service performance than WC–Co cemented carbide. In this paper, the main preparation processes of WC-HEA cemented carbide in recent years are summarized; the influence of the working principle, advantages, and defects of the two different preparation methods on the microstructure and properties of WC-HEA cemented carbide were described. The characteristics and influence mechanism of microstructure such as the composition of high-entropy alloy binder and the change behavior of phase structure of WC-HEA cemented carbide were discussed. The service performance characteristics of WC-HEA cemented carbides were discussed, including mechanical properties, wear resistance, oxidation resistance, and corrosion resistance. Finally, it summarizes the research challenges and prospects in the current research work, and provides an outlook on the research direction and application prospects of WC-HEA cemented carbide. [ABSTRACT FROM AUTHOR]

Magnesium alloys play an essential role in metallic lightweight construction for modern mobility applications due to their low density, excellent specific strength, and very good castability. For some years now, degradable implants have also been made from magnesium alloys, which, thanks to this special functionality, save patients a second surgery for explantation. New additive manufacturing processes, which are divided into powder-based and wire-based processes depending on the feedstock used, can be utilized for these applications. Therefore, magnesium alloys should also be used here, but this is hardly ever implemented, and few literature reports exist on this subject. This is attributable to the high affinity of magnesium to oxygen, which makes the use of powders difficult. Therefore, magnesium wires are likely to be used. In this paper, a magnesium-based nanocomposite wire is made from an AM60 (Mg-6Al-0.4Mn) (reinforced with 1 wt% AlN nanoparticles and containing calcium to reduce flammability), using a high-shear process and then extruded into wires. These wires are then used as feedstock to build up samples by wire-arc directed energy deposition, and their mechanical properties and microstructure are examined. Our results show that although the ductility is reduced by adding calcium and nanoparticles, the yield strength in the welding direction and perpendicular to it is increased to 131 MPa. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 (ATZ) ceramics are attracting high interest in biomedical applications because of their desirable mechanical performance and biocompatibility. However, strength and toughness are mutually exclusive in structural ceramics. In this paper, based on digital light processing, novel textured ATZ ceramics with obvious crystallographic orientations were fabricated by incorporating Al 2 O 3 platelets with a high aspect ratio and equiaxed particles into the ZrO 2 matrix. The optimized fracture toughness of 16.9 ± 0.8 MPa m1/2 was achieved in the textured ATZ ceramic, which was about 67.3 % higher than non-textured ZrO 2 ceramics, without sacrificing strength. The coupling toughening effects of macrolayer structure, equiaxed and platelet-shaped Al 2 O 3 particles, and ZrO 2 particles were responsible for the enhanced mechanical performance. The macroscale toughening of 3D-printed lamellar architecture led to effective energy dissipation. Additionally, the crack deflection and crack branching induced by dual-morphology Al 2 O 3 particles, accompanied by the phase transformation of the ZrO 2 matrix, were significant microscopic toughening mechanisms. [ABSTRACT FROM AUTHOR]

Al2O3-forming austenitic steel (AFA steel) is an important candidate material for advanced reactor core components due to its excellent corrosion resistance and high temperature strength. Al is a strong ferrite-forming element. Therefore, it is necessary to increase the Ni content to stabilize austenite. Ni is expensive and highly active, and so increasing the Ni content not only increases the costs but also damages the radiation resistance. Mn is a low-cost austenitic stable element. Its substitution for Ni will not only help to improve the irradiation resistance of austenitic steel, but also reduce the cost. In order to explore the feasibility of Mn-substituted Ni-stabilized austenite in AFA steel, this paper summarized the research progress of Mn-added AFA steels, whilst the research status of traditional Mn-added austenitic steels are also referred to and compared herein. The effect of the addition of Mn on the microstructure and properties of AFA steel was analyzed. The results show that Mn can promote the precipitation of the M23C6 phase and inhibit the precipitation of the B2-NiAl phase and secondary NbC phase. With the increase in Mn content, the strength of AFA steel at room temperature and high temperature decreased slightly, the room temperature elongation increased slightly, while the high temperature elongation and creep resistance decreased obviously. In addition, for austenitic steel free of Al, the addition of Mn will destroy the oxide layer of Cr2O3, which will decrease the oxidation resistance of the steel. But the preliminary study shows that Mn has little effect on the Al2O3 oxide layer. It is worth studying the effect of Mn-substituted Ni on the oxidation resistance of AFA steel. In summary, more efforts are necessary to investigate the optimal Mn content to balance the advantages and disadvantages of introducing Mn instead of Ni. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 (ATZ) ceramics are attracting high interest in biomedical applications because of their desirable mechanical performance and biocompatibility. However, strength and toughness are mutually exclusive in structural ceramics. In this paper, based on digital light processing, novel textured ATZ ceramics with obvious crystallographic orientations were fabricated by incorporating Al 2 O 3 platelets with a high aspect ratio and equiaxed particles into the ZrO 2 matrix. The optimized fracture toughness of 16.9 ± 0.8 MPa m1/2 was achieved in the textured ATZ ceramic, which was about 67.3 % higher than non-textured ZrO 2 ceramics, without sacrificing strength. The coupling toughening effects of macrolayer structure, equiaxed and platelet-shaped Al 2 O 3 particles, and ZrO 2 particles were responsible for the enhanced mechanical performance. The macroscale toughening of 3D-printed lamellar architecture led to effective energy dissipation. Additionally, the crack deflection and crack branching induced by dual-morphology Al 2 O 3 particles, accompanied by the phase transformation of the ZrO 2 matrix, were significant microscopic toughening mechanisms. [ABSTRACT FROM AUTHOR]

