Highly choreographed atomic motion and mechanism of interface amorphization

Atomic mechanisms are investigated for solid-state amorphization using a diffusion couple made of metallic glass Cu46Zr54 and single-crystal Al. Our extensive molecular dynamics simulation reveals that amorphization occurs in the crystalline metal at the interface via a series of highly coordinated and complex atomic motion involving all elements in both the glassy phase and the crystal. Chemical mixing occurs through asymmetric interdiffusion of more Cu and Zr in the glass phase into the crystal than Al into the glass. The faster diffuser Cu is found to hop into the Al lattice position, whereas Zr trails behind and provides a supporting role by pulling Al atoms off the lattice position. This highly choreographed atomic motion creates cooperative diffusion and mixing at the interface region that causes large lattice distortion and eventually leads to the collapse of the crystalline phase when critical amounts of Cu and Zr are fused into Al. Extension of this atomic mechanism to a more general setting is discussed, particularly in the context of elastic instability.