Tensile creep resistance of a high-pressure die-cast Mg–4Al–4RE–0.3Mn (AE44) alloy was significantly deteriorated after substituting part RE with Ca. According to traditional power-law creep theories, the stress exponent and the activation energy were revealed as 6 and 217 kJ/mol, which indicate inconsistent mechanisms of dislocation climb and dislocation cross-slip, respectively. Then, transmission electron microscopy (TEM) observations illustrate that dislocation substructures developed during creep are variational with precipitate characters in α-Mg grains, creep stress levels and creep temperatures. Therefore, both stress exponent and activation energy obtained from traditional power-law creep theories are meaningless for the AE44 alloy with part RE substituted by Ca. Finally, the shrink of C36 phase lattice, the precipitation of Al₂Ca precipitates and the denuded zones were observed in the crept samples, and all of them are responsible for the deterioration in creep resistance of the AEX422 alloy. Also, this paper provides insight into alloy design principles for further development of creep-resistance Mg–Al–RE based alloys.

用Ca代替RE部分后，高压压铸Mg-4Al-4RE-0.3Mn（AE44）合金的抗拉蠕变性显着降低。根据传统的幂律蠕变理论，应力指数和活化能分别为6 kk / mol和217 kJ / mol，表明位错爬升和位错错滑的机理不一致。然后，透射电子显微镜（TEM）观察表明，蠕变过程中形成的位错亚结构随着α-Mg晶粒中的析出特征，蠕变应力水平和蠕变温度而变化。因此，从传统的幂律蠕变理论获得的应力指数和活化能对于用RE代替Ca的AE44合金都是没有意义的。最后，C36相晶格收缩，Al析出在蠕变样品中观察到_2个Ca析出物和剥蚀区，它们都是AEX422合金抗蠕变性能下降的原因。此外，本文还为进一步开发抗蠕变Mg-Al-RE基合金提供了合金设计原理的见解。