3D-FEM Modeling of Macrosegregation in Solidification of Binary Alloys

ABSTRACT: The paper presents a three-dimensional coupled numerical solution of momentum, energy and solute conservation equations, for binary alloy solidification. The mushy zone is modelled as a porous medium, saturated in liquid, following Darcy’s law. Microsegregation is governed either by lever rule or Scheil models. The resulting solute, momentum and energy transport equations are solved using the Streamline-Upwind Petrov/Galerkin method. All these equations are coupled but solved with a single staggered scheme. The full algorithm was implemented in the 3D finite element code THERCAST. Two applications cases are given: solidification of Sn-Pb and Pb-Sn alloys in a parallelepipedic cavity. Comparisons with experimental measurements and with two other simulation codes are made. Full 3D and pseudo-2D calculations are also compared. Finally the mesh size effect on the accuracy of the solution is discussed. KEY WORDS: macrosegregation, alloy solidification, 3D finite element