Cryogenic tensile behavior of carbon-doped CoCrFeMnNi high-entropy alloys additively manufactured by laser powder bed fusion

Cryogenic tensile behaviors of carbon-doped CoCrFeMnNi high-entropy alloy (C-HEA) printed by laser powder bed fusion (LPBF) were systematically explored. The LPBFed C-HEA exhibits excellent cryogenic tensile properties with not only high yield strength but also largely extended elongation as compared to those under room temperature deformation. In particular, the elongation of the C-HEA is twice as high at 77 K compared to 298 K. The strain hardening rate of LPBFed C-HEA under cryogenic deformation is much higher than that under plastic deformation at the room temperature, which contributes to the dramatic enhancement of uniform elongation by delaying plastic instability. Because the flow stress of C-HEA is significantly increased by temperature decrease, it can exceed the critical twinning stress at the early-stage deformation at 77 K. Deformation twins and nano-carbides synergistically contribute to the high back stress evolution of the C-HEA under cryogenic tensile deformation. This study can provide a new perspective on developing high-performance alloys for use in additive manufacturing in cryogenic applications.