Sample records for solidification technology rst

  1. Application of RST in the steel industry

    Raman, R. V.; Maringer, R. E.


    The rapid solidification technology (RST) involves quenching molten metals at rates of perhaps 102 to 1010 degrees C per second. First reported in 1960, RST has experienced rapid growth during the last decade and is now established on the commercial market-place. This has resulted from the simple facts that unusual properties result from RST, that relatively easy techniques are available to produce large quantities of material, and that applications for these materials have been recognized. Ferrous-base materials produced by RST methods include staple fibers of mild and stainless steel for incorporation into concrete and castable refractories, powder metallurgy tool steels, and amorphous strip for power transformers. Research results suggest that RST will have a strong continuing influence on ferrous powder metallurgy, on the direct casting of strip and foil of carbon and stainless steel, and on core materials for motor and transformers.

  2. Optical oxygen sensing systems for drug discovery applications: Respirometric Screening Technology (RST)

    Papkovsky, Dmitri B.; Hynes, James; Fernandes, Richard


    Quenched-fluorescence oxygen sensing allows non-chemical, reversible, real-time monitoring of molecular oxygen and rates of oxygen consumption in biological samples. Using this approach we have developed Respirometric Screening Technology (RST); a platform which facilitates the convenient analysis of cellular oxygen uptake. This in turn allows the investigation of compounds and processes which affect respiratory activity. The RST platform employs soluble phosphorescent oxygen-sensitive probes, which may be assessed in standard microtitter plates on a fluorescence plate reader. New formats of RST assays and time-resolved fluorescence detection instrumentation developed by Luxcel provide improvements in assay sensitivity, miniaturization and overall performance. RST has a diverse range of applications in drug discovery area including high throughput analysis of mitochondrial function; studies of mechanisms of toxicity and apoptosis; cell and animal based screening of compound libraries and environmental samples; and, sterility testing. RST has been successfully validated with a range of practical targets and adopted by several leading pharmaceutical companies.

  3. Proceedings of the 2010 international solidification-stabilization technology forum

    Lake, C.B. [Dalhousie Univ., Halifax, NS (Canada). Dept. of Civil and Resource Engineering; Hills, C.D. [Greenwich Univ. (United Kingdom). Centre for Contaminated Land Remediation] (eds.)


    Solidification/stabilization (S/S) is remediation technology used to manage the risk associated with contaminated soils, wastes, and brownfield sites. Canada is now facing considerable challenges in ensuring that sites impacted by hydrocarbon contaminants are efficiently and effectively remediated. This forum was held to bring together leading researchers and practitioners in S/S remediation technology. Recent advances in research were presented, as well as new developments in the implementation of S/S technologies in the field, and methods of safely stabilizing and using potentially hazardous waste products. The conference was divided into the following 8 sessions: (1) stabilization/solidification of organics, (2) stabilization/solidification case studies, (3) stabilization/solidification of metals, (4) performance assessment, (5) mining applications, (6) new stabilization/solidification applications and approaches, (7) marine/coastal applications, and (8) stabilization/solidification amendments or alternatives. The forum featured 28 presentations, of which 6 have been catalogued separately for inclusion in this database. refs., figs.

  4. [Application of solidification technology in ecological protection of rural riverbank].

    Fu, Rong-bing; Chen, Xiao-hua; Luo, Qi-shi; Zhang, Shu-jiu; Li, Xiao-ping; Geng, Chun-nü


    A self-developed binder was used for the solidification of construction refuse piles and whole soil matrix, and a technology of this solidification combining with grass-planting was adopted to ecologically protect the rural riverbanks at Tianshan Village of Shanghai. This technology and other ecological engineering techniques were also employed to reconstruct the ecological environment of a sewage pond at the Village. The results showed that the solidified piles had an anti-compression strength of up to 7.3 MPa, with good hydraulic permeability, fast hardening rate, and low drying shrinkage, which met the requirements for ecological safety. The solidified stakes could be used at a low temperature of above -18 degrees C with addition of certain anti-freezing agents. The riverbank underpinned with the solidified stakes had higher anti-compressive strength, higher ability of anti-soil erosion, and better hydraulic permeability; and its soil had the similar moisture content to bare riverbank soil, with no detrimental effects on the root growth of planted grass. After soil solidification, the shearing strength of the riverbank increased by 50 times, and its soil loss was only 5% of the bare riverbank. In the first 10 days after adopting this technology, parts of Cynodon dactylon roots on the surface of solidified soil matrix began to extend into soil; after one month, 60% of the roots penetrated into deeper soil layer; and 11 months later, the grass roots completely grew in-depth in the soil. The combination of our solidification technique with vegetation reconstruction satisfied the requirements of both stabilizing riverbank and improving riparian habitat.


    This Technolgy Evaluation Report evaluates the solidification/stabilization process of Silicate Technology Corporation (STC) for the on-site treatment of contaminated soil The STC immobilization technology uses a proprietary product (FMS Silicate) to chemically stabilize and ...

  6. Discussion on "proportional solidification technology" for nodular iron casting method

    ZHOU Gen


    The Proportional Solidification Technology believes that advancing the expansion of graphite precipitation is favorable for fully utilizing the expansion to offset the contraction and minimizing feeder size. But this author has proved that advancing the expansion is unfavorable for both feeding from the feeder and the self-feeding by expansion. On contrary, advancing the contraction is favorable for both kinds of feeding and favorable for avoiding shrinkage. The feeding efficiency of feeders cannot be increased by advancing the expansion of the casting, but can only be increased by accelerating cooling and contraction of the casting, and (or) by delaying the freezing of the feeders. In order to fully utilize the expansion to offset the contraction, it is a must to ensure that all inlets and outlets of a casting being poured are blocked rapidly at the moment when pouring is finished. It is pointed out that blocking at the earlier frozen feeder neck is unfavorable for both feeding from the feeder and the self-feeding by expansion; whereas blocking at earlier frozen ingates is favorable for both kinds of feeding.


    This paper presents an EPA evaluation of the first field demonstration of an in situ stabilization/solidification process for contaminated soil under the EPA Superfund Innovative Technology Evaluation (SITE) program. Demonstration of this process was a joint effort of two vendors...

  8. Application of Layer-by-Layer Solidification Principle to Optimization of Large Chain Wheel Foundry Technology

    李日; 毛协民; 柳百成; 李文珍


    In order to get a sound casting of the alloy with a solidification range, the principle of directional solidification (DS) and the layer-by-layer solidification(LBLS) should be followed, especially in designing foundry process of steel cas/dng. Using the principles, the reasons for the forming of the defects on the surface of the chain wheels teeth and groove and the forming of MT (magneldc particle testing) thin lines were analyzed. The results of the metallographic observation and the numerical simulation show that the low temperature gradient results in a wider mushy zone at the S/L interface that causes the defects and MT thin lines on the surface of the chain wheel casting. Bvsed on the anslysis, a new casUng technology of the chain wheel was designed and used in the casting production successfully.

  9. Advanced powder metallurgy aluminum alloys via rapid solidification technology

    Ray, R.


    Aluminum alloys containing 10 to 11.5 wt. pct. of iron and 1.5 to 3 wt. pct. of chromium using the technique of rapid solidification powder metallurgy were studied. Alloys were prepared as thin ribbons (.002 inch thick) rapidly solidified at uniform rate of 10(6) C/second by the melt spinning process. The melt spun ribbons were pulverized into powders (-60 to 400 mesh) by a rotating hammer mill. The powders were consolidated by hot extrusion at a high reduction ratio of 50:1. The powder extrusion temperature was varied to determine the range of desirable processing conditions necessary to yield useful properties. Powders and consolidated alloys were characterized by SEM and optical metallography. The consolidated alloys were evaluated for (1) thermal stability, (2) tensile properties in the range, room temperature to 450 F, and (3) notch toughness in the range, room temperature to 450 F.

  10. [Recent advance in solidification/stabilization technology for the remediation of heavy metals-contaminated soil].

    Hao, Han-zhou; Chen, Tong-bin; Jin, Meng-gui; Lei, Mei; Liu, Cheng-wu; Zu, Wen-pu; Huang, Li-mi


    Remediation of heavy metals-contaminated soil is still a difficulty and a hotspot of international research projects. At present, the technologies commonly adopted for the remediation of contaminated sites mainly include excavation, solidification/stabilization (S/S), soil washing, soil vapor extraction (SVE), thermal treatment, and bioremediation. Based on the S/S technical guidelines of Unite State Environmental Protection Agency (EPA) and United Kingdom Environment Agency (EA) and the domestic and foreign patents, this paper introduced the concepts of S/S and its development status at home and abroad, and discussed its future development directions. Solidification refers to a process that binds contaminated media with a reagent, changing the media's physical properties via increasing its compressive strength, decreasing its permeability, and encapsulating the contaminants to form a solid material. Stabilization refers to the process that involves a chemical reaction which reduces the leachability of a waste, chemically immobilizes the waste and reduces its solubility, making the waste become less harmful or less mobile. S/S technology includes cement solidification, lime pozzolanic solidification, plastic materials stabilization, vitrification, and regent-based stabilization. Stabilization (or immobilization) treatment processes convert contaminants to less mobile forms through chemical or thermal interactions. In stabilization technology, the aim of adding agents is to change the soil physical and chemical properties through pH control technology, redox potential technology, precipitation techniques, adsorption technology, and ion-exchange technology that change the existing forms of heavy metals in soil, and thus, reduce the heavy metals bioavailability and mobility. This review also discussed the S/S evaluation methods, highlighted the need to enhance S/S technology in the molecular bonding, soil polymers, and formulation of China's S/S technical guidelines.

  11. Solidification microstructure of M2 high speed steel by different casting technologies

    Zhou Xuefeng; Fang Feng; Jiang Jianjing


    The present work investigated the solidification microstructure of AISI M2 high speed steel manufactured by different casting technologies, namely iron mould casting and continuous casting. The results revealed that the as-cast structure of the steel was composed of the iron matrix and the M2C eutectic carbide networks, which were greatly refined in the ingot made by continuous casting process, compared with that by the iron mould casting process. M2C eutectic carbides presented variation in ...

  12. Immobilization of antimony waste slag by applying geopolymerization and stabilization/solidification technologies.

    Salihoglu, Güray


    During the processing of antimony ore by pyrometallurgical methods, a considerable amount of slag is formed. This antimony waste slag is listed by the European Union as absolutely hazardous waste with a European Waste Catalogue code of 10 08 08. Since the levels of antimony and arsenic in the leachate of the antimony waste slag are generally higher than the landfilling limits, it is necessary to treat the slag before landfilling. In this study, stabilization/solidification and geopolymerization technologies were both applied in order to limit the leaching potential of antimony and arsenic. Different combinations ofpastes by using Portland cement, fly ash, clay, gypsum, and blast furnace slag were prepared as stabilization/solidification or geopoljymer matrixes. Sodium silicate-sodium hydroxide solution and sodium hydroxide solution at 8 M were used as activators for geopolymer samples. Efficiencies of the combinations were evaluated in terms of leaching and unconfined compressive strength. None of the geopolymer samples prepared with the activators yielded arsenic and antimony leaching below the regulatory limit at the same time, although they yielded high unconfined compressive strength levels. On the other hand, the stabilization/solidification samples prepared by using water showed low leaching results meeting the landfilling criteria. Use of gypsum as an additive was found to be successful in immobilizing the arsenic and antimony.


    E. I. Marukovich


    Full Text Available The new method of continuously iterative casting of hollow cylindrical castings from cast iron without application of core, based on the principle of direction of metal solidification is presented in the work. the thermal condition of crystallizer at iterative temperature influences on its internal surface and solidification of casting in the conditions of intensive one-way heat sink and presence of constant overheat on front of solidification is examined.

  14. Video Watermarking Using RST Resilient Technique

    Ramya. C


    Full Text Available Watermarking is a process of staganography or embedding process. It is mainly proposed for copy right protection, data security, data hiding, convey other information etc. In this paper, watermarking process is achieved by RST resilient technique. The advantage of this technique is providing a data security. RST resilient technique can avoid a data loss, due to disorder caused by Rotation, Scaling and Translation (RST attack. Embedding data to the video frames is achieved by two steps. At first step, by using RST technique data or message is watermarked to an image. At second step, data embedded image is watermarked to a selective frames in the video sequence. This process can be done in both spatial domain and frequency domain.

  15. Solidification microstructure of M2 high speed steel by different casting technologies

    Zhou Xuefeng


    Full Text Available The present work investigated the solidification microstructure of AISI M2 high speed steel manufactured by different casting technologies, namely iron mould casting and continuous casting. The results revealed that the as-cast structure of the steel was composed of the iron matrix and the M2C eutectic carbide networks, which were greatly refined in the ingot made by continuous casting process, compared with that by the iron mould casting process. M2C eutectic carbides presented variation in their morphologies and growth characteristics in the ingots by both casting methods. In the ingot by iron mould casting, they have a plate-like morphology and grow anisotropically. However, in the ingot made by continuous casting, the carbides evolved into the fiber-like shape that exhibited little characteristics of anisotropic growth. It was noticed that the fiber-like M2C was much easier to decompose and spheroidize after heated, as a result, the carbides refined remarkably, compared with the case of plate-like carbides in the iron mould casting ingot.

  16. Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2

    Ray, Ranjan; Jha, Sunil C.


    Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.

  17. Effect of Oxide Level on Pore Formation in A356 Alloy by X-Ray Imaging and Directional Solidification Technology

    Liao, Hengcheng; Song, Wan; Wang, Qigui; Zhao, Lei; Fan, Ran

    Effect of oxide level on porosity formation in an A356 alloy was investigated using micro-focus X-ray imaging and directional solidification technology. The increase of oxide level in liquid aluminum was achieved by violently stirring molten metal at elevated temperature. During solidification, the increased oxide content in melt significantly increases the amount of active nucleation sites for porosity and thus raises the nucleation temperature of pores. The fast growth of those early formed pores further restrains the succeeding nucleation operations of new pores in local regions and results in a considerable reduction in pore density. It was also found that the melt with high oxide content shows less dependency of growth rate reduction with local temperature.

  18. Advances in Solidification Processing

    Hugo F. Lopez


    Full Text Available Melt solidification is the shortest and most viable route to obtain components, starting from the design to the finished products. Hence, a sound knowledge of the solidification of metallic materials is essential for the development of advanced structural metallic components that drive modern technological societies. As a result, there have been innumerable efforts and full conferences dedicated to this important subject [1–6]. In addition, there are various scientific journals fully devoted to investigating the various aspects which give rise to various solidification microstructures [7–9]. [...

  19. Low-gravity solidification of cast iron and space technology applications

    Graham, J. A.


    Two types of analyses relating to cast iron solidification were conducted. A theoretical analysis using a computer to predict the cooling versus time relationship throughout the test specimen was performed. Tests were also conducted in a ground-based laboratory to generate a cooling time curve for cast iron. In addition, cast iron was cooled through the solidification period on a KC-135 and an F-104 aircraft while these aircraft were going through a period of low gravity. Future subjects for low gravity tests are enumerated.

  20. Topics about steel technologies. 2. ; Semi-solidification process. Tekko gijutsu topics. 2. ; Hangyoko kako process

    Kawakami, M.


    This paper describes features, the current status and examples of studies on the metal semi-solidification process. This process provides fine and uniform grain structures without coarse dendrite, internal defects, and segregation. The process uses a low processing pressure that makes uniform processing easier, and can make new composite materials and alloys with new components because of high viscosity in slurry. The thixomolding that combines a semi-melting process with the semi-solidification process is expected of the early realization of its use because it is easier in controlling metal crystal shapes, processing temperatures, and viscosity during processing than in the rheocasting. Research and development efforts in other countries are addressed to developing cryogenic casting processes for mass-produced steel materials aimed at reducing segregation, and studying a process to supply semi-solidified metal slurries to different manufacturing processes to fabricate difficult-to-process materials and functional materials into a near net shape. Studies include identification of relationship between cooling rates and stirring rates affecting crystal shapes, understanding of formability and transformation behavior of semi-solidified metals, and introduction of viscosity inferring equations. 3 figs., 1 tab.

  1. Black hole mining in the RST model

    Basavaraju, Rohitvarma


    We consider the possibility of mining black holes in the 1+1-dimensional dilaton gravity model of Russo, Susskind and Thorlacius. The model correctly incorporates Hawking radiation and back-reaction in a semiclassical expansion in 1/N, where N is the number of matter species. It is shown that the lifetime of a perturbed black hole is independent of the addition of any extra apparatus when realized by an arbitrary positive energy matter source. We conclude that mining does not occur in the RST model and comment on the implications of this for the black hole information paradox.

  2. Continuous and directional solidification technology of titanium alloys with cold crucible

    CHEN Rui-run; DING Hong-sheng; GUO Jing-jie; BI Wei-sheng; FU Heng-zhi


    The experiments of continuous and directional solidification of titanium alloys with cold crucible were carried out in a multifunctional electromagnetic cold crucible apparatus. Parameters and factors influencing the surface crack and macrostructure of titanium alloy ingots were studied. The mechanism of the parameters and factors influencing the surface crack and macrostructure of the ingots were interpreted. The results show that the surface cracks of the prepared ingots decrease with the increase of the input power from 50 to 60 kW or with the increase of the coil turns from 3 to 5 circles. The surface cracks increase with the increase of withdrawal velocity from 3 to 5 mm/min or the height of the primer from 2 to 3 cm, then decrease with the increase of withdrawal velocity from 5 to 8.7 mm/min or the height of the primer from 3 to 4 cm. Coil turns is the most important one in all parameters effect on the surface crack, the input power is more important, then the withdrawal velocity is important and the height of the primer is the least important. Withdrawal velocity is the most important factor affecting the macrostructure, and effects of other factors on macrostructure is slight. With the decrease of velocity from 8.7 to 0.5 mm/min, the quantity of grains reduces, the grain orientation degree becomes small, and the solidification fronts change from concave to plane to convex. The ingot can be directional solidified at velocity of 1 mm/min. The ingot with free surface crack and directional macrostructure is prepared under definite conditions.

  3. A microencapsulation process of liquid mercury by sulfur polymer stabilization/solidification technology. Part II: Durability of materials

    Lopez-Delgado, A.; Guerrero, A.; Lopez, F. A.; Perez, C.; Alguacil, F. J.


    Under the European LIFE Program a microencapsulation process was developed for liquid mercury using Sulfur Polymer Stabilization/Solidification (SPSS) technology, obtaining a stable concrete-like sulfur matrix that allows the immobilization of mercury for long-term storage. The process description and characterization of the materials obtained were detailed in Part I. The present document, Part II, reports the results of different tests carried out to determine the durability of Hg-S concrete samples with very high mercury content (up to 30 % w/w). Different UNE and RILEM standard test methods were applied, such as capillary water absorption, low pressure water permeability, alkali/acid resistance, salt mist aging, freeze-thaw resistance and fire performance. The samples exhibited no capillarity and their resistance in both alkaline and acid media was very high. They also showed good resistance to very aggressive environments such as spray salt mist, freeze-thaw and dry-wet. The fire hazard of samples at low heat output was negligible. (Author)

  4. A microencapsulation process of liquid mercury by sulfur polymer stabilization/solidification technology. Part II: Durability of materials

    López-Delgado, A.


    Full Text Available Under the European LIFE Program a microencapsulation process was developed for liquid mercury using Sulfur Polymer Stabilization/Solidification (SPSS technology, obtaining a stable concrete-like sulfur matrix that allows the immobilization of mercury for long-term storage. The process description and characterization of the materials obtained were detailed in Part I. The present document, Part II, reports the results of different tests carried out to determine the durability of Hg-S concrete samples with very high mercury content (up to 30 % w/w. Different UNE and RILEM standard test methods were applied, such as capillary water absorption, low pressure water permeability, alkali/acid resistance, salt mist aging, freeze-thaw resistance and fire performance. The samples exhibited no capillarity and their resistance in both alkaline and acid media was very high. They also showed good resistance to very aggressive environments such as spray salt mist, freeze-thaw and dry-wet. The fire hazard of samples at low heat output was negligible.

    Dentro del Programa Europeo LIFE, se ha desarrollado un proceso de microencapsulación de mercurio liquido, utilizando la tecnología de estabilización/solidificación con azufre polimérico (SPSS. Como resultado se ha obtenido un material estable tipo concreto que permite la inmovilización de mercurio y su almacenamiento a largo plazo. La descripción del proceso y la caracterización de los materiales obtenidos, denominados concretos Hg-S, se detallan en la Parte I. El presente trabajo, Parte II, incluye los resultados de los diferentes ensayos realizados para determinar la durabilidad de las muestras de concreto Hg-S con un contenido de mercurio de hasta el 30 %. Se han utilizado diferentes métodos de ensayo estándar, UNE y RILEM, para determinar propiedades como la absorción de agua por capilaridad, la permeabilidad de agua a baja presión, la resistencia a álcali y ácido, el comportamiento en

  5. Research on extended AHP method with the aid of RST

    NII Ming


    Analytic Hierarchy Process (AHP) method can be used to solve the tasks of multi-criterion decision system fields, but some complicated questions processed by AHP cannot be easily solved by means of the gener-al method. It is because of being unsatisfied with consistency condition or judgment matrix too intricate to solve, which causes AHP invalidation. So in order to resolve this problem, AHP knowledge systems reduced with the aid of Genetic Algorithms (GA) were proposed, which directly acquired the order of AHP issue through the rule of Rough Sets Theory (RST) method, or solved the tasks reduced by RST with classical AHP method. On this condition, the compare decision system of region informatization level was solved, and the results solved were the same to those by classical AHP, which denoted that this method was more simple and reliable, besides the four rules of changing AHP system into RST Decision System.

  6. Research progress on solidification technologies for dredging sediment of river & lake%河湖疏浚底泥的固化处置技术研究进展

    彭旭更; 胡保安


    通过固化处理将河湖疏浚底泥转化为固化土是目前一种有效的资源化利用途径.文章在总结分析国内外疏浚底泥固化技术的基础上,系统地介绍了物化反应、水分转化和骨架构建3种固化过程机理,并对影响固化土力学性质的影响因素进行了讨论分析,主要包括有机质含量、固化材料掺加量、含水量、养护龄期与粘粒含量,同时介绍了目前固化工艺的工程实践,分析了面临的问题,得出了工程经验.通过对研究成果的总结,探讨了河湖疏浚底泥固化工艺的发展趋势.%Through solidification process,the transformation from sediment to the solidified soil was one of the available recycling treatment.The sediment solidification technologies for dredging sediment were summarized and analyzed in this paper,and the three kinds of process mechanism were presented,including physical and chemical reaction model,water transformation model and skeleton construction model.Several important influence parameters for solidification were discussed,which included organic matter content,mixing amount of solidification material,water content,curing age and clay content.Engineering application and experiences of solidification technologies were also introduced and obtained in this paper.Through summarizing the research findings, the development tendency of solidification technologies were discussed in the end.

  7. Application of Layer-by-Layer Solidification Principle to Optimization of Large Chain Wheel Foundry Technology%逐层凝固原则在大链轮铸造工艺优化中的应用

    李日; 毛协民; 柳百成; 李文珍


    In order to get a sound casting of the alloy with a solidification range, the principle of directional solidification (DS) and the layer-by-layer solidification(LBLS) should be followed, especially in designing foundry process of steel casting. Using the principles, the reasons for the forming of the defects on the surface of the chain wheels teeth and groove and the forming of MT (magnetic particle testing) thin lines were analyzed. The results of the metallographic observation and the numerical simulation show that the low temperature gradient results in a wider mushy zone at the S/L interface that causes the defects and MT thin lines on the surface of the chain wheel casting. Based on the analysis, a new casting technology of the chain wheel was designed and used in the casting production successfully.

  8. Structural dynamics of the two-component response regulator RstA in recognition of promoter DNA element

    Li, Yi-Chuan; Chang, Chung-ke; Chang, Chi-Fon; Cheng, Ya-Hsin; Fang, Pei-Ju; Yu, Tsunai; Chen, Sheng-Chia; Li, Yi-Ching; Hsiao, Chwan-Deng; Huang, Tai-huang


    The RstA/RstB system is a bacterial two-component regulatory system consisting of the membrane sensor, RstB and its cognate response regulator (RR) RstA. The RstA of Klebsiella pneumoniae (kpRstA) consists of an N-terminal receiver domain (RD, residues 1–119) and a C-terminal DNA-binding domain (DBD, residues 130–236). Phosphorylation of kpRstA induces dimerization, which allows two kpRstA DBDs to bind to a tandem repeat, called the RstA box, and regulate the expression of downstream genes. Here we report the solution and crystal structures of the free kpRstA RD, DBD and DBD/RstA box DNA complex. The structure of the kpRstA DBD/RstA box complex suggests that the two protomers interact with the RstA box in an asymmetric fashion. Equilibrium binding studies further reveal that the two protomers within the kpRstA dimer bind to the RstA box in a sequential manner. Taken together, our results suggest a binding model where dimerization of the kpRstA RDs provides the platform to allow the first kpRstA DBD protomer to anchor protein–DNA interaction, whereas the second protomer plays a key role in ensuring correct recognition of the RstA box. PMID:24990372

  9. Image adaptive RST invariant watermark using pseudo-Zernike moments

    Leida LI; Baolong GUO


    Rotation, scaling and translation (RST) attacks can desynchronize watermark detection, which causes failure in many watermarking systems. In this paper, an image adaptive RST invariant watermark (AWPZM) is proposed by using the rotation invariant property of pseudo-Zernike moments (PZM) and odd-even quantization. PZM of the original image is computed first, and then those suitable for watermark generation are selected. Then, magnitudes of them are odd-even quantized to generate the watermark. In detection, a normalized hamming function is employed to determine the similarity of the watermark. Experimental results show its robustness to rotation and scaling. For traditional attacks, such as JPEG compression, added noise and filtering, the similarities are all above 0.95.

  10. Solidification under microgravity

    B K Dhindaw


    The paper outlines the broad areas where studies are being conducted under microgravity conditions worldwide viz., biotechnology, combustion science, materials science and fluid physics. The paper presents in particular a review on the various areas of research being pursued in materials science. These include studies on immiscibles, eutectics, morphology development during solidification or pattern formation, nucleation phenomena, isothermal dendrite growth, macrosegregation and the behaviour of insoluble particles ahead of the solidifying interface. The latter studies are given in detail with description of case studies of experiments conducted by the author on space shuttles. In particular, the technology and the science issues are addressed. Lastly, based on the presentations, some salient features enumerating the advantages of conducting experiments under conditions of microgravity are highlighted in terms of science returns.

  11. Directional Solidification of Ledeburite

    M. Trepczyńska-Łent


    Full Text Available Directional solidification of ledeburite was realised out using a Bridgman’s device. The growth rate for movement sample v=83.3 μm/s was used. In one sample the solidification front was freezing. The value of temperature gradient in liquid at the solidification front was determined. Interfacial distance λ on the samples was measured with NIS-Elements application for image analysis.

  12. Fundamental Metallurgy of Solidification

    Tiedje, Niels


    The text takes the reader through some fundamental aspects of solidification, with focus on understanding the basic physics that govern solidification in casting and welding. It is described how the first solid is formed and which factors affect nucleation. It is described how crystals grow from ...

  13. Back analysis based on SOM-RST system

    Owladeghaffari, H


    This paper describes application of information granulation theory, on the back analysis of Jeffrey mine southeast wall Quebec. In this manner, using a combining of Self Organizing Map (SOM) and rough set theory (RST), crisp and rough granules are obtained. Balancing of crisp granules and sub rough granules is rendered in close-open iteration. Combining of hard and soft computing, namely finite difference method (FDM) and computational intelligence and taking in to account missing information are two main benefits of the proposed method. As a practical example, reverse analysis on the failure of the southeast wall Jeffrey mine is accomplished.

  14. Parabolic aircraft solidification experiments

    Workman, Gary L. (Principal Investigator); Smith, Guy A.; OBrien, Susan


    A number of solidification experiments have been utilized throughout the Materials Processing in Space Program to provide an experimental environment which minimizes variables in solidification experiments. Two techniques of interest are directional solidification and isothermal casting. Because of the wide-spread use of these experimental techniques in space-based research, several MSAD experiments have been manifested for space flight. In addition to the microstructural analysis for interpretation of the experimental results from previous work with parabolic flights, it has become apparent that a better understanding of the phenomena occurring during solidification can be better understood if direct visualization of the solidification interface were possible. Our university has performed in several experimental studies such as this in recent years. The most recent was in visualizing the effect of convective flow phenomena on the KC-135 and prior to that were several successive contracts to perform directional solidification and isothermal casting experiments on the KC-135. Included in this work was the modification and utilization of the Convective Flow Analyzer (CFA), the Aircraft Isothermal Casting Furnace (ICF), and the Three-Zone Directional Solidification Furnace. These studies have contributed heavily to the mission of the Microgravity Science and Applications' Materials Science Program.

  15. Preliminary Reports, Memoranda and Technical Notes of the Materials Research Council Summer Conference, La Jolla, California. Volume 1. Rapid Solidification Technology


    specimen size and geometry requirements. He gave examples of dendritic and micro- crystalline structures found in atomized nickel alloy powders. He also...mination of exact cooling rates during solidification of crystalline and non- crystalline structures in these processes have required estimates the liquid during rapid solidification for the formation of non- crystalline structures 8-1 0 . Heat flow calcula- tions are usually combined with

  16. Modelling directional solidification

    Wilcox, William R.; Regel, Liya L.


    This grant, NAG8-831, was a continuation of a previous grant, NAG8-541. The long range goal of this program has been to develop an improved understanding of phenomena of importance to directional solidification, in order to enable explanation and prediction of differences in behavior between solidification on Earth and in space. Emphasis in the recently completed grant was on determining the influence of perturbations on directional solidification of InSb and InSb-GaSb alloys. In particular, the objective was to determine the influence of spin-up/spin-down (ACRT), electric current pulses and vibrations on compositional homogeneity and grain size.

  17. Solidification microstructure development

    G Phanikumar; K Chattopadhyay


    In the present article, evolution of microstructure during solidification, as a function of various parameters, is discussed. Macrosegregation is described as being due to insufficient diffusivity of solute in the solid. Pattern formation is discussed in the light of instabilities at the solidification growth front. An overview of the scaling relations for various microstructures is given. Metastable extensions to equilibrium phase diagrams and corrections to equilibrium quantities are described.

  18. Solidification and casting

    Cantor, Brian


    INDUSTRIAL PERSPECTIVEDirect chillcasting of aluminium alloysContinuous casting of aluminium alloysContinuous casting of steelsCastings in the automotive industryCast aluminium-silicon piston alloysMODELLING AND SIMULATIONModelling direct chill castingMold filling simulation of die castingThe ten casting rulesGrain selection in single crystal superalloy castingsDefects in aluminium shape castingPattern formation during solidificationPeritectic solidificationSTRUCTURE AND DEFECTSHetergeneous nucleation in aluminium alloysCo

  19. Directional Solidification of Eutectic Ceramics

    Sayir, Ali


    Two major problems associated with structural ceramics are lack of damage tolerance and insufficient strength and creep resistance at very high temperatures of interest for aerospace application. This work demonstrated that the directionally solidified eutectics can have unique poly-phase microstructures and mechanical properties superior to either constituent alone. The constraining effect of unique eutectic microstructures result in higher resistance to slow crack growth and creep. Prospect of achieving superior properties through controlled solidification are presented and this technology can also be beneficial to produce new class of materials.

  20. Travelling wave solutions to nonlinear physical models by means of the first integral method

    İsmail Aslan Aslan


    This paper presents the first integral method to carry out the integration of nonlinear partial differential equations in terms of travelling wave solutions. For illustration, three important equations of mathematical physics are analytically investigated. Through the established first integrals, exact solutions are successfully constructed for the equations considered.

  1. Progress of Solidification Researches and the Applications in Materials Processing


    The research achievements of solidification theories and technologies in the last decades are reviewed with the stresses on some new development in the recent years. Some new interesting areas emerged in the last years are also pointed out.

  2. Onihomikozes diagnostika un ārstēšana

    Grečaņuka, Viktorija


    Onihomikozes paaugstinātas izplatīšanās dēļ ir nepieciešams rūpēties par nagu veselību, jo nevērīgas attieksmes dēļ nagu sēnītes infekcija var augt un izplatīties uz veselajiem ādas rajoniem apkārt nagam, tāpēc ja ir aizdomas par nagu sēnīti ir savlaicīgi jāvēršās pie ārsta, lai viņš diagnosticētu sēnītes sugu un sāktu pareizo ārstēšanas kursu.Bakalura darba mērķis ir izpētīt inficētā naga paņemtos materiālus uz sēnīti un apstiprināt to laboratoriski, kā arī izanalizēt pretsēnīšu preparātu ap...

  3. Models of Rapid Solidification

    Gilmer, G. H.; Broughton, J. Q.


    Laser annealing studies provide much information on various consequences of rapid solidification, including the trapping of impurities in the crystal, the generation of vacancies and twins, and on the fundamental limits to the speed of the crystal-melt interface. Some results obtained by molecular dynamics methods of the solidification of a Lennard-Jones liquid are reviewed. An indication of the relationship of interface speed to undercooling for certain materials can be derived from this model. Ising model simulations of impurity trapping in silicon are compared with some of the laser annealing results. The consequences of interface segregation and atomic strain are discussed.

  4. Solidification modeling: Status and outlook

    Dantzig, J. A.


    Solidification modeling is a complex and highly advanced field. This article examines the state of the art in solidification modeling, including physical phenomena of solidification such as heat extraction, transport processes within a casting, and dimensional changes in the casting and mold during solidification. Also examined are current efforts to model these phenomena and the strengths and weaknesses of these efforts. Finally, obstacles to solidification modeling, such as speed and cost of the process, are considered, along with the likelihood those obstacles will be overcome.

  5. Late-onset-Hörstörungen bei CI-Kindern

    Nickisch, A.; Horn, U; Massinger, C


    Hintergrund: Nach jüngsten Mitteilungen des Deutschen Zentralregisters für kindliche Hörstörungen konnte durch das Neugeborenen-Hörscreening das mittlere Erfassungsalter permanenter frühkindlicher Hörstörungen erfreulicherweise in das erste Lebenshalbjahr verschoben werden. Wie hoch der Anteil von late-onset-Hörstörungen ist, ist derzeit jedoch unklar.Material und Methoden: Aus der Datei der von uns betreuten CI-Kinder wurden retrospektiv diejenigen ausgewählt, bei denen ein Neugeborenenhör...

  6. Application of treatment technology of drilling waste mud harmless and solidification%钻井废弃泥浆无害化和固化处理技术的应用

    王伟; 周岩


    Briefly introduced China's current harmless treatment of drilling waste mud,the impact on the environment,and now commonly used drilling waste mud harmless and solidification treatment technology.Through the examples to appraise the non-toxic and harmless of waste mud produced by drilling in exploration mine area,and did a bold attempt to treatment technology and process of harmless and solidification,wanted to share much experience with counterparts,to promote protection work of core drilling environment.%简要介绍我国目前钻井废弃泥浆无害化处理的现状,废弃泥浆对环境的影响,目前常用钻井废弃泥浆无害化固化处理技术。通过实例对勘探矿区内的钻孔产生的废弃泥浆进行无毒和无害化评价,并进行一次无害化和固化处理技术及工艺的大胆尝试,取得点滴体会供同行们分享,推动岩心钻探环境保护工作。

  7. Solidification of oils and organic liquids

    Clark, D.E.; Colombo, P.; Neilson, R.M. Jr.


    The suitability of selected solidification media for application in the disposal of low-level oil and other organic liquid wastes has been investigated. In the past, these low-level wastes (LLWs) have commonly been immobilized by sorption onto solid absorbents such as vermiculite or diatomaceous earth. Evolving regulations regarding the disposal of these materials encourage solidification. Solidification media which were studied include Portland type I cement; vermiculite plus Portland type I cement; Nuclear Technology Corporation's Nutek 380-cement process; emulsifier, Portland type I cement-sodium silicate; Delaware Custom Materiel's cement process; and the US Gypsum Company's Envirostone process. Waste forms have been evaluated as to their ability to reliably produce free standing monolithic solids which are homogeneous (macroscopically), contain < 1% free standing liquids by volume and pass a water immersion test. Solidified waste form specimens were also subjected to vibratory shock testing and flame testing. Simulated oil wastes can be solidified to acceptable solid specimens having volumetric waste loadings of less than 40 volume-%. However, simulated organic liquid wastes could not be solidified into acceptable waste forms above a volumetric loading factor of about 10 volume-% using the solidification agents studied.

  8. Borrelia burgdorferi RST1 (OspC type A) genotype is associated with greater inflammation and more severe Lyme disease.

    Strle, Klemen; Jones, Kathryn L; Drouin, Elise E; Li, Xin; Steere, Allen C


    Evidence is emerging for differential pathogenicity among Borrelia burgdorferi genotypes in the United States. By using two linked genotyping systems, ribosomal RNA intergenic spacer type (RST) and outer surface protein C (OspC), we studied the inflammatory potential of B. burgdorferi genotypes in cells and patients with erythema migrans or Lyme arthritis. When macrophages were stimulated with 10 isolates of each RST1, RST2, or RST3 strain, RST1 (OspC type A)-stimulated cells expressed significantly higher levels of IL-6, IL-8, chemokine ligand (CCL) 3, CCL4, tumor necrosis factor, and IL-1β, factors associated with innate immune responses. In peripheral blood mononuclear cells, RST1 strains again stimulated significantly higher levels of these mediators. Moreover, compared with RST2, RST1 isolates induced significantly more interferon (IFN)-α, IFN-γ, and CXCL10, which are needed for adaptive immune responses; however, OspC type I (RST3) approached RST1 (OspC type A) in stimulating these adaptive immune mediators. Similarly, serum samples from patients with erythema migrans who were infected with the RST1 genotype had significantly higher levels of almost all of these mediators, including exceptionally high levels of IFN-γ-inducible chemokines, CCL2, CXCL9, and CXCL10; and this pronounced inflammatory response was associated with more symptomatic infection. Differences among genotypes were not as great in patients with Lyme arthritis, but those infected with RST1 strains more often had antibiotic-refractory arthritis. Thus, the B. burgdorferi RST1 (OspC type A) genotype, followed by the RST3 (OspC type I) genotype, causes greater inflammation and more severe disease, establishing a link between spirochetal virulence and host inflammation.

  9. Enhanced salt tolerance of alfalfa (Medicago sativa) by rstB gene transformation.

    Zhang, Wan-Jun; Wang, Tao


    Generating salt tolerance forage plant is essential for use of the land affected by high salinity. A salt tolerance gene rstB was used as a selectable marker gene in Agrobacterium-mediated transformation of tobacco under a selective regime of 170mM NaCl. The transgenic plants showed clear improvement in salt tolerance. To improve salt tolerance of alfalfa (Medicago sativa L.), rstB gene was introduced into alfalfa genome by Agrobacterium-mediated transformation. No abnormal phenotype was observed among the transgenic plants when compared with wild type (wt) plants. Significant enhancement of resistance to salt-shock treatment was noted on the rstB transgenic (T0) plants. Transgenic second-generation (T1) seeds showed improved germination rate and seedling growth under salt-stress condition. Hindered Na(+) accumulation, but enhanced Ca(2+) accumulation was observed on the rstB T1 plants when subjected to salt-stresses. Enhanced calcium accumulation in transgenic plants was also verified by cytohistochemical localization of calcium. Under salt-stress of 50mM NaCl, about 15% of the transgenic plants finished their life-cycle but the wt plants had no flower formation. The results demonstrated that the expression of rstB gene improved salt tolerance in transgenic alfalfa. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  10. Auto-pickfi rst breaks with complex raypaths for undulate surface conditions

    An Sheng-Pei; Hu Tian-Yue; Cui Yong-Fu; Duan Wen-Sheng; Peng Geng-Xin


    First-break picking is the key step in seismic data processing for surveying undulate surfaces, and directly infl uences the precision of near-surface modeling and effects of static corrections. The currentfi rst-break auto-picking methods may fail when the signal-to-noise ratio (SNR) is low for seismic data in the undulate area, and require labor and time intensive manual picking. This study develops an improved super-virtual interferometry (SVI) method that combines multichannel and multidomain quality control (MMQC) techniques to achieve auto-pickedfi rst breaks. The improved SVI method extends the SVI application to enhance the SNR for near-surface scattered waves for thefi rst time, which allows for the SVI method to adapt tofi rst breaks with complex raypaths by linear combination of refractions and near-surface scattered waves. Methods of inverse and multidomain interferometry are developed to effectively enhance the virtual records extracted by the SVI method. The deconvolution filter for waveforms is used to increase resolution and reduce false picks, while the MMQC technique is designed to auto-correct false picks and increase the stability of auto-pickingfi rst breaks. The robust technique developed in this study enables stable processing of large 3D seismic datasets. Higher quality results are obtained using the approach presented in this paper to actualfi eld data from the mountain areas in western China, when compared to some commonly used commercial software.

