| The new generation of cars have to fulfil the strict regulations regarding fuel consumption and gas emission. Thus, lightweight structures are becoming an increasingly critical target in the car body design. At the same time, other indispensable design obligations, such as safety, ride quality and affordability, also have to be met. Tailor welded blank (TWB) and welded patch- work blank techniques have been extensively used in the automotive industry as an effective way of weight reduction and stiffness improvement. TWBs capacitate further weight and strength optimisation in design by integrating sheets of different materials with different thicknesses and/ or coatings into one part. Local reinforcement with welded patchwork blanks also contributes to the weight reduction and crashworthiness of the car body. The laser welding of tailored and patchwork blanks made of galvanised steel and aluminium is widely used in the automotive industry. The weld between Zn-coated steel and aluminium commonly suffers from defects such as spatter, cavity and crack. The vaporisation of Zn is commonly known as the main source of instability in the weld pool and cavity formation, especially in a lap joint configuration. Cracks are mainly due to the brittle intermetallic compounds growing at the weld interface of aluminium and steel. This study provides a review on the main metallurgical and mechanical concerns regarding laser overlap welding of Zn-coated steel on Al-alloy and the methods used by researchers to avoid the weld defects related to the vaporisation of Zn and the poor metallurgical compatibility between steel and aluminium. |
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