High pressure induced ultra-hard twinned lath martensite in binary Fe-15wt.%Cr alloy

Abstract Under high pressure of 4 GPa, cooling at 10 °C/s from 1050 °C to ambient temperature induces unprecedented hardening by a factor of 4 (600 HV) in a binary Fe-15 wt.%Cr alloy that is traditionally unable to be hardened via heat treatment. A martensite of body centered cubic structure was induced, having the common features of hierarchical packet-block-lath structure of lath martensite in ferrous alloys, but with substructure of high density of twinned variants (lath) of 31 nm in average thickness. This study allows good combination of hardening and high temperature oxidation resistance in binary Fe-Cr system without alloying extra elements.