Microstructure Evolution and Forming Characteristics of Post-Weld Composite Treatment of 6061 Aluminum Alloy Tailor Welded Blanks

The mechanical properties and cross-sectional geometric dimensions of the fusion zone (FZ), heat affected zone (HAZ), and base metal (BM) of 6xxx series aluminum alloys are inconsistent after filler wire welding, which reduces the formability of aluminum alloy tailor welded blanks (TWBs). This paper proposes a post-weld cold rolling-solution heat treatment (PWCR-SHT) composite process, and the effects of weld excess metal, plastic deformation, and SHT on the formability of aluminum alloy TWBs are studied. The results show that the PWCR-SHT composite process eliminates the weld excess metal and internal pores, reduces the stress concentration at the weld toe, eliminates the local strain hardening behavior, and causes recrystallization in the FZ region. The cupping value of aluminum alloy TWBs using SHT is 105% of BM, in comparison, the cupping value of aluminum alloy TWBs using the PWCR-SHT composite process is 119% of BM, which is the result of the combined effect of geometric dimensions consistency and mechanical properties consistency.