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Microstructure and crystal growth direction of Al-Cu alloy 被引量:1
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作者 陈体军 李向威 +1 位作者 郭海洋 郝远 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2015年第5期1399-1409,共11页
The microstructures and crystal growth directions of permanent mould casting(PMC) and directionally solidified(DS) Al-Cu alloys with different contents of Cu were investigated. Simultaneously, the effects of pouri... The microstructures and crystal growth directions of permanent mould casting(PMC) and directionally solidified(DS) Al-Cu alloys with different contents of Cu were investigated. Simultaneously, the effects of pouring temperature on the microstructure and crystal growth direction of permanent mould casting pure Al were also discussed. The results indicate that the α(Al) crystals in the pure Al do not always keep common columnar grains, but change from the columnar grains to columnar dendrites with developed arms as the pouring temperature rises. The growth direction also varies with the change of pouring temperature. Cu element has similar effects on the microstructures of the PMC and DS casting Al-Cu alloys and the α(Al) crystals gradually change from columnar crystals in turn to columnar dendrites and developed equiaxed dendrites as the Cu content increases. The crystal growth direction in the PMC alloys gradually approaches (110) orientation with increasing Cu content. But the resulting crystals with growth direction of (110) do not belong to feathery grains. There are also no feathery grains to form in all of the DS Al-Cu alloys. 展开更多
关键词 Al-Cu alloy directional solidification crystal growth direction permanent mould casting MICROSTRUCTURE
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Microstructure and crystal growth direction of Al-Mg alloy
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作者 Ti-jun Chen Hai-yang Guo +1 位作者 Xiang-wei Li Yuan Hao 《China Foundry》 SCIE CAS 2015年第2期129-135,共7页
The microstructures and crystal growth directions of permanent mould casting and directionally solidified Al-Mg al oys with different Mg contents have been investigated. The results indicate that the effect of Mg cont... The microstructures and crystal growth directions of permanent mould casting and directionally solidified Al-Mg al oys with different Mg contents have been investigated. The results indicate that the effect of Mg content on microstructure is basical y same for the al oys prepared by these two methods. The primary grains change from cel ular crystals to developed columnar dendrites, and then to equiaxed dendrites as the Mg content is increased. Simultaneously, both the cel ular or columnar grain region and the primary trunk spacing decrease. Al of these changes are mainly attributed to the constitutional supercooling resulting from Mg element. Comparatively, the cellular or columnar crystals of the directionally solidified alloys are straighter and more paral el than those of the permanent mould casting al oys. These have straight or wavy grain boundaries, one of the most important microstructure characteristics of feathery grains. However, the transverse microstructure and growth direction reveal that they do not belong to feathery grains. The Mg seemingly can affect the crystal growth direction, but does not result in the formation of feathery grains under the conditions employed in the study. 展开更多
关键词 Al-Mg alloy MICROSTRUCTURE crystal growth direction feathery grains permanent mould casting directional solidifi cation
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LYOTROPIC AND THERMOTROPIC LIQUID CRYSTALL INE TRIALKYL CELLULOSES OBTAINED DIRECTLY FROM CELLULOSE ACETATE IN DIMETHYL SULFOXIDE
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作者 Xin Gui LI, and Mei Rong HUANG~1 Institute of Membrane Separation Engineering, ~1Department of Textile Chemical Engineering, Tianjin Institute of Textite Science and Technology, Tianjin 300160 《Chinese Chemical Letters》 SCIE CAS CSCD 1992年第7期573-576,共4页
Highly substituted n-atkyl celluloses with sidechains 3 to 10 carbon atoms long have been prepared from cellulose acetate, sodium hydroxide and n-alkyl bromides with dimethyl sulfoxide as solvent. Synthetic conditions... Highly substituted n-atkyl celluloses with sidechains 3 to 10 carbon atoms long have been prepared from cellulose acetate, sodium hydroxide and n-alkyl bromides with dimethyl sulfoxide as solvent. Synthetic conditions of n-alkyl celluloses were studied with respect to reaction temperature, time and yield. The molecular structure of the n-alkyl celluloses, which were obtained as white powders or as sticky, soft and birefringent solids at room temperature, was investigated by IR and NMR spectra and elemental analysis. The highly substituted n-alkyl celluloses all exhibited both therotropic and lyotropic liquid crystalline cholesteric phases in some non-polar solvents. The metting behavior and solubility of the n-alkyl celluloses were examined. 展开更多
关键词 LYOTROPIC AND THERMOTROPIC LIQUID CRYSTALL INE TRIALKYL CELLULOSES OBTAINED directLY FROM CELLULOSE ACETATE IN DIMETHYL SULFOXIDE
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Experience in the Production of Horizontal Ingots of Platinum Metals and Alloys
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作者 LEVCHENKO S. D. VERSHININA E. N. 《贵金属》 CAS CSCD 北大核心 2012年第A01期250-252,共3页
