The mechanism of intragranular ferrite formed on Ti-rich (Ti,V)(C,N) precipitates in the coarse heat affected zone of a V-N-Ti microalloyed steel

The effect of Ti-rich (Ti,V)(C,N) precipitates on the evolution of intragranular ferrite in the coarse grain heated effected zone (CGHAZ) of V-N-Ti steel was systematically investigated via transmission electron microscopy. The coarse grain boundary ferrite, bainite, and ferritic side-plates in simulated CGHAZ were replaced by polygonal ferrite and acicular ferrite, when the nitrogen content was increased from 0.0044 wt% to 0.0094 wt%. In addition, the undissolved Ti-rich core acted as a nucleation site for the V-rich cap; the cap reached the critical size at which nucleation of intragranular ferrite occurs nucleation size of intragranular ferrite with the aid of the core. Owing to a cap-induced increase in the nucleation potency, the intragranular ferrite have formed on the Ti-rich (Ti,V)(C,N) hold the Baker-Nutting orientation relationship ((001)(IGF)//(001)((Ti,V)(C,N)), [110](IGF)//[100]((Ti,V)(C,N))). (c) 2016 Elsevier B.V. All rights reserved.