Scale-bridging phase-field approach for nucleation and microstructure evolution applied to the β to α phase transformation in pure titanium

Abstract

Modeling concurrent nucleation and growth in the phase-field framework on experimentally relevant length scales remains a significant challenge due to spatial resolution and driving force limitations. This work proposes a modeling framework that overcomes these challenges by integrating the explicit nucleation method within the recently developed high-driving force phase-field model to investigate the influence of the cooling rate on solid-state nucleation and growth. The model accurately captures the growth behavior of individual nuclei across varying length scales, and allows efficient one grid point nucleation without modifying the high driving force equation. To accommodate nanoscale nucleation within a mesoscale phase-field framework, the model incorporates an analytical subscale step accounting for critical nucleus growth to one grid point. The model was applied to the β to α transformation in extra pure titanium, for which a material-specific input parameter study was performed. Simulation results were compared to experimental results on the cooling rate dependence of transformation temperatures and mean grain sizes obtained through an Electron Backscatter Diffraction analysis of furnace-, air-, and water-cooled samples. The model's significance lies in extending the phase-field method's applicability to simulate nucleation on much larger length-scales than previously achievable, bridging the gap between simulation and experimental length-scales.

Keywords

• Phase-field modeling
• Nucleation
• High driving force
• Pure titanium
• EBSD