The mechanical properties and deformation mechanisms of bicontinuous Cu₅₀Zr₅₀ amorphous alloys are investigated via molecular dynamics simulation.

Thanks to their excellent properties such as superelasticity, high hardness, and shape memory effect, polycrystalline shape memory alloys (SMAs) have extensive applications in various engineering fields including automobile, functional materials, and aerospace. Using molecular dynamics simulations, the present paper aims to a systematic study of the fundamental tensile behavior in the nanoscale of polycrystalline B2-CuZr SMAs with mean grain sizes in the range of 6–25 nm. Effects of mean grain size, temperature, and tensile rate on mechanical properties are considered. Our results show that along with the increase in mean grain size came increases in Young's modulus, yield strength, flow stress, and ultimate tensile strength. The development of amorphous regions in the grain cores is the major deformation mode in polycrystalline CuZr SMAs with larger grain sizes, while the grain boundary sliding and grain rotation for smaller grain sizes. Besides, an increased temperature results in mechanical performance degradation and the temperature sensitivity of mechanical properties does not depend on the mean grain size. Our work would lay the groundwork for the optimization of the mechanical properties of polycrystalline SMAs as well as serving as a useful theoretical guideline for their practical engineering applications.

Nanoscale cold welding is a promising method in the bottom-up fabrication of nanodevices. Herein, cold welding mechanisms of Cu₅₀Zr₅₀ nanoporous amorphous alloys (NPAAs) are investigated by molecular dynamics simulations, along with the mechanical properties of the welded products. Effects of welding conditions and microstructural parameters are considered. Our results demonstrate that the welded joint has superior mechanical properties. The ultimate strength of the welded NPAAs can be as high as 94–99% that of the original NPAAs but 62–75% for the yield strength and elastic modulus. Voronoi analysis declares that the changes in atomic clusters of NPAAs caused by cold welding are mild. The welding conditions do not have remarkable influences on the mechanical responses of the welded structure. The NPAAs with smaller ligament sizes are more suitable for cold welding, benefiting from the size effect of amorphous alloys. We also successfully use cold welding to fabricate gradient NPAAs and repair fractured NPAAs. It is found that the ultimate tensile strength of the NPAAs changes very little with each successful cold welding. After ten fracture-welding cycles, the ultimate strength of the as-welded specimen is slightly lower than that of the raw materials.