Two numerical models have been developed in order to simulate the reaustenitization from ferrite/pearlite microstructures in Fe-C steels. The first one describes the dissolution of pearlite which takes place just above the eutectoid temperature. It is based upon a two-dimensional finite element method and an adaptive mesh. The diffusion equation is solved in austenite (γ) for a typical domain representative of the periodic structure of ferrite (α) and cementite (θ) lamellae. The α/γ and θ/γ interfaces are allowed to move with respect to the local equilibrium condition including curvature effects via the Gibbs-Thomson coefficient. The model is able to predict the dissolution rate, the concentration field and the shape of the interface at different stages of the pearlite dissolution. The second model describes the transformation of proeutectoid ferrite into austenite which follows the pearlite dissolution in hypoeutectoid steels. The diffusion equation is solved for a domain representative of the α-γ grain structures, using a finite volume method based upon a hexagonal grid. The discrete α/γ boundary is represented by special interfacial elements which separate α-elements from γ-elements. This technique allows to handle the displacement of the interface while respecting the flux condition at the interface. Simulated microstructures showing the dissolution of ferrite regions in the austenite matrix are presented at different stages of the phase transformation. A reverse TTT-diagram calculated with this 2D model is compared with dilatometric measurements performed at the same heating rates.