The outbreak of the COVID-19 epidemic has led to a large number of waste disposable medical face masks (DMFMs) worldwide, which seriously pollute the environment and threaten human health. In this paper, waste DMFMs were recycled as mask fiber and mixed into self-compacting recycled aggregates concrete (SCRAC) to form a mask fiber reinforced self-compacting recycled aggregates concrete (FRSCRAC). The effects of recycled coarse aggregate (RCA) replacement ratio, DMFM fiber content, and length on the working and mechanical properties of FRSCRAC were investigated. The results show that the specimens meet the requirements of self-compacting concrete (SCC) in terms of working and mechanical performance, but the RCA and DMFM fiber could reduce the workability of the FRSCRAC, and the higher the amount of RCA and DMFM fiber, the more obvious the reduction. At the same time, the mechanical properties of FRSCRAC increased as the decreasing RCA replacement ratio and growing DMFM fiber content. Compared with specimens without DMFM fiber reinforcement, the compressive strength, split tensile strength, flexural strength, and elastic modulus were increased by 1.3%-9.6%, 1.46%-8.6%, 24.4%-54.69%, and 0.65%-4.73%, respectively. Moreover, the reduction of the DMFM fiber length is favorable to the mechanical properties of FRSCRAC as well. Furthermore, the X-ray CT and scanning electron microscope (SEM-EDS) techniques were applied to analyze the microstructure of typical specimens. The results showed that the DMFM fiber and surrounding mortar could form a multiphase composite, which reduces the porosity and improves interfacial stress transfer efficiency, thus enhancing the mechanical properties of FRSCRAC. In addition, based on the experimental results, the mechanical strength index of FRSCRAC and the calculation formula of its mutual conversion relationship were proposed. The research conclusions of this paper can provide a reference for the application of waste DMFM fibers in FRSCRAC. • Waste disposable medical face masks were recycled as fiber and mixed into self-compacting recycled aggregate concrete. • Parameters were investigated to make clear the influential mechanisms of waste fiber on recycled concrete performance. • The mechanical strength index of FRSCRAC and the calculation formula of its mutual conversion relationship were proposed. [ABSTRACT FROM AUTHOR]

Mechanical vibration was utilized to enhance the mechanical properties of the WAAM 2319 aluminum alloy and address issues related to coarse grains and porosity in this paper. The research aims to investigate the impact of varying vibration accelerations on the microstructure and mechanical properties of the specimens. The mechanism of solutes transfer caused by vibration has been described in this paper, which significantly improved elongation. The dendrites during growth were broken by vibration, which led to microstructure refinement. The solutes located in the interstices of the dendrites were transferred to the liquid phase by vibration, reducing the concentration of solutes in the interstices of the dendrites. The continuous coarse precipitation phase becomes intermittent and fine; resulting in increased matrix plasticity. With the increase of vibration acceleration, the elongation was significantly enhanced. The longitudinal elongation was enhanced more significantly because of the alternating distribution of INZ and ITZ, with longitudinal elongation showing a 29.3% increase and transverse elongation a 52.5% increase, while the UTS and YS was not changed significantly in the presence of multiple factors. • Mechanical vibration increases the elongation without affecting the UTS and YS. • Mechanical vibration applies reciprocating force to the dendrite, causing the fracture of the dendrite and the refinement of the grain. • Mechanical vibration induces solutes located in the dendrite interstices toliquid phase, reducing the solute concentration in the INZ. • Intermittent precipitation phases and fewer intragranular precipitation phasesin the INZ lead to increased elongation. [ABSTRACT FROM AUTHOR]

