The effect of Bi addition on the microstructure and tensile properties of cast Al-15%Mg2Si composite

In the current research, the influence of different concentrations of Bi (0.01-0.3 wt.%) on the microstructure and tensile properties of Al-15 wt.% Mg2Si in-situ metal matrix composite (MMC) has been investigated. It was found that 0.03 wt.% Bi changes the primary Mg2Si shape from large to irregular or dendritic to polyhedral shape. The average particle size of Mg2Si also decreases from 65 m to 20 m by adding 0.03% Bi. Microstructural observations by scanning electron microscope (SEM) also depicted that the morphology of the eutectic Mg2Si phase alters from flake-like to fine fiber or dot like. Further investigations on tensile testing revealed that the optimum amount of Bi level is 0.03% for improving both ultimate tensile test (UTS) and elongation values.