title: Dislocation mechanisms and 3D twin architectures generate exceptional strength-ductility-toughness combination in CrCoNi medium-entropy alloy.
abstract: Combinations of high strength and ductility are hard to attain in metals. Exceptions include materials exhibiting twinning-induced plasticity. To understand how the strength-ductility trade-off can be defeated, we apply in situ, and aberration-corrected scanning, transmission electron microscopy to examine deformation mechanisms in the medium-entropy alloy CrCoNi that exhibits one of the highest combinations of strength, ductility and toughness on record. Ab initio modelling suggests that it has negative stacking-fault energy at 0K and high propensity for twinning. With deformation we find that a three-dimensional (3D) hierarchical twin network forms from the activation of three twinning systems. This serves a dual function: conventional twin-boundary (TB) strengthening from blockage of dislocations impinging on TBs, coupled with the 3D twin network which offers pathways for dislocation glide along, and cross-slip between, intersecting TB-matrix interfaces. The stable twin architecture is not disrupted by interfacial dislocation glide, serving as a continuous source of strength, ductility and toughness.
authors.affiliation: Center of Electron Microscopy &State Key Laboratory of Silicon Materials, Department of Materials Science &Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Zijiao
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Physics and Astronomy, George Mason University, Fairfax, Virginia 22030, USA.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Sheng
authors.affiliation: Department of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Zhangjie
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Bernd
authors.identifier: 0000-0002-2420-3879
authors.initials: B
authors.lastname: Gludovatz
authors.affiliation: Center of Electron Microscopy &State Key Laboratory of Silicon Materials, Department of Materials Science &Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Ze
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Materials Sciences &Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Easo P
authors.initials: EP
authors.lastname: George
authors.affiliation: Center of Electron Microscopy &State Key Laboratory of Silicon Materials, Department of Materials Science &Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Yu
authors.affiliation: Center of Electron Microscopy &State Key Laboratory of Silicon Materials, Department of Materials Science &Engineering, Zhejiang University, Hangzhou 310027, China.|Department of Mechanical Engineering &Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Scott X
authors.initials: SX
authors.lastname: Mao
authors.affiliation: Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.|Department of Materials Science &Engineering, University of California, Berkeley, California 94720, USA.
authors.forename: Robert O
authors.identifier: 0000-0002-0501-6998
authors.initials: RO
authors.lastname: Ritchie