CO2 laser beam welding of aluminum 5754-O and 6111-T4 alloys

Legislative and market pressures have caused the automotive industry to consider more fuel efficient designs of vehicles in recent years. Many light weight material options are being explored to reduce vehicle weight. Aluminum alloys are receiving a great deal of attention. As a result, development of rapid joining techniques for aluminum alloys has become an important research issue. The objective of this investigation was to develop welding procedures for autogenous CO2 laser beam welding of aluminum 5754-O and 6111-T4 alloys for application in tailor welded blanks. The mechanical and microstructural characteristics of the welded joints were evaluated using tensile tests, microhardness tests, optical microscopy, and energy dispersive X-ray (EDAX) for local chemical analysis. Results indicate that both the alloys can be autogenously laser welded with full penetration, minimum surface discontinuities and little, if any, loss of magnesium through vaporization from the fusion zone. It was found that welds made on 5754-O with a 3-kW laser beam and a travel speed ranging between 100 and 400 in./min had total longitudinal elongation (17.3-23.6%), close to the base metal value (22%). Similar welds on Alloy 6111-T4 welds had lower longitudinal elongation (8.6-18.7%), compared to the base material (26%). The reduced ductility observed in 6111 laser welds is probably due to weld solidification cracking in the fusion zone. Based on the results, laser welded aluminum alloys possess potential for use in automotive fabrication applications.