Characterization of clusters and ultrafine precipitates in Nb-containing C-Mn-Si steels

Atom probe tomography was used to characterize the composition, sizes and distribution of Nb-, Fe-, Mo- and C-containing clusters and fine particles in thermomechanically processed CMnSi transformation induced plasticity steels, alloyed with Nb, Mo and/or Al. Nb-containing clusters and fine particles were detected in all the phases. The presence of C-rich clusters and significant increase of cluster density indicated that further decomposition of supersaturated retained austenite took place during isothermal hold at 450-500 °C.