Gradient structure design to strengthen carbon interstitial Fe40Mn40Co10Cr10 high entropy alloys

In this work, gradient structure is successfully produced in the surface of FCC structured (Fe40Mn40Co10Cr10)C3.3 high entropy alloy (HEA) by using surface mechanical rolling treatment (SMRT). The depth of surface gradient layer with higher hardness increases with increasing the SMRT passes. The introducing of gradient layer not only significantly improves the strength of HEAs but also remains sufficient ductility. The ultra-high strength of the gradient structured HEA is mainly related to the synergetic strengthening mechanism, while the comparatively good ductility is ascribed to the back stress strain hardening mechanism. Gradient structure design provides a novel strategy for producing HEAs with high performance.