Mechanical performance and metallurgical characterization of ultrasonically welded dissimilar joints

Abstract

The present research work explores the joints of various dissimilar metals produced by ultrasonic spot welding. The weld strength, interface temperature, weld area and microhardness were measured as well as the quality of weld revealed for different weld times. The tensile shear and T-peel failure load increased with increasing weld time and reaching the highest values of 1512N and 280.83N respectively for Al-Cu joints followed by Al-UNS C27000 brass and Al-AISI 304 steel combinations. With further increase in weld time, the interfacial temperature was far above than the recrystallization temperature of Al, showing a substantial loss in joint strength. An axisymmetric type hardness distribution was also noticed across the joint interface and the microhardness values increased with increasing in weld time. The highest interface diffusion layer of thickness 1.5μm was observed for Al-Cu weld coupon combination. Moreover, some intermetallic compounds such as Al2Cu, Cu5Zn8 and FeAl3 were formed during the welding of Al-Cu, Al-Brass and Al-SS sheets and the correlations of the presence of these compounds with the joint strength were also described.