Effect of mechanical vibrations on grain refinement of AZ91 Mg alloy

AZ91 Mg alloys are extensively being consumed in the automotive, aerospace, electrical and communication industries. The large freezing range of this alloy allows the formation of coarse-grained structures. To overcome this problem magnesium alloys are, therefore, treated for grain refinement. In this study, mechanical vibrations in the frequency range from 0 to 25 Hz at a constant amplitude of 2 mm were imposed during solidification of Mg–9Al–1Zn alloy. Optimum results were obtained at 15 Hz. It was observed that mechanical vibration during solidification had a good refining effect on the grain morphology of the alloy. The alloy was characterized by optical metallography, scanning electron microscopy and mechanical properties such as hardness and tensile strength. It was observed that, by applying vibrations to the melt, a uniform distribution of the fine grains of the primary α-Mg phase was achieved and the properties were enhanced.