Effect of Friction Stir Processing on Fusion Welded Joint of Al-5083

Tungsten Inert Gas Welding (TIG) is the most preferred joining process for aluminum alloys, but it produces weld joint having inferior mechanical property in comparison with base metal because of inherent limitations of the process. To improve the mechanical properties, the weld is post processed by friction stir processing (FSP) upto depth of 2mm. This paper presents the effect of performing FSP on autogenous TIG welded butt joint of Al-5083, 6mm thick plate. Mechanical and metallurgical properties of both processed and unprocessed autogenous TIG weld are compared. Characterisation techniques adopted to evaluate weld joint are tensile test, microhardness measurement, microstructural examinations and SEM analysis. Tensile strength of autogenous TIG weld joint is lowered by 6.5% compared to base metal because of presence of micro porosities in the weld metal. Friction stir processing produces the fine grain refined structure, marginally improves the tensile strength of the autogenous TIG weld joint by 2.7%. Microhardness of the autogenous TIG weld metal of the surface is raised from 163.6 HV to 298 HV after performing FSP. However, SEM images of fractured surface of friction stir processed specimen reveals fine dimpled structure which indicates that ductility of the weld joint remain unaffected after performing FSP on autogenous TIG weld joint.