Christophe Desrayaud

Integrated modelling of precipitation during friction stir welding of 2024-T3 aluminium alloy

Abstract The microstructure and hardness profiles across a friction stir welded joint of a 2024-T3 aluminium alloy have been simulated by thermal and microstructure models. Thermal modelling is based on a semi-analytical model, which analyses the complex material flow by standard velocity fields. The precipitation model is based on classical nucleation, growth and coarsening mechanisms and can be combined with precipitation hardening laws. Applying these models in succession gives simulated hardness profiles, which have been compared to experimental hardness values after friction stir welding under equivalent conditions. The positions of maximum and minimum hardness are well reproduced, but the simulated hardness variation across the weld is less pronounced than the experimental one. The simulated microstructures in well characterised zones of the joint have been compared to previous TEM observations and shown to be generally in agreement. The results demonstrate the feasibility of making realistic hardness predictions from physically based models on a standard personal computer.

Two dimensional Coupled Eulerian Lagrangian (CEL) model for banded structure prediction in friction stir welding with trigonal tool

A finite element model has been developed by means of a coupled Eulerian-Lagrangian approach. The banded structure which is related to the periodical material deposition is predicted in two dimensions as the experimental investigation shows that, during FSW with trigonal tool, the material flow operates mainly in the welded plates plan.