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Dynamic mechanical properties of the selected laser melting (SLM)-NiCrFeCoMo 0.2 high-entropy alloy (HEA) are further improved by controlling the molten pool structure and the generation of σ-phase precipitation particles. In this study, a split Hopkinson pressure bar (SHPB) was used for testing the dynamical mechanical properties of the quenched SLM-NiCrFeCoMo 0.2 HEA specimens. Microstructure and volume fraction of the σ precipitates were characterized by X-ray diffractometry (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and the small angle neutron scattering (SANS) technique. After heating to 800 ℃, holding for 8 h and water quenching, the molten pool boundary of the SLM-NiCrFeCoMo 0.2 HEA disappear, and the ultimate compressive strength and the impact energy of specimens reach 1970 MPa and of 217.45 MJ·m−3, respectively. Due to the segregation of Mo elements in the molten-pool boundary of the as-build SLM-NiCrFeCoMo 0.2 HEA, more σ precipitates tend to form at the residual molten pool boundary of the quenched SLM-NiCrFeCoMo 0.2 HEA. The σ precipitates play key role in strengthening of the SLM-NiCrFeCoMo 0.2 HEA. • Annealed SLM- NiCrFeCoMo 0.2 HEA has larger ultimate compressive strength and the impact energy. • Lots of σ precipitates generate at the residual molten pool boundary. • Small angle neutron scattering technique is used to analyze the volume fraction of σ precipitates. • The σ precipitates play key role in strengthening of the SLM-NiCrFeCoMo 0.2 HEA. [ABSTRACT FROM AUTHOR]

Abstract SiC ceramics are important high-temperature structural materials with excellent chemical and physical properties. However, the different impurities are usually introduced into the raw materials in the preparation of SiC powders, especially Fe 2 O 3 impurity. The current work aims to investigate the effect of Fe 2 O 3 contents (0–0.8 wt%) on the sintering behaviour and mechanical properties of SiC ceramics. Fe 2 O 3 -containing SiC ceramics were prepared by pressureless sintering using carbon and boron carbide as sintering additives. The X-ray diffraction, inductively coupled plasma-atomic emission spectrometry, scanning electron microscope, and mechanical testing were used to understand the effect of Fe 2 O 3 on a few key properties of sintered samples. The results indicated that the hardness (from 24.4 ± 1.0 GPa to 27.2 ± 1.3 GPa) and flexural strength (from 360 ± 38 MPa to 394 ± 18 MPa) can be increased by 10% upon a gentle introduction of only 0.02 wt% of Fe 2 O 3 , due to the formation of fine gains and homogenous microstructures. However, the further increase of Fe 2 O 3 contents above 0.4 wt% is found to be detrimental to sintering of SiC ceramics. It is suggested that excessive Fe 2 O 3 reacts with C leading to the formation of more volatile species (CO, Fe), and increasing the porosity of SiC matrix, which hampers the densification process and is harmful to mechanical properties of sintered SiC. Highlights • Hardness and flexural strength can be increased by 10% upon a gentle introduction of only 0.02 wt% of Fe 2 O 3. • The abnormal growth of grains can be controlled to some extent by adding Fe 2 O 3. • The content of Fe 2 O 3 should be controlled within 0.4 wt% in the preparation of SiC powders. [ABSTRACT FROM AUTHOR]

Abstract (Ti 1-x ,Zr x)(C 0.5 ,N 0.5)-Co cermets doped with various zirconium (x = 0, 0.05, 0.1, 0.15) were fabricated by in-situ carbothermal reduction-nitridation and liquid phase sintering-HIP treatment at 1500 °C. The microstructure, mechanical properties and oxidation resistance of (Ti 1-x ,Zr x)(C 0.5 ,N 0.5)-Co cermets were characterized by scanning electron microscope, X-ray diffraction, mechanical properties tests and high temperature oxidation experiment. The results showed that the existence of zirconium in cermets could refine the hard phase grain and improve the mechanical properties of cermets. The proper zirconium addition promoted the formation of a dense protective layer on the surface of cermets at the high temperature, which might reduce the diffusion rate of the oxygen atom and enhance the oxidation resistance of cermets. Highlights • The (Ti,Zr)(C,N)-Co cermets with the different Zr additions were fabricated. • The addition of extra Zr can inhibit the growth of hard phase particles in the sintering process. • The addition of extra Zr can enhance mechanical properties and oxidation resistance obviously. • The Zr-doped cermets hold great potential in machining and structural applications. [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]

