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The automobile industry uses magnesium for load-bearing components due to its low density, durability, and ductility. This study investigated a nanocomposite containing Nb2O5 (3 and 6 wt%) nanoparticles as reinforcement with AZ31 magnesium alloy made by stir casting. A severe plastic deformation was conducted on the cast samples via equal-channel angular pressing (ECAP) after homogenization at 410 °C for 24 h and aging at 200 °C for 10 h. The microstructural distributions and mechanical properties of the magnesium metal matrix composites (MMCs) reinforced with Nb2O5 nanoparticles were investigated via ECAP. With the increase in the number of ECAP passes, the grain sizes became uniform, and the size of secondary phases reduced in the pure Nb2O5/AZ31 MMC. The grain size decreased remarkably after the ECAP process from 31.95 µm to 18.41µm due to the dynamic recrystallization during plastic deformation. The mechanical properties of hardness, ultimate tensile strength, and elongation effectively improved after each ECAP pass. The maximum values achieved for the Nb2O5/AZ31 composite subjected to ECAP were 64.12 ± 12 HV, 151.2 MPa, and 52.71%. [ABSTRACT FROM AUTHOR]

The impact of hot bending forming process on the high-temperature mechanical properties and hydrogen damage of 2.25Cr-1Mo-0.25V steel was investigated by scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive spectrum (EDS) and the slow strain rate tensile (SSRT) test in high-temperature hydrogen environment. The samples containing hot bending residual influence were extracted from a real hydrogenation reactor shell fabricated through hot bending-welding process. SEM images of the material demonstrated that the density and size of carbides in 2.25Cr-1Mo-0.25V increased after forming. TEM and EDS results revealed that ferrite matrix of the formed material was purified. The mechanical properties measured by SSRT test manifested that 2.25Cr-1Mo-0.25V was softened after forming. Moreover, it was observed that high-temperature hydrogen environment embrittled the material and the susceptibility to hydrogen damage increased after forming. The role of hot bending process on the evolution of mechanical properties and hydrogen damage susceptibility was discussed. Possible mechanism for the impact of hot bending process on the high-temperature hydrogen damage was proposed. [ABSTRACT FROM AUTHOR]

In the present work, advanced aluminium metal matrix composite reinforced by nanomaterials is reported. The materials used for the experiments are AA6061 aluminium alloy, compounded with inorganic nanotubes (INT) and fullerene-like (IF) nanoparticles of WS 2 . Aluminium metal matrix composite with different weight percentage (0.1–0.5 wt%) of the INT and IF were prepared. Both the AA6061 aluminium and the aluminium metal matrix nanocomposites (MMCs) were re-melted by the stirring-casting method. Mechanical properties and microstructure analysis of the nano-MMCs were conducted. The measurements have shown that the hardness, yielding strength, ultimate tensile strength, and ductility were improved by up to 68% compared to the neat alloy for nanoparticles concentrations the range of 0.2 wt%. Metallography microstructure analysis showed that increasing the WS 2 INT or IF nanoparticles weight percentage in aluminium metal matrix composite, resulted in a more refined grains. The grain size of the composite matrix was reduced by up to 48.4% compared with that of neat AA6061 alloy ingot. Scanning electron microscope (SEM) analysis showed that addition of 0.5 wt% of WS 2 nanotubes into the Al matrix resulted in INT agglomeration which had deleterious effect on the tensile strength. The composite materials reinforcement mechanism was studied. This analysis showed that the improved mechanical properties of the metal nanocomposites can be predominantly attributed to the differences in thermal expansion coefficients of the WS 2 INT (or WS 2 IF nanoparticle) and the AA6061 alloy. [ABSTRACT FROM AUTHOR]

This study analyzes the effect of substitution of Ni for Zn on microstructure and mechanical properties of Mg–Gd–Y–Zn–Mn alloy. Our results show that the volume fraction of Mg5(Gd, Y) and (Mg, Zn)3RE phase decreased and LPSO phase increased with more substitution of Ni. After homogenization, only α-Mg and LPSO phase existed. In Mg–Gd–Y–Zn–Mn alloys, the LPSO phases mainly consisted of the 14H type. While in Mg–Gd–Y–Ni–Mn alloy, the LPSO phases consisted of the 18R type. In addition, compared with Mg–Gd–Y–Zn–Mn alloy, the mechanical properties of as-extruded Ni-substitution alloys were improved due to the better refinement of the size of grains and LPSO phases. The tensile strength in as-extruded Mg–Gd–Y–Ni–Mn alloy could reach up to 400 MPa with 18% of the elongation to failure. [ABSTRACT FROM AUTHOR]

The process engineering of Mg alloys is nevertheless compromised due to their relatively poor mechanical properties. To address some of these difficulties, metal-matrix composites (MMCs) of Mg-alloys have been investigated for sometime. In the present work, small amounts (up to 1 wt%) of WS 2 nanotubes are mixed with Mg-alloy (AZ31) using melt-stirring process above 700 °C. The new MMC nanocomposites exhibit much superior mechanical properties vis a vis the pristine alloy. Metallographic investigation demonstrates that the average grain size has been reduced in inverse proportion to the added amounts of nanotubes up to 1 wt%. Physical considerations suggest that the main mechanism responsible for the reinforcement effect lies in the mismatch between the thermal expansion coefficients of the metal and the nanotubes. This mismatch induced large density of dislocations in the grain boundaries in the vicinity of the nanotube-matrix interface, which obstruct the crack propagation. [ABSTRACT FROM AUTHOR]

