| 1. |
- Fenstermacher, M.E., et al.
(författare)
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DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
- 2022
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:4
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Tidskriftsartikel (refereegranskat)abstract
- DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.
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| 2. |
- Liu, Z. Y., et al.
(författare)
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Micromechanical characterization of casting-induced inhomogeneity in an Al0.8CoCrCuFeNi high-entropy alloy
- 2011
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Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462. ; 64:9, s. 868-871
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Tidskriftsartikel (refereegranskat)abstract
- The microstructural features and micromechanical behavior of individual phases in a cast Al0.8CoCrCuFeNi high-entropy alloy (HEA) were characterized by high-resolution scanning electron microscopy and micro-compression tests. Use of neutron diffraction enabled the detection of a new phase which was otherwise unobservable by conventional X-ray diffraction. The identified phase constitution agreed well with the compositional analysis and the micro-compression results. The delicate microscale characterization of individual phase provides new insights for the design of novel HEAs with desirable mechanical properties. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 3. |
- Hu, Q., et al.
(författare)
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Anomalous thermal expansion in the deep super-cooled liquid region of a ZrCuAlAg bulk metallic glass
- 2018
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Ingår i: Materials Research Letters. - : Informa UK Limited. - 2166-3831. ; 6:2, s. 121-129
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Tidskriftsartikel (refereegranskat)abstract
- Bulk metallic glasses (BMGs), like other glasses, soften in the super-cooled liquid region (SCLR). Here in this work, surprisingly, a large expansion is reported occurring in the deep SCLR of a Zr 47 Cu 37 Al 8 Ag 8 BMG. Nano-crystals (NCs) are found precipitated during the anomalous expansion of Zr 47 Cu 37 Al 8 Ag 8 , but also in the SCLR of Zr 43 Cu 41 Al 8 Ag 8 that exhibits a conventional softening. It is found that there is a steep composition and density change at the NCs/amorphous matrix transition region in the former alloy, and this transition region exerts a thermal stress of about 0.15 MPa to the surrounding super-cooled liquid (SCL) and drives the soft SCL to expand severely. (Figure presented) IMPACT STATEMENT An anomalous expansion, and particularly a large expansion instead of softening, is reported occurring in the deep SCLR of a Zr-based bulk metallic glass for the first time.
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| 4. |
- Ouyang, D. L., et al.
(författare)
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Influence of casting temperature on the castability and glass-forming ability of Zr-based bulk metallic glasses
- 2023
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Ingår i: Journal of Non-Crystalline Solids. - : Elsevier BV. - 0022-3093. ; 603
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Tidskriftsartikel (refereegranskat)abstract
- Both castability and glass-forming ability (GFA) are crucial for die-casting of Zr-based bulk metallic glass (BMG) components. In this work, a simple method is used to quantify the castability required for casting two SIM card slots with different designs, and to quantify the castability at different casting temperatures. It is found that the Zr55Cu30Ni5Al10 (Zr55) BMG has a wider optimal casting temperature region (in which glassy rods with a diameter of at least 5 mm can be formed) than that of Zr52.5Cu25Ni9.5Al7Ti6 (Zr52.5), which is consistent of the better GFA of the Zr55. In the optimal casting temperature region, however, the castability of Zr52.5 is significantly better than that of Zr55, because Zr52.5 has a lower melting point, a poorer wettability to the copper mold, and a higher optimal casting temperature. These results are helpful to guide the production of Zr-based BMG components.
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| 5. |
- Zhang, H., et al.