The quality of semi-products of platinum metals and alloys, produced by way of plastic working, essentially depends on or, in many cases, is completely determined by the quality of ingots. Plastic working does not mak... The quality of semi-products of platinum metals and alloys, produced by way of plastic working, essentially depends on or, in many cases, is completely determined by the quality of ingots. Plastic working does not make it possible to eliminate or localize metallurgical defects. In many cases it promotes the occurence thereof. Low-rate casting with directional crystallization can ensure the production of dense ingots free of non-metallic inclusions, shrinkage and gas weakness, with observance of certain temperature/rate modes. After comparative tests of vertical and horizontal molds, preference has been given to horizontal water-cooled molds, allowing to cast all alloys in the conditions of directional crystallization. 展开更多
关键词 INGOT directional crystallization low-rate casting MOLD crystallization front metallurgical defect STICKING pyrometallurgical refining
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Analysis of heat transfer processes for sapphire growth by horizontal directed crystallization method
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作者 Yu.V.Klunnikova S.P.Malyukov +1 位作者 A.V.Filimonov N.Zhang 《Journal of Advanced Dielectrics》 CAS 2020年第1期2-8,共7页
This research summarizes the analytical and experimental results of heat-transfer processes influence on defects formation during sapphire crystal growth by horizontal directed crystallization method(HDC).The shape of... This research summarizes the analytical and experimental results of heat-transfer processes influence on defects formation during sapphire crystal growth by horizontal directed crystallization method(HDC).The shape of solid-melt interface significantly influences the process of sapphire crystals growth by this method.We receive the Stefan problem solution for sapphire crystals growth.It allows investigating the crystal growth process and the related factors(thermal stresses on different stages of growth process),their influence on defects formation.We investigate the main reasons for the formation of defective structures of the solid phase of sapphire crystals and the influence of thermal unit construction,the crystal geometry on the quality of the resulting sapphire crystal.We study the structure formation process,impurity distribution,and the nature of the defects in the crystal during it growth. 展开更多
关键词 Crystal growth directional crystallization DEFECTS internal stresses analytical methods
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Spontaneous hierarchical surface engineering of minerals through coupled dissolution-precipitation chemistry 被引量:1
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作者 Jinyang Jiang Jiawen Zhang +4 位作者 Lanxin Wang Zeyu Lu Fengjuan Wang Zhiyong Liu Hongbo Zeng 《Aggregate》 EI CAS 2024年第1期460-472,共13页
Peculiar hierarchical microstructures in creatures inspire modern material design with distinct functionalities.Creatures can effortlessly construct sophisticated yet long-range ordered microstructure across bio-membr... Peculiar hierarchical microstructures in creatures inspire modern material design with distinct functionalities.Creatures can effortlessly construct sophisticated yet long-range ordered microstructure across bio-membrane through ion secretion and precipitation.However,microstructure biomimicry in current technology generally requires elaborate,point-by-point fabrication.Herein,a spontaneous yet controllable strategy is developed to achieve surface microstructure engineering through a natural surface phenomenon similar to ion secretion-precipitation,that is,coupled dissolution-precipitation.A series of hierarchical microstructures on mineral surfaces in fluids with tunable morphology,orientation,dimension,and spatial distribution are achieved by simply controlling initial dissolution and fluid chemistry.In seawater,long-range ordered film of vertically aligned brucite flakes forms through interfacial dissolution,nucleation,and confinement-induced orientation of flakes with vertically grown{110}plane,on the edge of which,fusiform aragonite epitaxially precipitates.With negligible initial surface dissolution,prismatic aragonite epitaxially grows on a calcite polyhedron-packed surface.By tuning fluid chemistry,closely packed calcite polyhedron and loosely packed calcite micro-pillars are engineered through rapid and retarded precipitation,respectively.Surprisingly,the spontaneously grown microstructures resemble those deliberately created by human or found in nature,and tremendously modulate surface functionality.These findings open new possibilities for facile and customizable engineering of microstructural surfaces,hierarchical heterostructures,and biomimetic materials. 展开更多
关键词 directional crystallization dissolution-precipitation chemistry hierarchical microstructures spontaneous growth surface engineering
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Modes of Grain Selection in Spiral Selector during Directional Solidification of Nickel-base Superalloys 被引量:11
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作者 Xiangbin Meng Qi Lu +6 位作者 Jinguo Li Tao Jin Xiaofeng Sun Jun Zhang ZhongqiangChen Yanhui Wang Zhuangqi Hu 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2012年第3期214-220,共7页
