Dynamic shear deformation of a CrCoNi medium-entropy alloy with heterogeneous grain structures. (15th April 2018)

• Record Type: Journal Article
• Authors: Ma, Yan; Yuan, Fuping; Yang, Muxin; Jiang, Ping; Ma, Evan; Wu, Xiaolei
• Is Part Of: Acta materialia. Volume 148(2018)
• Page Start: 407
• Page End: 418
• Publication Date: 2018-04-15
• Subjects: Medium-entropy alloys -- Dynamic shear properties -- Grain refinement -- Lomer-Cottrell locks -- Phase transformation; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2018.02.016
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Single-phase CrCoNi medium-entropy alloys (MEA) are emerging recently as an interesting class of metallic materials, but the dynamic response of this MEA at high strain rates remains unknown. Here we have produced this MEA with various heterogeneous microstructures, using cold rolling followed by annealing at various temperatures. The high-strain-rate response of the MEAs was characterized using hat-shaped specimens in Hopkinson-bar experiments. A combination of high dynamic shear yield strength and large uniform dynamic shear strain was observed, exceeding all other metals and alloys reported so far. Even better dynamic shear properties was revealed when the experiments were conducted at cryogenic temperature. The strong strain hardening under dynamic shear loading can be attributed to the dynamic grain refinement and deformation twinning that accompany the homogeneous shear deformation. When compared to room temperature, the efficiency of grain refinement was found to be enhanced at cryogenic temperature, with a higher density of multiple twins, stacking faults, Lomer-Cottrell locks, and hcp phase via phase transformation inside the grains, which could be responsible for the better dynamic shear properties under cryogenic environment. Graphical abstract: Image 1