(författare)
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Novel high-entropy and medium-entropy stainless steels with enhanced mechanical and anti-corrosion properties
- 2018
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Ingår i: Materials Science and Technology. - : Informa UK Limited. - 1743-2847 .- 0267-0836. ; 34:5, s. 572-579
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Tidskriftsartikel (refereegranskat)abstract
- Novel high-entropy and medium-entropy stainless steels (MESS), containing a high amount of alloying elements, were designed and prepared by arc melting. These high-entropy and MESS possess a simple phase constitution, mainly solid solution phases, and noticeably exhibit excellent anti-corrosion properties in sulphuric acid. In particular, an austenitic Fe 65 Cr 13 Co 4.75 Mn 4.75 Mo 4.75 Ni 4.75 Cu 3 (at.-%) alloy has a higher hardness of 182 HV and better corrosion resistance than those of the 00Cr19Ni14Mn2 austenitic stainless steel prepared under the same condition; a ferritic precipitation hardening Fe 65 Cr 13 Al 3.167 Co 3.167 Mn 3.167 Mo 3.167 Ni 3.167 Ti 3.167 Cu 3 (at.-%) alloy was also developed, with a higher hardness of 584 HV and even better corrosion resistance.
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| 6. |
- Cheng, Q., et al.
(författare)
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Mechanistic origin of abnormal annealing-induced hardening in an AlCoCrFeNi 2.1 eutectic multi-principal-element alloy
- 2023
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Ingår i: Acta Materialia. - 1359-6454. ; 252
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Tidskriftsartikel (refereegranskat)abstract
- Annealing-induced hardening, also known as anneal hardening, has been often observed in cold-worked solid solution alloys. Here, we report a peculiar case of annealing-induced hardening in a dual-phase (FCC + B2) as-cast AlCoCrFeNi2.1 eutectic multi-principal-element alloy (EMPEA) without any prior cold-working history. Investigation of the relative hardness contribution of the two phases by nanoindentation experiments revealed that, although both the FCC and B2 phases harden with increasing annealing temperatures, only the FCC phase showed a similar hardening behavior while the B2 phase hardened with increasing annealing temperature. The abnormal hardening in the dual-phase AlCoCrFeNi2.1 is thus proposed to result from the hardening of the FCC phase, which was caused by the ordering strengthening from the L12 phase embedded in the FCC matrix. This ordering strengthening is further supported by the fact that the volume fraction of the L12 ordered particles exhibit a similar peak as that of the hardness value of the FCC phase. By contrast, the growth of BCC particles within the B2 matrix phase was observed, which led to an increased volume fraction of BCC particles. Transmission electron microscopy observations reveal that the BCC particles were observed as strong pinning sites against dislocation motion, which could explain the temperature-dependent hardening behavior of the B2 phase measured by nanoindentation experiments. In this study, a quantitative evaluation of strengthening contributions from the L12 and BCC particles was also performed to understand the mechanical behavior of the alloy.
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| 7. |
- Hu, Q., et al.
(författare)
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Invar effect of Fe-based bulk metallic glasses
- 2018
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Ingår i: Intermetallics. - : Elsevier BV. - 0966-9795. ; 93, s. 318-322
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Tidskriftsartikel (refereegranskat)abstract
- Invar alloys have a wide application owing to its low expansion characteristics. Recently, it is revealed that some Fe-based bulk metallic glasses (BMGs), which have much higher strength than that of traditional Fe-Ni Invar alloys, also have the Invar effect. Combining the low expansion of the Invar effect and the good mechanical properties of Fe-based BMGs has an attractive potential for applications, for which firstly systematic study on the Invar effect of Fe-based BMGs is needed. In this work, the thermal expansion of 14 FeSiPCBM, (Fe,Co)BSiNb, FeNiPC and FeMoPCB BMGs are investigated. The results show all the alloys have the Invar effect, but can be categorized in two types, depending on whether the low expansion occurs in a wide temperature range below the Curie temperature Tc, or in a narrow temperature range near Tc. It is found the former type of alloys have lower Tc and saturation magnetic induction density, i.e., weaker magnetic properties. The substitution of Fe by Co and Ni weakens the Invar effect. These findings are explained based on the characteristics of the amorphous structure and the Bethe-Slater curve. The findings in this paper help to further develop low expansion Fe-based BMGs.
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| 8. |
- Xu, X., et al.
