THEORY OF BAINITIC TRANSFORMATION: A MODEL WITH COUPLED FIRST-ORDER PHASE TRANSFORMATIONS

We devise a Ginzburp-Landau theory for bainitic transformation, which contains two first-order phase transformations, one being reconstrvctive represented by the diffusional proeutectoidal precipitation of ferrite, and the other the displacive tronsformation. It provides a coupled mechanism for the formation of bainite. With the numerical simulation results, a diffusion-induced nucleation and a diffusion-accompanied growth of displacive transformation were suggested. This theory can be helpful to overthrow the thermodynamic difficuity of displacive transformation above the Ms temperature, and also heopful to understand the Bs temperature, the partial sapersaturation,the single variation of bainitic carbides, and the incomplete-reaction phenomenon of bainitic transformation, etc.