Effect of carbon upon mechanical properties and deformation mechanisms of TWIP and TRIP-assisted high entropy alloys

The present work systematically investigates the effect of carbon upon a TWIP alloy Cr20Mn15Fe34Co20Ni11 and a TRIP alloy Cr20Mn24Fe30Co20Ni6. After doping 0.5 at.% C, C-TWIP and C-TRIP alloy present a single face-centred cubic phase. Both alloys have achieved simultaneous enhancement of strength and ductility. The yield strength of the C-TWIP alloy increases from 130 ± 4 MPa to 235 ± 5 MPa, and the ultimate tensile strength rises from 402 ± 5 MPa to 646 ± 10 MPa, accompanied by about 40% increase in total elongation. The C-TRIP alloy also shows a simultaneous increase in strength and ductility compared to the C-free TRIP alloy, i.e., the yield strength increases from 165 ± 5 MPa to 220 ± 8 MPa, the ultimate tensile strength rises from 460 ± 5 MPa to 639 ± 8 MPa, and ∼36% of the total elongation. Systematic microstructure investigations were carried out before and after tensile deformation. It was found that C-doping in the C-TWIP alloy retains the TWIP effect while suppressing the dominant TRIP effect to the TWIP effect in the C-TRIP alloy. This work illustrates the role of C in the TWIP and TRIP-assisted HEAs and sheds some light on the design of high-performance alloys.