Insights into the deformation behavior of the CrMnFeCoNi high-entropy alloy revealed by elevated temperature nanoindenta
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Benjamin Schuh Department Materials Physics, Montanuniversität Leoben & Erich-Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben A-8700, Austria
Easo P. George Oak Ridge National Laboratory, Materials Science and Technology Division, Oak Ridge, Tennessee 37831-6115, USA; and Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996-2100, USA
Helmut Clemens Department Physical Metallurgy & Materials Testing, Montanuniversität Leoben, Leoben A-8700, Austria
Anton Hohenwarter Department Materials Physics, Montanuniversität Leoben & Erich-Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben A-8700, Austria (Received 24 February 2017; accepted 13 June 2017)
A CrMnFeCoNi high-entropy alloy was investigated by nanoindentation from room temperature to 400 °C in the nanocrystalline state and cast plus homogenized coarse-grained state. In the latter case a h100i-orientated grain was selected by electron back scatter diffraction for nanoindentation. It was found that hardness decreases more strongly with increasing temperature than Young’s modulus, especially for the coarse-grained state. The modulus of the nanocrystalline state was slightly higher than that of the coarse-grained one. For the coarse-grained sample a strong thermally activated deformation behavior was found up to 100–150 °C, followed by a diminishing thermally activated contribution at higher testing temperatures. For the nanocrystalline state, different temperature dependent deformation mechanisms are proposed. At low temperatures, the governing processes appear to be similar to those in the coarse-grained sample, but with increasing temperature, dislocation-grain boundary interactions likely become more dominant. Finally, at 400 °C, decomposition of the nanocrystalline alloy causes a further reduction in thermal activation. This is rationalized by a reduction of the deformation controlling internal length scale by precipitate formation in conjunction with a diffusional contribution.
I. INTRODUCTION
During the last few years, multicomponent alloys with at least 5 major alloying elements and individual concentrations ranging between 5 and 35 at.%, generally termed as high-entropy alloys (HEAs) or compositionally complex alloys, have attracted considerable attention.1–7 The extraordinarily large number of alloys conceivable in this multicomponent space, together with promising mechanical properties (in some cases), has opened a fascinating new field in metallurgy and materials science. This novel alloying concept can benefit from new combinatorial approaches7,8 and high-throughput characterization techniques, especially if small sample
Contributing Editor: Mathias Göken a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.260
volumes can be characterized in terms of their mechanical properties and phase stability.7,9 Pioneering studies on the face-centered cubic (fcc) alloy, CrMnFeCoNi, showed that it has ext
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