Microstructures and High-Temperature Properties of Sm-Modified Mg-4Al-4RE Alloy

The effect of Sm on the microstructure and tensile properties of Mg-4Al-4 (La, Ce) alloy was studied. The Mg-4Al-4 (La, Ce) alloy was mainly composed of α-Mg and Al11(La, Ce)3. With the addition of Sm, a new phase of Al2(La, Ce, Sm) was revealed in the alloy. The results showed that at room temperature (RT), after Sm addition, the ultimate tensile stress and the elongation decreased, while the yield stress increased slightly; the elongation increased with the Sm addition and the yield stress was basically the same, but the ultimate tensile stress decreased at an elevated temperature of 150 °C. The change in the mechanical properties of the alloy was mainly related to the change in microstructure and phase. With the increase in Sm content, the volume fraction of Al2(La, Ce, Sm) phase increased and the Al11(La, Ce)3 eutectic volume fraction decreased significantly, which led to a change in the mechanical properties of the alloy. The 1 wt.%Sm-addition alloy exhibited greater elongation than the Sm-free alloys.