A cost-effective iron-rich non-equiatomic Fe 50 Mn 20 Al 15 Ni 10 Co 5 medium entropy alloy (MEA) was synthesized by vacuum induction melting. The as-cast alloy exhibits a multiphase microstructure with the ordered B2 (a= 2.90 ± 0.01 Å), disordered body-centred cubic (BCC) (a= 2.89 ± 0.01 Å) and face-centred cubic (FCC) (a= 3.61 ± 0.02 Å) phases. X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to confirm the structure of the evolved phases. The columnar dendrites having a width in the range of 120–300 µm were observed in the as-cast structure. The formation of Ni-Al rich B2 precipitates in the BCC matrix was confirmed based on detailed microstructural characterization using scanning electron microscope (SEM) and TEM. The phase separation in the form of modulated structure of ordered B2 and disordered BCC phase was related to the spinodal decomposition. The formation of the FCC phase at and near the grain boundaries is linked to simultaneous nucleation and growth mechanisms, which occur during the solidification. The as-cast alloy has shown an average compressive yield strength of ∼1250 MPa and ultimate strength of ∼1675 MPa, along with a compressive strain of ∼42%. The optimum balance of strength and ductility is achieved due to the formation of the hard (B2, BCC) and soft (FCC) phases and their interplay during the deformation process. These encouraging results of the alloy in the as-cast state have provided the direction to design and develop such economically viable alloys, which could be produced at industrial scale. • A novel cost-effective Fe 50 Mn 20 Al 15 Ni 10 Co 5 MEA was synthesized by vacuum induction melting. • Alloys exhibits two phase structure of BCC and FCC in as-cast state. • The modulated structure of B2 and BCC was related to spinodal decomposition. • The optimum balance of strength and ductility is achieved in the alloy. [ABSTRACT FROM AUTHOR]

Abstract Current work reports on the development of A357 alloy composite which is reinforced with dual size SiC particles by stir casting route. Influence of different weight fractions (3% coarse+ 3% fine, 4% coarse + 2% fine, and 2% coarse + 4% fine) of dual size SiC particles on mechanical properties and wear resistance of A357 composites is the focus of this work. Hardness and tensile properties were studied for dual size composites and then were compared with A357 alloy. Microstructural study, fractured surface and worn surface investigation were carried out using optical and scanning electron microscopes respectively. Microstructural analysis showed fairly uniform dispersion of dual size SiC particles in A357 matrix with good interfacial bonding. Compared to A357 alloy, the composites showed improvement in hardness, yield, and tensile strength. In particular, composite with 4 wt. % of fine and 2 wt. % of large SiC particles displayed the highest tensile strength while composite with 4 wt. % of large and 2 wt. % of fine SiC particles exhibited high hardness and wear resistance among A357 alloy and dual particle size composites. The strengthening mechanisms that contributed to improvement in strength values were effective load transfer and dislocation strengthening due to thermal mismatch. Highlights • Uniform dispersion of dual size SiC particles in A357 matrix. • Continuous interface and good bonding between A357 matrix and dual size SiC particles. • Significant improvement in hardness and mechanical properties of dual size composites compared to A357 alloy. • Improvement in wear resistance of dual size composites compared to A357 alloy. [ABSTRACT FROM AUTHOR]

Abstract P 2 O 5 -added Li 2 O-SiO 2 -Si 3 N 4 glasses were prepared by melt-quenching the liquid inside a glove box under a N 2 atmosphere. Studies on crystallization kinetics of the glasses show that the crystallization of oxynitride glasses is controlled by the three-dimensional interfacial growth mode of crystals (Avrami index = 2.70–3.90). The introduction of the nucleating agent P 2 O 5 can increase the crystallization ability, and the crystallization activation energy is reduced. X-ray diffraction and scanning electron microscope were used to investigate the crystallization behavior and phase formation of the glass-ceramics. In general, the addition of 3.0 mol% nucleating agent P 2 O 5 and two-step heat-treatment facilitate the precipitation of rod-like Li 2 Si 2 O 5 crystals with high aspect-ratio, which are uniformly embedded in the glass matrix and show interlocking and uniform morphology, thereby improving the mechanical properties of Li 2 O-SiO 2 -Si 3 N 4 oxynitride glass-ceramics. This work provides a roadmap for the preparation of high performance glass-ceramics. Highlights • Crystallization kinetics study show three-dimensional interfacial growth mode for glasses. • P 2 O 5 can act as effective nucleating agent to promote crystallization of oxynitride glass. • Rod-like Li 2 Si 2 O 5 with high-aspect-ratio contribute to improvement of bending strength. • This work provides a roadmap for the preparation of high properties glass-ceramics. [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]

The microstructures and mechanical properties of as-cast Mg-5Nd- x Al ( x = 0, 0.8, 1.6, 2.4 and 3.0 wt%) were investigated by the optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and uniaxial tension test. The addition of 3.0 wt% Al led to the most significant grain refinement of Mg-5Nd alloy with the reduction of average grain size from 448 μm to 68 μm. The grain refinement was attributed to the formation of Al 2 Nd particles as the Al 2 Nd particles acted as effective grain refiners for the Mg matrix confirmed by XRD analysis, SEM observation, and crystallography calculation. The mechanical properties of as-cast Mg-5Nd alloy increased obviously after the addition of Al. The yield strength, ultimate tensile strength and elongation of the as-cast Mg-5Nd-3.0Al alloy were enhanced by about 45.3%, 72.4% and 264.0%, respectively, compared to as-cast Mg-5Nd alloy. The improvement of mechanical properties was mainly ascribed to the refined grains and secondary phase strengthening. [ABSTRACT FROM AUTHOR]

