Despite the industrial significance of grain size for enhancing mechanical properties and formability, the in-depth deformation mechanisms at elevated temperature are still unclear. To investigate the functions of grain size on hot workability and deformation mechanisms, three groups of Mg-1.2Zn-0.2Y alloy specimens with different grain sizes were hot compressed and then studied by combining constitutive model, processing map and microstructural observations. The results showed that the enhanced hot workability accompanying low deformation activation energy and small instability regime was obtained with refined grain size. During hot deformation, the decreased grain size in Mg-1.2Zn-0.2Y alloy mainly improved the plastic deformation homogeneity, especially for the weakened local straining around grain boundaries. As a result, the dynamic recrystallization nucleation and texture development at lower strain level were influenced by the initial grain size. At higher strain magnitude, the growth and coarsening of dynamic recrystallized grains would further release strain localization and improve hot workability, while the texture was less impacted. Further, unlike the primary basal slip and deformation twinning in the specimen with coarse grain at low temperature, non-basal slips of dislocations were initiated with less deformation twins in the specimens with refined grain size.

尽管晶粒尺寸对于提高机械性能和可成形性具有工业意义，但高温下的深度变形机制仍不清楚。为了研究晶粒尺寸对热加工性和变形机制的影响，对三组不同晶粒尺寸的 Mg-1.2Zn-0.2Y 合金试样进行热压，然后结合本构模型、加工图和显微组织观察对其进行研究。结果表明，随着晶粒尺寸的细化，获得了伴随低变形激活能和小的失稳区的增强的热加工性。在热变形过程中，Mg-1.2Zn-0.2Y 合金晶粒尺寸的减小主要改善了塑性变形的均匀性，尤其是晶界周围的局部应变减弱。因此，较低应变水平下的动态再结晶形核和织构发展受初始晶粒尺寸的影响。在较高的应变值下，动态再结晶晶粒的生长和粗化将进一步释放应变局部化并改善热加工性，同时织构受到的影响较小。此外，与低温下粗晶试样中的初级基底滑移和变形孪晶不同，细晶粒试样中的非基底滑移和变形孪晶较少。而质地受到的影响较小。此外，与低温下粗晶试样中的初级基底滑移和变形孪晶不同，细晶粒试样中的非基底滑移和变形孪晶较少。而质地受到的影响较小。此外，与低温下粗晶试样中的初级基底滑移和变形孪晶不同，细晶粒试样中的非基底滑移和变形孪晶较少。