Abstract
During fusion welding of aluminium alloy, the heat-affected zone (HAZ) reduces mechanical strength of component, particularly in 6000 series alloys, where the reduction can be 30%-50%. This softening phenomenon 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. From this study, 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. In terms of microstructural analysis, the grain size was significantly increased after the welding processes. 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. From this work, a comparison of mechanical properties and microstructural changes 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.