TY - JOUR

T1 - Phase Transformation Induced by High Pressure Torsion in the High-Entropy Alloy CrMnFeCoNi

AU - Chulist, Robert

AU - Pukenas, Aurimas

AU - Chekhonin, Paul

AU - Hohenwarter, Anton

AU - Pippan, Reinhard

AU - Schell, Norbert

AU - Skrotzki, Werner

N1 - Publisher Copyright: © 2022 by the authors.

PY - 2022/11/25

Y1 - 2022/11/25

N2 - The forward and reverse phase transformation from face-centered cubic (fcc) to hexagonal close-packed (hcp) in the equiatomic high-entropy alloy (HEA) CrMnFeCoNi has been investigated with diffraction of high-energy synchrotron radiation. The forward transformation has been induced by high pressure torsion at room and liquid nitrogen temperature by applying different hydrostatic pressures and large shear strains. The volume fraction of hcp phase has been determined by Rietveld analysis after pressure release and heating-up to room temperature as a function of hydrostatic pressure. It increases with pressure and decreasing temperature. Depending on temperature, a certain pressure is necessary to induce the phase transformation. In addition, the onset pressure depends on hydrostaticity; it is lowered by shear stresses. The reverse transformation evolves over a long period of time at ambient conditions due to the destabilization of the hcp phase. The effect of the phase transformation on the microstructure and texture development and corresponding microhardness of the HEA at room temperature is demonstrated. The phase transformation leads to an inhomogeneous microstructure, weakening of the shear texture, and a surprising hardness anomaly. Reasons for the hardness anomaly are discussed in detail.

AB - The forward and reverse phase transformation from face-centered cubic (fcc) to hexagonal close-packed (hcp) in the equiatomic high-entropy alloy (HEA) CrMnFeCoNi has been investigated with diffraction of high-energy synchrotron radiation. The forward transformation has been induced by high pressure torsion at room and liquid nitrogen temperature by applying different hydrostatic pressures and large shear strains. The volume fraction of hcp phase has been determined by Rietveld analysis after pressure release and heating-up to room temperature as a function of hydrostatic pressure. It increases with pressure and decreasing temperature. Depending on temperature, a certain pressure is necessary to induce the phase transformation. In addition, the onset pressure depends on hydrostaticity; it is lowered by shear stresses. The reverse transformation evolves over a long period of time at ambient conditions due to the destabilization of the hcp phase. The effect of the phase transformation on the microstructure and texture development and corresponding microhardness of the HEA at room temperature is demonstrated. The phase transformation leads to an inhomogeneous microstructure, weakening of the shear texture, and a surprising hardness anomaly. Reasons for the hardness anomaly are discussed in detail.

KW - high pressure torsion

KW - high-entropy alloy

KW - microstructure

KW - phase transformation

KW - strength

KW - texture

UR - http://www.scopus.com/inward/record.url?scp=85143810866&partnerID=8YFLogxK

U2 - 10.3390/ma15238407

DO - 10.3390/ma15238407

M3 - Article

AN - SCOPUS:85143810866

VL - 2022

JO - Materials

JF - Materials

SN - 1996-1944

IS - 15

M1 - 8407

ER -