Effect of Mn on grain size of high-purity Mg-3Al alloys

The effect of Mn on the grain size of high-purity Mg-3Al (mass fraction, %) alloys was investigated. The results show that the grain sizes of high-purity Mg-3Al alloys changes little when the Mn content is lower than 0.21% (mass fraction), while the grains are coarsened when Mn content is higher than 0.21%. The effect of Mn is relative to the heterogeneous nucleation of carbon-containing cores in the melt. When Mn content is low and dissolves into the melt, the nucleating potent of carbon-containing cores would not be influenced basically. But when Mn content in the melts is close to or higher than its solubility, the nucleating potent of the cores is decreased by Mn addition, and the grains are coarsened.