Ultra-strong and strain-hardenable ultrafine-grained medium-entropy alloy via enhanced grain-boundary strengthening

Park, Jeong Min; Yang, Dae Cheol; Kim, Han Jin; Kim, Dong Geun; Lee, Sunghak; Kim, Hyoung Seop; Sohn, Seok Su

doi:10.1080/21663831.2021.1913768

Cited by 50 publications

(2 citation statements)

References 32 publications

(71 reference statements)

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“…Here we present a unique way of work hardening that harnesses premature necking during Lüders banding to induce the rapid multiplication of dislocations. The VCoNi MPEA is selected as the prototype [14][15][16] , having the local-chemical-order (LCO) regions as built-in heterogeneities [17][18][19][20][21][22] . We show that in addition to forest dislocation work hardening, the dislocations further interact with the LCO regions, promoting dislocation accumulation in ultrafine grains (UFGs) and consequently contributing to additional work hardening.…”

Section: Premature Necking and Plastic Responsesmentioning

confidence: 99%

Harnessing instability for work hardening in multi-principal element alloys

Xu,

Duan,

Chen

et al. 2024

Nat. Mater.

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The strength–ductility trade-off has long been a Gordian knot in conventional metallic structural materials and it is no exception in multi-principal element alloys. In particular, at ultrahigh yield strengths, plastic instability, that is, necking, happens prematurely, because of which ductility almost entirely disappears. This is due to the growing difficulty in the production and accumulation of dislocations from the very beginning of tensile deformation that renders the conventional dislocation hardening insufficient. Here we propose that premature necking can be harnessed for work hardening in a VCoNi multi-principal element alloy. Lüders banding as an initial tensile response induces the ongoing localized necking at the band front to produce both triaxial stress and strain gradient, which enables the rapid multiplication of dislocations. This leads to forest dislocation hardening, plus extra work hardening due to the interaction of dislocations with the local-chemical-order regions. The dual work hardening combines to restrain and stabilize the premature necking in reverse as well as to facilitate uniform deformation. Consequently, a superior strength-and-ductility synergy is achieved with a ductility of ~20% and yield strength of 2 GPa during room-temperature and cryogenic deformation. These findings offer an instability-control paradigm for synergistic work hardening to conquer the strength–ductility paradox at ultrahigh yield strengths.

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Section: Premature Necking and Plastic Responsesmentioning

confidence: 99%

Harnessing instability for work hardening in multi-principal element alloys

Xu,

Duan,

Chen

et al. 2024

Nat. Mater.

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“…However, developing high strength and ductility of metallic material simultaneously has been the great challenge for materials scientists [ 1 , 2 ]. Ultrafine-grained (UFG) metallic materials, which have extremely high strength compared with their coarse-grained (CG) counterparts, have generated considerable attention [ 1 , 3 ]. However, the limitation of UFG materials is their poor ductility, something which is the main barrier for widely used commercial applications [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Copper of Harmonic Structure: Mechanical Property-Based Optimization of the Milling Parameters and Fracture Mechanism

et al. 2022

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A severe plastic deformation process for the achievement of favorable mechanical properties for metallic powder is mechanical milling. However, to obtain the highest productivity while maintaining reasonable manufacturing costs, the process parameters must be optimized to achieve the best mechanical properties. This study involved the use of response surface methodology to optimize the mechanical milling process parameters of harmonic-structure pure Cu. Certain critical parameters that affect the properties and fracture mechanisms of harmonic-structure pure Cu were investigated and are discussed in detail. The Box–Behnken design was used to design the experiments to determine the correlation between the process parameters and mechanical properties. The results show that the parameters (rotation speed, mechanical milling time, and powder-to-ball ratio) affect the microstructure characteristics and influence the mechanical performance, including the fracture mechanisms of harmonic-structure pure Cu specimens. The best combination values of the ultimate tensile strength (UTS) and elongation were found to be 272 MPa and 46.85%, respectively. This combination of properties can be achieved by applying an optimum set of process parameters: a rotation speed of 200 rpm; mechanical milling time of 17.78 h; and powder-to-ball ratio of 0.065. The superior UTS and elongation of the harmonic-structure pure Cu were found to be related to the delay of void and crack initiation in the core and shell interface regions, which in turn were controlled by the degree of strength variation between these regions.

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Synergic Combination of Strength and Ductility through Both Grain Refinement and Precipitation in Al_0.3CoCrNi Medium‐Entropy Alloy

et al. 2023

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To improve the tensile properties of Al0.3CoCrNi (at%), herein, medium‐entropy alloys at room temperature, high‐pressure torsion (HPT), and appropriate annealing are presented. Severe deformation due to HPT causes fine grains and evenly distributed B2 and σ precipitates with a nanometer scale through an annealing procedure. A synergic combination of yield strength over 1.0 GPa and uniform elongation over 25% is obtained due to the simultaneous utilization of both grain refinement and precipitation strengthening.

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Ultra-strong and strain-hardenable ultrafine-grained medium-entropy alloy via enhanced grain-boundary strengthening

Cited by 50 publications

References 32 publications

Harnessing instability for work hardening in multi-principal element alloys

Harnessing instability for work hardening in multi-principal element alloys

Fabrication of Copper of Harmonic Structure: Mechanical Property-Based Optimization of the Milling Parameters and Fracture Mechanism

Synergic Combination of Strength and Ductility through Both Grain Refinement and Precipitation in Al_0.3CoCrNi Medium‐Entropy Alloy

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Ultra-strong and strain-hardenable ultrafine-grained medium-entropy alloy via enhanced grain-boundary strengthening

Cited by 50 publications

References 32 publications

Harnessing instability for work hardening in multi-principal element alloys

Harnessing instability for work hardening in multi-principal element alloys

Fabrication of Copper of Harmonic Structure: Mechanical Property-Based Optimization of the Milling Parameters and Fracture Mechanism

Synergic Combination of Strength and Ductility through Both Grain Refinement and Precipitation in Al0.3CoCrNi Medium‐Entropy Alloy

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Synergic Combination of Strength and Ductility through Both Grain Refinement and Precipitation in Al_0.3CoCrNi Medium‐Entropy Alloy