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-centered cubic (fcc) 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.m1/2; 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.m1/2. 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.
@article{arxiv.1602.01155,
title = {Exceptional damage-tolerance of a medium-entropy alloy CrCoNi at cryogenic temperatures},
author = {Bernd Gludovatz and Anton Hohenwarter and Keli V. S. Thurston and Hongbin Bei and Zhenggang Wu and Easo P. George and Robert O. Ritchie},
journal= {arXiv preprint arXiv:1602.01155},
year = {2016}
}