TWI

In relation to the occurrence of abnormal grain growth in aluminium alloy spun formed dome development using friction stir welded (FSW) blanks, an investigation is presented into tensile tests performed on two AA 2195 (Al, 4%Cu, 1%Li) FSW parameter sets to examine the effects of post weld annealing treatment on the forming range and strain hardening exponent. Conventional FSW was employed to join test pieces, creating the spin forming blank. Weld nugget grain size was determined by electron backscatter diffraction using an FEI Quanta 600F field emission SEM. Weld hardness was measured with a microhardness tester. Tensile testing was performed at 200 deg.C on specimens with a double reduced gauge section, and the strain hardening exponent was evaluated from the true stress-true strain diagram. Nugget zone microstructure was observed by optical microscopy. The effect of salt bath solution heat treatment on grain size reduction and arrest of abnormal grain growth is discussed.

9th International Symposium, 15-17 May 2012, Session 7B: Metallurgy, Paper 02