This study was undertaken to understand the fundamentals of T-Al₆Mg₁₁Zn₁₁ intermetallic phase precipitation in heat-resistant Al–Mg–Zn ternary alloys, with the goal of further strength improvements. The thermodynamic assessment involved three alloy compositions, Al–4Mg–4.5Zn, Al–5Mg–3.5Zn, and Al–7Mg–1.5Zn (at%), with the T phase in a fixed fraction (approximately 6–7.5%) in equilibrium with the α-Al phase at 300 °C. The alloy compositions were set on different tie-lines between the α-Al and T phases in the two-phase region, resulting in varied compositions of each phase. In the three experimental alloys aged at 300 °C, the T phase precipitated on the grain boundaries of the α-Al matrix, and granular precipitates were homogeneously dispersed intragranularly. There was no significant difference in the precipitation morphology. It was demonstrated that the lattice parameters of the T and α-Al phases could be controlled based on the alloy composition and applied heat treatments. However, the lattice parameters have no significant effect on the precipitation morphologies of the thermodynamically stable T phase in the Al–Mg–Zn ternary alloys. The Zn-rich Al–4Mg–4.5Zn alloy exhibited a pronounced softening behavior after 10 h of aging due to the enhanced coarsening of precipitates in the α-Al matrix. The thermal instability of the precipitates was responsible for the transformation sequence from the initially formed metastable phases (η-Zn₂Mg associated phases) to the stable T phase. These results provided a fundamental insight that alloy strengthening by introducing thermodynamically stable intermetallic phases is essential for sustaining the strength of heat-resistant Al–Mg–Zn ternary alloys after long-term treatment at elevated temperatures.

本研究旨在了解 T-Al ₆ Mg ₁₁ Zn ₁₁的基本原理耐热Al-Mg-Zn三元合金中的金属间相析出，以进一步提高强度。热力学评估涉及三种合金成分，Al-4Mg-4.5Zn、Al-5Mg-3.5Zn 和 Al-7Mg-1.5Zn（at%），其中 T 相在固定分数（约 6-7.5%）中在 300 °C 时与 α-Al 相平衡。合金成分设置在两相区域中α-Al和T相之间的不同联系线上，导致各相的成分不同。在 300 °C 时效的三种实验合金中，T 相在 α-Al 基体的晶界析出，粒状析出物均匀分散在晶内。沉淀形态没有显着差异。结果表明，可以根据合金成分和应用的热处理来控制 T 和 α-Al 相的晶格参数。然而，晶格参数对 Al-Mg-Zn 三元合金中热力学稳定 T 相的析出形态没有显着影响。由于 α-Al 基体中析出物的粗化增强，富锌 Al-4Mg-4.5Zn 合金在时效 10 小时后表现出明显的软化行为。沉淀物的热不稳定性是由最初形成的亚稳相（η-Zn 由于 α-Al 基体中析出物的粗化增强，富锌 Al-4Mg-4.5Zn 合金在时效 10 小时后表现出明显的软化行为。沉淀物的热不稳定性是由最初形成的亚稳相（η-Zn 由于 α-Al 基体中析出物的粗化增强，富锌 Al-4Mg-4.5Zn 合金在时效 10 小时后表现出明显的软化行为。沉淀物的热不稳定性是由最初形成的亚稳相（η-Zn₂ Mg 相关相）到稳定的 T 相。这些结果提供了一个基本见解，即通过引入热力学稳定的金属间相来强化合金对于在高温下长期处理后保持耐热铝镁锌三元合金的强度至关重要。