To further enhance our understanding of the microstructure of SRM and its intrinsic relationship with macroscopic properties, this paper conducted indoor freeze-thaw cycles, EIS and uniaxial compression tests. The results indicated that the number of freeze-thaw cycles has a significant exponential relationship with R CPP , R CPP 1 and C DSRP. As the number of cycles increased, R CPP and R CPP 1 exhibited a decreasing trend, whereas C DSRP showed an increasing pattern. The freeze-thaw cycles led to the expansion and connection of different pores, resulting in the widening or multiplication of channels in CPP , leading to a decrease in both R CPP and R CPP 1. However, in DSRPP , the liquid-filled pores underwent radial expansion during freeze-thaw cycles, connecting with gas-filled pores around them. This transition led the conductive path to transform into CPP , reducing the accumulated thickness of non-continuous points. Consequently, C DSRP exhibited an increasing trend. Furthermore, the increase in porosity weakened the deformation resistance, increasing the compaction stage of pores and the peak strain, while reducing its peak strength and secant modulus. The peak strength, strain and secant modulus also exhibited significant exponential relationships with different cycles. There was a good exponential correlation between ∆ R CPP of CPP and the uniaxial strength, and the freeze-thaw deterioration model constructed with it as an influence factor could better assess its peak mechanical strength after freezing and thawing. • An electrochemical circuit model for different conductive paths was proposed. • The microstructure was characterized by EIS parameters of the equivalent model. • The influence and mechanism of freeze-thaw cycles on EIS parameters were analyzed. • A degradation model for the uniaxial strength was established with EIS parameters. [ABSTRACT FROM AUTHOR]

This paper presents new technology for stainless steel wire processing. This technology consists of using cryogenic cooling immediately after the wire leaves the drawing die. Results of a laboratory experiment show that use of cryogenic processing after wire drawing improves mechanical properties compared with traditional drawing. Metallographic analysis proves that deformation conditions during cryogenic drawing are an additional factor for realization of structural resources to optimize steel wire physical and mechanical properties. [ABSTRACT FROM AUTHOR]

In this paper, the effects of Mn element and rare earth element Gd on the microstructure, thermal stability, mechanical properties and shape memory effect of polycrystalline Cu-12.0Al-4.0Ni and Cu-12.0Al-4.0Ni-1.5Mn- x Gd high-temperature shape memory alloy were investigated. The results show that the Cu-12.0Al-4.0Ni alloy exhibits millimeter-sized grain, dual-phase structure with coexistence of 18R and 2H martensite and poor thermal stability. When the Mn and Gd element was added to Cu-12.0Al-4.0Ni alloys, the grain size can be refined by an order of magnitude, and the 2H martensite disappeared completely, accompanied by the formation of the AlCu 4 Gd phase, meanwhile, thermal stability is significantly improved. The grain refinement improves the mechanical properties and shape memory effect of Cu-12.0Al-4.0Ni-1.5Mn- x Gd alloys. When x = 0.3, the compressive fracture stress, compressive fracture strain and recoverable strain can reach 969 MPa, 15 % and 8 %, respectively. • Cu–Al–Ni-based shape memory alloy achieved exceptional thermal stability. • Fully recoverable strain of the alloy reached 8 %. • The stress shielding effect is responsible for the ductility deterioration. [ABSTRACT FROM AUTHOR]

• Electromagnetic pulse welding joins 1060 Al and SiCp/2A14 with pre-treatment. • No IMCs are formed at the interface, and the maximum tensile-shear force of the joint reached 2.75 kN. • SiC-rich was unfavorable for the metallurgical bonding of 1060 Al and SiCp/2A14. Electromagnetic pulse welding (EMPW) technology has received wide attention in welding the same and dissimilar metal materials. In this paper, the connection of Al 1060 and SiCp/2A14 (2A14/SiC/15p) dissimilar materials was realized by EMPW technology at three discharge energies of 21 kJ, 24 kJ and 27 kJ, and the interface microstructure characterization and tensile-shear performance experiments were carried out to evaluate the joint performance. The results show that the interface morphology of Al 1060-SiCp/2A14 dissimilar materials by EMPW presents a typical wave shape, the wave amplitude is positively correlated with the discharge energy, and the maximum value is 9 μm (27 kJ). The tensile-shear performance of the welded joint is better than that of the base material, and the maximum tensile-shear force is 2.75kN (27 kJ). The fracture failure mode changes from interface failure (21 kJ and 24 kJ) to base material failure (27 kJ). There are no IMCs (Intermetallic Compounds) at the interface, and the high shear strength of the joint is due to the combined action of mechanical interlocking and atomic diffusion. [ABSTRACT FROM AUTHOR]