The modes of grain selection in spiral selector were investigated by both a ProCAST simulation and experimental confirmation.The results show that the efficiency of grain selection in starter block is associated with ... The modes of grain selection in spiral selector were investigated by both a ProCAST simulation and experimental confirmation.The results show that the efficiency of grain selection in starter block is associated with the geometry shape.At the early stage of grain selection,the optimization of grain orientation is dominated by competitive grain growth,but the optimization of grain orientation in starter block is gradually dominated by geometry shape at the later stage of grain selection.Besides,the spiral part could also optimize the orientation of the selected single crystal when the initial angle is large enough,and the single crystal selection in spiral parts with different pitch lengths and initial angles is dominated by different modes.The simulation results agree well with experimental ones. 展开更多
关键词 Ni-base single crystal superalloys Competitive grain growth Geometry shape directional solidification Spiral selector
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Selectivity of Crystal Growth Direction in Layered Double Hydroxides
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作者 赵芸 梁吉 +1 位作者 李峰 段雪 《Tsinghua Science and Technology》 SCIE EI CAS 2004年第6期672-675,共4页
Investigation of selectivity of crystal growth direction in layered double hydroxides is helpful to control their particle sizes in different directions. Mg-AI layered double hydroxides (LDHs) were synthesized using a... Investigation of selectivity of crystal growth direction in layered double hydroxides is helpful to control their particle sizes in different directions. Mg-AI layered double hydroxides (LDHs) were synthesized using a coprecipitation method. The influences of aging temperature, aging time, and Mg/AI molar ratio on the crystal structure, the LDHs particle size, and the selectivity of crystal growth in different directions were investigated. The results show that the size of the crystallites in the a direction is larger than that in the c direction for all experimental conditions, indicating faster crystal growth in the a direction than in the c direction. The crystallite sizes in the a and c directions both increase with decreasing Mg/AI molar ratio but with less difference between the sizes in the two directions. Therefore, the crystal growth rate in the c direction increases more than that in the a direction as the Mg/AI molar ratio decreases. The influence of the aging time, aging temperature, and Mg/AI molar ratio on the selectivity of the crystal growth direction can be used to prepare LDHs with selected sizes in the a and c directions. 展开更多
关键词 layered double hydroxides selectivity of crystal growth direction particle size
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Ultrasonic generation via direct interaction between photons and phonons in anharmonic lattice of ionic crystals
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作者 OU Fa (Department of Applied Physics, South China University of Technology Guangzhou 510641) WU Fugen HE Minggao (Physics Department, Guangdong University of Technology Guangzhou 510090) LIU Cuihong (Physics Department, Guangzhou Teachers’College Guangzh 《Chinese Journal of Acoustics》 2000年第2期182-191,共10页
A theory of ultrasonic generation via direct interaction of transverse optic (TO) phonons with photons in anharmonic lattice of ionic crystals is presented. There are two methods of supplying light energy for the exci... A theory of ultrasonic generation via direct interaction of transverse optic (TO) phonons with photons in anharmonic lattice of ionic crystals is presented. There are two methods of supplying light energy for the excitation of TO lattice wave as a high frequency ultrasound: (A) incident light comes from the source outside the cavity? fulfilled with ionic crystal medium, (B) photon mode of the cavity possesses the gain of amplification by stimulated radiation of active atoms doping in the medium. More attention is drawn to the case (B). The working system of case (B), as a mixture of lasing action and ultrasonic generation, has the threshold phenomena like usual laser. And the linear stability analysis shows that the nonlineax phonon-photon coupling and the interaction among phonons themselves, both of which reflect the anharmonicity of lattice vibration, are necessary to the stable ultrasonic output. So this laser-ultrasonic generation mixture would be also a measure to investigate the lattice-dynamic nonlinearity and correlated electromagnetic properties of ionic crystals. 展开更多
关键词 Ultrasonic generation via direct interaction between photons and phonons in anharmonic lattice of ionic crystals mode
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Tunable high-Q SAW resonator loaded on a changing capacitance
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作者 G.Ya.Karapetyan V.E.Kaydashev +4 位作者 M.E.Kutepov T.A.Minasyan V.A.Kalinin V.O.Kislitsyn E.M.Kaidashev 《Journal of Advanced Dielectrics》 CAS 2020年第1期55-60,共6页
A tunable high-Q surface acoustic wave(SAW)resonator in the form of several parallel-connected interdigital transducers loaded on a varying capacitance on lithium niobate substrates was developed and studied.The worki... A tunable high-Q surface acoustic wave(SAW)resonator in the form of several parallel-connected interdigital transducers loaded on a varying capacitance on lithium niobate substrates was developed and studied.The working frequency range was 90-2450 MHz.A method of calculating such resonators,considering losses in the metal film as well as losses due to the propagation of SAWs and transformations into bulk waves is proposed.Such a design allows one to obtain a quality factor over 5000 in the frequency range 2400-2483 MHz.The resonant frequency shifts by 600 kHz when the capacitance changes by±25%of the value of 21 pF(or 32 ppm/pF)and has an almost linear character. 展开更多
关键词 Crystal growth directional crystallization defects internal stresses analytical methods
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