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 (K-cr) was essentially decreased (similar to 32%) in the as-welded condition. Heat treatment before welding presented a 15% increase in K-cr for 4 h of artificial aging, while a decrease in K-cr 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 K-cr. 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 K-cr.