Phase-field models offer the possibility of simulating the microstructure evolution under rapid solidification conditions without having to neglect the key physical mechanisms such as nucleation, growth kinetics, and solute diffusion which are active at a microscopic length scale. However, until now the phase-field simulations are mostly restricted to binary alloys owing to the complexity of obtaining thermodynamic descriptions for technical alloy compositions. This gap is bridged by the full coupling of phase-field evolution with a thermodynamic database with the TQ-interface of ThermoCalc. A new interpolation scheme, called pair-wise interpolation, guarantees numerical stability and offers significant improvements in computational efforts needed to simulate a multi-component alloy system. In this work, we employ 3-D phase filed simulations coupled to both mass and heat transport phenomena including the release of latent heat of solidification. The simulation studies are conducted for CMSX-4, which is a Ni-based superalloy with 10 chemical elements. A macroscopic CFD model is employed to obtain the heat fluxes at the boundaries (both the heat extraction rate and heat addition rate) which will act as accurate boundary conditions for the microscopic PF simulation model.