The low water-cement ratio has a significant effect on increasing the compacted density of the concrete, thereby enhancing its mechanical properties and microstructures. This paper introduces an innovative approach of utilizing the cold isostatic pressing method to prepare reactive powder concrete (RPC) specimens with an ultra-low water-cement ratio which not exceeds 0.16. And it is compared with the specimens prepared by the traditional vibrational method which conversely requires the minimum water-cement ratio of 0.21. The results show that the RPC specimens under cold isostatic pressing exhibit enhanced compressive strength and microhardness, as well as improved matrix compactness. Conversely, the RPC matrix produced under the vibrational method not only contains a small number of air-entrained bubbles that can influence the strength of matrix but also exhibits a significantly larger cumulative volume of harmful pores that affect the performance of RPC compared to cold isostatic pressing. Therefore, cold isostatic pressing technology based on all-directional hydroforming is a powerful tool for the preparation of high-strength RPC, which significantly reduces the internal defects of the specimen, and the prepared RPC has superior mechanical properties and matrix structure. • Significant increase in the compressive strength of RPC has been achieved by cold isostatic pressing. • The molding method has a significant influence on the Vickers hardness of RPC. • The hydration reaction of cold isostatic pressing specimens after autoclave curing is still incomplete. • Specimens prepared by cold isostatic pressing exhibit dense matrix without air-entrained bubble observed. [ABSTRACT FROM AUTHOR]

The paper comparatively investigates the microstructure, mechanical, and damping properties of hypoeutectic Al–Si–Cu casting alloys prepared by the cooling slope casting and thixoforming process. Microstructural analysis shows that cooling slope process refined the grains and promoted the transformation of equiaxed dendritic α-Al to rosette morphology. Subsequent thixoforming further enhanced this refinement, generating a microstructure of α-Al globules and spheroidized eutectic silicon particles. These microstructural alterations significantly improved their mechanical properties. Notably, the thixoformed samples exhibited a remarkable increase in yield strength from 139 to 193 MPa (38%), ultimate tensile strength from 145 to 205 MPa (42%), and fracture elongation from 1.1 to 3.2%. The damping analysis revealed a significant increase in both the loss modulus and damping capacity, while the storage modulus decreased at high temperatures for all samples. Consequently, the thixoformed samples displayed a distinct improvement in both their mechanical characteristics and damping capability. [ABSTRACT FROM AUTHOR]

In this paper the influence introducing various plasticizers into an initial charge on the structure and properties of iron-based powder materials alloyed with copper is considered. It is shown that introduction of copper stearate into an initial powder mixture and warm mixing, pressing and subsequent sintering makes it possible to obtain low-porosity workpieces with relative porosity of 95%. Pores within the workpieces obtained have a small size of 10–15 microns and a rounded shape. Also, bending strength is determined for sintered samples of all the compositions of powder mixtures studied and the Rockwell hardness is determined on the C scale. Powder steels based upon mixtures have the best set of mechanical propertiesPZhRV 2.200.28 + 0.7 wt.% Br + 0.7 wt.% Cu + 1 wt. % StCu + warm mixing—hardness HRC 58. flexural strength 600 MPaPZhRV 2.200.28 + 1.4 wt.% Br + 1.4 wt.% Cu + 1.4 wt.% C + 1.0 wt.% StFe + warm mixing—hardness HRC 100, flexural strength 530 MPaPZhRV 2.200.28 + 0.7 wt.% Br + 0.7 wt.% Cu + 1 wt. % StCu + warm mixing—hardness HRC 58. flexural strength 600 MPaPZhRV 2.200.28 + 1.4 wt.% Br + 1.4 wt.% Cu + 1.4 wt.% C + 1.0 wt.% StFe + warm mixing—hardness HRC 100, flexural strength 530 MPa [ABSTRACT FROM AUTHOR]

