| 1. |
- Reddy, S. R., et al.
(författare)
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High Strain Rate Superplastic Flow and Fracture Characteristics of a Fine-Grained Eutectic High Entropy Alloy
- 2024
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Ingår i: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. - 1073-5623. ; 55, s. 173-182
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Tidskriftsartikel (refereegranskat)abstract
- A fine-grained micro-duplex AlCoCrFeNi2.1 eutectic high entropy alloy exhibited high strain rate superplasticity with an elongation to failure of ~ 960 pct at 1173 K and a strain rate of 10-1 s-1. Optimum superplasticity was associated with a strain rate sensitivity of ~ 0.5, and there were transitions to non-superplastic flow with strain rate sensitivities of < 0.5 at both low and high strain rates. Superplasticity is attributed to grain boundary sliding with the observed retention of an equiaxed grain morphology, with some grain growth. Cavities with dimensions in the range of 1 to 5 μm were observed in specimens pulled to failure. Although analysis revealed that cavity nucleation is likely under the experimental conditions, cavity growth was slow because of control by a plasticity growth rate that was proportional to the cavity size. Graphical Abstract: [Figure not available: see fulltext.]
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| 2. |
- Seelam, Rajasekhar Reddy, et al.
(författare)
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Engineering heterogeneous microstructure by severe warm-rolling for enhancing strength-ductility synergy in eutectic high entropy alloys
- 2019
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Ingår i: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - : Elsevier BV. - 0921-5093. ; 764
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure and mechanical properties of a (L12+B2) AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) processed by severe warm-rolling were investigated in the present work. The EHEA was successfully warm-rolled up to 90% reduction in thickness at 400 °C, 600 °C and 750 °C. Considerable differences in the microstructural evolution were identified during warm-rolling at the three temperatures. The L12 phase in the EHEA was disordered due to severe warm-rolling at 400 °C and 750 °C, while a predominantly ordered structure was retained in the EHEA warm-rolled at 600 °C. This anomalous behavior could be adequately explained by the sluggish ordering kinetics at lower deformation temperatures. The EHEA warm-rolled at 750 °C showed an extremely heterogeneous microstructure featured by retained lamellar regions comprising of B2 and FCC lamellae with dispersed B2 phase inside the FCC, whereas the non-lamellar regions showed a mixture of ultrafine to nanocrystalline disordered FCC, ordered B2 and Cr-rich σ phases. The non-lamellar regions were scarce and nearly absent in the EHEA 90% warm-rolled at 600 °C and 400 °C, respectively. The remarkably heterogeneous microstructure of EHEA warm-rolled at 750 °C resulted in outstanding strength-ductility combination with tensile strength ~1635 MPa and elongation to failure ~18%. The results indicated tremendous potential for achieving superior mechanical properties in heterogeneous EHEAs processed by severe warm-rolling.
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| 3. |
- Seelam, Rajasekhar Reddy, et al.
(författare)
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Microstructural design by severe warm-rolling for tuning mechanical properties of AlCoCrFeNi2.1 eutectic high entropy alloy
- 2019
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Ingår i: Intermetallics. - : Elsevier BV. - 0966-9795. ; 114:nov.
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Tidskriftsartikel (refereegranskat)abstract
- The influence of severe warm-rolling and subsequent annealing on the microstructure and mechanical properties in an AlCoCrFeNi2.1 high entropy alloy consisting of a lamellar arrangement of ordered L1(2) and B2 phases was studied. For this purpose, the as-cast EHEA was severely warm-rolled up to 90% reduction in thickness at selected temperatures of 400 degrees C, 600 degrees C, and 750 degrees C. The severely warm-rolled EHEAs were further annealed at temperatures ranging from 800 degrees C to 1200 degrees C for 1 h. Warm-rolling resulted in a unique disordering behavior of the L1(2) depending on the temperature of warm-rolling. However, the B2 phase maintained the ordered structure irrespective of the warm-rolling temperature. The EHEA warm-rolled at 400 degrees C and 600 degrees C showed a predominantly lamellar microstructure, while the EHEA warm-rolled at 750 degrees C showed a novel heterogeneous microstructure featured by a mixture of lamellar and non-lamellar regions. Annealing of the 90% warm-rolled materials resulted in the formation of predominantly duplex microstructures consisting of disordered FCC and B2 phases. The EHEA warm-rolled at 400 degrees C and 600 degrees C showed high strength but rather limited ductility, which could be improved upon annealing. Remarkably, the EHEA warm-rolled at 750 degrees C showed the most outstanding properties featured by exceptional strength-ductility combination owing to the novel heterogeneous microstructure. Annealing of the heterogeneous EHEA resulted in the deterioration of the strength-ductility balance owing to the annihilation of the heterogeneous microstructure, being replaced by a microduplex structure.
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| 4. |
- Yeh, Jienwei, et al.
(författare)
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Preface- Materials Chemistry and Physics
- 2018
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584. ; 210, s. 1-1
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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