NUMERICAL-MODEL FOR DENDRITIC SOLIDIFICATION OF BINARY-ALLOYS

A finite element model capable of simulating solidification of binary alloys and the formation of freckles is presented. It uses a single sy stem of equations to deal with the all-liquid region, the dendritic re gion, and the all-solid region. The dendritic region is treated as an anisotropic porous medium. The algorithm uses the bilinear isoparametr ic element, with a penalty function approximation and a Petrov-Galerki n formulation. Numerical simulations are shown in which an NH4Cl-H2O m ixture and a Pb-Sn alloy melt are cooled. The solidification process i s followed in time. Instabilities in the process can be clearly observ ed and the final compositions obtained.