Cryogenic strength improvement by utilizing room-temperature deformation twinning in a partially recrystallized VCrMnFeCoNi high-entropy alloy

Abstract

The excellent cryogenic tensile properties of the CrMnFeCoNi alloy are generally caused by deformation twinning, which is difficult to achieve at room temperature because of insufficient stress for twinning. Here, we induced twinning at room temperature to improve the cryogenic tensile properties of the CrMnFeCoNi alloy. Considering grain size effects on the critical stress for twinning, twins were readily formed in the coarse microstructure by cold rolling without grain refinement by hot rolling. These twins were retained by partial recrystallization and played an important role in improving strength, allowing yield strengths approaching 1 GPa. The persistent elongation up to 46% as well as the tensile strength of 1.3 GPa are attributed to additional twinning in both recrystallized and non-recrystallization regions. Our results demonstrate that non-recrystallized grains, which are generally avoided in conventional alloys because of their deleterious effect on ductility, can be useful in achieving high-strength high-entropy alloys.

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

“…Micro-twining mechanism at cryogenic temperatures Micro-twins have been experimentally observed in most HEAs during deformation, [2][3][4]8,15 particularly at 77 K, and are regarded as a probable reason for excellent tensile properties at 77 K. Previous studies claimed that the low stacking fault energy (SFE) of HEAs is one of the probable reasons for the micro-twinning. 27,28 However, it is not fully understood why HEAs have a low SFE.…”

“…4 Even though most HEAs have equiatomic or near equiatomic compositions, it is believed that the equiatomic composition would not be the optimum composition for a wide range of material properties. [5][6][7][8][9][10] To improve a specific material property, one may have to change the alloy composition from the equiatomic composition. Indeed, there have been many efforts to improve the facecentered cubic (fcc) single-phase stability or mechanical properties of the CoCrFeMnNi HEAs by adjusting the composition.…”

“…Indeed, there have been many efforts to improve the facecentered cubic (fcc) single-phase stability or mechanical properties of the CoCrFeMnNi HEAs by adjusting the composition. [5][6][7][8][9] However, for an efficient alloy design, one would need to understand the reason for the typical HEA properties and the effect of individual elements on them.…”

“…Sluggish diffusion, [11][12][13] severe lattice distortion 14 and microtwinning [2][3][4]8,15 have been mentioned as probable reasons for the typical HEA properties. However, exact mechanisms for such structural reasons are not clearly known yet.…”

High‐Entropy Alloys: Potential Candidates for High‐Temperature Applications – An Overview

“…The VCrMnFeCoNi HEA exhibits excellent cryogenic mechanical properties with a yield strength of %1 GPa and elongation up to 46%. [59] The HE nitride film of SiTiVAlCrNb shows remarkable thermal stability by retaining its nanostructure even after annealing at 1000 C for 5 h. [75] The [76] In addition, a wide range of multicomponent amorphous alloys based on equiatomic substitution has been investigated. [77][78][79][80][81][82] In one of the study, the addition of Nb is reported to increase the thermal stability of amorphous phase.…”