  11. Solidification microstructures and solid-state parallels: Recent developments, future directions

    Asta, M. [Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, CA 95616 (United States); Beckermann, C. [Department of Mechanical and Industrial Engineering, University of Iowa, Iowa City, IA 52242 (United States); Karma, A. [Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA 02115 (United States); Kurz, W. [Institute of Materials, Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne (Switzerland)], E-mail:; Napolitano, R. [Department of Materials Science and Engineering, Iowa State University, and Ames Laboratory USDOE, Ames, IA 50011 (United States); Plapp, M. [Physique de la Matiere Condensee, Ecole Polytechnique, CNRS, 91128 Palaiseau (France); Purdy, G. [Department of Materials Science and Engineering, McMaster University, Hamilton, Ont., L8S 4L7 (Canada); Rappaz, M. [Institute of Materials, Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne (Switzerland); Trivedi, R. [Department of Materials Science and Engineering, Iowa State University, and Ames Laboratory USDOE, Ames, IA 50011 (United States)


    Rapid advances in atomistic and phase-field modeling techniques as well as new experiments have led to major progress in solidification science during the first years of this century. Here we review the most important findings in this technologically important area that impact our quantitative understanding of: (i) key anisotropic properties of the solid-liquid interface that govern solidification pattern evolution, including the solid-liquid interface free energy and the kinetic coefficient; (ii) dendritic solidification at small and large growth rates, with particular emphasis on orientation selection; (iii) regular and irregular eutectic and peritectic microstructures; (iv) effects of convection on microstructure formation; (v) solidification at a high volume fraction of solid and the related formation of pores and hot cracks; and (vi) solid-state transformations as far as they relate to solidification models and techniques. In light of this progress, critical issues that point to directions for future research in both solidification and solid-state transformations are identified.

  12. Possible Involvement of Nitric Oxide and Reactive Oxygen Species in Glucose Deprivation-Induced Activation of Transcription Factor Rst2

    Toshiaki Kato; Xin Zhou; Yan Ma


    Glucose is one of the most important sources of cellular nutrition and glucose deprivation induces various cellular responses. In Schizosaccharomyces pombe, zinc finger protein Rst2 is activated upon glucose deprivation, and regulates gene expression via the STREP (stress response element of Schizosaccharomyces pombe) motif. However, the activation mechanism of Rst2 is not fully understood. We monitored Rst2 transcriptional activity in living cells using a Renilla luciferase reporter system. ...

  13. 重金属污染土壤稳定/固化修复技术研究进展%Recent advance in solidification/stabilization technology for the remediation of heavy metals contaminated soil

    郝汉舟; 陈同斌; 靳孟贵; 雷梅; 刘成武; 祖文普; 黄莉敏


    Remediation of heavy metals-contaminated soil is still a difficulty and a hotspot of international research projects. At present. the technologies commonly adopted for the remediation of contaminated sites mainly include excavation. solidification/stabilization ( S/S) . soil washing, soil vapor extraction ( SVE) . thermal treatment. and bioremediation. Based on the S/S technical guidelines of Unite State Environmental Protection Agency ( EPA) and United Kingdom Environment Agency ( EA) and the domestic and foreign patents, this paper introduced the concepts of S/S and its development status at home and abroad, and discussed its future development directions. Solidification refers to a process that binds contaminated media with a reagent, changing the media' s physical properties via increasing its compressive strength, decreasing its permeability, and encapsulating the contaminants to form a solid material. Stabilization refers to the process that involves a chemical reaction which reduces the leachability of a waste. chemically immobilizes the waste and reduces its solubility, making the waste become less harmful or less mobile. S/S technology includes cement solidification, lime pozzolanic solidification, plastic materials stabilization. vitrification. and regent-based stabilization. Stabilization ( or immobilization) treatment processes convert contaminants to less mobile forms through chemical or thermal interactions. In stabilization technology, the aim of adding agents is to change the soil physical and chemical properties through pH control technology, redox potential technology, precipitation techniques, adsorption technology, and ion-exchange technology that change the existing forms of heavy metals in soil. and thus. reduce the heavy metals bioavailability and mobility. This review also discussed the S/S evaluation methods. highlighted the need to enhance S/S technology in the molecular bonding, soil polymers. and formulation of China ' s S/S technical

  14. Detailed Vertical and Lateral Delineation of Redox Zones in Contaminant Plumes Using Redox-Sensitive Tapes (RST)

    Blum, P.; Oeste, F. D.; Melzer, R.; Martus, P.


    Innovative redox-sensitive tapes (RST) have been developed for a detailed vertical and lateral delineation of redox zones in contaminated aquifers. The RST have the potential to become an integral part of a data acquisition strategy for monitored natural attenuation (MNA). The tape material, consists of a 2 cm wide synthetic textile coated with reactive manganese dioxide minerals. The RST are submerged into existing monitoring wells for approximately one month. This time period is sufficient to allow for a reaction of the mineral coating with groundwater. The RST are aimed at investigating four different redox-zones in contaminated aquifers: Mn(II)-oxidizing, Mn(IV)-reducing, Fe(III)-reducing and sulfate-reducing. Two RST case studies are presented. The RST investigations on a coal tar contaminated site allowed for a precise lateral and vertical delineation of the contaminant plume using the existing monitoring well network. The RST investigations on a BTEX contaminated site yielded a good correlation of RST data with hydrochemical data at the wells sampled. In the majority of plume wells located 50 m downstream of the source area and beyond, Mn(IV)-reducing environment appeared to be prevailing. Comparing the RST data with hydrochemical data indicated evidence for the transport of transformation products with groundwater flow. The repeated application of the RST facilitated an assessment of the plume dynamics. No significant seasonal variation with respect to the redox zone distribution was observed within the contaminant plume. However, the assessment of the changes in redox conditions over a time period of 2.5 years showed that the iron-reducing zone is shrinking and the sulfate-reducing zone disappeared completely indicating that the contaminant plume might decrease in the near future. Thus, the application of the RST facilitated an assessment of the plume dynamics on a centimeter-scale without the necessity of pumping and treating contaminated groundwater.

  15. Analytic treatment of nonlinear evolution equations using first integral method

    Ahmet Bekir; Ömer Ünsal


    In this paper, we show the applicability of the first integral method to combined KdV-mKdV equation, Pochhammer–Chree equation and coupled nonlinear evolution equations. The power of this manageable method is confirmed by applying it for three selected nonlinear evolution equations. This approach can also be applied to other nonlinear differential equations.

  16. Five Reinforcement Sensitivity Theory (RST) of personality questionnaires : Comparison, validity and generalization

    Krupić, D.; Corr, P.J.; Ručević, S.; Križanić, V.; Gracanin, A.


    There are six purpose-built Reinforcement Sensitivity Theory (RST) personality questionnaires currently in use to measure the fight-flight-freeze system (FFFS), the behavioural inhibition system (BIS), and the behavioural approach system (BAS). They differ in their conceptualizations and operational

  17. Molecular Analysis and Identification of Virulence Gene on pRST98 from Multi-Drug Resistant Salmonella typhi

    Rui Huang; Shuyan Wu; Xueguang Zhang; Yanyun Zhang


    pRST98 is a large and conjugative resistant plasmid (R plasmid) of 98.6 mega-dalton from multi-drug resistant Salmonella typhi (S.typhi), which was classified to incompatibility group C (Inc C). It has been found that pRST98 made its host bacteria not only antibiotic resistant but also more virulent. In this study we explored the possibility of plasmid pRST98 in S. typhi carrying the Salmonella plasmid virulence gene -spv. The plasmid pRST98 was isolated,purified and then digested by nine restriction endonucleases to make the plasmid enzyme profile. Spv-specific PCR and Southern blot were applied to identify the virulence gene on pRST98. The amplified spv fragments spvR and spvB were cloned into pGEM-T EASY and then the DNA sequences were analysed. The fragments of pRST98 digested by endonucleases Bgl Ⅱ, Pst Ⅰ and Sac Ⅱ were identified, which may be useful for molecular analysis and further epidemiological surveillance of pRST98. The results of PCR and Southern blot showed that spv homologous genetic sequence which had been found in all pathogenesis Salmonella spp. except S. typhi was also presented on pRST98. The ORF of spvR and spvB of pRST98 were 894 bp and 1,776 bp, respectively. They have more than 99% homology with that of spvR and spvB on virulence plasmid in S. typhmurium. The genotype research on pRST98 revealed that there is a plasmid carrying genes responsible for drug resistance and virulence in S. typhi. This is the first report for such kind chimerical plasmid in S. typhi. Cellular & Molecular Immunology. 2005;2(2):136-140.

  18. Solidification of Simulated Liquid Effluents Originating From Sodium-Bearing Waste at the Idaho Nuclear Technology and Engineering Center, FY-03 Report

    S. V. Raman; A. K. Herbst; B. A. Scholes; S. H. Hinckley; R. D. Colby


    In this report, the mechanism and methods of fixation of acidic waste effluents in grout form are explored. From the variations in the pH as a function of total solids addition to acidic waste effluent solutions, the stages of gellation, liquefaction, slurry formation and grout development are quantitatively revealed. Experimental results indicate the completion of these reaction steps to be significant for elimination of bleed liquid and for setting of the grout to a dimensionally stable and hardened solid within a reasonable period of about twenty eight days that is often observed in the cement and concrete industry. The reactions also suggest increases in the waste loading in the direction of decreasing acid molarity. Consequently, 1.0 molar SBW-180 waste is contained in higher quantity than the 2.8 molar SBW-189, given the same grout formulation for both effluents. The variations in the formulations involving components of slag, cement, waste and neutralizing agent are represented in the form of a ternary formulation map. The map in turn graphically reveals the relations among the various formulations and grout properties, and is useful in predicting the potential directions of waste loading in grouts with suitable properties such as slurry viscosity, Vicat hardness, and mechanical strength. A uniform formulation for the fixation of both SBW-180 and SBW-189 has emerged from the development of the formulation map. The boundaries for the processing regime on this map are 100 wt% cement to 50 wt% cement / 50 wt% slag, with waste loadings ranging from 55 wt% to 68 wt%. Within these compositional bounds all the three waste streams SBW-180, SBW-189 and Scrub solution are amenable to solidification. A large cost advantage is envisaged to stem from savings in labor, processing time, and processing methodology by adopting a uniform formulation concept for fixation of compositionally diverse waste streams. The experimental efforts contained in this report constitute the

  19. A Solidification Technology for Heavy Metals in EMM Residue%电解金属锰渣中重金属的固化新技术

    李昌新; 钟宏; 王帅; 薛建荣; 张振宇


    以湘西某电解金属锰厂的电解金属锰渣为原料,在分析其浸出特性的基础上,研究硫化钙焙砂固化工艺对电解金属锰渣中重金属离子浸出率的影响。结果表明,利用硫化钙焙砂能有效地固定锰渣中的重金属,固化体浸出液中的重金属浓度明显降低。当硫化钙焙砂用量为电解金属锰渣质量的15%,固化反应时间为3.0 h 时,固化后电解金属锰渣的浸出毒性符合相关国家标准。%Based on an analysis of leaching characteristics of electrolytic manganese residue (EMR)generated in an EMM company in Xiangxi of Hunan province.EMR was immobilized by CaS.The optimal conditions for immobilization process were studied.The results show that the heavy metals in the EMR can be effectively immobilized,when the dosage of CaS was 15% of EMR and the solidification time was 3.0 h.And the leaching toxicity of the amended EMR can meet the requirement stipulated in corresponding national standards.

  20. "Muslim allerførst" - om religiøsitet og diasporiske selvkonstruktioner

    Khawaja, Iram


    Artiklen tager udgangspunkt i empiribaserede refleksioner over unge muslimers måder at fremstille sig selv på baggrund af teoretiske perspektiver på diasporisk selvkonstruktion, transnationale relationer og intersektionalitet. Der ses nærmere på to overordnede tendenser: 1. Positionering som "all...... "allerførst muslim" med distance til kulturelle, nationale og etniske kategorier, og 2. Positionering som muslim i forhold til nationale, etniske og kulturelle tilhørsforhold....

  1. Measuring the coherence of healthy and aphasic discourse production in Chinese using Rhetorical Structure Theory (RST

    Anthony Pak Hin Kong


    Our results seemed to suggest that speakers with anomic aphasia had reduced proportion of essential information content, lower degree of elaboration, simplified discourse structure, and more structural disruptions than their healthy counterparts. We argue that the above characteristics have contributed to the reduced overall coherence in their oral discourse. The use of RST to quantify discourse coherence provided more objective measurement on macro-linguistic characteristics in aphasia and, therefore, warrants further investigation.

  2. Advances on Microstructure Modeling of Solidification Process of Shape Casting

    柳百成; 许庆彦


    Simulation technology for shape casting at macro-scale has been successfully put into engineering application in a number of casting plants and as a result the quality of castings is assured, the research and development time is shortened, and the manufacturing cost is greatly saved as well. In this paper, modeling and simulation technologies of solidification process of shape casting at microstructure-scale, especially deterministic, cellular automaton, and phase field models are studied and reviewed.

  3. Control of dendrite growth by a magnetic field during directional solidification

    Dai, Yanchao; Du, Dafan; Hou, Long; Gagnoud, Annie; Ren, Zhongming; Fautrelle, Yves; Moreau, Rene; Li, Xi


    In this work, the alignment behavior of three kinds of dendrites (Al3Ni, α-Al and Al2Cu dendrites) with a remarkable crystalline anisotropy during directional solidification under an axial magnetic field is studied by the EBSD technology. Experimental results reveal that the magnetic field is capable of tailoring the dendrite alignment during directional solidification. Further, based on the crystalline anisotropy, a method to control the dendrite alignment by adjusting the angle between the magnetic field and the solidification direction is proposed.

  4. Effect of temperature field on solidification structure of pure Al under pulse magneto-oscillation

    Li Bo; Yin Zhenxing; Gong Yongyong


    This article discusses the effect of temperature field on the Pulse Magneto-Oscillation (PMO) induced solidification refinement of pure aluminium to provide more information for the industrial application of the PMO solidification technology. The temperature field is altered mainly by applied variable cooling conditions and pulse parameters. Experimental results show that the refinement effect in the case of full sand mould applied is weakened with the decreasing of cooling rate, however, in ...

  5. Solidification of Al alloys under electromagnetic field



    New theories and technology in the electromagnetic field were put forward about DC casting of Al alloys, including the fundamental research works, I.e, effects of the electromagnetic field on solidus and liquidus, macrosegregation of the main alloying elements, microstructures, content of alloying elements in grains and grain size after solidification under electromagnetic field, and also including a new process-DC casting under low frequency electromagnetic field(LFEMC), which can refine microstructure, eliminate macrosegregation, increase the content of alloying elements within grains, decrease the residual stress, avoid cracks and improve surface quality, and another new process-DC casting under low frequency electromagnetic vibration(LFEVC), which is a high effective method for grain refining.

  6. Directional Solidification Assisted by Liquid Metal Cooling

    Jian ZHANG; Langhong LOU


    An overview of the development and current status of the directional solidification process assisted by liquid metal cooling (LMC) has been presented in this paper. The driving force of the rapid development of the LMC process has been analyzed by considering the demands of (1) newer technologies that can provide higher thermal gradients for alleviated segregation in advanced alloy systems, and (2) better production yield of the large directionally solidified superalloy components. The brief history of the industrialization of the LMC process has been reviewed, followed by the discussion on the LMC parameters including selection of the cooling media, using of the dynamic baffle, and the influence of withdrawal rates and so on. The microstructure and mechanical properties of the traditional superalloys processed by LMC, as well as the new alloys particularly developed for LMC process were then described. Finally, future aspects concerning the LMC process have been summarized.

  7. Automatic RST-based system for a rapid detection of man-made disasters

    Tramutoli, Valerio; Corrado, Rosita; Filizzola, Carolina; Livia Grimaldi, Caterina Sara; Mazzeo, Giuseppe; Marchese, Francesco; Pergola, Nicola


    Man-made disasters may cause injuries to citizens and damages to critical infrastructures. When it is not possible to prevent or foresee such disasters it is hoped at least to rapidly detect the accident in order to intervene as soon as possible to minimize damages. In this context, the combination of a Robust Satellite Technique (RST), able to identify for sure actual (i.e. no false alarm) accidents, and satellite sensors with high temporal resolution seems to assure both a reliable and a timely detection of abrupt Thermal Infrared (TIR) transients related to dangerous explosions. A processing chain, based on the RST approach, has been developed in the framework of the GMOSS and G-MOSAIC projects by DIFA-UNIBAS team, suitable for automatically identify on MSG-SEVIRI images harmful events. Maps of thermal anomalies are generated every 15 minutes (i.e. SEVIRI temporal repetition rate) over a selected area together with kml files (containing information on latitude and longitude of "thermally" anomalous SEVIRI pixel centre, time of image acquisition, relative intensity of anomalies, etc.) for a rapid visualization of the accident position even on Google Earth. Results achieved in the cases of gas pipelines recently exploded or attacked in Russia and in Iraq will be presented in this work.

  8. The Reinforcement Sensitivity Theory of Personality Questionnaire (RST-PQ): Development and validation.

    Corr, Philip J; Cooper, Andrew J


    We report the development and validation of a questionnaire measure of the revised reinforcement sensitivity theory (rRST) of personality. Starting with qualitative responses to defensive and approach scenarios modeled on typical rodent ethoexperimental situations, exploratory and confirmatory factor analyses (CFAs) revealed a robust 6-factor structure: 2 unitary defensive factors, fight-flight-freeze system (FFFS; related to fear) and the behavioral inhibition system (BIS; related to anxiety); and 4 behavioral approach system (BAS) factors (Reward Interest, Goal-Drive Persistence, Reward Reactivity, and Impulsivity). Theoretically motivated thematic facets were employed to sample the breadth of defensive space, comprising FFFS (Flight, Freeze, and Active Avoidance) and BIS (Motor Planning Interruption, Worry, Obsessive Thoughts, and Behavioral Disengagement). Based on theoretical considerations, and statistically confirmed, a separate scale for Defensive Fight was developed. Validation evidence for the 6-factor structure came from convergent and discriminant validity shown by correlations with existing personality scales. We offer the Reinforcement Sensitivity Theory of Personality Questionnaire to facilitate future research specifically on rRST and, more broadly, on approach-avoidance theories of personality. (PsycINFO Database Record

  9. Effect of thermosolutal convection on directional solidification

    Suresh V Garimella; James E Simpson


    The impact of thermosolutal convection during directional solidification is explored via results of numerical investigations. Results from fully transient numerical simulations of directional solidification in a differentially heated cavity under terrestrial conditions and Bridgman crystal growth in space are discussed. The pivotal role of both thermal and solutal convection in the solidification process is illustrated by examining these two cases. In particular, radial and longitudinal macrosegregation resulting from this thermosolutal convection is discussed.

  10. Molecular Analysis and Identification of Virulence Gene on pRST98 from Multi-Drug Resistant Salmonella typhi

    RuiHuang; ShuyanWu; XueguangZhang; YanyunZhang


    pRST98 is a large and conjugative resistant plasmid (R plasmid) of 98.6 mega-dalton from multi-drug resistant Salmonella typhi (S. typhi), which was classified to incompatibility group C (Inc C). It has been found that pRST98 made its host bacteria not only antibiotic resistant but also more virulent. In this study we explored the possibility of plasmid pRsr98 in S. typhi carrying the Salmonella plasmid virulence gene - spv. The plasmid pRST98 was isolated, purified and then digested by nine restriction endonucleases to make the plasmid enzyme profile. Spv-specific PCR and Southern blot were applied to identify the virulence gene on pRsr98. The amplified spv fragments spvR and spvB were cloned into pGEM-T EASY and then the DNA sequences were analysed. The fragments of pRST98 digested by endonucleases Bgl II, Pst I and Sac II were identified, which may be useful for molecular analysis and further epidemiological surveillance of pRsT98. The results of PCR and Southern blot showed that spv homologous genetic sequence which had been found in all pathogenesis Salmonella spp. except S. typhi was also presented on pRST98. The ORF of spvR and spvB of pRsr98 were 894 bp and 1,776 bp, respectively. They have more than 99% homology with that of spvR and spvB on virulence plasmid in S. typhmurium. The genotype research on pRST98 revealed that there is a plasmid carrying genes responsible for drug resistance and virulence in S. typhi. This is the first report for such kind chimerical plasmid in S. typhi. Cellular & Molecular Immunology. 2005;2(2):136-140.Key Words: s. typhi, R plasmid, virulence gene

  11. Impact of Metal Droplets: A Numerical Approach to Solidification

    Koldeweij, Robin; Mandamparambil, Rajesh; Lohse, Detlef


    Layer-wise deposition of material to produce complex products is a subject of increasing technological relevance. Subsequent deposition of droplets is one of the possible 3d printing technologies to accomplish this. The shape of the solidified droplet is crucial for product quality. We employ the volume-of-fluid method (in the form of the open-source code Gerris) to study liquid metal (in particular tin) droplet impact. Heat transfer has been implemented based on the enthalpy approach for the liquid-solid phase. Solidification is modeled by adding a sink term to the momentum equations, reducing Navier-Stokes to Darcy's law for high solid fraction. Good agreement is found when validating the results against experimental data. We then map out a phase diagram in which we distinguish between solidification behavior based on Weber and Stefan number. In an intermediate impact regime impact, solidification due to a retracting phase occurs. In this regime the maximum spreading diameter almost exclusively depends on Weber number. Droplet shape oscillations lead to a broad variation of the morphology of the solidified droplet and determine the final droplet height. TNO.

  12. Structural Properties of Liquid SiC during Rapid Solidification

    WanJun Yan


    Full Text Available The rapid solidification of liquid silicon carbide (SiC is studied by molecular dynamic simulation using the Tersoff potential. The structural properties of liquid and amorphous SiC are analyzed by the radial distribution function, angular distribution function, coordination number, and visualization technology. Results show that both heteronuclear and homonuclear bonds exist and no atomic segregation occurs during solidification. The bond angles of silicon and carbon atoms are distributed at around 109° and 120°, respectively, and the average coordination number is <4. Threefold carbon atoms and fourfold silicon atoms are linked together by six typical structures and ultimately form a random network of amorphous structure. The simulated results help understand the structural properties of liquid and amorphous SiC, as well as other similar semiconductor alloys.

  13. Fluid mechanics of directional solidification at reduced gravity

    Chen, C. F.


    The primary objective of the proposed research is to provide additional groundbased support for the flight experiment 'Casting and Solidification Technology' (CAST). This experiment is to be performed in the International Microgravity Laboratory-1 (IML-1) scheduled to be flown on a space shuttle mission scheduled for 1992. In particular, we will provide data on the convective motion and freckle formation during directional solidification of NH4Cl from its aqueous solution at simulated parameter ranges equivalent to reducing the gravity from the sea-level value down to 0.1 g or lower. The secondary objectives of the proposed research are to examine the stability phenomena associated with the onset of freckles and the mechanisms for their subsequent growth and decline (to eventual demise of some) by state-of-the-art imaging techniques and to formulate mathematical models for the prediction of the observed phenomena.

  14. Morphology of solidification front in eutectic

    M. Trepczyńska - Łent


    Full Text Available In this paper the analysis of morphology of solidification front in eutectic made. It was present influence of composition, solidification velocity, concentration micro-field and capillarity effects on the morphology of the solid/liquid interface. It was introduced phase-field model.

  15. Numerical modelling of rapid solidification

    Pryds, Nini; Hattel, Jesper Henri


    A mathematical model of the melt spinning process has been developed based on the control-volume finite-difference method. The model avoids some of the limitations of the previous models, for example including the effect of the wheel in the heat how calculations and the temperature dependence...... of the thermophysical parameters of the material. The nucleation temperature was calculated based on the heterogeneous nucleation theory. The effect of various parameters, such as the heat transfer coefficient, the nucleation temperature and the heating and type of the wheel on the rapid solidification behaviour...

  16. A MODIS-Based Robust Satellite Technique (RST for Timely Detection of Oil Spilled Areas

    Teodosio Lacava


    Full Text Available Natural crude-oil seepages, together with the oil released into seawater as a consequence of oil exploration/production/transportation activities, and operational discharges from tankers (i.e., oil dumped during cleaning actions represent the main sources of sea oil pollution. Satellite remote sensing can be a useful tool for the management of such types of marine hazards, namely oil spills, mainly owing to the synoptic view and the good trade-off between spatial and temporal resolution, depending on the specific platform/sensor system used. In this paper, an innovative satellite-based technique for oil spill detection, based on the general robust satellite technique (RST approach, is presented. It exploits the multi-temporal analysis of data acquired in the visible channels of the Moderate Resolution Imaging Spectroradiometer (MODIS on board the Aqua satellite in order to automatically and quickly detect the presence of oil spills on the sea surface, with an attempt to minimize “false detections” caused by spurious effects associated with, for instance, cloud edges, sun/satellite geometries, sea currents, etc. The oil spill event that occurred in June 2007 off the south coast of Cyprus in the Mediterranean Sea has been considered as a test case. The resulting data, the reliability of which has been evaluated by both carrying out a confutation analysis and comparing them with those provided by the application of another independent MODIS-based method, showcase the potential of RST in identifying the presence of oil with a high level of accuracy.

  17. Crystalline and liquid Si3 N4 characterization by first-principles molecular dynamics simulations

    Castellani Niccoló


    Full Text Available Silicon nitride (Si3 N4 has a wide range of engineering applications where its mechanical and electronic properties can be effectively exploited. In particular, in the microelectronics field, the amorphous silicon nitride films are widely used as charge storage layer in metal-alumina-nitrideoxide nonvolatile memory devices. Atomic structure of amorphous silicon nitride is characterized by an high concentration of traps that control the electric behavior of the final device by the trappingde-trapping mechanism of the electrical charge occurring in its traps. In order to have a deep understanding of the material properties and, in particular, the nature of the electrical active traps a detailed numerical characterization of the crystalline and liquid phases is mandatory. For these reasons first-principles molecular dynamics simulations are extensively employed to simulate the crystalline Si3 N4 in its crystalline and liquid phases. Good agreement with experimental results is obtained in terms of density and formation entalpy. Detailed characterization of c-Si3 N4 electronic properties is performed in terms of band structure and band gap. Then constant temperature and constant volume first-principles molecular dynamics is used to disorder a stoichiometric sample of Si3 N4 . Extensive molecular dynamics simulations are performed to obtain a reliable liquid sample whose atomic structure does not depend on the starting atomic configuration. Detailed characterization of the atomic structure is achieved in terms of radial distribution functions and total structure factor.

  18. Efficient dynamic pruning on largest scores fi rst (LSF) retrieval

    Kun JIANG; Yue-xiang YANG


    Inverted index traversal techniques have been studied in addressing the query processing performance challenges of web search engines, but still leave much room for improvement. In this paper, we focus on the inverted index traversal on document-sorted indexes and the optimization technique called dynamic pruning, which can efficiently reduce the hardware computational resources required. We propose another novel exhaustive index traversal scheme called largest scores fi rst (LSF) retrieval, in which the candidates are fi rst selected in the posting list of important query terms with the largest upper bound scores and then fully scored with the contribution of the remaining query terms. The scheme can effectively reduce the memory consumption of existing term-at-a-time (TAAT) and the candidate selection cost of existing document-at-a-time (DAAT) retrieval at the expense of revisiting the posting lists of the remaining query terms. Preliminary analysis and implementation show comparable performance between LSF and the two well-known baselines. To further reduce the number of postings that need to be revisited, we present efficient rank safe dynamic pruning techniques based on LSF, including two important optimizations called list omitting (LSF_LO) and partial scoring (LSF_PS) that make full use of query term importance. Finally, experimental results with the TREC GOV2 collection show that our new index traversal approaches reduce the query latency by almost 27% over the WAND baseline and produce slightly better results compared with the MaxScore baseline, while returning the same results as exhaustive evaluation.

  19. Analysis of Borrelia burgdorferi Genotypes in Patients with Lyme Arthritis: High Frequency of RST 1 Strains in Antibiotic-Refractory Arthritis

    Jones, Kathryn L.; McHugh, Gail A.; Glickstein, Lisa J.; Steere, Allen C.


    Objective Most of the B. burgdorferi genotypes have been isolated from erythema migrans (EM) skin lesions in patients with Lyme disease; outer-surface protein C (OspC) type K strains, which are 16S-23S rRNA intergenic spacer type 2 (RST 2), are most commonly recovered, but a higher percentage of OspC type A strains (RST 1), the next most common type, are detectable in blood. Our goals were to determine the B. burgdorferi genotypes in the joints of patients with Lyme arthritis. Methods Joint fluid samples from 124 patients seen over a 30-year period were analyzed for OspC types by semi-nested PCR and sequencing, and for RST by nested PCR and RFLP techniques. This information was correlated with clinical outcome. Results OspC and RST genotypes could be determined in 49 of the 124 joint fluid samples (40%). Of the 49 samples, 21 (43%) were OspC type K (RST 2), 11 (22%) were type A (RST 1), and 17 (35%) were distributed among 8 other OspC types and all 3 RSTs. However, among 17 patients who received current antibiotic regimens, all 7 infected with RST 1 strains had antibiotic-refractory arthritis compared with 4 of 6 patients infected with RST 2 strains and only 1 of 4 infected with RST 3 strains (P=0.03). Conclusions Most of the B. burgdorferi genotypes infected the joints of patients with Lyme arthritis, particularly OspC type K (RST 2); and genotype frequencies reflected those in EM skin lesions. However, RST 1 strains were most frequent in patients with antibiotic-refractory arthritis. PMID:19565522

  20. ‘Do You Want a Receipt?’ Combating VAT and RST Evasion with Lottery Tickets

    S.J.C. Hemels (Sigrid); M. Fabbri (Marco)


    textabstractGovernments both in developed and developing countries are facing the problem of value added tax (VAT) and retail sales tax (RST) evasion. This explains a growing interest in policies alternative to the traditional methods of deterrence. This paper describes the achievements resulting

  1. rst Konstantin von Polock und die Geschichte Livlands im dritten Viertel des 13. Jahrhunderts / Anti Selart

    Selart, Anti, 1973-


    13. ja 14. sajandi Teotooni ordu allikates esinevast vürst Konstantinist. Tema isiku identifitseerimiset. Autor peab Konstantini pärast Leedu suurvürsti Tatvila surma 1263. aastal esile kerkinud Smolenski või Polotski suguvõsa esindajaks



    Facing the market economy and global challenge the development of manufacturing industry especially casting industry is critical to the national economy. To reform the traditional casting industry by using computer technology is one of the hottest research frontiers studied by many researchers and engineers. Computer simulation of solidification process of shaped casting can assure the quality of casting, optimize the casting technology, shorten the lead time and therefore decrease the developing and manufacturing cost. Recently, numerical simulation of mold-filling and solidification processes of shaped casting and prediction of microstructure and property as well are extensively studied and put into application in many casting plants with many successful simulation cases.

  3. PREFACE: Third International Conference on Advances in Solidification Processes (ICASP - 3)

    Zimmermann, Gerhard; Ratke, Lorenz


    The 3rd International Conference on Advances in Solidification Processes was held in the Rolduc Abbey in the Netherlands a few kilometres away from Aachen. Around 200 scientists from 24 countries come in for the four day meeting. They found a stimulating but also relaxing environment and atmosphere, with beautiful weather and the medieval abbey inviting for walks, discussions, sitting outside and drinking a beer or wine. The contributions given at the conference reflected recent advances in various topics of solidification processes, ranging from fundamental aspects to applied casting technologies. In 20 oral sessions and a large poster session innovative results of segregation phenomena, microstructure evolution, nucleation and growth, phase formation, polyphase solidification, rapid solidification and welding, casting technology, thermophysics of molten alloys, solidification with forced melt flow and growth of single crystals and superalloys together with innovative diagnostic techniques were presented. Thereby, findings from experiments as well as from numerical modeling on different lengths scales were jointly discussed and contribute to new insight in solidification behaviour. The papers presented in this open access proceedings cover about half the oral and poster presentations given. They were carefully reviewed as in classical peer reviewed journals by two independent referees and most of them were revised and thus improved according to the reviewers comments. We think that this collection of papers presented at ICASP-3 gives an impression of the excellent contributions made. The papers embrace both the basic and applied aspects of solidification. We especially wish to express our appreciation for the team around Georg Schmitz and Margret Nienhaus organising this event and giving us their valued advice and support at every stage in preparing the conference. We also thank Lokasenna Lektorat for taking the task of checking all language-associated issues and

  4. Solidification of gold nanoparticles in carbon nanotubes.

    Arcidiacono, S; Walther, J H; Poulikakos, D; Passerone, D; Koumoutsakos, P


    The structure and the solidification of gold nanoparticles in a carbon nanotube are investigated using molecular dynamics simulations. The simulations indicate that the predicted solidification temperature of the enclosed particle is lower than its bulk counterpart, but higher than that observed for clusters placed in vacuum. A comparison with a phenomenological model indicates that, in the considered range of tube radii (R(CNT)) of 0.5 < R(CNT) < 1.6 nm, the solidification temperature depends mainly on the length of the particle with a minor dependence on R(CNT).

  5. Rapid solidification of immiscible alloys

    Bosco, Enrica; Rizzi, Paola; Baricco, Marcello E-mail:


    Immiscible alloys have been rapidly solidified for the preparation of granular materials with giant magnetoresistance properties. Au-based (Au-Co and Au-Fe) and Cu-based (Cu-Co and Cu-Fe) systems have been investigated. Single supersaturated solid solution has been obtained for Au-Fe, whereas three FCC solid solutions with different Co content have been found for Au-Co. For Cu-Co and Cu-Fe a limit of solubility in Cu has been observed. Ni additions to Cu-Fe strongly enhance solid solubility. A thermodynamic analysis has been used to describe the competition between partition-less solidification and phase separation in undercooled liquid.

  6. Evolution of solidification texture during additive manufacturing

    Wei, H L; Mazumder, J; DebRoy, T


    Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data...

  7. Alternating grain orientation and weld solidification cracking

    Kou, S.; Le, Y.


    A new mechanism for reducing weld solidification cracking was proposed, based on the concept of the crack path and resistance to crack propagation, and its effectiveness was verified in magnetically oscillated GTA welds of a rather crack susceptible material 2014 aluminum alloy. This mechanism, i.e., alternating grain orientation, was most pronounced in welds made with transverse arc oscillation of low frequency and high amplitude, and solidification cracking was dramatically reduced in these welds. The effect of the arc oscillation pattern, amplitude, and frequency on the formation of alternating columnar grains and the reduction of solidification cracking in GTA welds of 2014 aluminum alloy was examined and explained. The present study demonstrated for the first time that columnar grains can, in fact, be very effective in reducing solidification cracking, provided that they are oriented favorably.

  8. A visualization of the eutectic solidification process

    E. Olejnik


    Full Text Available The study presents a visualization of the sequence of formation of eutectic grains during solidification in volume and directional solidification of model organic materials from the system of salol (faceted phase - camphor (non-faceted phase and carbon tetrabromide (non-faceted phase - hexachloroethane (non-faceted phase. It has been proved that the faceted phase may act as a substrate for nucleation of the non-faceted phase, while the non-faceted phase in a eutectic grain is of polycrystalline character. The directional solidification of non-faceted/non-faceted eutectic enabled disclosing various structural defects, while solidification in volume explained in what way the, so called, halo effect is formed.

  9. Evolution of solidification texture during additive manufacturing.

    Wei, H L; Mazumder, J; DebRoy, T


    Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.

  10. A Citizen's Guide to Solidification and Stabilization

    This guide describes how solidification and stabilization refer to a group of cleanup methods that prevent or slow the release of harmful chemicals from wastes, such as contaminated soil, sediment, and sludge.

  11. Stabilization/solidification of TSCA incinerator ash

    Spence, R.D.; Trotter, D.R.; Francis, C.L.; Morgan, I.L.


    Stabilization/solidification is a well-known waste treatment technique that utilizes different additives and processes. The Phoenix Ash Technology of the Technical Innovation Development Engineering Company is such a technique that uses Cass C fly ash and mechanical pressure to make brick waste forms out of solid wastes, such as the bottom ash from the Toxic Substances Control Act incinerator at the Oak Ridge K-25 Site. One advantage of this technique is that no volume increase over the bulk volume of the bottom ash occurs. This technique should have the same high pH stabilization for Resource Conservation and Recovery Act metals as similar techniques. Also, consolidation of the bottom ash minimizes the potential problems of material dispersion and container corrosion. The bottom ash was spiked with {sup 99}{Tc} to test the effectiveness of the bricks as a physical barrier. The {sup 99}{Tc} leachability index measured for these bricks was 6.8, typical for the pertechnetate anion in cementitious waste forms, indicating that these bricks have accessible porosity as high as that of other cementitious waste forms, despite the mechanical compression, higher waste form density, and water resistant polymer coating.

  12. Att utveckla elevers läsförståelse : En kvalitativ studie över lärares arbete med läsförståelse och begrepp i grundskolans senare år

    Martinsson, Margaretha


    I undersökningar som Progress in International Reading Literacy Study (PIRLS) och Programme for International Student Assessment (PISA) visar Sverige nedslående resultat när det gäller elevers läsförståelse. Samtidigt visar skolans styrdokument att lärare i alla ämnen är ansvariga att arbeta språkutvecklande. Mitt syfte med studien är att undersöka hur några lärare i naturorienterade ämnen arbetar med läsförståelse och begrepp i undervisningen, samt hur de stödjer elever med bristande läsförs...

  13. Numerical prediction of the incremental melting and solidification process

    Jun Wang; Chengchang Jia; Sheng Yin


    A mathematical formulation is applied to represent the phenomena in the incremental melting and solidification process (IMSP), and the temperature and electromagnetic fields and the depth of steel liquid phase are calculated by a finite difference technique using the control volume method. The result shows that the predicted values are in good agreement with the observations. In accordance with the calculated values for different kinds of materials and different size of molds, the technological parameter of the IMS process such as the power supply and the descending speed rate can be determined.

  14. rst transcriptional activity influences kirre mRNA concentration in the Drosophila pupal retina during the final steps of ommatidial patterning.

    Maiaro Cabral Rosa Machado

    Full Text Available BACKGROUND: Drosophila retinal architecture is laid down between 24-48 hours after puparium formation, when some of the still uncommitted interommatidial cells (IOCs are recruited to become secondary and tertiary pigment cells while the remaining ones undergo apoptosis. This choice between survival and death requires the product of the roughest (rst gene, an immunoglobulin superfamily transmembrane glycoprotein involved in a wide range of developmental processes. Both temporal misexpression of Rst and truncation of the protein intracytoplasmic domain, lead to severe defects in which IOCs either remain mostly undifferentiated and die late and erratically or, instead, differentiate into extra pigment cells. Intriguingly, mutants not expressing wild type protein often have normal or very mild rough eyes. METHODOLOGY/PRINCIPAL FINDINGS: By using quantitative real time PCR to examine rst transcriptional dynamics in the pupal retina, both in wild type and mutant alleles we showed that tightly regulated temporal changes in rst transcriptional rate underlie its proper function during the final steps of eye patterning. Furthermore we demonstrated that the unexpected wild type eye phenotype of mutants with low or no rst expression correlates with an upregulation in the mRNA levels of the rst paralogue kin-of-irre (kirre, which seems able to substitute for rst function in this process, similarly to their role in myoblast fusion. This compensatory upregulation of kirre mRNA levels could be directly induced in wild type pupa upon RNAi-mediated silencing of rst, indicating that expression of both genes is also coordinately regulated in physiological conditions. CONCLUSIONS/SIGNIFICANCE: These findings suggest a general mechanism by which rst and kirre expression could be fine tuned to optimize their redundant roles during development and provide a clearer picture of how the specification of survival and apoptotic fates by differential cell adhesion during the

  15. Exact solutions of the generalized Lane–Emden equations of the first and second kind

    Ben Muatjetjeja; Chaudry Masood Khalique


    In this paper we discuss the integrability of the generalized Lane–Emden equations of the first and second kinds. We carry out their Noether symmetry classification. Various cases for the arbitrary functions in the equations are obtained for which the equations have Noether point symmetries. First integrals of such cases are obtained and also reduction to quadrature of the corresponding Lane–Emden equations are presented. New cases are found.

