Abstract In this work, the role of Al addition in modifying the microstructure and mechanical properties of the Mg-1.0Ca-xAl (x = 0.6, 1.0 wt%; termed as XA10 and XA11, respectively) based alloys has been systematically investigated. Microstructural examination showed that, when the Al content is low, the Al and Ca atoms were inclined to segregate to the dislocation lines in the XA10 sample. As a result, the mobility of dislocation was restrained and the dynamic recovery behavior was hindered, which leads to a low degree of dynamic recrystallization. When the Al content is high, in contrast, no apparent Ca/Al segregations along dislocations have been found in XA11-0 extrusion billet during the whole stages of processing, which results in the enhanced dislocation mobility. Consequently, the recovery of dislocations and dynamic recrystallization rate can be largely enhanced at the earlier stage of extrusion. More importantly, subsequently formed high density Guinier-Preston (G.P.) zones and nano-disk Al2Ca phases in the high-Al content Mg sample can play an effective role in inhibiting the growth of subgrains and dynamically recrystallized (DRXed) grains, which enhance the thermal stability of high density low angular grain boundaries (LAGBs) in the later extrusion stage. The high density nano-disk phases, high volume fraction of DRXed grains, as well as the high density LAGBs in the un-DRXed grains, can together contribute to both high strength and good elongation of the XA11 sample. The findings lead to the controllable Mg-Ca based alloy designing strategy that can improve the strength and ductility simultaneously.

中文翻译：

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添加 Al 对 Mg-1.0 wt% Ca 基合金显微组织和力学性能的影响

摘要 在这项工作中，系统研究了添加 Al 在改变 Mg-1.0Ca-xAl（x = 0.6, 1.0 wt%；分别称为 XA10 和 XA11）基合金的组织和机械性能方面的作用。显微组织检查表明，当铝含量较低时，铝和钙原子倾向于偏析到 XA10 样品中的位错线。结果，位错的迁移受到抑制，动态恢复行为受到阻碍，导致动态再结晶程度较低。相反，当Al含量高时，XA11-0挤压坯在整个加工阶段没有发现沿位错的明显Ca/Al偏析，导致位错迁移率增强。最后，位错的恢复和动态再结晶速率在挤压的早期可以大大提高。更重要的是，随后在高Al含量Mg样品中形成的高密度Guinier-Preston（GP）区和纳米盘Al2Ca相可以有效抑制亚晶粒和动态再结晶（DRXed）晶粒的生长，从而增强挤压后期高密度低角晶界 (LAGB) 的热稳定性。高密度纳米盘相、DRXed 晶粒的高体积分数以及未 DRX 晶粒中的高密度 LAGB 共同有助于 XA11 样品的高强度和良好的伸长率。这些发现导致了可控的镁钙基合金设计策略，可以同时提高强度和延展性。