Resistance spot welding (RSW) is attractive for joining dissimilar materials, especially, aluminium to steel in automotive body. The direct joining of aluminium to steel forms an intermetallic compound (IMC) layer at their interface that dominates mechanical behaviour of the joint. A new formula was developed that considers material inhomogeneities such as the different mechanical properties in the weld such as base metal, heat affected zone (HAZ) and the weld nugget to accurately calculate the minimum weld nugget diameter required to enable pull‐out fracture. The shear strengths of weld regions such as the HAZ and IMC were directly measured and used as inputs to this new formula. The new formula was validated using experimental measurements from six combinations of aluminium–steel welds in comparison with analogous aluminium–aluminium welds. The new derivation was able to accurately predict fracture modes for all material combinations.

中文翻译：

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材料不均匀性对铝钢电阻点焊缝断裂模式的影响

电阻点焊（RSW）对于将异种材料（尤其是汽车车身中的铝与钢）连接起来很有吸引力。铝与钢的直接连接在其界面处形成金属间化合物（IMC）层，该层主导着接头的机械性能。开发了一个新的公式，该公式考虑了材料的不均匀性，例如母材，热影响区（HAZ）和熔核等焊缝中不同的机械性能，以准确计算实现拉拔断裂所需的最小熔核直径。直接测量诸如HAZ和IMC等焊接区域的剪切强度，并将其用作此新公式的输入。与六个类似的铝-铝焊缝相比，使用六种铝-钢焊缝组合的实验测量结果验证了新公式。