Titanium silicon nitride (TiSiN) thin films were deposited on p-type c-Si (100) with different N 2 flow rate by using chemical vapor deposition (CVD) technique. The microstructure, phonon modes, mechanical properties and compositional study of TiSiN thin films were characterised by scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy, nanoindentation and X-ray photoelectron spectroscopy (XPS),respectively. The SEM images show increases in surface roughness with increasing of N 2 flow rate, however, improves the hardness and Young's modulus of TiSiN thin film. The XRD analysis reveals the presence of strain in TiSiN films. The estimated crystallites of TiSiN thin films was 7.51 and 7.39 nm for 40 and 100 sccm N 2 flow rate. The XPS reveals the presence of 20 at. % Si content at 40 sccm N 2 flow rate in the TiSiN film. To analyse the broad Raman spectra of TiSiN thin films, the peaks were convoluted into six individual Gaussian peaks. The quantitative and qualitative analysis XPS and Raman spectra of TiSiN thin films were carried out by using Origin 9.0 software. [ABSTRACT FROM AUTHOR]

The effect of neodymium (Nd) additions from 0 to 0.2 wt.% on microstructure, mechanical properties at room and high temperature, as well as corrosion resistance of 2A70 alloy were studied by optical microscopy (OM), scanning electron microscope (SEM), transmission electron microscopy (TEM) in this paper. The results show that appropriate addition of Nd (0.15 wt.%) refines the size and enhances the density of the aging precipitates S′ phase, which lead to the increasing of mechanical properties at room and elevated temperatures. The newly formed Al8Cu4Nd compound, dispersed along grain boundary, which hinders the movement of grain boundaries at elevated temperature and improves the high temperature performance of 2A70 alloy. Compared with traditional 2A70 alloy, the intergranular corrosion of the peak-aged alloy with 0.15 wt.% Nd has also been effectively enhanced. [ABSTRACT FROM AUTHOR]

The fabrication method of composite materials has significant influence on the mechanical properties of the materials. Establishment of proper bonding, dispersion and diffusion of reinforcement in the matrix are identified as principal characteristics which need to be taken care during the manufacturing of metal matrix composites. The current work has highlighted the impact of metal (Al) mixed dual size particle reinforcements (Al 2 O 3 (μm) & Si 3 N 4 (nm)) and the domination of silicon nitride nano particle in the composite system. The reinforcement powders were ball milled for 3 h. The matrix alloy used in this work was AA6061 which holds the applications in the construction of structures, aircraft and automobile bodies. The matrix alloy was melted and milled powders were added at 850 °C followed by stirring process. The tensile, Compression and Hardness tests were conducted to characterize the mechanical behavior of the prepared composites. The Optical Microscope and the Scanning Electron Microscopes were used to analyze the morphology of the as-cast and fractured surfaces. The composites of metal mixed reinforcements offered improved mechanical properties than the composites of unmixed reinforcement. Tensile characteristics [Ultimate Tensile Strength (72.3 MPa–153.2 MPa), yield strength (67 MPa–148 MPa), and ductility (2–8.3%)] were much influenced by pre mixed Si 3 N 4 nano particles and its volume fraction in composites. The composites with dual reinforcement have shown superior tensile behavior than single reinforcement. The compression behavior [compression strength (253–361.74 MPa)] and hardness of the composites were dominated by single reinforcement with premixed Al 2 O 3 particles. The dislocation density due to the presence of Si 3 N 4 nano particle and proper bonding of hard Al 2 O 3 particles in the matrix supported by Si 3 N 4 nano particles were observed as strengthening mechanism in the composites with dual reinforcement. [ABSTRACT FROM AUTHOR]

The effects of carbon or boron addition on microstructure, mechanical properties, phase composition and distribution of the carbides and borides in Ti-48Al alloys were studied in this paper. Carbon and boron were added into Ti-48Al by various styles, such as boron powers or carbon powers, TiB 2 and TiC powers and B 4 C powers. The ingots were prepared by induction skull melting (ISM) with a water-cooled copper crucible. The tensile tests and fracture toughness tests at room temperature were investigated. Meanwhile, the as-cast microstructures were analyzed by the scanning electron microscope (SEM) and the transmission electron microscope (TEM). The grain sizes were estimated by a line intercept technique on at least ten OM micrographs and EBSD. It could be observed that the Ti-48Al alloys containing 0.2 at.%B 4 C with smaller grains exhibited the excellent tensile strength and elongation among the alloys, 517 MPa and 0.471%, respectively. The effects of boron and carbon addition on distribution of borides and carbides were analyzed. It could be found that borides and carbides distributing uniformly in microstructure also provided better fracture toughness for Ti-48Al-0.2B 4 C alloys. [ABSTRACT FROM AUTHOR]

The effects of VC/Cr 3 C 2 on WC grain morphologies and mechanical properties of WC-6wt. %Co cemented carbides were studied using scanning electron microscope (SEM) and mechanical properties tests. The results showed that the morphologies of WC grains in alloys doped VC were equilateral triangle with multi-steps in basal and prismatic planes because of the V segregate at (0 0 0 1) and slightly at (1 0 1 ¯ 0) surfaces of WC grains as (V, W) Cx carbide. However, the surfaces of triangle WC grains tended to become round without multi-steps as the VC grain inhibitor was partially replaced by Cr 3 C 2 . With the addition of VC, the hardness was improved due to the decrease of WC grain size and the transverse rupture strength decreased due to the multi-steps in WC grains. Additionally, the hardness and transverse rupture strength of the alloys had a little change with the partial substitution of VC by Cr 3 C 2 . [ABSTRACT FROM AUTHOR]