  16. Moods as ups and downs of the motivation pendulum: Revisiting Reinforcement Sensitivity Theory (RST) in Bipolar Disorder

    Tal eGonen; Haggai eSharon; Godfrey ePearlson; Talma eHendler


    Motivation is a key neurobehavioral concept underlying adaptive responses to environmental incentives and threats. As such, dysregulation of motivational processes may be critical in the formation of abnormal behavioral patterns/tendencies. According to the long standing model of the Reinforcement Sensitivity Theory (RST), motivation behaviors are driven by three neurobehavioral systems mediating the sensitivity to punishment, reward or goal-conflict. Corresponding to current neurobehavioral ...

  17. Moods as ups and downs of the motivation pendulum: revisiting reinforcement sensitivity theory (RST) in bipolar disorder

    Gonen, Tal; Sharon, Haggai; Pearlson, Godfrey; Hendler, Talma


    Motivation is a key neurobehavioral concept underlying adaptive responses to environmental incentives and threats. As such, dysregulation of motivational processes may be critical in the formation of abnormal behavioral patterns/tendencies. According to the long standing model of the Reinforcement Sensitivity Theory (RST), motivation behaviors are driven by three neurobehavioral systems mediating the sensitivity to punishment, reward or goal-conflict. Corresponding to current neurobehavioral ...

  18. Moods as ups and downs of the motivation pendulum: Revisiting Reinforcement Sensitivity Theory (RST in Bipolar Disorder

    Tal eGonen


    Full Text Available Motivation is a key neurobehavioral concept underlying adaptive responses to environmental incentives and threats. As such, dysregulation of motivational processes may be critical in the formation of abnormal behavioral patterns/tendencies. According to the long standing model of the Reinforcement Sensitivity Theory (RST, motivation behaviors are driven by three neurobehavioral systems mediating the sensitivity to punishment, reward or goal-conflict. Corresponding to current neurobehavioral theories in psychiatry, this theory links abnormal motivational drives to abnormal behavior; viewing depression and mania as two abnormal extremes of reward driven processes leading to either under or over approach tendencies, respectively. We revisit the RST framework in the context of bipolar disorder (BD and challenge this concept by suggesting that dysregulated interactions of both punishment and reward related processes better account for the psychological and neural abnormalities observed in BD. We further present an integrative model positing that the three parallel motivation systems currently proposed by the RST model, can be viewed as subsystems in a large-scale neurobehavioral network of motivational decision making.

  19. Moods as ups and downs of the motivation pendulum: revisiting reinforcement sensitivity theory (RST) in bipolar disorder.

    Gonen, Tal; Sharon, Haggai; Pearlson, Godfrey; Hendler, Talma


    Motivation is a key neurobehavioral concept underlying adaptive responses to environmental incentives and threats. As such, dysregulation of motivational processes may be critical in the formation of abnormal behavioral patterns/tendencies. According to the long standing model of the Reinforcement Sensitivity Theory (RST), motivation behaviors are driven by three neurobehavioral systems mediating the sensitivity to punishment, reward or goal-conflict. Corresponding to current neurobehavioral theories in psychiatry, this theory links abnormal motivational drives to abnormal behavior; viewing depression and mania as two abnormal extremes of reward driven processes leading to either under or over approach tendencies, respectively. We revisit the RST framework in the context of bipolar disorder (BD) and challenge this concept by suggesting that dysregulated interactions of both punishment and reward related processes better account for the psychological and neural abnormalities observed in BD. We further present an integrative model positing that the three parallel motivation systems currently proposed by the RST model, can be viewed as subsystems in a large-scale neurobehavioral network of motivational decision making.

  20. Formation of metastable phases during solidification of Al-3.2 wt% Mn

    Khvan, Alexandra V.; Cheverikin, Vladimir V.; Dinsdale, Alan T. [Thermochemistry of Materials SRC, National University of Science and Technology MISIS, 4 Leninsky Prosp., 119049 Moscow (Russian Federation); Watson, Andy [Thermochemistry of Materials SRC, National University of Science and Technology MISIS, 4 Leninsky Prosp., 119049 Moscow (Russian Federation); Institute for Materials Research, School of Chemical and Process Engineering, University of Leeds, LS2 9JT Leeds (United Kingdom); Levchenko, Viktor V.; Zolotorevskiy, Vadim S. [Department of Physical Metallurgy of Non-Ferrous Metals, National University of Science and Technology MISIS, 4 Leninsky Prosp., 119049 Moscow (Russian Federation)


    Highlights: • During rapid solidification of Al-Mn alloys, expected phases do not always form. • This has been verified in this study. • Calculations of phase equilibria using thermodynamics can help to explain this. • ‘Stable’ phases are shown to be kinetically inhibited from forming. - Abstract: The solidification of the technologically important Al-rich Al-Mn alloys has been studied both experimentally and by calculation of the phase equilibria. The results of previous experimental studies, which indicated that one or more stable intermetallic phases are suppressed on solidification from the liquid, have been confirmed. It was shown that it is important to consider the formation of Al{sub 11}Mn{sub 4} even though other intermetallic phases have a higher driving force for solidification. It is concluded that while an understanding of the thermodynamic properties of the phases is fundamental to modelling the formation of microstructure associated with solidification, it is necessary to take into account other effects such as the thermodynamic properties at interfaces and their effect on nucleation.

  1. A Chebyshev Collocation Method for Moving Boundaries, Heat Transfer, and Convection During Directional Solidification

    Zhang, Yiqiang; Alexander, J. I. D.; Ouazzani, J.


    Free and moving boundary problems require the simultaneous solution of unknown field variables and the boundaries of the domains on which these variables are defined. There are many technologically important processes that lead to moving boundary problems associated with fluid surfaces and solid-fluid boundaries. These include crystal growth, metal alloy and glass solidification, melting and name propagation. The directional solidification of semi-conductor crystals by the Bridgman-Stockbarger method is a typical example of such a complex process. A numerical model of this growth method must solve the appropriate heat, mass and momentum transfer equations and determine the location of the melt-solid interface. In this work, a Chebyshev pseudospectra collocation method is adapted to the problem of directional solidification. Implementation involves a solution algorithm that combines domain decomposition, finite-difference preconditioned conjugate minimum residual method and a Picard type iterative scheme.

  2. Microdomain patterns from directional eutectic solidification and epitaxy

    De Rosa C; Park; Thomas; Lotz


    Creating a regular surface pattern on the nanometre scale is important for many technological applications, such as the periodic arrays constructed by optical microlithography that are used as separation media in electrophoresis, and island structures used for high-density magnetic recording devices. Block copolymer patterns can also be used for lithography on length scales below 30 nanometres (refs 3-5). But for such polymers to prove useful for thin-film technologies, chemically patterned surfaces need to be made substantially defect-free over large areas, and with tailored domain orientation and periodicity. So far, control over domain orientation has been achieved by several routes, using electric fields, temperature gradients, patterned substrates and neutral confining surfaces. Here we describe an extremely fast process that leads the formation of two-dimensional periodic thin films having large area and uniform thickness, and which possess vertically aligned cylindrical domains each containing precisely one crystalline lamella. The process involves rapid solidification of a semicrystalline block copolymer from a crystallizable solvent between glass substrates using directional solidification and epitaxy. The film is both chemically and structurally periodic, thereby providing new opportunities for more selective and versatile nanopatterned surfaces.

  3. A Review of Permanent Magnet Stirring During Metal Solidification

    Zeng, Jie; Chen, Weiqing; Yang, Yindong; Mclean, Alexander


    Rather than using conventional electromagnetic stirring (EMS) with three-phase alternating current, permanent magnet stirring (PMS), based on the use of sintered NdFeB material which has excellent magnetic characteristics, can be employed to generate a magnetic field for the stirring of liquid metal during solidification. Recent experience with steel casting indicates that PMS requires less than 20 pct of the total energy compared with EMS. Despite the excellent magnetic density properties and low power consumption, this relatively new technology has received comparatively little attention by the metal casting community. This paper reviews simulation modeling, experimental studies, and industrial trials of PMS conducted during recent years. With the development of magnetic simulation software, the magnetic field and associated flow patterns generated by PMS have been evaluated. Based on the results obtained from laboratory experiments, the effects of PMS on metal solidification structures and typical defects such as surface pinholes and center cavities are summarized. The significance of findings obtained from trials of PMS within the metals processing sector, including the continuous casting of steel, are discussed with the aim of providing an overview of the relevant parameters that are of importance for further development and industrial application of this innovative technology.

  4. Finite element modelling of solidification phenomena

    K N Seetharamu; R Paragasam; Ghulam A Quadir; Z A Zainal; B Sathya Prasad; T Sundararajan


    The process of solidification process is complex in nature and the simulation of such process is required in industry before it is actually undertaken. Finite element method is used to simulate the heat transfer process accompanying the solidification process. The metal and the mould along with the air gap formation is accounted in the heat transfer simulation. Distortion of the casting is caused due to non-uniform shrinkage associated with the process. Residual stresses are induced in the final castings. Simulation of the shrinkage and the thermal stresses are also carried out using finite element methods. The material behaviour is considered as visco-plastic. The simulations are compared with available experimental data and the comparison is found to be good. Special considerations regarding the simulation of solidification process are also brought out.

  5. Solidification control in continuous casting of steel

    S Mazumdar; S K Ray


    An integrated understanding of heat transfer during solidification, friction/lubrication at solid-liquid interface, high temperature properties of the solidifying shell etc. is necessary to control the continuous casting process. The present paper elaborates upon the knowledge developed in the areas of initial shell formation, mode of mould oscillation, and lubrication mechanism. The effect of these issues on the caster productivity and the quality of the product has been discussed. The influence of steel chemistry on solidification dynamics, particularly with respect to mode of solidification and its consequence on strength and ductility of the solidifying shell, has been dealt with in detail. The application of these basic principles for casting of stainless steel slabs and processing to obtain good quality products have been covered.

  6. Non newtonian annular alloy solidification in mould

    Moraga, Nelson O.; Garrido, Carlos P. [Universidad de La Serena, Departamento de Ingenieria Mecanica, La Serena (Chile); Castillo, Ernesto F. [Universidad de Santiago de Chile, Departamento de Ingenieria Mecanica, Santiago (Chile)


    The annular solidification of an aluminium-silicon alloy in a graphite mould with a geometry consisting of horizontal concentric cylinders is studied numerically. The analysis incorporates the behavior of non-Newtonian, pseudoplastic (n=0.2), Newtonian (n=1), and dilatant (n=1.5) fluids. The fluid mechanics and heat transfer coupled with a transient model of convection diffusion are solved using the finite volume method and the SIMPLE algorithm. Solidification is described in terms of a liquid fraction of a phase change that varies linearly with temperature. The final results make it possible to infer that the fluid dynamics and heat transfer of solidification in an annular geometry are affected by the non-Newtonian nature of the fluid, speeding up the process when the fluid is pseudoplastic. (orig.)

  7. Segregation effects and phase developments during solidification of alloy 625

    Højerslev, Christian; Tiedje, Niels Skat; Hald, John


    The solidification behaviour of pure Alloy 625, and Alloy 625 enriched respectively in iron and carbon, was investigated in situ by hot-stage light optical microscopy. Using this technique planar front solidification for distances of several hundred microns was facilitated. After solidification...

  8. Solidification of ternary systems with a nonlinear phase diagram

    Alexandrov, D. V.; Dubovoi, G. Yu.; Malygin, A. P.; Nizovtseva, I. G.; Toropova, L. V.


    The directional solidification of a ternary system with an extended phase transition region is theoretically studied. A mathematical model is developed to describe quasi-stationary solidification, and its analytical solution is constructed with allowance for a nonlinear liquidus line equation. A deviation of the liquidus equation from a linear function is shown to result in a substantial change in the solidification parameters.

  9. Transient convective instabilities in directional solidification

    Meca, Esteban


    We study the convective instability of the melt during the initial transient in a directional solidification experiment in a vertical configuration. We obtain analytically the dispersion relation, and perform an additional asymptotic expansion for large Rayleigh number that permits a simpler analytical analysis and a better numerical behavior. We find a transient instability, i.e. a regime in which the system destabilizes during the transient whereas the final unperturbed steady state is stable. This could be relevant to growth mode predictions in solidification.

  10. Conditions Of Directional Solidification Affect Superalloy

    Schmidt, D. D.; Alter, W. S.; Hamilton, W. D.; Parr, R. A.


    Report describes experiments to determine effects of gradient of temperature and rate of solidification on microstructure and fatigue properties of nickel-based superalloy MAR-M246(Hf). Enhancement of properties extends lifespans of objects, including turbo-pump blades of Space Shuttle Main Engines. Results indicate significant improvements in fatigue properties derived through manipulation of parameters of directional solidification. Particularly MAR-M246(Hf) for turbine blades contains small, well-dispersed blocky carbide and microstructure with small distances between dendrite arms, and without eutectic phase.

  11. Solidification Based Grain Refinement in Steels


    likely to form, the author conducted a Schiel solidification analysis using Thermo-Calc. Table 2 lists the steel chemistry used based on the actual...the phases present during freezing were calculated. Table 3 Steel chemistry used fur Schiel analysis. C (wt. %) Mn (wt %) AKwt. %) Ti(wt. %) N(wt...0.4 0.6 0.8 Mole fraction of all solid phases Figure 23 Schiel solidification analysis for 0.1 % Ti containing 1030 steel. Figure 25 depicts the

  12. Solidification on fly ash, Yugoslav experiences

    Knezevic, D. [Mining Institute, Belgrade (Yugoslavia); Popov, S.; Salatic, D. [Faculty of Mining and Geology, Belgrade (Yugoslavia)


    A study was performed on ashes produced in the combustion process of coal from the Kosovo coal basin, in order to determine the potential and conditions of ash self-solidification. Investigations showed that the ash properties allows for the transformation into a solid mass through a controlled mixing with water. The optimal concentration of ash is 50 percent and the hydro-mixture is behaving as a Bingham plastic fluid. Solidification is obtained in a relatively short period (within 3 to 5 days) without additives. The resulting solidified mass is very consistent and stable

  13. Observations of a monotectic solidification interface morphology

    Kaukler, W. F.; Frazier, D. O.


    For detailed studies of the region around a solidification interface on a microscopic scale, a very thin (essentially two-dimensional) test cell may be translated across two temperature-controlled heating/cooling blocks and viewed with a microscope. Such a device is sometimes referred to as a temperature gradient microscope stage (TGS). Of particular interest in this study is the behavior of a monotectic type solution during solidification. Succinonitrile based model systems for metallic monotectic alloys, when solidified on a TGS, form an unusual 'worm-like' micromorphology. These interfaces are observable in situ under high optical magnification during growth.

  14. Modern methods for the quality management of high-rate melt solidification

    Vasiliev, V. A.; Odinokov, S. A.; Serov, M. M.


    The quality management of high-rate melt solidification needs combined solution obtained by methods and approaches adapted to a certain situation. Technological audit is recommended to estimate the possibilities of the process. Statistical methods are proposed with the choice of key parameters. Numerical methods, which can be used to perform simulation under multifactor technological conditions, and an increase in the quality of decisions are of particular importance.

  15. Modeling and simulation of 3D thermal stresses of large-sized castings in solidification processes


    When heavy machines and large scaled receiver system of communication equipment are manufactured, it always needs to produce large- sized steel castings, aluminum castings and etc. Some defects of hot cracking by thermal stress often appear during solidification process as these castings are produced, which results in failure of castings.Therefore predicting the effects of technological parameters for production of castings on the thermal stress during solidification process becomes an important means. In this paper, the mathematical models have been established and numerical calculation of temperature fields by using finite difference method (FDM) and then thermal stress fields by using finite element method (FEM) during solidification process of castings have been carried out. The technological parameters of production have been optimized by the results of calculation and the defects of hot cracking have been eliminated. Modeling and simulation of 3D thermal stress during solidification processes of large-sized castings provided a scientific basis, which promoted further development of advanced manufacturing technique.

  16. The problem of the first return attached to a pseudodifferential operator in dimension 3

    Oscar F. Casas-Sánchez


    Full Text Available In this article we study the problem of first return associated to an elliptic pseudodifferential operator with non-radial symbol of dimension 3 over the p-adics. Resumen.El problema del primer retorno asociado a un operador seudodiferencial en dimensión 3 En este artículo estudiamos el problema del primer retorno asociado a un operador seudodiferencial elíptico con símbolo no radial de dimensión 3 sobre el cuerpo de los números pádicos.

  17. Solidification and crystal growth of solid solution semiconducting alloys

    Lehoczky, S.L.; Szofran, F.R.


    Problems associated with the solidification and crytal growth of solid-solution semiconducting alloy crystals in a terrestrial environment are described. A detailed description is given of the results for the growth of mercury cadmium telluride (HgCdTe) alloy crystals by directional solidification, because of their considerable technological importance. A series of HgCdTe alloy crystals are grown from pseudobinary melts by a vertical Bridgman method using a wide range of growth rates and thermal conditions. Precision measurements are performed to establish compositional profiles for the crystals. The compositional variations are related to compositional variations in the melts that can result from two-dimensional diffusion or density gradient driven flow effects ahead of the growth interface. These effects are discussed in terms of the alloy phase equilibrium properties, the recent high temperature thermophysical data for the alloys and the highly unusual heat transfer characteristics of the alloy/ampule/furnace system that may readily lead to double diffusive convective flows in a gravitational environment.

  18. Solidification and crystal growth of solid solution semiconducting alloys

    Lehoczky, S. L.; Szofran, F. R.


    Problems associated with the solidification and crytal growth of solid-solution semiconducting alloy crystals in a terrestrial environment are described. A detailed description is given of the results for the growth of mercury cadmium telluride (HgCdTe) alloy crystals by directional solidification, because of their considerable technological importance. A series of HgCdTe alloy crystals are grown from pseudobinary melts by a vertical Bridgman method using a wide range of growth rates and thermal conditions. Precision measurements are performed to establish compositional profiles for the crystals. The compositional variations are related to compositional variations in the melts that can result from two-dimensional diffusion or density gradient driven flow effects ahead of the growth interface. These effects are discussed in terms of the alloy phase equilibrium properties, the recent high temperature thermophysical data for the alloys and the highly unusual heat transfer characteristics of the alloy/ampule/furnace system that may readily lead to double diffusive convective flows in a gravitational environment.

  19. Solidification studies of automotive heat exchanger materials

    Carlberg, T.; Jaradeh, M.; Kamgou Kamaga, H.


    Modifications of the aluminum alloy AA 3003 have been studied to improve and tailorits properties for applications in automotive heat exchangers. Laboratory techniques have been applied to simulate industrial direct-chill casting, and some basic solidification studies have been conducted. The results are coupled to structures observed in industrial-size ingots and discussed in terms of structure-property relations.

  20. Detached Growth of Germanium by Directional Solidification

    Palosz, W.; Volz, M. P.; Cobb, S.; Motakef, S.; Szofran, F. R.


    The conditions of detached solidification under controlled pressure differential across the meniscus were investigated. Uncoated and graphite- or BN-coated silica and pBN crucibles were used. Detached and partly detached growth was achieved in pBN and BN-coated crucibles, respectively. The results of the experiments are discussed based on the theory of Duffar et al.

  1. Microstructure Development during Solidification of Aluminium Alloys

    Ruvalcaba Jimenez, D.G.


    This Thesis demonstrates studies on microstructure development during the solidification of aluminium alloys. New insights of structure development are presented here. Experimental techniques such as quenching and in-situ High-brilliance X-ray microscopy were utilized to study the microstructure evo

  2. PREFACE: MCWASP XIII: International Conference on Modeling of Casting, Welding and Advanced Solidification Processes

    Ludwig, Andreas


    Due to fast-paced development in computer technologies during the last three decades, computer-based process modeling has become an important tool for the improvement of existing process technologies and the development of new, innovative technologies. With the help of numerical process simulations, complex and costly experimental trials can now be reduced to a minimum. For metallurgical processes in particular, computer simulations are of outstanding importance, as the flow and solidification of molten alloys or the formation of microstructure and defects can hardly be observed experimentally. Corresponding computer simulations allow us inside views into the key process phenomena and so offer great potential for optimization. In 1980 the conference series 'Modeling of Casting, Welding and Advanced Solidification Processes (MCWASP)' was started up, and has now been continued by holding the 13th international conference on 'Modeling of Casting, Welding and Advanced Solidification Processes', MCWASP XIII, in Schladming, Austria, from June 17-22 2012. Around 200 scientists from industry and academia, coming from 20 countries around the globe attended 78 oral and 50 poster presentations on different aspects of solidification-related modeling topics. Besides process-related sessions such as (i) Ingot and Shape Casting, (ii) Continuous Casting and Direct Chill Casting, (iii) Directional Solidification and Zone Melting, (iv) Welding, and (v) Centrifugal Casting, a larger focus was put on (vi) Experimental Investigation and In-Situ Observations. In recent years, this topic has been significantly strengthened as advanced synchrotron technologies allow fantastic in-situ observations of phenomena happening inside small metallic samples. These observations will definitely serve as a benchmark for the modeling community. Further macroscopic aspects of advanced solidification science were tackled in the sessions (vii) Electromagnetic Coupling, (viii) Thermomechanics, (ix

  3. Identification of dust outbreaks on infrared MSG-SEVIRI data by using a Robust Satellite Technique (RST)

    Sannazzaro, Filomena; Filizzola, Carolina; Marchese, Francesco; Corrado, Rosita; Paciello, Rossana; Mazzeo, Giuseppe; Pergola, Nicola; Tramutoli, Valerio


    Dust storms are meteorological phenomena of great interest for scientific community because of their potential impact on climate changes, for the risk that may pose to human health and due to other issues as desertification processes and reduction of the agricultural production. Satellite remote sensing, thanks to global coverage, high frequency of observation and low cost data, may highly contribute in monitoring these phenomena, provided that proper detection methods are used. In this work, the known Robust Satellite Techniques (RST) multitemporal approach, used for studying and monitoring several natural/environmental hazards, is tested on some important dust events affecting Mediterranean region in May 2004 and Arabian Peninsula in February 2008. To perform this study, data provided by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) have been processed, comparing the generated dust maps to some independent satellite-based aerosol products. Outcomes of this work show that the RST technique can be profitably used for detecting dust outbreaks from space, providing information also about areas characterized by a different probability of dust presence. They encourage further improvements of this technique in view of its possible implementation in the framework of operational warning systems.

  4. LGBT tiesību pārstāvniecība Eiropas Savienībā

    Mūsiņa, Santa


    Bakalaura darbā „LGBT tiesību pārstāvniecība Eiropas Savienībā” galvenā uzmanība pievērsta LGBT interešu pārstāvībai ES, analizējot interešu grupu spēju īstenot LGBT lobija aktivitātes ES institucionālajā ietvarā. Pētījumā mēģināts noskaidrot, kāpēc LGBT organizācijām līdz šim nav izdevies panākt ES LGBT likumdošanas paplašināšanu, pievēršot uzmanību organizāciju lobija stratēģijām. Darba teorētiskā pieeja balstās uz lobija efektivitātes principiem, kurus adap...

  5. LGBT tiesību pārstāvniecība Eiropas Savienībā

    Mūsiņa, Santa


    Bakalaura darbā „LGBT tiesību pārstāvniecība Eiropas Savienībā” galvenā uzmanība pievērsta LGBT interešu pārstāvībai ES, analizējot interešu grupu spēju īstenot LGBT lobija aktivitātes ES institucionālajā ietvarā. Pētījumā mēģināts noskaidrot, kāpēc LGBT organizācijām līdz šim nav izdevies panākt ES LGBT likumdošanas paplašināšanu, pievēršot uzmanību organizāciju lobija stratēģijām. Darba teorētiskā pieeja balstās uz lobija efektivitātes principiem, kurus adap...

  6. An improved RST approach for timely alert and Near Real Time monitoring of oil spill disasters by using AVHRR data

    C. S. L. Grimaldi


    Full Text Available Information acquired and provided in Near Real Time is fundamental in contributing to reduce the impact of different sea pollution sources on the maritime environment. Optical data acquired by sensors aboard meteorological satellites, thanks to their high temporal resolution as well as to their delivery policy, can be profitably used for a Near Real Time sea monitoring, provided that accurate and reliable methodologies for analysis and investigation are designed, implemented and fully assessed.

    In this paper, the results achieved by the application of an improved version of RST (Robust Satellite Technique to oil spill detection and monitoring will be shown. In particular, thermal infrared data acquired by the NOAA-AVHRR (National Oceanic and Atmospheric Administration-Advanced Very High Resolution Radiometer have been analyzed and a new RST-based change detection index applied to the case of the oil spills that occurred off the Kuwait and Saudi Arabian coasts in January 1991 and during the Lebanon War in July 2006.

    The results obtained, even in comparison with those achieved by other AVHRR-based techniques, confirm the unique performance of the proposed approach in automatically detecting the presence of oil spill with a high level of reliability and sensitivity. Moreover, the potential of the extension of the proposed technique to sensors onboard geostationary satellites will be discussed within the context of oil spill monitoring systems, integrating products generated by high temporal (optical and high spatial (radar resolution satellite systems.

  7. Application of simplified model to sensitivity analysis of solidification process

    R. Szopa


    Full Text Available The sensitivity models of thermal processes proceeding in the system casting-mould-environment give the essential information concerning the influence of physical and technological parameters on a course of solidification. Knowledge of time-dependent sensitivity field is also very useful in a case of inverse problems numerical solution. The sensitivity models can be constructed using the direct approach, this means by differentiation of basic energy equations and boundary-initial conditions with respect to parameter considered. Unfortunately, the analytical form of equations and conditions obtained can be very complex both from the mathematical and numerical points of view. Then the other approach consisting in the application of differential quotient can be applied. In the paper the exact and approximate approaches to the modelling of sensitivity fields are discussed, the examples of computations are also shown.

  8. An evaluation of the relationship between Gray’s revised RST and Eysenck’s PEN: distinguishing BIS and FFFS in Carver and White’s BIS/BAS scales

    Heym, N; Ferguson, E; Lawrence, C.


    Recent revisions of Gray's Reinforcement Sensitivity Theory (RST) have important implications for self-report measures of approach and avoidance behaviours and how Gray's model relates to other personality models. In this paper, we examine the revised RST by comparing Carver and White's (1994) original one-factor solution of the BIS scale with two alternative two-factor solutions separating BIS-Anxiety and FFFS-Fear. We also examine the relationships between Eysenck's PEN and revised RST fact...

  9. Experimental Verification of Solidification Stress Theory

    Solbrig, C W; Morrison, M C; SImpson, M F; Bateman, K J


    A research program is being conducted to develop a crack-free ceramic waste form (CWF) to be used for long term encasement of fission products and actinides resulting from processing spent nuclear fuel. Cracking usually occurs in the cooldown phase of the glass or ceramic formations. A crack-free formation should have more resistance to leaching than one with many cracks. In the research leading up to producing a CWF, a model was developed that proposes a permanent stress develops when the melt solidifies and that this stress can cause failure as the CWF nears room temperature. This paper reports on how the formation, CWF2, confirms the existence of this stress. The solidification stress is in addition to and of opposite sign of the thermal stress. Its derivation is reported on in Ref. 1. Cracking of the CWF would occur at low temperatures if solidification stress exists but at high temperatures if it doesn’t. If solidification stress occurs, then the cooldown rate during solidification should be reduced. If not, it should be reduced when the thermal stresses are highest. Recording cracking sounds confirm the existence of this solidification stress since cracking occurred during the low temperature phase of the cooldown. As a side purpose of this paper, a cooldown rate is proposed that should eliminate cracking in the next experiment, CWF3. CWF2 is a prototype vertical ceramic waste cylinder formed over a period of 10 days by heating a mixture of 75% zeolite, 25% glass frit in an argon atmosphere furnace through melting to 925 C and then cooling through solidification to room temperature. It is approximately 1 m high, 0.5 m in diameter, weighs about 400 kg, and is formed in a stainless steel can 0.5 cm thick. This cylinder developed many cracks on cooldown. At least 15 loud cracks were recorded over a period of 4 days at the end of cooldown when the temperatures were below 400 C. The CWF2 surface and centerline temperatures at mid height were measured which

  10. Transport Phenomena During Equiaxed Solidification of Alloys

    Beckermann, C.; deGroh, H. C., III


    Recent progress in modeling of transport phenomena during dendritic alloy solidification is reviewed. Starting from the basic theorems of volume averaging, a general multiphase modeling framework is outlined. This framework allows for the incorporation of a variety of microscale phenomena in the macroscopic transport equations. For the case of diffusion dominated solidification, a simplified set of model equations is examined in detail and validated through comparisons with numerous experimental data for both columnar and equiaxed dendritic growth. This provides a critical assessment of the various model assumptions. Models that include melt flow and solid phase transport are also discussed, although their validation is still at an early stage. Several numerical results are presented that illustrate some of the profound effects of convective transport on the final compositional and structural characteristics of a solidified part. Important issues that deserve continuing attention are identified.

  11. Complex banded structures in directional solidification processes.

    Korzhenevskii, A L; Rozas, R E; Horbach, J


    A combination of theory and numerical simulation is used to investigate impurity superstructures that form in rapid directional solidification (RDS) processes in the presence of a temperature gradient and a pulling velocity with an oscillatory component. Based on a capillary wave model, we show that the RDS processes are associated with a rich morphology of banded structures, including frequency locking and the transition to chaos.

  12. Molecular dynamics modelling of solidification in metals

    Boercker, D.B.; Belak, J.; Glosli, J. [Lawrence Livermore National Lab., CA (United States)


    Molecular dynamics modeling is used to study the solidification of metals at high pressure and temperature. Constant pressure MD is applied to a simulation cell initially filled with both solid and molten metal. The solid/liquid interface is tracked as a function of time, and the data are used to estimate growth rates of crystallites at high pressure and temperature in Ta and Mg.

  13. Direct numerical simulation of solidification microstructures affected by fluid flow

    Juric, D.


    The effects of fluid flow on the solidification morphology of pure materials and solute microsegregation patterns of binary alloys are studied using a computational methodology based on a front tracking/finite difference method. A general single field formulation is presented for the full coupling of phase change, fluid flow, heat and solute transport. This formulation accounts for interfacial rejection/absorption of latent heat and solute, interfacial anisotropies, discontinuities in material properties between the liquid and solid phases, shrinkage/expansion upon solidification and motion and deformation of the solid. Numerical results are presented for the two dimensional dendritic solidification of pure succinonitrile and the solidification of globulitic grains of a plutonium-gallium alloy. For both problems, comparisons are made between solidification without fluid flow and solidification within a shear flow.

  14. Study on undercooling of metal droplet in rapid solidification

    GAO; Yulai; GUAN; Wanbing; ZHAI; Qijie; XU; Kuangdi


    A mathematical model for the undercooling of the metal droplet during the rapid solidification is established, by which the factors that influence the undercooling of the metal droplet during the rapid solidification are analyzed, and the parameter ζ=σSL3/ (TLΔH 2 ) is defined as the impact factor of the undercooling for the droplet solidification. Different undercoolings of droplets induced by various rapid solidification conditions are mainly ascribed to the change of the impact factor. Moreover, it is shown that the larger of ζ, the higher the relative undercooling can be gained. Meanwhile, the parameters such as solid-liquid interfacial energy σSL and latent heat of solidification ΔH also vary with the rapid solidification conditions of droplets.

  15. Shape of growth cells in directional solidification.

    Pocheau, A; Georgelin, M


    The purpose of this study is to characterize experimentally the whole shape of the growth cells displayed in directional solidification and its evolution with respect to control parameters. A library of cells is first built up from observation of directional solidification of a succinonitrile alloy in a large range of pulling velocity, cell spacing, and thermal gradient. Cell boundaries are then extracted from these images and fitted by trial functions on their whole profile, from cell tip to cell grooves. A coherent evolution of the fit parameters with the control parameters is evidenced. It enables us to characterize the whole cell shape by a single function involving only two parameters which vary smoothly in the control parameter space. This, in particular, evidences a continuous evolution of the cell geometry at the cell to dendrite transition which denies the existence of a change of branch of solutions at the occurrence of sidebranching. More generally, this global determination of cell shape complemented with a previous determination of the position of cells in the thermal field (the cell tip undercooling) provides a complete characterization of growth solutions and of their evolutions in this system. It thus brings about a relevant framework for testing and improving theoretical and numerical understanding of cell shapes and cell stability in directional solidification.

  16. The study of ctx B and rstR variations of toxigenic Vibrio cholerae O1 E1 Tor strains isolated from 1961 to 2010 in China



    Objective To understand the ctx B and rstR variations of toxigenic Vibrio cholerae(V.cholerae)O1 E1 Tor strains isolated from different provinces in China from1961 to 2010.Methods All 385 toxigenic V.cholerae O1 E1 Tor strains were selected,which were isolated in China between year 1961 and 2010.ctx B gene was amplified by PCR method and sequenced for further analysis.rstR was detected with PCR by using the genotype

  17. Analysis of solidification and melting of Pcm with energy generation

    Jiji, Latif M. [Department of Mechanical Engineering, The City College of the City University of New York, New York, NY 10031 (United States); Gaye, Salif [Ecole Superieure Polytechnique, Enseignant a l' ESP BP A10, Universite Cheikh Anta Diop, Thies (Senegal)


    One-dimensional solidification and melting of a slab with uniform volumetric energy generation is examined analytically. A sudden change in surface temperature triggers phase transformation and interface motion. Analytic solutions are obtained using a quasi-steady approximation. Unlike solidification, the melting case is characterized by a pure liquid phase and a mixture of solid and liquid at the fusion temperature. The solution is governed by a single energy generation parameter. Temperature profiles, interface location and steady state conditions are presented for solidification and melting. Results are applied to two examples: solidification of a nuclear material and melting of ice. [Author].

  18. A Numerical Study of Directional Solidification and Melting in Microgravity

    Chen, P. Y. P.; Timchenko, V.; Leonardi E.; deVahlDavis, G.; deGroh, H. C., III


    A computational model is presented for the study of the solidification and melting of a pure substance and of a binary alloy. The enthalpy method has been used, and incorporated into a commercial CFD code. Three examples of the use of the model are described: the three-dimensional solidification of a pure substance (succinonitrile), the results of which are compared with experiment; an example of the solidification of a bismuth-tin alloy; and a simulation of a solidification and melting experiment done in space known as the MEPHISTO program.

  19. Effect of solidification rate on competitive grain growth in directional solidification of a nickel-base superalloy

    ZHOU YiZhou; SUN XiaoFeng


    The mechanism of grain structure evolution during directional solidification is a fundamental subject in material science.Within the published research there exist conflicting views on the mechanism of grain overgrowth.To study the effect of solidification rate on grain structure evolution,bi-crystals samples were produced in a nickel-base superalloy at different solidification rates.It was found that at the convergent grain boundaries those grains better aligned with respect to the heat flux more readily overgrew neighbouring grains with misaligned orientations and the effect became more pronounced as solidification rate was increased.However,at diverging grain boundaries the rate of overgrowth was invariant to the solidification rate.These experimental results were compared with models in the literature.Thus,a better insight into competitive grain growth in directional solidification processes was obtained.

  20. Effects of the location of a cast in the furnace on flatness of the solidification front in directional solidification

    Lian, Yuanyuan; Li, Dichen; Zhang, Kai


    Many defects of single crystals are caused by the nonplanar solidification front. The transverse temperature gradient at melt-crystal interface results in nonplanar solidification fronts. The location of a cast in the directional solidification furnace affects heat dissipation and thus influences the transverse temperature gradient. This paper presents a criterion and a searching algorithm to find the optimal location of the cast for flattening the solidification front. A numerical simulation was employed for the verification of our method. Additionally, the effects of the size of the cooling device of the furnace on the optimal location, the transverse temperature gradient and the solidification time were discussed. The transverse temperature gradient is reduced about 50% without increasing much solidification time when setting the cast with a varying thickness mould at the optimal location. In addition, the optimal location is mainly influenced by the radius of the cooling ring.

  1. Thermal and structural studies about the solidification process of grey cast irons; Estudio termico y estructural del proceso de solidificacion de funciones de hierro con grafito laminar

    Larranaga, P.; Sertucha, J.


    The grey iron casting manufacture is an industrial process extendly used today. Therefore, the study of the solidification features obtained from this iron and the factors that have influence on such transition becomes a powerful tool in order to support the technological development of this type of material. In the present work, three inoculated alloys with different chemical compositions (hypo eutectic, eutectic and hyper eutectic) have been selected so as to comparatively analyse the structural characteristics of the irons during the liquid-solid transformation. The behaviour of the samples has been controlled recording the cooling curves and then they have been quenched in order to study the structural characteristics at different stages of the solidification. The selected alloys show different solidification features as a function of the chemical composition and the corresponding nucleation potential. The obtained results have been discussed in terms of a comparative analysis, establishing a solidification model that explains the industrial behaviour of the alloys. (Author)

  2. Online process control for directional solidification by ultrasonic pulse echo technique.

    Drevermann, A; Pickmann, C; Tiefers, R; Zimmermann, G


    A method of controlling the actual growth velocity during directional solidification based on ultrasound has been developed. For this purpose a pulse echo technique is used to measure the actual solidification rate online. This quantity is used to control the furnace velocity. Solidification experiments with metallic alloys and constant furnace velocity often result in non-steady actual solidification rates. Experiments carried out with online process control demonstrate that a really steady-state solidification with a constant solidification rate is achieved.

  3. Radiation heat transfer model for complex superalloy turbine blade in directional solidification process based on finite element method

    Dun-ming Liao


    Full Text Available For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification (DS process, a radiation heat transfer model based on the Finite Element Method (FEM is developed in this study. Key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also stated. In order to analyze the effect of withdrawing rate on DS process, the solidification processes of a complex superalloy turbine blade in the High Rate Solidification (HRS process with different withdrawing rates are simulated; and by comparing the simulation results, it is found that the most suitable withdrawing rate is determined to be 5.0 mm昺in-1. Finally, the accuracy and reliability of the radiation heat transfer model are verified, because of the accordance of simulation results with practical process.

  4. Prediction of solidification and phase transformation in weld metals for welding of high performance stainless steels; Kotaishoku kotainetsu stainless koyo yosetsu kinzoku no gyoko hentai no yosoku gijutsu

    Koseki, T.; Inoue, H.; Morimoto, H.; Okita, S. [Nippon Steel Corp., Tokyo (Japan)


    Prediction technology is introduced on the solidification and transformation of weld metals used for high performance stainless steel. A model has been developed which uses Thermo Calc, a multiple balanced calculation program, as a means to analyze the solidification of multi-component alloys including the polyphase solidification such as eutectic and peritectic. Verification has been in progress concerning the adequacy of this model and the adaptability as a practical steel. The following are the prediction technologies for solidification and transformation which have been derived from experiments and applied to welding techniques: the effects of nitrogen on the solidification mode and residual {gamma}quantity of a welding metal that is required for controlling the welding/solidification of high nitrogen content {gamma}system stainless steel; the structural control of weld metal for high corrosion resistance high Mo stainless steel, in which high Ni and high Mo contents are indispensable for attaining the optimum structure; the structural control of weld metal for two-phase stainless steel containing Mo and N, in which it is essential to secure a high nitrogen content and a {delta}/{gamma}phase balance in a weld metal; and the precipitation prediction of intermetallic compound in a high alloy weld metal for a high alloy stainless steel, for which an explanation is there by Cieslak et al. based on the phase stability theory. 22 refs., 16 figs.

  5. Undercooling, Rapid Solidification, and Relations to Processing in Low Earth Orbit (A Review of the Works of Bingbo Wei)

    deGroh, Henry C., III


    This is a survey of the published works of Prof. Bingbo Wei of the Department of Applied Physics at Northwestern Polytechnical University, Xian P.R. China. Transformations among solid - liquid - and vapor are fundamental to the foundations of life and culture on Earth. The development and understanding of materials has lead the evolution and advancement of the human race since antiquity. Materials and fluids research is continuing today, with us standing on the shoulders of those that have gone before us. Technological and scientific breakthroughs continue due to studies of greater and greater complexity, that include for example, research done at high pressures, in high magnetic fields, at temperatures near absolute zero, and in the low gravity environment of low Earth orbit. Of particular technological importance is the liquid to solid transformation of metals and alloys. Solidification processing is generally the most important factor in the final properties of objects made of metal; and undercooling is the fundamental driving force for all solidification. The interest and resources dedicated to the study of solidification and undercooling are great and World wide. For many years B. Wei and his coworkers have been studying undercooling and rapid solidification and have amassed a significant body of published research in this important field, contributing to the leading edge of the state-of-the-art. It is the goal of this memorandum to provide a review of the research of B. Wei et al.; publications in Chinese are included in the reference list but are not discussed. The bulk of Wei's work has been in the area of undercooling and rapid solidification [1-11, 13-16, 24-36] with papers dating back to 1989, the same year he earned his Ph.D. Below, discussions of Wei's undercooling and rapid solidification research have been grouped together mostly on the basis of alloy type, such as eutectic, intermetallic, or monotectic.

