Aluminium alloy 6061-T6 is utilized in aerospace industry for developing pressure vessel liner. Cold metal transfer is a promising welding process used in fabricating aluminium structures. The present work is focussed to achieve an optimum welding parameter for joining a 3.5-mm thick pressure vessel and to examine the mechanical properties and metallurgical nature of the weldment. The welded joint was evaluated as defect free using radiography test. The joint efficiency (66.61%) and measured microhardness of weldment (59.78 HV) exhibited promising results. The effect of grain coarsening in the heat affected zone (HAZ) and weld zone is attributed to the thermal gradients during welding. Dissipation of small amounts of strengthening elements Si and Mg during welding leads to reduction in mechanical properties. X-ray diffraction peaks revealed the presence of intermetallic Al–Si and Fe–Si in the weld zone. Fractography examination confirms the ductile type of failure in the fractured surface of the tensile samples.
