Study on Microstructure and Formability of Laser Tailor-Welded Joints of Aluminum Alloy Thin Sheet

Abstract

As an advanced manufacturing technology, tailor welded blanks (TWB) not only meet different requirements of properties in different parts, but also can satisfy the requirements of weight reduction and energy conservation. 6061 aluminum alloy with the thickness of 1mm was jointed by laser beam welding technology and the microstructure of tailor-welded joints was analyzed compare to base metal. The forming and bulging property characteristics of TWB were evaluated through tensile and cupping tests. Experimental results indicated that: the weld joints contained fine equiaxed grains in the center of the weld and columnar grains and dendrites near the fusion boundary were observed to be oriented towards the center of the weld. The dendrites became smaller and thinner during the transition process from the weld fusion boundary to the center. The fracture path of the TWB tensile specimens occurred in the heat-affected zone (HAZ) with the tensile and yield strength increased while the strain hardening coefficient and elongation reduced compared to base metal. The erichsen index of TWB in the cupping test was lower than base material, which demonstrated that the bulging property of the TWB was worse than base metal.