Fatigue and fracture behaviour of friction stir welded aluminium–lithium 2195

Abstract

Abstract Aluminium–lithium (Al–Li) alloys offer attractive properties for lightweight aerospace structures, due to their low density, high strength and fatigue crack growth resistance. Although there are many advantages with Al–Li alloys, limitations remain while using conventional joining techniques. Friction stir welding is a well-established solid-state joining process that is expected to reduce many of the concerns about Al–Li welding. The work presented in this paper involves the characterisation of the fatigue performance of the AA2195-T8X at room temperature. SN and crack growth tests of base material and friction stir welded 5 mm thick specimens were performed. During crack growth tests, three different R ratios (minimum remote stress/maximum remote stress), 0.1, 0.5 and 0.8, were used per each three different material conditions: base material, heat affected zone (HAZ), and weldment. M(T) specimens containing notches at the centre of the weld, at the HAZ and at the base material, were tested. The fatigue crack growth specimens were left with an un-cracked ligament for final evaluation of fracture toughness. Novel results are presented for fatigue crack growth and toughness on T–L orientation. The results for SN fatigue behaviour, fatigue crack growth and toughness of the studied alloy and its friction stir weldments present high values when compared with data found in the literature.