Effects of Ar-He shielding gas mixture on mechanical and metallurgical properties of weld metal in laser welding of 6061 T6 aluminium alloy

Abstract

In this study, a 6 mm-thick 6061 T6 aluminum alloy was welded using fiber laser welding, and its mechanical and metallurgical properties were investigated. Full penetration autogenous welds were made at a constant laser power of 4.95 kW using a continuous-wave fiber laser and focal positions of −4 mm. In addition, the shielding gas content was changed for weldments welded at different travel speeds (mm s−1). Accordingly, welding speeds were 50, 40, 35, 25, and 20 mm s−1, and the shielding gas contents were 100% argon (Ar), 10% helium (He) + 90% Ar, 30% He + 70% Ar, 50% He + 50% Ar, and 75% He + 25% Ar. Then, macro and micro images were taken, and some mechanical properties (hardness, tensile test, and bending test) were examined. As a result, the change in shielding gas content and welding speed has provided significant variations in the welding joints. Decreases in mechanical properties were detected due to the coarsening of the precipitates. On the other hand, the narrowness of the weld seam and HAZ obtained in laser welding, compared to traditional welding methods, minimizes this disadvantage.

The review of visual monitoring and recognition algorithm in laser welding

“…Pellone et al [51] pointed out that increasing the flow of shielding gas gave the external load pressure of molten pool and produce wider welding. Emine et al [52] found that as the proportion of He in the mixture increased, the width of the weld increased. The above studies show that the selection of shielding gas parameters affects molten pool stability, and then affects the welding quality.…”