The tensile creep anisotropy of a dilute-alloyed Mg-0.3wt%Ca sheet is investigated along the rolling direction (RD) and normal direction (ND). Strong creep anisotropy is shown between the RD and ND, owing to the easy twinning and the Ca-segregation along twin boundaries during creep loading along the ND. To weaken the creep anisotropy, hot-compression parallel to the RD-ND plane is performed and the continuous dynamic recrystallization mechanism induces a bimodal microstructure with the coexistence of unrecrystallized and recrystallized grains. The creep anisotropy is successfully weakened after hot-compression, and the creep resistance is also significantly enhanced along both loading directions. With the assistance of microstructural characterization, the weakened creep anisotropy is ascribed to the dislocation arrays in the interiors of recrystallized grains and the Ca-segregation along the boundaries of recrystallized grains. Compared to commercial Mg alloys with poor creep property and rare-earth alloyed Mg with high price, good creep performance and low production cost can be synchronously realized in the hot-compressed Mg-0.3wt%Ca alloy. Thus, this work proposes a new perspective for producing creep-resistant Mg alloys.

In this study, the tensile creep behavior of a hot-rolled Mg-4Y-3.5Nd alloy subjected to different prior thermo-mechanical treatments was investigated at 220 ℃. Five groups of samples were prepared using different combinations of the solid solution (S), aging treatment at 220 ℃ for 30 h (A), and hot compression at 490 ℃ to a true strain of 0.25 (C). The abbreviations for the samples are S, SA, SC, SAC, and SCA. Upon examining the yield strength and creep resistance, it was found that creep resistance could not be directly predicted by the yield strength. The stability of the deformation bands (DBs) induced by prior thermo-mechanical treatment plays an important role in determining the creep resistance. The dislocation of the DBs and demonstrated the best creep resistance in the SAC sample, which were prepared using a solid solution, aging treatment, and subsequent hot compression. However, despite the highest yield strength, frequent dislocation motions destroyed the stability of the DBs and deteriorated the creep resistance of the SCA sample, which were prepared using a solid solution, hot compression, and subsequent aging treatment. Among the thermo-mechanical treatments used in this study, the application of aging treatment was important to obtain the resultant creep resistance. When the aging treatment was performed prior to hot compression, the creep resistance could be further enhanced based only on hot compression. Accordingly, the sequence from the strongest to the weakest creep resistance was SAC > SC > S > SCA > SA.