Pawan Tripathi1 Somnath Bhowmick1

1, Material Science and Engineering, IIT Kanpur, Kanpur, , India

Austenite (γ-Fe, face-centered cubic (FCC)) to ferrite (α-Fe, body-centered cubic (BCC)) phase transformation in steel is of great importance from the point of view of industrial applications. In this work, using classical molecular dynamics (MD) simulations, we study the atomistic mechanisms involved during the transformation of the ferrite phase from an austenite phase. The kinetics of the transformations, classified as martensitic and massive, is defined in terms of the interface mobility, which depends on the interface migration velocity and Gibbs free energy change. The simulations are performed by creating an FCC region, sandwiched between two BCC regions (interface formed
according to Nishiyama-Wasserman (NW) orientation relationship, with [110] of BCC oriented parallel to [111] of FCC) and studying how the former transforms into the later phase at elevated temperature, ranging from 1000 to 1400 K. Three configurations of BCC-FCC phase were created by tilting FCC phase with respect to z-axis with an angle of 3.11o , 4.04o and 5.77o from the ideal NW, resulting into formation of steps or disconnections at the interface. Using MD simulations, the effect of the tilt on interface velocities, mobilities and activation energy followed by the interface migration mechanism in each of the orientation will be discussed.