Microstructural modelling in friction stir welding of 2000 series aluminium alloys

¹ Department of Engineering, University of Cambridge, Trumpington St, Cambridge, CB2 1PZ, UK
² TWI, Granta Park, Cambridge, CB1 6AL, UK

Corresponding author: hrs@eng.cam.ac.uk

Received: 2 July 2004
Accepted: 5 November 2004

Abstract

Simple process models are applied to predict microstructural changes due to the thermal cycle imposed in friction stir welding. A softening model developed for heat-treatable aluminium alloys of the 6000 series is applied to the aerospace alloy 2014 in the peak-aged (T6) condition. It is found that the model is not readily applicable to alloy 2024 in the naturally aged (T3) temper, but the softening behaviour can still be described semi-empirically. Both analytical and numerical (finite element) thermal models are used to predict the thermal histories in trial welds. These are coupled to the microstructural model to investigate: (a) the hardness profile across the welded plate; (b) alloy softening ahead of the approaching welding tool. By incorporating the softening model applied to 6082-T6 alloy, the hardness profile of friction stir welds in dissimilar alloys is also predicted.