Ab initio investigation on preferred orientation at the Al/Al₃(Zr,Y) interface in Al-Zr-Y alloy

The orientation at the interfaces plays a vital role on the morphology of the aging precipitates in Al-Zr-Y composites. Experimental observation found out that the aging precipitates FCC-Al3(Zr,Y) phase does not have the typical "Al3Y core-Al3Zr shell"structure, which is common for most of the Al-Z-RE (rare earth elements) alloys. First-principles calculations were employed in this paper to reveal the orientations at the Al/Al3(Zr,Y) interface for the development of a new heat resistant Al-Zr-Y alloy. Three interface configurations D019-Al3Y(001)/Al(111), L12-Al3Y(111)/Al(111), and L12-Al3Y(001)/Al(001) were proposed for considerations. The calculations revealed that FCC-Al(001)/FCC-Al3Y(001) is the most stable interface. Zr and Y doping led to lower interface energies. In the early stage of growth, Zr doping dominated the interface energies due to the influence of surface energy. With the increase of the substituted elements content at the interface, the work of adhesion has a more significant effect on the interface energies, and the interface was dominated by Y doping. Therefore, the composite shell is finally formed as the FCC-Al3(Zr,Y) phase rather than the typical "Al3RE core-Al3Zr shell"structure. This result provides a guide for further research studies on the interface performance between Al3(Zr,Y) and Al matrix.