Mechanical and micro structural behavior of 2024–7075 aluminium alloy plates joined by friction stir welding

The aim of the present work is to investigate on the mechanical and micro structural properties of dissimilar 2024 and 7075 aluminium plates joined by friction stir welding (FSW). The two plates, aligned with perpendicular longitudinal directions, have been successfully welded; successively, the welded plates have been tested under tension at room temperature in order to analyse the mechanical response with respect to the parent materials. The fatigue endurance (S-N) curves of the welded joints have been achieved, since the fatigue behaviour of light welded plates is the best performance indicator for a large part of industrial applications; a resonant electromechanical testing machine load and a constant load ratio R=σ_min/σ_max=0.1 have been used at a load frequency of about 75 Hz. The resulted microstructure due to the FSW process has been studied by employing optical and scanning electron microscopy either on `as welded´ specimens and on tested specimen after rupture occurred.