  6. Forming Conditions and Neural Network Control of Continuously Directional Microstructure in Directional Solidification Continuous Casting Process


    Directional solidification continuous casting (DSCC) process is a new manufacturing technology for metal- lic materials which combines advantages of both directional solidification technology and continuous casting technolo- gy. Unlimited long shaped metal with directionally solidifying microstructure can be produced by this process. It is experimentally shown that controlling condition of stable and continuous growth of single crystal structure means the precise control of the location of the S/L interface, which is affected and determined by seven process parameters. Moreover, these parameters are also interacted each other, so the disturbance of any parameters may cause the fail- ure of controlling of S/L interface. In this paper, on the basis of analyzing the forming conditions of continuously di- rectional microstructures in DSCC process, the control model of DSCC procedure by neural network control (NNC) method was proposed and discussed. Combining with the experiments, we first used the computer to simulate the effects of the solidification parameters on destination control variable (S/L interface) and the interactions among these parameters during DSCC procedure. Secondly many training samples necessary for neural network calculation can be obtained through the simulation. Moreover, these samples are inputted into neural network software (NNs) and trained, then the control model can be built up.

  7. Effect of temperature field on solidification structure of pure Al under pulse magneto-oscillation

    Li Bo


    Full Text Available This article discusses the effect of temperature field on the Pulse Magneto-Oscillation (PMO induced solidification refinement of pure aluminium to provide more information for the industrial application of the PMO solidification technology. The temperature field is altered mainly by applied variable cooling conditions and pulse parameters. Experimental results show that the refinement effect in the case of full sand mould applied is weakened with the decreasing of cooling rate, however, in the alternative case, the sand mould whose sand bottom was replaced by a graphite block is favorable to the survival of equiaxed nucleus. The refinement mechanism is discussed in terms of the relationship between temperature field and the formation process of solidified structure. The formation or survival of nucleus depends on both temperature field and Joule heat produced by PMO, both low pulse frequency and high pulse current were experimentally confirmed to be effective; and PMO was demonstrated high potential in industrial application.

  8. Continuous melting and directional solidification of silicon ingot with an electromagnetic cold crucible

    Huang Feng


    Full Text Available In order to avoid contamination from the crucible and to modify the structures, a new solidification method based on cold crucible technology was used to prepare silicon ingots. A silicon ingot with square cross section was directionally solidified with a cold crucible. The mechanism of the cold crucible directional solidification of silicon ingot was revealed. Due to the induction heat that was released in the surface layer and the incomplete contact between the crucible and the melt, the lateral heat loss was reduced and the silicon ingot was directionally solidified. The structures, dislocation defects and the grain growth orientation of the ingot were determined. The results show that neither intergranular nor intragranular precipitates are found in the ingot, except for the top part that was the last to solidify. The average dislocation density is about 1 to 2 × 106 cm-2. The grains are preferentially orientated.

  9. Pattern and phase selection of peritectic reaction during directional solidification

    HUANG; Weidong; (黄卫东); LIN; Xin; (林鑫); WANG; Meng; (王猛); SHEN; Shujuan; (沈淑娟); SU; Yunpeng; (苏云鹏); LIU; Zhenxia; (刘振侠)


    Based on the growth competition between different pattern and phases, the pattern and phase selection during peritectic solidification is analysed by applying the maximum interface temperature criterion to the interface response functions calculated from a numerical model for single phase solidification. The theoretical results agree very well with the experimental results published in literature.

  10. A Computer Aided System for Simulating Weld Metal Solidification Crack


    A computer-aided system for simulating weld solidification crack has been developed by which a welding engineer can carry out the welding solidification crack simulation on the basis of a commercial finite element analysis software package. Its main functions include calculating the heat generations of the moving arc, mesh generation, calculating stress-strain distributions with element rebirth technique.

  11. [Solidification of volatile oil with graphene oxide].

    Yan, Hong-Mei; Jia, Xiao-Bin; Zhang, Zhen-Hai; Sun, E; Xu, Yi-Hao


    To evaluate the properties of solidifying volatile oil with graphene oxide, clove oil and zedoary turmeric oil were solidified by graphene oxide. The amount of graphene oxide was optimized with the eugenol yield and curcumol yield as criteria. Curing powder was characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The effects of graphene oxide on dissolution in vitro and thermal stability of active components were studied. The optimum solidification ratio of graphene oxide to volatile oil was 1:1. Dissolution rate of active components had rare influence while their thermal stability improved after volatile oil was solidified. Solidifying herbal volatile oil with graphene oxide deserves further study.

  12. Seaweed to dendrite transition in directional solidification.

    Provatas, Nikolas; Wang, Quanyong; Haataja, Mikko; Grant, Martin


    We simulate directional solidification using a phase-field model solved with adaptive mesh refinement. For small surface tension anisotropy directed at 45 degrees relative to the pulling direction we observe a crossover from a seaweed to a dendritic morphology as the thermal gradient is lowered, consistent with recent experimental findings. We show that the morphology of crystal structures can be unambiguously characterized through the local interface velocity distribution. We derive semiempirically an estimate for the crossover from seaweed to dendrite as a function of thermal gradient and pulling speed.

  13. Low Melt Height Solidification of Superalloys

    Montakhab, Mehdi; Bacak, Mert; Balikci, Ercan


    Effect of a reduced melt height in the directional solidification of a superalloy has been investigated by two methods: vertical Bridgman (VB) and vertical Bridgman with a submerged baffle (VBSB). The latter is a relatively new technique and provides a reduced melt height ahead of the solidifying interface. A low melt height leads to a larger primary dendrite arm spacing but a lower mushy length, melt-back transition length, and porosity. The VBSB technique yields up to 38 pct reduction in the porosity. This may improve a component's mechanical strength especially in a creep-fatigue type dynamic loading.

  14. Novel Directional Solidification of Hypermonotectic Alloys

    Grugel, R. N.; Fedoseyev, A. I.; Rose, M. Franklin (Technical Monitor)


    There are many metal alloy systems that separate into two different liquids upon cooling from a higher temperature. Uniform microstructural development during solidification of these immiscible liquids on Earth is hampered by inherent density differences between the phases. Microgravity processing minimizes settling but segregation still occurs due to gravity independent wetting and coalescence phenomena. Experiments with the transparent organic, metal analogue, succinonitrile-glycerol system were conducted in conjunction with applied ultrasonic energy. The processing parameters associated with this technique have been evaluated in view of optimizing dispersion uniformity. Characterization of the experimental results in terms of an initial modeling effort will also be presented.

  15. Alternating tip splitting in directional solidification.

    Utter, B; Ragnarsson, R; Bodenschatz, E


    We report experimental results on the tip splitting dynamics of seaweed growth in directional solidification of succinonitrile alloys. Despite the random appearance of the growth, a tip splitting morphology was observed in which the tip alternately splits to the left and to the right. The tip splitting frequency f was found to be related to the growth velocity V as a power law f~V1.5. This finding is consistent with the predictions of a tip splitting model that is also presented. Small anisotropies are shown to lead to different kinds of seaweed morphologies.

  16. ORNL liquid low-level waste solidification

    Schultz, R.M.; Monk, T.H.; du Mont, S.P.; Helms, R.E.; Keigan, M.V.; Morris, M.I.


    The solidification of LLLW at ORNL has developed two basic strategies, a near-term or backup flowsheet is planned to alleviate the immediate capacity problem for storage of concentrated LLLW and a long-term or reference flowsheet is planned to incorporate filtration of the settleable TRU and cesium and strontium decontamination of the LLLW. Presently a feasibility study is evaluating the process alternatives for segregating LLLW from remote-handled transuranic (RH-TRU) sludges, decontamination of the LLLW for beta-gamma radionuclides such as cesium and strontium, and the handling and storage of the RH-TRU sludges and decontamination media. 14 refs.

  17. Melt Flow Control in the Directional Solidification of Binary Alloys

    Zabaras, Nicholas


    Our main project objectives are to develop computational techniques based on inverse problem theory that can be used to design directional solidification processes that lead to desired temperature gradient and growth conditions at the freezing front at various levels of gravity. It is known that control of these conditions plays a significant role in the selection of the form and scale of the obtained solidification microstructures. Emphasis is given on the control of the effects of various melt flow mechanisms on the local to the solidification front conditions. The thermal boundary conditions (furnace design) as well as the magnitude and direction of an externally applied magnetic field are the main design variables. We will highlight computational design models for sharp front solidification models and briefly discuss work in progress toward the development of design techniques for multi-phase volume-averaging based solidification models.

  18. Nanoparticle-induced unusual melting and solidification behaviours of metals

    Ma, Chao; Chen, Lianyi; Cao, Chezheng; Li, Xiaochun


    Effective control of melting and solidification behaviours of materials is significant for numerous applications. It has been a long-standing challenge to increase the melted zone (MZ) depth while shrinking the heat-affected zone (HAZ) size during local melting and solidification of materials. In this paper, nanoparticle-induced unusual melting and solidification behaviours of metals are reported that effectively solve this long-time dilemma. By introduction of Al2O3 nanoparticles, the MZ depth of Ni is increased by 68%, while the corresponding HAZ size is decreased by 67% in laser melting at a pulse energy of 0.18 mJ. The addition of SiC nanoparticles shows similar results. The discovery of the unusual melting and solidification of materials that contain nanoparticles will not only have impacts on existing melting and solidification manufacturing processes, such as laser welding and additive manufacturing, but also on other applications such as pharmaceutical processing and energy storage.

  19. [Comparison of fixation effects of heavy metals between cement rotary kiln co-processing and cement solidification/stabilization].

    Zhang, Jun-li; Liu, Jian-guo; Li, Cheng; Jin, Yi-ying; Nie, Yong-feng


    Both cement rotary kiln co-processing hazardous wastes and cement solidification/stabilization could dispose heavy metals by fixation. Different fixation mechanisms lead to different fixation effects. The same amount of heavy metal compounds containing As, Cd, Cr, Cu, Pb, Zn were treated by the two kinds of fixation technologies. GB leaching test, TCLP tests and sequential extraction procedures were employed to compare the fixation effects of two fixation technologies. The leached concentration and chemical species distribution of heavy metals in two grounded mortar samples were analyzed and the fixation effects of two kinds of technologies to different heavy metals were compared. The results show the fixation effect of cement rotary kiln co-processing technology is better than cement solidification/stabilization technology to As, Pb, Zn. Calcinations in cement rotary kiln and then hydration help As, Pb, Zn contained in hazardous wastes transform to more steady chemical species and effectively dispose these heavy metals compounds. Cr3+ is liable to be converted to much more toxic and more mobile Cr6+ state in cement rotary kiln. And so Cr wastes are more fit for treatment by cement solidification/stabilization technology. The work could provide a basis when choosing disposal technologies for different heavy metals and be helpful to improve the application and development of cement rotary kiln co-processing hazardous wastes.

  20. Built-in mechanisation of vertical layers at the Mina la Camocha by utilising the mechanised complex Asturfalia RST3. Final report; Mecanizacion integral de capas verticales en Mina la Camocha mediante el complejo mecanizado asturfalia RST3. Informe final



    In the coal field located in the Cuenca Central Asturiana, a coal deposit characterised by narrow vertical layers, and where several geological changes are occurring, is being worked on. In 58% of the reservoirs there are dips of more than 60 degrees. Since the end of the seventies, research work has been done in Asturia, with the aim to find the best working system by utilising an integrally mechanised system on such layers. At the Mina la Camocha, the first tests performed by using an integrally mechanised system began in 1986 and went on with good results in the working of different kinds of layers. As soon as what needed to be studied in order to be improved was worked out, the project and the production of the new appliance RST3, was carried out. It was tested on layer 14 at the Mina la Camocha, as illustrated in the present report. This report describes the equipment utilised, and offers analyses of the workshop progress and of the results obtained. Finally, the conclusions include different aspects of the installation, as well as both the functioning of the appliance itself and its practical applications.

  1. The melting and solidification of nanowires

    Florio, B. J.; Myers, T. G.


    A mathematical model is developed to describe the melting of nanowires. The first section of the paper deals with a standard theoretical situation, where the wire melts due to a fixed boundary temperature. This analysis allows us to compare with existing results for the phase change of nanospheres. The equivalent solidification problem is also examined. This shows that solidification is a faster process than melting; this is because the energy transfer occurs primarily through the solid rather than the liquid which is a poorer conductor of heat. This effect competes with the energy required to create new solid surface which acts to slow down the process, but overall conduction dominates. In the second section, we consider a more physically realistic boundary condition, where the phase change occurs due to a heat flux from surrounding material. This removes the singularity in initial melt velocity predicted in previous models of nanoparticle melting. It is shown that even with the highest possible flux the melting time is significantly slower than with a fixed boundary temperature condition.

  2. The Advanced Automated Directional Solidification Furnace

    Gillies, D. C.; Reeves, F. A.; Jeter, L. B.; Sledd, J. D.; Cole, J. M.; Lehoczky, S. L.


    The Advanced Automated Directional Solidification Furnace (AADSF) is a five zone tubular furnace designed for Bridgman-Stockbarger, other techniques of crystal growth involving multiple temperature zones such as vapor transport experiments and other materials science experiments. The five zones are primarily designed to produce uniform hot and cold temperature regions separated by an adiabatic region constructed of a heat extraction plate and an insert to reduce radiation from the hot to the cold zone. The hot and cold zone temperatures are designed to reach 1600 C and 1100 C, respectively. AADSF operates on a Multi-Purpose Experiment Support Structure (MPESS) within the cargo bay of the Space Shuttle on the United States Microgravity Payload (USMP) missions. Two successful flights, both employing the directional solidification or Bridgman Stockbarger technique for crystal growth have been made, and crystals of HgCdTe and PbSnTe grown in microgravity have been produced on USMP-2 and USMP-3, respectively. The addition of a Sample Exchange Mechanism (SEM) will enable three different samples to be processed on future flights including the USMP-4 mission.

  3. Carburizer Effect on Cast Iron Solidification

    Janerka, Krzysztof; Kondracki, Marcin; Jezierski, Jan; Szajnar, Jan; Stawarz, Marcin


    This paper presents the effect of carburizing materials on cast iron solidification and crystallization. The studies consisted of cast iron preparation from steel scrap and different carburizers. For a comparison, pig iron was exclusively used in a solid charge. Crystallization analysis revealed the influence of the carburizer material on the crystallization curves as well as differences in the solidification paths of cast iron prepared with the use of different charge materials. The carburizers' influence on undercooling during the eutectic crystallization process was analyzed. The lowest undercooling rate was recorded for the melt with pig iron, then for synthetic graphite, natural graphite, anthracite, and petroleum coke (the highest undercooling rate). So a hypothesis was formulated that eutectic cells are created most effectively with the presence of carbon from pig iron (the highest nucleation potential), and then for the graphite materials (crystallographic similarity with the carbon precipitation in the cast iron). The most difficult eutectic crystallization is for anthracite and petroleum coke (higher undercooling is necessary). This knowledge can be crucial when the foundry plant is going to change the solid charge composition replacing the pig iron by steel scrap and the recarburization process.

  4. Solidification microstructure of centrifugally cast Inconel 625

    Silvia Barella


    Full Text Available Centrifugal casting is a foundry process allowing the production of near net-shaped axially symmetrical components. The present study focuses on the microstructural characterization of centrifugally cast alloys featuring different chemical compositions for the construction of spheres applied in valves made of alloy IN625 for operation at high pressure. Control of the solidification microstructure is needed to assure the reliability of the castings. Actually, a Ni-base superalloy such as this one should have an outstanding combination of mechanical properties, high temperature stability and corrosion resistance. Alloys such as IN625 are characterised by a large amount of alloying elements and a wide solidification range, so they can be affected by micro-porosity defects, related to the shrinkage difference between the matrix and the secondary reinforcing phases (Nb-rich carbides and Laves phase. In this study, the microstructure characterization was performed as a function of the applied heat treatments and it was coupled with a calorimetric analysis in order to understand the mechanism ruling the formation of micro-porosities that can assure alloy soundness. The obtained results show that the presence of micro-porosities is governed by morphology and by the size of the secondary phases, and the presence of the observed secondary phases is detrimental to corrosion resistance.

  5. Inversion Solidification Cladding of H90-Steel

    LI Bao-mian; XU Guang-ming; CUI Jian-zhong


    The variation law of cladding thickness as well as the structures and properties of H90-steel clad strip produced by inversion solidification was studied.The interface bonding mechanisms were approached.It is found that the thickness of H90 cladding goes sequentially through the solidification growth stage,holding stage,and remelting stage,with an increase in immersion time.The higher the preheating temperature of the steel coil,the thicker is the maximum cladding thickness.Observation by using optical microscopy (OM) and the electron probe microanalyzer (EPMA) shows that the microstrueture of H90 cladding is composed of equiaxed grains,and that interdiffusion between Cu and Fe at interface occurs but obvious diffusion of Zn and the intermetallic layer are not observed.The diffusion layer is thin and about 4 μm.Multipass small reduction cold rolling and repeated bending tests show that the interface is firmly bonded.Tensile test shows that the mechanical properties of the as-clad strips can meet the requirements of GB5213-2001 for the F-grade deep-drawing steel plate though there is a slight difference in the mechanical properties among the clad strips with different cladding thickness.

  6. Numerical Simulation of Transport Phenomena in Solidification of Multicomponent Ingot Using a Continuum Model


    A continuum model proposed for dendrite solidification of multicomponent alloys, with any partial solid back diffusion, was used to numerically simulate the macroscopic solidification transport phenomena and macrosegregations in an upwards directionally solidified plain carbon steel ingot. The computational results of each macroscopic field of the physical variables involved in the solidification process at a middle solidification stage were presented.

  7. 模辊式生物质燃料成型技术及设备的研究进展%Research Progress of Biomass Pellet Fuel Solidification Technology and Equipment

    郝玲; 祖宇; 董良杰


    从模辊式生物质燃料成型技术的起源、设备类型与特点以及影响因素、成型机理、设备和关键部件的研究现状等方面进行了总结,分析了模辊式生物质燃料成型技术与设备的发展潜力、遇到的问题及研究成果,并对今后研究方向及设备结构的优化提出了看法.%With the summary of these aspects which are the origin of the mould and roller biomass fuel forming technology, types and characteristics of the equipment and the research status of its influence factors, formation mechanism, equipment and key components, this paper analyzed the development potential of the mould and roller biomass fuel forming technology and equipment, problems and results in the research, and gave suggestions of the future direction in research and the optimization of equipment.

  8. Solidification science in cast MMCs: The influence of merton flemings

    Rohatgi, Pradeep; Asthana, Rajiv


    The solidification science of cast metalmatrix composites (MMC) evolved as a subset of the broad field of solidification of monolithic alloys pioneered by Merton Flemings and his students. As a result of advances in solidification, the cast MMC field has evolved from its early incarnation—employing empirical research to engineer novel materials using versatile and cost-effective casting techniques—to using solidification-science-based approaches to tailor advanced materials for application-specific needs. The current and emerging applications of cast MMCs in a variety of automotive, aerospace, electronic packaging, and consumer-good industries exemplify the maturity of the field and the materials. Innovations in composite-forming techniques and efforts at wider industrial acceptance of MMCs will undoubtedly continue. However, the scientific principles underlying the solidification microstructure evolution that governs the composite properties have become well established, to a great extent, due to Flemings’ early, pioneering work on monolithic alloys and some of his more recent studies on solidification of reinforced metals. This paper reviews some aspects of solidification of discontinuously reinforced cast metals that owe their current understanding to Flemings’ contributions, in particular, the scientific understanding of macro- and microsegregation, fluidity and rheology of multiphase slurries, and stircasting, semi-solid casting, and preform infiltration. Current research to develop and test prototype components made from cast composites, including Al-flyash, Cu-graphite, Al-graphite, Al-alumina, and SiC-Al, is also presented, along with directions for future research.

  9. Structures Self-Assembled Through Directional Solidification

    Dynys, Frederick W.; Sayir, Ali


    Nanotechnology has created a demand for new fabrication methods with an emphasis on simple, low-cost techniques. Directional solidification of eutectics (DSE) is an unconventional approach in comparison to low-temperature biomimetic approaches. A technical challenge for DSE is producing microstructural architectures on the nanometer scale. In both processes, the driving force is the minimization of Gibb's free energy. Selfassembly by biomimetic approaches depends on weak interaction forces between organic molecules to define the architectural structure. The architectural structure for solidification depends on strong chemical bonding between atoms. Constituents partition into atomic-level arrangements at the liquid-solid interface to form polyphase structures, and this atomic-level arrangement at the liquid-solid interface is controlled by atomic diffusion and total undercooling due to composition (diffusion), kinetics, and curvature of the boundary phases. Judicious selection of the materials system and control of the total undercooling are the keys to producing structures on the nanometer scale. The silicon-titanium silicide (Si-TiSi2) eutectic forms a rod structure under isothermal cooling conditions. At the NASA Glenn Research Center, directional solidification was employed along with a thermal gradient to promote uniform rods oriented with the thermal gradient. The preceding photomicrograph shows the typical transverse microstructure of a solidified Si-TiSi2 eutectic composition. The dark and light gray regions are Si and TiSi2, respectively. Preferred rod orientation along the thermal gradient was poor. The ordered TiSi2 rods have a narrow distribution in diameter of 2 to 3 m, as shown. The rod diameter showed a weak dependence on process conditions. Anisotropic etch behavior between different phases provides the opportunity to fabricate structures with high aspect ratios. The photomicrographs show the resulting microstructure after a wet chemical etch and a

  10. Localized microstructures induced by fluid flow in directional solidification.

    Jamgotchian, H; Bergeon, N; Benielli, D; Voge, P; Billia, B; Guérin, R


    The dynamical process of microstructure localization by multiscale interaction between instabilities is uncovered in directional solidification of transparent alloy. As predicted by Chen and Davis, morphological instability of the interface is observed at inward flow-stagnation regions of the cellular convective field. Depending on the driving force of fluid flow, focus-type and honeycomb-type localized patterns form in the initial transient of solidification, that then evolves with time. In the case of solute-driven flow, the analysis of the onset of thermosolutal convection in initial transient of solidification enables a complete understanding of the dynamics and of the localization of morphological instability.

  11. Capillary-wave description of rapid directional solidification.

    Korzhenevskii, Alexander L; Bausch, Richard; Schmitz, Rudi


    A recently introduced capillary-wave description of binary-alloy solidification is generalized to include the procedure of directional solidification. For a class of model systems a universal dispersion relation of the unstable eigenmodes of a planar steady-state solidification front is derived, which readjusts previously known stability considerations. We moreover establish a differential equation for oscillatory motions of a planar interface that offers a limit-cycle scenario for the formation of solute bands and, taking into account the Mullins-Sekerka instability, of banded structures.

  12. Inverse thermal analysis method to study solidification in cast iron

    Dioszegi, Atilla; Hattel, Jesper


    Solidification modelling of cast metals is widely used to predict final properties in cast components. Accurate models necessitate good knowledge of the solidification behaviour. The present study includes a re-examination of the Fourier thermal analysis method. This involves an inverse numerical...... solution of a 1-dimensional heat transfer problem connected to solidification of cast alloys. In the analysis, the relation between the thermal state and the fraction solid of the metal is evaluated by a numerical method. This method contains an iteration algorithm controlled by an under relaxation term...... inverse thermal analysis was tested on both experimental and simulated data....

  13. Simulation of continuous cast steel product solidification

    Ardelean, E.


    Full Text Available Primary cooling – inside the tundish – has a great impact over the thickness of the solidified steel crust. If on exiting the tundish the crust is too thin, it can punch and break, as a result of the ferrostatic pressure exerted from the inside by the liquid steel as well as because of the weight of the molten steel. The parameters that influence the amount of dissipated heat depend on the cooling water flow of the tundish, on the pressure and temperature of the cooling water but also on the overheating of the continuously cast steel. The secondary cooling takes place at the exit of the semi-finished product from the tundish, when the solidification is supposed to take place all along the cross section of the strand. In order to achieve it, in addition to a correctly managed primary cooling, it is necessary to obtain the proper correlation of the factors that influence the secondary cooling as well: the water flow rate long the three zones of the installation and its pressure in the secondary circuit. All these have in view a proper solidification length; an intense cooling can generate cracks due to the thermal stress, while a too slow cooling can generate a partial solidification of the strand up to the cropping machine area. The paper presents a mathematical simulation of the continuously cast steel solidification.

    El enfriamiento primario del cristalizador tiene una gran importancia sobre el espesor de la costra de acero solidificado. Si al salir del cristalizador, esta costra es demasiado sutil, bajo la acción de la presión ferro estática ejercitada por el acero líquido del interior y gracias el peso propio del hilo, ésta, puede perforar resultando su rompimiento. Los parámetros que influenyen sobre la cantidad de calor cedida dependen del agua de enfriamiento del catalizador, de la presión y de la temperatura de agua de enfriamiento, pero también del sobrecalentamiento del acero fundido continuamente. A la salida del

  14. Convection and morphological stability during directional solidification

    Coriell, Sam R.; Chernov, A. A.; Murray, Bruce T.; Mcfadden, G. B.


    For growth of a vicinal face at constant velocity, the effect of anisotropic interface kinetics on morphological stability is calculated for a binary alloy. The dependence of the interface kinetic coefficient on crystallographic orientation is based on the motion and density of steps. Anisotropic kinetics give rise to traveling waves along the crystal-melt interface, and can lead to a significant enhancement of morphological stability. The stability enhancement increases as the orientation approaches a singular orientation and as the solidification velocity increases. Shear flows interact with the traveling waves and, depending on the direction of the flow, may either stabilize or destabilize the interface. Specific calculations are carried out for germanium-silicon alloys.

  15. The cement solidification systems at LANL

    Veazey, G.W.


    There are two major cement solidification systems at Los Alamos National Laboratory. Both are focused primarily around treating waste from the evaporator at TA-55, the Plutonium Processing Facility. The evaporator receives the liquid waste stream from TA-55's nitric acid-based, aqueous-processing operations and concentrates the majority of the radionuclides in the evaporator bottoms solution. This is sent to the TA-55 cementation system. The evaporator distillate is sent to the TA-50 facility, where the radionuclides are precipitated and then cemented. Both systems treat TRU-level waste, and so are operated according to the criteria for WIPP-destined waste, but they differ in both cement type and mixing method. The TA-55 systems uses Envirostone, a gypsum-based cement and in-drum prop mixing; the TA-50 systems uses Portland cement and drum tumbling for mixing.

  16. A study on the Abruzzo 6 April 2009 earthquake by applying the RST approach to 15 years of AVHRR TIR observations

    M. Lisi


    Full Text Available A self adaptive approach (RST, Robust Satellite Technique has been proposed as a suitable tool for satellite TIR surveys in seismically active regions devoted to detect and monitor thermal anomalies possibly related to earthquake occurrence. In this work, RST approach has been applied to 15 years of AVHRR (Advanced Very High Resolution Radiometer thermal infrared observations in order to study the 6 April 2009 Abruzzo earthquake. Preliminary results show clear differences in TIR anomalies occurrence during the periods used for validation (15 March–15 April 2009 and the one (15 March–15 April 2008 without earthquakes with ML≥4.5, used for confutation purposes. Quite clear TIR anomalies appears also to mark main tectonic lineaments during the preparatory phases of others, low magnitude(3.9<ML<4.6 earthquakes, occurred in the area in the same period.

  17. A note on the interplay between symmetries, reduction and conservation laws of Stokes’ first problem for third-grade rotating fluids

    K Fakhar; A A Zainal; A H Kara


    We investigate the invariance properties, nontrivial conservation laws and interplay between these notions that underly the equations governing Stokes’ first problem for third-grade rotating fluids. We show that a knowledge of this leads to a number of different reductions of the governing equations and, thus, a number of exact solutions can be obtained and a spectrum of further analyses may be pursued.

  18. Experimental Determination of the Primary Solidification Phase dependency on the solidification velocity for 17 different austenitic stainless steel compositions

    Laursen, Birthe Nørgaard; Olsen, Flemming Ove; Yardy, John;


    to the austenite phase.Most stainless steels are weldable by conventional welding techniques. However, during laser weldng the solidification velocities can be very much higher than by conventional welding techniques. By increasing the solidification velocity to a critical value known as the transition velocity......, the primary solidification phase is found to change from ferrite to austenite.A novel laser remelting technique has been modified to enable the transition velocity for laser welded austenitic stainless steels to be deermined experimentally and on the basis of results from 17 different alloy compositions...... an equation for the calculation of the transition velocity from alloy composition is proposed....

  19. Stabilization/solidification of mercury-contaminated waste ash using calcium sodium phosphate (CNP) and magnesium potassium phosphate (MKP) processes.

    Cho, Jae Han; Eom, Yujin; Lee, Tai Gyu


    This study examined the stabilization and solidification (S/S) of mercury (Hg)-contaminated waste ash generated from an industrial waste incinerator using chemically bonded phosphate ceramic (CBPC) technology. A magnesium potassium phosphate (MKP; MgKPO4 · 6H2O) ceramic, fabricated from MgO and KH2PO4, and a calcium sodium phosphate (CNP; CaNaPO4) ceramic, fabricated from CaO and Na2HPO4, were used as solidification binders in the CBPC process, and Na2S or FeS was added to each solidification binder to stabilize the Hg-contaminated waste ash. The S/S processes were conducted under various operating conditions (based on the solidification binder and stabilization reagent, stabilization reagent dosage, and waste loading ratio), and the performance characteristics of the S/S sample under each operating condition were compared, including the Hg leaching value and compressive strength. The Hg leaching value of untreated Hg-contaminated waste ash was 231.3 μg/L, whereas the S/S samples treated using the MKP and CNP processes exhibited Hg leaching values below the universal treatment standard (UTS) limit (25 μg/L). Although the compressive strengths of the S/S samples decreased as the sulfide dosage and waste loading ratio were increased, most of the S/S samples fabricated by the MKP and CNP processes exhibited good mechanical properties.

  20. Fundamentals of Alloy Solidification Applied to Industrial Processes


    Solidification processes and phenomena, segregation, porosity, gravity effects, fluid flow, undercooling, as well as processing of materials in the microgravity environment of space, now available on space shuttle flights were discussed.

  1. Effect Of Natural Convection On Directional Solidification Of Pure Metal

    Skrzypczak T.


    Full Text Available The paper is focused on the modeling of the directional solidification process of pure metal. During the process the solidification front is sharp in the shape of the surface separating liquid from solid in three dimensional space or a curve in 2D. The position and shape of the solid-liquid interface change according to time. The local velocity of the interface depends on the values of heat fluxes on the solid and liquid sides. Sharp interface solidification belongs to the phase transition problems which occur due to temperature changes, pressure, etc. Transition from one state to another is discontinuous from the mathematical point of view. Such process can be identified during water freezing, evaporation, melting and solidification of metals and alloys, etc.

  2. Rapid Solidification of AB5 Hydrogen Storage Alloys

    Gulbrandsen-Dahl, Sverre


    This doctoral thesis is concerned with rapid solidification of AB5 materials suitable for electrochemical hydrogen storage. The primary objective of the work has been to characterise the microstructure and crystal structure of the produced AB5 materials as a function of the process parameters, e.g. the cooling rate during rapid solidification, the determination of which has been paid special attention to.The thesis is divided in to 6 parts, of which Part I is a literature review, starting wit...

  3. Eutectic-Free Superalloy Made By Directional Solidification

    Schmidt, Deborah Dianne


    By suitable control of thermal conditions in directional-solidification process, supperalloy structural and machine components (e.g., turbine blades) cast with microstructures enhancing resistance to fatigue. Specific version of process and thermal conditions chosen to reduce micro-segregation during solidification and to minimize or eliminate script carbide and eutectic-phase inclusions, which are brittle inclusions found to decrease resistance to fatigue.

  4. Variable-Temperature-Gradient Device for Solidification Research

    Kaukler, W. F.


    Device for research in solidification and crystal growth allows crystallization of melt observed as occurs. Temperature gradient across melt specimen increased or decreased rapidly while solidification front proceeds at constant speed across sample. Device moves sample at same speed, thereby holding position of liquid/solid interface stationary within field of optical microscope. Device, variabletemperature-gradient microscope stage, used to study crystal growth at constant rate while thermal driving force is varied.

  5. Experimental Determination of the Primary Solidification Phase dependency on the solidification velocity for 17 different austenitic stainless steel compositions

    Laursen, Birthe Nørgaard; Olsen, Flemming Ove; Yardy, John


    When studying laser welding of austenitic stainless steel, hot cracking is frequently observed. To prevent hot cracking in laser welded stainless steel it is advantageous to obtain primary solidification of the ferrite phase that subsequently, on cooling, transforms in the solid state...... to the austenite phase.Most stainless steels are weldable by conventional welding techniques. However, during laser weldng the solidification velocities can be very much higher than by conventional welding techniques. By increasing the solidification velocity to a critical value known as the transition velocity......, the primary solidification phase is found to change from ferrite to austenite.A novel laser remelting technique has been modified to enable the transition velocity for laser welded austenitic stainless steels to be deermined experimentally and on the basis of results from 17 different alloy compositions...

  6. Stabilization and Solidification of Nitric Acid Effluent Waste at Y-12

    Singh, Dileep [Argonne National Lab. (ANL), Argonne, IL (United States); Lorenzo-Martin, Cinta [Argonne National Lab. (ANL), Argonne, IL (United States)


    Consolidated Nuclear Security, LLC (CNS) at the Y-12 plant is investigating approaches for the treatment (stabilization and solidification) of a nitric acid waste effluent that contains uranium. Because the pH of the waste stream is 1-2, it is a difficult waste stream to treat and stabilize by a standard cement-based process. Alternative waste forms are being considered. In this regard, Ceramicrete technology, developed at Argonne National Laboratory, is being explored as an option to solidify and stabilize the nitric acid effluent wastes.

  7. Segregation behaviour and phase developments during solidification of Inconel 625; effect of iron and carbon

    Højerslev, Christian; Tiedje, Niels; Hald, John


    The key to improve the performance of Inconel 625 weld overlays applied for corrosion resistance in waste incinerator plants is to understand the solidification process: At present, enhanced resistance against fireside corrosion in waste incinerator boilers is commonly achieved by overlay welding...... with nickel based alloys i.e. Inconel grades. The final layer has a thickness of at least 2 mm. This layer has a dendritic morphology with a dendrite arm spacing of a few microns. In general, this combination of material and process technology provides an adequate solution. However, corrosive attacks...

  8. Solidification phenomena in metal matrix nanocomposites

    de Cicco, Michael Peter


    Nanoparticles in metal matrix nanocomposites (MMNCs) were shown to act as catalysts for nucleation of solidification of the matrix alloy, as well as to alter the intermetallic phase formation. These phenomena were studied in zinc, aluminum, and magnesium alloys. In all alloys studied, a refinement of the microstructure was seen with the addition of the nanoparticles. Various types of nanoparticles were used and had varying degrees of refinement. In a zinc alloy, AC43A, SiC, TiC, and Al2O3 gamma nanoparticles were all found to refine the alloy. Thermal analysis of bulk samples showed the onset of solidification at reduced undercoolings, indicating nucleation catalysis. Nucleation of the primary phase was also observed by employing the droplet emulsion technique (DET). DET results showed that the secondary phase nucleation was also catalyzed by the nanoparticles. Exploiting the nucleation catalysis of the nanoparticles and the associated grain refinement, a semi-solid casting (SSC) process was demonstrated in AC43A + SiC nanocomposites. This novel process successfully incorporated the strength enhancement of MMNCs and the casting quality benefits of SSC. This process required no additional processing steps or material handling typical of existing SSC processes. The nucleation catalysis of the nanoparticles was sufficient to create semi-solid slurries appropriate for SSC. Nanoparticle induced nucleation catalysis was also examined in a common aluminum alloy, A356, using the DET. All nanoparticles catalyzed nucleation of the primary Al phase. However, undercoolings varied depending on the nanoparticle identity and average diameter. The variation in undercoolings generally agreed with a modified lattice disregistry theory and the free growth theory. For nanoparticles with a small lattice spacing mismatch with the Al phase, undercoolings approached the size dependent free growth limit. Binary alloys of magnesium and zinc showed significant strength and ductility

  9. The effects of solidification on sill propagation dynamics and morphology

    Chanceaux, L.; Menand, T.


    Sills are an integral part of the formation and development of larger plutons and magma reservoirs. Thus sills are essential for both the transport and the storage of magma in the Earth's crust. However, although cooling and solidification are central to magmatism, their effects on sills have been so far poorly studied. Here, the effects of solidification on sill propagation dynamics and morphology are studied by means of analogue laboratory experiments. Hot fluid vegetable oil (magma analogue), that solidifies during its propagation, is injected as a sill in a colder layered gelatine solid (elastic host rock analogue). The injection flux and temperature are maintained constant during an experiment and systematically varied between each experiment, in order to vary and quantify the amount of solidification between each experiments. The oil is injected directly at the interface between the two gelatine layers. When solidification effects are small (high injection temperatures and fluxes), the propagation is continuous and the sill has a regular and smooth surface. Inversely, when solidification effects are important (low injection temperatures and fluxes), sill propagation is discontinuous and occurs by steps of surface-area creation interspersed with periods of momentary arrest. The morphology of these sills displays folds, ropy structures on their surface, and lobes with imprints of the leading fronts that correspond to each step of area creation. These experiments show that for a given, constant injected volume, as solidification effects increase, the area of the sills decreases, their thickness increases, and the number of propagation steps increases. These results have various geological and geophysical implications. The morphology of sills, such as lobate structures (interpretation of 3D seismic studies in sedimentary basin) and ropy flow structures (field observations) can be related to solidification during emplacement. Moreover, a non-continuous morphology

  10. Comparison of the fixation effects of heavy metals by cement rotary kiln co-processing and cement based solidification/stabilization.

    Zhang, Junli; Liu, Jianguo; Li, Cheng; Jin, Yiying; Nie, Yongfeng; Li, Jinhui


    Cement rotary kiln co-processing of hazardous wastes and cement based solidification/stabilization could both immobilize heavy metals. The different retention mechanisms of the two technologies lead to different fixation effects of heavy metals. The same amount of heavy metal compounds were treated by the two types of fixation technologies. Long-term leaching test (160 days), the maximum availability leaching test (NEN 7341) and a modified three-step sequential extraction procedure, proposed by the Commission of the European Communities Bureau of Reference (BCR) were employed to compare the fixation effects of the two fixation technologies. The leaching concentrations in NEN 7341 and long-term leaching tests were compared with identification standard for hazardous wastes (GB5085.3-1996) and drinking water standard (GB5749-2005). The results indicate that the leaching concentrations of the long-term leaching test and NEN 7341 test were lower than the regulatory limits and the leached ratios were small. Both cement based solidification/stabilization and cement rotary kiln co-processing could effectively fix heavy metals. Calcination in a cement rotary kiln and the following hydration that follows during cement application could fix As, Cd, Pb and Zn more effectively and decrease the release to the environment. Cement solidification/stabilization technology has better effect in immobilizing Cr and Ni. Cr wastes are more fitful to be treated by cement solidification/stabilization.

  11. Effective solidification/stabilisation of mercury-contaminated wastes using zeolites and chemically bonded phosphate ceramics.

    Zhang, Shaoqing; Zhang, Xinyan; Xiong, Ya; Wang, Guoping; Zheng, Na


    In this study, two kinds of zeolites materials (natural zeolite and thiol-functionalised zeolite) were added to the chemically bonded phosphate ceramic processes to treat mercury-contaminated wastes. Strong promotion effects of zeolites (natural zeolite and thiol-functionalised zeolite) on the stability of mercury in the wastes were obtained and these technologies showed promising advantages toward the traditional Portland cement process, i.e. using Portland cement as a solidification agent and natural or thiol-functionalised zeolite as a stabilisation agent. Not only is a high stabilisation efficiency (lowered the Toxicity Characteristic Leaching Procedure Hg by above 10%) obtained, but also a lower dosage of solidification (for thiol-functionalised zeolite as stabilisation agent, 0.5 g g(-1) and 0.7 g g(-1) for chemically bonded phosphate ceramic and Portland cement, respectively) and stabilisation agents (for natural zeolite as stabilisation agent, 0.35 g g(-1) and 0.4 g g(-1) for chemically bonded phosphate ceramic and Portland cement, respectively) were used compared with the Portland cement process. Treated by thiol-functionalised zeolite and chemically bonded phosphate ceramic under optimum parameters, the waste containing 1500 mg Hg kg(-1) passed the Toxicity Characteristic Leaching Procedure test. Moreover, stabilisation/solidification technology using natural zeolite and chemically bonded phosphate ceramic also passed the Toxicity Characteristic Leaching Procedure test (the mercury waste containing 625 mg Hg kg(-1)). Moreover, the presence of chloride and phosphate did not have a negative effect on the chemically bonded phosphate ceramic/thiol-functionalised zeolite treatment process; thus, showing potential for future application in treatment of 'difficult-to-manage' mercury-contaminated wastes or landfill disposal with high phosphate and chloride content.

