Resistance spot welding (RSW) of Al-Si-coated PHS was undertaken, and the effect of Al-Si coating on nugget formation and mechanical properties was investigated. Press-hardened steel (PHS) has long been applied to automotive body structure construction to support mass and corresponding greenhouse gas emission reductions. PHS materials are often combined with an Al-Si coating applied as an oxidation barrier though unfortunately, the Al-Si coating poses a challenge to the resistance spot welding (RSW) of PHS containing stack-ups. As a newly developed coating for the hot stamping process, the property of Al-Si coating is different from base metal and traditional coatings, and the influence mechanism of Al-Si coating on the welding process is not clear. It would remain at nugget edge and might cause severe stress concentration. To investigate this problem, RSW of 1.5-mm Al-Si-coated PHS was undertaken, and the results indicate that a large portion of the Al-Si coating is extruded and forms a sharp notch close to the nugget edge during the welding process. During the post-weld cooling stage, a thin layer of residual coating is formed between the nugget and notch root. The mechanical performance of the welded joints is limited by the thin residual Al-Si layer which acts as a preexisting crack and supports the interfacial fracture. The presence of the Al-Si coating at the faying interface also significantly delays nugget formation, though it contributes to a larger nugget size by inhibiting expulsion events at the faying interface.

中文翻译：

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铝硅涂层对压力硬化钢焊接性的影响

进行了铝硅涂层小灵通的电阻点焊（RSW），并研究了铝硅涂层对熔核形成和力学性能的影响。压硬化钢（PHS）长期以来一直用于汽车车身结构的制造，以支持减少质量和相应地减少温室气体排放。PHS材料通常与用作氧化阻挡层的Al-Si涂层结合使用，尽管遗憾的是，Al-Si涂层对包含PHS的叠层的电阻点焊（RSW）构成了挑战。作为一种新的热冲压工艺涂层，Al-Si涂层的性能与贱金属和传统涂层不同，而且Al-Si涂层对焊接工艺的影响机理尚不清楚。它会保留在金块边缘，并可能导致严重的应力集中。为了研究该问题，进行了1.5mm Al-Si涂层PHS的RSW，结果表明，在焊接过程中，大部分Al-Si涂层被挤出并在靠近熔核边缘的地方形成一个尖锐的缺口。在焊后冷却阶段，在熔核和缺口根之间会形成一层薄薄的残留涂层。焊接接头的机械性能受到薄薄的残留Al-Si层的限制，该Al-Si层充当预先存在的裂纹并支撑界面断裂。尽管在接合界面处存在Al-Si涂层，但通过抑制在接合界面处的排出事件而有助于增大熔核尺寸，但也显着延迟了熔核的形成。结果表明，在焊接过程中，大部分的Al-Si涂层被挤压并在靠近熔核边缘的地方形成一个尖锐的缺口。在焊后冷却阶段，在熔核和缺口根之间会形成一层薄薄的残留涂层。焊接接头的机械性能受到薄薄的残留Al-Si层的限制，该Al-Si层充当了预先存在的裂纹并支撑了界面断裂。尽管在接合界面处存在Al-Si涂层，但通过抑制在接合界面处的排出事件而有助于增大熔核尺寸，但也显着延迟了熔核的形成。结果表明，在焊接过程中，大部分的Al-Si涂层被挤出并在靠近熔核边缘的地方形成一个尖锐的缺口。在焊后冷却阶段，在熔核和缺口根之间会形成一层薄薄的残留涂层。焊接接头的机械性能受到薄薄的残留Al-Si层的限制，该Al-Si层充当了预先存在的裂纹并支撑了界面断裂。尽管在接合界面处存在Al-Si涂层，但通过抑制在接合界面处的排出事件而有助于增大熔核尺寸，但也显着延迟了熔核的形成。焊接接头的机械性能受到薄薄的残留Al-Si层的限制，该Al-Si层充当了预先存在的裂纹并支撑了界面断裂。尽管在接合界面处存在Al-Si涂层，但通过抑制在接合界面处的排出事件而有助于增大熔核尺寸，但也显着延迟了熔核的形成。焊接接头的机械性能受到薄薄的残留Al-Si层的限制，该Al-Si层充当了预先存在的裂纹并支撑了界面断裂。尽管在接合界面处存在Al-Si涂层，但通过抑制在接合界面处的排出事件而有助于增大熔核尺寸，但也显着延迟了熔核的形成。