The failure of resistance spot welds in ultra-high-strength press-hardened steels often occurs due to martensite tempering in the heat-affected zone. In the present work, however, it is shown that the failure occurs by local shear band formation at the fusion boundary (FB) in spot welds in press-hardened 22MnB5 (Al–Si coated). The failure behaviour of spot welds was investigated to understand failure mechanisms with respect to microstructural features. The results showed that a 104 μm wide shear band is located in a local area of softening adjacent to the FB. A fine-meshed model was developed using hardness-based local properties to simulate the softened zone which was able to capture the observed failure at the FB interface.

中文翻译：

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超高强度热冲压钢熔合边界剪切带形成及电阻点焊失效行为

超高强度压制硬化钢中电阻点焊的失效往往是由于热影响区的马氏体回火造成的。然而，在目前的工作中，表明失效是由在加压硬化的 22MnB5（Al-Si 涂层）的点焊中的熔合边界 (FB) 处形成的局部剪切带引起的。研究了点焊的失效行为，以了解与微观结构特征相关的失效机制。结果表明，104 μm 宽的剪切带位于与 FB 相邻的局部软化区域。使用基于硬度的局部特性开发了一个细网格模型来模拟软化区，该模型能够捕获在 FB 界面观察到的失效。