Simulation of microsegregation and microstructural evolution in directionally solidified superalloys

A two-dimensional model for solidification and secondary phase precipitatio n in directionally solidified superalloys is presented, which makes use of a shape function approximation for the isothermal cross-section of the prim ary dendrites, The phase boundary is represented by a diffuse interface on a finite difference grid, as in phasefield methods, Thus, two-dimensional m ulticomponent diffusion can be calculated for all phases. Via a Fortran int erface, the model is coupled to thermodynamic databases assessed using the 'calculation of phase diagrams' (Calphad) approach. In this way, for each t ime step actual data are available for partitioning, dendritic growth, and nucleation of secondary phases. The model is applied to Ni-Al-Cr as a terna ry model system and to the commercial superalloy IN706. MST/4802.