Abstract Mg-9.5Gd-0.9Zn-0.5Zr alloys were water quenched (WQ), air cooled (AC) and furnace cooled + water quenched (FC + WQ) after solution treatment. Effects of quenching conditions on the microstructure, mechanical properties and age hardening behavior were investigated, then the quench sensitivity and strengthening mechanism were analyzed. Results showed that only rod-like Zn2Zr3 phases were found in the WQ alloy, while Mg5Gd and 14H LPSO phases were also detected in the AC and FC + WQ alloys. The WQ alloy exhibited the most significant age hardening response, and the peak-aged alloy was consisted of densely distributed γ' + γ'' precipitates, Zn2Zr3 and Mg5Gd particles. In contrast, decreased amount of γ' + γ'' precipitates were observed in the AC and FC + WQ peak aged alloys. The increment of yield strength and ultimate tensile strength after aging treatment decreased with the decreasing quenching rate, and the elongation decreased sharply in the WQ and AC peak-aged alloys, while it only decreased slightly in the FC + WQ peak-aged alloy. The calculated strengthening contribution exhibited that the variation of precipitation strengthening in peak-aged alloys was more dramatic than that of solid solution strengthening in solution treated alloys, then lead to a higher quench sensitivity.

中文翻译：

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Mg-9.5Gd-0.9Zn-0.5Zr合金的组织演变和淬火敏感性表征

摘要 Mg-9.5Gd-0.9Zn-0.5Zr合金在固溶处理后进行水淬（WQ）、空冷（AC）和炉冷+水淬（FC+WQ）。研究了淬火条件对组织、力学性能和时效硬化行为的影响，分析了淬火敏感性和强化机制。结果表明，在 WQ 合金中只发现了棒状 Zn2Zr3 相，而在 AC 和 FC + WQ 合金中也检测到了 Mg5Gd 和 14H LPSO 相。WQ 合金表现出最显着的时效硬化反应，峰值时效合金由密集分布的 γ' + γ'' 析出物、Zn2Zr3 和 Mg5Gd 颗粒组成。相反，在 AC 和 FC + WQ 峰值时效合金中观察到 γ' + γ'' 析出物的数量减少。时效处理后屈服强度和极限抗拉强度的增量随着淬火速率的降低而减小，WQ和AC峰时效合金的伸长率急剧下降，而FC+WQ峰时效合金的伸长率仅略有下降。计算的强化贡献表明，峰值时效合金中析出强化的变化比固溶处理合金中的固溶强化变化更大，从而导致更高的淬火敏感性。