Influence of Induced Convection on Transformation Kinetics During Rapid Solidification of Steel Alloys: The Retained Damage Model

Abstract

The Retained Damage Model successfully predicts the incubation delay during transformation from ferrite to austenite in the presence of an applied external flow field during rapid solidification of ternary stainless-steel alloys. The model incorporates two new features-conservation of the free energy associated with undercooling of the primary metastable phase, and use of a modified Read-Shockley approach to quantify defect energy induced by melt shear. Healing of the microstructure could reduce the amount of free energy retained, but, for the alloys considered in this work, it was found that the model is not sensitive to this phenomenon, and thus 100% of available free energy is retained to provide an additional transformation driving force, significantly shortening the incubation period. Use of a dimensionless approach allows comparison between systems with very different thermophysical properties, and highlights the similarity in response to local flow conditions over a wide range of compositions.