Abstract Microstructure and mechanical properties evolution of as-cast Mg-Y-Zn alloys have been systematically investigated with various phase types via adjusting Y/Zn ratio. The results show that the investigated alloys have typical α-Mg dendritic microstructure with different intermetallic compounds including I phase, I + W phases, W phase, LPSO + W phases and LPSO phase. Phase evolution in Mg-Y-Zn alloys is analyzed in detail combining microstructure observations and differential scanning calorimetry results. Strengthening effects of mechanical properties with five different compositions indicate that the second phase strengthening is the main strengthening mechanism, and that the contribution follows the order of W > I + W > LPSO + W > I > LPSO. Based on transmission electron microscopy analysis, the lamellar W phase effectively hinders dislocation movement compared to other phases, and alloys with W phase exhibit high strength. LPSO phase shows fracture and kink bands during tension and compression, respectively, which leads to evident yield asymmetry (>1.1) in alloys containing LPSO. Other alloys with I or W phase have a yield anisotropy around 1.0. The tensile property of Mg-Y-Zn alloys is enough for mechanical design.

中文翻译：

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Mg-Y-Zn合金的力学性能和屈服不对称性：第二相的竞争行为

摘要 通过调整 Y/Zn 比，系统研究了不同相类型的铸态 Mg-Y-Zn 合金的显微组织和力学性能演变。结果表明，所研究的合金具有典型的α-Mg枝晶组织，具有不同的金属间化合物，包括I相、I+W相、W相、LPSO+W相和LPSO相。结合显微组织观察和差示扫描量热法结果详细分析了 Mg-Y-Zn 合金的相演变。五种不同成分的力学性能强化效果表明，第二相强化是主要的强化机制，其贡献顺序为W>I+W>LPSO+W>I>LPSO。基于透射电子显微镜分析，与其他相相比，层状 W 相有效地阻碍了位错运动，并且具有 W 相的合金具有高强度。LPSO 相分别在拉伸和压缩过程中显示断裂和扭结带，这导致含有 LPSO 的合金出现明显的屈服不对称性 (>1.1)。具有 I 或 W 相的其他合金的屈服各向异性约为 1.0。Mg-Y-Zn合金的拉伸性能足以进行机械设计。