Bi-directional ferrite to austenite transformation through warm temperature deformation of a ferrite-based low density steel

Abstract

The Gibbs energy model as an effective thermodynamic function along with detailed microstructural analyses were employed to assess the capability of strain induced transformations in a ferrite based lightweight steel. In this respect, the material was deformed in a warm temperature regime in compression mode and the resultant microstructures were studied in details. The progressive and extensive development of the banded structure was led to the partitioning of the ferrite phase and also the shearing of the parent austenite. The shear strain localization was effectively released through simultaneous transformation of ferrite to austenite and austenite to ferrite transformations as an effective strain compensation mechanism. This was led to appreciable flow softening in corresponding flow curves. The capability for bidirectional transformation resulted from the specified local elemental partitioning of Al and Mn and the resultant exactly same levels of Gibbs energies of each constituent phases.