Evolution of as-cast and heat-treated microstructure of a commercial bearing alloy

The present study involves the microstructural changes of a zinc-aluminium alloy (ZA27) by nickel, a high melting point element, and the commercial master alloys, Al-5Ti-1B and Al-5Sr. The evolution of as-cast microstructure and the effect of heat treatment on the as-cast microstructure and hardness have been presented in detail. The addition of Ti, B and Sr as master alloys results in significant refinement in the dendrite structure of the ZA27 alloy. The addition of Ni to ZA27-based alloy results in the formation of Ni-aluminides as rod as well as blocky-shaped particles. High amount of Ni (2 wt.%) refines the dendritic structure significantly.