Melting and Resolidification of Direct Metal Laser Sintering with Multiscale Nonequilibrium Model

A multiscale numerical model based on the nonequilibrium thermal effect for melting and resolidification of direct metal laser sintering with a moving laser beam is developed. The effects of surface tension, buoyancy, and permeability as well as volume shrinkage due to the density change are taken into account. The finite volume method was used in this nonequilibrium model, and the nonequilibrium model is solved numerically using the SIMPLE algorithm method with iterative tridiagonal matrix algorithm. The surface temperature distributions and shapes of top surface, liquid-upper mushy, upper mushy-lower mushy, and lower mushy-solid interfaces are investigated. The results show that, during the melting progress, the liquid region, upper mushy zone, and lower mushy zone are formed on the top of unsintered zone. The parametric study shows that the top surface, liquid-upper mushy, upper mushy- lower mushy, and lower mushy-solid interfaces become lower with increasing laser intensity, increasing initial porosity, or decreasing scanning velocity.