Effect of Bi Addition on Microstructures and Mechanical Properties of AZ80 Magnesium Alloy

The effects of Bi addition on the microstructures and mechanical properties of as-cast AZ80 alloy were investigated. The results show that with the addition of Bi, the coarse eutectic phases are refined and become discontinuous; some flaky and granular Mg(3)Bi(2) phases with a hexagonal structure of D5(2) are observed along the grain boundaries and between dendrites. The tensile strength and elongation increase first, and then decrease with increasing Bi content. AZ80-0.5% Bi alloy has optimum combination mechanical properties. When the content of Bi is above 1.0% ( mass fraction), the amount of flaky Mg(3)Bi(2) phase increases markedly, which splits the matrix and deteriorates the tensile strength and elongation.