The mechanical properties and internal friction (damping capacity) of Mg–Zn–Y alloys with a long-period stacking ordered (LPSO) structure at different Y/Zn atomic ratios (2/1, 3/2 or 4/3) in cast and extrusion were investigated. It was found that the as-cast Mg–Zn–Y alloys with different Y/Zn atomic ratios possess a single LPSO phase with the same stable 18R-type structure. Among the three alloys, the alloy with 3/2 atomic ratio yields the highest damping capacity in low- and high-strain amplitude stages. Two damping peaks particularly P1 and P2 are detected in the Mg–Zn–Y alloy with 3/2 atomic ratio at approximately 108 and 220 °C, respectively. These results may be attributed to few solute atoms in Mg matrix and grain boundaries. In addition, the studied alloy with 3/2 atomic ratio exhibits excellent comprehensive properties in as-cast and as-extruded states; this alloy yields an ultimate tensile strength of 346 MPa and maintains a certain damping capacity (Q−1 > 0.01) in extrusion. [ABSTRACT FROM AUTHOR]

Abstract: The effects of Mn substitution for Mg on the microstructure, mechanical properties, and corrosion behavior of Mg69−xZn27Ca4Mnx (x=0, 0.5 and 1at.%) alloys were investigated using X-ray diffraction, compressive tests, electrochemical treatments, and immersion tests, respectively. Microstructural observations showed that the Mg69Zn27Ca4 alloy was mainly amorphous. The addition of Mn decreases the glass-forming ability, which results in a decreased strength from 545MPa to 364MPa. However, this strength is still suitable for implant application. Polarization and immersion tests in the simulated body fluid at 37°C revealed that the Mn-doped Mg–Zn–Ca alloys have significantly higher corrosion resistance than traditional ZK60 and pure Mg alloys. Cytotoxicity test showed that cell viabilities of osteoblasts cultured with Mn-doped Mg–Zn–Ca alloys extracts were higher than that of pure Mg. Mg68.5Zn27Ca4Mn0.5 exhibits the highest bio-corrosion resistance, biocompatibility and has desirable mechanical properties, which could suggest to be used as biomedical materials in the future. [Copyright &y& Elsevier]

Abstract: Mg69Zn27Ca4 with a spot of Fe particle-reinforced alloys was synthesized by Cu-mold injection casting using industrial raw materials. The microstructure, mechanical properties and corrosion resistance of these Mg-based alloys were studied by X-ray diffraction, differential scanning calorimeter, compressive testing and electrochemical measurements, respectively. The Mg69Zn27Ca4 alloy can be controlled to become fully amorphous using the industrial raw materials. With Fe particle addition, ductile α-Mg and Mg–Zn dendrites were embedded in the amorphous matrix, which enhanced the compressive strength and fracture strain. The Mg69Zn27Ca4 glassy alloy and Mg69Zn27Ca4/Fe alloy remarkably improved the corrosion resistance in 3.5wt% NaCl solution compared with AZ31 and pure Mg. Therefore, Mg69Zn27Ca4 and Mg69Zn27Ca4/Fe alloys have high potential as engineering materials. [Copyright &y& Elsevier]

High-performance as-extruded and peak-aged Mg-9.2Gd-3.3Y-1.2Zn-0.9Mn (wt%) alloys have been fabricated by semi-continuous casting, heat-treating, extruding and ageing processes. The effects of different heat treatments on the microstructure and mechanical properties have been investigated. Lamellar and bulk-shaped 14H-type long-period stacking ordered (LPSO) phase and few RE-rich (RE: rare earth element) particles form by different heat treatments. After hot extrusion, the heat-treated alloy with bulk-shaped LPSO phase exhibits an equal-axial microstructure, while the heat-treated alloy with lamellar LPSO phase across the grains shows bimodal grain microstructure consisting of fine equal-axial grains and coarse deformed grains. The more profuse lamellar LPSO phase in heat-treated alloy generates higher volume fraction of deformed grains and finer equal-axial grains, hence leads to higher strength but lower ductility. After ageing, the alloy with profuse LPSO and β′ phases achieves the superior mechanical properties with ultimate tensile strength (UTS) of 525 MPa, tensile yield strength (TYS) of 420 MPa and elongation to failure (EL) of 6.3%. The alloy strengthening is mainly attributed to the bimodal grain microstructure, LPSO phase, Mg 5 Gd (β) phase and β′ phase. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure and mechanical properties of Mg–8.40Gd–5.30Y–1.65Zn–0.59Mn (wt%) alloy were investigated in this study. The phase composition of the alloy involved an α-Mg matrix and long-period stacking ordered phases of Mg12Zn(Y,Gd) with some eutectic phases. After aging at 200°C for 50h following extrusion (extrusion ratio= 11:1, extrusion temperature=400°C), the alloy achieved high strength (ultimate tensile strength=∼500MPa, tensile yield strength=∼322MPa) and good ductility (elongation=∼10.0%) and exhibited excellent comprehensive mechanical properties. These properties could be attributed to the numerous plate-shaped β′ phase precipitates in the α-Mg matrix, as well as the small dispersed block-shaped long-period stacking ordered phases along the grain boundaries. [Copyright &y& Elsevier]