Abstract The microstructure and mechanical properties of dissimilar resistance spot weldments between the sheets of 6061-T6 aluminum alloy and St-12 low carbon steel using Al0·5FeCoCrNi high entropy alloy (HEA) interlayers (with the thicknesses of 0.4, 0.7 and 1 mm) were studied and compared to interlayer-free weldment. Although HEA contained Al and Fe, its microstructure showed no evidence of Al–Fe intermetallic compounds (IMCs). Barely visible interfaces formed at the carbon steel/HEA side of all weldments, suggesting metallurgical consistency between both materials. Conversely, complex IMCs formed at the interfaces of Al/HEA, as a result of strong chemical tendency of HEA constituent elements towards the aluminum alloy. The application of HEA interlayer was found to change the type of the formed IMCs from AlxFey in the interlayer-free weldment to complex IMCs. The latter prevented cracking in the Al-side of the weldments. Meanwhile, it increased the tendency to hot tearing in the Al-side of the weldments. The thickness of HEA interlayer affected the morphology of IMCs. For instance, a 1 mm-thick interlayer produced needle-shaped complex IMCs owing to initial dissolution of IMCs into the molten aluminum and subsequent eutectic solidification. The weldments fabricated by HEA interlayer exhibited improvement of tensile shear load compared to the interlayer-free joint. Distinct fracture mechanisms were involved in the weldments produced with and without HEA interlayer. The pre-existing cracks and hot tearing at the Al-side of the joint were deduced to be responsible for the fracture initiation in the fabricated weldments without and with HEA interlayer, respectively.

中文翻译：

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使用高熵合金夹层的6061-T6铝合金/St-12碳钢异种电阻点焊

摘要 采用 Al0·5FeCoCrNi 高熵合金 (HEA) 夹层（厚度为 0.4、0.7 和 1 mm）的 6061-T6 铝合金和 St-12 低碳钢薄板异种电阻点焊的组织和力学性能进行了研究并与无夹层焊件进行了比较。尽管 HEA 含有 Al 和 Fe，但其微观结构没有显示出 Al-Fe 金属间化合物 (IMC) 的证据。在所有焊件的碳钢/HEA 侧形成几乎不可见的界面，表明两种材料之间的冶金一致性。相反，由于 HEA 组成元素对铝合金的强烈化学倾向，在 Al/HEA 的界面处形成了复杂的 IMC。发现 HEA 夹层的应用将形成的 IMC 类型从无夹层焊件中的 AlxFey 改变为复杂的 IMC。后者防止焊件的铝侧开裂。同时，它增加了焊件铝侧热撕裂的趋势。HEA 夹层的厚度影响 IMCs 的形貌。例如，由于 IMC 最初溶解在熔融铝中并随后发生共晶凝固，因此 1 毫米厚的夹层产生了针状复合 IMC。与无夹层接头相比，由 HEA 夹层制造的焊件表现出拉伸剪切载荷的改善。使用和不使用 HEA 夹层生产的焊件中涉及不同的断裂机制。