The single-phase TiNbZrMo x (x = 0, 0.3, 0.5, 0.7, 1) high-entropy alloys (HEAs) were prepared by arc melting. The relation between molybdenum, microstructure, mechanical properties and wear resistance was investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), universal tensile tester, hardness tester, friction tester, and wear tester. The results showed that TiNbZrMo x alloys were composed of a single BCC phase. With the increase of Mo elements, the crystallite size of the as-cast alloy decreased first and then increased, both the alloy strength and hardness were increased and compressive strain plasticity was decreased. TiNbZrMo 0.5 has the best comprehensive performance with a yield strength of 1.0 GPa, compressive strength of 1.3 GPa, and hardness of 429 HV; compared with TiNbZrMo 0 , yield strength increased by 77.32%, compressive strength increased by 25.14%, and hardness increased by 70.24%; and its specific wear rate decreased by 50%, while it's compressive plasticity only decreased by 5%. • The addition of appropriate amounts of molybdenum improves the strength, hardness and wear resistance of TiNbZrMo x HEAs. • Compared to TiNbZr, TiNbZrMo 0.5 has the best overall performance. • The main wear mechanisms of TiNbZrMo x (x = 0, 0.3, 0.5, 0.7, 1) are abrasive wear and oxidative wear. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) has been broadly employed for bone treatment applications. In the present research, HA was extracted from hen, goat and cattle bone. Samples were prepared by cold isostatic pressing method (CIP) and sintered at 1100, 1200 and 1300 °C. In order to evaluate the characteristics of the produced HA, X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier Transform spectroscopy (FTIR), scanning electron microcopy (SEM) and energy dispersive spectroscopy (EDS) analyses were carried out on it. Hardness and compression tests were examined before and after sintering. Also, the morphology of the samples at different sintering temperatures was studied by SEM imaging. The obtained experimental results ascertained that with increasing the sintering temperature up to 1300 °C, relative density and hardness of the samples increased. Finally, compressive strength of the sintered sample at 1200 °C was determined as maximum value. [ABSTRACT FROM AUTHOR]

The effects of Gd addition on microstructure, mechanical properties and corrosion behavior of degradable Mg-17Al-7Cu-3Zn- x Gd ( x = 0, 1, 2, 3. weight fraction) alloys were investigated using optical microscope, scanning electronic microscope equipped with energy dispersive spectroscope, compression tests, electrochemical measurements, and immersion tests. The main phases in the alloys with rare earth Gd consist of α-Mg、β-Mg 17 Al 12 、T (Al 13 Mg 14 Cu 5 Zn 1 ) and (Al,Mg) 3 Gd. The Mg-17Al-7Cu-3Zn-1Gd alloy exhibits the maximum yield strength of 302 MPa, ultimate compression strength of 440 MPa, and degradable corrosion rate of 0.21 mm/day. The significant improvements in compression strength and degradable rate were attributed to the dense network-shaped β-Mg 17 Al 12 phase forming on the grain boundaries of the α-Mg matrix and tubular-shaped T phase. The cuboid-shaped (Al, Mg) 3 Gd phases refine the grain size, and thus improve the mechanical properties and corrosion resistance of the based alloys. [ABSTRACT FROM AUTHOR]

This work aimed at investigating the superiorities of multilayer graphene (MLG) and β-Si 3 N 4 whisker (β-Si 3 N 4w) in synergistically enhancing the toughness of Si 3 N 4 ceramic composites. First, Si 3 N 4 ceramic composites with hybrid 1 wt% MLG and 0 – 5 wt% β-Si 3 N 4w were sintered by spark plasma sintering. Phase constitutions and microstructures of Si 3 N 4 -based ceramic composites were characterized by X-rays diffraction, Raman spectra, and scanning electron microscope. Then, the optimal β-Si 3 N 4w content and sintering process of MLG/β-Si 3 N 4w -toughened Si 3 N 4 ceramic composites were comprehensively optimized by orthogonal experiments. Results indicated that in the case of maintaining the hardness of 15.87 – 18.84 GPa, the fracture toughness of Si 3 N 4 ceramic composites incorporated with 1 wt% MLG and 3 wt% β-Si 3 N 4w was advanced to 11.04 MPa·m1/2, which was 11.29% and 87.12% higher than that of 1 wt% MLG- and 3 wt% β-Si 3 N 4w -reinforced Si 3 N 4 ceramic composites, respectively. Orthogonal experiments demonstrated that 1 wt% MLG/3 wt% β-Si 3 N 4w -toughened Si 3 N 4 ceramic composites sintered at 1600 ℃, 40 MPa, and holding time for 6 min had optimum comprehensive mechanical properties. MLG wrapping and the synergistic effects of pull out, crack deflection, crack branching, and bridging resulted by MLG and β-Si 3 N 4w were the main responsible for the enhancement of toughness. [Display omitted] • MLG/β-Si 3 N 4w synergistic toughened Si 3 N 4 ceramics were sintered by SPS. • Fracture toughness of Si 3 N 4 -based ceramics was enhanced to 11.04 MPa·m1/2. • Optimal contents of MLG and β-Si 3 N 4w were 1 wt% and 3 wt%. • Optimum sintering process were 1600 ℃, 40 MPa, and holding time for 6 min. [ABSTRACT FROM AUTHOR]

