MODELING OF MELTING AND SOLIDIFICATION BEHAVIOR DURING LASER SPOT-WELDING

It is well known that rapid solidification and fast cooling rates occu r in pulsed laser spot welds. It is particularly difficult, but import ant, to determine various solidification parameters in terms of develo pment of novel microstructure, prevention of welding defects, and impr ovement in mechanical properties. Therefore, in this study, a heat con duction and solidification model considering the effects of microsegre gation and latent heat is developed to provide a reasonably good knowl edge of rapid melting and solidification behaviour in such a spot weld . It was confirmed that the latent heat would greatly affect thermal h istories during solidification and growth rates of cellular dendrite t ips. Also, microsegregation models on the basis of the pseudo-binary p hase 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 legion during spot welding, and consequently to reduc e cracking in laser spot welds of commercially available aluminium all oy.