Cryogenic-temperature fracture toughness analysis of non-equi-atomic V10Cr10Fe45Co20Ni15 high-entropy alloy

• Published in: Journal of alloys and compounds Vol. 809; p. 151864
• Main Authors: Jo, Yong Hee, Doh, Kyung-Yeon, Kim, Dong Geun, Lee, Kwanho, Kim, Dae Woong, Sung, Hyokyung, Sohn, Seok Su, Lee, Donghwa, Kim, Hyoung Seop, Lee, Byeong-Joo, Lee, Sunghak
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.11.2019; Elsevier BV
• Subjects: Ab-initio calculation; Alloys; Cryogenic properties; Cryogenic temperature; Damage tolerance; Elongation; Entropy; Face centered cubic lattice; Fracture toughness; High entropy alloys; High-entropy alloy (HEA); Mathematical analysis; Mechanical properties; Medium entropy alloys; Stacking fault energy (SFE); Stacking faults; Superalloys; High-entropy alloy (HEA); Stacking fault energy (SFE); Cryogenic temperature; Ab-initio calculation; Fracture toughness
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2019.151864

Representative face-centered-cubic (FCC) high-entropy alloys (HEAs) or medium-entropy alloys (MEAs), e.g., equi-atomic CoCrFeMnNi or CrCoNi alloys, have drawn many attentions due to the excellent damage-tolerance at cryogenic temperature. The investigation of fracture toughness at 77 K is basically required for the reliable evaluation of high-performance alloys used for cryogenic applications; however, it has been rarely carried out for the non-equi-atomic FCC HEAs yet. In this study, tensile and fracture toughness tests were conducted on the non-equi-atomic V10Cr10Fe45Co20Ni15 alloy, and the results were compared with those of the equi-atomic CoCrFeMnNi and CrCoNi alloys. The present alloy shows a good damage tolerance at cryogenic temperature with tensile strength of 1 GPa and elongation of ∼60%. The KJIc fracture toughness values are 219 and 232 MPa m1/2 at 298 and 77 K, respectively, showing the increase in toughness with decreasing temperature. This increase results from the absence of twins at 298 K and the increased propensity to twin formation at 77 K, which is well confirmed by the variation of stacking fault energies (SFEs) by using Ab-initio calculations. The mechanical properties of the present alloy are actually similar or slightly lower than those of the other CoNiCr or FeMnCoNiCr alloy; instead, this study provides that neither composition nor certain elements are the most important factors dictating damage-tolerance of HEAs or MEAs. [Display omitted] •The increase in fracture toughness with decreasing temperature for the non-equi-atomic HEA is achieved for the first time.•The SFE decreases in the order of the V10Cr10Fe45Co20Ni15, CrMnFeCoNi, and CrCoNi alloys.•Increase in twins acts as a key parameter contributing to the relief of detrimental cryogenic-temperature effects.•Neither composition nor certain elements are the most important factors dictating damage-tolerance of HEAs or MEAs.