Cu-1 wt%Al 2 O 3 composite powder, prepared by mechanical milling and consolidated by spark plasma sintering to have about 98–99% of theoretical density, were characterized by scanning electron microscope, focused ion beam microscope, X-ray diffraction, nanoindentation and transmission electron microscope. The mechanically milled powders, upon consolidation, exhibited a finer grain size of 2 μm. Tensile deformation behavior of this composite, at ambient temperature but over the strain rates of 10 −4 s −1 to 5 × 10 −2 s −1 , exhibited typical manifestations of dynamic strain ageing in the form of serrations and negative strain rate dependence of flow stress. The yield and ultimate tensile strengths, and so also the elongation decrease gradually with increase in strain rate. Such variation was also shown by nanoindentation hardness as a function of loading rate over 1–100 mN/s. The observed results are explained by the dislocation structure evolved from its interaction with Al 2 O 3 dispersoids and impurity atoms like Fe, C and O coming from the powder processing. [ABSTRACT FROM AUTHOR]

To optimize the mechanical properties of Ti(C,N)-based cermets used as tool materials, the cermets with different Ni–Co binder contents and Co/(Ni + Co) weight ratios were prepared. The effects of metal binder content and Co/(Ni + Co) ratio on the microstructure and mechanical properties of Ti(C,N)-based cermets were investigated by scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and measuring the transverse rupture strength (TRS), Vickers hardness ( HV ) and fracture toughness ( K IC ). The experimental results reveal that increasing Ni–Co binder content can increase the thickness of rim phases by improving the solid solution reaction and the wetting of hard phases. The cermets with 25 wt.% binder addition present good comprehensive mechanical properties, which is attributed to the moderate rim phases and uniformly distributed Ti(C,N) grains. The Co/(Ni + Co) weight ratios in binder have a great influence on the grain sizes and microstructure features of Ti(C,N)-based cermets, in virtue of the synergic effects between the wettability of Co and the solubilizing capacity of Ni on hard phases. The cermets with pure Co as binder exhibit optimal mechanical properties with a TRS of 1767 ± 81 MPa, a hardness of 12.26 ± 0.10 GPa and a K IC of 8.40 ± 0.47 MPa m 1/2 , which meet the requirements for tool materials. And the cermets with a Co/(Ni + Co) ratio of 0.2 have the second best mechanical properties with a TRS of 1848 ± 201 MPa, a hardness of 11.12 ± 0.40 GPa and a K IC of 9.43 ± 0.54 MPa m 1/2 , in which the lower hardness can be further improved by optimizing the compositions and sintering process. [ABSTRACT FROM AUTHOR]

As-explosive welded clad plates usually show poor ductility due to heavily deformed microstructures developed after explosive welding (EXW). In this study, the feasibility of improving mechanical properties of an EXWed Mg–6Al–1Zn–1Ca (AZX611)/Al–0.6Mg–0.6Si–0.1Fe (A6005C) (all in wt%) clad plate has been explored by subsequent hot-rolling. Increasing the thickness reduction per pass from 10% to 28% or decreasing the rolling temperature from 430 °C to 250 °C is shown to enhance tensile properties. The joint sheet rolled at 250 °C with a thickness reduction per pass of 28% shows a large fracture elongation of 15%, which is significantly higher than that of the as-EXWed clad plate, 1.2%. Microstructure characterization by means of scanning electron microscope, electron backscatter diffraction and transmission electron microscope reveals that the substantial improvement in ductility is intimately related to a significant reduction of the accumulated strain in AZX611 and A6005C alloy sheets and an elimination of the interface delamination formed during EXW. A certain degree of anisotropic mechanical properties is observed in all sheets regardless of rolling conditions, which can be ascribed to the mechanical anisotropy originated from the AZX611 and A6005C alloy sheets. • Producing high performance lightweight Mg/Al joint sheets by explosive welding followed by conventional hot rolling. • Characterizing microstructure and evaluating mechanical properties of EXWed Mg/Al joint sheets rolled in different conditions. • Providing an in-depth understanding of the relationship between rolling condition, microstructure and mechanical properties. [ABSTRACT FROM AUTHOR]

