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.