Resistance spot welding (RSW) is an economic, robust welding process, which is easy to automate and widely used in automotive industry. In this work, the resistance spot weldability of die-cast aluminum alloys EN AC-AlSi7MnMg, EN AC-AlSi9Mn and EN AC-AlSi10MnMg-T6/T7 to wrought aluminum alloy EN AW-AlSi1MnMg-T6 is investigated when applying the standard welding profile as recommended in VDA 238-401 considering main challenges in welding aluminum die castings, for example, porosity and inhomogenities. Weldability is best for EN AC-AlSi10MnMg-T6/T7, but the results show limited applicability of VDA 238-401 in general, especially for high total sheet thicknesses, because of invalid electrode force favouring spatter formation and weld spot irregularites. Still, all spot welds between die castings and 2 mm wrought aluminum sheets reach the recommended shear tension forces for spot diameter dw of 5·√t (2 mm: 5.95 kN; 3 mm: 8.96 kN; according to DIN EN ISO 18595), although being afflicted with solidification porosity and liquation cracking. Gas porosity is not observed and solidification porosity is only found to be significant for weld spot failure when being located close to the joining level, which is observed at welding depths of approximately 50% into the wrought aluminum sheet. Here, a failure path across the nugget is found. Weld porosity apart from the joining level is less significant and failure path is found along the fusion line between nugget and wrought aluminum. Instead, hardness difference between nugget and HAZ is the main reason for weld spot failure. Although the applied welding current profile is not suited best for RSW of mixed joints between aluminium die castings and wrought aluminium alloys, the results confirm its potential, for example, a significantly reduced gas porosity compared to applied fusion welding processes.

中文翻译：

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通过电阻点焊连接铝压铸件和锻铝

电阻点焊 (RSW) 是一种经济、坚固的焊接工艺，易于实现自动化，广泛应用于汽车行业。在这项工作中，研究了采用标准焊接曲线时压铸铝合金 EN AC-AlSi7MnMg、EN AC-AlSi9Mn 和 EN AC-AlSi10MnMg-T6/T7 与变形铝合金 EN AW-AlSi1MnMg-T6 的电阻点焊性能根据 VDA 238-401 中的建议，考虑焊接铝压铸件的主要挑战，例如孔隙率和不均匀性。EN AC-AlSi10MnMg-T6/T7 的焊接性最好，但结果显示，VDA 238-401 一般而言适用性有限，特别是对于高总板材厚度，因为无效的电极力有利于飞溅形成和焊点不规则。尽管如此，压铸件和 2 mm 锻铝板之间的所有点焊均达到点直径 d 的建议剪切拉力w5·√t（2 毫米：5.95 kN；3 毫米：8.96 kN；根据 DIN EN ISO 18595），尽管受到凝固孔隙和液化开裂的影响。没有观察到气孔，只有当位于靠近连接水平时，凝固孔隙才对焊点故障产生显着影响，这是在锻铝板的焊接深度约 50% 处观察到的。在这里，找到了穿过金块的故障路径。除了连接水平之外，焊接孔隙率不太重要，并且沿着熔核和锻铝之间的熔合线发现了失效路径。相反，熔核和热影响区之间的硬度差异是焊点失效的主要原因。尽管所应用的焊接电流曲线并不最适合铝压铸件和变形铝合金之间的混合接头的 RSW，但结果证实了其潜力，例如，与所应用的熔焊工艺相比，气体孔隙率显着降低。