Nucleation of intragranular ferrite at Ti2O3 particle in low carbon steel

Systematic experiments have been performed to study the intragranular nucle ation phenomena of ferrite in Ti-bearing low carbon steels. The fine intrag ranular acicular ferrite structure in Ti-bearing low carbon steels is induc ed by heterogeneous nucleation of ferrite plates at fine dispersed Ti2O3 pa rticles, which are thermodynamically stable in the steels. From a steel-Ti2 O3 diffusion bonding experiment, it is clearly observed that a local Mn-dep leted zone (MDZ) has developed in the vicinity of the steel-Ti2O3 interface . The MDZ formation around Ti2O3 particles is believed to be a dominant dri ving force for the heterogeneous nucleation of intragranular ferrite. It is also confirmed that the development of the MDZ is associated with the abso rption of Mn into the Ti2O3 phase at high temperatures. The width of the MD Z decreases with decreasing bonding (austenitizing) temperature and influen ces greatly the intragranular nucleation ability of acicular ferrite at Ti2 O3 particles. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.