This paper aims to investigate the microstructure and mechanical properties of S31603 + Q355B stainless-clad (SC) bimetallic steel welded connections with different welding configurations. A comprehensive research approach was employed, including microstructure analysis, static tensile test, impact test, bending test, Vickers hardness distribution measurement, and analysis of welding economy and efficiency. Four types of welded connections were examined to understand their performance variations arising from different welding configurations. Based on the findings, a recommended welding configuration suitable for structural engineering applications was proposed. Research outcomes showed that the decarburization and carbon accumulation zones were observed at the fusion interface during the welding of dissimilar metals. It should be noted that martensite was formed in the substrate, or the base metal, due to diffusion of alloying elements, with a more pronounced effect observed with higher welding heat inputs. In order to minimize the fusion area of dissimilar metals, it is advisable to avoid using a single welding consumable made of stainless steel as the mechanical properties of the welded connection were not significantly influenced by the use of stainless steel welding consumables with higher Nickle (Ni) and Chromium (Cr) alloying content in the transition region. Consequently, the same welding consumable should be employed in the transition region to simplify the welding procedure and to enhance the welding efficiency. • Micro-macro tests on stainless-clad bimetallic steel welded connections were done. • Effects of various welding configurations were clarified. • The unique behaviour of transition weld zones were described. • The advantages and disadvantages of each welding configuration were discussed. • The recommended welding configuration was proposed. [ABSTRACT FROM AUTHOR]

Achieving the stringent demands of sustainable tribological industrial applications poses a significant challenge, particular in optimizing the self-lubricant performance of nitride-based films. This paper tackled this challenge by designing and depositing a series of ZrN-MoSN composite films with varying (Mo + S)/Zr ratios, employing RF magnetron sputtering, aimed to enhance the tribological properties through utilizing the high loading capacity of the ZrN matrix and the exceptional self-lubricating attributes of Mo-S-N additives. After conducting thorough investigations on the microstructure, and tribological properties, the results revealed that the dense columnar structured ZrN-MoSN composite films displayed a polycrystalline composition comprising fcc-ZrN and hcp-MoS 2 phases, intertwined with amorphous phases of Mo(SN) x and MoS 2 (N 2). (Mo + S)/Zr ratios below 1.08 exhibited a minor impact on the room temperature (RT) tribological properties, while higher ratios led to degradation on RT average friction coefficient (COF) and wear rate (WR). However, the synergistic effect of ZrN matrix and the tribo-phases of layered MoO 3 and hard ZrO 2 contributed to the significant enhanced 500 °C tribological properties, particularly with an optimized (Mo + S)/Zr ratio of 0.43. [Display omitted] • ZrN-MoSN composite films were fabricated by the magnetron co-sputtering technique. • The films exhibited a coexistence of fcc-ZrN, hcp-MoS 2 , Mo(SN) x and MoS 2 (N 2) phases. • Incorporating Mo-S-N in ZrN notably bolstered the 500 °C tribological properties. [ABSTRACT FROM AUTHOR]

In this paper, the aluminum foam sandwich (AFS) was obtained from foamable precursor sandwich (FPS) through a foaming process, in which the preparation of FPS was achieved by compound casting with hot rolling. The effects of rolling and foaming on the interface microstructures and mechanical properties were investigated. Furthermore, the interface bonding mechanisms and strengthening mechanisms were revealed. For FPSs, increasing the rolling pass increased the interface thermodynamic energy, which was beneficial to the achievement of a more effectively bonded interface. Meanwhile, the grains were refined, the fraction of low angle grain boundaries (f LGABs) and average geometrically necessary dislocation density ( ρ ¯ GND) at the interface increased, which collectively contributed to the enhancement of interface bonding strength and ductility. In the foaming process, although the interface thermodynamic energy led to a reduction in the original interface defects and an enhancement in elements diffusion at the pre-existing well-bonded interface, AFSs displayed lower interface bonding strength and ductility compared to their corresponding FPSs due to coarse grains, decreased f LGABs and ρ ¯ GND. Moreover, an analysis of interface strengthening mechanisms revealed that the increase of rolling pass for FPS resulted in an improvement in the interface bonding strength and ductility of the corresponding AFS. [ABSTRACT FROM AUTHOR]