  12. Crustal fingering: solidification on a moving interface

    Fu, Xiaojing; Jimenez-Martinez, Joaquin; Porter, Mark; Cueto-Felgueroso, Luis; Juanes, Ruben


    Viscous fingering-the hydrodynamic instability that takes place when a less viscous fluid displaces a more viscous fluid-is a well known phenomenon. Motivated by the formation of gas hydrates in seafloor sediments and during the ascent of gas bubbles through ocean water, here we study the interplay of immiscible viscous fingering with solidification of the evolving unstable interface. We present experimental observations of the dynamics of a bubble of Xenon in a water-filled and pressurized Hele-Shaw cell. The evolution is controlled by two processes: (1) the formation of a hydrate "crust" around the bubble, and (2) viscous fingering from bubble expansion. To reproduce the experimental observations, we propose a phase-field model that describes the nucleation and thickening of a porous solid shell on a moving gas-liquid interface. We design the free energy of the three-phase system (gas-liquid-hydrate) to rigorously account for interfacial effects, mutual solubility, and phase transformations (hydrate formation and disappearance). We introduce a pseudo-plasticity model with large variations in viscosity to describe the plate-like rheology of the hydrate shell. We present high-resolution numerical simulations of the model, which illustrate the emergence of complex "crustal fingering" patterns as a result of gas fingering dynamics modulated by hydrate growth at the interface.

  13. Onset of sidebranching in directional solidification.

    Echebarria, Blas; Karma, Alain; Gurevich, Sebastian


    We use a computationally efficient phase-field formulation [B. Echebarria, Phys. Rev. E 70, 061604 (2004)] to investigate the origin and dynamics of sidebranching in directional solidification for realistic parameters of a dilute alloy previously studied experimentally [M. Gorgelin and A. Pocheau, Phys. Rev. E 57, 3189 (1998)]. Sidebranching is found to result either from noise amplification or from deterministic oscillations that exist both in two dimensions and in a three-dimensional thin-sample geometry. The oscillatory branch of growth solutions bifurcates subcritically from the main steady-state branch of solutions and exists over a finite range of large array spacings. In contrast, noise-induced sidebranching is associated with a smooth transition where the sidebranching amplitude increases exponentially with spacing up to nonlinear saturation due to the overlap of diffusion fields from neighboring cells, as observed experimentally. In the latter case where sidebranching is noise-induced, we find that increasing the externally imposed thermal gradient reduces the onset velocity and wavelength of sidebranching, as also observed experimentally. We show that this counterintuitive effect is due to tip blunting with increasing thermal gradient that promotes noise amplification in the tip region.

  14. Interface Pattern Selection in Directional Solidification

    Trivedi, Rohit; Tewari, Surendra N.


    The central focus of this research is to establish key scientific concepts that govern the selection of cellular and dendritic patterns during the directional solidification of alloys. Ground-based studies have established that the conditions under which cellular and dendritic microstructures form are precisely where convection effects are dominant in bulk samples. Thus, experimental data can not be obtained terrestrially under pure diffusive regime. Furthermore, reliable theoretical models are not yet possible which can quantitatively incorporate fluid flow in the pattern selection criterion. Consequently, microgravity experiments on cellular and dendritic growth are designed to obtain benchmark data under diffusive growth conditions that can be quantitatively analyzed and compared with the rigorous theoretical model to establish the fundamental principles that govern the selection of specific microstructure and its length scales. In the cellular structure, different cells in an array are strongly coupled so that the cellular pattern evolution is controlled by complex interactions between thermal diffusion, solute diffusion and interface effects. These interactions give infinity of solutions, and the system selects only a narrow band of solutions. The aim of this investigation is to obtain benchmark data and develop a rigorous theoretical model that will allow us to quantitatively establish the physics of this selection process.

  15. A new coupled model for alloy solidification

    LI Daming; LI Ruo; ZHANG Pingwen


    A new coupled model in the binary alloy solidification has been developed. The model is based on the cellular automaton (CA)technique to calculate the evolution of the interface governed by temperature, solute diffusion and Gibbs-Thomson effect. The diffusion equation of temperature with the release of latent heat on the solid/liquid (S/L) interface is valid in the entire domain.The temperature diffusion without the release of latent heat and solute diffusion are solved in the entire domain. In the interface cells, the energy and solute conservation, thermodynamic and chemical potential equilibrium are adopted to calculate the temperature, solid concentration, liquid concentration and the increment of solid fraction. Compared with other models where the release of latent heat is solved in implicit or explicit form according to the solid/liquid (S/L) interface velocity, the energy diffusion and the release of latent heat in this model are solved at differentscales, I.e. The macro-scale and micro-scale. The variation ofsolid fraction in this model is solved using several algebraicrelations coming from the chemical potential equilibrium andthermodynamic equilibrium which can be cheaply solved insteadof the calculation of S/L interface velocity. With the assumptionof the solute conservation and energy conservation, the solidfraction can be directly obtained according to the thermodynamicdata. This model is natural to be applied to multiple (>2)spatial dimension case and multiple (>2) component alloy. Themorphologies of equiaxed dendrite are obtained in numericalexperiments.

  16. Weld solidification cracking in 304 to 204L stainless steel

    Hochanadel, Patrick W [Los Alamos National Laboratory; Lienert, Thomas J [Los Alamos National Laboratory; Martinez, Jesse N [Los Alamos National Laboratory; Johnson, Matthew Q [Los Alamos National Laboratory


    A series of annulus welds were made between 304 and 304L stainless steel coaxial tubes using both pulsed laser beam welding (LBW) and pulsed gas tungsten arc welding (GTAW). In this application, a change in process from pulsed LBW to pulsed gas tungsten arc welding was proposed to limit the possibility of weld solidification cracking since weldability diagrams developed for GTAW display a greater range of compositions that are not crack susceptible relative to those developed for pulsed LBW. Contrary to the predictions of the GTAW weldability diagram, cracking was found.This result was rationalized in terms of the more rapid solidification rate of the pulsed gas tungsten arc welds. In addition, for the pulsed LBW conditions, the material compositions were predicted to be, by themselves, 'weldable' according to the pulsed LBW weldability diagram. However, the composition range along the tie line connecting the two compositions passed through the crack susceptible range. Microstructurally, the primary solidification mode (PSM) of the material processed with higher power LBW was determined to be austenite (A), while solidification mode of the materials processed with lower power LBW apparently exhibited a dual PSM of both austenite (A) and ferrite-austenite (FA) within the same weld. The materials processed by pulsed GTAW showed mostly primary austenite solidification, with some regions of either primary austenite-second phase ferrite (AF) solidification or primary ferrite-second phase austenite (FA) solidification. This work demonstrates that variations in crack susceptibility may be realized when welding different heats of 'weldable' materials together, and that slight variations in processing can also contribute to crack susceptibility.

  17. Weld solidification cracking in 304 to 304L stainless steel

    Hochanadel, Patrick W [Los Alamos National Laboratory; Lienert, Thomas J [Los Alamos National Laboratory; Martinez, Jesse N [Los Alamos National Laboratory; Martinez, Raymond J [Los Alamos National Laboratory; Johnson, Matthew Q [Los Alamos National Laboratory


    A series of annulus welds were made between 304 and 304L stainless steel coaxial tubes using both pulsed laser beam welding (LBW) and pulsed gas tungsten arc welding (GTAW). In this application, a change in process from pulsed LBW to pulsed gas tungsten arc welding was proposed to limit the possibility of weld solidification cracking since weldability diagrams developed for GTAW display a greater range of compositions that are not crack susceptible relative to those developed for pulsed LBW. Contrary to the predictions of the GTAW weldability diagram, cracking was found. This result was rationalized in terms of the more rapid solidification rate of the pulsed gas tungsten arc welds. In addition, for the pulsed LBW conditions, the material compositions were predicted to be, by themselves, 'weldable' according to the pulsed LBW weldability diagram. However, the composition range along the tie line connecting the two compositions passed through the crack susceptible range. Microstructurally, the primary solidification mode (PSM) of the material processed with higher power LBW was determined to be austenite (A), while solidification mode of the materials processed with lower power LBW apparently exhibited a dual PSM of both austenite (A) and ferrite-austenite (FA) within the same weld. The materials processed by pulsed GT A W showed mostly primary austenite solidification, with some regions of either primary austenite-second phase ferrite (AF) solidification or primary ferrite-second phase austenite (FA) solidification. This work demonstrates that variations in crack susceptibility may be realized when welding different heats of 'weldable' materials together, and that slight variations in processing can also contribute to crack susceptibility.

  18. Numerical study on morphology and solidification characteristics of successive droplet depositions on a substrate

    Adaikalanathan, Vimalan

    Successive droplet impingement finds extensive applications in additive manufacturing technologies such as 3D printing, Liquid Metal Jetting and Net Form Manufacturing. Deposition, deformation and solidification of droplets are the constitutive stages in the process which determine the final outcome. Detailed knowledge about the flow behaviour, phase transformation and free surface deformation is required to have a complete understanding and optimization of the process parameters. Experimental research in this field is only limited to imaging techniques and post solidification analysis which only provide superficial information while overlooking most of the governing phenomenon. Knowledge of the physics governing the fluid and thermal behaviours can be applied to study the process with real time data pertaining to flow field, temperature profiles and solidification. However, free surface tracking, surface tension modelling, non-isothermal solidification and convection dominant heat transfer pose mathematical challenges in the solution of the governing equations. Moreover, deposition of droplets on pre-solidified splats or non-flat surfaces requires accurate special attention. The objective of the present work is to model the successive droplet impacts and simultaneous solidification and deformation. The highly non-linear flow field governed by the Navier Stokes equation is solved using a Two Step Projection method. The surface tension effects are accounted for through a Continuum Surface Force technique. One of the crucial elements in the study is the interface tracking algorithm. A Coupled Level Set Volume of Fluid (CLSVOF) method is formulated to give an accurate orientation of the drastically deforming interface and also facilitates generation of multiple droplets in a fixed domain at a user defined frequency, thereby conserving computational resources. The phase change is modelled using an enthalpy formulation of the energy equation with an implicit source term

  19. The RST and PARP-like domain containing SRO protein family: analysis of protein structure, function and conservation in land plants

    Salojärvi Jarkko


    Full Text Available Abstract Background The SROs (SIMILAR TO RCD-ONE are a group of plant-specific proteins which have important functions in stress adaptation and development. They contain the catalytic core of the poly(ADP-ribose polymerase (PARP domain and a C-terminal RST (RCD-SRO-TAF4 domain. In addition to these domains, several, but not all, SROs contain an N-terminal WWE domain. Results SROs are present in all analyzed land plants and sequence analysis differentiates between two structurally distinct groups; cryptogams and monocots possess only group I SROs whereas eudicots also contain group II. Group I SROs possess an N-terminal WWE domain (PS50918 but the WWE domain is lacking in group II SROs. Group I domain structure is widely represented in organisms as distant as humans (for example, HsPARP11. We propose a unified nomenclature for the SRO family. The SROs are able to interact with transcription factors through the C-terminal RST domain but themselves are generally not regulated at the transcriptional level. The most conserved feature of the SROs is the catalytic core of the poly(ADP-ribose polymerase (PS51059 domain. However, bioinformatic analysis of the SRO PARP domain fold-structure and biochemical assays of AtRCD1 suggested that SROs do not possess ADP-ribosyl transferase activity. Conclusions The SROs are a highly conserved family of plant specific proteins. Sequence analysis of the RST domain implicates a highly preserved protein structure in that region. This might have implications for functional conservation. We suggest that, despite the presence of the catalytic core of the PARP domain, the SROs do not possess ADP-ribosyl transferase activity. Nevertheless, the function of SROs is critical for plants and might be related to transcription factor regulation and complex formation.

  20. The RST and PARP-like domain containing SRO protein family: analysis of protein structure, function and conservation in land plants.

    Jaspers, Pinja; Overmyer, Kirk; Wrzaczek, Michael; Vainonen, Julia P; Blomster, Tiina; Salojärvi, Jarkko; Reddy, Ramesha A; Kangasjärvi, Jaakko


    The SROs (SIMILAR TO RCD-ONE) are a group of plant-specific proteins which have important functions in stress adaptation and development. They contain the catalytic core of the poly(ADP-ribose) polymerase (PARP) domain and a C-terminal RST (RCD-SRO-TAF4) domain. In addition to these domains, several, but not all, SROs contain an N-terminal WWE domain. SROs are present in all analyzed land plants and sequence analysis differentiates between two structurally distinct groups; cryptogams and monocots possess only group I SROs whereas eudicots also contain group II. Group I SROs possess an N-terminal WWE domain (PS50918) but the WWE domain is lacking in group II SROs. Group I domain structure is widely represented in organisms as distant as humans (for example, HsPARP11). We propose a unified nomenclature for the SRO family. The SROs are able to interact with transcription factors through the C-terminal RST domain but themselves are generally not regulated at the transcriptional level. The most conserved feature of the SROs is the catalytic core of the poly(ADP-ribose) polymerase (PS51059) domain. However, bioinformatic analysis of the SRO PARP domain fold-structure and biochemical assays of AtRCD1 suggested that SROs do not possess ADP-ribosyl transferase activity. The SROs are a highly conserved family of plant specific proteins. Sequence analysis of the RST domain implicates a highly preserved protein structure in that region. This might have implications for functional conservation. We suggest that, despite the presence of the catalytic core of the PARP domain, the SROs do not possess ADP-ribosyl transferase activity. Nevertheless, the function of SROs is critical for plants and might be related to transcription factor regulation and complex formation.

  1. Investigation of Melting and Solidification of Thin Polycrystalline Silicon Films via Mixed-Phase Solidification

    Wang, Ying

    Melting and solidification constitute the fundamental pathways through which a thin-film material is processed in many beam-induced crystallization methods. In this thesis, we investigate and leverage a specific beam-induced, melt-mediated crystallization approach, referred to as Mixed-Phase Solidification (MPS), to examine and scrutinize how a polycrystalline Si film undergoes the process of melting and solidification. On the one hand, we develop a more general understanding as to how such transformations can transpire in polycrystalline films. On the other hand, by investigating how the microstructure evolution is affected by the thermodynamic properties of the system, we experimentally reveal, by examining the solidified microstructure, fundamental information about such properties (i.e., the anisotropy in interfacial free energy). Specifically, the thesis consists of two primary parts: (1) conducting a thorough and extensive investigation of the MPS process itself, which includes a detailed characterization and analysis of the microstructure evolution of the film as it undergoes MPS cycles, along with additional development and refinement of a previously proposed thermodynamic model to describe the MPS melting-and-solidification process; and (2) performing MPS-based experiments that were systematically designed to reveal more information on the anisotropic nature of Si-SiO2 interfacial energy (i.e., sigma Si-SiO2). MPS is a recently developed radiative-beam-based crystallization technique capable of generating Si films with a combination of several sought-after microstructural characteristics. It was conceived, developed, and characterized within our laser crystallization laboratory at Columbia University. A preliminary thermodynamic model was also previously proposed to describe the overall melting and solidification behavior of a polycrystalline Si film during an MPS cycle, wherein the grain-orientation-dependent solid-liquid interface velocity is identified

  2. Effects of rapid solidification on the microstructure and microhardness of a lead-free Sn-3.5Ag solder

    SHEN Jun; LIU Yongchang; Han Yajing; GAO Houxiu


    A lead-free Sn-3.5Ag solder was prepared by rapid solidification technology. The high solidification rate, obtained by rapid cooling, promotes nucleation, and suppresses the growth of Ag3Sn intermetallic compounds (IMCs) in Ag-rich zone, yielding fine Ag3Sn nanoparticulates with spherical morphology in the matrix of the solder. The large amount of tough homogeneously-dispersed IMCs helps to improve the surface area per unit volume and obstructs the dislocation lines passing through the solder, which fits with the dispersion-strengthening theory. Hence, the rapidly-solidified Sn-3.5Ag solder exhibits a higher microhardness when compared with a slowly-solidified Sn-3.5Ag solder.

  3. Shape sensitivity analysis in numerical modelling of solidification

    E. Majchrzak


    Full Text Available The methods of sensitivity analysis constitute a very effective tool on the stage of numerical modelling of casting solidification. It is possible, among others, to rebuilt the basic numerical solution on the solution concerning the others disturbed values of physical and geometrical parameters of the process. In this paper the problem of shape sensitivity analysis is discussed. The non-homogeneous casting-mould domain is considered and the perturbation of the solidification process due to the changes of geometrical dimensions is analyzed. From the mathematical point of view the sensitivity model is rather complex but its solution gives the interesting information concerning the mutual connections between the kinetics of casting solidification and its basic dimensions. In the final part of the paper the example of computations is shown. On the stage of numerical realization the finite difference method has been applied.

  4. Simulation of shrinkage cavity formation during solidification of binary alloy

    T. Skrzypczak


    Full Text Available Presented paper is focused on numerical modeling of binary alloy solidification process with connection to shrinkage cavity formation phenomenon. Appropriate matching of cooling parameters during solidification process of the cast with raiser is essential to obtain suitable properties of the manufactured part. Localization, structure and depth of the shrinkage cavity is connected to these parameters. The raiser is removed after process, so defect localization in the top part of the manufactured element is of great importance. Mathematical model of solidification process is presented in the paper. The main focus is put on the algorithm of shrinkage cavity creation process. On the basis of mathematical model the numerical approach using finite element method is proposed. On the base of mathematical and numerical model computer program is made. It is able to perform simulation of the shrinkage cavity formation in 2D region. Shape and localization of shrinkage cavity obtained from simulation is compared to defect which was created during experiment.

  5. Matemathical description of solidification cooling curves of pure metals

    Arno Müller


    Full Text Available The introduction of an "incubation time" to the Schwarz classical mathematical description of metals solidification, resulted in a new model called Modified Schwarz Model. By doing so it was possible to identify and quantify the "delay time" that separates the two heat waves traveling independently in a casting during the solidification: the Supercooled / Superheated Liquid and the Solid / Liquid. The thermal shock produced in the initial stage of the undercooling generation process, can be used as an important parameter in the forecasting of the solidification's behavior of pure metals and alloys, when changing mold's materials, pouring and ambient temperatures. The hypercooling proneness degree of metals and alloys, can also be calculated.

  6. Non-equilibrium solidification of undercooled droplets during atomization process

    Prashant Shukla; R K Mandal; S N Ojha


    Thermal history of droplets associated with gas atomization of melt has been investigated. A mathematical model, based on classical theory of heterogeneous nucleation and volume separation of nucleants among droplets size distribution, is described to predict undercooling of droplets. Newtonian heat flow condition coupled with velocity dependent heat transfer coefficient is used to obtain cooling rate before and after nucleation of droplets. The results indicate that temperature profile of droplets in the spray during recalescence, segregated and eutectic solidification regimes is dependent on their size and related undercooling. The interface temperature during solidification of undercooled droplets rapidly approaches the liquidus temperature of the alloy with a subsequent decrease in solid–liquid interface velocity. A comparison in cooling rates of atomized powder particles estimated from secondary dendrite arm spacing measurements are observed to be closer to those predicted from the model during segregated solidification regime of large size droplets.

  7. Stabilization/Solidification Remediation Method for Contaminated Soil: A Review

    Tajudin, S. A. A.; Azmi, M. A. M.; Nabila, A. T. A.


    Stabilization/Solidification (S/S) is typically a process that involves a mixing of waste with binders to reduce the volume of contaminant leachability by means of physical and chemical characteristics to convert waste in the environment that goes to landfill or others possibly channels. Stabilization is attempts to reduce the solubility or chemical reactivity of the waste by changing the physical and chemical properties. While, solidification attempt to convert the waste into easily handled solids with low hazardous level. These two processes are often discussed together since they have a similar purpose of improvement than containment of potential pollutants in treated wastes. The primary objective of this review is to investigate the materials used as a binder in Stabilization/Solidification (S/S) method as well as the ability of these binders to remediate the contaminated soils especially by heavy metals.

  8. Inverse thermal analysis method to study solidification in cast iron

    Dioszegi, Atilla; Hattel, Jesper


    Solidification modelling of cast metals is widely used to predict final properties in cast components. Accurate models necessitate good knowledge of the solidification behaviour. The present study includes a re-examination of the Fourier thermal analysis method. This involves an inverse numerical...... solution of a 1-dimensional heat transfer problem connected to solidification of cast alloys. In the analysis, the relation between the thermal state and the fraction solid of the metal is evaluated by a numerical method. This method contains an iteration algorithm controlled by an under relaxation term...... was developed in order to investigate the thermal behaviour of the solidifying metal. Three cylindrically shaped cast samples surrounded by different cooling materials were introduced in the same mould allowing a common metallurgical background for samples solidifying at different cooling rates. The proposed...

  9. In-Situ Analysis of Coarsening during Directional Solidification Experiments in High-Solute Aluminum Alloys

    Ruvalcaba, D.; Mathiesen, R.H.; Eskin, D.G.; Arnberg, L.; Katgerman, L.


    Coarsening within the mushy zone during continuous directional solidification experiments was studied on an Al-30 wt pct Cu alloy. High brilliance synchrotron X-radiation microscopy allowed images to be taken in-situ during solidification. Transient conditions were present during directional solidif

  10. Effects of Pulse Current on Solidification Structure of Austenitic Stainless Steel

    FAN Jin-hui; CHEN Yu; LI Ren-xing; ZHAI Qi-jie


    The 1Cr18Ni9Ti specimens were treated respectively with pulse current under 520 V and 2 600 V during solidification and the solidification structure was observed. The results showed that pulse current can refine solidification grains, cut primary dentrities remarkably and reduce second dentritic arm spacing. The mechanism and effect are changed with operation parameters.

  11. Application of modern software packages to calculating the solidification of high-speed steels

    Morozov, S. I.


    The solidification of high-speed steels is calculated with the Pandat and JMatPro software packages. The results of calculating equilibrium and nonequilibrium solidification are presented and discussed. The nonequilibrium solidification is simulated using the Shelley-Gulliver model. The fraction of carbides changes as a function of the carbon content in the steels.

  12. Modelling of convection during solidification of metal and alloys

    A K Singh; R Pardeshi; B Basu


    The role of convection during solidification is studied with the help of a mathematical model. The effect of various mush models on convection and consequent macrosegregation is examined with the help of numerical simulations. The predicted macrosegregation profiles are compared with published experimental data. Subsequently, the importance of proper auxiliary relationship for thermo-solutal coupling in the mushy region is highlighted through some careful numerical simulations. Finally, the role of material parameters on double-diffusive convection is illustrated through comparative study of solidification of aqueous ammonium chloride, iron-carbon and lead-tin binary systems. Important results of these studies are presented and discussed.

  13. Modeling solidification structure evolution and microsegregation under pressure condition

    Qiang Li; Qiaoyi Guo; Rongde Li


    Solidification microstructure and microsegregation were simulated under a constant pressure condition using the cellular automaton method. First, a single dendrite evolution was simulated and compared under pressure condition and under normal condition,respectively. The solidification microstructure and microsegregation were then simulated. Through simulation, it may be concluded that if the growth direction of the dendrite is parallel to the pressure direction, dendrite growth will be hindered. On the other hand,pressure has no influence on the dendrite evolution. However, when two dendrites grow in close contact, solute enrichment occurs in the dendrites, which hinders the growth of the dendrites. In addition, the solute is preferentially enriched along the pressure direction.

  14. Heat Transfer and Its Effect on Solidification in Combined Mould

    QIU Sheng-tao; TAO Hong-biao; TANG Hong-wei; ZHANG Hui; ZHAO Pei


    The nucleation can be enhanced by decreasing the superheat of molten steel, thus reducing temperature gradient on the solidification front can retard the growth of columnar crystals and enlarge the equiaxed zone in continuous casting strand. The billets with equiaxed zone more than 90% were cast with a combined mould and the heatflux was measured. The heat transfer of the combined mould and traditional mould was compared. The results show that under same casting conditions, the temperature gradient on the solidification front in the combined mould is smaller than that in traditional mould at a distance within 0-150 mm from the meniscus.

  15. Solidification microstructure of directionally solidified superalloy under high temperature gradient


    The effect of solidification rate on the microstructure development of nickel-based superalloy under the temperature gradient of 500 K·cm-1 was studied. The results show that, with the increase of directional solidification rate from 50 to 800 μm·s-1, both the primary and the secondary dendrite arm spacings of the alloy decrease gradually, and the dendrite morphologies transform from coarse dendrite to superfine dendrite. The sizes of all precipitates in the superalloy decrease gradually. The morphology of ...

  16. Potential Flow Interactions With Directional Solidification

    Buddhavarapu, Sudhir S.; Meiburg, Eckart


    The effect of convective melt motion on the growth of morphological instabilities in crystal growth has been the focus of many studies in the past decade. While most of the efforts have been directed towards investigating the linear stability aspects, relatively little attention has been devoted to experimental and numerical studies. In a pure morphological case, when there is no flow, morphological changes in the solid-liquid interface are governed by heat conduction and solute distribution. Under the influence of a convective motion, both heat and solute are redistributed, thereby affecting the intrinsic morphological phenomenon. The overall effect of the convective motion could be either stabilizing or destabilizing. Recent investigations have predicted stabilization by a flow parallel to the interface. In the case of non-parallel flows, e.g., stagnation point flow, Brattkus and Davis have found a new flow-induced morphological instability that occurs at long wavelengths and also consists of waves propagating against the flow. Other studies have addressed the nonlinear aspects (Konstantinos and Brown, Wollkind and Segel)). In contrast to the earlier studies, our present investigation focuses on the effects of the potential flow fields typically encountered in Hele-Shaw cells. Such a Hele-Shaw cell can simulate a gravity-free environment in the sense that buoyancy-driven convection is largely suppressed, and hence negligible. Our interest lies both in analyzing the linear stability of the solidification process in the presence of potential flow fields, as well as in performing high-accuracy nonlinear simulations. Linear stability analysis can be performed for the flow configuration mentioned above. It is observed that a parallel potential flow is stabilizing and gives rise to waves traveling downstream. We have built a highly accurate numerical scheme which is validated at small amplitudes by comparing with the analytically predicted results for the pure




    Full Text Available In this research solidification characteristic of metal matrix composites consisted of titanium carbide particulate reinforced aluminium-11.8% silicon alloy matrix is performed. Vortex mixing and permanent casting method are used as the manufacturing method to produce the specimens. Temperature measurements during the casting process are captured and solidification graphs are plotted to represent the solidification characteristic. The results show, as volume fraction of particulate reinforcement is increased, solidification time is faster. Particulate reinforcement promotes rapid solidification which will support finer grain size of the casting specimen. Hardness test is performed and confirmed that hardness number increased as more particulate are added to the system.

  18. Construction and analysis of dynamic solidification curves for non-equilibrium solidification process in lost-foam casting hypo-eutectic gray cast iron

    Ming-guo Xie


    Full Text Available Most lost-foam casting processes involve non-equilibrium solidification dominated by kinetic factors, while construction of a common dynamic solidification curve is based on pure thermodynamics, not applicable for analyses and research of non-equilibrium macro-solidification processes, and the construction mode can not be applied to non-equilibrium solidification process. In this study, the construction of the dynamic solidification curve (DSC for the non-equilibrium macro-solidification process included: a modified method to determine the start temperature of primary austenite precipitation (TAL and the start temperature of eutectic solidification (TES; double curves method to determine the temperature of the dendrite coherency point of primary austenite (TAC and the temperature of eutectic cells collision point (TEC; the “technical solidus” method to determine the end temperature of eutectic reaction (TEN. For this purpose, a comparative testing of the non-equilibrium solidification temperature fields in lost-foam casting and green sand mold casting hypoeutectic gray iron was carried out. The thermal analysis results were used to construct the DSCs of both these casting methods under non-equilibrium solidification conditions. The results show that the transformation rate of non-equilibrium solidification in hypoeutectic gray cast iron is greater than that of equilibrium solidification. The eutectic solidification region presents a typical mushy solidification mode. The results also indicate that the primary austenite precipitation zone of lost-foam casting is slightly larger than that of green sand casting. At the same time, the solid fraction (fs of the dendrite coherency points in lost-foam casting is greater than that in the green sand casting. Therefore, from these two points, lost-foam casting is more preferable for reduction of shrinkage and mechanical burnt-in sand tendency of the hypoeutectic gray cast iron. Due to the fact that

  19. Phase-field simulation of peritectic solidification closely coupled with directional solidification experiments in an Al-36 wt% Ni alloy.

    Siquieri, R; Doernberg, E; Emmerich, H; Schmid-Fetzer, R


    In this work we present experimental and theoretical investigations of the directional solidification of Al-36 wt% Ni alloy. A phase-field approach (Folch and Plapp 2005 Phys. Rev. E 72 011602) is coupled with the CALPHAD (calculation of phase diagrams) method to be able to simulate directional solidification of Al-Ni alloy including the peritectic phase Al(3)Ni. The model approach is calibrated by systematic comparison to microstructures grown under controlled conditions in directional solidification experiments. To illustrate the efficiency of the model it is employed to investigate the effect of temperature gradient on the microstructure evolution of Al-36 wt% Ni during solidification.

  20. Rapid solidification processing of iron-base alloys for structural applications

    Flinn, J.E.


    The response of iron-base alloys to rapid solidification is reviewed with an emphasis on the effects of processing on the microstructure and mechanical property behavior. The processing topics addressed are powder atomization, powder consolidation, joining, and thermal-mechanical exposure. The value of rapid solidification processing (RSP) lies in the ability to promote compositional homogeneity and retention of fine and stable (to high temperatures) microstructures. Achieving the maximum benefit from RSP requires proper application of the basic principles of composition control and rapid crystallization. This investigation has disclosed two very important facets of the RSP approach that can be applied using current technologies. Dissociated oxygen appears to play a significant role in stabilizing microstructural features. In conjunction with oxygen, vacancies trapped during crystallization provide a very stable matrix dispersion for enhanced strengthening. With a fundamental understanding of the response of iron-base alloys to RSP, alloys can be designed that will have substantially better properties and performance than their conventionally processed counterparts. 77 refs., 94 figs., 14 tabs.

  1. Numerical Simulation and Optimization of Directional Solidification Process of Single Crystal Superalloy Casting

    Hang Zhang


    Full Text Available The rapid development of numerical modeling techniques has led to more accurate results in modeling metal solidification processes. In this study, the cellular automaton-finite difference (CA-FD method was used to simulate the directional solidification (DS process of single crystal (SX superalloy blade samples. Experiments were carried out to validate the simulation results. Meanwhile, an intelligent model based on fuzzy control theory was built to optimize the complicate DS process. Several key parameters, such as mushy zone width and temperature difference at the cast-mold interface, were recognized as the input variables. The input variables were functioned with the multivariable fuzzy rule to get the output adjustment of withdrawal rate (v (a key technological parameter. The multivariable fuzzy rule was built, based on the structure feature of casting, such as the relationship between section area, and the delay time of the temperature change response by changing v, and the professional experience of the operator as well. Then, the fuzzy controlling model coupled with CA-FD method could be used to optimize v in real-time during the manufacturing process. The optimized process was proven to be more flexible and adaptive for a steady and stray-grain free DS process.

  2. Exploring new concepts in directional solidification by electron beam melting and selective laser melting

    Martinez, Edwin

    Unlike more conventional directional solidification, electron and laser-beam melting technologies involve building 3D components through layer-by-layer melt/solidification thermal cycling which creates novel, directional microstructural architectures. In this study we compared various the columnar microstructures of various components manufactured by EBM and SLM; image composite observations of columnar microstructural architectures in Cu, Co-29-Cr-6Mo-0.2C alloy, Ni-22Cr-9Mo-4Nb (alloy 625) fabricated by electron beam melting (EBM), and Ni-19Cr-19Fe-5Nb-1Al (alloy 718) by selective laser melting (SLM) as well as stainless steel 17-4 PH (SLM). Cu produced discontinuous columns of Cu2O precipitates while the Co-base alloy exhibited similar columns of Cr 23C6 precipitates. The alloy 625 produced columns of Ni 3Nb (Upsilon"-bct) precipitates. All of the EBM-produced columnar microstructure arrays were spaced ˜2 microm. In contrast, the SLM fabricated alloy 718 contained columnar microstructural arrays of Ni3 Nb (Upsilon") spaced ˜ 0.8microm, the 17-4 PH stainless steel produced martensitic structures dependent on the gas used for manufacturing. The manufactured components were observed by optical microscopy, SEM, XRD and by TEM in order to understand the microstructural development.

  3. Study on soil solidification based on microbiological precipitation of CaCO3


    The soil solidifying technology started booming from the 1940s and formed an integrated cross-discipline.This paper aimed to study the effect and mechanism of soil solidification by microorganisms.Soil specimens treated by different methods were designed.Then the compressive strengths of these specimens on day 7 were tested and the situ bacteria culturing technique in soil was investigated.Finally the mechanism of soil solidification by microorganisms was explored according to the decomposition rate of substrate,pH value and the SEM and XRD analysis.Experimental results showed that the soil could be solidified by filling enhancement and precipitation of microorganisms.The compressive strength increased with bacteria A but decreased with substrate B,and soil specimen got a higher strength with bacteria situ cultured.The suitable pH value for bacteria A was 8–9,and the delay of lime addition could make substrate decomposition more completely,lower the influence by the existence of substrate,and improve the strength.In XRD and SEM images,precipitation of CaCO3 could be speculated.

  4. Particle Trapping and Banding in Rapid Colloidal Solidification

    Elliott, J. A. W.


    We derive an expression for the nonequilibrium segregation coefficient of colloidal particles near a moving solid-liquid interface. The resulting kinetic phase diagram has applications for the rapid solidification of clay soils, gels, and related colloidal systems. We use it to explain the formation of bandlike defects in rapidly solidified alumina suspensions. © 2011 American Physical Society.

  5. Solidification in a Supercomputer: From Crystal Nuclei to Dendrite Assemblages

    Shibuta, Yasushi; Ohno, Munekazu; Takaki, Tomohiro


    Thanks to the recent progress in high-performance computational environments, the range of applications of computational metallurgy is expanding rapidly. In this paper, cutting-edge simulations of solidification from atomic to microstructural levels performed on a graphics processing unit (GPU) architecture are introduced with a brief introduction to advances in computational studies on solidification. In particular, million-atom molecular dynamics simulations captured the spontaneous evolution of anisotropy in a solid nucleus in an undercooled melt and homogeneous nucleation without any inducing factor, which is followed by grain growth. At the microstructural level, the quantitative phase-field model has been gaining importance as a powerful tool for predicting solidification microstructures. In this paper, the convergence behavior of simulation results obtained with this model is discussed, in detail. Such convergence ensures the reliability of results of phase-field simulations. Using the quantitative phase-field model, the competitive growth of dendrite assemblages during the directional solidification of a binary alloy bicrystal at the millimeter scale is examined by performing two- and three-dimensional large-scale simulations by multi-GPU computation on the supercomputer, TSUBAME2.5. This cutting-edge approach using a GPU supercomputer is opening a new phase in computational metallurgy.

  6. Changes in porosity of foamed aluminum during solidification


    In order to control the porosity of foamed aluminum, the changes in the porosity of foamed aluminum melt in the processes of foaming and solidification, the distribution of the porosity of foamed aluminum, and the relationship between them were studied. The results indicated that the porosity of foamed aluminum coincides well with the foaming time.

  7. Overview of the Tusas Code for Simulation of Dendritic Solidification

    Trainer, Amelia J. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Newman, Christopher Kyle [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Francois, Marianne M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)


    The aim of this project is to conduct a parametric investigation into the modeling of two dimensional dendrite solidification, using the phase field model. Specifically, we use the Tusas code, which is for coupled heat and phase-field simulation of dendritic solidification. Dendritic solidification, which may occur in the presence of an unstable solidification interface, results in treelike microstructures that often grow perpendicular to the rest of the growth front. The interface may become unstable if the enthalpy of the solid material is less than that of the liquid material, or if the solute is less soluble in solid than it is in liquid, potentially causing a partition [1]. A key motivation behind this research is that a broadened understanding of phase-field formulation and microstructural developments can be utilized for macroscopic simulations of phase change. This may be directly implemented as a part of the Telluride project at Los Alamos National Laboratory (LANL), through which a computational additive manufacturing simulation tool is being developed, ultimately to become part of the Advanced Simulation and Computing Program within the U.S. Department of Energy [2].

  8. Three-dimensional solidification and melting using magnetic field control

    Dulikravich, George S.; Ahuja, Vineet


    A new two-fluid mathematical model for fully three dimensional steady solidification under the influence of an arbitrary acceleration vector and with or without an arbitrary externally applied steady magnetic field have been formulated and integrated numerically. The model includes Joule heating and allows for separate temperature dependent physical properties within the melt and the solid. Latent heat of phase change during melting/solidification was incorporated using an enthalpy method. Mushy region was automatically captured by varying viscosity orders of magnitude between liquidus and solidus temperature. Computational results were obtained for silicon melt solidification in a parallelepiped container cooled from above and from a side. The results confirm that the magnetic field has a profound influence on the solidifying melt flow field thus changing convective heat transfer through the boundaries and the amount and shape of the solid accrued. This suggests that development of a quick-response algorithm for active control of three dimensional solidification is feasible since it would require low strength magnetic fields.

  9. Multi-crystalline silicon solidification under controlled forced convection

    Cablea, M.; Zaidat, K.; Gagnoud, A.; Nouri, A.; Chichignoud, G.; Delannoy, Y.


    Multi-crystalline silicon wafers have a lower production cost compared to mono-crystalline wafers. This comes at the price of reduced quality in terms of electrical properties and as a result the solar cells made from such materials have a reduced efficiency. The presence of different impurities in the bulk material plays an important role during the solidification process. The impurities are related to different defects (dislocations, grain boundaries) encountered in multi-crystalline wafers. Applying an alternative magnetic field during the solidification process has various benefits. Impurities concentration in the final ingot could be reduced, especially metallic species, due to a convective term added in the liquid that reduces the concentration of impurities in the solute boundary layer. Another aspect is the solidification interface shape that is influenced by the electromagnetic stirring. A vertical Bridgman type furnace was used in order to study the solidification process of Si under the influence of a travelling magnetic field able to induce a convective flow in the liquid. The furnace was equipped with a Bitter type three-phase electromagnet that provides the required magnetic field. A numerical model of the furnace was developed in ANSYS Fluent commercial software. This paper presents experimental and numerical results of this approach, where interface markings were performed.

  10. The Effect of Solidification Rate on Morphological Stability

    Sekerka, R. F.


    At low solidification rates, the criterion for the onset of morphological instability parallels closely the criterion of constitutional supercooling. At somewhat larger rates of solidification, however, the results of the perturbation theory of morphological instability differ significantly from the predictions of constitutional supercooling. This arises because the critical wave length for instability decreases as solidification rate increases and thus the effects of capillarity (solid-liquid surface tension) play a strong stabilizing role. This gives rise to the concept of absolute stability, according to which the system will always be stable for a sufficiently large rate of solidification. This enhanced stabilization by capillarity is present only so long as local equilibrium is maintained at the solid-liquid interface. If the interfacial temperature drops below its equilibrium value by an amount dependent on growth rate, oscillatory morphological instabilities can occur. The differences among these various stability criteria are illustrated by means of some simple two-dimensional diagrams that should supplant the conventional plots of (temperature gradient)/(growth rate) vs. alloy concentration.

  11. Microstructural Development in Al-Si Powder During Rapid Solidification

    Genau, Amber Lynn [Iowa State Univ., Ames, IA (United States)


    Powder metallurgy has become an increasingly important form of metal processing because of its ability to produce materials with superior mechanical properties. These properties are due in part to the unique and often desirable microstructures which arise as a result of the extreme levels of undercooling achieved, especially in the finest size powder, and the subsequent rapid solidification which occurs. A better understanding of the fundamental processes of nucleation and growth is required to further exploit the potential of rapid solidification processing. Aluminum-silicon, an alloy of significant industrial importance, was chosen as a model for simple eutectic systems displaying an unfaceted/faceted interface and skewed coupled eutectic growth zone, Al-Si powder produced by high pressure gas atomization was studied to determine the relationship between microstructure and alloy composition as a function of powder size and atomization gas. Critical experimental measurements of hypereutectic (Si-rich) compositions were used to determine undercooling and interface velocity, based on the theoretical models which are available. Solidification conditions were analyzed as a function of particle diameter and distance from nucleation site. A revised microstructural map is proposed which allows the prediction of particle morphology based on temperature and composition. It is hoped that this work, by providing enhanced understanding of the processes which govern the development of the solidification morphology of gas atomized powder, will eventually allow for better control of processing conditions so that particle microstructures can be optimized for specific applications.

