Prediction of microstructures in laser welding of stainless steel AISI 304

A mathematical model is proposed to investigate the evolution of microstruc tures due to rapid solidification in laser materials processing. The instab ility of solid-liquid interface is analyzed by considering the diffusion pr ocess and perturbation method. The results of this model show that the neut ral stability curve is largely dependent on solidification rate and partiti on coefficient. The decay, periodic oscillation, and growth of the perturba tions at the solid-liquid interface can be regarded as planar, cellular and dendritic microstructures, respectively. Laser spot welding experiments we re conducted for stainless steel AISI 304 to verify the theoretical predict ions. (C) 1999 Laser Institute of America. [S1042-346X(99)00102-3].