Abstract
A solid-state joining process, called friction bit joining (FBJ), was used to spot weld aluminum alloy 7075-T6 to dual phase 980 steel. Lap shear failure loads for specimens without adhesive averaged about 10kN, while cross tension specimens averaged 2.8kN. Addition of adhesive with a thickness up to 500 µm provided a gain of about 50% to lap shear failure loads, while a much thinner layer of adhesive caused a rise of about 20% to cross tension failure loads. Microstructures of the welds were martensitic, but the hardness of the joining bit portion was greater, owing to its higher alloy content. Softening in the heat affected zone (HAZ) of a welded joint appeared to be relatively small, though enough to cause some nugget pullout failures in lap shear tension. Other failures in lap shear tension were interfacial, while all of the failures in cross tension were interfacial.A solid-state joining process, called friction bit joining (FBJ), was used to spot weld aluminum alloy 7075-T6 to dual phase 980 steel. Lap shear failure loads for specimens without adhesive averaged about 10kN, while cross tension specimens averaged 2.8kN. Addition of adhesive with a thickness up to 500 µm provided a gain of about 50% to lap shear failure loads, while a much thinner layer of adhesive increased cross tension failure loads by 20%. Microstructures of the welds were martensitic, but the hardness of the joining bit portion was greater than that of the DP 980, owing to its higher alloy content. Softening in the heat affected zone (HAZ) of a welded joint appeared to be relatively small, though enough to cause nugget pullout failures in some lap shear tension specimens. Other failures in lap shear tension were interfacial, while all of the failures in cross tension were interfacial.