• SLM-fabricated 430 FSS exhibits significant anisotropy. • SLM-fabricated 430 FSS contains second-phase oxides and high dislocations. • SLM-fabricated 430 FSS exhibits excellent strength with limited plasticity. • SLM-fabricated 430 FSS shows cleavage fractures. This study investigates the microstructure and mechanical properties of 430 ferritic stainless steel (FSS) fabricated via the selective laser melting (SLM) process. The mechanical properties and fracture morphologies of SLM-fabricated 430 FSS and conventional 430 FSS were compared in this paper. It was found that 430 FSS produced by SLM exhibits significant microstructural anisotropy, with higher dislocation density and the presence of oxides of silicon, manganese and aluminum. Regarding mechanical properties, 430 FSS fabricated via SLM process displays higher tensile strength and yield strength, as well as superior product of strength and elongation (PSE) and yield ratio, compared to those produced by conventional methods. Fracture morphology analysis revealed that SLM-fabricated 430 FSS primarily exhibited characteristics of cleavage fractures, whereas conventional 430 FSS showed typical features of ductile fractures. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel idea of controlling microstructure and mechanical properties based on the non-equilibrium microstructure of nickel-based superalloy fabricated by laser powder bed fusion (LPBF). The network microstructures were firstly built in LPBF nickel-based superalloys by direct aging (DA) heat treatment. Thermodynamic calculations were conducted to design the DA and homogenizing + DA (HDA) heat treatments for elucidating the control mechanism. The results showed that the non-equilibrium microstructures in as-built nickel-based superalloy contributed to the network microstructure formation and recrystallization during DA heat treatment. The grains were refined and the <001> texture was eliminated after DA heat treatment. The non-equilibrium microstructures were removed and the recrystallized grains tended to coarsen after HDA heat treatment due to high temperature homogenizing treatment. The in-situ nano γ′ phase uniformly distributed in the grains of HAD-treated microstructures, which was also found inside network microstructures of DA-treated microstructures. Due to the additional strengthening effect of refined grains and network microstructures, the strength of DA-treated sample was higher than those of as-built and HAD-treated samples, while the ductility was lower than that of as-built sample, and but was close to that of HAD-treated sample. This study will provide guidance for developing a suitable heat treatment process of LPBF nickel-based superalloys. [ABSTRACT FROM AUTHOR]

• The densification behavior in different hatch distances was investigated. • The microstructure evolution was characterized and analyzed. • The strengthening mechanism was explored. • The relationship between microstructure and mechanical properties was established. Laser powder bed fusion (LPBF) of duplex stainless steel is a promising route to fabricate intricate parts with excellent mechanical properties. However, further understanding of build mechanisms is required to improve the process. This paper aims to better understand the influence of hatch distance on the densification behavior and figure out the correlation with microstructure and mechanical properties in LPBF of 2205 stainless steel. With the optimized laser power and scanning speed, the significant influence of hatch distance on the build quality is revealed. A hatch distance of 0.07 mm is selected for an even surface and dense part with a relative density of up to 99.13 %. The hatch distance has a crucial impact on the heat and mass transfer between tracks; hence, poor surface morphologies such as inter-track voids or swelling surfaces occur if an improper hatch distance is adopted. The optimal mechanical properties are also achieved. Specifically, the yield strength (0.2 YS), ultimate tensile strength (UTS), and elongation (EL) values are 896.8 MPa, 1035.13 MPa, and 15.34 %, respectively. The improvement in mechanical properties can be ascribed to the coordination between high dislocation density, fine grain size, high CSL boundaries and LAGBs, and high relative density with few pores. This work can help improve the build quality and expand the application horizon of duplex stainless steel for manufacturing intricate components. [ABSTRACT FROM AUTHOR]

To achieve superior damage tolerance and fatigue properties, it is desirable for the microstructure of Ti-6Al-4V ELI (Extra Low Interstitial) titanium alloy to consist of equiaxed grains with a homogeneous lamellar structure. However, traditional forging and single additive manufacturing techniques require extreme processes such as quasi β heat treatment and hot isostatic pressing. In this paper, a hybrid directed energy deposition method that integrates in-situ rolling with simple annealing is proposed to simultaneously achieve these microstructures. The results indicate that the initial microstructures produced by hybrid directed energy deposition consist of fine equiaxed prior-β grains, inconspicuous interpass bright bands, randomly oriented lamellar structure and numerous small substructures at the TEM scale. Due to the plastic deformation caused by in-situ rolling, the primary β grains underwent significant refinement with a reduction in grain diameter from over 2000 μm to 113.8 μm. Besides, the unique microstructures and thickness of α laths are influenced by coarsening and dissolution mechanisms that are controlled by diffusion during phase transformation. Furthermore, a uniform microstructure without bright bands and excellent comprehensive properties can be achieved through heating at 880 °C for 2 h and natural cooling. These findings validate that hybrid directed energy deposition coupled with simple annealing present a novel and cost-effective approach for the direct manufacturing of uniform titanium alloy forgings. • Microstructure evolution in DED with in-situ rolling and annealing was studied in detail. • Uniform microstructure realized with fine equiaxed grains. • Driving forces and mechanisms of α lamellae evolution were summarized. • Optimal comprehensive properties were analyzed. [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]

