Fundamental Research on Evolution of TiN in Fe–Al–Ti–O–N Alloy During Isothermal Holding

Different from previous work, evolution of shape, size distribution, total number density, and distribution characteristic of TiN was systematically investigated in Fe–Al–Ti–O–N alloy with a low concentration of alloying elements during isothermal holding at 1273 K and 1573 K. The holding time varied from 0.5 to 12 hours. TiN was saturated in each alloy, and it was separated from oxides prior to thermal holding. TiN > 0.5 μ m was analyzed by automatic SEM-EDS. The results show that the size of TiN follows lognormal distribution in each alloy. Thermal holding is invalid to modify the cuboid shape of TiN; it enhances the concentration of large TiN on the grain boundary of alloy. Oswald ripening of TiN is not apparent in any alloy during thermal holding at either holding temperature. The relation between the average size of TiN and the holding time does not conform to the LSW equation. Size distribution of TiN during thermal holding is comprehensively affected by the supersaturation degree of TiN, the molar ratio of Ti/N in alloy, the original distribution of TiN in as-cast alloy, and the holding temperature and time. The fundamental information obtained contributes to building the database to predict the distribution of TiN in steel during the whole manufacturing process.