The solidification characterization of Mg–xZn–0.5Zr (x = 0, 1, 3, 4, 5 wt%) alloys has been extensively investigated through thermal analysis, microstructure characterization and thermodynamic calculations. The impact of Zn content on the grain growth restriction, dendrite coherency and thus the final grain size has been investigated and discussed. Increasing Zn content, the grain size of Mg–xZn–0.5Zr alloy was firstly refined and then coarsened with the finest grain size of ~ 50 μm for the Mg–3Zn–0.5Zr (ZK31) alloy. Significant effects of the grain size on the mechanical properties were observed in the investigated alloys. The combination of growth restriction factor theory and dendrite coherency point provides a reasonable explanation of the grain size results. It helps to further understand the mechanisms of grain refinement and grain coarsening related to solute content, providing reference for alloy design and grain size prediction.

Mg – x Zn–0.5Zr（x  = 0、1、3、4、5 wt％）合金的凝固表征已通过热分析，微观结构表征和热力学计算得到了广泛研究。研究和讨论了锌含量对晶粒生长限制，枝晶连贯性以及最终晶粒尺寸的影响。锌含量增加，Mg– x的晶粒尺寸对于Mg-3Zn-0.5Zr（ZK31）合金，首先对Zn-0.5Zr合金进行精炼，然后进行粗化，其最大晶粒尺寸约为50μm。在研究的合金中观察到晶粒尺寸对机械性能的显着影响。生长限制因子理论和枝晶相干点的结合为晶粒尺寸结果提供了合理的解释。它有助于进一步了解与溶质含量有关的晶粒细化和晶粒粗化的机理，为合金设计和晶粒尺寸预测提供参考。