Abstract Microstructure evolution and mechanical properties of Mg96.5Gd2.5Zn1 alloys in as-cast and solution-treated states were systematically studied during hot extrusion. The as-cast alloy mainly contains eutectic (Mg,Zn)3Gd compound, block-shaped 18R-LPSO structure and Mg matrix with a few lamellar long-period stacking order (LPSO) structures. The solution-treated alloy has a block-shaped 14H-LPSO structure at grain boundaries (GBs) and high-density lamellar LPSO structures within the matrix. After hot extrusion, the (Mg,Zn)3Gd phase and 18R-LPSO structure were broken an kinked, respectively. Bimodal microstructure with fine recrystallized (DRXed) grains and coarse-deformed grain were formed in both studied alloys. Sandwich-like distribution of the fine DRXed grain was observed in the as-cast-extruded alloy, which shows obviously different DRX behavior compared with the solution-treated-extruded alloy that recrystallizes at GBs. The result reveals that lamellar LPSO structure promotes DRX formation in the LPSO-free region of the matrix by accumulating dislocations at the interface frontier of lamellar LPSO/matrix. Moreover, the LPSO structure, fine DRXed grains and nanoparticles at GBs enhanced the yield strength of the wrought alloy.

中文翻译：

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Mg96.5Gd2.5Zn1合金在铸态和固溶处理状态下的显微组织演变差异

摘要 系统地研究了Mg96.5Gd2.5Zn1合金在热挤压过程中铸态和固溶态的显微组织演变和力学性能。铸态合金主要包含共晶 (Mg,Zn)3Gd 化合物、块状 18R-LPSO 结构和具有少量层状长周期堆积有序 (LPSO) 结构的 Mg 基体。固溶处理合金在晶界 (GBs) 处具有块状 14H-LPSO 结构，在基体中具有高密度层状 LPSO 结构。热挤压后，(Mg,Zn)3Gd 相和 18R-LPSO 结构分别断裂和扭结。在两种研究的合金中都形成了具有细小再结晶 (DRXed) 晶粒和粗变形晶粒的双峰显微组织。在铸态挤压合金中观察到细 DRX 晶粒的三明治状分布，与在 GB 处再结晶的固溶处理挤压合金相比，它显示出明显不同的 DRX 行为。结果表明，层状 LPSO 结构通过在层状 LPSO/基质的界面前沿积累位错来促进基质的无 LPSO 区域中的 DRX 形成。此外，LPSO 结构、细小的 DRX 晶粒和 GB 处的纳米颗粒提高了锻造合金的屈服强度。