3D phase-field computations of microsegregation in nodular cast iron compared to experimental data and Calphad-based Scheil-prediction

Abstract

The redistribution of solute elements during processing of a nodular cast iron alloy was simulated for the first time comprehensively over time and 3D space. Numerical predictions had so far been limited to 1D models, neglecting local morphological aspects and commonly also diffusion and growth in solid-state. Application of the standard multi-phase-field method was hindered by the inherent simplifying assumption of equal and constant molar volume, causing artificial piling-up of solute and biased kinetics during modelling of graphite growth. A recently developed volumetric multi-phase-field approach now accounts for the changing partial molar volume of the individual elements. The Calphad-based phase-field study was benchmarked to experimental cooling and nodule density data, and the predicted as-cast distributions were validated by experimental segregation analysis. The combined numerical and experimental findings were furthermore used as a basis to discuss simplifying assumptions commonly made in 1D Scheil-type models.