The influence of gradient mismatches on mechanical properties and microstructure of 2219-T6 aluminum alloy VP-TIG joints

In this paper, 6 mmthick2219-T6aluminum alloy was joined by means of variable polarity tungsten-arc welding(VP-TIG)and the influence of gradient mismatches on VP-TIG joints is investigated.The average tensile strength of the joints reduces32%, 53%and59%,when the mismatch of the joint was0.635 mm, 1.44 mm, 1.83 mm,respectively.Incomplete penetration,additional bending moment(Ma)and decrease of effective load region area are considered to explain this phenomenon.The fracture location of tensile specimens occurred at the weld zone(WZ)close to partial melt zone(PMZ),corresponding to a sharp decline of microhardness from PMZ to WZ.The original position of fracture is found at weld toe,where incomplete penetration forms due to the introduction of gradient mismatches.