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The formation of shear bands in metallic glasses (MGs) was examined by tailoring localized complex stress fields (LCSFs). The findings have shown that the LCSFs in MGs can increase the localization of strained atoms and accelerate the release of accumulated deformation energy for initiating a shear band in confined and thin-layered regions. The findings not only add more knowledge to the formation mechanisms of shear bands in MGs, but also provide possible rationale for the discrepancies in the mechanical properties of different-sized MGs. As compared with the bulk samples, the higher strength and larger elastic limits in nanoscaled MGs could be attributed to the elimination of stress-concentrators, which can serve as LCSFs.

The microstructure and tensile properties of FexCoCrNiMn high-entropy alloys (HEAs) were investigated. It was found that the FexCoCrNiMn HEA has a single face-centered cubic (fcc) structure in a wide range of Fe content. Further increasing the Fe content endowed the FexCoCrNiMn alloys with an fcc/body-centered cubic (bcc) dual-phase structure. The yield strength of the FexCoCrNiMn HEAs slightly decreased with the increase of Fe content. An excellent combination of strength and ductility was achieved in the FexCoCrNiMn HEA with higher Fe content, which can be attributed to the outstanding deformation coordination capability of the fcc/bcc dual phase structure.

Lanthanum silicate (LSO) electrolytes doped with different valence cations are successfully synthesized by solid state reaction. Crystal structure, electrical properties, stability and compatibility with cathode materials are characterized. The measured total conductivities of LSO electrolytes doped with In3+, Nb5+ and W6+ are relatively high compared with that of undoped La10Si6O27, which is attributed to more carriers including either excessive oxygen vacancies generated when doping with In3+ or more interstitial oxide-ion O (5) generated when doping with Nb5+ and W6+. The thermal expansion coefficients of La10Si5.9A0.1O27±δ (A = In3+, Si4+, Nb5+, W6+) electrolytes vary from 8.48 to 8.83 × 10–6 K–1 at 1073 K. The doped LSO electrolytes match well with (La0.75Sr0.25)0.95MnO3±δ cathode at temperatures below 1573 K, which is highly stable, to some extent, in various atmospheres of CO2 or H2O vapour.

The effect of Cu addition on the microstructural evolution and mechanical properties of hypoeutectic Al-10Mg2Si alloys was investigated. It was found that Cu addition could effectively refine the primary α-Al grain. Simultaneously, the coarse eutectic Mg2Si was also modified to be fine coral-like. The constitutional supercooling and the multiple nanosized precipitating layers at the edge of the eutectic Mg2Si cause the branching and refining of the eutectic Mg2Si through effectively restricting the growth of eutectic Mg2Si, while The Cu-rich clusters and nanosized precipitates on the surface of the end of the eutectic Mg2Si prevent the diffusion of the solute atoms such as Al, Mg and Si, and the growth of eutectic Mg2Si grains is physically limited, resulting in the decrease of the length of eutectic Mg2Si. The strength and ductility of the Cu-added Al-10Mg2Si alloys were simultaneously improved, and the fracture failure mode transforms from brittle failure to ductile failure. The mechanism of mechanical properties enhanced by Cu addition was discussed.

In the present work, the influence of Bi on the microstructures, tensile properties, and fracture behavior of the cast Al-10Mg2Si alloys has been systematically investigated. It was found that Bi addition caused a significant modification and refinement efficiency on the eutectic Mg2Si in the cast Al-10Mg2Si alloys. The morphology of the eutectic Mg2Si in the cast alloys transformed from plate-like structure to a thin coral-like and fibrous one, and the mean size and aspect ratio sharply decreased with the increase of Bi content. Bi addition changed the mode of fracture from brittle to ductile due to the presence of a large number of deep and well-distributed dimples, and fine Mg2Si particles embedded in the Al-matrix, resulting in the significant improvement of the tensile properties of the cast Al-10Mg2Si alloys.

The dependence of microstructure and mechanical properties on alloy composition of a series of Cu48Zr48−xAl4Nbx (x = 0, 0.3, 0.8, 1.2, 1.5, 2.0 at.%) bulk metallic glass composites (BMGCs) was studied in detail. It was found that the doping element Nb exerts a crucial role on the mechanical properties of the studied BMGCs. By adjusting Nb content, a BMGC possessing an excellent combination of high strength (~1.3 GPa) and significant tensile plasticity (~8%) was obtained. Such superior mechanical performance can be attributed to the formation of multiple shear bands and the deformation-induced martensitic transformation from a cubic primitive B2 phase to a monoclinic B19′ phase.

Previous application of electromagnetic pulse (EMP) treatment during alloy solidification process provided a potential tool box for controlling alloys’ properties. In this work, EMP treatment was firstly applied during the preparation process of AlCoCrFeNi high entropy alloy (HEA), and its effects as well as mechanism were discussed. The crystal structure, microstructure, mechanical properties and corrosion properties of AlCoCrFeNi in current and perpendicular directions were characterized. The results demonstrated that EMP treatment can alter spinodal decomposition process, improve the plasticity and pitting corrosion resistance of AlCoCrFeNi HEA. The wall thickness of spinodal decomposed microstructure enlarges from 293.5 nm to 446.5 nm with EMP frequency increasing. Meanwhile, the compression ratio increases by 18.0% with sacrificing only 1.1% fracture strength. Pitting potential increased from −0.24–0.14 V in electric direction, while it increased form −0.26–0.05 V in magnetizing direction, which revealed that EMP treated samples have better pitting corrosion resistance than untreated state. In addition, alloy’s original anisotropy differences were reversed and altered with increasing EMP frequency.

