Materials, Methods & Technologies, Volume 14, 2020

Abstract: A finite element method (FEM) was developed to predict macrosegregation during alloys solidification with columnar structure. A fractional step method was employed to solve the thermosolutal convection in the mushy zone with a damping convection. The velocity and pressure were decoupled and interpolated by equal-order linear triangular elements. The time derivative terms were discretized by a fully implicit Euler backward method. The convection-diffusion equations of energy, solute and momentum were spatially discretized by the consistent SUPG method, and the terms of convection, diffusion, pressure gradient, Darcy drag, and buoyancy were integrated using the second-order Crank-Nicolson method. A solution procedure was designed to couple the resolutions of conservations of energy, solute and momentum, as well as the microsegregation model at an overall computational efficiency and accuracy. The FEM was applied to predict macrosegregation during solidification of Pb-18wt%Sn alloy in a rectangular mold. The macrosegregation maps, temperature fields, velocity fields and liquid fraction fields, as well as evolutions of liquid fraction, average mass concentration and velocity magnitude were presented.