Modelling of heat flow phenomena in friction stir welding of aluminium alloys

摘要

In the present investigation a 2-D numerical heat flow model for friction stir welding (FSW) of aluminium alloys has been developed, based on the finite difference approach. The algorithm is implemented in MatLab 5.1, and calculates the thermal programme in butt welds for fixed starting conditions. The results show that the temperature in front of the tool is most critical, since the parent material must be pre-heated to a certain temperature before it can sustain the plastic deformation. The heating rate is, in turn, determined by the applied heat input and the geometry of the aluminium plate. In practice, this imposes restrictions on the welding speed v and the net power q0 for a given plate thickness d to avoid surface defects or excessive HAZ softening. At pseudo-steady state the different welding variables cna be combined in a single process parameter, q0/vd [kJ/mm~2], which controls the thermal programme during FSW.