Structure evolution, thermal stability and diffusion behaviors in Cu-Ta amorphous alloys studied by ab initio molecular dynamics simulation

Abstract Cu-based materials consisting of immiscible elements have been paid much attention due to their high strength and high conductivity. The amorphous layers between Cu and strengthening phases formed through severe deformation play a crucial role in the improvement of properties. In this study, structure evolution, thermal stability of Cu 100−x Ta x (x = 10, 30, 50, and 70 at%) amorphous alloys and diffusion behaviors of alloys were studied by ab initio molecular dynamics (AIMD) simulations. With the Ta concentration rising, the number increase of Cu-Ta and Ta-Ta bonds results in the increase of volume for Cu-Ta amorphous alloys. Ta tends to be soluble in Cu clusters for Cu-rich amorphous alloys while Cu tends to be soluble in Ta clusters for relatively Ta-rich ones. According to energy evolution, the thermal stability of amorphous alloys decreases and then increases as Ta concentration increases. Compared with Cu element, the diffusion of Ta is significantly limited. The differences in thermal stability between Cu-Ta amorphous alloys and diffusion of Cu and Ta elements result in the formation of Ta-rich amorphous alloys after non-equilibrium fabricating. These results could substantively contribute to the development of Cu-based materials and understanding of the interface characteristic of immiscible alloys.