TWI

5A06 aluminium alloy (Al, 6.8%Mg, 0.5%Mn) sheets (thickness 5.17 mm) were joined by friction stir welding (FSW) and the microstructure and mechanical properties of the welded joints were investigated. Welding was performed using a tool pin with a screw thread shape at a traverse speed of 120 mm/min and rotational speeds of 400-800 rpm. Welded joint microstructure was observed by SEM and electron backscattered diffraction while precipitates and dislocations were examined by TEM. Mechanical properties were characterised by Vickers hardness measurements and room temperature tensile tests using a CSS-1110 universal testing machine. Issues discussed include the significant increase of Mg2Si rod-shaped precipitates with increasing rotational speed, the stirring effect of the pin in the thermomechanically affected zone at the advancing side and the effect of grain size on hardness.

12th International Symposium, 26-28 Jun 2018, Session 4B: Performance I, Paper 03