Crystallographic variant selection of martensite at high stress/strain

Abstract

The phenomenological theory of martensitic transformation is well understood that the displacive phase transformations are mainly influenced by the externally applied stress. Martensitic transformation occurs with 24 possible Kurdjomov-Sachs (K-S) variants, where each variant shows a distinct lattice orientation. The elegant transformation texture model of Kundu and Bhadeshia for crystallographic variant selection of martensite in metastable austenite at various stress/strain levels has been assessed in this present research. The corresponding interaction energies have also been evaluated. Encouraging correlation between model prediction and experimental data generation for martensite pole figures at many deformed austenite grains has been observed at different stress/strain levels. It has been investigated that the mechanical driving force alone is able to explain the observed martensite microtextures at all stress/strain levels under uniaxial tensile deformation of metastable austenite under low temperature at a slow strain rate. The present investigation also proves that the Patel and Cohen’s classical theory can be utilized to predict the crystallographic variant selection, if it is correctly used along with the phenomenological theory of martensite crystallography.

Keywords:

• stress-induced martensite
• strain-induced martensite
• variant selection
• interaction energy
• austenitic stainless steels
• tensile deformation

Acknowledgements

I am grateful to the Ministry of Science & Technology, Department of Science & Technology, Government of India for the BOYSCAST Fellowship. I express my sincere gratitude to Dr. S. Tarafder, Chief Scientist of CSIR-National Metallurgical Laboratory Jamshedpur, Professor P.C. Chakraborti, Department of Metallurgical and Material Engineering, Jadavpur University, Kolkata for their fruitful suggestions and discussions. Dr. S. Kundu, Head, Product Research Group, Tata Steel, Jamshedpur is also gratefully acknowledged for his help in programming and discussions. I am also grateful to Professor H.K.D.H. Bhadeshia for fruitful suggestions, stimulating discussions and the provision of the laboratory facilities at the Phase Transformation & Complex Properties Research Group, Department of Materials Science & Metallurgy, University of Cambridge, UK during the fellowship (2009–2010). I would also like to thank all the respected reviewers for their positive and constructive recommendations which helped a lot to prepare this revised manuscript.

Disclosure statement

No potential conflict of interest was reported by the author.