The Investigation Of Numerical Simulation Of The Effect Of Deformation On γ→α Transformation And Deformation-induced γ→α Transformation

In the new century, the great improvements in both strength and toughness of steel are required stringently with cost reduction. The best way to realize this aim is to strengthen materials by means of low-carbon, microalloyed and refining grain. With controlling the time-temperature-deformation procedures during hot rolling, microstructure is refined as the result of the cooperation of recrystallization, austenite transformation and strain-induced precipitation. Refined grain, even ultrafined ferrite grain can be produced by transformation when deformed. The effect of deformation on ferrite transformation of HSLA steel is investigated at the temperature range of austenite non-recrystallization. A model is constructed for transformations in deformed austenite during continuous cooling. In the model, the transformations of ferrite, pearlite and bainite are included.In present paper, the effect of deformation on ferrite transforming is analyzed from the aspects of nucleation and growth of ferrite. As well known, grain boundary of austenite is the nucleation site of ferrite. With deformation, the nucleation of ferrite is thought to be at deformation bands beside grain boundary. Therefore, boundary area is replaced by effective boundary area as nucleation sites. On the other hand, the deformation store energy is also taken into account in thermodynamic calculation.In the model, the software Thermo-Calc is used to calculate thermodynamic data. The ferrite transforming kinetics model is based on Cahn's transformation kinetics theory and Scheil's additivity rule. The pearlite and bainite transformation kinetics model are suggested on the presumption of nucleation sites saturation. The simulations of different experiments...