Modelling of melting and solidification behaviour during laser spot welding

Abstract

It is well known that rapid solidification and fast cooling rates occur in pulsed laser spot welds. It is particularly difficult, but important, to determine various solidification parameters in terms of development of novel microstructure, prevention of welding defects, and improvement in mechanical properties. Therefore, in this study, a heat conduction and solidification model considering the effects of microsegregation and latent heat is developed to provide a reasonably good knowledge of rapid melting and solidification behaviour in such a spot weld. It was confirmed that the latent heat would greatly affect thermal histories during solidification and growth rates of cellular dendrite tips. Also, microsegregation models on the basis of the pseudobinary phase diagram are proposed for rapid solidification to obtain a better knowledge of thermal histories and growth rates of cellular dendrites. These models could be utilised to reveal variations in a molten pool and a mushy zone region during spot welding, and consequently to reduce cracking in laser spot welds of commercially available aluminium alloy.