TWI

An investigation was undertaken to examine the effects of high welding speed and the use of thermal boundary conditions during friction stir welding (FSW) on the mechanical properties of AA 7050 aluminium alloy weldments. FSW experiments were performed on AA 7050-T7451 plates (thickness 6.4 mm) at a welding speed of 6.8 mm/s, tool rotation rate of 480 rpm and forge force of 37.8 or 33.3 kN. Both active and passive thermal boundary conditions were employed to facilitate heat extraction from the weld zone. Preheating comprised tempering or solution heat treatment, while PWHT (24 h at 121 deg.C or 10 h at 121 deg.C followed by 3 h at 163 deg.C) was designed to increase strength in the weld nugget while minimising HAZ and parent metal over-ageing. Mechanical properties were characterised by Vickers microhardness measurements, transverse tensile testing, residual stress measurement, and exfoliation and intergranular corrosion resistance testing.

9th International Symposium, 15-17 May 2012, Session 3A: Weld Performance, Paper 02