Mg-Gd based alloys are an important class of high-performance Mg alloys. In this study, three Mg-Gd alloys with different gadolinium (Gd) contents: Mg-9.54Gd-0.40Zr (wt.%, G10 K), Mg-15.11Gd-0.35Zr (wt.%, G15 K) and Mg-19.67Gd-0.33Zr (wt.%, G20 K) were prepared by semicontinuous casting and subsequent solution and aging heat treatments. The role of Gd content on microstructures and mechanical properties of the Mg-Gd-Zr alloy is studied. All three as-cast alloys exhibit eutectic phases of Mg₅Gd, with the amount increasing as the Gd content rises. Mg₅Gd disappears after the solution heat treatment (the G10 K alloy solution-treated at 480 °C for 4 h, the G15 K alloy at 500 °C for 12 h and the G20 K alloy at 520 °C for 24 h, respectively). Aging heat treatment at 200 °C for 64 h after solution introduces numerous prismatic β′ precipitates, with a significant increase in their area number density corresponding to increased Gd content. Additionally, the morphology of the β′ precipitates exhibits distinct variations: the G10 K alloy is characterized by an enhanced aspect ratio. Consequently, the peak-aged G10 K alloy demonstrates superior strength-ductility synergy, with a yield strength (YS) of 216 ± 1 MPa, an ultimate tensile strength (UTS) of 363 ± 1 MPa, and an elongation (EL) of 8.7 ± 0.6 %. This study suggests that plasticity diminishes and precipitation strengthening is limited when the gadolinium content exceeds 15 wt.%.

中文翻译：

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半连续铸造 Gd 含量对 Mg-xGd-Zr 合金组织和力学性能的影响


Mg-Gd 基合金是一类重要的高性能 Mg 合金。本研究采用半连续铸造和随后的固溶和时效热处理，制备了三种不同钆 （Gd） 含量的 Mg-Gd 合金：Mg-9.54Gd-0.40Zr（重量%，G10 K）、Mg-15.11Gd-0.35Zr（重量%，G15 K）和 Mg-19.67Gd-0.33Zr（重量%，G20 K）。研究了 Gd 含量对 Mg-Gd-Zr 合金的微观组织和机械性能的影响。所有三种铸态合金都表现出_{Mg 5}Gd 的共晶相，随着 Gd 含量的增加，其含量会增加。固溶热处理后 Mg₅Gd 消失（G10 K 合金在 480 °C 下固溶处理 4 h，G15 K 合金在 500 °C 下处理 12 h，G20 K 合金在 520 °C 下处理 24 h）。固溶后在 200 °C 下老化热处理 64 小时，引入许多棱柱形 β' 沉淀物，其面积数密度显着增加，对应于 Gd 含量的增加。此外，β' 沉淀物的形态表现出明显的变化：G10 K 合金的特点是提高了纵横比。因此，峰时效 G10 K 合金表现出卓越的强度-延展性协同作用，屈服强度 （YS） 为 216 ± 1 MPa，极限抗拉强度 （UTS） 为 363 ± 1 MPa，伸长率 （EL） 为 8.7 ± 0.6 %。这项研究表明，当钆含量超过 15 wt.% 时，塑性会降低，析出强度会受到限制。