CO2 and Nd-YAG laser beam welding of 5754-O aluminium alloy for automotiveapplications

Federal regulations have recently been enacted to reduce significantly the atmospheric pollution caused by motor vehicles. This has compelled automoti ve Manufacturers to improve the fuel efficiency of cars and light trucks by using lightweight materials such as aluminium. The focus of the present wo rk is to develop welding procedures for autogenous CO (continuous mode) and Nd-YAG (continuous mode) laser beam welding of 57-54-O aluminium alloy. Th e 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 las er welded with, fall penetration, minimum surface discontinuities, and litt le if any mass of magnesium through vaporisation from the fusion zone. The total elongation all weld metal in the longitudinal direction for 5754-O la ser welds produced using 5 OF CC and 3 kW continuous ware (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 ;la ser at travel speeds between 127 and 212 min s(-1) display red a to tal lon gitudinal elongation of 19-13-15.12% and those produced rising the 3 kW CW Nd-YAG laser at travel speeds between 85 and 148 mm s-1 displayed a total l ongitudinal elongation of 22.6-18.15%, compared with the base metal value o f 28.1%. An observation of great interest was that the weld surface conditi on did not have any effect on the ductibility ductility of the 5754-O alumi nium alloy studied in the present investigation. (C) 2001 1oM Communication s Ltd.