Hyeonseok Kwon , Jae Heung Lee , Alireza Zargaran , Stefanus Harjo , Wu Gong , Jaemin Wang , Gang Hee Gu , Byeong-Joo Lee , Jae Wung Bae , Hyoung Seop Kim
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引用次数: 0
Abstract
In this work, we harness a hierarchical microstructure to tailor both the strengthening and deformation mechanisms of Co21Cr12.5Fe55Ni4Mo7.5 (at %) ferrous medium-entropy alloy (MEA) simultaneously. A simple thermomechanical processing (cold rolling and 90 s of annealing) creates a hierarchical microstructure composed of ultrafine recrystallized grains, non-recrystallized grains with rolling-driven substructures, and intragranular nanoprecipitates. The hierarchical microstructure with the high density of dislocations and ultrafine recrystallized grains leads to a high yield strength of ∼1.60 GPa, but it is well-known that the same features can make materials vulnerable to premature fracture. To solve this issue, Lüders deformation, which was induced by the ultrafine grain boundaries and stress-induced martensitic transformation facilitated by pre-existing martensite nucleation sites, was harnessed: stable propagation of the Lüders band delays massive strain hardening by regulating strain-induced martensitic deformation that ensues and enables a large uniform ductility. Resultantly, tensile strength of ∼1.84 GPa and uniform elongation of ∼20 % are achieved, on par with the finest tensile properties among multi-principal element alloys ever reported. Our results point to a paradigm to achieve a large uniform ductility via harnessing the Lüders deformation without compromising strength, based on the hierarchical microstructure.
期刊介绍:
International Journal of Plasticity aims to present original research encompassing all facets of plastic deformation, damage, and fracture behavior in both isotropic and anisotropic solids. This includes exploring the thermodynamics of plasticity and fracture, continuum theory, and macroscopic as well as microscopic phenomena.
Topics of interest span the plastic behavior of single crystals and polycrystalline metals, ceramics, rocks, soils, composites, nanocrystalline and microelectronics materials, shape memory alloys, ferroelectric ceramics, thin films, and polymers. Additionally, the journal covers plasticity aspects of failure and fracture mechanics. Contributions involving significant experimental, numerical, or theoretical advancements that enhance the understanding of the plastic behavior of solids are particularly valued. Papers addressing the modeling of finite nonlinear elastic deformation, bearing similarities to the modeling of plastic deformation, are also welcomed.