Aiming to investigate the role and mechanism of nano MgO on the hot compressive deformation behavior of Mg alloys, the Mg-3Zn-0.2Ca alloy (MZC, in wt%) and the 0.2MgO/Mg-3Zn-0.2Ca alloy (MZCM, in wt%) were investigated systematically in the temperature range of 523–673 K and the strain rate range of 0.001–1 s⁻¹. MZCM shows finer grains and second phase because of the refinement effects of added MgO. Flow behavior analysis shows that the addition of nano MgO promotes the dynamic recrystallization (DRX) of MZC. The flow stress of MZCM is lower than that of MZC during deformation at 523–623 K but exhibits a reverse trend at 673 K and 0.1–1 s⁻¹. The constitutive analysis indicates that dislocation climb is the dominant deformation mechanism for MZC and MZCM. The addition of nano MgO particles decreases the stress sensitivity and deformation resistance for thermal deformation and improves the plasticity of the MZC. Besides, according to the processing map constructed at strains of 0.7 and corresponding microstructure evolution, MZCM exhibits higher power dissipation efficiency and smaller instability regions than MZC, and the optimum hot working condition for MZCM was determined to be at 623–653 K and 0.01–0.001 s⁻¹.

中文翻译：

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纳米MgO对Mg-Zn-Ca合金热压缩变形行为的作用和机理的洞察

目的研究纳米MgO对Mg-3Zn-0.2Ca合金（MZC，wt％）和0.2MgO / Mg-3Zn-0.2Ca合金（MZCM，在523–673 K的温度范围和0.001–1 s ^-1的应变速率范围内，进行了系统的研究。由于添加的MgO的细化效果，MZCM显示出更细的晶粒和第二相。流动行为分析表明，纳米MgO的添加促进了MZC的动态重结晶（DRX）。在523–623 K变形期间，MZCM的流动应力低于MZC，但在673 K和0.1–1 s ^-1时呈现出相反的趋势。。本构分析表明，位错爬升是MZC和MZCM的主要变形机制。纳米MgO颗粒的添加降低了热变形的应力敏感性和抗变形性，并改善了MZC的可塑性。此外，根据在0.7应变下构造的加工图和相应的微结构演变，MZCM具有比MZC更高的功耗效率和更小的不稳定性区域，并且确定MZCM的最佳热加工条件为623-653 K和0.01-K。 0.001 s ^-1。