The effect of charcoal addition on the grain refinement and ageing response of magnesium alloy AZ91

This article focuses on the grain refinement and ageing behavior of AZ91 Mg alloy inoculated with charcoal. The results show addition of 0.2 wt% charcoal has made considerable grain refinement in the AZ91 Mg alloy by reducing the grain size from 100 to 30 μm. Such fine grain structure achieved through addition of charcoal suggests that the Al4C3 and Al2MgC2 particles formed in the melt have acted as efficient nucleating sites during solidification of α-Mg. Further, this study reveals that the ageing kinetics of AZ91 is improved by the addition of charcoal and the time to reach peak hardness comes down from 16 h in the base alloy to 10 h with 0.2 wt% charcoal added AZ91 alloy. In addition, the tensile properties are also found to increase with charcoal addition, which is mainly attributed to the grain refinement.

► Minor addition of charcoal effectively refines the grains in AZ91 Mg alloy.
► Age hardening is accelerated in charcoal added AZ91 alloy.
► The tensile properties are also found to increase with charcoal addition, which is mainly attributed to the grain refinement.