Grain refinement and enhanced mechanical properties of Mg–2Zn-xCa alloys (with a wide range of calcium contents from 0 to 5 wt%) were studied in both as-cast and extruded conditions. It was revealed that Ca addition can effectively refine the grain size of the ingots based on the growth restriction factor (GRF) mechanism, where at high Ca additions, the dendritic microstructure was obtained. By increasing the amount of Ca, the binary Mg–Zn phase was replaced by the Ca₂Mg₆Zn₃ phase and at high Ca contents, the Mg₂Ca phase appeared in the microstructure. The tensile properties were enhanced at low Ca additions (up to 0.3 wt%) due to the grain refinement but they were deteriorated at higher Ca additions due to the formation of grain boundary second phases. Accordingly, the ultimate tensile strength (UTS) of 228 MPa and total elongation of 20% was obtained for the as-cast Mg–2Zn-0.3Ca (ZX20) alloy. During hot extrusion, significant grain refinement and the fracturing and dispersion of second phase particles were observed. The grain size refinement beyond ∼1 wt% Ca was negligible and extrusion defects were observed at higher Ca contents, and hence, the best combination of mechanical properties was obtained for the Mg–2Zn–1Ca (ZX21) alloy with UTS of 283 MPa and elongation to failure of 29%. This alloy showed a desirable work-hardening behavior and the best combination of tensile properties, where the product of tensile strength and total elongation reached as high as ∼8000 MPa%. Finally, the yield stress of the alloys was correlated to the average grain size via the classical Hall-Petch plot with a slope of 228.5 MPa μm^−0.5.

在铸造和挤压条件下，研究了Mg-2Zn-xCa合金（钙含量范围从0到5 wt％）的晶粒细化和增强的机械性能。结果表明，添加钙可以根据生长限制因子（GRF）机理有效地改善铸锭的晶粒尺寸，在高添加钙的情况下，可以获得枝晶组织。通过增加Ca的含量，二元Mg-Zn相被Ca ₂ Mg ₆ Zn ₃相代替，并且在高Ca含量时，Mg ₂Ca相出现在微观结构中。由于晶粒细化，在低钙添加量（至多0.3 wt％）下，拉伸性能得到增强，但由于晶界第二相的形成，在高钙添加量下，拉伸性能下降。因此，铸态的Mg-2Zn-0.3Ca（ZX20）合金的极限拉伸强度（UTS）为228 MPa，总伸长率为20％。在热挤压过程中，观察到明显的晶粒细化以及第二相颗粒的破裂和分散。Ca含量超过〜1 wt％时晶粒细化可忽略不计，并且在较高的Ca含量下观察到挤出缺陷，因此，对于UTS为283 MPa的Mg-2Zn-1Ca（ZX21）合金，可以获得最佳的力学性能组合断裂伸长率为29％。该合金表现出理想的加工硬化性能和拉伸性能的最佳组合，其中拉伸强度和总伸长率的乘积高达〜8000 MPa％。最后，合金的屈服应力通过经典的Hall-Petch图与228.5 MPaμm的斜率关联到平均晶粒尺寸^−0.5。