Welding high-entropy alloy (HEA) to Mg alloy has gained increasing attention for multi-metal structure design, while intrinsic sluggish diffusion kinetics of HEA confines diffusion-controlled interfacial reactions and makes it challenging to establish robust metallurgical bonding. This study investigated welding of FeCoCrNiMn HEA to commercial AZ31 as a model combination to pioneer this field. Interfacial phase separation phenomenon was observed, with the diffusion accelerated by in-situ engineering a submicron-scale thick (∼400–500 nm) HEA nearby the interface into nanocrystalline-structure during friction stir welding. Abundant grain boundaries generated in this nanocrystalline-interlayer serve as diffusion short-circuits and energetically preferred nucleation-sites, which promoted Al in AZ31 to diffuse into HEA and triggered quick separation into body-centered cubic AlNi-type and tetragonal FeCr-type intermetallics. HEA and AZ31 were thus metallurgically bonded by these interfacial intermetallics. The joint shows exceptional strength in tensile lap-shear testing with fracture largely occurred within AZ31 rather than right along interface as commonly reported previously for dissimilar joints.

中文翻译：

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在 AZ31/高熵合金搅拌摩擦焊过程中，通过增强 Al 扩散诱导的相分离实现稳健的界面键合


在多金属结构设计中，将高熵合金 （HEA） 焊接到镁合金上越来越受到关注，而 HEA 固有的缓慢扩散动力学限制了扩散控制的界面反应，使建立稳健的冶金结合变得具有挑战性。本研究调查了 FeCoCrNiMn HEA 与商业 AZ31 的焊接，作为开创该领域的模型组合。观察到界面相分离现象，在搅拌摩擦焊过程中，通过原位工程将界面附近的亚微米级厚 （∼400–500 nm） 高熵合金加速扩散为纳米晶结构。在这个纳米晶中间层中产生的丰富晶界充当扩散短路和能量优先的成核位点，这促进了 AZ31 中的 Al 扩散成 HEA，并触发快速分离成体心立方 AlNi 型和四方 FeCr 型金属间化合物。因此，HEA 和 AZ31 通过这些界面金属间化合物进行冶金键合。该接头在拉伸搭接剪切测试中显示出非凡的强度，断裂主要发生在 AZ31 内，而不是像以前通常报道的不同接头那样沿着界面发生。