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Heczel, Anita,Kawasaki, Megumi,Lá,bá,r, Já,nos L.,Jang, Jae-il,Langdon, Terence G.,Gubicza, Jenő Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.711 No.-
<P><B>Abstract</B></P> <P>An equiatomic CoCrFeMnNi High-Entropy Alloy (HEA) produced by arc melting was processed by High-Pressure Torsion (HPT). The evolution of the microstructure during HPT was investigated after ¼, ½, 1 and 2 turns using electron backscatter diffraction and transmission electron microscopy. The spatial distribution of constituents was studied by energy-dispersive X-ray spectroscopy. The dislocation density and the twin-fault probability in the HPT-processed samples were determined by X-ray line profiles analysis. It was found that the grain size was gradually refined from ∼60 μm to ∼30 nm while the dislocation density and the twin-fault probability increased to very high values of about 194 × 10<SUP>14</SUP> m<SUP>−2</SUP> and 2.7%, respectively, at the periphery of the disk processed for 2 turns. The hardness evolution was measured as a function of the distance from the center of the HPT-processed disks. After 2 turns of HPT, the microhardness increased from ∼1440 MPa to ∼5380 MPa at the disk periphery where the highest straining is achieved. The yield strength was estimated as one-third of the hardness and correlated to the microstructure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The microstructure and the hardness in HPT processed CoCrFeMnNi HEA were studied. </LI> <LI> The dislocation density increased up to 194 × 10<SUP>14</SUP> m<SUP>−2</SUP> after 2 turns of HPT. </LI> <LI> The grain size decreased to 27 nm at the periphery of the disk processed by 2 turns. </LI> <LI> After 2 turns the twin fault probability increased to 2.7% at the disk periphery. </LI> <LI> The hardness increased from 1440 MPa to 5380 MPa due to 2 turns of HPT. </LI> </UL> </P>