Effect of Sn Addition on the Precipitation Behavior in AZ91 Magnesium Alloy

The effect of Sn (1, 3 and 5 mass%) addition on the precipitation behavior of AZ91 alloy has been investigated in the present study. The addition of Sn is effective in suppression of discontinuous precipitation as well as acceleration of continuous precipitation. The Mg2Sn particles at the grain boundary effectively reduce the nucleation sites for discontinuous beta precipitates, and slow down the movement of the grain boundary. The addition of Sn remarkably enhances the aging response of AZ91. The hardness increases steeply with the start of the aging treatment, resulting in significantly higher peak hardness within shorter aging time. The addition of Sn enhances the aging response by solid solution hardening effect as well as by co-precipitation of Mg17Al12 and Mg2Sn in the alpha-Mg matrix.