  12. Solidification of Hypereutectic Thin Wall Ductile Cast Iron

    Pedersen, Karl Martin; Tiedje, Niels Skat


    Hypereutectic ductile iron was cast in green sand moulds with four plates with thickness of 1.5, 2, 3 and 4 mm in each mould. Temperatures were measured in the 3 and 4 mm plate. The temperature curves showed that eutectic solidification was divided into two stages: primary and secondary eutectic...

  13. Solidification paths in modified Inconel 625 weld overlay material

    Chandrasekaran, Karthik; Tiedje, Niels Skat; Hald, John


    Inconel 625 is commonly used for overlay welding to protect the base metal against high temperature corrosion. The efficiency of corrosion protection depends on effective mixing of the overlay weld with the base metal and the subsequent segregation of alloy elements during solidification...

  14. Solidification at the High and Low Rate Extreme

    Meco, Halim [Iowa State Univ., Ames, IA (United States)


    The microstructures formed upon solidification are strongly influenced by the imposed growth rates on an alloy system. Depending on the characteristics of the solidification process, a wide range of growth rates is accessible. The prevailing solidification mechanisms, and thus the final microstructure of the alloy, are governed by these imposed growth rates. At the high rate extreme, for instance, one can have access to novel microstructures that are unattainable at low growth rates. While the low growth rates can be utilized for the study of the intrinsic growth behavior of a certain phase growing from the melt. Although the length scales associated with certain processes, such as capillarity, and the diffusion of heat and solute, are different at low and high rate extremes, the phenomena that govern the selection of a certain microstructural length scale or a growth mode are the same. Consequently, one can analyze the solidification phenomena at both high and low rates by using the same governing principles. In this study, we examined the microstructural control at both low and high extremes. For the high rate extreme, the formation of crystalline products and factors that control the microstructure during rapid solidification by free-jet melt spinning are examined in Fe-Si-B system. Particular attention was given to the behavior of the melt pool at different quench-wheel speeds. Since the solidification process takes place within the melt-pool that forms on the rotating quench-wheel, we examined the influence of melt-pool dynamics on nucleation and growth of crystalline solidification products and glass formation. High-speed imaging of the melt-pool, analysis of ribbon microstructure, and measurement of ribbon geometry and surface character all indicate upper and lower limits for melt-spinning rates for which nucleation can be avoided, and fully amorphous ribbons can be achieved. Comparison of the relevant time scales reveals that surface-controlled melt

  15. Progress on Numerical Modeling of the Dispersion of Ceramic Nanoparticles During Ultrasonic Processing and Solidification of Al-Based Nanocomposites

    Zhang, Daojie; Nastac, Laurentiu


    In present study, 6061- and A356-based nano-composites are fabricated by using the ultrasonic stirring technology (UST) in a coreless induction furnace. SiC nanoparticles are used as the reinforcement. Nanoparticles are added into the molten metal and then dispersed by ultrasonic cavitation and acoustic streaming assisted by electromagnetic stirring. The applied UST parameters in the current experiments are used to validate a recently developed magneto-hydro-dynamics (MHD) model, which is capable of modeling the cavitation and nanoparticle dispersion during UST processing. The MHD model accounts for turbulent fluid flow, heat transfer and solidification, and electromagnetic field, as well as the complex interaction between the nanoparticles and both the molten and solidified alloys by using ANSYS Maxwell and ANSYS Fluent. Molecular dynamics (MD) simulations are conducted to analyze the complex interactions between the nanoparticle and the liquid/solid interface. The current modeling results demonstrate that a strong flow can disperse the nanoparticles relatively well during molten metal and solidification processes. MD simulation results prove that ultrafine particles (10 nm) will be engulfed by the solidification front instead of being pushed, which is beneficial for nano-dispersion.

  16. Progress on Numerical Modeling of the Dispersion of Ceramic Nanoparticles During Ultrasonic Processing and Solidification of Al-Based Nanocomposites

    Zhang, Daojie; Nastac, Laurentiu


    In present study, 6061- and A356-based nano-composites are fabricated by using the ultrasonic stirring technology (UST) in a coreless induction furnace. SiC nanoparticles are used as the reinforcement. Nanoparticles are added into the molten metal and then dispersed by ultrasonic cavitation and acoustic streaming assisted by electromagnetic stirring. The applied UST parameters in the current experiments are used to validate a recently developed magneto-hydro-dynamics (MHD) model, which is capable of modeling the cavitation and nanoparticle dispersion during UST processing. The MHD model accounts for turbulent fluid flow, heat transfer and solidification, and electromagnetic field, as well as the complex interaction between the nanoparticles and both the molten and solidified alloys by using ANSYS Maxwell and ANSYS Fluent. Molecular dynamics (MD) simulations are conducted to analyze the complex interactions between the nanoparticle and the liquid/solid interface. The current modeling results demonstrate that a strong flow can disperse the nanoparticles relatively well during molten metal and solidification processes. MD simulation results prove that ultrafine particles (10 nm) will be engulfed by the solidification front instead of being pushed, which is beneficial for nano-dispersion.

  17. Modeling fluid interactions with the rigid mush in alloy solidification

    Plotkowski, Alexander J.

    Macrosegregation is a casting defect characterized by long range composition differences on the length scale of the ingot. These variations in local composition can lead to the development of unwanted phases that are detrimental to mechanical properties. Unlike microsegregation, in which compositions vary over the length scale of the dendrite arms, macrosegregation cannot be removed by subsequent heat treatment, and so it is critical to understand its development during solidification processing. Due to the complex nature of the governing physical phenomena, many researchers have turned to numerical simulations for these predictions, but properly modeling alloy solidification presents a variety of challenges. Among these is the appropriate treatment of the interface between the bulk fluid and the rigid mushy zone. In this region, the non-linear and coupled behavior of heat transfer, fluid mechanics, solute transport, and alloy thermodynamics has a dramatic effect on macrosegregation predictions. This work investigates the impact of numerical approximations at this interface in the context of a mixture model for alloy solidification. First, the numerical prediction of freckles in columnar solidification is investigated, and the predictive ability of the model is evaluated. The model is then extended to equiaxed solidification, in which the analogous interface is the transition of free-floating solid particles to a rigid dendritic network. Various models for grain attachment are investigated, and found to produce significant artifacts caused by the discrete nature of their implementation on the numerical grid. To reduce the impact of these artifacts, a new continuum grain attachment model is proposed and evaluated. The differences between these models are compared using uncertainty quantification, and recommendations for future research are presented.

  18. Comparative study between PI, RST and sliding mode controllers of a DFIG supplied by an AC-AC converter for wind energy conversion system

    Ahmed Bourouina


    Full Text Available This paper deals with a variable speed device to produce electrical energy on a power network, based on a doubly-fed induction generator (DFIG supplied by a direct matrix converter used in wind energy conversion systems. In the first place, we carried out briefly a study of modelling on the whole system. In order to control the power flowing between the stator of the DFIG and the power network, a control law is synthesized using three types of controllers: PI, RST and sliding mode controllers. Their respective performances are compared in terms of power reference tracking, response to sudden speed variations, sensitivity to perturbations and robustness against machine parameters variations.

  19. Suppression of Amplitude dependent closest tune approach and first tests of the ADT as an AC-dipole (MD 1412)

    Persson, Tobias Hakan Bjorn; Maclean, Ewen Hamish; Olexa, Jakub; Tomas Garcia, Rogelio; Valuch, Daniel; Wierichs, David Alexander; Carlier, Felix Simon; CERN. Geneva. ATS Department


    The amplitude detuning has been observed to decrease significantly as the horizontal and vertical tunes are approaching each other. The measured tune split (Qₓ −Qᵧ) versus amplitude was several times bigger than what can be explained with linear coupling during the non-linear MD in 2012 [1]. This effect is potentially harmful since it might cause a loss of Landau damping, hence giving rise to instabilities. In this MD we validated the findings in the MD from 2012 and demonstrated the possibility to mitigate this effect through having opposite polarity of the focusing and defocusing octupoles (MOD and MOF). The amplitude dependent dependent closest tune approach was also measured with the AC-dipole and gave unexpected results. A first test of using the ADT as an AC-dipole was also performed.

  20. On the potential of an RST-based analysis of the MODIS-derived chl-a product over Condor seamount and surrounding areas (Azores, NE Atlantic)

    Ciancia, Emanuele; Magalhães Loureiro, Clara; Mendonça, Ana; Coviello, Irina; Di Polito, Carmine; Lacava, Teodosio; Pergola, Nicola; Satriano, Valeria; Tramutoli, Valerio; Martins, Ana


    Oceanographic cruises have been conducted on the Condor seamount (SW Faial Island, Azores archipelago, NE Atlantic) since 2009 to collect in situ data and understand potential seamount effects on local biodiversity. Satellite data have been concurrently collected to infer the space-time upper-ocean optical property variability and the associated physical processes. The main limitation of this analysis is the persistent and significant cloud coverage above the region that, especially in some seasons, can significantly hinder satellite data availability. This study was meant to test the robust satellite technique (RST) over the Condor seamount, assess its capability to estimate multiyear trends and identify space-time anomalies. To this aim, 11-year MODIS/AQUA level 2-derived chlorophyll-a (chl-a) data were used. Results achieved for October 2010 show, within a large-scale analysis, the presence of well-defined areas of near-surface chl-a anomalies, highlighting the occurrence of a trapping effect due to flow-topography interaction processes. Regarding the Condor area, the chl-a anomalies detected along the eastern side of the seamount were linked to a strong vertical mixing that provided sufficient inorganic nutrients requested for productivity. The achieved results, whose accuracy was also tested through a comparison with in situ data, are consistent with those independently obtained by other authors who described the phytoplankton variability around the Condor seamount. This study shows the high potential of the RST approach to assess the chl-a variability in the space-time domain in oligotrophic regions such as the Azores, allowing the identification of the most important areas to be preserved and/or managed.

  1. 伤寒杆菌耐药质粒pRST98介导细菌毒力的研究%Studies on virulence mediated by drug resistant Salmonella typhi R plasmid

    黄瑞; 吴淑燕; 闻玉梅


    Objective To explore the possibility of R plasmid (pRST98) encoding resistance to antimicrobial agents in S. typhi mediate virulence to its host bacteria. Methods pRST98 was transferred into a less virulent strain of S. typhimurium RIA for creating a transconjugant pRST98/RIA. The standard S. typhimurium virulence strain SR-11 which carries a 100kb virulence plasmid was used as a positive control, and RIA as a negative one. Infection with S. typhimurium was employed to assess the effect of pRST98 on the virulence of host bacteria by LD50 of peroral (p.o.) and intraperitoneal (i.p.) infection of BALB/c mice. After oral inoculation of the bacteria into BALB/c mice, mesenteric lymph nodes, spleen and liver were examined for quantity of bacteria and for the histopathological changes. The three strains were also studied for their in vitro adhesion and invasion of HEp-2, CHO and HeLa cells. Three chromosomally isogenic strains, i.e., plasmid-containing wild-type S. typhi strain, plasmid artificially cured strain and plasmid-reintroduced into the cured strain were compared for their resistance to the bactericidal activity present in human, rabbit and guinea pig sera. Results The p.o. and i.p. LD50 of pRST98/RIA was 700 and 75 folds less than that of RIA. The bacteria counting in mesenteric lymph nodes, spleen and liver were more (P<0.05) and more severe histopathological changes were observed in pRST98 harboring S. typhimurium. However, pRST98 did not affect the adhesion and invasion of S. typhimurium to the cells. Experiments showed that pRST98 mediated resistance to serum bactericidal effect in host bacteria (P<0.05). Conclusion This is the first report about a plasmid carrying genes coding for drug resistance and virulence in S. typhi. The data presented here suggested that novel virulence gene or related sequences, which are important in the pathogenesis of Salmonella infection could exist on pRST98.%目的研究伤寒杆菌耐药质粒pRST98能否介导细菌毒力。方法将pRST

  2. Investigation of Intermetallic Compound Formed from Rapid Solidification of Al-Ti-RE Alloy

    杨明珊; 王振飞


    Al-Ti alloy containing rare earth elements can produce fine,uniform dispersion intermetallic phase through rapid solidification(RS)technology.RS Al-Ti-RE alloy can be designed for applications at elevated-temperature since the intermetallic compound has good thermal stability.A transmission electron microscopy investigation shows the intermetallic phase has a diamond cubic structure(a=1.47736 nm),with space group Fd3m.The chemical stoichiometry is Al20Ti2La.The particle is formed from the melting directly,prior to other phases,and the nucleus is formed from icosahedrons composed with twenty tetrahedrons.Twin crystal structure plays an important role in the nucleation stage.

  3. Critical parameters and TCLP performance of the RFP microwave solidification system

    Sprenger, G.S.


    Two series of experiments were conducted at Rocky Flats Plant (RFP) to identify the critical operating parameters for microwave solidification and to evaluate the performance of the product against the EPA's Toxicity Characteristic Leach Procedure (TCLP). A surrogate hydroxide coprecipitation sludge spiked with heavy metals was used in the study. The RFP process uses microwave energy to heat and melt the waste into a vitreous final form that is suitable for land disposal. The results of the study indicate that waste loading and borax content in the glass forming frit are critical in the treatment of hydroxide sludge. Also, the product will easily satisfy EPA's limitations for land disposal. These results are very encouraging and support RFP's commitment to the use of microwave technology for treatment of various mixed waste streams at the facility.

  4. Preparation and microstructure of Al-Ni-Y powder by rapid solidification

    黄劲松; 刘咏; 陈仕奇; 刘祖铭


    The Al-Ni Y alloy powder was prepared by rapid solidification technology of inert gas atomization. The diameter of amorphous powder is less than 12 μm. The effects of atomization gas on cooling velocity, morphology,microstructure and microhardness of powder and fine powder ratio were investigated. The results show that the mor-phology, microstructure and microhardness of powder and fine powder ratio are affected by cooling velocity changed through atomization gas. The cooling velocity of inert gas atomization is more than 1 × 104 K/s. The larger the cool-ing velocity, the finer the powder, and the smoother the surface of powder; the smaller the diameter of powder, the larger the microhardness of powder.

  5. Kinetic model of ductile iron solidification with experimental verification

    W. Kapturkiewicz


    Full Text Available A solidification model for ductile iron, including Weibull formula for nodule count has been presented. From this model, the following can be determined: cooling curves, kinetics of austenite and eutectic nucleation, austenite and eutectic growth velocity, volume fraction, distribution of Si and P both in austenite and eutectic grain with distribution in casting section.In the developed model of nodular graphite iron casting solidification, the correctness of the mathematical model has been experimentally verified in the range of the most significant factors, which include temperature field, the value of maximum undercooling, and the graphite nodule count interrelated with the casting cross-section. Literature offers practically no data on so confronted process model and simulation program.

  6. Modeling of solidification of MMC composites during gravity casting process

    R. Zagórski


    Full Text Available The paper deals with computer simulation of gravity casting of the metal matrix composites reinforced with ceramics (MMC into sand mold. The subject of our interest is aluminum matrix composite (AlMMC reinforced with ceramic particles i.e. silicon carbide SiC and glass carbon Cg. The created model describes the process taking into account solidification and its influence on the distribution of reinforcement particles. The computer calculation has been carried out in 2D system with the use of Navier-Stokes equations using ANSYS FLUENT 13. The Volume of Fluid approach (VOF and enthalpy method have been used to model the air-fluid free surface (and also volume fraction of particular continuous phases and the solidification of the cast, respectively.

  7. Solidification zoning and metallographic cooling rates of chondrites

    Willis, J.; Goldstein, J. I.


    The cooling rates of chondrites have been determined according to the cooling rate method of Wood (1967) which involves the measurement of the concentration of nickel in the interiors of taenite grains of various sizes. The present paper presents an investigation of the effect of zoning produced during solidification on the use of the Wood method. Cooling rate curves were obtained in a computer simulation based on a model of kamacite formation on the outer edge of a taenite sphere of uniform initial composition, followed by the inward radial progression of the kamacite-taenite interface. When a concentration gradient produced by solidification is present in the initial conditions, deviations from the cooling rate curves for uniform 10% Ni are obtained only at cooling rates greater than 1000 K/million years, which would result in an overestimation of the cooling rates based on observed Ni gradients in grains of radius greater than 20 microns.

  8. Computer modelling of solidification of pure metals and alloys

    Barkhudarov, M R


    differencing advection algorithm used in the simulations, the Leith's method is incorporated into the public domain two-dimensional SOLA code. It is shown that the resulting scheme is unconditionally stable despite being explicit. Two numerical models have been developed to describe the volumetric changes during solidification in pure metals and alloys and to predict shrinkage defects in the castings of general three-dimensional configuration. The first model is based on the full system of the Continuity, Navier-Stokes and Enthalpy Equations. Volumetric changes are described by introducing a source term in the Continuity Equation which is a function of the rate of local phase transformation. The model is capable of simulating both volumetric shrinkage and expansion. The second simplified shrinkage model involves the solution of only the Enthalpy Equation. Simplifying assumptions that the feeding flow is governed only by gravity and solidification rate and that phase transformation proceeds only from liquid to...

  9. Solidification and ordering during directional drying of a colloidal dispersion.

    Goehring, Lucas; Clegg, William J; Routh, Alexander F


    During drying, colloidal dispersions undergo processes such as solidification, cracking, and the draining of interstitial pores. Here we show that the solidification of polystyrene and silica dispersions, during directional drying, occurs in two separate stages. These correspond to the initial ordering and subsequent aggregation of the colloidal particles. Transitions between these stages are observed as changes in transparency and color that propagate as distinct fronts along the drying layer. The dynamics of these fronts are shown to arise from a balance between compressive capillary forces and the electrostatic and van der Waals forces described by DLVO theory. This suggests a simple method by which the maximum interparticle repulsion between particles can be measured through the optical inspection of the dynamics of a drying dispersion, under a microscope.

  10. Inverse problem for porosity estimation during solidification of TNT

    Aldélio Bueno Caldeira


    Full Text Available In the present study, the porosity formed during the solidification process is estimated by an inverse problem technique based on particle swarm optimization. The effective heat capacity method is adopted to model the heat transfer problem. The transient-diffusive heat transfer equation is solved numerically by the finite volume method with an explicit scheme, employing the central difference interpolation function. The solution of the direct problem is compared to reference solutions. The model is applied to trinitrotoluene (TNT solidification process. The results show that the proposed procedure was able to estimate the porosity for different Stefan numbers. The analysis of the heat flux in the mold is indicated to predict the porosity formation during the casting process.

  11. Nonlinear instability and dynamic bifurcation of a planeinterface during solidification

    吴金平; 侯安新; 黄定华; 鲍征宇; 高志农; 屈松生


    By taking average over the curvature, the temperature and its gradient, the solute con-centration and its gradient at the flange of planar interface perturbed by sinusoidal ripple during solidifi-cation, the nonlinear dynamic equations of the sinusoidal perturbation wave have been set up. Analysisof the nonlinear instability and the behaviors of dynamic bifurcation of the solutions of these equationsshows that (i) the way of dynamic bifurcation of the flat-to-cellular interface transition vades with differ-ent thermal gradients. The quasi-subcritical-lag bifurcation occurs in the small interface thermal gradientscope, the supercritical-lag bifurcation in the medium thermal gradient scope and the supercritical bifur-cation in the large thermal gradient scope. (ii) The transition of cellular-to-flat interface is realizedthrough supercritical inverse bifurcation in the rapid solidification area.

  12. Growth directions of microstructures in directional solidification of crystalline materials.

    Deschamps, J; Georgelin, M; Pocheau, A


    In directional solidification, as the solidification velocity increases, the growth direction of cells or dendrites rotates from the direction of the thermal gradient to that of a preferred cristalline orientation. Meanwhile, their morphology varies with important implications for microsegregation. Here, we experimentally document the growth directions of these microstructures in a succinonitrile alloy in the whole accessible range of directions, velocities, and spacings. For this, we use a thin sample made of a single crystal on which the direction of the thermal gradient can be changed. This allows a fine monitoring of the misorientation angle between thermal gradient and preferred crystalline orientation. Data analysis shows evidence of an internal symmetry which traces back to a scale invariance of growth directions with respect to a Péclet number. This enables the identification of the relationship between growth directions and relevant variables, in fair agreement with experiment. Noticeable variations of growth directions with misorientation angles are evidenced and linked to a single parameter.

  13. Dynamics of liquid solidification thermal resistance of contact layer

    Lipnicki, Zygmunt


    This monograph comprehensively describes phenomena of heat flow during phase change as well as the dynamics of liquid solidification, i.e. the development of a solidified layer. The book provides the reader with basic knowledge for practical designs, as well as with equations which describe processes of energy transformation. The target audience primarily comprises researchers and experts in the field of heat flow, but the book may also be beneficial for both practicing engineers and graduate students.

  14. Supporting the model of ductile iron dendritic solidification

    Santos, H.M.C.M. [Porto Univ. (Portugal). Metall. and Mater. Dept.; Pinto, A.M.P. [Minho Univ. (Portugal). Mechanical Engineering Dept.; Jacinto, M.C.P.L. [Porto Polytechnic Inst. and INEGI, Porto (Portugal). Mechanical Engineering Dept.; Sa, C.P.M. [Porto Univ. (Portugal). Materials Center


    Microsegregation in ductile iron is generally accepted as modelled by a regular pattern: the graphite promoter elements are assumed to concentrate in the neighborhood of the graphite nodules and the carbide forming elements in the eutectic cell boundaries. The authors have conducted several microanalyses in several ductile irons and concluded that the microsegregation pattern does not agree with this model but supports the mechanism of dendritic ductile iron solidification. (orig.)

  15. Solidification process and infrared image characteristics of permanent mold castings

    Viets, Roman; Breuer, Markus; Haferkamp, Heinz; Kruessel, Thomas; Niemeyer, Matthias


    Interdependence between the development of temperature gradients at the solid-liquid interface during solidification of metals and the formation of local defects demands for thermal investigation. In foundry practice thermocouples are used to control the die's overall cooling-rate, but fluctuations in product quality still occur. Capturing FIR- thermograms after opening the die visualizes the state, when most thermal throughput has already flattened the temperature gradients in the mold. Rapid dissipation of heat from liquid metal to the mold during solidification forces further approach of the process investigation by slowing down the heat flux or the use of transparent mold material. Aluminum gravity casting experiments under technical vacuum conditions lead to decelerated solidification by suppression of convection and image sequences containing explicit characteristics that could be assigned to local shrinkage of the casting. Hence relevant clusters are extracted and thermal profiles are drawn from image series, pointing out correlations between feeding performance from the sink heads and the appearance of local defects. Tracing thermal processes in vacuum casting can scarcely be transferred to image data in foundry practice, since only little analogies exist between atmospheric and vacuum casting. The diagnosis of the casting process requires detection of the still closed mold using a transparent silica- aerogel sheet as part of the die. Hereby thermograms of the initial heat input are recorded by adapting a NIR-camera in addition to the FIR-unit. Thus the entire thermal compensation at the joint face for each casting is visualized. This experimental set-up is used for image sequence analysis related to the intermediate casting phases of mold filling, body formation and solidification shrinkage.

  16. Development Of A Magnetic Directional-Solidification Furnace

    Aldrich, Bill R.; Lehoczky, Sandor L.


    Report describes development of directional-solidification furnace in which axial magnetic field is imposed by surrounding ring permanent magnets and/or electromagnets and pole pieces. Furnace provides controlled axial temperature gradients in multiple zones, through which ampoule containing sample of material to be solidified is translated at controlled speed by low-vibration, lead-screw, stepping-motor-driven mechanism. Intended for use in low-gravity (spaceflight) experiments on melt growth of high-purity semiconductor crystals.

  17. Interface Pattern Selection Criterion for Cellular Structures in Directional Solidification

    Trivedi, R.; Tewari, S. N.; Kurtze, D.


    The aim of this investigation is to establish key scientific concepts that govern the selection of cellular and dendritic patterns during the directional solidification of alloys. We shall first address scientific concepts that are crucial in the selection of interface patterns. Next, the results of ground-based experimental studies in the Al-4.0 wt % Cu system will be described. Both experimental studies and theoretical calculations will be presented to establish the need for microgravity experiments.

  18. Fluid mechanics and solidification investigations in low-gravity environments

    Fichtl, G. H.; Lundquist, C. A.; Naumann, R. J.


    Fluid mechanics of gases and liquids and solidification processes were investigated under microgravity conditions during Skylab and Apollo-Soyuz missions. Electromagnetic, acoustic, and aerodynamic levitation devices, drop tubes, aircraft parabolic flight trajectories, and vertical sounding rockets were developed for low-g simulation. The Spacelab 3 mission will be carried out in a gravity gradient flight attitude; analyses of sources of vehicle dynamic accelerations with associated g-levels and angular rates will produce results for future specific experiments.

  19. Solidification and microstructure of thin walled ductile cast iron

    Pedersen, Karl Martin


    In the recent years there has been an increasing interest in light constructions in order to save weight in e.g. cars. Ductile cast iron has good mechanical properties but it is necessary to re­duce the wall thicknesses of the castings in order to reduce the weight. Reducing the wall thicknesses...... of the casting will increase the cooling rates and by that change the conditions for nucleation and growth during solidification....

  20. The solidification of two-phase heterogeneous materials: Theory versus experiment

    ZHANG Bin; KIM Tongbeum; LU TianJian


    The solidification behavior of two-phase heterogeneous materials such as close-celled aluminum foams was analytically studied. The proposed analytical model can precisely predict the location of solidification front as well as the full solidification time for a two-phase heterogeneous material composed of aluminum melt and non-conducting air pores. Experiments using distilled water simulating the aluminum melt to be solidified (frozen) were subsequently conducted to validate the analytical model for two selected porosities (ε), ε=0 and 0.5. Full numerical simulations with the method of finite difference were also performed to examine the influence of pore shape on solidification. The remarkable agreement between theory and experiment suggests that the delay of solidification in the two-phase heterogeneous material is mainly caused by the reduction of bulk thermal conductivity due to the presence of pores, as this is the sole mechanism accounted for by the analytical model for solidification in a porous medium.

  1. Microstructural development of rapid solidification in Al-Si powder

    Jin, Feng [Iowa State Univ., Ames, IA (United States)


    The microstructure and the gradient of microstructure that forms in rapidly solidificated powder were investigated for different sized particles. High pressure gas atomization solidification process has been used to produce a series of Al-Si alloys powders between 0.2 μm to 150 μm diameter at the eutectic composition (12.6 wt pct Si). This processing technique provides powders of different sizes which solidify under different conditions (i.e. interface velocity and interface undercooling), and thus give different microstructures inside the powders. The large size powder shows dendritic and eutectic microstructures. As the powder size becomes smaller, the predominant morphology changes from eutectic to dendritic to cellular. Microstructures were quantitatively characterized by using optical microscope and SEM techniques. The variation in eutectic spacing within the powders were measured and compared with the theoretical model to obtain interface undercooling, and growth rate during the solidification of a given droplet. Also, nucleation temperature, which controls microstructures in rapidly solidified fine powders, was estimated. A microstructural map which correlates the microstructure with particle size and processing parameters is developed.

  2. Non-Equilibrium Solidification of Undercooled Metallic Melts

    Dieter M. Herlach


    Full Text Available If a liquid is undercooled below its equilibrium melting temperature an excess Gibbs free energy is created. This gives access to solidification of metastable solids under non-equilibrium conditions. In the present work, techniques of containerless processing are applied. Electromagnetic and electrostatic levitation enable to freely suspend a liquid drop of a few millimeters in diameter. Heterogeneous nucleation on container walls is completely avoided leading to large undercoolings. The freely suspended drop is accessible for direct observation of rapid solidification under conditions far away from equilibrium by applying proper diagnostic means. Nucleation of metastable crystalline phases is monitored by X-ray diffraction using synchrotron radiation during non-equilibrium solidification. While nucleation preselects the crystallographic phase, subsequent crystal growth controls the microstructure evolution. Metastable microstructures are obtained from deeply undercooled melts as supersaturated solid solutions, disordered superlattice structures of intermetallics. Nucleation and crystal growth take place by heat and mass transport. Comparative experiments in reduced gravity allow for investigations on how forced convection can be used to alter the transport processes and design materials by using undercooling and convection as process parameters.

  3. Rapid solidification in thermal spary deposition: Microstructure and modelling

    Guo-Xiang Wang; V Prasad; S Sampath


    Mechanical, thermal, and adhesive properties of thermal spray coatings are primarily determined by the phase and microstructure of single splats, which ultimately depend on rapid solidification of each splat and on the interactions between the splats and between the splat and the substrate. Significant efforts are being made to develop a better understanding of the physical mechanisms underlying these phenomena. This paper reviews a series of work in the area of mathematical modelling of phase and microstructure formation during the rapid solidification of single splats and coatings. The model development has been complimented by special experiments. Conditions under which plariar interface solidification occurs, columnar cellular or dendriric growth takes place, or banded structure forms, have been identified. A microstructure map can therefore be built using the model presented here. The process parameters that promote crystalline nucleation and grain structure formation can be isolated and the effect of interfacial heat transfer, splat substrate temperature difference, and substrate melting and resolidification can be examined using the model. The model predictions agree qualitatively well with the experimental data for alumina, yttria, partially-stabilized zirconia, and molybdenum.

  4. Solidification of sediment contaminated with volatile chlorinated hydrocarbons

    Schwarz, E.J. [Anchor QEA LLC, Portland, OR (United States)


    A series of bench-scale treatability tests were used to evaluate the effectiveness of various solidification reagents in treating sediments contaminated with high concentrations of chlorinated hydrocarbons. The effectiveness of Portland cement, cement kiln dust, lime kiln dust, fly ash, and a combination of silica and lime were was assessed relative to their ability to reduce the leaching of contaminants, increase the strength of the contaminated sediment, and reduce the hydraulic conductivity of the sediments. The aim of the study was to develop a design for treating sediments in a stagnant water body located on the grounds of an industrial facility. The sediments were predominantly fine-grained and high in organic content. Preliminary tests identified Portland cement and the silica and lime mixture as achieving the desired strength and resistance to leaching. The solidification reagents were used to solidify more than 11,000 cubic yards of sediment with a mixture of 2 fly ashes. The full-scale solidification project surpassed the required standards for strength and permeability. 10 refs., 4 tabs., 3 figs.

  5. Solidification microstructure formation in HK40 and HH40 alloys

    Ding, Xian-fei; Liu, Dong-fang; Guo, Pei-liang; Zheng, Yun-rong; Feng, Qiang


    The microstructure formation processes in HK40 and HH40 alloys were investigated through JmatPro calculations and quenching performed during directional solidification. The phase transition routes of HK40 and HH40 alloys were determined as L → L + γ → L + γ + M7C3 → γ + M7C3 → γ + M7C3 + M23C6→ γ + M23C6 and L → L + δ → L + δ + γ→ L + δ + γ + M23C6 δ + γ + M23C6, respectively. The solidification mode was determined to be the austenitic mode (A mode) in HK40 alloy and the ferritic-austenitic solidification mode (FA mode) in HH40 alloy. In HK40 alloy, eutectic carbides directly precipitate in a liquid and coarsen during cooling. The primary γ dendrites grow at the 60° angle to each other. On the other hand, in HH40 alloy, residual δ forms because of the incomplete transformation from δ to γ. Cr23C6 carbide is produced in solid delta ferrite δ but not directly in liquid HH40 alloy. Because of carbide formation in the solid phase and no rapid growth of the dendrite in a non-preferential direction, HH40 alloy is more resistant to cast defect formation than HK40 alloy.

  6. Successful Completion of Outward Transport Disposal Stage Ⅰ of Radioactive Cement Solidification

    DU; Hong-ming; LIU; Fu-guo; JIN; Song


    As the last batch of solidification barrels arriving at the repository on May 5th,2013,the outward transport disposal stage I of radioactive cement solidification completed successfully.This project started in May,2011,lasted for 19 months,during which 9 batches,3 300 barrels of cement solidification,had been retrieved and transferred.It is a lot of preparation work and continuous improvement that to ensure the safety of the outbound work.

  7. Characterization of Solidification and Solid State Transformation in Duplex Cast Steel: Thermo-Calc Investigation


    The paper presents a characteristic of solidification process and changes occurring in the solid state in a duplex cast steel. Theoretical chemical composition of individual phases, its changes during solidification and cooling after solidification and also changes in volume fractions of phases versus temperature have been determined. Theoretical results of Thermo-Calc analysis have been correlated with the microstructure of as-cast cast steel as well as with analysis of chemical composition ...

  8. Effect of solidification rate on microstructure evolution in dual phase microalloyed steel.

    Kostryzhev, A G; Slater, C D; Marenych, O O; Davis, C L


    In steels the dependence of ambient temperature microstructure and mechanical properties on solidification rate is not well reported. In this work we investigate the microstructure and hardness evolution for a low C low Mn NbTi-microalloyed steel solidified in the cooling rate range of 1-50 Cs(-1). The maximum strength was obtained at the intermediate solidification rate of 30 Cs(-1). This result has been correlated to the microstructure variation with solidification rate.

  9. Analysis of a solidification interface stability Al - Cu by the heat balance integral method

    B. Magiera


    Full Text Available The aim of his thesis is the analysis of a planar interface solidification stability of alloys. The stability of a planar interface solidification is tested by means of solving the heat conduction equation for solids and liquid and a mass diffusion equation for liquid, under assumed boundary, initial and continuity conditions. The solidification equations are solved using the method of heat balance integral and the theorem of the derivative integrals, whose limitsdepend on the parameter.

  10. Numerical simulation on directional solidification of Al-Ni-Co alloy based on FEM

    Yang Zhili


    Full Text Available The ratio, of the temperature gradient at the solidification front to the solidification rate of solid-liquid interface, plays a large part in columnar grain growth. The transient temperature fields of directional solidification of Al-Ni-Co alloy were studied by employing a finite element method. The temperature gradient at the solidification front and the solidification rate were analyzed for molten steels pouring at different temperatures. The results show that with different initial pouring temperatures, the individual ratio of the temperature gradient at solidification front to the solidification rate soars up in the initial stage of solidification, then varies within 2,000-6,000 ℃·s·cm-2, and finally goes down rapidly and even tend to be closed to each other when the solidification thickness reaches 5-6 cm. The simulation result is consistent with the practical production which can provide an available reference for process optimization of directional solidified Al-Ni-Co alloy.

  11. The Solidification Velocity of Undercooled Nickel and Titanium Alloys with Dilute Solute

    Algoso, Paul R.; Altgilbers, A. S.; Hofmeister, William H.; Bayuzick, Robert J.


    The study of solidification velocity is important for two reasons. First, understanding the manner in which the degree of undercooling of the liquid and solidification velocity affect the microstructure of the solid is fundamental. Second, there is disagreement between theoretical predictions of the relationship between undercooling and solidification velocity and experimental results. Thus, the objective of this research is to accurately and systematically quantify the solidification velocity as a function of undercooling for dilute nickel-and titanium-based alloys. The alloys chosen for study cover a wide range of equilibrium partition coefficients, and the results are compared to current theory.

  12. MPS Solidification Model. Volume 2: Operating guide and software documentation for the unsteady model

    Maples, A. L.


    The operation of solidification Model 2 is described and documentation of the software associated with the model is provided. Model 2 calculates the macrosegregation in a rectangular ingot of a binary alloy as a result of unsteady horizontal axisymmetric bidirectional solidification. The solidification program allows interactive modification of calculation parameters as well as selection of graphical and tabular output. In batch mode, parameter values are input in card image form and output consists of printed tables of solidification functions. The operational aspects of Model 2 that differ substantially from Model 1 are described. The global flow diagrams and data structures of Model 2 are included. The primary program documentation is the code itself.

  13. Directional Solidification of AlSi Alloys with Fe Intermetallic Phases

    Mikołajczak P.


    Full Text Available Directional solidification technique is an important research instrument to study solidification of metals and alloys. In the paper the model [6,7,8] of directional solidification in special Artemis-3 facility was presented. The current work aimed to propose the ease and efficient way in calibrating the facility. The introduced M coefficient allowed effective calibration and implementation of defined thermal conditions. The specimens of AlSi alloys with Fe-rich intermetallics and especially deleterious β-Al5FeSi were processed by controlled solidification velocity, temperature gradient and cooling rate.

  14. Effect of low temperature melt on solidification structure of A356 alloy with melt thermal treatment

    何树先; 王俊; 孙宝德; 周尧和


    The influence of the low temperature melt (LTM) structure on solidification structure of the sample with melt thermal treatment (MTT) process was studied. And the mechanism of the MTT process was analyzed with cluster theory. It is shown that the final solidification structure is dependent mainly on the structure of LTM. Dendrites will appear in the solidification structure if the structure of LTM is dendritic before MTT. Otherwise, non-dendritic grains will appear in the solidification structure. And the lower the temperature of LTM, the more remarkable the effect of the LTM structure is.

  15. Numerical investigation of a binary solidification design problem

    Hale, Scott Wayne

    This exposition presents the development and application of a methodology for control of unidirectional solidification of a binary alloy. In particular, it is desired to produce a casting that has a uniform cast structure throughout its entire length. Furthermore, the methodology allows the specification, a priori, of the cast structure with respect to both scale, i.e., fine or coarse, and morphology, i.e., dentritic or cellular. This specification is in the form of a map that relates solidification characteristics, i.e., scale and morphology, to the solidification velocity and liquid-side interfacial temperature gradient. Thus design is accomplished by controlling these two parameters during the solidification process. With this in mind, the goal of what is termed the binary solidification design problem is the prediction of a set of boundary temperatures and heat fluxes which when applied will result in the desired interfacial motion and temperature gradient and therefore cast structure. Mathematical models for problems of this type lead to what are termed ill-posed systems in that they may not exhibit existence, uniqueness, or continuous dependence on boundary data. The resolution of this class of problems requires advanced techniques to overcome the instabilities encountered due to their ill-posed nature. The methodology developed herein employs the classical weight residual approach in a innovative manner. Normally, in the solution of a parabolic partial differential equation, such as the heat equation, a spatial series expansion with time varying coefficients is utilized along with a minimization technique to reduce the partial differential equation to a set of first order ordinary differential equations. This set can be solved using any number of numerical technique, i.e., Runge-Kutta, to obtain the temporal variation of the coefficients. These types of time stepping techniques eventually lead to the onset of instability when employed for the resolution of

  16. Skaergaard vs Sudbury: Solidification Times and Crystal Sizes

    Marsh, B. D.; Mittal, T.; Currier, R. M.; Jordon, E.


