Mechanical performance of TIG-welded Al6061-T6 alloy under argon–helium shielding gas mixtures

Abstract This study evaluates argon–helium shielding gas mixtures in tungsten inert gas-welded Al6061-T6 alloy. Five gas compositions, from pure argon to pure helium, were tested under constant welding parameters on 6 mm-thick plates. Microstructural analysis via optical and scanning electron microscopy revealed refinement from ASTM grain size 4 in the base material to ASTM 7 in helium-rich welds; the 25% Ar–75% He mixture (hereafter referred to as G4) produced the most homogeneous fusion zone. All welded joints showed reductions in tensile strength and microhardness, characteristic of precipitation-hardened aluminum alloys. G4 performed best, retaining ~ 70% of ultimate tensile strength (UTS), ~ 65% of yield strength, and ~ 73.5% of Vickers microhardness of the base material. Pure argon led to limited penetration and heterogeneity, while pure helium caused excessive heat input and grain coarsening in the fusion zone. These results show that balanced Ar–He mixtures greatly improve weld microstructure and mechanical integrity, offering a practical guideline for high-performance Al6061-T6 joining in aerospace. Graphical abstract