CO 2 laser beam welding of AM60 magnesium-based alloyThere 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 2 ͑continuous mode͒ and Nd:YAG ͑continuous and pulsed mode͒ laser beam welding of 6111-T4-aluminum alloy. The mechanical and microstructural characteristics of the welded joints were evaluated using tensile tests, microhardess 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 metal͒ in the longitudinal direction for the laser welds made using 3 kW CO 2 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 metal͒ of the laser welds made using 5 kW CO 2 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 42 and 63 mm/s displayed the highest total longitudinal elongation ͑20.78% to 16.45%͒, compared to the base metal values of 27.8%. A very interesting observation was that the weld surface condition did not have any effect on the ductility of the 6111-T4-aluminum alloy studied in this investigation.

Federal regulations have recently been enacted to reduce significantly the atmospheric pollution caused by motor vehicles. This has compelled automotive manufacturers to improve the fuel efficiency of cars and light trucks by using lightweight materials such as aluminium. The focus of the present work is to develop welding procedures for autogenous CO2 (continuous mode) and Nd–YAG (continuous mode) laser beam welding of 5754–O aluminium alloy. 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 vaporisation from the fusion zone. The total elongation (all weld metal) in the longitudinal direction for 5754–O laser welds produced using 5 kW CO2 and 3 kW continuous wave (CW) Nd–YAG shows a slight decrease with increasing travel speed. Studies indicate that the decreasing tendency is probably due to the orientation of the grains with respect to the loading direction. The welds produced using the 5 kW CO2 laser at travel speeds between 127 and 212 mm s-1 displayed a total longitudinal elongation of 19.13–15.12% and those produced using the 3 kW CW Nd–YAG laser at travel speeds between 85 and 148 mm s-1 displayed a total longitudinal elongation of 22.6–18.15%, compared with the base metal value of 28.1%. An observation of great interest was that the weld surface condition did not have any effect on the ductility of the 5754–O aluminium alloy studied in the present investigation.

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