| 1. |
- Wei, Daixiu, et al.
(författare)
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Development of strong and ductile metastable face-centered cubic single-phase high-entropy alloys
- 2019
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Ingår i: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 181, s. 318-330
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Tidskriftsartikel (refereegranskat)abstract
- Face-centered cubic (fcc)-phase high-entropy alloys (HEAs) have attracted much academic interest, with the stacking fault energy (SFE) playing an important role in regulating their mechanical behaviors. Here, we revealed the principles for regulating both the elastic and plastic behaviors by composition modification and Mo addition in an fcc-phase quaternary CoCrFeNi system with the assistance of ab initio and thermodynamics calculations. An increase in Co content and a decrease in Fe and Ni contents reduced the fcc phase stability and SFE, but enhanced the elastic modulus, anisotropy, and lattice friction stress. A minor substitution of Co by Mo increased the lattice constant, but decreased the SFE and elastic modulus. Based on these findings, we developed a series of strong and ductile metastable fcc-phase CoxCr25(FeNi)(70-x)Mo-5 (x = 30, 40, 50) HEAs with mechanical properties superior to those of the CoCrFeNi HEM. The careful investigation revealed that the enhanced mechanical properties are due to the Mo-addition-induced strengthening accompanied with a low-SFE-induced restriction of planar behavior of dislocations, mechanical twinning, and strain-induced martensitic transformation. The findings shed light on the development of high-performance HEAs.
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| 2. |
- Wei, Daixiu, et al.
(författare)
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Novel Co-rich high entropy alloys with superior tensile properties
- 2019
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Ingår i: Materials Research Letters. - : Taylor & Francis. - 2166-3831. ; 7:2, s. 82-88
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Tidskriftsartikel (refereegranskat)abstract
- We developed a series of Co-rich CoxCr25(FeNi)(75-x) (x = 35, 45, 55, 65) high entropy alloys with improved strength and/or ductility, derived from lowering the stacking fault energy (SFE) and reducing the fcc phase stability of the equiatomic CoCrFeNi alloy. Thermodynamics and ab initio calculations demonstrated that increasing Co while decreasing Fe and Ni concentrations lower the SFE and reduce the fcc phase stability. The Co35Cr25Fe20Ni20 and Co45Cr25Fe15Ni15 alloys with single fcc phase, exhibit superior tensile properties, contributing to the twinning and fcc -> hcp martensitic transformation. The present study offers a guideline for designing high-performance high entropy alloys. [GRAPHICS] IMPACT STATEMENT A series of novel Co-rich non-equiatomic high entropy alloys with enhanced tensile properties were developed by lowering the stacking fault energy and reducing the phase stability of equiatomic CoCrFeNi alloy.
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| 3. |
- Wei, Daixiu, et al.
(författare)
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Si-addition contributes to overcoming the strength-ductility trade-off in high-entropy alloys
- 2022
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Ingår i: International journal of plasticity. - : Elsevier BV. - 0749-6419 .- 1879-2154. ; 159
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Tidskriftsartikel (refereegranskat)abstract
- Face-centered cubic single-phase high-entropy alloys (HEAs) containing multi-principal transition metals have attracted significant attention, exhibiting an unprecedented combination of strength and ductility owing to their low stacking fault energy (SFE) and large misfit parameter that creates severe local lattice distortion. Increasing both strength and ductility further is challenging. In the present study, we demonstrate via meticulous experiments that the CoCrFeNi HEA with the addition of the substitutional metalloid Si can retain a single-phase FCC structure while its yield strength (up to 65%), ultimate strength (up to 34%), and ductility (up to 15%) are simultaneously increased, owing to a synthetical effect of the enhanced solid solution strengthening and a reduced SFE. The dislocation behaviors and plastic deformation mechanisms were tuned by the addition of Si, which improves the strain hardening and tensile ductility. The present study provides new strategies for enhancing HEA performance by targeted metalloid additions.
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