Molecular dynamics simulation of diffusion for Ni–Zr interface

The molecular dynamics simulation has been performed to study the effects of temperature on interdiffusion of Ni–Zr system. The simulated results indicate that the thickness of Ni/Zr diffusion layer increased with increasing diffusion time, and interdiffusion results in disordered or amorphization in the diffusion zone. During the diffusion process, Ni atoms diffuse crossing the interface more easily and deeply into Zr side than Zr atoms into Ni side. The activation energies of Ni and Zr are 1.25 and 1.28 eV for Ni(100)//Zr(0001) interface, 1.33 and 1.42 eV for Ni(110)//Zr(0001) interface at the temperature range of 950–1100 K, respectively. The microscopic diffusion mechanisms for Ni atoms in Zr lattice have been studied, and the results show that the most possible diffusion mechanism is the interstitial hopping mechanism, while for Zr diffusing in Ni, the vacancy diffusion mechanism is favored. The interdiffusion for case of Ni(110)//Zr(0001) interface is more easy than that of Ni(100)//Zr(0001) interface due to the lower surface energy for the former. In the diffusion zone of Ni–Zr, some typical clusters have been identified, which are similar to those extracted from the Ni–Zr intermetallic compounds, and which are generally consistent with the experimental observations in diffusion couples.