Investigations of the properties of Mg–4Al–2Sn–1Ca–xCe alloys

The microstructures and mechanical properties of Mg–4Al–2Sn–1Ca alloy with Ce addition have been investigated for the purpose of the development of heat resistant magnesium alloys for automotive powertrain application. The main phases of as-cast Mg–4Al–2Sn–1Ca alloy were Mg17Al12, Mg2Sn and CaMgSn phases, and Al11Ce3 phase were found in the alloys with Ce addition. And, Mg17Al12 phases were decreased with addition of Ce. The addition of Ce improved the mechanical properties of Mg–4Al–2Sn–1Ca alloy. The strengthening mechanism of Ce-containing Mg–4Al–2Sn–1Ca alloys was mainly attributed to the refinement of CaMgSn phase. The deformation mechanism was observed the twin deformation. Fractographic analysis demonstrated that dimple and cleavage facet were dominant mechanisms of these alloys tested at room and elevated temperature. The portion of dimples was increased with the trace addition of Ce at the room and elevated temperatures.

Research highlights1. With the addition of Ce element, Al11Ce3 phase was formed in the as-cast alloys and its amount increased with increasing addition of Ce. Meanwhile the morphology of CaMgSn was refined to granular phases. 2. The highest tensile properties were obtained in the Mg–4Al–2Sn–1Ca–1.0Ce alloy. The UTS, YS and elongation at room temperature were 194, 95 MPa and 11.4%, respectively. Cracks were initiated preferentially in the CaMgSn phases at room temperature. However, cracks propagation was mainly observed along the dendritic and grain boundaries at elevated temperature. The deformation mechanism was observed a twin deformation.