Nucleation Rate and Number of Precipitates in V and Nb-Microalloyed Steels

Abstract

Abstract. Recrystallization-precipitation-time-temperature (RPTT) diagrams were experimentally determined for two microalloyed steels with V and Nb, respectively, at a strain of 0.35 and a strain rate of 3.63 s -1 . From the RPTT diagrams, and applying the classic theory of nucleation, the nucleation rate was calculated for both steels. In order to determine the mentioned magnitudes, several parameters were calculated, such as: the Zeldovich factor (Z), the energy of formation of the nucleus (G), the driving force for precipitation (Gv), the critical radius for nucleation (Rc), and the dislocation density at the start of precipitation (), among others. The calculated data has made it possible to clarify the shape of precipitation start and finish curves and to plot the nucleation rate as a function of temperature. The number of precipitates was calculated by integration of the nucleation rate expression. In this way, substantial differences were established between the two types of microalloyed steels, including the final size of the V(C, N) and Nb(C, N) precipitates.

Correlative analysis of interaction between recrystallization and precipitation during sub-critical annealing of cold-rolled low-carbon V and Ti–V bearing microalloyed steels

“…The driving force for the formation of TiC particle is much higher than for VC because of the lower solubility of Ti in ferrite matrix than that of V [66]. The higher driving force for nucleation promotes finer critical radius for nucleation of precipitates [39,67,68]. Driven by the higher force, the simulated precipitation kinetics is much faster in the Ti+ grade than in the base grade.…”