Strength and fatigue crack growth behaviours of metal inert gas AA5083-H116 welded joints under in-process vibrational treatment

Abstract

Abstract Strength and fatigue properties are important design considerations for many aluminium welded structures which are operated under cyclic loadings such as ships, railway vehicles and car bodies. Over the years, various weld treatments have been developed to improve the quality of weld joints through modification of microstructure and residual stress. In the present study, in-process vibrational treatment has been applied to metal inert gas (MIG) welding of 5083-H116 aluminium alloy plates at various frequencies of 100, 300 and 500 Hz in effort to enhance strength and fatigue crack growth resistance of the weld joints. Experimental works including microstructure observation, microhardness and tensile tests, residual stress measurements and fatigue crack growth tests were performed. Results showed that in-process vibrational treatment obviously increased the ultimate tensile strength of the weld joints with the best frequency was achieved at 300 Hz. It was found that the strength of the weld at this condition was increased around 51.3 % higher than the weld in as welded condition owing to grain refinement and increasing amount of equiaxed dendritic microstructure in the weld metal region. These fine grained equiaxed dendritic structures combined with compressive residual stress induced by vibrational treatment could improve fatigue crack growth performance of the welds.