Prediction and validation of temperature distribution and material flow during refill friction stir spot welding of AZ91D magnesium alloy

Abstract

Temperature distribution and material flow behaviours during refill friction stir spot welding (RFSSW) of AZ91D magnesium alloy were studied by a combination of numerical modelling and experimentation. The coupled Eulerian–Lagrangian (CEL) formulation was adopted to analyse processing thermal history and plastic deformation mechanisms of the RFSSW joint more accurately. Welding thermal cycles of varying positions in joint were measured by thermocouples so as to validate accuracy of this simulation process. The FEA (Finite Element Analysis) simulation to cover mechanical results was found to be consistent with the experimental values. Moreover, simulation analysis presented that material flow caused the clear hook defects and bonding ligament, and such material flow behaviours were experimentally verified via the macrostructure and microstructure of the RFSSW joint.