Ferrite nucleation potency of non-metallic inclusions in medium carbon steels Original Research Article

In recent years, there has been renewed interest in the role of non-metallic inclusions in controlling the microstructure of steels. The potency of various inclusions and precipitates such as SiO2, MnO·SiO2, MnS, Al2O3, Ti2O3 and VN for the nucleation of intragranular ferrite has been examined in the present study. Among them, single SiO2, MnO·SiO2, Al2O3, TiN and MnS particles seem to be inert to the nucleation of intragranular ferrite under the present experimental condition. Ti2O3 particles in a Mn-containing steel are very effective for the nucleation of intragranular ferrite, being (Ti,Mn)2O3 particles by absorbing Mn atoms from a steel matrix. On the other hand, Ti2O3 particles in a Mn-free steel are not effective. MnS and Al2O3 particles in high nitrogen steels containing vanadium also appear to be potent for the nucleation of intragranular ferrite. The decrease in transformation temperature causes a change in the morphology of intragranular ferrite from idiomorphic ferrite to acicular ferrite.