Activation energy for plastic flow in nanocrystalline CoCrFeMnNi high-entropy alloy: A high temperature nanoindentation study

Nanoindentation experiments in the temperature (7) range of 298 and 573 K were performed to determine the activation energy (Q) for the plastic flow in a nanocrystalline CoCrFeMnNi high-entropy alloy, which was synthesized using high-pressure torsion. A marked increase in Q from similar to 0.5 to similar to 1.8 eV was observed when T is increased from 473 to 523 K, which correspond to similar to 0.3 and similar to 0.34 T-m (T-m: melting temperature), respectively. Detailed analysis reveals that this transition is associated with the additional activation of the grain boundary diffusion mechanism in enhancing plasticity. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.The work at Hanyang University was supported by the National Research Foundation of Korea (NRF) grants funded by the Ministry of Science and ICT (No. 2015R1A5A1037627 and No. 2017R1A2B4012255). The work at Karlsruhe Institute of Technology was supported by the Deutsche Forschungsgemeinschaft DFG (German Research Foundation) under grant number SCHW 855/6-1 within the priority program SPP 2006 "Compositionally Complex Alloys - High Entropy Alloys (CCA-HEA)"