MODELING THE TITANIUM NITRIDE (TiN) GERMINATION AND GROWTH DURING THE SOLIDD7ICATION OF A MARAGING STEEL

摘要

A maraging steel containing nitrogen and titanium is considered. As solidification proceeds, the segregation accounts for an increase of Ti and N mass fraction in the liquid phase. This eventually leads to the formation of TiN if the supersaturation is high enough. A model has been developed to calculate the creation and evolution of the TiN distributions in both phases. Microsegregation is modeled using the lever rule, while the kinetics of precipitation is mainly driven by the supersaturation of the liquid bath. The model enables one to investigate the competition between segregation and precipitation regarding the solute concentrations and the shape of the particle size distributions in the liquid and solid phases. A parametric study on the solidification time reveals the existence of a maximal inclusion size. It also confirms the influence of the initial composition on the final size of TiN particles.