Exploring the local structure of molten Al-Zr-Y(Si) alloys using ab initio molecular dynamics

Accelerating the diffusion rate of Zr in aluminum and suppressing Zr segregation during solidification are crucial for enhancing the heat resistance of Al-Zr alloys. In this study, ab initio molecular dynamics simulations were employed to investigate the local structure of molten Al-Zr-Y(Si) alloys and the morphology of the liquid/substrate interface. By examining the atomic interactions, the mechanism by which Si addition improves Zr segregation during solidification and accelerates Zr diffusion was revealed. The results indicate that the interaction between Si and Zr is significantly stronger than that with other alloying elements such as Al, Y, and Zr itself. The introduction of Si had a discernible detrimental effect on Zr-Zr bonds, as Zr atoms exhibited a preference for bonding with Si atoms, consequently promoting cluster formation. This phenomenon resulted in the fragmentation of large Zr clusters into smaller ones. Moreover, the inclusion of Si atoms notably augmented the diffusion coefficient of Zr atoms within the Al-Zr-Y alloy. Analysis of the solid-liquid interface unveiled a noteworthy dragging effect, where Si atoms prominently pulled Zr atoms into the liquid phase at the interface's forefront.