EXPERIMENTAL COMPARISON ON MECHANICAL PROPERTIES, MICROSTRUCTURAL CHANGES AND HEAT-AFFECTED-ZONE (HAZ) SIZE OF TIG- AND LASER WELDED EN AW 6082-T6

Abstract

The heat-affected zone (HAZ) reduces 30%-50% of mechanical strength in a welded 6000 series of aluminium components. The softening phenomenon of welded aluminium is not adequately addressed in current design standards such as Eurocode 9 and the British Standard Institution (BSI) Standard. In the present study, comprehensive experimental work is conducted to investigate the influence of welding methods and parameters on the occurrence of HAZ. Through experimental analysis of tungsten inert gas (TIG) and laser welding coupons, the severity and extension of HAZ were compared using tensile strength, hardness values and microstructure distribution. It is evident that tensile strength and hardness values of welded components significantly depended on heat input, welding speed, and welding method. The strength reduction in laser-welded components was inconsistent with that of TIG-welded components. However, the extent of HAZ was much narrower in laser-welded components than in TIG welding. The grain size significantly increased after the welding process due to the fusion process. The orientation of the grain was found to be different for each welding method and was greatly influenced by the welding speed and temperature gradient of the weld pool. A comparitive analysis of mechanical and microstructural properties in TIG and laser-welded components can provide a basis to further improve the current design standards, particularly on the softening factor of welded joining. The results will significantly contribute to the enhancement of welding quality in the industrial joining practice.