Martensitic transformation can easily induce a maximum hardness value of 800–900 HV (Vickers hardness) for steels with carbon contents of 0.6 wt.% and above. However, the occurrence of martensitic transformation in pure iron requires exceptionally high cooling rates (105 –106 °C/s), and the maximum achievable hardness is only about 150 HV. Here we report an extreme hardness of 830 HV in pure iron obtained through high pressure induced martensitic transformation at a rather slow cooling rate of just 10°C/s. This unprecedented strength originates from the formation of twin-related martensitic laths with an average thickness of 3.8 nm.
Bibliographical note© 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
- high pressure
- Martensitic transformation
- nanotwinned martensite
- pure iron