Peculiarities of deformation of CoCrFeMnNi at cryogenic temperatures
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ARTICLE Peculiarities of deformation of CoCrFeMnNi at cryogenic temperatures Aditya Srinivasan Tirunilai Institute for Applied Materials (IAM-WK), Karlsruhe Institute of Technology (KIT), Karlsruhe D-76131, Germany
Jan Sas and Klaus-Peter Weiss Institute for Technical Physics (ITEP), Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen D-76344, Germany
Hans Chen Institute for Applied Materials (IAM-WK), Karlsruhe Institute of Technology (KIT), Karlsruhe D-76131, Germany
Dorothée Vinga Szabó and Sabine Schlabach Institute for Applied Materials (IAM-WK), Karlsruhe Institute of Technology (KIT), Karlsruhe D-76131, Germany; and Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen D-76344, Germany
Sebastian Haas Metals and Alloys, University Bayreuth, Bayreuth D-95447, Germany
David Geissler Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden), Institute for Complex Materials, Dresden D-01069, Germany
Jens Freudenberger Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden), Institute for Metallic Materials, Dresden D-01069, Germany; and Institute of Materials Science, Technische Universität Bergakademie Freiberg, Freiberg 09599, Germany
Martin Heilmaier and Alexander Kauffmanna) Institute for Applied Materials (IAM-WK), Karlsruhe Institute of Technology (KIT), Karlsruhe D-76131, Germany (Received 13 April 2018; accepted 3 July 2018)
This contribution presents a comprehensive analysis of the low temperature deformation behavior of CoCrFeMnNi on the basis of quasistatic tensile tests at temperatures ranging from room temperature down to 4.2 K. Different deformation phenomena occur in the high-entropy alloy in this temperature range. These include (i) serrated plastic flow at certain cryogenic temperatures (4.2 K/8 K), (ii) deformation twinning (4.2 K/8 and 77 K), and (iii) dislocation slip (active from 4.2 K up to room temperature). The importance of deformation twinning for a stable work-hardening rate over an extended stress range as well as strain range has been addressed through the use of comprehensive orientation imaging microscopy studies. The proposed appearance of e-martensite as well as a previously uninvestigated route of analysis, essentially a quantitative time-dependent, strain-dependent, and stress-dependent evaluation of the serrated plastic flow in CoCrFeMnNi is provided.
I. INTRODUCTION
High-entropy alloys (HEAs) are a class of metallic alloys that have recently gained intense interest, especially over the course of the last decade.1–8 Research in HEAs is considered to be a field that allows for the evaluation of prevalent theories under new, previously unexamined conditions. Among HEAs, no alloy has been subject to more research than the face-centered cubic (fcc), equiatomic CoCrFeMnNi
a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.252 J. Mater. Res., 2018
alloy, which was first synthesized by Cantor et al.9 This alloy exhibi
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