Interfacial reaction, amorphization transition, and associated elastic instability studied by molecular dynamics simulations in the Ni-Ta system

Abstract

By means of constant-pressure molecular dynamics simulation, the crystal-to-amorphous transition in the Ni-Ta system is investigated in detail. An n-body potential is first developed for the system in the framework of an embedded-atom method and is then applied to simulate the crystal-to-amorphous transition at the interfaces in a Ni-Ta sandwich model. It is found that the amorphous layers initiate to grow at the interfacial areas and extend to Ni and Ta lattices by crossing-interface atomic migration. Simulation is also performed on the models consisting of Ni- and Ta-based solid solutions and it reveals that the crystal-to-amorphous transitions take place at two respective critical solute concentrations, from which the composition range favoring metallic glass formation is thus determined. In addition to a structural change, a dramatic softening in shear elastic moduli is in association with the glass transition, which is therefore considered to be triggered by a mechanical instability. A brief discussion is also presented to compare the simulation results with those proposed criteria for solid-state amorphization.