热变形条件下C-Mn钢奥氏体→铁素体相变模拟

MODELING OF SUBSEQUENT FERRITE FORMATION IN C-Mn STEEL AFTER AUSTENITE HOT DEFORMATION

为了定量考虑热变形对普碳钢奥氏体向铁素体转变的影响,计算了热变形的C-Mn钢中的位错密度和变形储存能.在计算变形奥氏体向铁素体的平衡转变温度时,将计算所得变形储存能加在母相γ的能量项中,从而使变形奥氏体向铁素体转变的平衡转变温度Ae3提高,在本工作的热变形条件下,变形储存能为10-20.J/mol,使平衡转变温度Ae3提高1.0K左右,因而相同的冷却条件下奥氏体向铁素体转变的实际温度Ar3也会提高、从γ/α界面移动速度控制铁素体生长速度角度的计算表明,奥氏体中储存能△Gdef使相变驱动力△Gγ→α增加,使铁素体的长大速度增加,加速奥氏体向铁素体的转变过程,但长大速度并未发生数量级的变化.在连续冷却相变模拟的过程中,利用超组元模型计算相变的平衡参数。

The dislocation density and stored energy of hot deformation were calculated to evaluate quantitatively the effect of hot plastic deformation of austenite on the kinetics of subsequent ferrite transformation. Due to stored energy, the gamma --> alpha equilibrium transformation temperature A(e3) increases to a higher temperature. Under the hot deformation conditions tested, the modeled stored energy is approximately 10-20 J/mol, and the equilibrium temperature A(e3) increases about 10 K, so the practical start transformation temperature moves to higher temperature region. The total driving force DeltaG(gamma-->alpha) of transformation is increased due to the additional stored energy DeltaG(def) too, so the move velocity of the gamma/alpha-interface is quickened. The growth velocity of ferrite increases, which accelerates the transformation progress of ferrite. The equilibrium parameters were calculated by use of super-elements lattice model in continuously cooling. Compared with the results measured in published literature, the modeled transformation dynamics of subsequent ferrite of C-Mn steel after austenite hot deformation agrees well with the measured results.