Assessment of the thermodynamic dimension of the stacking fault energy

Abstract

Especially with respect to high Mn and other austenitic TRansformation and/or TWinning Induced Plasticity (TRIP/TWIP) steels, it is a current trend to model the stacking fault energy of a stacking fault that is formed by plastic deformation with an equilibrium thermodynamic formalism as proposed by Olson and Cohen in 1976. In the present paper, this formalism is critically discussed and its ambiguity is stressed. Suggestions are made, how the stacking fault energy and its relation to the formation of hexagonal ϵ-martensite might be treated appropriately. It is further emphasized that a thermodynamic treatment of deformation-induced stacking fault phenomena always faces some ambiguity. However, an alternative thermodynamic approach to stacking faults, twinning and the formation of ϵ-martensite in austenitic steels might rationalize the specific stacking fault arrangements encountered during deformation of TRIP/TWIP alloys.

Keywords:

• TWIP
• TRIP
• deformation twinning
• stacking fault
• stacking fault energy
• ϵ-martensite

Acknowledgements

The authors thank O. Fabrichnaya for very helpful comments and interesting discussions.

Notes

The author A. Kauffmann acknowledges the German Research Foundation (DFG) for funding under Grant No FR1714/5-1. Further the author S. Martin acknowledges the DFG for funding by the SFB 799 ‘TRIP-Matrix-composites’.