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Dissimilar Ti-based amorphous alloy sheets were butt welded by a pulsed laser and metallurgical joints were obtained. The β-Ti crystal grains in nanometre scale unevenly distribute on the amorphous...

In our work, NiCo2O4@Ni(OH)2 electrode materials are prepared by a two-step hydrothermal method. The synthesized product can be directly used as electrode material of a supercapacitor, and its specific capacity is 687 C g−1 at 1 A g−1. The composite electrode is used as the positive electrode and a hybrid capacitor is assembled. The ASCs (asymmetric supercapacitors) possess an energy density of 71.38 Wh kg−1 at a power density of 2750 W kg−1 and capacity retention of 92% after 10,000 cycles.

Ternary mixed metal sulfide is a potential pseudocapacitive material. In this work, ZnS nanowire and NiCo2S4 nanosheet were grown on nickel foam through hydrothermal method. As compared with NiCo2S4/NF and ZnS/NF, ZnS/NiCo2S4/NF has a significant supercapacitance. The surface capacitance is as high as 2604 mF cm−2 at 1 mA cm−2, and still keep 1020 mF cm−2 with electric current density of 10 mA cm−2. The ZnS/NiCo2S4/NF nanostructures have large capacitance retention rate of 90% after 6000 laps in condition of 8 mA cm−2. The prepared ZnS/NiCo2S4/NF//ASC device displayed both high power density and energy density (725 W kg−1 at 39.88 Wh kg−1).

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.

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.

The coupling effect between a laser and arc plasma was studied in situations in which the laser acts at the positive and negative waveforms of the arc discharge during the laser-arc hybrid welding of magnesium alloy. Using the methods of direct observation, high speed imaging, and spectral analysis, the surface status of weld seams, weld penetration depths, plasma behavior, and spectral characteristics of welding plasma were investigated, respectively. Results show that, as compared with the laser pulse acting at the negative waveform of the arc plasma discharge, a better weld seam formation can be achieved when the laser pulse acts at the positive waveform of the arc discharge. At the same time, the radiation intensity of Mg atoms in the arc plasma increases significantly. However, the weld penetration depth is weaker. The findings show that when the laser pulse is acting at the negative waveform of the arc plasma discharge, the position of the arc plasma discharge on the workpiece can be restrained by the laser action point, which improves the energy density of the welding arc.

The elastic performance of kirigami metallic glasses (MGs) plays a key role for their applications as potential mechanical metamaterials, however, the mechanisms on how to achieve programmable large elasticity in these kirigami MGs are still unknown. In this work, kirigami MGs, with programmable stretchability reaching 317%, were fabricated, demonstrating super elasticity larger than 277%. The high stretchability and super-elasticity are mainly attributed to the elastic out-of-plane bending of the kirigami elements rather than rigid deformation. The super elastic kirigami MGs can be developed for use as high stretchable mechanical/functional metamaterials/devices, such as wearable sensors and stretchable electronics. Keywords: Kirigami, Metallic glass, Elasticity, Stretchability, Metamaterials

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.

NiCo2O4 nanosheets for hybrid supercapacitors with long cycle stability are successfully fabricated by a one-step hydrothermal method. The battery type electrode material shows capacitances of 571.3 mAh g−1 at 1 A g−1 and excellent cycling stability. The specific capacitance retention can still retain 100% at 5 A g−1 after 10,000 cycles. In addition, When acts as electrocatalyst, the as-prepared samples present a low overpotential of OER (290 mV) and HER (165 mV) at 10 mA cm−2, and a low cell voltage of 1.72 V at 10 mA cm−2 and long-term durability for 14 h, indicating that NiCo2O4 structure can effectively improve electrochemical performance, which provides a broad possibility for the further development of cheap electrode materials for overall splitting.

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.

The tensile plastic deformation of dendrite-reinforced Ti-based metallic glass composites (MGCs) was investigated. It was found that there is a critical normalized strain-hardening rate (NSHR) that determines the plastic stability of MGCs: if the NSHR is larger than the critical value, the plastic deformation of the MGCs will be stable, i.e. the necking and strain localization can be effectively suppressed, resulting in homogeneous plastic elongation. In addition, dendrite-reinforce MGCs are verified as being intrinsically ductile, and can be used as good coatings for improving the surface properties of pure titanium or titanium alloys. These findings are helpful in designing, producing, and using MGCs with improved performance properties.

The plastic flow of bulk metallic glasses (BMGs) is characterized by intermittent bursts of avalanches and this trend results in disastrous failures of BMGs. In the present work, a double-side-notched BMG specimen is designed, which exhibits chaotic plastic flows consisting of several catastrophic avalanches under the applied loading. The disastrous shear avalanches have, then, been delayed by forming a stable plastic-flow stage in the specimens with tailored distances between the bottoms of the notches, where the distribution of a complex stress field is acquired. Differing from the conventional compressive testing results, such a delaying process is independent of loading rate. The statistical analysis shows that in the specimens with delayed catastrophic failures, the plastic flow can evolve to a critical dynamics, making the catastrophic failure more predictable than the ones with chaotic plastic flows. The findings are of significance in understanding the plastic-flow mechanisms in BMGs and controlling the avalanches in relating solids.