Abstract
Dissimilar materials lap joining of aluminum alloy to galvanized steel sheets was investigated with refilled friction stir spot welding (Refilled FSSW). For the lap joint between 1.0mm thick Novelist AC 170 PX aluminum alloy and 1.2mm thick ST06 Z galvanized steel sheets, the maximum tensile/shear fracture load is 3044N with cross-tension fracture load of 296N. For that between 1.5mm thick Aleris Superlite 200 ST aluminum alloy and 1.2mm thick ST06 Z galvanized steel sheets, the maximum tensile/shear fracture load reaches 4500N and the maximum cross-tension fracture load is 359N. All samples failed through the Al/steel interface during tensile/shear and cross-tension tests. The microstructure, composition, fractogragh and fracture mode of Al/steel joints were analyzed with electron probe microanalysis (EPMA), scanning electron microscope (SEM) and X-ray diffraction (XRD). Zinc and oxygen rich layer were observed in the interface on aluminum alloy side, and ZnO phase was detected on the fractured surface of both aluminum alloy and steel sides. The samples during tensile/shear test failed mainly through shear brittle fracture with features of cleavage and intergranular fracture feature. The spot weld can be distinguished as pin-refilled zone and sleeve-plunging zone due to the distribution of zinc coating.
Published Version
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