Effect of friction stir welding on microstructure and mechanical properties of dissimilar Al 5083-H321 and 316L stainless steel alloy joints

The effect of tool traverse speed, offset and rotation direction during dissimilar butt friction stir welding of Al 5083-H321 and 316L stainless steel plates was studied at constant rotational speed of 280 rpm. The macrostructure and microstructure of the joints were examined using optical microscope and scanning electron microscope equipped with energy dispersive X-ray analysis. The tensile and hardness tests were conducted to evaluate the mechanical properties of the joints. The results showed that the joint welded at traverse speed of 160 mm/min, pin offset of 0.4 mm, and clockwise rotation condition was defect free with a maximum tensile strength of 238 MPa. The lower tensile strength of the other joints were due to their surface and cross sectional defects such as tunnel defect, voids, non-uniform distribution and large particles of the steel fragments, and micro cracks developed in the interface of the dissimilar parts. The microstructure and hardness profile of the joints confirmed that both dissimilar plates had distinct microstructural zones containing base metal, heat affected zone, thermomechanically affected zone and stirred zone. In addition, the FeAl3 intermetallic compound was detected in the interface of the steel fragments and Al. (C) 2016 Elsevier B.V. All rights reserved.