(författare)
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Effects of mixing enthalpy and cooling rate on phase formation of Al x CoCrCuFeNi high-entropy alloys
- 2019
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Ingår i: Materialia. - : Elsevier BV. - 2589-1529. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the influence of mixing enthalpy and cooling rate on phase formation and selected the melt-spun Al x CoCrCuFeNi (x = 0, 0.1, 0.5, 0.8 and 1.0 in molar ratios) high-entropy alloys (HEAs) as a model system. The mean mixing enthalpy (ΔH mix ) of the alloy system is tuned from positive to negative by increasing Al molar ratios while the mixing entropy (ΔS mix ) only has an insignificant variation. Microstructure analyses revealed that the dominant phase in the Al x CoCrCuFeNi HEAs changes from a face-centered cubic (FCC) to body-centered cubic (BCC) structure with the variation of the ΔH mix . Accompanying with phase changing, the lattice constant of the FCC phase increases linearly with Al molar ratio regardless of cooling rate, indicating that the lattice expansion caused by the substitutional alloying of Al plays an important role in the phase evolution, in addition to the effect of the ΔH mix . The increasingly negative enthalpy ΔH mix with Al addition also leads to more pronounced phase separation with the formation of ordered intermetallic phases in the BCC-dominant HEAs than the FCC-dominant ones. Interestingly, when the magnitude of the mean ΔH mix is small, both the coarsening of Cu-rich nanophase and decomposition of the solid-solution phase in the Al 0.5 CoCrCuFeNi HEA are suppressed. This observation is in line with thermodynamic predictions that a weak ΔH mix benefits the stabilization of the solid-solution phase.
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| 9. |
- Zhou, X., et al.
(författare)
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Study on the Cavity Forming Induced by a Gas Jet Impinging on a Liquid Surface Based on a Deformed Mesh Method
- 2021
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Ingår i: JOM. - : Springer. - 1047-4838 .- 1543-1851. ; 73:10, s. 2953-2962
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Tidskriftsartikel (refereegranskat)abstract
- The current study focuses on the cavity formation induced by jet impingement with the help of numerical simulations based on a deformed mesh method. The interface between the liquid phase and gas phase separates the calculation domain into two single-phase domains, which exchange momentum data except for mass transfer. For the subsonic jet flow, the results show that the cavity depth is a decreasing function when the blowing height is increased, while the cavity diameter increases when increasing the blowing height. In addition, larger diameter of the nozzle will result in a deeper cavity because the jet flow attenuation becomes weaker. The simulation result shows good agreement with that of the theoretical equation on the cavity depth and diameter for the subsonic jet flow. In addition, the cavity formation created by the supersonic flow, which is treated as a compressible flow, can also be described by the developed model.
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| 10. |
- Zhang, H., et al.
(författare)
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Effect of High Configuration Entropy and Rare Earth Addition on Boride Precipitation and Mechanical Properties of Multi-principal-Element Alloys
- 2017
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Ingår i: Journal of Materials Engineering and Performance. - : Springer Science and Business Media LLC. - 1059-9495 .- 1544-1024. ; 26:8, s. 3750-3755
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Tidskriftsartikel (refereegranskat)abstract
- A series of multi-principal-element (MPE) alloys have been prepared by adding Ni, Mn, Al, Cu and Y into the reference CoCrFe-B alloy. The microstructure and mechanical properties of these MPE alloys have been investigated thoroughly. It is found that the addition of the elements can inhibit boride precipitation in the designed alloys and the solid solution strengthening effect induced by interstitial boron atoms is more significant than that by boride precipitation. The MPE alloys with the fcc phase as the main solid solution phase have a higher boron solubility and hence less boride precipitation, than those with the bcc phase as the main solid solution phase. The addition of yttrium can improve the boron solubility, decrease boride precipitation, control the boride morphology and, importantly, simultaneously improve the compressive strength and ductility of boron-containing MPE alloys.
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