AlCoCrFeNi2.1 high entropy alloy with a novel “steel-frame” eutectic microstructure was prepared and its microstructure, mechanical properties, and notch sensitivity were characterized. The alloy exhibits high strength and high ductility due to the unique steel framed eutectic microstructure that consists of face-centered-cubic (FCC) phase, L12 phase and B2 phase. This unique eutectic microstructure hinders dislocation movements and postpones the crack propagation. Considering the notch sensitivity of materials is critical to its application, U-shaped notches with four different notch radii were introduced to investigate the notch sensitivity and their effects on the deformation behavior. The results show that AlCoCrFeNi2.1 alloy is insensitive to the notch and the tensile properties of the notched specimens are improved compared to that of the un-notched counterpart.

The microstructure and tensile properties of the hypoeutectic Al-11Mg2Si alloy modified by the rare earth element erbium was comprehensively studied. It was found that addition of 0.1 wt% Er was efficient for modifying eutectic Mg2Si from coarse mazelike lamellar to fine coralline fiber with a decrease in aspect ratio of Mg2Si from 14.9 ± 2.3 µm to 1.2 ± 0.5 µm and a reduction in interlamellar spacing of eutectic Mg2Si from 2.7 ± 0.5 µm to 0.4 ± 0.2 µm. Furthermore, the eutectic grain transformed from columnar to equiaxial structure with an average size decrease from 41.2 ± 6.1 µm to 9.6 ± 2.5 µm. The excellent modification effect was attributed to the fact that the Er distribution produces undercooling and inhibits the growth of eutectic Mg2Si and grains. The tensile deformation results indicated that trace Er can effectively enhance the strength and the plastic deformation capability of the as-cast hypoeutectic Al-11Mg2Si alloy, especially a tremendously increase in elongation from to from 3.9 ± 0.3% to 12.6 ± 0.7%. The fracture mode changes from brittle mode with a smooth cleavage surface to ductile mode with dense dimples.

The first-principle calculations based on density functional theory (DFT) have been used to investigate structural and mechanical properties of Fe24−xAl8C8Mnx alloys. The calculated lattice constants of Fe3AlC were in accord with experimental values, and its lattice deformation increased with the doped content of Mn increasing. The calculated formation enthalpy indicated that Mn atom is more likely to locate in the center of each face of the Fe3AlC crystal lattice, and the Fe24−xAl8C8Mnx is a stable compound. The effect of Mn atoms on the independent elastic constants and the polycrystalline elastic parameters were calculated and discussed, such as bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratio ν, anisotropy value A and Vickers hardness Hv. The effect of Mn content on the melting temperature of the Fe3AlC alloys was also investigated, which represents the high temperature property. In addition, the density of states, the electron density difference, the population analysis and magnetic moment were also calculated to explain the mechanism of the structural stability, the chemical bonding and magnetization mechanism for the Fe3AlC and the Fe24−xAl8C8Mnx alloys at the electron level.

The effect of Gd element on the microstructure and tensile properties of a hypoeutectic Al-Mg2Si alloy, i.e. AlMg5Si2Mn alloy, was systematically studied. The results show that Gd can refine the primary α-Al phase and modify the eutectic Mg2Si phase in the Mg2Si reinforced Al alloy. With Gd addition, the morphology of the primary α-Al phase is varied from coarse dendrite to small round particle. Meanwhile, the morphology of the eutectic Mg2Si phase can change from mazelike thick lamellar to thin coralline fiber. The yield strength, ultimate tensile strength and the ductility are remarkably enhanced. It is proposed that the refinement of primary α-Al phase results from the formation of Al3Gd, and the modification of eutectic Mg2Si phase is attributed to the Gd segregation and composition supercooling in front of the growing Mg2Si phase.

Cutting behavior exerts a considerable influence on the fabrication of bulk metallic glass (BMG) components. In this study, the influences of machining parameters (i.e., depth of cutting, feed rate, and spindle rate) on the turned surface of a Zr-based BMG after observing the 3D morphologies of this surface were characterized. The results showed that the influence of the spindle rate on the surface morphologies is more substantial as compared to the depth of cutting and the feed rate. Nanoscratch tests were conducted to further characterize the separation mechanism of the chips, which revealed that the chips are torn off the surface of a BMG because of inhomogeneous localized maximum shear stress.

The influence of addition of Bi (0.2%-8.0%) on the microstructure and dry sliding wear behaviors of cast Al-15%Mg2Si in situ metal matrix composites was investigated. The microstructure features of the composites were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), and their wear characteristics were evaluated at different loads. The results show that the proper addition of Bi has significant modification effect on the morphologies of both primary and eutectic Mg2Si in the Al-15%Mg2Si composites. With the increase of Bi content from 0 to 4%, the morphology of primary Mg2Si changes from irregular or dendritic to polyhedral shape and its average particle size significantly decreases from 70 to 6 μm. Moreover, the morphology of eutectic Mg2Si phase also alters from flake-like to very short fibrous or dot-like shape. When the Bi content exceeds 4.0%, the primary Mg2Si becomes coarse again; however, the eutectic Mg2Si still exhibits modified morphology. The wear rates and coefficient of friction of the composites with Bi addition are lower than those without Bi. Furthermore, the wear mechanism of the composite changes from the combination of abrasive, adhesive and delamination wear without Bi into mild abrasion and adhesive wear with 1% Bi; the addition of 4% Bi effectively restrains the cracks in primary Mg2Si and on the worn surface of the composite and avoids adhesive and delamination wear, and thus only a single mild abrasion occurs. The improvement of wear performance of the composites with Bi is originated from the combination of Bi modification on Mg2Si and self-lubrication function of Bi particles in the friction process.