Microstructural evolution, shear mechanical properties, and strengthening mechanisms of Mg–4Zn alloys with 0.5% Mn and Y: Comparison of as-homogenized and hot-rolled conditions

The influences of separately adding 0.5 wt% Mn and Y elements, as well as hot rolling on the microstructure, texture, mechanical behavior, and strengthening of homogenized Mg–4Zn alloy were investigated. Optical and scanning electron microscopy showed that while the grain size of homogenized Mg–4Zn alloy was significantly reduced by Mn addition, it was increased by Y addition due to the coarse intermetallic particles accumulated at the grain boundaries and the lower capability of Y in grain growth restriction. Hot rolling reduced grain size in both Mn- and Y-containing alloys, where the finest grain size of 16 µm was achieved in the Y-bearing alloy. New second phase particles, such as Mn-rich and Mg3Zn6Y compounds, were formed at the expense of MgZn2 particles. Texture analysis showed that by adding Mn and Y elements, the relatively weak basal texture of the Mg–4Zn alloy was changed to basal pole splitting toward the TD in the homogenized state. Besides, hot rolling produced a strong basal texture in all three alloys, and the addition of Mn and Y decreased texture intensity due to dynamic recrystallization (DRX) and finer grain structure. Mechanical properties, assessed by shear punch testing (SPT), showed improved strength with the addition of the third elements and hot rolling. Quantitative analysis revealed that grain size and solid solution strengthening mechanisms are responsible for improved shear yield stress in both Mn- and Y-containing alloys after hot rolling.