Effect of Ca on microstructure and tensile strength of AZ91 alloys

The AZ91 alloy containing calcium has been prepared under the protection of a mixed gas atmosphere of SF6(10%) and CO2(90%) by using commercial stock, and their microstructure and mechanical properties also have been investigated. The experimental results show that a small amount addition of calcium to AZ91 alloy can result in an obvious increase of tensile strength at both ambient and elevated temperatures. Microstructural observations reveal that the addition of calcium can refine the microstructure and change the morphology of the matrix phase from dendritic to equiaxed. The addition of calcium enhances the thermal stability of β precipitates, and it is considered the most important factor of affecting the creep resistance of the alloys.