Nowadays the development of high-field magnets strongly relies on the performance of superconducting materials.Iron-based superconductors(IBSs)exhibit high upper critical fields and low electromagnetic anisotropy,maki...Nowadays the development of high-field magnets strongly relies on the performance of superconducting materials.Iron-based superconductors(IBSs)exhibit high upper critical fields and low electromagnetic anisotropy,making them particularly attractive for high-field applications,especially in particle accelerator magnets,nuclear magnetic resonance spectrometers,medical magnetic resonance imaging systems and nuclear fusion reactors.Herein,through an industrially scalable manufacturing strategy,a practical-level critical current density up to 1.1×10^(5)A cm^(-2)at4.2 K in an external magnetic field of 10 T was achieved in Cu/Ag composite-sheathed Ba_(1-x)K_(x)Fe_(2)As_(2)(Ba122)superconducting tapes.The preparation strategy combines flat rolling to induce grain texture and subsequent hot-isostaticpressing densification.By varying the parameters of rolling,the degree of grain texture was engineered.It is found that the transport properties of the Ba122 tapes can be enhanced by applying a large amount of deformation during rolling,which can be attributed to the improved degree of c-axis texture.Microstructure characterizations on the highest-performance tape demonstrate that the Ba122 phase has a uniform element distribution and small grains with good connectivity.Grain boundary pinning is consequently enhanced as proved by large currents circulating through the sample even at 25 K.Our work proves that Cu/Ag composite-sheathed Ba122 superconducting tapes can be a promising competitor for practical high-field applications in terms of the viable,scalable and cost-effective fabrication strategy applied and the high transport properties achieved in this work.展开更多
The grain size, textures and grain boundary plane distributions in a cold-rolled and annealed ferritic stainless steel were investigated by means of EBSD techniques. The results show that, following cold rolling with ...The grain size, textures and grain boundary plane distributions in a cold-rolled and annealed ferritic stainless steel were investigated by means of EBSD techniques. The results show that, following cold rolling with the thickness reduction of 85%, relatively low temperature （780℃） annealing brings an extremely sluggish grain growth and no grain texture develops when the annealing time varies from 5 min to 480 min. The free energy reduction of the system is mainly caused by the grain boundary plane re-orientation in addition to minor grain growth because the distributions of grain boundary planes are moderately preferred on { 100} according to the five parameter analyses （FPA） concerning the grain boundary plane characteristics. However, in the case of high-temperature （1 000 ℃） annealing, the average grain size does not increase until annealing time is prolonged to 90 min, after which extensive grain growth occurs and strong {100}（hkl） texture emerges whereas nearly random grain boundary plane distributions are observed. The free energy reduction of the system is most likely attributed to the selective growth.展开更多
Commercial grain oriented silicon steel was cold rolled to thickness from 0.06 to 0.10 mm by cross shear rolling, then annealed in vacuum or a hydrogen atmosphere furnace. Deformation textures of the sheets were resea...Commercial grain oriented silicon steel was cold rolled to thickness from 0.06 to 0.10 mm by cross shear rolling, then annealed in vacuum or a hydrogen atmosphere furnace. Deformation textures of the sheets were researched by ODF method and reverse pole figure quantitative analyses. The results indicate that: in the condition of the cross shear rolling, the deformation texture of rolled sheet is generally similar to that of conventional rolled sheet, however, the texture distribution through the thickness is asymmetrical. With mismatch speed ratio increasing, the amount of Goss texture increases. With reduction ratio increasing, the intensity of γ-fiber becomes strong.展开更多
Texture is one of the important factors affecting sheet metal forming performance.The through-thickness texture gradient during the hot-rolling process of twinning induced plasticity（TWIP）steel sheet was investigate...Texture is one of the important factors affecting sheet metal forming performance.The through-thickness texture gradient during the hot-rolling process of twinning induced plasticity（TWIP）steel sheet was investigated using electron backscatter diffraction and X-ray diffraction.With increasing reduction of the TWIP steel,the fraction of∑1 decreased,whereas the fractions of∑3,∑9,and∑27increased.During 53%reduction,a similar trend could be found from its surface to the center.The gradients of intensities of the fibers decreased with increasing hot-rolling reduction.The intensities of face-centered cubic（fcc）shear textures E and Y were higher in the center than that at the surface for both reductions.During 20% reduction,the intensity of fcc plain strain texture S orientation increased from the center to the surface.展开更多
Main attention of this paper was devoted to studying the effect of solidification texture on microstructure（phase constituents,grain morphology,and magnetic domain structure） of polycrystalline Fe_（82）Ga_（18） sa...Main attention of this paper was devoted to studying the effect of solidification texture on microstructure（phase constituents,grain morphology,and magnetic domain structure） of polycrystalline Fe_（82）Ga_（18） sample.The alloy was melted using button arc melting and solidified in water-cooled copper mold.Optical microscope（OM） results confirm the development of large columnar grains in the solidification microstructure.Phase constitution and magnetic domain structures of the sample were studied by X-ray diffraction（XRD） and magnetic force microscopy（MFM）.Results show a single-phase solid solution with an A2 structure for the sample which consists of regularly aligned magnetic domains.Although some maze-like subdomains are found in few regions,well-aligned stripe-like domains are predominant patterns in the sample.It demonstrates the high dependence of grain morphology and magnetic domain structure upon a preferred crystallographic direction during solidification.展开更多
