用砂型铸造了不同Ca含量的Mg-5Al-0.4Zn-0.2Mn-Sr-Ti-xCa合金. 当x为0.37, 0.70, 0.93, 1.69时，合金相组成为α-Mg，(α+Al2Ca)共晶和Mg17Al12. 当x=2.93时，相组成为α-Mg和(α+(Mg, Al)2Ca)共晶. 随着x增加，合金的室温力学性能(σb和δ)呈下降趋势，但合金在200 ℃下的强度先升高，后又降低. 高温延伸率随x增加而下降. 合金200 ℃下的屈服强度σ0.2, 200 ℃随x的增大而稳步增加. 组织的热稳定性分析表明，Ca溶入 Mg17Al12相使得其自身的耐热性提高. 晶界上耐高温相Al2Ca或(Mg, Al)2Ca的形成，在高温下对晶界具有钉扎作用，并降低了晶界处的溶质扩散速度，使晶界强度提高. TEM分析表明, 含Ca合金在200 ℃拉伸时，(10-10)棱柱面和(-1-121)角锥面上的位错参与了滑移. 不同滑移系的位错滑移到晶界时，受到晶界上Al2Ca相阻挡而发生位错塞积.
In the sand-casting magnesium alloys Mg-5Al-0.4Zn-0.2Mn-Sr-Ti-xCa , existed α-Mg, (α + Al2Ca) eutectic and Mg17Al12 when x=0.37, 0.70, 0.93, 1.69, or α-Mg and (α+(Mg, Al)2Ca) eutectic when x=2.93. With increasing x, the room temperature mechanical properties (σb, δ) of the alloys decreased, meanwhile the strength at 200 ℃ increased first and then decreased slightly, and the elongation decreased rapidly. The yield strength at 200 ℃ (σ0.2, 200 ℃) of the alloys was greatly improved with the increase of x value. DSC analysis proved that the thermal stability of Mg17Al12 phase was improved by dissolution of Ca. The grain boundary strength at 200 ℃ was improved through the formation of the Al2Ca or (Mg, Al)2Ca phases at the grain boundary. TEM analysis shows that the dislocations slip not only at the basal slip plane (0001), but also at the (10-10) prismatic slip plane and (-1-121) pyramidal slip plane at 200 ℃. The dislocation can be piled up by Al2Ca phases at the grain boundary resulting in the higher yield strength of the alloy containing Ca than those without Ca at 200 ℃.
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