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

In recent years, there has been renewed interest in the role of non-metalli c inclusions in controlling the microstructure of steels. The: potency of v arious inclusions and precipitates such as SiO2. MnO . SiO2, MnS, Al2O3, Ti 2O3 and VN for the nucleation of intragranular ferrite has been examined in the present study. Among them, single SiO2, MnOSiO2, Al2O3. TiN and MnS pa rticles seem to be inert to the nucleation of intragranular ferrite under t he present experimental condition. Ti2O3 particles in a Mn-containing steel are very effective for the nucleation of intragranular ferrite. being (Ti, Mn)(2)O-3 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 pot ent for the nucleation of intragranular ferrite. The decrease in transforma tion temperature causes a change in the morphology of intragranular ferrite from idiomorphic ferrite to acicular ferrite. (C) 2001 Published by Elsevi er Science Ltd on behalf of Acta Materialia Inc.