Abstract We designed three Al-based cast alloys strengthened by T-Al6Mg11Zn11 intermetallic phases using a eutectic reaction (liquid → α(fcc) + T) in the Al–Mg–Zn ternary system and then fabricated them using solidification processes. Thermodynamic assessment provided target alloy compositions of Al–26.5Zn–21.5 Mg (at%), Al–23.5Zn–22.5 Mg (at%), and Al–13Zn–28Mg (at%) with the α -Al (fcc) phase in equilibrium with the T phase with high fractions (>60%). All of the alloys exhibited regularly arrayed fibers of the α phase embedded in a T-phase matrix in α/T two-phase eutectic microstructures. A slight effect of phase compositions on the fibrous eutectic morphology was observed, whereas the volume fraction of the T phase could be controlled according to the thermodynamic assessments. The fibrous α phases had faceted interfaces of {111} planes with a surrounding T-phase matrix, suggesting a low interfacial energy of the α/T interfaces. The fabricated eutectic alloys exhibited a high Vickers hardness (>230 HV) and high yield strength at elevated temperatures above 250 °C. The Mg-rich alloy with a composition of Al–13Zn–28Mg (at%) exhibited a relatively lower hardness, responsible for the low hardness of the T phase with a Mg-rich composition. The Mg-rich alloy exhibited the plasticity at a lower temperature of 200 °C but comparatively lower strength at elevated temperatures above 250 °C. These results indicated that chemical composition strongly affected the mechanical properties of the T phase in the eutectic alloys. The present results provide important insights into control of the mechanical properties of Al-based eutectic alloys reinforced by the T intermetallic phase.

中文翻译：

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Al-Zn-Mg三元合金共晶组织中T-Al6Mg11Zn11相的形貌和力学性能

摘要 我们设计了三种由 T-Al6Mg11Zn11 金属间相强化的铝基铸造合金，在 Al-Mg-Zn 三元体系中使用共晶反应（液体 → α(fcc) + T），然后使用凝固工艺制造它们。热力学评估提供了 Al–26.5Zn–21.5 Mg (at%)、Al–23.5Zn–22.5 Mg (at%) 和 Al–13Zn–28Mg (at%) 与 α -Al (fcc) 相的目标合金成分与具有高分数 (>60%) 的 T 相平衡。所有合金都表现出规则排列的 α 相纤维嵌入在 α/T 两相共晶显微组织中的 T 相基体中。观察到相组成对纤维共晶形态的轻微影响，而 T 相的体积分数可以根据热力学评估进行控制。纤维状 α 相具有 {111} 面与周围 T 相基质的多面界面，表明 α/T 界面的界面能较低。制造的共晶合金在高于 250°C 的高温下表现出高维氏硬度 (>230 HV) 和高屈服强度。具有 Al–13Zn–28Mg (at%) 成分的富镁合金表现出相对较低的硬度，这是导致富镁成分 T 相硬度低的原因。富镁合金在 200°C 的较低温度下表现出塑性，但在 250°C 以上的高温下强度相对较低。这些结果表明化学成分强烈影响共晶合金中 T 相的机械性能。