Outstanding tensile properties of a precipitation-strengthened FeCoNiCrTi0.2 high-entropy alloy at room and cryogenic temperatures

Superior strength-ductility combination of a Co-rich CoCrNiAlTi high-entropy alloy at room and cryogenic temperatures

“…In addition, TEM observations (figures 6(b) and (c)) on the deformed alloy did not detect nanotwins which coincides with the observations of Yang et al and Tong et al [6,8]. Instead, dense stacking faults were formed during the tension process at 77 K. According to the results of Tong et al [8], the contribution of stacking faults to the strain hardening is weak owing to the space of stacking faults is broad. Hence, the TRIP effect provides an additional strengthening mechanism contributing to the pronounced strain hardening rate.…”

“…Thus, the alloy sustains relatively steady strain hardening behaviour with a high hardening rate (over 3000 MPa) during the entire plastic straining stage. Recently, Yang et al and Tong et al reported that nano-precipitated HEAs exhibited abnormal increases of strain-hardening rate during the plastic straining process both at 293 K and 77 K [6,8]. It is clearly that our alloy displays a different plastic deformation behaviour compared to the research of Yang et al suggesting different underlying mechanisms operative in the two alloys.…”

“…However, the coarse-grained high-entropy alloys (HEAs) with a face-centered cubic (FCC)-structured single phase usually display good ductility but relative low yield strength at ambient temperatures [2]. Refining the grains to ultrafine scale (UFG) as well as the introduction of high-density nano-precipitates (such as coherent γ′ phase with L1 2 structure) in the FCC-structured matrix phase have proved to be effective methods in enhancing yield strength to a gigapascal level [3][4][5][6][7][8]. However, in such cases, the ductility (UE) is generally scarified severely because phase transformation (transformation-induced plasticity (TRIP)) and twinning (twinning-induced plasticity (TWIP)) all lose their potent in these ultra-fine-grained as well as high-density nano-particles strengthened alloys [3][4][5][6][7][8].…”

Constitutive modelling of hot deformation behaviour of a CoCrFeMnNi high-entropy alloy

“…According to the Equations (15)(16)(17)(18), the material constants α, n, Q and A can be calculated under different strains, and thus the same values are substituted in Equation 5to obtain the constitutive equations at different strain rates. The corresponding stress values can be evaluated from Equation (11).…”

“…The number of HEA compositions under investigation is increasing steadily due to the evergrowing interest and research efforts in this field, particularly driven by their superb properties [12]. Notable among the exceptional mechanical properties are high strength at elevated temperatures, excellent cryogenic toughness [13][14][15][16], high wear resistance [17][18][19], good thermal stability [20][21][22], excellent fracture toughness [14,23,24] and superior corrosion resistance [25]. Thus far, CoCrFeMnNi is the most studied HEA [26][27][28][29][30] and is also called as 'Cantor alloy' named after Cantor et al [2] for their first studies of the alloy.…”