EBSD Study of ZnAl25 Alloy Inoculated with ZnTi4 Master Alloy

The microstructure of cast Zn-25wt%Al alloy inoculated by addition of a Zn-4wt%Ti master alloy (ZnTi4) has been studied using scanning electron microscopy and electron back-scatter diffraction (EBSD). It is found that Ti(Al,Zn)3 particles act as nucleation centres for grains of the primary solid solution of Zn in Al (α' phase). The Ti(Al,Zn)3 particles evolve in melt from the TiZn3 particles in the ZnTi4 master alloy. EBSD shows that α' phase dendrites are in the same crystallographic orientation as the Ti(Al,Zn)3 particles on which they nucleate. It is also found that some of the Ti(Al,Zn)3 particles do not have any well-defined crystallographic orientation relationship with the α' phase. These particles were probably pushed and then engulfed by growing α' grains which had already nucleated on other particles.