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

By means of constant-pressure molecular dynamics simulation, the crystal-to -amorphous transition in the Ni-Ta system is investigated in detail. An ii- body potential is first developed for the system in the framework of an emb edded-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 th e amorphous layers initiate to grow at the interfacial areas and extend to Ni and Ta lattices by crossing-interface atomic migration. Simulation is al so performed on the models consisting of Ni- and Ta-based solid solutions a nd it reveals that the crystal-to-amorphous transitions take place at two r espective critical salute concentrations, from which the composition range favoring; metallic glass formation is thus determined. In addition to a str uctural change, a dramatic softening in shear elastic moduli is in associat ion with the glass transition, which is therefore considered to be triggere d by a mechanical instability. A brief discussion is also presented to comp are the simulation results with those proposed criteria for solid-state amo rphization.