Thermal behaviour and microstructure evolution of new ternary eutectic alloy in Al-Cu-Si-Ni system
Thermal behaviour and microstructure evolution of new ternary eutectic alloy in Al-Cu-Si-Ni system
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DOI：
10.1016/j.jallcom.2023.168942
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发表时间：
2023-01
影响因子：
6.2
通讯作者：
Qing Cai;C. Fang;C. Mendis;I. Chang;B. Cantor
中科院分区：
文献类型：
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作者：
Qing Cai;C. Fang;C. Mendis;I. Chang;B. Cantor
采用电弧熔炼和吸铸法制备了四元Al-Cu-Si-Ni系共晶合金。在组成为Al67.2Cu24Si8Ni0.8 （wt%）的四元合金体系中发现了不变的三元共晶反应（α-Al+Si+θ-Al2(CuNi)）。在三元共晶反应中，Ni （~ 1.7 at%）溶解在四方θ-Al2Cu中。密度泛函理论（DFT）计算表明，在高温下，构型熵稳定了θ-Al2Cu晶格中随机取代Ni的Cu位。凝固共晶组织为片层状θ-Al2（CuNi）相，片层厚度为130±30 nm，呈碎片状；Si为纤维状，纤维直径小于100 nm。研究了Al-Cu-Si-Ni共晶合金凝固后退火后的热稳定性，发现三元共晶组织的热稳定性优于相应的Al33Cu （wt%）二元共晶组织。结果表明，θ-Al2（CuNi）相中的Ni溶液有助于该三元共晶组织的热稳定性，β2-Al3(CuNi)2（β1-(Cu2.9Ni0.1)Al型，fm - 3m）相在不同温度下退火后可由θ-Al2（CuNi）相转变而成。Al-Cu-Si-Ni共晶合金具有优良的铸态硬度和热稳定性。这对于设计适用于高温环境的新型铝合金具有潜在的价值。
Eutectic alloys were fabricated from the quaternary Al-Cu-Si-Ni system via arc melting and suction casting. An invariant ternary eutectic reaction (α-Al+Si+θ-Al2(CuNi)) was found in the quaternary alloy system with a composition of Al67.2Cu24Si8Ni0.8 (wt%). The dissolution of Ni (∼1.7 at%) into tetragonal θ-Al2Cu takes place during this ternary eutectic reaction. Density functional theory (DFT) calculations show that the configurational entropy stabilises this level of randomly substituted Ni with Cu sites in the θ-Al2Cu lattice at high temperatures. The as-solidified eutectic microstructure exhibits a lamellar θ-Al2(CuNi) phase showing fragmented lamellar morphology with a lamellar thickness of 130 ± 30 nm and Si exhibits fibrous morphology with a fibre diameter below 100 nm. The thermal stability of the Al-Cu-Si-Ni eutectic alloy after post-solidification annealing was investigated, and the thermal stability of the ternary eutectic microstructure is better than the corresponding Al33Cu (wt%) binary eutectic microstructure. It was found that Ni solution in θ-Al2(CuNi) phase contributes to the thermal stability of this ternary eutectic microstructure and β2-Al3(CuNi)2(β1-(Cu2.9Ni0.1)Al type, Fm-3 m) phase can transform from θ-Al2(CuNi) phase after annealing at different temperatures. The Al-Cu-Si-Ni eutectic alloy has excellent as-cast hardness together with thermal stability. It is potentially valuable for the design of new aluminium alloys for serving at elevated temperatures.