2008 Volume 48 Issue 11 Pages 1603-1608
The intragranular nucleation of ferrite has been studied in a V microalloyed steel (C=0.103; Mn=1.463; V=0.139; N=0.0100% mass). Using torsion tests and applying the double deformation method known as “back extrapolation”, the recrystrallised fraction of austenite has been determined for several deformation temperatures and two strain values (0.20 and 0.35) and has been plotted as a function of time. Recrystallisation-precipitation-time-temperature (RPTT) diagrams have then been drawn. The RPTT diagrams depict precipitation kinetics as a function of the temperature and time and this information has been used to study the intragranular nucleation of ferrite, cooling specimens from programmed temperatures and moments for which the precipitated volume and the average precipitate size (determined by TEM) are known. The results have allowed us to determine the contribution of intragranular nucleation to ferritic grain refinement, which was approximately 20%.