Strength and ductility synergy induced by Al/C addition in low cost high entropy alloy

The effect of C and Al alloying on microstructure, mechanical properties and deformation mechanism of Fe40Mn40Ni10Cr10 low-cost high-entropy alloy was investigated. It was found that addition of 8 at. % Al and 2 at.% C resulted in the formation of M7C3 particles distributing at the grain boundaries of face-centered cubic matrix, in recrystallized state of Fe36Mn36Ni9Cr9Al8C2 alloy. More importantly, synergistically improved strength and ductility was obtained in the Al/C co-alloyed Fe36Mn36Ni9Cr9Al8C2 alloy. The yield strength and ultimate strength was notably enhanced from 329 MPa and 617 MPa to 421 MPa and 852 MPa, along with ductility improved from 39% to 44%. The improved strength was attributed to the solid solution strengthening originated from addition of Al with large atom size and interstitial C. The Al/C co-alloying induced activation of microbands formation during plastic deformation was responsible for the enhanced strain hardening capability and improved ductility.