The Mg-12Gd-2Er-0.4Zr (GE122K) is fabricated by double extrusion, and the effects of grain refinement and precipitate evolution on the mechanical performance of the extruded alloys are deeply analyzed. Scanning electron microscope results spectacle that some bulky precipitates in the single extruded alloy are fragmented to fine precipitates during double extrusion and distribute linearly along the extrusion direction (ED). The fine precipitates exhibit the strongest dispersion strengthening effect, whereas the bulky precipitates act as crack resources and decrease the elongation. After double extrusion, a refined grain structure with an average grain size of 2.7 µm is achieved, which is attributed to dynamic recrystallization (DRX). Moreover, double extrusion boosts the content of rare-earth elements into the matrix by dissolving the fine precipitates. During aging, extensive β′ precipitates form in the double extruded alloy than in the single extrude alloy. As a result, refined grains and strong precipitation strengthening make a significant contribution to a high yield strength (YS) of 422 ± 1.59 MPa with an elongation (EL) of 6.5 ± 0.89% in the double extruded+peak-aged alloy (ACX2). The possible strengthening mechanisms are discussed, and it is found that grain refinement and precipitate strengthening are the main contributors to the high strength of the GE122K alloy. Fabrication of Mg-12Gd-2Er-0.4Zr (wt%) alloy via double extrusion+aging with excellent mechanical performance. [Display omitted] • A facile and robust fabrication mechanism is adopted to attain an excellent balance of yield strength and elongation. • Grain refinement and precipitates have different effects on the strength of Mg-12Gd-2Er-0.4Zr alloy. • The β′ precipitate strengthening is the dominate strengthening mechanism during aging treatment of the extruded alloys. [ABSTRACT FROM AUTHOR]

A suitable sintering method is important to obtain the Ti(C,N)-based cermets with superior properties. In this paper, Ti(C,N)-based cermets were fabricated by hot-pressing sintering (HP) and conventional pressureless sintering (PLS) technology, respectively, to investigate the influence of different sintering methods on the microstructure and mechanical properties of cermets materials. The microstructure, fracture morphology, indention cracks and phase composition were observed and detected using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The transverse rupture strength (TRS), Vickers hardness ( HV ) and fracture toughness ( K IC ) were also measured. The results reveal that all of the Ti(C,N)-based cermets exhibit core–rim microstructures with black cores, white cores and grey rims embedded into metal binder phases. The grain size of the samples fabricated by HP is much finer and the structure is more compact than those fabricated by PLS, while there exist pores in the HP sintered samples. The sintering process has no influence on the phase composition of cermets, but affects the phase content and crystallinity. The samples fabricated by PLS present higher transverse rupture strength, fracture toughness and density than samples fabricated by HP. However, the HP sintered samples possess a higher hardness. [ABSTRACT FROM AUTHOR]

• A 3D Microstructure-based finite element modeling of TiB 2 /Cu composites was established. • Numerical evaluation and experimental verification of mechanical properties and fracture behavior for TiB 2 /Cu composites are implemented. • It provides useful guidelines for optimum composite structures design in TiB 2 /Cu composites. [Display omitted] In this paper, according to the geometric characteristics of TiB 2 particle acquired from the scanning electron microscopes (SEM), computational structural modeling of TiB 2 /Cu composites is performed, in which the size, shape, position, volume fraction and proportion of TiB 2 particles are numerically reproduced to be similar to those of the actual micro-structures of TiB 2 /Cu composites. The ductile damage and failure behaviors for matrix, the elastic brittle failure for the particle reinforcement, and the traction-separation for interface, were independently simulated in this model. Four evaluation indexes such as elastic modulus, yield strength, tensile strength and elongation are used to assess the comprehensive mechanical properties of composites. Load-bearing capability of the TiB 2 /Cu composites is investigated by analyzing the stress and strain distribution of particles, interface and matrix. The validity of the simulation results is verified by the agreement of the experimental stress-strain curve and the morphology of fracture section. The effects of particle size, shape, volume fraction and proportion of TiB 2 particles on the mechanical behavior are presented. The present work may provide useful guidelines for optimum composite structures design and industrial applications. [ABSTRACT FROM AUTHOR]

Al-Zn-Mg-Cu alloy, as an important lightweight structural material in the aerospace field, has ushered in a broader application space and proposed higher performance requirements. This paper presents the experimental investigation of the effect of Zr content on the microstructure refinement and performance improvement of cast Al-5.8Zn-2.3Mg-1.7Cu alloy, aiming to optimize the additional amount of Zr, refine the alloy grains, and improve the microstructure uniformity and mechanical properties. The chemical component, phase, and microstructure were observed by inductively coupled plasma, X-ray diffraction, optical microscope and scanning electron microscope; the hardness and mechanical properties were measured by Brinell hardness tester and tensile testing machine. The addition of different contents of Zr into the alloy can form fine dispersed or primary coarse Al 3 Zr phase, which has a significant effect on the microstructure and mechanical properties of the alloy. The results indicate that the addition of 0.05 wt% Zr does not significantly improve the grain refinement and mechanical properties, but the Brinell hardness reaches the maximum. As the Zr content rises, the grain refinement effect becomes more obvious, while the mechanical properties first increase and then decrease. The addition amount reaches 0.20 wt%, the second dendrite arm spacing is the smallest, the ultimate tensile strength, yield strength and elongation at room temperature reach the maximum of 296.74 MPa, 249.41 MPa and 8.26%, respectively. When the amount of Zr added exceeds 0.20 wt%, the existence of coarse and brittle primary Al 3 Zr phase reduces the mechanical properties, and the fracture morphology changes from ductile to brittle intergranular fracture. • Zr element can refine the alloy grains. The higher the amount of Zr added, the more obvious the grain refining effect. • With the increase of Zr content, the mechanical properties of the alloy will first increase and then decrease. • When Zr content is excessive, the Al 3 Zr phase is the reason for the decrease in toughness. [ABSTRACT FROM AUTHOR]

