TWI

Defect free welded joints were fabricated in 5083-O aluminium alloy (Al, 4.3%Mg, 0.65%Mn) plates (thickness 20 mm) by friction stir welding (FSW) and the influence of tool geometrical features on their microstructures and structure properties relationship was investigated. Welding was performed using a "Triflat" design tool at a rotational speed of 500 rpm, travel speed of 50 mm/min and tool tilt angle of 3 deg. A 'stop action' weld specimen was obtained to study the individual effects of threads and flats in the tool. Microstructure and dislocation density distributions were observed by TEM, field emission SEM and electron backscatter diffraction. Microhardness was measured with a Vickers microhardness tester. Issues discussed include Orowan hardening parameters in the stir zone, thermomechanically affected zone (TMAZ) and HAZ, dynamic recrystallisation and structure properties deviation from the Hall-Petch relationship.

11th International Symposium, 17-19 May 2016, Poster Session, Paper 08