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Exceptional damage-tolerance of a medium-entropy alloy CrCoNi at cryogenic temperatures

Bernd GludovatzMaterials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USAAnton HohenwarterDepartment of Materials Physics, Montanuniversität Leoben and Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben 8700, AustriaKeli V.S. ThurstonDepartment of Materials Science and Engineering, University of California, Berkeley, California 94720, USAHongbin BeiMaterials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USAZhenggang WuDepartment of Materials Sciences and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USAE.P. GeorgeDepartment of Materials Sciences and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USARobert O. RitchieDepartment of Materials Science and Engineering, University of California, Berkeley, California 94720, USA

2016en

ABI

Annotatsiya

High-entropy alloys are an intriguing new class of metallic materials that derive their properties from being multi-element systems that can crystallize as a single phase, despite containing high concentrations of five or more elements with different crystal structures. Here we examine an equiatomic medium-entropy alloy containing only three elements, CrCoNi, as a single-phase face-centred cubic solid solution, which displays strength-toughness properties that exceed those of all high-entropy alloys and most multi-phase alloys. At room temperature, the alloy shows tensile strengths of almost 1 GPa, failure strains of ∼70% and KJIc fracture-toughness values above 200 MPa m(1/2); at cryogenic temperatures strength, ductility and toughness of the CrCoNi alloy improve to strength levels above 1.3 GPa, failure strains up to 90% and KJIc values of 275 MPa m(1/2). Such properties appear to result from continuous steady strain hardening, which acts to suppress plastic instability, resulting from pronounced dislocation activity and deformation-induced nano-twinning.

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DOI: 10.1038/ncomms10602

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