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      Enhancing radiation tolerance by controlling defect mobility and migration pathways in multicomponent single-phase alloys

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          Abstract

          A grand challenge in material science is to understand the correlation between intrinsic properties and defect dynamics. Radiation tolerant materials are in great demand for safe operation and advancement of nuclear and aerospace systems. Unlike traditional approaches that rely on microstructural and nanoscale features to mitigate radiation damage, this study demonstrates enhancement of radiation tolerance with the suppression of void formation by two orders magnitude at elevated temperatures in equiatomic single-phase concentrated solid solution alloys, and more importantly, reveals its controlling mechanism through a detailed analysis of the depth distribution of defect clusters and an atomistic computer simulation. The enhanced swelling resistance is attributed to the tailored interstitial defect cluster motion in the alloys from a long-range one-dimensional mode to a short-range three-dimensional mode, which leads to enhanced point defect recombination. The results suggest design criteria for next generation radiation tolerant structural alloys.

          Abstract

          Radiation tolerance is a property determined both by materials structure and defect dynamics. Here authors demonstrate enhancement of radiation tolerance at elevated temperatures in equiatomic single-phase concentrated solid solution alloys and propose an underlying mechanism.

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          A fracture-resistant high-entropy alloy for cryogenic applications.

          High-entropy alloys are equiatomic, multi-element systems that can crystallize as a single phase, despite containing multiple elements with different crystal structures. A rationale for this is that the configurational entropy contribution to the total free energy in alloys with five or more major elements may stabilize the solid-solution state relative to multiphase microstructures. We examined a five-element high-entropy alloy, CrMnFeCoNi, which forms a single-phase face-centered cubic solid solution, and found it to have exceptional damage tolerance with tensile strengths above 1 GPa and fracture toughness values exceeding 200 MPa·m(1/2). Furthermore, its mechanical properties actually improve at cryogenic temperatures; we attribute this to a transition from planar-slip dislocation activity at room temperature to deformation by mechanical nanotwinning with decreasing temperature, which results in continuous steady strain hardening. Copyright © 2014, American Association for the Advancement of Science.
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            Metastable high-entropy dual-phase alloys overcome the strength-ductility trade-off.

            Metals have been mankind's most essential materials for thousands of years; however, their use is affected by ecological and economical concerns. Alloys with higher strength and ductility could alleviate some of these concerns by reducing weight and improving energy efficiency. However, most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength-ductility trade-off. Here we present a metastability-engineering strategy in which we design nanostructured, bulk high-entropy alloys with multiple compositionally equivalent high-entropy phases. High-entropy alloys were originally proposed to benefit from phase stabilization through entropy maximization. Yet here, motivated by recent work that relaxes the strict restrictions on high-entropy alloy compositions by demonstrating the weakness of this connection, the concept is overturned. We decrease phase stability to achieve two key benefits: interface hardening due to a dual-phase microstructure (resulting from reduced thermal stability of the high-temperature phase); and transformation-induced hardening (resulting from the reduced mechanical stability of the room-temperature phase). This combines the best of two worlds: extensive hardening due to the decreased phase stability known from advanced steels and massive solid-solution strengthening of high-entropy alloys. In our transformation-induced plasticity-assisted, dual-phase high-entropy alloy (TRIP-DP-HEA), these two contributions lead respectively to enhanced trans-grain and inter-grain slip resistance, and hence, increased strength. Moreover, the increased strain hardening capacity that is enabled by dislocation hardening of the stable phase and transformation-induced hardening of the metastable phase produces increased ductility. This combined increase in strength and ductility distinguishes the TRIP-DP-HEA alloy from other recently developed structural materials. This metastability-engineering strategy should thus usefully guide design in the near-infinite compositional space of high-entropy alloys.
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              Mechanical properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 refractory high entropy alloys

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                Author and article information

                Journal
                Nat Commun
                Nat Commun
                Nature Communications
                Nature Publishing Group
                2041-1723
                15 December 2016
                2016
                : 7
                : 13564
                Affiliations
                [1 ]Department of Nuclear Engineering and Radiological Sciences, University of Michigan , Ann Arbor, Michigan 48109, USA
                [2 ]Materials Science and Technology Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, USA
                [3 ]Department of Materials Science and Engineering, University of Tennessee , Knoxville, Tennessee 37996, USA
                [4 ]Department of Engineering Physics, University of Wisconsin-Madison , Madison, Wisconsin 53706, USA
                [5 ]Department of Materials Science and Engineering, University of Michigan , Ann Arbor, Michigan 48109, USA
                Author notes
                Author information
                http://orcid.org/0000-0001-7697-0466
                http://orcid.org/0000-0003-0283-7990
                http://orcid.org/0000-0002-9017-7365
                Article
                ncomms13564
                10.1038/ncomms13564
                5171798
                27976669
                19fe2204-bdaf-4c68-99b3-ed95489b36be
                Copyright © 2016, The Author(s)

                This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

                History
                : 24 April 2016
                : 13 October 2016
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