An Investigation on fatigue crack propagation in gas metal and hybrid plasma-gas metal arc weldments of AA5083-H111

Okan, Kemal
5083 aluminum alloy among 5XXX series has the greatest strength and is commonly used for its good weldability, corrosion resistance and moderate strength. In this study, 5083-H111 aluminum alloy plates were joined by Gas Metal Arc Welding (GMAW) and Hybrid Plasma Arc Welding (HPAW) techniques. Mechanical strength of base metal (BM) and welded samples was examined using hardness, tensile and toughness tests. Crack propagation behavior of BM, GMA welded and HPA welded samples was investigated by fatigue crack growth (FCG) tests both in welding and transverse to welding directions. Hardness test results show that there is almost no variation in the hardness profile throughout the welded section in HPA weldment. However, GMA weldment exhibits lower hardness values in some parts of the weld section. GMAW and HPAW processes gave similar tensile strength results though HPAW has elongation (%), ultimate tensile strength (UTS) and yielding point values which are favorable over GMAW. Fracture toughness test results showed that GMA and HPA welded samples had almost the same critical stress intensity factor, Kc value. When the FCG rates in welding direction are compared at the same stress intensity range (ΔK), HPA welded sample has the lowest FCG rate. GMA welded sample has lower FCG rate in the weld region compared to HPA welded sample in transverse direction.