While the interfacial phases between Al and high-entropy alloy (HEA) share the same types as that between Al and steel, it has been found previously that the thermal stability of the Al-HEA interfacial phases is significantly higher than that of the Al-steel interfacial phases. To further elucidate the reason for the exceptional thermal stability of Al-HEA interfacial phases, this study investigated the evolution of the interfacial phases formed between Al alloy and FeCoCrNiMn HEA during annealing. An Al-FeCoCrNiMn thin film diffusion couple was extracted from a friction stir lap welding (FSLW) joint by focused ion beam and then annealed at 400 °C. An amorphous layer is formed initially at the interface due to the high strain rate deformation during FSLW. The amorphous layer remained even after prolonged annealing at 400 °C (∼0.72 of Al alloy) for 60 min with very limited thickening (from 50 nm to 55 nm), showing remarkable thermal stability at the relatively high temperature. AlFe-type intermetallic compound (IMC) with the Fe site occupied by Fe, Co, Cr, Ni and Mn first nucleates at the interface between Al alloy and amorphous layer. With the annealing time extended to 180 min, the amorphous layer is partially transformed into AlFe-type IMC. The rate constant for the thickening of the reaction layer at the Al/FeCoCrNiMn interface is 0.03 μm∙min, which is much smaller than (only 0.02 times) that at the Al/steel interface under similar annealing condition. The high thermal stability of Al-HEA interfacial layer is thus attributed to the slow kinetics in crystallization of the initially formed amorphous layer, the barrier effect of amorphous layer for interdiffusion, and the reduced diffusivity inside of IMCs caused by significant fluctuations in lattice potential energy due to high-density doping with HEA elements. This finding provides new insights into the fabrication of thermally stable Al-HEA hybrid structures suitable for service conditions involving high-temperature exposure.

中文翻译：

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退火过程中铝合金与高熵合金界面相的演变

虽然Al与高熵合金(HEA)之间的界面相与Al与钢之间的界面相类型相同，但先前发现Al-HEA界面相的热稳定性明显高于Al-HEA界面相的热稳定性。钢的界面相。为了进一步阐明 Al-HEA 界面相优异热稳定性的原因，本研究研究了退火过程中铝合金和 FeCoCrNiMn HEA 之间形成的界面相的演变。通过聚焦离子束从搅拌摩擦搭接焊 (FSLW) 接头中提取 Al-FeCoCrNiMn 薄膜扩散偶，然后在 400 °C 下退火。由于 FSLW 期间的高应变率变形，最初在界面处形成非晶层。即使在 400 °C（铝合金的 ∼0.72）下长时间退火 60 分钟后，非晶层仍保持非常有限的增厚（从 50 nm 到 55 nm），在相对较高的温度下表现出显着的热稳定性。 Fe位被Fe、Co、Cr、Ni和Mn占据的AlFe型金属间化合物（IMC）首先在铝合金和非晶层之间的界面处形核。随着退火时间延长至180 min，非晶层部分转变为AlFe型IMC。在相似退火条件下，Al/FeCoCrNiMn界面反应层增厚的速率常数为0.03 μm∙min，远小于Al/钢界面反应层增厚的速率常数（仅0.02倍）。因此，Al-HEA界面层的高热稳定性归因于最初形成的非晶层的结晶动力学缓慢、非晶层对相互扩散的势垒效应以及晶格势能的显着波动导致IMC内部的扩散率降低由于 HEA 元素的高密度掺杂。这一发现为制造适合高温暴露的使用条件的热稳定 Al-HEA 混合结构提供了新的见解。