Nucleation of intragranular ferrite at Ti 2O 3 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 Ti 2O 3 particles, which are thermodynamically stable in the steels. From a steel–Ti 2O 3 diffusion bonding experiment, it is clearly observed that a local Mn-depleted zone (MDZ) has developed in the vicinity of the steel–Ti 2O 3 interface. The MDZ formation around Ti 2O 3 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 Ti 2O 3 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 Ti 2O 3 particles.