Microstructure and Mechanical Properties of High-Entropy Alloy Co(20)Cr(26)Fe(20)Mn(20)Ni(14) Processed by High-Pressure Torsion at 77 K and 300 K

In this work, the mechanical characteristics of high-entropy alloy Co(20)Cr(26)Fe(20)Mn(20)Ni(14) with low-stacking fault energy processed by cryogenic and room temperature high-pressure torsion (HPT) were studied. X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses were performed to identify the phase and microstructure variation and the mechanical properties characterized by Vickers hardness measurements and tensile testing. Cryogenic HPT was found to result in a lower mechanical strength of alloy Co(20)Cr(26)Fe(20)Mn(20)Ni(14) than room temperature HPT. Microstructure analysis by SEM and TEM was conducted to shed light on the microstructural changes in the alloy Co(20)Cr(26)Fe(20)Mn(20)Ni(14) caused by HPT processing. Electron microscopy data provided evidence of a deformation-induced phase transformation in the alloy processed by cryogenic HPT. Unusual softening phenomena induced by cryogenic HPT were characterized by analyzing the dislocation density as determined from X-Ray diffraction peak broadening.