Effect of grain refinement with boron on the microstructure and mechanical properties of Al-30Zn alloy

In this study, one binary aluminum-zinc (Al-30Zn) alloy and nine ternary aluminum-zinc-boron [Al-30Zn-(0.01-2) B] alloys were produced by permanent mold casting method. Structural properties of the produced alloys were determined by light and electron microscopy. hardness and mechanical properties were determined by universal testing methods. It was observed that the dendrite and grain size decreased, but the number of dendrites increased with boron addition to Zn-30Al alloy. Microstnicture of the binary Al-30Zn alloy was composed of alpha dendrites and the eta phase surrounding these dendrites. With increasing boron content. the hardness of Zn-30Al-(0-2)B alloys increased continuously, but compressive strength decreased. Their tensile strength increased with increasing boron additions, but above 0.06% B the trend reversed. The changes in the mechanical properties of the boron addition to Zn-30Al alloy are explained based on the changes in the microstructure.