THREE DIMENSIONAL TRANSIENT FINITE ELEMENT ANALYSIS FOR SOLIDIFICATION MICROSTRUCTURE AND THERMAL STRESSES IN MULTI-PASS LASER AIDED DMD PROCESS

摘要

Despite enormous progress in Laser Aided DirectMetal/Material Deposition (DMD) process manyissues concerning the adverse effects of processparameters on the stability of variety of propertiesand the integrity of microstructure have beenreported. Traditional solidification theories as theyapply to castings or related processes areinappropriate in describing solidification in highenergy beam processes involving significantly greatercooling rates. A complete model that provides aquantitative relationship between process parameters,temperature history, phase transformation kinetics,solidification parameters such as temperaturegradient, growth rate, resultant interfaceundercooling, and the thermal residual stresses alongwith the deposited material microstructure is highlydesirable. The focus of this paper is the solutetransport in multi-pass DMD process, especially thecoupling of the process scale transport with thetransport at the local scale of the solid-liquidinterface. This requires modelling of soluteredistribution at the scale of the secondary armspacing in the dendritic mushy region. This paper isan attempt towards a methodology of finite elementanalysis for the prediction of solidificationmicrostructure and macroscopic as well asmicroscopic thermal stresses in this process. Thecomputer simulation is based on the metallo-thermomechanicaltheory and finite element analysis forcoupled temperature, solidification, phasetransformation and stress/strain fields, and comparedwith experiments to verify the model.