Role of disconnections in mobility of the austenite-ferrite inter-phase boundary in Fe

TL;DR

This study uses molecular dynamics simulations to explore how disconnections at the austenite-ferrite boundary influence phase transformation mechanisms and boundary mobility in steel.

Contribution

It reveals that disconnections serve as nucleation sites and characterizes boundary mobility with Arrhenius behavior across a temperature range.

Findings

Disconnections act as nucleation centers for ferrite.

Phase transformation occurs via massive transformation mechanism.

Boundary mobility follows Arrhenius behavior with specific activation energies.

Abstract

Austenite ({\gamma}-Fe, face centered cubic (FCC)) to ferrite ({\alpha}-Fe, body centered cubic (BCC)) phase transformation in steel is of great significance from the point of view of industrial applications. In this work, using classical molecular dynamics simulations, we study the atomistic mechanisms involved during the nucleation and growth of the ferrite phase embedded in an austenite phase. We find that the disconnections present at the inter-phase boundary can act as the nucleation centers for the ferrite phase. Relatively small interface velocities (1.19 - 4.67 m/s) confirm a phase change via massive transformation mechanism. Boundary mobilities obtained in a temperature range of 1000 to 1400 K show an Arrhenius behavior, with activation energies ranging from 30 - 40 kJ/mol.