Fatigue and fracture toughness of electron beam welded joints of aluminum alloy 6156 (Al–Mg–Si) for aerospace applications

The mechanical behavior of AA6156 electron beam welded joints and the effect of artificial aging heat treatments on the fracture‐related properties were investigated. The fatigue test results of the welded joints presented lower fatigue endurance limit by approximately 60%, when compared to the base material. Fracture resistance results showed that the critical stress intensity factor (Kcr) was essentially decreased (~32%) in the as‐welded condition. Heat treatment before welding presented a 15% increase in Kcr for 4 h of artificial aging, while a decrease in Kcr was noticed for prolonged isothermal heat treatment prior to welding. By applying post welding heat treatments, all investigated isothermal heat treatment conditions resulted in decreasing Kcr. Tensile test results of the welded joints showed that an almost 40% increase of the yield stress can be achieved with appropriate post welding heat treatment, on the expense of only 10% decrease in Kcr.