By employment of variable polarity cold metal transfer welding, 1.5 mm 6451 aluminum (Al) alloy sheets and 0.8 mm DC56 galvanized mild steel sheets were welded with ER1100 filler wire to clarify the correlation between the heat input, microstructure characteristics and tensile-shear strength. It was found Al-Zn hypoeutectoid dendrites formed in the weld toe, where shrinkage was evident at the dendritic clearances. Intermetallic compounds (IMCs) formed at the Al/steel interface were composed of a dominant Fe₂Al₅ phase on the steel side and a minor FeAl₃ phase on the Al side. As the heat input increased from ∼82.8 J/mm to ∼443.7 J/mm, the maximum thickness of Fe₂Al₅ increased from ∼3.7 μm to ∼18.7 μm. The joint strength increased first with increasing heat input, then decreased as the heat input further increased. The joint strength was primarily determined by two competitive factors, the Zn accumulation and the IMC growth. The Zn accumulation tended to occur near the interface of weld with low heat input, leading to the harmful Al-Zn structure with interdendritic shrinkage. IMC overgrowth would be produced when excessive heat input was applied, resulting in embrittlement of Al/steel interface. It was suggested to improve the joint strength by the reduction of the Zn accumulation and the inhibition of the IMC growth through a moderate and evenly distributed heat input.

通过使用可变极性冷金属传递焊接，将1.5毫米6451铝（Al）合金薄板和0.8毫米DC56镀锌低碳钢板与ER1100填充焊丝焊接在一起，以阐明热量输入，显微组织特征和拉伸剪切强度之间的关系。发现在焊趾中形成了Al-Zn次共析树突，其中在树突间隙处明显收缩。在Al /钢界面处形成的金属间化合物（IMC）由钢侧的主要Fe ₂ Al ₅相和Al侧的次要FeAl ₃相组成。随着热量输入从〜82.8 J / mm增加到〜443.7 J / mm，Fe ₂ Al ₅的最大厚度从〜3.7μm增加到〜18.7μm。接头强度首先随着热量输入的增加而增加，然后随着热量输入的进一步增加而降低。接头强度主要由两个竞争因素决定，即锌积累和IMC生长。Zn的蓄积倾向于在低热量输入的焊缝界面附近发生，从而导致有害的Al-Zn结构并出现枝晶间收缩。当施加过多的热量输入时，会产生IMC过度生长，导致Al /钢界面脆化。建议通过适度且均匀分布的热量输入来减少锌的积累并抑制IMC的生长，从而提高接头强度。