基金supported by the National Key R&D Program of China (2018YFA0704200 and 2017YFE0129500)the National Natural Science Foundation of China (51861135311, U1832213 and 51721005)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences (XDB25000000)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences (QYZDJ-SSWJSC026)
文摘Nowadays the development of high-field magnets strongly relies on the performance of superconducting materials.Iron-based superconductors(IBSs)exhibit high upper critical fields and low electromagnetic anisotropy,making them particularly attractive for high-field applications,especially in particle accelerator magnets,nuclear magnetic resonance spectrometers,medical magnetic resonance imaging systems and nuclear fusion reactors.Herein,through an industrially scalable manufacturing strategy,a practical-level critical current density up to 1.1×10^(5)A cm^(-2)at4.2 K in an external magnetic field of 10 T was achieved in Cu/Ag composite-sheathed Ba_(1-x)K_(x)Fe_(2)As_(2)(Ba122)superconducting tapes.The preparation strategy combines flat rolling to induce grain texture and subsequent hot-isostaticpressing densification.By varying the parameters of rolling,the degree of grain texture was engineered.It is found that the transport properties of the Ba122 tapes can be enhanced by applying a large amount of deformation during rolling,which can be attributed to the improved degree of c-axis texture.Microstructure characterizations on the highest-performance tape demonstrate that the Ba122 phase has a uniform element distribution and small grains with good connectivity.Grain boundary pinning is consequently enhanced as proved by large currents circulating through the sample even at 25 K.Our work proves that Cu/Ag composite-sheathed Ba122 superconducting tapes can be a promising competitor for practical high-field applications in terms of the viable,scalable and cost-effective fabrication strategy applied and the high transport properties achieved in this work.
基金Project(50974147)supported by the National Natural Science Foundation of ChinaProject(2009ZRB01176)supported by the Natural Science Foundation of Shandong Province,China
文摘The grain size, textures and grain boundary plane distributions in a cold-rolled and annealed ferritic stainless steel were investigated by means of EBSD techniques. The results show that, following cold rolling with the thickness reduction of 85%, relatively low temperature （780℃） annealing brings an extremely sluggish grain growth and no grain texture develops when the annealing time varies from 5 min to 480 min. The free energy reduction of the system is mainly caused by the grain boundary plane re-orientation in addition to minor grain growth because the distributions of grain boundary planes are moderately preferred on { 100} according to the five parameter analyses （FPA） concerning the grain boundary plane characteristics. However, in the case of high-temperature （1 000 ℃） annealing, the average grain size does not increase until annealing time is prolonged to 90 min, after which extensive grain growth occurs and strong {100}（hkl） texture emerges whereas nearly random grain boundary plane distributions are observed. The free energy reduction of the system is most likely attributed to the selective growth.
基金National Natural Science Foundation of China!(No. 59671037).
文摘Commercial grain oriented silicon steel was cold rolled to thickness from 0.06 to 0.10 mm by cross shear rolling, then annealed in vacuum or a hydrogen atmosphere furnace. Deformation textures of the sheets were researched by ODF method and reverse pole figure quantitative analyses. The results indicate that: in the condition of the cross shear rolling, the deformation texture of rolled sheet is generally similar to that of conventional rolled sheet, however, the texture distribution through the thickness is asymmetrical. With mismatch speed ratio increasing, the amount of Goss texture increases. With reduction ratio increasing, the intensity of γ-fiber becomes strong.
基金Sponsored by National Natural Science Foundation of China(50934011)Shanghai Leading Academic Discipline Projectof China(J51402)
文摘Texture is one of the important factors affecting sheet metal forming performance.The through-thickness texture gradient during the hot-rolling process of twinning induced plasticity（TWIP）steel sheet was investigated using electron backscatter diffraction and X-ray diffraction.With increasing reduction of the TWIP steel,the fraction of∑1 decreased,whereas the fractions of∑3,∑9,and∑27increased.During 53%reduction,a similar trend could be found from its surface to the center.The gradients of intensities of the fibers decreased with increasing hot-rolling reduction.The intensities of face-centered cubic（fcc）shear textures E and Y were higher in the center than that at the surface for both reductions.During 20% reduction,the intensity of fcc plain strain texture S orientation increased from the center to the surface.
基金support of Center of Excellence for High Performance Materials (CEPMAT) at University of Tehran, Sahand University of Technology
文摘Main attention of this paper was devoted to studying the effect of solidification texture on microstructure（phase constituents,grain morphology,and magnetic domain structure） of polycrystalline Fe_（82）Ga_（18） sample.The alloy was melted using button arc melting and solidified in water-cooled copper mold.Optical microscope（OM） results confirm the development of large columnar grains in the solidification microstructure.Phase constitution and magnetic domain structures of the sample were studied by X-ray diffraction（XRD） and magnetic force microscopy（MFM）.Results show a single-phase solid solution with an A2 structure for the sample which consists of regularly aligned magnetic domains.Although some maze-like subdomains are found in few regions,well-aligned stripe-like domains are predominant patterns in the sample.It demonstrates the high dependence of grain morphology and magnetic domain structure upon a preferred crystallographic direction during solidification.
