Nucleation of intragranular ferrite at Ti2O3 particle in low carbon steel

Abstract

Systematic experiments have been performed to study the intragranular nucleation phenomena of ferrite in Ti-bearing low carbon steels. The fine intragranular acicular ferrite structure in Ti-bearing low carbon steels is induced by heterogeneous nucleation of ferrite plates at fine dispersed Ti2O3 particles, which are thermodynamically stable in the steels. From a steel-Ti2O3 diffusion bonding experiment, it is clearly observed that a local Mn-depleted zone (MDZ) has developed in the vicinity of the steel-Ti2O3 interface. The MDZ formation around Ti2O3 particles is believed to be a dominant driving force for the heterogeneous nucleation of intragranular ferrite. It is also confirmed that the development of the MDZ is associated with the absorption of Mn into the Ti2O3 phase at high temperatures. The width of the MDZ decreases with decreasing bonding (austenitizing) temperature and influences greatly the intragranular nucleation ability of acicular ferrite at Ti2O3 particles. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.