Grain refining mechanisms in Mg–Al alloys with Al4C3 microparticles

Experiments were conducted to examine the grain refining mechanisms in AM60B, pure Mg, and Mg–6%Al with the addition of 5 wt% aluminum carbide (Al4C3). Grain refinement was observed in the AM60B and pure Mg with the addition of 5 wt% Al4C3 via two different mechanisms respectively, i.e. duplex nucleation hypothesis (Al4C3 → Al8Mn5 → α-Mg) in AM60B and Al4C3 nuclei hypothesis (Al4C3 → α-Mg) in pure Mg. It is suggested that Mn is required to facilitate significant grain refinement in Mg–Al alloys containing ≥6% Al due to the segregating behavior of Al4C3 particles to the solid–liquid (S–L) interface. Mechanical properties (yield strength, tensile strength, ductility, and microhardness) were enhanced by the addition of Al4C3 to AM60B alloy.