Abstract: Single-wall carbon nanotubes (SWCNTs) functionalized 63Sn–37Pb solders was synthesized. Composite solders up to 1wt.% reinforcement of SWCNTs were prepared. The composite specimens were characterized by X-ray diffraction (XRD), Field-emission scanning electron microscope (FE-SEM). Melting characteristics of the SWCNT based solders were determined by differential scanning calorimetry. Microstructures of the composite solders were examined by FE-SEM at higher magnification for the observation of the CNT distribution. Mechanical properties of the composite specimens were compared with those of the pure 63Sn–37Pb solder specimens and found that the ultimate tensile strength increased by 30% with the 0.3wt.% addition of CNTs. Hardness values of the CNT based composites have shown higher Vickers hardness compared to un-reinforced counterparts. The enhanced mechanical properties are resulting from the possible load-transfer mechanisms of the CNTs, which is discussed in detail. The fractrographic examination conducted by FE-SEM indicated the existence of ductile features in the form of dimples in all the composite solders with different weight proportions; it is evident from the micrographs that much reduced ductility is observed in the specimens reinforced with the higher wt.% of CNTs. [Copyright &y& Elsevier]

In this research work, the 6111Al reinforced by rare earth element Er was subjected to severe plastic deformation with different rolling reduction ranging from 50%, 70%–90% respectively. Continuous deepening of the dynamic recrystallization occurred during the increment on rolling deformation and the average size of α-Al grains decreased to 7.9 μm eventually. The nanosized Al 3 Er particles were characterized by the combined function of inhibiting and promoting the DRX at the same time during the rolling process. And the competitive relationship between the driving force and the restraining force has been studied via systematic calculation here. A noticeable enhancement on 6111Al–Er alloy has been obtained with YS, UTS and elongation increasing to 359 MPa, 380 MPa and 27.4% respectively when the rolling deformation reached to 90%, which was attributed to the synergistic strengthening effect induced by the fine grain strengthening and the Orowan strengthening mechanisms. The evolution of microstructure was characterized by the equipments including Electron backscattered diffraction (EBSD), Scanning electron microscope (SEM) and High resolution transmission electron microscope (HRTEM). • Multi round dynamic recrystallization occurred during the rolling process. • Al 3 Er particles possess combined function of inhibiting and promoting the DRX. • Mechanical properties of 6111Al is enhanced notably by rolling and Er addition. [ABSTRACT FROM AUTHOR]

The hard anodizing process is one of the best choices to achieve high wear resistance in a 6061-Al alloy, which is commonly used in marine and aerospace applications. In this study, the hard anodizing process was performed by applying several current densities at different times. Two types of electrolytes containing various concentrations of sulfuric acid or oxalic acid were used as the bath. The microhardness of the coatings was measured. Morphology, thickness, and structure of the samples were investigated through a scanning electron microscope (SEM), and an X-ray diffractometer (XRD). Surface roughness and tribological behavior of the optimum samples were also examined. The results revealed that there was an optimum value for the electrolyte concentration, as well as the hard anodizing current density and time at which the hardest coating was obtained. All the oxide films had an amorphous structure. Doing the hard anodizing at 35 mA/cm2 in a sulfuric acid bath for 50 min resulted in a uniform and crack-free coating. The weight loss of this oxide film was 50 and 21 times lower than the substrate and the coating obtained in an oxalic acid bath at the optimum conditions, respectively. • Hard anodizing of 6061-T6 Al alloy in the sulfuric and oxalic acid baths. • Effect of electrolyte concentration, current density, and time on properties. • Sulfuric acid was better electrolyte than oxalic acid for hard-anodizing of 6061-Al. • All the hard-anodized films had higher hardness and wear resistance than base alloy. • Optimum condition to obtain compact, hard and wear resistant coating is proposed. [ABSTRACT FROM AUTHOR]

The chemically architectured alloys were proposed as a new concept of microstructure, with a multi-scale architecturation. They are composed of a solid-solution at the atomic scale, grain boundaries and composition gradients at the micronic scale and finally a 3D network of gradients at the mesoscale. Composition gradients are between two phases with the same crystalline structure but different compositions. As a first application of this concept, powders of pure Ni and CoCrFeMnNi high entropy alloy were successfully densified by Spark Plasma Sintering. Then the microstructure and mechanical properties were characterized by scanning electron microscope coupled with energy dispersive spectroscopy and electron backscattered diffraction, X-ray diffraction, nanoindentation and compression tests. The obtained chemically architectured alloys present a homogeneous distribution of the two phases with a 10 μm wide chemical gradient in between. By comparison with reference non architectured materials, the chemical architecturation induces a 35% increase of the yield strength. Thus the concept of chemically architectured metallic alloys and composition gradients was proven as very promising: processing of this complex microstructure is possible and it induces a significant mechanical strengthening. Image 1 • A mixture of CoCrFeMnNi and Ni powders was fully densified by spark plasma sintering. • A chemical gradient of around 10 μm was formed between HEA and Ni phases. • This material is called a chemically architectured alloy. • Mechanical strength is improved compared to an ideal mixture of Ni and CoCrFeMnNi. [ABSTRACT FROM AUTHOR]