High-manganese steels, due to their unique combination of strength and elongation, have been widely used in aerospace, petrochemical and rail transportation. However, a prevalent challenge in advancing the utilization of high-manganese steel is the need for corresponding welding consumables. The deformation mechanism of high-manganese steel encompasses three primary mechanisms: martensitic phase transformation, twinning and dislocation movement. The stacking fault energy (SFE) is a critical factor in determining the dominant deformation mechanism in high-manganese austenitic steels. Furthermore, the magnitude of the SFE is principally influenced by the alloying elements present and the temperature at which deformation occurs. Alloying elements can significantly influence the microstructure and mechanical properties of wire arc additive manufacturing (WAAM) of high-manganese steels. The metal powder-cored wire of high-manganese steel with full austenitic microstructure was designed in this paper. The effects of C, Mn and Cu on the microstructure, solute segregation and properties of WAAM of high-manganese steels were systematically investigated by optical microscopy, electron microscopy and mechanical testing. The influence of SFE on the microstructure characteristics and work hardening behaviour were also studied. The results showed that as an increase of the C content, the tensile strength and elongation of deposited metals were improved. The corresponding low-temperature impact toughness increased at first and then decreased. The highest value of impact toughness was 68.5 J with 0.79%C. As the Mn increased, the strength decreased, the elongation increased and the low-temperature impact toughness value displayed an initial increase followed by a subsequent decrease. With the increase of Cu, the yield strength and elongation improved significantly. The tensile strength exhibited a marginal initial increase followed by a decrease, whereas the change was not substantial. In contrast, the low-temperature impact toughness value showed a substantial increase followed by a decrease. The developed M3 wire containing 1.10%C-21%Mn-0.3%Cu possessed the optimum performance (yield strength of 551 MPa, tensile strength of 909 MPa, elongation at break of 30.2%, impact toughness value of 57.5J), with the good mechanical stability and low solidification cracking sensitivity. [ABSTRACT FROM AUTHOR]

In this paper, the effect of Si content on the microstructure and mechanical properties of the Al–1.2Mg–xSi–1.2Cu–0.6Mn cast alloy was investigated. The study aimed to explore the optimal addition of Si element to improve the comprehensive properties of alloys. The microstructure, phase composition and fracture morphology of the alloy were determined through OM, SEM, EBSD and XRD analysis. The Si content in the alloy ranged from 0.48 to 2.4 wt.%. With the increase of Si content, the number of strengthening phases increases, which improves the comprehensive properties of the alloy. When the Si content is 0.8 wt.%, the eutectic Mg2Si transforms from rod-shaped to larger block shaped, and the formation of coarse Mg2Si phase limits the elongation of the alloy. When the Si content is 2.4 wt.%, fine Al2Cu phases are present in this alloy and coexist with Al(Fe,Mn)Si phases, while an increase in the Si content appears as partially accompanied by an incipient crystalline Si phase around the Al(Fe,Mn)Si phase. The alloy exhibits a maximum tensile strength, yield strength and elongation of 198.2 MPa, 101.2 MPa and 4.96%, respectively, with a hardness of 80.94 Hv. It consists of five alloy phases, mainly α-Al, Mg2Si, Al(Fe, Mn)Si eutectic phase, Q-AlCuMgSi eutectic phase and the beginning crystalline silicon phase formed due to the increased Si content. The Si content can improve alloy strength, but there is some damage to the toughness of the alloy. Higher silicon alloy content results in the formation of fine Al2Cu eutectic. This result makes it possible to achieve a higher level of strength with a reduced loss of ductility in the alloy. [ABSTRACT FROM AUTHOR]

