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

摘要

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 (～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).