To determine the effect of heating and water-cooling on the mechanical properties of the WC-Co coatings, we conducted a series of mechanical tests on the HVOF (high-velocity oxygen-fuel) sprayed WC-Co samples. These coatings were first heated to the target temperatures (200–800 °C), followed by rapid cooling with water. Mechanical properties were tested after thermal treatments. Microstructural changes were also observed using a scanning electron microscope and optical microscope. According to experimental results, the microhardness, residual stress and adhesive strength of the heated WC-Co coating changed significantly after water-cooling. As heating temperature rises, changes in these properties become more pronounced. However, the number of cycles has less effect on the mechanical properties of the coatings and the effect mainly occurs in the first 30 cycles. Compared with the argon-cooling method, water-cooling induces greater changes in the mechanical properties at higher target temperatures. This indicates that water-cooling can damage the heated WC-Co coatings more remarkably than the other cooling treatment. Nevertheless, after about 30 cycles, changes in mechanical become less pronounced. Additionally, cobalt content has little impact on the mechanical properties of the coating after heating and water-cooling. • The effects of heating and water-cooling on the WC-Co coatings were investigated. • Temperature is the main factor affecting the properties of the coating. • Phase transformation and crack growth affect the properties of the coating. • Reducing vibration of the hammer can increase the service life of the coating. [ABSTRACT FROM AUTHOR]

In the quest of novel, reasonable and effective reinforcement, it is very hard to find rare combination of materials which attempts to accord and benefit each other. The exhausted waste spent catalyst from petroleum industries is experimented as a reinforcement obliging to the concept of reuse and recycle. In this investigation, aluminium metal matrix nano composite is to be synthesized by double stir casting method. Pure aluminium and Spent Alumina Catalyst (SAC) is chosen as matrix and primary reinforcement respectively. Nano CuO is added as secondary reinforcement to enhance the mechanical properties of aluminium spent alumina catalyst composite. The composites are synthesized as such, 10% SAC is reinforced to pure aluminium and the amount of nano CuO is varied 0.5%, 0.75%, 1%. Microstructural characteristics of cast composites and tensile samples is studied under Scanning Electron Microscope. There is no clogging of reinforcement materials (nano CuO and SAC) in the aluminium matrix. The mechanical properties of the composites are determined and compared with pure aluminium. There is an impact of dual reinforcement on aluminium matrix which is evident by the improvement in the mechanical properties of the composite. The optimum composition is Al + 10%SAC +1%nano CuO, which resulted in maximum increase in hardness (77%) and tensile strength (78%). • Reuse of Spent Alumina Catalyst (petroleum industrial waste) as a reinforcement. • Synthesis of Aluminium nano composite with Dual Reinforcement (Spent Alumina Catalyst + nano Copper Oxide) by Stir Casting. • Evaluation of microstructure and mechanical properties of newly synthesized composite. • Enhanced mechanical Properties. [ABSTRACT FROM AUTHOR]

To investigate the effect of oxide additives on the mechanical characteristics of Ag-based contact materials, the Ag/SnO 2 tensile samples with CuO and Cu 2 O were prepared by powder metallurgy method. The mechanical properties of the prepared Ag/SnO 2 materials were tested on a special tensile machine. And, the effect of cyclic loadings on the mechanical characteristics of the prepared samples was also studied. The tensile fractures of the Ag/SnO 2 samples were analyzed by a Scanning Electron Microscope (SEM). The results showed that a small amount of CuO and Cu 2 O additives had remarkable influence on the mechanical characteristics of the Ag/SnO 2 materials. The Ag/SnO 2 samples with 0.5 wt% Cu 2 O exhibited the optimal mechanical property. The ultimate strength and uniform elongation were increased by 60% and 21%, respectively. The CuO and Cu 2 O additives suppressed the growth of intergranular cracks in the Ag/SnO 2 materials by the formation of larger dimples around SnO 2 particles. The cyclic creeps of the Ag/SnO 2 samples with copper oxides were also obviously decreased. These results indicated that a moderate amount of cupper oxides especially Cu 2 O was beneficial for improving the processability of Ag/SnO 2 contact materials. Image 1 • The processability of the Ag/SnO 2 samples was improved by adding CuO and Cu 2 O.. • The ultimate strength and uniform elongation of the Ag/SnO 2 materials with copper oxides were effectively increased.. • The CuO and Cu 2 O additives suppressed the growth of intergranular cracks in the Ag/SnO 2 tensile materials.. • The creep deformations of the Ag/SnO 2 samples with copper oxides were obviously decreased. [ABSTRACT FROM AUTHOR]