Journal
ACTA MATERIALIA
Volume 140, Issue -, Pages 443-451Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2017.08.057
Keywords
High-entropy alloy; Nanocrystalline metal; Annealing effect; Constitutive behavior
Funding
- Convergence Agenda Program (CAP) of the Korea Research Council of Fundamental Science and Technology [CAP-11-05-KRISS]
- National Research Foundation of Korea (NRF) - Ministry of Science and ICT [2015R1A5A1037627, 2017R1A2B4012255]
- National Research Council of Science & Technology (NST), Republic of Korea [CAP-11-05-KRISS] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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The influence of annealing on the constitutive stress-strain response of nanocrystalline (nc) CoCrFeMnNi high-entropy alloy (HEA) was investigated through a series of nanoindentation experiments using five different three-sided pyramidal indenters. The nc HEA, produced by high-pressure torsion (HPT), was subjected to annealing at 450 degrees C for 1 and 10 h. Microstructural analysis using transmission electron microscopy (TEM) showed that three different nano-scale precipitates (NiMn-, FeCo-, and Co-rich phases) form in the primary single-phase matrix of nc HEA after annealing. The strain-dependent plastic flow response of nc HEA pre- and post-annealing was estimated using the indentation strain and constraint factor, revealing a significant strain softening in nc HEA, which becomes pronounced after annealing. TEM analysis of the deformed material underneath the indenter suggests that the plastic deformation aids in the dissolution of the annealing-induced intermetallic precipitates, which could be the mechanism for the pronounced softening. The dissolution mechanism was rationalized by the destabilization of precipitates during plastic deformation due to the increase in interface energy. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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