Gradient cell–structured high-entropy alloy with exceptional strength and ductility

Pan, Qingsong; Zhang, Liangxue; Feng, Rui; Lu, Qian; An, Ke; Chuang, Andrew Chihpin; Poplawsky, Jonathan D.; Liaw, Peter K.; Lü, Lei

doi:10.1126/science.abj8114

Cited by 446 publications

(86 citation statements)

References 79 publications

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“…Based on the Taylor hardening model, 38 the hardness can be increased by the presence of a higher density of dislocations. Meanwhile, the native dislocations, especially dislocation networks, could prevent slide and growth of dislocations under the applied stress, leading to increase of strength 11 . Similarly, the lattice stress can also improve strength via restraining slide of dislocations 39 .…”

Section: Resultsmentioning

confidence: 99%

High hardness (TiZr)C ceramic with dislocation networks

et al. 2022

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Raising the configurational entropy in a solid solution ceramic is regarded as a promising strategy to improve the mechanical properties of ceramics, especially when five or more elements are mixed to form so-called high-entropy ceramics. However, in this study, we report that the binary (TiZr)C solid solution ceramics can demonstrate high hardness comparable or even superior to high-entropy ceramics. Followed by a carbothermal reduction synthesis of carbide powders, the bulk ceramics were synthesized by hot pressing. Via increasing the hot pressing temperature to 2200 • C, a full solid solution of equimolar (TiZr)C was obtained in contrast to phase separation at lower sintering temperatures, for example, 2000 and 2100 • C. The dislocation networks are observed in the single-phase (TiZr)C ceramic and should be the product of competition between enthalpy and entropy in a binary full solid solution. These defects finally contribute to the high nano-hardness of 41.9 ± 1.4 GPa (H) and the Vickers hardness of 22.0 ± 0.6 GPa (H V at 49 N).

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Section: Resultsmentioning

confidence: 99%

High hardness (TiZr)C ceramic with dislocation networks

et al. 2022

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“…Besides, no visible deformation twins and martensitic phase are observed in the GDS sample. Such gradient dislocation structure in the austenitic GDS 304 SS sample is primarily a result of the imposed gradient plastic strain from the topmost surface to the core under a gradient stress/strain state with a large accumulative strain [3,18]. The above microstructural observations indicate that a distinctive hierarchical dislocation structure, i.e., gradiently distributed dislocation patterns and size, is developed in the micron-sized grains of austenitic 304 SS after CT treatment.…”

Section: Resultsmentioning

confidence: 99%

“…Dog-bone-shaped bar CG 304 SS specimens with a gauge diameter of 6 mm and a gauge length of 12 mm were processed by means of a novel cyclic-torsion (CT) treatment on an Instron (Boston, MA, USA) 8874 testing machine at ambient temperature. The CT treatment is referred to as a repeatedly imposed gradient plastic deformation process when one end of the bar sample is torqued under a specific torsion angle amplitude with a number of cycles while the other end is kept fixed [18,19]. The CT processing parameters are described as follows: the torsion angle amplitude of 16 • was used at a torsion rate of 144 • s −1 .…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, they are good candidates for this type of research. In this study, by using the cyclic-torsion treatment [17,18], we produce a distinctive gradient nano-scaled low-angle dislocation structure (GDS) without changing initial grain size in one most widespread used 304 stainless steel (304 SS). A remarkably improved yield strength with continuous strain-hardening and high ductility combination is achieved in the GDS 304 SS, owing to the suppressed strain localization and resultant hardening in GDS associated with extensive dislocation storage and deformation twinning.…”

Section: Introductionmentioning

confidence: 99%

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Superior Strength and Ductility of 304 Austenitic Stainless Steel with Gradient Dislocations

et al. 2021

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Materials with designed gradient nanograins exhibit unprecedented mechanical properties, such as superior strength and ductility. In this study, a heterostructured 304 stainless steel with solely gradient dislocation structure (GDS) in micron-sized grains produced by cyclic-torsion processing was demonstrated to exhibit a substantially improved yield strength with slightly reduced uniform elongation, compared with its coarse grained counterparts. Microstructural observations reveal that multiple deformation mechanisms, associated with the formation of dense dislocation patterns, deformation twins and martensitic phase, are activated upon straining and contribute to the delocalized plastic deformation and the superior mechanical performance of the GDS 304 stainless steel.

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“…During the tensile deformation process, there is a significant strain gradient from the surface to the core, which transforms the uniaxial stress state into a multiaxial stress state, promoting the continuous accumulation and delivery of dislocations, which in turn produces additional work hardening capacity. Recently, Pan et al [19] introduced a gradient dislocation cell structure into Al 0.1 CoCrFeNi high entropy alloy using a small-angle reciprocal torsional gradient plastic deformation technique, while keeping the morphology, size and orientation of the original grain unchanged. The strength of graded dislocation cell alloys is 2-3 times that of coarse-grained and fine-grained materials while maintaining good plasticity and stable work hardening.…”

Section: Introductionmentioning

confidence: 99%

Quasi-Static, Dynamic Compressive Properties and Deformation Mechanisms of Ti-6Al-4V Alloy with Gradient Structure

Lei

Zhang

Zhao

et al. 2021

Metals

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Gradient structure metals have good comprehensive properties of strength and toughness and are expected to improve the dynamic mechanical properties of materials. However, there are few studies on the dynamic mechanical properties of gradient structured materials, especially titanium alloys. Therefore, in this study, ultrasonic surface rolling is used to prepare a gradient structure layer on the surface of Ti-6Al-4V, and the quasi-static and dynamic compressive properties of coarse-grained Ti-6Al-4V (CG Ti64) and gradient-structured Ti-6Al-4V (GS Ti64) are investigated. The results show that a GS with a thickness of 293 µm is formed. The quasi-static compressive strength of GS Ti64 is higher than that of CG Ti64. Both CG Ti64 and GS Ti64 exhibit weak strain hardening effects and strain rate insensitivity during dynamic compression, and the compressive strength is not significantly improved. The lateral expansion of CG Ti64 is more obvious, while the lateral side of GS Ti64 is relatively straight, indicating that uniform deformation occurs in GS Ti64. The α phase in the GS produces dislocation cells and local deformation bands, and the lamellar structure is transformed into ultrafine crystals after dynamic compression. Both of them produce an adiabatic shear band under 2700 s−1, a large crack forms in CG Ti64, while GS Ti64 forms a small crack, indicating that GS Ti64 has better resistance to damage. The synergistic deformation of GS and CG promotes Ti-6Al-4V to obtain good dynamic mechanical properties.

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Gradient cell–structured high-entropy alloy with exceptional strength and ductility

Cited by 446 publications

References 79 publications

High hardness (TiZr)C ceramic with dislocation networks

High hardness (TiZr)C ceramic with dislocation networks

Superior Strength and Ductility of 304 Austenitic Stainless Steel with Gradient Dislocations

Quasi-Static, Dynamic Compressive Properties and Deformation Mechanisms of Ti-6Al-4V Alloy with Gradient Structure

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