High-rate squeezing process of bulk metallic glasses

Strain Rate and Temperature Effects on Tensile Properties of Polycrystalline Cu6Sn5 by Molecular Dynamic Simulation

Intermetallic compounds (IMCs) are essential in the soldering of electronic products and are composed mainly of Cu6Sn5 and Cu3Sn. They must maintain reliable mechanical and electrical connections. As they are usually only a few microns thick, and it is difficult to study their mechanical properties by traditional methods. In this study, a 100 Å × 100 Å × 100 Å polycrystal with 10 grains was created by Atomsk through Voronoi tessellation based on a Cu6Sn5 unit cell. The effects of the temperature and strain rate on the tensile properties of the polycrystalline Cu6Sn5 were analyzed based on MEAM potential function using a molecular dynamics (MD) method. The results show that Young’s modulus and ultimate tensile strength (UTS) of the polycrystalline Cu6Sn5 decrease approximately linearly with an increase in temperature. At high strain rates (0.001–100 ps−1), Young’s modulus and UTS of the Cu6Sn5 are logarithmic with respect to the strain rate, and both increase with an increase in strain rate. In addition, at low strain rates (0.00001–0.0005 ps−1), the UTS has a quadratic increase as the strain rate increases.

A nanoscale study of the negative strain rate dependency of the strength of metallic glasses by molecular dynamics simulations

Compressive strength and deformation characteristics of a metallic glassy alloy related to strain rate are studied by molecular dynamics simulations. The negative strain rate dependency of strength is presented, i.e., compressive strength decreases with the increase of strain rate, which is well in line with the experimental results. The negative strain rate dependency of strength is explained from two aspects at the atomic scale of free volume and potential energy. Compressive strength is related to the free volume formation in a shear band, which is different from that in a metallic glass matrix. In addition, the relation of potential energy and temperature is also investigated, which indicates that thermal softening also plays an important role in the negative strain rate dependency of strength. The thermal-mechanical coupling mechanisms causing the negative strain rate dependency of the strength of the metallic glassy alloy are clarified. It is significant to explore the intrinsic deformation characteristics of the metallic glassy alloy under a high rate loading.