Effects of Composition on Atomic Structure, Diffusivity, and Viscosity of Liquid Al-Zr Alloys

The diffusion coefficients and viscosity of four Al1-x Zr (x) (x = 0.4, 0.5. 0.6, and 0.67) alloys are predicted by ab initio molecular dynamic simulations via the Einstein and Darken equations. It is observed that the addition of Zr to Al reduces the self-diffusion coefficient of Al drastically, whereas the addition of Al to Zr has little effect on the self-diffusion coefficient of Zr. The interdiffusion coefficient and viscosity are predicted with both being close to those of pure Al extrapolated to high temperatures. Based on the analysis of atomic structures, the observations are attributed to clustering in liquid so that the migration of Al and Zr are correlated strongly and viscous flow is affected by Al-Al bonding between clusters.