Ultrafine cement is widely used in micro-fracture grouting due to its very small particle size, and the expansion agent can improve the dry shrinkage and cracking phenomenon of ultrafine cement grouting materials, and at the same time produce self-stress to enhance the sealing effect, but at present, there are fewer researches on the hydration synergistic effect of ultrafine cement and expansion agent. For this reason, this paper explored the effects of two commonly used expansion agents, U-type and MgO-type, on the mechanical properties, hydration heat, hydration products and microscopic morphology of ultrafine cement materials. The results demonstrated that the expansion performance of MgO-type expansion agent (MEA) was better than that of U-type expansion agent (UEA); At the same time, the MgO-type expansion agent delays the exothermic cement hydration and inhibits the transformation of hydration products, and the stress concentration generated by its delayed expansion effect leads to brittle damage of the material. UEA participates in cement hydration and produces swelling crystals, and at this time, the specimen was mainly cemented in the form of particles, and the pre-generated internal expansion stress densifies the pore structure of ultrafine cement, which enhanced the mechanical strength of the specimen. • The effects of MgO and U-type expansion agent on the expansion and mechanical properties of superfine cement were analyzed. • The effects of U-type and MgO type expansion agent on the microstructure of ultrafine cement grouting materials were analyzed. • The relationship between hydration coordination and properties of superfine cement and expander was revealed. [ABSTRACT FROM AUTHOR]

This paper reports the development of TiCN - Co - Cr 3 C 2 - Si 3 N 4 cermets modified with the addition of B 4 C. Cermets of three different compositions with varying B 4 C in TiCN - Co - Cr 3 C 2 - Si 3 N 4 were fabricated. The TiCN, Co, Cr 3 C 2 , Si 3 N 4 and B 4 C powders in the combinations 80%TiCN-5%Co-5%Cr 3 C 2 –5%Si 3 N 4 –5%B 4 C; 75%TiCN-5%Co-5%Cr 3 C 2 –5%Si 3 N 4 –10%B 4 C; 70%TiCN-5%Co-5%Cr 3 C 2 –5%Si 3 N 4 –15%B 4 C were ground in a ball milling unit for six hours at a speed of 300 rpm at a ball-to-powder ratio of 10:1. The powders were then sintered in a vacuum hot press at a temperature of 1600 °C and a pressure of 50 MPa with soaking time of 90 min. For comparison purpose, 90%TiCN-5%Co-5%Cr 3 C 2 cermet was prepared. The microstructure of the sintered cermets revealed the core-rim structure. The Vickers hardness test was done with a load of 10 Kg and for duration of 10 s. Fracture toughness was measured using the crack length data obtained from the hardness test using scanning electron microscopy. The cermet with a composition 75% TiCN-5%Co-5% Cr 3 C 2 –5% Si 3 N 4 –10% B 4 C produced higher hardness of 26.53 ± 0.56 GPa and fracture toughness of 10.29 ± 0.18 MPa m and 70% TiCN-5%Co-5% Cr 3 C 2 –5% Si 3 N 4 –15% B 4 C showed high fracture toughness value of 11.23 ± 0.09 MPa m with hardness value of 21.05 ± 0.10 GPa. The cermet composition 75% TiCN-5%Co-5% Cr 3 C 2 –5% Si 3 N 4 –10% B 4 C retained the hardness of 16.85 GPa even after annealing at 600 °C. The sintered cermets tend to form TiO 2 which determines the hardness of the annealed cermets at a range of 600 °C – 1000 °C. The presence of these oxides tends to decrease the hardness. The wear test was performed taking the cermet as the pin material. The abrasive and adhesive wear mechanisms were dominant in the cermets. The harder precipitates formed tend to increase wear resistance by reducing the wear rate. The harder precipitates (TiN and TiB 2) formed mainly due to the addition of Si 3 N 4 and B 4 C, this addition promotes adhesive wear by a tribolayer formation. • Developed 75% TiCN-5%Co-5% Cr 3 C 2 –5% Si 3 N 4 –10% B 4 C cermet with hardness of 26.53 ± 0.56 GPa and K 1c of 10.29 ± 0.18 MPa m. • 75% TiCN-5%Co-5% Cr 3 C 2 –5% Si 3 N 4 –10% B 4 C retained the hardness of 14 GPa even after annealing at 1000 °C. • 75% TiCN-5%Co-5% Cr 3 C 2 –5% Si 3 N 4 –10% B 4 C cermet showed high wear resistance. [ABSTRACT FROM AUTHOR]