Interstitial strengthening of a f.c.c. FeNiMnAlCr high entropy alloy

The effects of adding boron or carbon on the microstructure and room-temperature mechanical properties of a new single-phase f.c.c. high entropy alloy Fe40.4Ni11.3Mn34.8Al7.5Cr6 are presented. Remarkably, 1.1 at% carbon in solution not only increases the yield strength (by a factor of 2), but also increases the elongation to failure (from ~41% to 50%) and the work-hardening rate. Surprisingly, the latter increases with increasing strain up to a strain of 35%. When fine-grained (4.7 µm), the C-doped HEA exhibits a yield strength of 557 MPa.