    The overall cooling time of a batch of magma is intimately reflected in the nature of the crystal sizes. The thinner are dikes and sills the finer grained are the crystals they display. And the spatial variations in crystal size and abundance record the spatial progression of solidification. Chilled margins are fine grained because of rapid solidification, and a progressive inward increase in crystal size is perfectly predictable by coupling a law of crystal growth with a suitable solidification front-based cooling model. When observed crystal sizes are much larger than predicted, as in finding phenocrysts near or in chilled margins, this is a clear indication of crystals grown and entrained prior to final emplacement and solidification. This is exactly the process exhibited by volcanics carrying swarms of large crystals. But in plutonic rocks there is frequent confusion over what crystal sizes to expect, especially when the pluton size and shape is poorly known, and there is often an unexpressed feeling that fine grained (i.e., non-phenocryst bearing) bodies almost regardless of size somehow cool fundamentally different than large bodies, especially layered intrusions. An invaluable standard state body to which to compare the crystal sizes of other large bodies is the Sudbury impact melt sheet. Formed in a few minutes, the 3km thick 200 km wide superheated melt sheet cooled and crystallized to produce a systematic and predictable internal variation in crystal size and abundance (Zieg & Marsh, 2002, JPet). Buried by 3km of fallback debris, the sheet took about 100,000 to solidify. The Skaergaard intrusion is of a similar thickness (3.4-4 km), but is much less extensive, being more like a thin-edged elliptical laccolith (Norton et. al., 1984, JGR) or a fault-bounded loaf of bread (7.75 x 10.55 x 3.7 km; Nielsen, 2004, JPet). In spite of its limited extent, the extent is large enough for solidification of the thickest parts time to approach that of an infinite sheet

  17. Advanced Lost Foam Casting Technology

    Charles E. Bates; Harry E. Littleton; Don Askeland; Taras Molibog; Jason Hopper; Ben Vatankhah


    This report describes the research done under the six tasks to improve the process and make it more functional in an industrial environment. Task 1: Pattern Pyrolysis Products and Pattern Properties Task 2: Coating Quality Control Task 3: Fill and Solidification Code Task 4: Alternate Pattern Materials Task 5: Casting Distortion Task 6: Technology Transfer


    S. N. Bandarenka


    Full Text Available One of the most prospective directions in preservation  and increase of service live of  road pavements is a construction of  automobile roads with cement concrete surface. Modern tendencies for provision of road construction quality presuppose a necessity to control processes of solidification and subsequent destruction of the material while forming and using cement concrete conglomerate being considered as a basic element of the road surface.  Multiyear practical experience of  automobile road operation using cement concrete pavements reveals an importance for monitoring  such processes as formation and destruction of cement concrete materials. An impedance spectroscopy method has been tried out and proposed as a tool for solution of the given problem.Experimental samples of cement concrete have been prepared for execution of tests, graded silica sand and granite chippings with particle size from 0.63 to 2.5 mm have been used as a fine aggregate in the samples. Dependencies of resistance (impedance on AC-current frequency  have been studied for samples of various nature and granulometric composition. The Gamry  G300 potentiostat has been used for measurement of complex impedance value. A spectrum analysis and calculation of equivalent circuit parameters calculation have been carried out while using EIS Spectrum Analyzer program.Comparison of impedance spectra for the prepared cement concrete samples have made it possible to reveal tendencies in changing spectrum parameters during solidification and subsequent contact with moisture in respect of every type of the sample. An equivalent electrical circuit has been developed that  characterizes physical and chemical processes which are accompanied by charge transfer in cement concrete conglomerate. The paper demonstrates a possibility to use an impedance spectroscopy for solution of a number of actual problems in the field of cement concrete technology problems. Particularly, the problems

  19. 城市生活垃圾焚烧飞灰中重金属的固化/稳定化处理%The Solidification/Stabilization Treatment Research of Heavy Metals from Fly Ash of Municipal Solid Waste Incineration

    周建国; 张曙光; 李萍; 冯旭; 刘俊鹏; 王云霞


    城市生活垃圾焚烧飞灰已被明确规定为危险废物,其中含有的大量有毒重金属对自然环境和人类生存会造成严重危害。综述了目前常用的水泥固化、烧结固化、熔融固化、药剂稳定化四种固化/稳定化垃圾焚烧飞灰中有毒重金属的方法,对比分析了各项技术的优缺点;对城市生活垃圾焚烧飞灰中重金属固化/稳定化处理的发展前景进行了展望,指出资源化利用是未来发展的必然趋势。%Fly ash from municipal solid waste incineration has been clearly defined as hazardous waste, which contains large amounts of toxic heavy metals that causes serious impact on natural environment and human survival. Four kinds of most commonly used solidification/stabilization technology such as cement solidification, sintering solidification, melting solidi-fication and chemical stabilization of toxic heavy metals from fly ash of municipal solid waste incineration are summarized. Meanwhile, the advantages and disadvantages of each treatment technology are comparatively analyzed. Finally, the pros-pects of toxic heavy metals’ solidification/stabilization are discussed, pointing out that the resource utilization is an inevitable trend for heavy metals’ solidification/stabilization from fly ash of municipal solid waste incineration in the future.

  20. Exploration of a capability-focused aerospace system of systems architecture alternative with bilayer design space, based on RST-SOM algorithmic methods.

    Li, Zhifei; Qin, Dongliang; Yang, Feng


    In defense related programs, the use of capability-based analysis, design, and acquisition has been significant. In order to confront one of the most challenging features of a huge design space in capability based analysis (CBA), a literature review of design space exploration was first examined. Then, in the process of an aerospace system of systems design space exploration, a bilayer mapping method was put forward, based on the existing experimental and operating data. Finally, the feasibility of the foregoing approach was demonstrated with an illustrative example. With the data mining RST (rough sets theory) and SOM (self-organized mapping) techniques, the alternative to the aerospace system of systems architecture was mapping from P-space (performance space) to C-space (configuration space), and then from C-space to D-space (design space), respectively. Ultimately, the performance space was mapped to the design space, which completed the exploration and preliminary reduction of the entire design space. This method provides a computational analysis and implementation scheme for large-scale simulation.

  1. A preliminary investigation of microcracks in the overcored borehole 210-020-RST1, 240 level of the Underground Research Laboratory

    McGregor, R.G.


    A section of borehole 210-020-RST1 was sampled and thin sections were cut in order to investigate the occurrence of microcracks within the borehole. The petrology of the sample was described and the presence of microcracks was noted. In total, 1894 microcracks were recorded during the investigation. Microcrack sets were defined on the basis of filling type (or lack of filling) and three-dimensional orientations attributed to the microcrack sets based on structural observations. Many microcrack sets are shown to have similar orientations to mesoscopic fractures observed within the Underground Research Laboratory (URL) lease area and within the URL subsurface. The relative age of observed microcracks, in terms of fillings, is from oldest to youngest: fluid-inclusion-filled fractures; unknown filled fractures; chlorite-filled fractures; and coeval in formation, chlorite-, hematite- and sericite-filled fractures. Fractures without filling are considered the youngest. Plates documenting some observed fractures are included. Biases in the generation and interpretation of the data are discussed and alternatives are mentioned. (auth)

  2. Evaluation of repetitive stimulation test (RST in 30 patients with Myasthenia Gravis, who were previously confirmed by clinical sign and tensilon test 1996-99

    "Ghabaee M


    Full Text Available est (RST is the most commonly used electrodiagnostic test to asses the defect of neuromuscular transmission, which is reported to be positive in the diffuse and restricted ocular forms 60-95% and 14-50%, respectively. In a cross-sectional study, to determine the efficacy of repetitive stimulation test in myasthenia gravis, we evaluated the results in 30 cases who were hospitalized in Imam Khomeini Hospital during 1996-1999. Patients were first selected clinically and then confirmed by Tensilon test.Various clinical types including generalized and restricted ocular forms with different severity and duration were entered in this study. Considering the fact that the positiveness of the test is enhanced by assessment of more muscle groups, we evaluated decremental response in the facial, proximal and distal muscles of limbs. 90% of patients had the generalized form of the disease, whereas ocular myasthenia gravis was seen only in 10% of the cases. 74% of females and 73% of males showed positive response (overall: 73.3%. No significant association was found between the positive response, and age and sex. Peaks of incidences of the disease for the males were in fourth and sixth decades and for the females in thired decades

  3. Grain Refinement and Improvement of Solidification Defects in Direct-Chill Cast Billets of A4032 Alloy by Melt Conditioning

    Li, Hu-Tian; Zhao, Pizhi; Yang, Rongdong; Patel, Jayesh B.; Chen, Xiangfu; Fan, Zhongyun


    Melt-conditioned, direct-chill (MC-DC) casting is an emerging technology to manipulate the solidification process by melt conditioning via intensive shearing in the sump during DC casting to tailor the solidification microstructure and defect formation. When using MC-DC casting technology in an industrial scale DC cast billet of an A4032 aluminum alloy, significant grain refinement and uniform microstructure can be achieved in the primary α-Al phase with fine secondary dendritic arm spacing (SDAS). Improved macrosegregation is quantitatively characterized and correlated with the suppression of channel segregation. The mechanisms for the prevention of channel segregation are attributed to the increased local cooling rate in the liquid-solid phase region in the sump and the formation of fine equiaxed dendritic grains under intensive melt shearing during MC-DC casting. A critical cooling rate has been identified to be around 0.5 to 1 K/s (°C/s) for the channel segregation to happen in the investigated alloy based on quantitative metallographic results of SDAS. Reduction and refinement of microporosity is attributed to the improved permeability in the liquid-solid phase region estimated by the Kozeny-Carman relationship. The potential improvement in the mechanical properties achievable in MC-DC cast billets is indicated by the finer and more uniform forging streamline in the forgings of MC-DC cast billet.

  4. Solidification fronts in large magma chambers: insights from the anomalies

    VanTongeren, J. A.


    The emplacement of hot viscous magma into the cold rigid crust causes a thermal disturbance within both the country rock and the magma. With time, heat loss from the molten interior to the walls causes solidification at the floor, roof and margins of the magma chamber. As is observed in both experiment and theory, in the absence of hydrothermal convection, the majority of heat is lost via conduction through the roof of the intrusion. In basaltic sills and layered mafic intrusions (LMIs), this solidification front is manifest in the deposition of mineral assemblages and compositions that become progressively more evolved from the floor of the intrusion upwards (the 'Layered Series'; LS) and from the roof downwards (the UBS) such that the most chemically evolved rocks are found in the interior of the magma body at a 'Sandwich Horizon'. The formation of a UBS, as typified by the Skaergaard Intrusion, is a natural outcome of the progression of the solidification front from the cold roof to the hot center of the magma chamber. There are, however, a few unique LMIs for which little or no UBS exists. Convection of the molten magma, reinjection and mixing of new magma, compaction of cumulates, and porous flow of interstitial liquid, among other processes, can affect the final location and composition of the most differentiated liquids; but ultimately, all are linked to the nature of heat loss from the magma chamber. In this study, I examine the thermal evolution of several classic LMIs as it is recorded in the extent of the preserved upper solidification front (or Upper Border Series; 'UBS'). For those intrusions that have experienced crystallization at the roof, such as the Skaergaard Intrusion, the development of a UBS reduces the temperature gradient at the roof and effectively slows the rate of heat loss from the main magma body. However, for those intrusions that do not have an UBS, such as the Bushveld Complex, the cooling rate is controlled only by the maximum rate

  5. Minimizing Segregation during the Controlled Directional Solidification of Dendric Alloys

    Grugel, Richard N.; Fedoseyev, Alex; Kim, Shin-Woo


    Gravity-driven convection induced in the liquid by density gradients of temperature or composition disrupts uniform dendritic growth during controlled directional solidification and promotes severe macrosegregation. The solute-rich region about the dendrite tip appears to play a pivotal role in channel initiation. Allen and Hunt referred to this region as an "initial transient" or dynamic region constituting steep concentration gradients. Experimental investigation also point to the role the tip region plays in developing microstructure. Hellawell and co-workers showed that flow-through dendritic channels could be effectively disrupted, and segregation minimized, during the gradient freezing of bulk castings by rotating the melt through a slight angle with respect to Earth's gravity vector. Adapting this principle to controlled directional solidification, it has been shown" that segregation in dendritic alloys can be minimized, and properties improved, by processing the sample near horizontal in conjunction with a slow axial rotation of the crucible. It is postulated that the observed microstructural uniformity arises by maintaining the developing solute field about the dendrite tip. Solute rejected during vertical directional solidification will rise or sink parallel to the primary dendrite arms during axial rotation setting the stage for accumulation, instabilities, and segregation. In contrast, during horizontal growth, the rejected solute will sink or rise perpendicular to the primary dendrite. Now, in the presence of a slight axial rotation, solute that was initially sinking (or rising) will find itself above (or below) its parent dendrite, i.e., still about the tip region. The following is intended to experimentally demonstrate the viability of this concept in coordination with a model that gives predictive insight regarding solute distribution about growing dendrites. Alloys based on the lead-tin eutectic system were used in this study. The system is well

  6. Effect of solidification parameters on the secondary dendrite arm spacing in MAR M-247 superalloy determined by a novel approach

    Milenkovic S.; Rahimian M.; Sabirov I.; Maestro L.


    The effect of solidification parameters on the secondary dendrite arm spacing in a MAR-M247 Ni-based superalloy has been studied by a novel approach, based on physical simulation of melting/solidification experiment with a constant cooling rate and variable temperature gradient. The applied experimental method proved to be efficient as it yielded a spread of microstructures corresponding to a range of well controlled solidification rates in a single melting/solidification experiment. In addit...

  7. Containerless Solidification and Characterization of Industrial Alloys (NEQUISOL)

    Ilbagi, A.; Henein, H.; Chen, J.; Herlach, D. M.; Lengsdorf, R.; Gandin, Ch-A.; Tourret, D.; Garcia-Escorial, A.


    Containerless solidification using electromagnetic levitator (EML), gas atomization and an instrumented drop tube, known as impulse atomization is investigated for Al-Fe and Al-Ni alloys. The effects of primary phase and eutectic undercooling on the microstructure of Al-Fe alloys are investigated using the impulse drop tube and parabolic flight. The TEM characterization on the eutectic microstructure of impulse-atomized Al-Fe powders with two compositions showed that the metastable AlmFe formed in these alloys. Also, the growth undercooling that the dendritic front experiences during the solidification of the droplet resulted in variation of dendrite growth direction from to . For Al-4 at%Fe, it was found that in reduced-gravity and in the impulse-atomized droplets the primary intermetallic forms with a flower-like morphology, whereas in the terrestrial EML sample it has a needle like morphology. For Al-Ni, the effect of primary phase undercooling on dendrite growth velocity under terrestrial and reduced-gravity condition is discussed. It is shown that under terrestrial conditions, in the Ni-rich alloys with increasing undercooling the growth velocity increases, whereas in the Al-rich alloys the growth velocity decreases. However, the Al-rich alloy that was studied in reduced-gravity showed similar behavior to that of Ni-rich alloys. Furthermore, the effect of cooling rate on the phase fractions and metastable phase formation of impulse-atomized Al-Ni alloys is compared with EML. A microsegregation model for the solidification of Al-Ni alloys is applied to impulse atomized powders. The model accounts for the occurrence of several phase transformations, including one or several peritectic reactions and one eutectic reaction.

  8. Development of Stable Solidification Method for Insoluble Ferrocyanides-13170

    Ikarashi, Yuki; Masud, Rana Syed; Mimura, Hitoshi [Dept. of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Aramaki-Aza-Aoba6-6-01-2, Sendai, 980-8579 (Japan); Ishizaki, Eiji; Matsukura, Minoru [UNION SHOWA K.K. 17-20, Mita 2-chome, Minato-ku, Tokyo 108-0073 (Japan)


    The development of stable solidification method of insoluble ferrocyanides sludge is an important subject for the safety decontamination in Fukushima NPP-1. By using the excellent immobilizing properties of zeolites such as gas trapping ability and self-sintering properties, the stable solidification of insoluble ferrocyanides was accomplished. The immobilization ratio of Cs for K{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O saturated with Cs{sup +} ions (Cs{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O) was estimated to be less than 0.1% above 1,000 deg. C; the adsorbed Cs{sup +} ions are completely volatilized. In contrast, the novel stable solid form was produced by the press-sintering of the mixture of Cs{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O and zeolites at higher temperature of 1,000 deg. C and 1,100 deg. C; Cs volatilization and cyanide release were completely depressed. The immobilization ratio of Cs, under the mixing conditions of Cs{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O:CP= 1:1 and calcining temperature: 1,000 deg. C, was estimated to be nearly 100%. As for the kinds of zeolites, natural mordenite (NM), clinoptilolite (CP) and Chabazite tended to have higher immobilization ratio compared to zeolite A. This may be due to the difference in the phase transformation between natural zeolites and synthetic zeolite A. In the case of the composites (K{sub 2-X}Ni{sub X/2}[NiFe(CN){sub 6}].nH{sub 2}O loaded natural mordenite), relatively high immobilization ratio of Cs was also obtained. This method using zeolite matrices can be applied to the stable solidification of the solid wastes of insoluble ferrocyanides sludge. (authors)

  9. Analysis of Solidification in the Presence of High Rayleigh Number Convection in an Enclosure


    A simple and convenient analysis of the process of time-dependent solidification in an enclosed liquid cooled from the side in the presence of natural convection is presented.the influence of each parameter on the process of solidification is carried out systematically,The accuracy of this model is justified by comparing its predicting values with the previous results.

  10. Feasibility of integrated seed making and directional solidification of TiAl alloy using cold crucible

    ZHANG Cheng-jun; FU Heng-zhi; XU Da-ming; GUO Jing-jie; BI Wei-sheng; SU Yan-qing


    A new seed making method with cold crucible by power off technique was proposed. The cold crucible quenched seed with columnar structure has a similar cross-section shape as that of the cold crucible, and can be directly used for the directional solidification processes. The proposed method can significantly simplify the seeded directional solidification process and avoid the contamination from the seed machining.

  11. Nucleation and solidification of thin walled ductile iron - Experiments and numerical simulation

    Pedersen, Karl Martin; Tiedje, Niels Skat


    Investigation of solidification of thin walled ductile cast iron has been performed based on experiments and numerical simulation. The experiments were based on temperature and microstructure examination. Results of the experiments have been compared with a 1-D numerical solidification model...

  12. Proceedings of the 1st workshop on radioactive waste treatment technologies, October 28, 1997 Taejon, Korea



    This proceedings describes the volume reduction of radioactive waste, the radioactive waste treatment technology, the decontamination and decommissioning, and the incineration and solidification of radioactive waste. Twenty two papers are submitted.

  13. Isothermal solidification based packaging of biosensors at low temperatures

    Sharma, R.P., E-mail: [Electronic Science Department, Kurukshetra University, Kurukshetra-136119, Haryana (India); Central Electronics Engineering Research Institute (CEERI)/Council of Scientific and Industrial Research (CSIR), Pilani-333031, Rajasthan (India); Khanna, P.K., E-mail: pkk@ceeri.ernet.i [Central Electronics Engineering Research Institute (CEERI)/Council of Scientific and Industrial Research (CSIR), Pilani-333031, Rajasthan (India); Kumar, D., E-mail: [Electronic Science Department, Kurukshetra University, Kurukshetra-136119, Haryana (India)


    Thick film Au printed square contact pads are interconnected to Cu substrates at constant pressure and temperature using the isothermal solidification of Bi-In alloy on the joining surfaces. The effect of reaction time on the mechanical strength of the package has been analyzed. Thermal stability of the fabricated specimens have been measured and discussed. The delaminated surfaces examined optically reveal the morphology of the metallization zones on the joining substrates. The scanning electron microscopy of these surfaces is reported in this paper. Tests for thermal shock, pH resistivity and shelf life have been carried out to predict the reliability of the packaging for long term applications.

  14. Numerical Simulation of Dendrite Evolution during Solidification Process

    LI Qiang; GUO Qiao-yi; REN Chuan-fu


    In order to precisely describe the dendrite evolution during solidification process, especially in microscale, a continuous method is presented to deal with the discontinuous physical properties beside the solid/liquid interface. In this method, the physical properties are used as averaging physical properties of solid phase and liquid phase in the interface zone, which can smooth the property gap between solid and liquid phases, and make the properties from liquid phase to solid phase. The simulated results show that the method can represent the sidebranches and the solute micro-segregation well.

  15. Divorced Eutectic Solidification of Mg-Al Alloys

    Monas, Alexander; Shchyglo, Oleg; Kim, Se-Jong; Yim, Chang Dong; Höche, Daniel; Steinbach, Ingo


    We present simulations of the nucleation and equiaxed dendritic growth of the primary hexagonal close-packed -Mg phase followed by the nucleation of the -phase in interdendritic regions. A zoomed-in region of a melt channel under eutectic conditions is investigated and compared with experiments. The presented simulations allow prediction of the final properties of an alloy based on process parameters. The obtained results give insight into the solidification processes governing the microstructure formation of Mg-Al alloys, allowing their targeted design for different applications.

  16. Micro/macro solidification modeling of columnar eutectic growth

    Judson, Ward Michael


    A general multidimensional model of alloy solidification is presented in which a velocity-dependent freezing temperature is coupled with the macroscale energy equation. The velocity dependence of the freezing temperature ( Tf˜v ) results from the microscale species diffusion for microstructures with coupled eutectic growth. At solidification rates ( ˜ 1--10 mm/s) that are representative of gravity permanent mold and die casting processes, consideration of the nonequilibrium conditions at the interface affects the prediction of the macroscale thermal field. Near-eutectic alloys freeze with a macroscopically discrete solid-liquid interface at a temperature below the equilibrium eutectic temperature. The model is illustrated with unidirectional solidification of a near-eutectic alloy in a finite domain and solved numerically with a fixed-grid Galerkin finite element method. The numerical algorithm includes inexpensive steps to compute the interface speed explicitly. By nondimensionalizing the governing equations the effect of coupled eutectic growth on heat transport is clearly identified so that the model's sensitivity to important parameters can be investigated. Additionally, the average eutectic spacing can be determined with the temperature field, rather than post-determination from a standard, uncoupled solution of the energy equation. The eutectic coupling results indicate that the predicted solid-liquid interface location lags behind the uncoupled solution; therefore, decreasing the amount of solid formed, increasing the total solidification time, and increasing the average eutectic spacing. A procedure is also illustrated for computing mechanical properties using experimental correlations and the computed interface velocity history. The effect of the eutectic undercooling is then studied in a square domain and a realistic three-dimensional production casting geometry. In order to address the multidimensional cases, a phase-field formulation is developed

  17. Fractal growth in impurity-controlled solidification in lipid monolayers

    Fogedby, Hans C.; Sørensen, Erik Schwartz; Mouritsen, Ole G.


    A simple two-dimensional microscopic model is proposed to describe solidifcation processes in systems with impurities which are miscible only in the fluid phase. Computer simulation of the model shows that the resulting solids are fractal over a wide range of impurity concentrations and impurity...... diffusional constants. A fractal-forming mechanism is suggested for impurity-controlled solidification which is consistent with recent experimental observations of fractal growth of solid phospholipid domains in monolayers. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....

  18. Instabilities in rapid solidification of multi-component alloys

    Altieri, Anthony L.; Davis, Stephen H.


    Rapid solidification of multi-component liquids occurs in many modern applications such as additive manufacturing. In the present work the interface departures from equilibrium consist of the segregation coefficient and liquidus slope depending on front speed, the one-sided, frozen-temperature approximation, and the alloy behaving as the superposition of individual components. Linear-stability theory is applied, showing that the cellular and oscillatory instabilities of the binary case are modified. The addition of components tends to destabilize the interface while the addition of a single large-diffusivity material can entirely suppress the oscillatory mode. Multiple minima in the neutral curve for the cellular mode occur.

  19. Algorithms of optimum location of sensors for solidification parameters estimation

    J. Mendakiewicz


    Full Text Available The algorithms of optimal sensor location for estimation of solidification parameters are discussed. These algorithms base on the Fisher Information Matrix and A-optimality or D-optimality criterion. Numerical examples of planning algorithms are presented and next foroptimal position of sensors the inverse problems connected with the identification of unknown parameters are solved. The examplespresented concern the simultaneous estimation of mould thermophysical parameters (volumetric specific heat and thermal conductivityand also the components of volumetric latent heat of cast iron.

  20. Cellular instability in rapid directional solidification - Bifurcation theory

    Braun, R. J.; Davis, S. H.


    Merchant and Davis performed a linear stability analysis on a model for the directional solidification of a dilute binary alloy valid for all speeds. The analysis revealed that nonequilibrium segregation effects modify the Mullins and Sekerka cellular mode, whereas attachment kinetics has no effect on these cells. In this paper, the nonlinear stability of the steady cellular mode is analyzed. A Landau equation is obtained that determines the amplitude of the cells. The Landau coefficient here depends on both nonequilibrium segregation effects and attachment kinetics. This equation gives the ranges of parameters for subcritical bifurcation (jump transition) or supercritical bifurcation (smooth transition) to cells.

  1. Competitive growth of high purity aluminum grains in directional solidification

    ZHANG Jiao; SHU Da; WANG De-lin; SUN Bao-de; CHEN Gang


    A self-made directional solidification setup was used to prepare high purity aluminum ingots of 100mm in diameter. The morphology of the growth interface was detected by SEM and AFM, and the grain lattice orientation was detected by XRD. The results indicate that the grains suffer competitive growth under any conditions in experiments. The lattice orientation of the preferred grains is determined by the flow field above the solid-liquid interface. The horizontal lattice position does not change during the growth process. However, the lattice orientation in the growth direction varies with the growth velocity and approaches to [100]gradually during the growth process.

  2. Boundary-layer model of pattern formation in solidification

    Ben-Jacob, E.; Goldenfeld, N.; Langer, J. S.; Schon, G.


    A model of pattern formation in crystal growth is proposed, and its analytic properties are investigated. The principal dynamical variables in this model are the curvature of the solidification front and the thickness (or heat content) of a thermal boundary layer, both taken to be functions of position along the interface. This model is mathematically much more tractable than the realistic, fully nonlocal version of the free-boundary problem, and still recaptures many of the features that seem essential for studying dendritic behavior, for example. Preliminary numerical solutions produce snowflakelike patterns similar to those seen in nature.

  3. Rapid Solidification of AB{sub 5} Hydrogen Storage Alloys

    Gulbrandsen-Dahl, Sverre


    This doctoral thesis is concerned with rapid solidification of AB{sub 5} materials suitable for electrochemical hydrogen storage. The primary objective of the work has been to characterise the microstructure and crystal structure of the produced AB{sub 5} materials as a function of the process parameters, e.g. the cooling rate during rapid solidification, the determination of which has been paid special attention to. The thesis is divided into 6 parts, of which Part I is a literature review, starting with a short presentation of energy storage alternatives. Then a general review of metal hydrides and their utilisation as energy carriers is presented. This part also includes more detailed descriptions of the crystal structure, the chemical composition and the hydrogen storage properties of AB{sub 5} materials. Furthermore, a description of the chill-block melt spinning process and the gas atomisation process is given. In Part II of the thesis a digital photo calorimetric technique has been developed and applied for obtaining in situ temperature measurements during chill-block melt spinning of a Mm(NiCoMnA1){sub 5} hydride forming alloy (Mm = Mischmetal of rare earths). Compared with conventional colour transmission temperature measurements, this technique offers a special advantage in terms of a high temperature resolutional and positional accuracy, which under the prevailing experimental conditions were found to be {+-}29 K and {+-} 0.1 mm, respectively. Moreover, it is shown that the cooling rate in solid state is approximately 2.5 times higher than that observed during solidification, indicating that the solid ribbon stayed in intimate contact with the wheel surface down to very low metal temperatures before the bond was broken. During this contact period the cooling regime shifted from near ideal in the melt puddle to near Newtonian towards the end, when the heat transfer from the solid ribbon to the wheel became the rate controlling step. In Part III of the

  4. Permeability in a state of partial solidification of aqueous solution

    Okada, Masashi; Kang, Chaedong; Okiyama, Haruhiko

    A mushy region was formed by solidifying NaCl aqueous solution in a circular tube or a rectangular tube. The measurements of permeability were performed by changing volume fraction of liquid region in the mushy region. The dendritic ice in the solidification process was observed with a CCD microscope. The following results were obtained. The permeability increases with the volume fraction of liquid phase, and decreases with increasing the super-cooling degree of the solution or increasing the initial concentration of the solution, and is constant after the mushy region was formed. The arm space of dendrite becomes narrower as the super-cooling degree of the solution increases.

  5. Crystal Growth and Fluid Mechanics Problems in Directional Solidification

    Tanveer, Saleh A.; Baker, Gregory R.; Foster, Michael R.


    Our work in directional solidification has been in the following areas: (1) Dynamics of dendrites including rigorous mathematical analysis of the resulting equations; (2) Examination of the near-structurally unstable features of the mathematically related Hele-Shaw dynamics; (3) Numerical studies of steady temperature distribution in a vertical Bridgman device; (4) Numerical study of transient effects in a vertical Bridgman device; (5) Asymptotic treatment of quasi-steady operation of a vertical Bridgman furnace for large Rayleigh numbers and small Biot number in 3D; and (6) Understanding of Mullins-Sererka transition in a Bridgman device with fluid dynamics is accounted for.

  6. Verification of a binary fluid solidification model in the finite-volume flow solver

    Waclawczyk, Tomasz


    The aim of this paper is to verify the new numerical implementation of a binary fluid, heat conduction dominated solidification model. First, we extend a semi-analytical solution to the heat diffusion equation, next, the range of its applicability is investigated. It was found that the linearization introduced to the heat diffusion equation negatively affects the ability to predict solidus and liquidus lines positions whenever the magnitude of latent heat of fusion exceeds a certain value. Next, a binary fluid solidification model is coupled with a flow solver, and is used in a numerical study of Al-4.1%Cu alloy solidification in a two-dimensional rectangular cavity. An accurate coupling between the solidification model and the flow solver is crucial for the correct forecast of solidification front positions and macrosegregation patterns.

  7. Effect of Mould Wall Thickness on Rate of Solidification of Centrifugal Casting



    Full Text Available In Centrifugal Casting process the centrifugal force presses the metal against the inner wall of the metal mould, resulting in rapid solidification of the molten metal. However the solidification structures like structural uniformity and structural character of the solidified metal of centrifugal casting is of great importance, regarding to its mechanical properties. The solidification time of the casting is dependent upon the various parameters like speed ofrotation of the mold, mould wall temperature, heat transfer coefficient at the metal-mold interface, mould wall thickness, material of the mould and so on. In this paper experimental study of effect of mould wall thickness on solidification of the centrifugal casting has been discussed. As the mould wall thickness increases, due to the chilling effect, the solidification time decreases. Fine grains are observed in castings produced in thick walled mould and coarse grains are observed in thin walled moulds. Brinel Hardness of the casting was measured.

  8. Effect of Coating on Instantaneous Interracial Heat Transfer During Near-Rapid Solidification

    ZHANG Wei; YU Yan; FANG Yuan; LI Jian-guo


    For many rapid or near-rapid solidification processes, the interracial heat transfer between the melt and the substrate is a key issue on the cooling and solidification rate of castings. For the purpose of controlling and adjusting of the interfacial thermal resistance, the effects of C/BN, Zn and organic coatings on the instantaneous interracial heat flux and the solidified structure of AISI304 stainless steel solidification on copper substrate have been investiga- ted by using an experimental simulator. The results show that C/BN coatings can improve the uniformity of heat flux and solidified structure; Zn coating can increase the heat flux and solidification rate in the growth stage of the solidified shell; organic coating will decrease the heat flux and the solidification rate and make re-melted structure on the surface of the solidified shell.

  9. Solidification microstructure selection of the peritectic Nd-Fe-B alloys

    ZHONG Hong; LI ShuangMing; L(U) HaiYan; LIU Lin; ZOU GuangRong; FU HengZhi


    Bridgman directional solidification and laser remelting experiments were carried out on Nd11.76Fe82.36B5.88 and Nd13.5Fe79.75B6.75 alloys. Microstructure evolutions along with solidification parameters (temperature gradient G, growth velocity V and initial alloy composition C0) were investigated. A solidification microstructure selection map was established, based on the consideration of solidification characteristics of peritectic T1 phase. In Bridgman directional solidification experiments, with the increasing growth velocities, the morphology of T1 phase changed from plane front or faceted plane front to dendrites. In laser remelting experiments, a transition from primary γ-Fe dendrites to T1 dendrites was found. Theoretical predictions are in good agreement with experimental results.

  10. Fabrication of directional solidification components of nickel-base superalloys by laser metal forming

    Liping Feng; Weidong Huang; Darong Chen; Xin Lin; Haiou Yang


    Straight plates, hollow columns, ear-like blade tips, twist plates with directional solidification microstructure made of Rene 95 superalloys were successfully fabricated on Nickel-base superalloy and DD3 substrates, respectively. The processing conditions for production of the parts with corresponding shapes were obtained. The fabrication precision was high and the components were compact. The solidification microstructure of the parts was analyzed by optical microscopy. The results show that the solidification microstructure is composed of columnar dendrites, by epitaxial growth onto the directional solidification substrates. The crystallography orientation of the parts was parallel to that of the substrates. The primary arm spacing was about 10 μm, which is in the range of superfine dendrites, and the secondary arm was small or even degenerated. It is concluded that the laser metal forming technique provides a method to manufacture directional solidification components.

  11. Solidification analysis of a centrifugal atomizer using the Al-32.7wt.% Cu alloy

    Osborne, Matthew G. [Iowa State Univ., Ames, IA (United States)


    A centrifugal atomizer (spinning disk variety) was designed and constructed for the production of spherical metal powders, 100-1,000 microns in diameter in an inert atmosphere. Initial atomization experiments revealed the need for a better understanding of how the liquid metal was atomized and how the liquid droplets solidified. To investigate particle atomization, Ag was atomized in air and the process recorded on high-speed film. To investigate particle solidification, Al-32.7 wt.% Cu was atomized under inert atmosphere and the subsequent particles were examined microscopically to determine solidification structure and rate. This dissertation details the experimental procedures used in producing the Al-Cu eutectic alloy particles, examination of the particle microstructures, and determination of the solidification characteristics (e.g., solidification rate) of various phases. Finally, correlations are proposed between the operation of the centrifugal atomizer and the observed solidification spacings.

  12. Solidification microstructure selection of the peritectic Nd-Fe-B alloys


    Bridgman directional solidification and laser remelting experiments were carried out on Nd11.76Fe82.36B5.88 and Nd13.5Fe79.75B6.75 alloys.Microstructure evolutions along with solidification parameters(temperature gradient G,growth velocity V and initial alloy composition C0)were investigated.A solidification microstructure selection map was established,based on the consideration of solidification characteristics of peritectic T1 phase.In Bridgman directional solidification experiments,with the increasing growth velocities,the morphology of T1 phase changed from plane front or faceted plane front to dendrites.In laser remelting experiments,a transition from primary γ-Fe dendrites to T1 dendrites was found.Theoretical predictions are in good agreement with experimental results.

  13. "In vivo" toxicity of a truncated version of the Drosophila Rst-IrreC protein is dependent on the presence of a glutamine-rich region in its intracellular domain



    Full Text Available The roughest-irregular chiasm C ( rst-irreC gene of Drosophila melanogaster encodes a transmembrane glycoprotein containing five immunoglobulin-like domains in its extracellular portion and an intracytoplasmic tail rich in serine and threonine as well some conserved motifs suggesting signal transduction activity. In the compound eye, loss-of-function rst-irreC mutants lack the characteristic wave of programmed cell death happening in early pupa and which is essential for the elimination of the surplus interommatidial cells. Here we report an investigation on the role played by the Rst-irreC molecule in triggering programmed cell death. "In vivo" transient expression assays showed that deletion of the last 80 amino acids of the carboxyl terminus produces a form of the protein that is highly toxic to larvae. This toxicity is suppressed if an additional 47 amino acid long, glutamine-rich region ("opa-like domain", is also removed from the protein. The results suggest the possibility that the opa-like domain and the carboxyl terminus act in concert to modulate rst-irreC function in apoptosis, and we discuss this implication in the context of the general mechanisms causing glutamine-rich neurodegenerative diseases in humans.O gene roughest-irregular chiasm C ( rst-irreC de Drosophila melanogaster, codifica uma glicoproteína transmembranar contendo cinco domínios semelhantes a imunoglobulina em sua porção extracelular e uma cauda intracitoplasmática rica em serina e treonina, assim como alguns sequências conservadas que sugerem atividade transdutora de sinais. No olho composto, mutantes rst-irreC de perda de função não apresentam uma característica "onda" de morte celular programada que ocorre no início do período pupal e que é essencial para a eliminação de células interomatidiais em excesso. Aqui descrevemos uma investigação sobre o papel desempenhado pela molécula Rst-IrreC no disparo da morte celular programada. Ensaios de

  14. Solidification/Stabilization of Elemental Mercury Waste by Amalgamation

    Yim, S. P.; Ahn, B. G.; Lee, H. J.; Shon, J. S.; Chung, H.; Kim, K. J.; Lee, C. K.


    Experiments on solidification of elemental mercury waste were conducted by amalgamation with several metal powders such as copper, zinc, tin, brass and bronze. Unlike the previous studies which showed a dispersible nature after solidification, the waste forms were found to possess quite large compressive strengths in both copper and bronze amalgam forms. The durability was also confirmed by showing very minor changes of strength after 90 days of water immersion. Leachability from the amalgam forms is also shown to be low: measured mercury concentration in the leachate by the Toxicity Characteristic Leaching Procedure (TCLP) was well below the Environmental Protection Agency (EPA) limit. Long term leaching behavior by Accelerated Leach Test (ALT) has shown that the leaching process was dominated by diffusion and the effective diffusion coefficient was quite low (around 10-19 cm2/sec). The mercury vapor concentration from the amalgam forms were reduced to a 20% level of that for elemental mercury and to one-hundredth after 3 months.

  15. Numerical modelling of the binary alloys solidification with solutal undercooling

    T. Skrzypczak


    Full Text Available In thc papcr descrip~ion of mathcmn~icaI and numerical modcl of binay alloy sot idification is prcscntcd. Mctal alloy consisting of maincomponent and solulc is introduced. Moving, sharp solidification rmnt is assumcd. Conaitulional undcrcooling phcnomcnon is tnkcn intoconsidcralion. As a solidifica~ionf ront advances, solutc is rcdistributcd at thc intcrfacc. Commonly, solutc is rejccted into Itlc liquid. whcrcit accumuIatcs into solittc boundary laycr. Depending on thc tcmpcrature gradient, such tiquid may be undcrcoolcd hclow its mclting point,cvcn though it is hot~crth an liquid at thc Front. This phcnomcnon is orten callcd constitutional or soIr~talu ndcrcool ing, to cmphasizc that itariscs from variations in solutal distribution or I iquid. An important conscqucncc of this accurnulntion of saIutc is that it can cause thc frontto brcak down into cclls or dendri~csT. his occurs bccausc thcrc is a liquid ahcad of thc front with lowcr solutc contcnt, and hcncc a highcrme1 ting tcmpcraturcs than liquid at thc front. In rhc papcr locarion and shapc of wndcrcoolcd rcgion dcpcnding on solidification pararnctcrsis discussed. Nurncrical mcthod basing on Fini tc Elelncnt Mctbod (FEM allowi~lgp rcdiction of breakdown of inoving planar front duringsolidification or binary alloy is proposed.

  16. Modified enthalpy method for the simulation of melting and solidification

    Niranjan N Gudibande; Kannan N Iyer


    Enthalpy method is commonly used in the simulation of melting and solidification owing to its ease of implementation. It however has a few shortcomings. When it is used to simulate melting/solidification on a coarse grid, the temperature time history of a point close to the interface shows waviness. While simulatingmelting with natural convection, in order to impose no-slip and impermeability boundary conditions, momentum sink terms are used with some arbitrary constants called mushy zone constants. The values of these are very large and have no physical basis. Further, the chosen values affect the predictions and hence have to be tuned for satisfactory comparison with experimental data. To overcome these deficiencies, a new cell splitting method under the framework of the enthalpy method has been proposed. This method does not produce waviness nor requires mushy zone constants for simulating melting with natural convection. The method is then demonstrated for a simple onedimensional melting problem and the results are compared with analytical solutions. The method is then demonstrated to work in two-dimensions and comparisons are shown with analytical solutions for problems with planar and curvilinear interfaces. To further benchmark the present method, simulations are performed for melting in a rectangular cavity with natural convection in the liquid melt. The solid–liquid interface obtained is compared satisfactorily with the experimental results available in literature.

  17. Simulation of spreading with solidification: assessment synthesis of Thema code

    Spindler, B.; Veteau, J.M. [CEA Grenoble, Direction de l' Energie Nucleaire, Dept. de Technologie Nucleaire, Service d' Etudes Thermohydrauliques et Technologiques, 38 (France)


    After a presentation of the models included in THEMA code, which simulates the spreading of a fluid with solidification, the whole assessment calculations are presented. The first series concerns the comparison with analytical or numerical solutions: dam break, conduction for the heat transfer in the substrate, crust growth. The second series concerns the comparison with the CORINE isothermal tests (simulating fluid at low temperature). The third series concerns the CORINE tests with heat transfer. The fourth series concerns the tests with simulating materials at medium or high temperature (RIT, KATS). The fifth series concerns the tests with prototypical materials (COMAS, FARO, VULCANO). Finally the blind simulations of the ECOKATS tests are presented. All the calculations are performed with the same physical models (THEMA version 2.5), without any variable tuning parameter according to the test under consideration. Sensitivity studies concern the influence of the viscosity model in the solidification interval, and for the tests with prototypical materials the inlet temperature and the solid fraction. The relative difference between the calculated and measured spreading areas is generally less than 20 % except for the test with prototypical materials, for which the assessment is not easy due to the large experimental uncertainties. The level of validation of THEMA is considered as satisfactory, taking into account the required accuracy. (authors)

  18. Wax solidification of drying agents containing tritiated water

    Mishikawa, M.; Kido, H.


