Plastic strain-induced sequential martensitic transformation

In contrast with pseudo-elasticity, martensite induced by plastic straining is known to exhibit limited further transformability and reversibility. The mechanistic and atomistic nature of a face-centered cubic (FCC)-hexagonal close-packing (HCP)-FCC sequential martensitic transformation pathway is investigated. Both transformations exhibit in the plastic realm and contribute to the observed strain hardening. In-situ electron microscopy and synchrotron diffraction verify that the final FCC-phase demonstrates strain accommodation capability. The random emission of Shockley partials in the HCP-martensite is identified as the most plausible atomistic mechanism for the second transformation, which renders a latent potential to dynamically mitigate stress concentration, enhancing strain hardenability. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.