The mechanism of bcc alpha ' nucleation in single hcp epsilon laths in the fcc gamma -> hcp epsilon -> bcc alpha ' martensitic phase transformation

XS Yang and S Sun and TY Zhang, ACTA MATERIALIA, 95, 264-273 (2015).

DOI: 10.1016/j.actamat.2015.05.034

High Resolution Transmission Electron Microscopy (HRTEM) and Molecular Dynamics (MD) simulations were conducted here to study the plastic deformation induced gamma (fcc) -> epsilon (hcp) -> alpha' (bcc) martensitic transformation in 304 stainless steels for the alpha' nucleation from single hcp-epsilon laths. Results elucidate that the underlying microscopic mechanism for the alpha' nucleation from single hcp-epsilon laths obeys the Bogers Burgers-Olson-Cohen "3T/8-T/3" model. In particular, the atomic-scale observations clearly show the Kurdyumov- Sachs (K-S) lattice orientation relation (OR) and Pitsch OR at the gamma/alpha' interfaces, the lattice rotation inside an alpha' martensitic inclusion, the transition lattice and the reverse shear- shuffling induced continuous lattice elastic deformation at the diffuse epsilon/alpha' interface, which caters the 3T/8 and T/3 shears and sheds atomic process insight into the mechanism of the martensitic transformation. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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