CO(2) and Nd:YAG laser beam welding of 6111-T4 and 5754-O aluminum alloys for automotive applications

There are two important trends that are currently taking place in the forming of sheet metal into automotive body components. One of these trends is the substitution of aluminum sheet alloys for steel. The other trend is the use of tailor welded blanks. Currently, there exists strong motivation for research to combine these technologies in order to produce tailor welded aluminum blanks. The focus of the current study is to develop welding procedures for autogenous CO{dollar}sb2{dollar} (Continuous) and Nd:YAG (Continuous and Pulsed) laser beam welding of 6111-T4 and 5754-O aluminum alloys. The mechanical and microstructural characteristics of the welded joints were evaluated using tensile tests, microhardness tests, optical microscopy and chemical analysis. Results indicate that this alloy can be autogenously laser welded with full penetration, minimum surface discontinuities and little if any loss of magnesium through vaporization from the fusion zone.; The total elongation (all weld metal) in the longitudinal direction for 6111-T4 laser welds made using 3 kW CO{dollar}sb2{dollar} and 2 kW Pulsed Nd:YAG show a decreasing trend with increasing travel speed. Studies indicate that the decreasing trend is probably due to the combination of two factors: orientation of the grains with respect to the loading direction and solidification cracking. The total elongation (all weld metal) of the 6111-T4 laser welds made using 5 kW CO{dollar}sb2{dollar} and 3 kW CW Nd:YAG did not show a consistent trend with travel speed. The main reason for this is solidification cracking. The welds made with 2 kW Pulsed Nd:YAG with travel speed between 100 and 150 ipm displayed the highest total longitudinal elongation (20.78 percent to 16.45 percent), compared to the base metal value of 27.8 percent.; The total elongation (all weld metal) in the longitudinal direction for 5754-O welds made using 5 kW CO{dollar}sb2{dollar} and 3 kW CW Nd:YAG showed a slight decrease with increasing travel speed. Like 6111-T4, studies indicate that the decreasing trend is due to the orientation of the grains with respect to the loading directions. A very interesting observation was the weld surface condition did not have any effect on the ductility of the welded aluminum specimens (both 6111-T4 and 5754-O) studied in this investigation.