Improved model for static recrystallization kinetics of hot deformed austenite in low alloy and Nb/V microalloyed steels

Abstract

Using torsion tests a improved model has been constructed to predict the static recrystallization kinetics of deformed austenite in low alloy and microalloyed steels. The model quantifies the influence of the most common elements (C, Si, Mn, Mo) in low alloy steels and the typical elements (V, Nb) in microalloyed steels, when they are in solution. Activation energy (Q) is the parameter sensitive to the content and nature of each alloying element, and an expression for Q is shown as a function of the percentage of each one. Nb is the element that contributes most to increasing the value of Q, and thus that which most delays recrystallization kinetics. C is seen to be the only alloying element that contributes to lowering the value of Q, and thus to accelerating recrystallization kinetics. Extrapolation of the expression of Q to pure iron in the austenitic phase gives a value of 148 637 J mol-1, which is similar to other values found in the literature for the grain boundary self-diffusion energy of pure Feγ . Static recrystallization kinetics follow Avrami's law and expressions are given for the parameter t0.5 and the exponent n.