FATIGUE CRACK GROWTH BEHAVIOUR OF FRICTION STIR WELDED 7075-T651 AND 6082-T6 ALUMINIUM ALLOYS

Abstract

Friction stir welding (FSW) is a solid-state welding procedure. It has become an alternative approach towards joining high strength alloys, such as aluminium alloys that were considered difficult to join using conventional welding techniques. In this experimental work, a comparative study of fatigue crack growth behaviour has been conducted between friction stir welded aluminium alloys 7075-T651 and 6082-T6. Fatigue crack growth rates are obtained in different locations of welds, such as nugget zone, heat affected zone and base material. Tensile testing results showed that the friction stir welded material is having less strength and ductility as compared to the base material for both the alloys but fatigue crack growth testing showed enhanced crack growth rate in the friction stir welded material as compared to heat affected zone and base material. The AA6082-T6 showed more fatigue crack growth resistance than AA7075-T651. Distinct features in microstructures of the welded joints are shown using optical microscopy and scanning electron microscopy. Chemical composition in different location of welds is determined by Energy dispersive X-Ray analysis.