    It is necessary to immobilize the tritium not to give any impact on the environmental biosphere because tritium may give profound effects in the metabolic pathway. One of the most probable methods of immobilizing tritium would be incorporation of tritiated water in solid forms. Any drying or dehydration technique would be effective in a tritium cleanup system for off-gas streams containing tritium or tritiated water. Commonly used drying agents such as activated alumina, silica gel, molecular sieves and calcium sulfate are of value for removal of water vapour from air or other gases. For long term tritium storage, however, these adsorptive materials should be enveloped to prevent contact with water or water vapour because the rate of leaching, evaporation or diffusion of tritium from these porous materials is so large. The beeswax solidification method of the packed bed of drying agents adsorbing tritiated water is developed in this study, where the wax solidification procedure is performed by pouring the melt of wax into the void space of the packed bed of the drying agents and successive gradual cooling. The observed values of diffusivity or permeability of tritium in the wax solidified materials are about one-thousandth of those obtained for the cement block. Effect of coating on the rate of leaching is also discussed.

  19. Stability of a directional solidification front in subdiffusive media.

    Hamed, Mohammad Abu; Nepomnyashchy, Alexander A


    The efficiency of crystal growth in alloys is limited by the morphological instability, which is caused by a positive feedback between the interface deformation and the diffusive flux of solute at the front of the phase transition. Usually this phenomenon is described in the framework of the normal diffusion equation, which stems from the linear relation between time and the mean squared displacement of molecules 〈x2(t)〉∼K1t (K1 is the classical diffusion coefficient) that is characteristic of Brownian motion. However, in some media (e.g., in gels and porous media) the random walk of molecules is hindered by obstacles, which leads to another power law, 〈x2(t)〉∼Kαtα, where 0directional solidification front in the case of an anomalous diffusion. Linear stability of a moving planar directional solidification front is studied, and a generalization of the Mullins-Sekerka stability criterion is obtained. Also, an asymptotic nonlinear long-wave evolution equation of Sivashinsky's type, which governs the cellular structures at the interface, is derived.

  20. A study on polypropylene encapsulation and solidification of textile sludge.

    Kumari, V Krishna; Kanmani, S


    The textile sludge is an inevitable solid waste from the textile wastewater process and is categorised under toxic substances by statutory authorities. In this study, an attempt has been made to encapsulate and solidify heavy metals and dyes present in textile sludge using polypropylene and Portland cement. Sludge samples (2 Nos.) were characterized for pH (8.5, 9.5), moisture content (1.5%, 1.96%) and chlorides (245mg/L, 425.4mg/L). Sludge samples were encapsulated into polypropylene with calcium carbonate (additive) and solidified with cement at four different proportions (20, 30, 40, 50%) of sludge. Encapsulated and solidified cubes were made and then tested for compressive strength. Maximum compressive strength of cubes (size, 7.06cm) containing sludge (50%) for encapsulation (16.72 N/mm2) and solidification (18.84 N/mm2) was more than that of standard M15 mortar cubes. The leachability of copper, nickel and chromium has been effectively reduced from 0.58 mg/L, 0.53 mg/L and 0.07 mg/L to 0.28mg/L, 0.26mg/L and BDL respectively in encapsulated products and to 0.24mg/L, BDL and BDL respectively in solidified products. This study has shown that the solidification process is slightly more effective than encapsulation process. Both the products were recommended for use in the construction of non-load bearing walls.

  1. Investigation of solidification dynamics of Zr-based alloys

    Kobold, Raphael; Herlach, Dieter [Institut fuer Materialphysik im Weltraum, Deutsches Zentrum fuer Luft- und Raumfahrt, 51170 Koeln (Germany); Ruhr-Universitaet Bochum, 44780 Bochum (Germany)


    In contrast to experiments with most undercooled binary alloys the velocity of dendritic growth of a Cu50Zr50 alloy does not increase monotonically with undercooling but passes through a maximum and then decreases. To study this behaviour we investigate Zr-based alloys such as CuZr, NiZr and NiZrAl with Zirconium concentrations ranging from 36 to 64 at.% including eutectic and intermetallic phases. We use electrostatic levitation technique to melt and undercool samples with a diameter of 2-3 mm under ultra-high-vacuum conditions. Containerless processing is an effective tool for undercooling metallic melts far below their equilibrium melting temperatures since heterogeneous nucleation on container walls is completely avoided. During crystallisation of the undercooled melt the heat of crystallisation is released. The rapid increase of the temperature at the solid-liquid interface makes the solidification front visible. The velocities of the solidification front are recorded by using a high-speed camera with a maximum rate of 50.000 frames per second and are analyzed with a software for optical ray tracing. Furthermore, we try to model the growth velocity vs. the undercooling temperature and perform sample EBSD analysis with a scanning electron microscope.

  2. Rapid solidification of undercooled Al-Cu-Si eutectic alloys

    RUAN Ying; WEI BingBo


    Under the conventional solidification condition,a liquid aluminium alloy can be hardly undercooled because of oxidation.In this work,rapid solidification of an undercooled liquid Al,80.4Cu,13.6Si,6 ternary eutectic alloy was realized by the glass fluxing method combined with recycled superheating.The re-lationship between superheating and undercooling was investigated at a certain cooling rate of the alloy melt.The maximum undercooling is 147 K (0.18 TE).The undercooled ternary eutectic is composed of α(Al) solid solution,(Si) semiconductor and β(CuAl,2) intermetallic compound.In the (Al+Si+θ) ternary eutectic,(Si) faceted phase grows independently,while (Al) and θ non-faceted phases grow coopera-tively in the lamellar mode.When undercooling is small,only (Al) solid solution forms as the leading phase.Once undercooling exceeds 73 K,(Si) phase nucleates firstly and grows as the primary phase.The alloy microstructure consists of primary (Al) dendrite,(Al+9) pseudobinary eutectic and (Al+Si+θ) ternary eutectic at small undercooling,while at large undercooling primary (Si) block,(Al+θ) pseudo-binary eutectic and (Al+Si+θ) ternary eutectic coexist.As undercooling increases,the volume fraction of primary (Al) dendrite decreases and that of primary (Si) block increases.

  3. Energetics of nonequilibrium solidification in Al-Sm

    Zhou, S. H.; Napolitano, R. E.


    Solution-based thermodynamic modeling, aided by first-principles calculations, is employed here to examine phase transformations in the Al-Sm binary system which may give rise to product phases that are metastable or have a composition that deviates substantially from equilibrium. In addition to describing the pure undercooled Al liquid with a two-state model that accounts for structural ordering, thermodynamic descriptions of the fcc phase, and intermediate compounds ( Al4Sm-β , Al11Sm3-α , Al3Sm-δ , and Al2Sm-σ ) are reanalyzed using special quasirandom structure and first-principles calculations. The possible phase compositions are presented over a range of temperatures using a “Baker-Cahn” analysis of the energetics of solidification and compared with reports of rapid solidification. The energetics associated with varying degrees of chemical partitioning are quantified and compared with experimental observations of the metastable Al11Sm3-α primary phase and reports of amorphous solids.

  4. Solidification of Trapped Liquid in Rocks and Crystals

    Morse, S. A.


    Trapped liquid in an igneous cumulate solidifies over a range of time and temperature that can be retrieved by use of the lever rule in binary solutions applied to plagioclase using the range in the An content found for the individual rock studied. The resident crystals in the cumulate count in the phase equilibria as though deposited by the resident liquid in pure fractional crystallization at the moment of trapping. The An range (Morse JPet 53:891, 2012) when measured in sufficient detail, defines the solidification history. The instantaneous solid composition along the solidus defines the zoning of the plagioclase as it follows the trapped liquid on the liquidus. The reference bulk composition of the trapped liquid is given by an intercept on the initial solid-liquid lever, defined by the fraction of plagioclase in the trapped parent magma times the residual porosity. The mafic fraction is assumed to solidify by reaction independently of the plagioclase zoning. The residual porosity is calculated from the An range when that is calibrated to a value independently determined from the evolved components. Examples from a recent treatment of residual porosity (cited above) will be given for the solidification of selected rock compositions from the Kiglapait and Skaergaard intrusions. The same principles apply to the solidification of melt inclusions, with the difference that the latter tend to sample an evolved sheath by capture, rather than a parent magma trapped by closure of a cumulate. Melt inclusions are evolved from birth, and then are likely to evolve further with continued growth and re-equilibration of the container. The cumulate, by contrast, given any small degree of adcumulus growth, has had time to exchange the evolved rejected solute owing to its slow solidification, so its trapped liquid is the contemporaneous magma at the cumulate interface. Experimental results on melt inclusions in mafic magma demonstrate their intrinsic evolved nature. For example

  5. Microstructural Development during Directional Solidification of Peritectic Alloys

    Lograsso, Thomas A.


    A thorough understanding of the microstructures produced through solidification in peritectic systems has yet to be achieved, even though a large number of industrially and scientifically significant materials are in this class. One type of microstructure frequently observed during directional solidification consists of alternating layers of primary solid and peritectic solid oriented perpendicular to the growth direction. This layer formation is usually reported for alloy compositions within the two-phase region of the peritectic isotherm and for temperature gradient and growth rate conditions that result in a planar solid-liquid interface. Layered growth in peritectic alloys has not previously been characterized on a quantitative basis, nor has a mechanism for its formation been verified. The mechanisms that have been proposed for layer formation can be categorized as either extrinsic or intrinsic to the alloy system. The extrinsic mechanisms rely on externally induced perturbations to the system for layer formation, such as temperature oscillations, growth velocity variations, or vibrations. The intrinsic mechanisms approach layer formation as an alternative type of two phase growth that is inherent for certain peritectic systems and solidification conditions. Convective mixing of the liquid is an additional variable which can strongly influence the development and appearance of layers due to the requisite slow growth rate. The first quantitative description of layer formation is a model recently developed by Trivedi based on the intrinsic mechanism of cyclic accumulation and depiction of solute in the liquid ahead of the interface, linked to repeated nucleation events in the absence of convection. The objective of this research is to characterize the layered microstructures developed during ground-based experiments in which external influences have been minimized as much as possible and to compare these results to the current the model. Also, the differences

  6. The monuments of the UNESCO List under threat in the 21rst century: the Project "MONUNESCO-PARIS" (2012-2013)

    Menendez, B.; Brimblecombe, P.; Deque, M.; Grossi, C. M.; Ionescu, A.; Lefevre, R. A.


    The banks of the River Seine in Paris are inscribed on the UNESCO List of the World Cultural Heritage since 1991 because they are studded with a succession of masterpieces such as Notre- Dame Cathedral, Sainte Chapelle, Louvre, Place de la Concorde, Tour Eiffel, and with prestigious museums: Louvre, Orsay, Quai Branly, Petit Palais…Unfortunately, these banks are crossed by the Pompidou urban motorway, an important and continuous source of atmospheric pollution. The aim of the Project is to evaluate the evolution of the weathering of limestone, glass and stained glass in the centre of Paris in the 21rst century by crossing Climate and Pollution Models with Dose-Response Functions (DRF) for limestone, glass and stained glass and with Climatology of Salt Transitions for limestone. A Lutetian limestone (« Courville Stone ») has been used for the construction and the restoration of the most important monuments (Notre-Dame, Louvre…) and haussmannian buildings in Paris. It has a fine grain, a medium porosity (19%) and contains 90% of CaO. The modern glass of windows and large contemporaneous façades has a Si-Ca-Na composition, it is chemically inert, has a low thermal inertia, a flat surface, no open porosity and no surface roughness, therefore it is very durable. The glass of stained glass windows has a Si-Ca-K composition and it is low durable. Using different climate and pollution scenarios of the 21rst century, the project will evaluate different schemes of material degradations: (i) - Recession of limestone surface; (ii) - Soiling of limestone surface; (iii) - Soiling of modern glass; (iv) - Leaching of ancient stained glass windows; (v) - Deterioration of limestone by salts. The British Hadley Models, the French Météo- France Arpège-Aladin Models and the ENSEMBLES Approach will be crossed with DRF and Climatology of Salts Transitions. An in-the-field inventory (stock at risk) of the surface occupied on the façades by each kind of material (stone

  7. Solidification of spent ion exchange resins into the SIAL matrix at the Dukovany NPP, Czech Republic

    Tatransky, Peter; Prazska, Milena; Harvan, David [AMEC Nuclear Slovakia, Trnava, Slovak Republic, 917 01 (Slovakia)


    Based on the decision of the State Office for Nuclear Safety, the Dukovany NPP has been obliged to secure the efficient capacities for the disposal of spent ion exchange resins. Therefore, in September 2010, based on the contract with supplier company AMEC Nuclear Slovakia s.r.o. has begun with pumping and treatment of ion exchange resins from the storage tank 0TW30B02, situated in the auxiliary building. The SIAL{sup R} technology, developed in AMEC Nuclear Slovakia, has been used for the solidification purposes. This technology allows an on-site treatment of various special radioactive waste streams (resins, sludge, sludge/resins and borates) at the room temperature. The SIAL{sup R} matrix and technology were licensed by the Czech State Office for Nuclear Safety in 2007. On-site treatment and solidification of spent ion exchange resins at Dukovany NPP involves process of resin removal from tank using remotely operated manipulator, resin transportation, resin separation from free water, resin filling into 200 dm{sup 3} drums and solidification into SIAL{sup R} matrix in 200 dm{sup 3} drums using the FIZA S 200 facility. The final product is observed for compressive strength, leachability, radionuclide composition, dose rate, solids and total weight. After meeting the requirements for final disposal and consolidation, the drums are being transported for the final disposal to the Repository at Dukovany site. During the 3 month's trial operation in 2010, and the normal operation in 2011 and 2012, 189 tons of dewatered resins have been treated into 1960 drums, with total activity higher than 920 GBq. At the end of trial run (2010), 22 tons of dewatered resins were treated into 235 drums. During standard operation approximately 91 tons in 960 drums (2011) and 76 tons in 765 drums (2012) were treated. The weights of resins in the drum ware in the range from 89 - 106 kg and compressive strength limit (10 MPa) has already been achieved 24 hours after fixation. The

  8. Solidification characteristics of Fe-Ni peritectic alloy thin strips under a near-rapid solidification condition

    Chang-jiang Song


    Full Text Available This paper is an experimental investigation of the structure evolution and the solute distribution of 2 mm thick strips of Fe-(2.6, 4.2, 4.7, 7.9wt.%Ni peritectic alloy under a near-rapid solidification condition, which were in the regions of δ-ferrite single-phase, hypo-peritectic, hyper-peritectic and γ-austenite single-phase, respectively. The highest area ratio of equiaxed grain zone in the hyper-peritectic of Fe-4.7wt.%Ni alloy strip was observed, while other strips were mainly columnar grains. The lowest micro-segregation was obtained in the Fe-7.9wt.%Ni alloy strip, while micro-segregation in the Fe-4.7wt.%Ni alloy was the highest. As opposed to the micro-segregation, the macro-segregation of all the Fe-Ni strips was suppressed due to the rapid solidification rate. Finally, the structure formation mechanism of Fe-Ni alloy strips was analyzed.

  9. Modeling of columnar and equiaxed solidification of binary mixtures; Modelisation de la solidification colonnaire et equiaxe de melanges binaires

    Roux, P


    This work deals with the modelling of dendritic solidification in binary mixtures. Large scale phenomena are represented by volume averaging of the local conservation equations. This method allows to rigorously derive the partial differential equations of averaged fields and the closure problems associated to the deviations. Such problems can be resolved numerically on periodic cells, representative of dendritic structures, in order to give a precise evaluation of macroscopic transfer coefficients (Drag coefficients, exchange coefficients, diffusion-dispersion tensors...). The method had already been applied for a model of columnar dendritic mushy zone and it is extended to the case of equiaxed dendritic solidification, where solid grains can move. The two-phase flow is modelled with an Eulerian-Eulerian approach and the novelty is to account for the dispersion of solid velocity through the kinetic agitation of the particles. A coupling of the two models is proposed thanks to an original adaptation of the columnar model, allowing for undercooling calculation: a solid-liquid interfacial area density is introduced and calculated. At last, direct numerical simulations of crystal growth are proposed with a diffuse interface method for a representation of local phenomena. (author)

  10. Technology.

    Online-Offline, 1998


    Focuses on technology, on advances in such areas as aeronautics, electronics, physics, the space sciences, as well as computers and the attendant progress in medicine, robotics, and artificial intelligence. Describes educational resources for elementary and middle school students, including Web sites, CD-ROMs and software, videotapes, books,…

  11. Effect of Melt Superheating Treatment on Directional Solidification Interface Morphology of Multi-component Alloy

    Changshuai Wang; Jun Zhang; Lin Liu; Hengzhi Fu


    The influence of melt superheating treatment on the solid/liquid (S/L) interface morphology of directionally solidified Ni-based superalloy DZ125 is investigated to elucidate the relationship between melt characteristic and S/L interface stability. The results indicate that the interface morphology is not only related to the withdrawal velocity (R) but also to the melt superheating temperature (Ts) when the thermal gradient of solidification interface remains constant for different Ts with appropriate superheating treatment regulation. The interface morphology changes from cell to plane at R of 1.1 μm/s when Ts increases from 1500°C to 1650°C, and maintains plane with further elevated Ts of 1750°C. However, the interface morphology changes from coarse dendrite to cell and then to cellular dendrite at R of 2.25 μm/s when Ts increases from 1500°C to 1650°C and then to 1750°C. It is proved that the solidification onset temperature and the solidification interval undergo the nonlinear variation when Ts increases from 1500°C to 1680°C, and the turning point is 1650°C at which the solidification onset temperature and the solidification interval are all minimum. This indicates that the melt superheating treatment enhances the solidification interface stability and has important effect on the solidification characteristics.

  12. ThermoCalc Application for the Assessment of Binary Alloys Non-Equilibrium Solidification

    Zyska A.


    Full Text Available The paper presents the possibility of application of the developed computer script which allows the assessment of non-equilibrium solidification of binary alloys in the ThermoCalc program. The script makes use of databases and calculation procedures of the POLY-3 module. A solidification model including diffusion in the solid state, developed by Wołczyński, is used to describe the non-equilibrium solidification. The model takes into account the influence of the degree of solute segregation on the solidification process by applying the so-called back-diffusion parameter. The core of the script is the iteration procedure with implemented model equation. The possibility of application of the presented calculation method is illustrated on the example of the Cr-30% Ni alloy. Computer simulations carried out with use of the developed script allow to determine the influence of the back-diffusion parameter on the course of solidification curves, solidus temperature, phase composition of the alloy and the fraction of each phase after the solidification completion, the profile of solute concentration in liquid during solidification process, the average solute concentration in solid phase at the eutectic temperature and many other quantities which are usually calculated in the ThermoCalc program.

  13. Directional solidification of flake and nodular cast iron during KC-135 low-g maneuvers

    Curreri, P. A.; Stefanescu, D. M.; Hendrix, J. C.


    Alloys solidified in a low-gravity environment can, due to the elimination of sedimentation and convection, form unique and often desirable microstructures. One method of studying the effects of low-gravity (low-g) on alloy solidification was the use of the NASA KC-135 aircraft flying repetitive low-g maneuvers. Each maneuver gives from 20 to 30 seconds of low-g which is between about 0.1 and 0.001 gravity. A directional solidification furnace was used to study the behavior of off eutectic composition case irons in a low-g environment. The solidification interface of hypereutectic flake and spheroidal graphite case irons was slowly advanced through a rod sample, 5 mm in diameter. Controlled solidification was continued through a number of aircraft parabolas. The known solidification rate of the sample was then correlated with accelerometer data to determine the gravity level during solidification for any location of the sample. The thermal gradient and solidification rate were controlled independently. Samples run on the KC-135 aircraft exhibited bands of coarser graphite or of larger nodules usually corresponding to the regions solidified under low-g. Samples containing high phosphorous (used in order to determine the eutectic cell) exhibited larger eutectic cells in the low-g zone, followed by a band of coarser graphite.

  14. Immobilisation/solidification of hazardous toxic waste in cement matrices

    Macías, A.


    Full Text Available Immobilization and solidification of polluting waste, introduced into the industrial sector more than 20 years ago, and throughout last 10 years is being the object of a growing interest for engineers and environment scientists, has become a remarkable standardized process for treatment and management of toxic and hazardous liquid wastes, with special to those containing toxic metals. Experimental monitorization of the behaviour of immobilized waste by solidification and stabilisation in life time safe deposits is not possible, reason why it is essential to develop models predicting adequately the behaviour of structures that have to undergo a range of conditions simulating the environment where they are to be exposed. Such models can be developed only if the basic physical and chemical properties of the system matrix/solidifying-waste are known. In this work immobilization/solidification systems are analyzed stressing out the formulation systems based on Portland cement. Finally, some examples of the results obtained from the study of interaction of specific species of wastes and fixation systems are presented.

    La inmovilización y solidificación de residuos contaminantes, implantada en el sector comercial desde hace más de 20 años y que desde hace diez es objeto de creciente interés por parte de ingenieros y científicos medioambientales, se ha convertido en un proceso estandarizado único para el tratamiento y gestión de residuos tóxicos y peligrosos líquidos y, en especial, de los que contienen metales pesados. La monitorización experimental del comportamiento de un residuo inmovilizado por solidificación y estabilización en el tiempo de vida de un depósito de seguridad no es posible, por lo que es imprescindible desarrollar modelos que predigan satisfactoriamente el comportamiento del sistema bajo un rango representativo de condiciones del entorno de exposición. Tales modelos sólo pueden ser desarrollados si se

  15. Immiscible phase incorporation during directional solidification of hypermonotectics

    Andrews, J. Barry; Merrick, Roger A.


    Solidification processes in immiscible samples were investigated by directly observing the events taking place at the solid-liquid interface during directional solidification. Visualization of these events was made possible through the use of a transparent metal analog system and a temperature gradient stage assembly fitted to an optical microscope. The immiscible transparent analog system utilized was the succinonitrile-glycerol system. This system has been shown to exhibit the same morphological transitions as observed in metallic alloys of monotectic composition. Both monotectic and hypermonotectic composition samples were directionally solidified in order to gain an improved understanding of the manner in which the excess hypermonotectic liquid is incorporated into the solidifying structure. The processing conditions utilized prevented sedimentation of the excess hypermonotectic liquid by directionally solidifying the samples in very thin (13 microns), horizontally oriented cells. High thermal gradient to growth rate ratios (G/R) were used in an effort to prevent constitutional supercooling and the subsequent formation of L(sub 2) droplets in advance of the solidification front during the growth of fibrous composite structures. Results demonstrated that hypermonotectic composites could be produced in samples up to two weight percent off of the monotectic composition by using a G/R ratio greater than or equal to 4.6 x 10(exp 4) C(s)/mm(sup 2) to avoid constitutional supercooling. For hypermonotectic samples processed with G/R ratios below 4.6 x 10(exp 4) C(s)/mm(sup 2), constitutional supercooling occurred and resulted in slight interfacial instability. For these samples, two methods of incorporation of the hypermonotectic liquid were observed and are reported. The correlation between the phase spacing, lambda, and the growth rate, R, was examined and was found to obey a relationship generally associated with a diffusion controlled coupled growth process. For

  16. Solidification and properties of photovoltaic silicon; Solidification et proprietes du silicium photovoltaique



    Strenuous efforts are being made to develop an economical process for purifying liquid metallurgical-grade silicon, in response to the growing shortages in high-purity silicon for use in manufacturing photovoltaic cells. A research project is studying this issue at C.E. Saclay, Gif-sur-Yvette, France, co-funded by ADEME (the French Environment and Energy Management Agency) and CEA-INSTN (French Atomic Energy Commission National Institute for Nuclear Science and Technology). (authors)

  17. Numerical analysis on solidification process and heat transfer of FGH95 superalloy droplets during PREP

    Huanming Chen; Benfu Hu; Yiwen Zhang; Quanmao Yu; Huiying Li


    In order to understand the relation between microstructure of superalloy powders and its solidification progress, the processing parameters are optimized during plasma rotating electrode processing (PREP). It was predicted from the results that the droplet velocities, droplet temperature, and fractional solidification with flight time about FGH95 superalloy droplet have been carried out based on Newtonian heat transfer formulation coupled with the classical heterogeneous nucleation and the specific solidification process. It has been found that the droplet dynamic and thermal behavior is strongly affected by the distribution of droplet diameters,the proportion of cooling atmosphere, but is relatively unaffected by the droplet superheat.

  18. Numerical calculation on temperature field of FGH95 alloy droplet during rapid solidification

    Huanming Chen; Benfu Hu


    The temperature field of FGH95 alloy droplet atomized by plasma rotating electrode processing (PREP) during solidifica-tion has been calculated through numerical analysis based on equivalent sensible heat capacity method. And thus the relational cul-ves among temperature gradient of solid-liquid interface, moving velocity of solid-liquid interface and solid fraction during solidifi-cation have been presented. The results indicate that the relation between average temperature gradient of solid-liquid interface anddroplet size, and the relation between average moving velocity of solid-liquid interface and droplet size can be expressed during solidification.

  19. Elimination of Hot Tears in Steel Castings by Means of Solidification Pattern Optimization

    Kotas, Petr; Tutum, Cem Celal; Thorborg, Jesper


    the solidification pattern, i.e., establishing directional and progressive solidification with the help of the Niyama criterion, macrosegregation and hot tearing issues can be both minimized or eliminated entirely. An original casting layout was simulated using a transient three-dimensional (3-D) thermal fluid model...... incorporated in a commercial simulation software package to determine potential flaws and inadequacies. Based on the initial casting process assessment, multiobjective optimization of the solidification pattern of the considered steel part followed. That is, the multiobjective optimization problem of choosing...

  20. Anisotropic growth of multigrain in equiaxial solidification simulated with the phase field method

    Li Mei-E; Xiao Zhi-Ying; Yang Gen-Cang; Zhou Yao-He


    The phase field method has been mainly used to simulate the growth of a single crystal in the past. But polycrystalline materials predominate in engineering. In this work, a phase field model for multigrain solidification is developed, which takes into account the random crystallographic orientations of crystallites and preserves the rotational invariance of the free energy. The morphological evolution of equiaxial multigrain solidification is predicted and the effect of composition on transformation kinetics is studied. The numerical results indicate that due to the soft impingement of grains the Avrami exponent varies with the initial melt composition and the solidification fraction.

  1. Investigation of the physical properties of iron nanoparticles in the course of the melting and solidification

    Fedorov, A. V.; Shul'gin, A. V.; Lavruk, S. A.


    The processes of iron-nanoparticles melting and iron-nanodroes solidification have been studied under different thermal actions. The determined values of the phase-transition temperatures for particles with radii of 1.5-4 nm agree with the data calculated by other authors. In the course of calculating the solidification of iron nanoparticles, the dependence of the solidification temperature on the rate of heat removal has been found and the hysteresis of the phase transition has been demonstrated. Based on the determined caloric curves, the heat capacity of the particles has been found and their approximation in the form of dependences on temperature and particle size has been suggested.

  2. Long-time dynamics of the directional solidification of rodlike eutectics.

    Perrut, Mikaël; Akamatsu, Silvère; Bottin-Rousseau, Sabine; Faivre, Gabriel


    We report long-duration real-time observations of the dynamics of hexagonal (rodlike) directional-solidification patterns in bulk samples of a transparent eutectic alloy. A slight forward curvature of the isotherms induces a slow dilatation of the growth pattern at constant solidification rate and triggers the rod-splitting instability. At long times, the rod-splitting frequency exactly balances the dilatation driven by the curved isotherms. The growth pattern is then disordered and nonstationary but has a sharply selected mean spacing. Well-ordered growth patterns can be grown using time-dependent solidification rates.

  3. Three Dimensional Numerical Simulation for the Driving Force of Weld Solidification Cracking

    Zhibo DONG; Yanhong WEI; Renpei LIU; Zujue DONG


    The double ellipsoidal model of heat source is used to analyze the thermal distributions with a three dimensional finite element method (FEM). In the mechanical model, solidification effects are treated by a dynamic element rebirth scheme. The driving force is obtained in the cracking susceptible temperature range. Moreover, this paper presents the effect of solidification shrinkage, external restraint, weld start locations and material properties on the driving force. The comparison between the simulated driving force and the experimental measurements of the material resistance predicts the susceptibility of weld metal solidification cracking.

  4. Detection of inner core solidification from observations of antipodal PKIIKP

    Cormier, Vernon F.


    PKIIKP waves, reflected from the underside of the inner core boundary, are very sensitive to the S velocity in the uppermost 80 km of the inner core at antipodal distances, undergoing a phase change and a factor of 4 amplification as the distance approaches 180°. Modeled PKIIKP waveforms are consistent with a near-zero shear modulus in the uppermost inner core in a 20-40 km thick patch beneath the eastern equatorial hemisphere. This bright spot of PKIIKP reflection correlates with a thin zone of low P velocity inferred from the complexity of PKIKP waveforms sampling this patch. Estimates of grain sizes from seismic attenuation, the absence of backscattered PKiKP coda in this region, and a prediction for enhanced heat flow through this patch suggest that it is a region of solidification rather than melting.

  5. Solidification of Suspended Sediments with Two Characteristic Grain Sizes

    Zarski, G.; Borja, R. I.


    We use mixture theory to formulate the problem of solidification of sediments with two characteristic grain sizes in a suspension. The formulation involves a mixture of larger grains in a thick fluid, where the thick fluid is a mixture of smaller particles in a host fluid. This mixture within a mixture description resembles a double porosity representation in unsaturated soil mechanics. Two independent variables of interest include the volume fraction of the larger grains relative to the total volume of the mixture, and the volume fraction of the smaller grains relative to the volume of the thick fluid. The two volume fractions are coupled by a constitutive law based on the Richardson-Zaki equation. The governing partial differential equations describing the settling velocities of the two solid groups are solved simultaneously in space and time using the finite element method.

  6. Assessment of mathematical models for the flow in directional solidification

    Lu, Jay W.; Chen, Falin


    In a binary solution unidirectionally solidified from below, the bulk melt and the eutectic solid is separated by a dendritic mushy zone. The mathematical formulation governing the fluid motion shall thus consist of the equations in the bulk melt and the mushy zone and the associated boundary conditions. In the bulk melt, assuming that the melt is a Newtonian fluid, the governing equations are the continuity equation, the Navier-Stokes equations, the heat conservation equation, and the solute conservation equation. In the mushy layer, however, the formulation of the momentum equation and the associated boundary conditions are diversified in previous investigations. In this paper, we discuss three mathematical models, which had been previously applied to study the flow induced by the solidification of binary solutions cooling from below. The assessment is given on the bases of the stability characteristics of the convective flow and the comparison between the numerical and experimental results.

  7. Melting and solidification of Bi nanoparticles in a germanate glass

    Haro-Poniatowski, E.; Jiménez de Castro, M.; Fernández Navarro, J. M.; Morhange, J. F.; Ricolleau, C.


    A very large melting-solidification hysteresis of Bi nanoparticles embedded in a bulk alkali germanate glass is reported. Heating and cooling cycles are reproducible and show reversible transitions. High resolution transmission electron microscopy reveals that the glass contains nanocrystals of elementary Bi which are a few tenths of a nanometre in size. Upon heating above the Bi melting temperature the glass transmission increases up to 10% with respect to the initial value, which is most likely related to Bi melting. Upon cooling this high transmission state remains up to temperatures as low as 436 K. This behaviour is confirmed by Raman spectroscopy measurements. This nanostructured glass with a high refractive index can be used in nonlinear optical applications as well as an optical thermo-sensor.

  8. Polymer solidification of mixed wastes at the Rocky Flats Plant

    Faucette, A.M.; Logsdon, B.W.; Lucerna, J.J.; Yudnich, R.J.


    The Rocky Flats Plant is pursuing polymer solidification as a viable treatment option for several mixed waste streams that are subject to land disposal restrictions within the Resource Conservation and Recovery Act provisions. Tests completed to date using both surrogate and actual wastes indicate that polyethylene microencapsulation is a viable treatment option for several mixed wastes at the Rocky Flats Plant, including nitrate salts, sludges, and secondary wastes such as ash. Treatability studies conducted on actual salt waste demonstrated that the process is capable of producing waste forms that comply with all applicable regulatory criteria, including the Toxicity Characteristic Leaching Procedure. Tests have also been conducted to evaluate the feasibility of macroencapsulating certain debris wastes in polymers. Several methods and plastics have been tested for macroencapsulation, including post-consumer recycle and regrind polyethylene.

  9. Modeling of Mold Filling and Solidification in Lost Foam Casting

    Fengjun LI; Houfa SHEN; Baicheng LIU


    Based on the characteristics of the lost foam casting (LFC) and the artificial neural network technique, a mathematicalmodel for the simulation of the melt-pattern interface movement during the mold filling of LFC has been proposed andexperimentally verified. The simulation results are consistent with the experiments in both the shapes of melt frontand filling sequences. According to the calculated interface locations, the fluid flow and the temperature distributionsduring the mold filling and solidification processes were calculated, and the shrinkage defect of a lost foam ductileiron casting was predicted by considering the mold wall movement in LFC. The simulation method was applied tooptimize the casting design of lost foam ductile iron castings. It is shown that the model can be used for the defectsprediction and for casting design optimization in the practical LFC production.

  10. Existence of needle crystals in local models of solidification

    Langer, J. S.


    The way in which surface tension acts as a singular perturbation to destroy the continuous family of needle-crystal solutions of the steady-state growth equations is analyzed in detail for two local models of solidification. All calculations are performed in the limit of small surface tension or, equivalently, small velocity. The basic mathematical ideas are introduced in connection with a quasilinear, isotropic version of the geometrical model of Brower et al., in which case the continuous family of solutions dissappears completely. The formalism is then applied to a simplified boundary-layer model with an anisotropic kinetic attachment coefficient. In the latter case, the solvability condition for the existence of needle crystals can be satisfied whenever the coefficient of anisotropy is arbitrarily small but nonzero.

  11. Modelling of binary alloy solidification in the MEPHISTO experiment

    Leonardi, Eddie; de Vahl Davis, Graham; Timchenko, Victoria; Chen, Peter; Abbaschian, Reza


    A modified enthalpy method was used to numerically model experiments on solidification of a bismuth-tin alloy which were performed during the 1997 flight of the MEPHISTO-4 experiment on the US Space Shuttle Columbia. This modified enthalpy method was incorporated into an in-house code SOLCON and a commercial CFD code CFX; Soret effect was taken into account by including an additional thermo-diffusion term into the solute transport equation and the effects of thermal and solutal convection in the microgravity environment and of concentration-dependent melting temperature on the phase change processes were also included. In this paper an overview of the results obtained as part of MEPHISTO project is presented. The numerical solutions are compared with actual microprobe results obtained from the MEPHISTO experiment. To cite this article: E. Leonardi et al., C. R. Mecanique 332 (2004).

  12. Solidification of Spent Ion Exchange Resin Using ASC Cement

    周耀中; 云桂春; 叶裕才


    Ion exchange resins (IERs) have been widely used in nuclear facilities. However, the spent radioactive IERs result in major quantities of low and intermediate level radioactive wastes. This article describes a laboratory experimental study on solidification processing of IERs using a new type of cement named ASC cement. The strength of the cementation matrix is in the range of 18-20 MPa (28 d); the loading of the spent IER in the cement-resin matrix is over 45% and leaching rates of 137Cs, 90Sr and 60Co are 7.92×10-5, 5.7×10-6, and 1.19×10-8 cm/d. The results show that ASC cement can be a preferable cementation material for immobilization of radioactive spent IER.

  13. Self Assembled Structures by Directional Solidification of Eutectics

    Dynys, Frederick W.; Sayir, Ali


    Interest in ordered porous structures has grown because of there unique properties such as photonic bandgaps, high backing packing density and high surface to volume ratio. Inspired by nature, biometric strategies using self assembled organic molecules dominate the development of hierarchical inorganic structures. Directional solidification of eutectics (DSE) also exhibit self assembly characteristics to form hierarchical metallic and inorganic structures. Crystallization of diphasic materials by DSE can produce two dimensional ordered structures consisting of rods or lamella. By selective removal of phases, DSE is capable to fabricate ordered pore arrays or ordered pin arrays. Criteria and limitations to fabricate hierarchical structures will be presented. Porous structures in silicon base alloys and ceramic systems will be reported.

  14. Nonlinear theory of autooscillations of quasiplanar interface during directional solidification

    Lubashevsky, I A; Keijan, M G


    Within the framework of the frozen temperature approximation we develop a strongly-nonlinear theory of one-dimensional pattern formation during directional solidification of binary mixture under nonequilibrium segregation. In the case of small partition coefficient the full problem is reduced to the system of two ordinary differential equations describing the interface motion in terms of its velocity and position coordinate. The type of the oscillatory instability bifurcation is studied in detail in different limits. For the subcrytical bifurcaton relaxation interface oscillations are analyzed analytically and numerically. We show that these oscillation exibit a number of anomalous properies. In particular, such oscillations can be weakly- or strongly-dissipative depending on the physical parameters and the amplitude of the strongly-dissipative oscillations is determined not only by the form of the corresponding nullcline but also by the behavior of the system for small values of the interface velocity. Chara...

  15. Prediction of the solidification structure of casting and heterogeneous nucleation

    K. Ohsasa; H. Shirosawa; T. Narita


    The frequency of heterogeneous nucleation during the solidification of Al-Si binary alloy was estimated by comparing ex-perimentally obtained macrostructures of castings with numerically simulated ones. A molten alloy was unidirectionally solidifiedfrom a water-cooled copper chill in an adiabatic mold. The location of colunmar to equiaxed transition (CET) in the solidified alloyingot was measured. A numerical simulation for grain structure formation based on the Monte Carlo method was carried out, and thefrequency of heterogeneous nucleation in the alloy was evaluated by producing similar structure with the experimental one. The fre-quency of heterogeneous nucleation was expressed as a probabilistic function with an exponential form of undercooling that deter-mines the probability of nucleation event in the simulation. The value of the exponent is regarded as the nucleation parameter. Thenucleation parameter of Al-Si binary alloy varied with initial Sicontent.

  16. Solidification of hypermonotectic Al-In alloys under microgravity conditions

    Potard, C.


    Four samples of the Al-In system having monotectic and hypermonotectic compositions that were solidified under microgravity during the NASA-SPAR IX flight of January 20, 1981, are considered. The experimental thermal and physicochemical conditions that were actually achieved are analyzed. Radiographic and metallographic observations of the samples reveal a nonregular dispersed primary phase inside the monotectic matrix. These observations are discussed in relation to capillarity and solidification aspects. A key finding is the preservation of a certain degree of dispersion of the indium primary phase. This result differs fundamentally from the results obtained under microgravity conditions on the same system and compositions (Gelles and Markworth, 1980; Alborn and Loehberg, 1979). The results are seen as clearly establishing that the space environment can be used to obtain dispersed structures from hypermonotectic alloys.

  17. Influence of gravity on the solidification of a drop

    Sanz, A.; Meseguer, J.; Mayo, L.


    In this paper the influence of gravity on the solidification of a drop formed at the end of a rod is analyzed. Although similar studies (but ignoring gravity effects) already exist, a theoretical analysis including gravity effects allows one to improve the experimental procedure to measure on Earth relevant properties of crystals (mainly the receding contact angle phi/sub i/) which are of importance in shaped crystal growth processes. One of the main results here obtained are the shapes of the solidified drops, which are strongly dependent on the value of phi/sub i/. Therefore, fitting theoretical shapes to experimental ones is a way to perform accurate measurements of phi/sub i/.

  18. Melting and solidification of Bi nanoparticles in a germanate glass

    Haro-Poniatowski, E [Departamento de Fisica, Universidad Autonoma Metropolitana Iztapalapa, Avenida San Rafael Atlixco No. 186 Colonia Vicentina, CP 09340 Mexico DF (Mexico); Castro, M Jimenez de [Instituto de Optica, CSIC, Serrano 121, 28006 Madrid (Spain); Navarro, J M Fernandez [Instituto de Optica, CSIC, Serrano 121, 28006 Madrid (Spain); Morhange, J F [Institut des Nanosciences de Paris, UMR-CNRS 7588, Universite Paris VI et Paris VII, 4 Place Jussieu, Paris (France); Ricolleau, C [Laboratoire Materiaux et Phenomenes Quantiques and Laboratoire de Physique du Solide, UMR 7162, CNRS/Universite Paris 7-Denis Diderot, ESPCI, 10 rue Vauquelin, 75005 Paris Cedex (France)


    A very large melting-solidification hysteresis of Bi nanoparticles embedded in a bulk alkali germanate glass is reported. Heating and cooling cycles are reproducible and show reversible transitions. High resolution transmission electron microscopy reveals that the glass contains nanocrystals of elementary Bi which are a few tenths of a nanometre in size. Upon heating above the Bi melting temperature the glass transmission increases up to 10% with respect to the initial value, which is most likely related to Bi melting. Upon cooling this high transmission state remains up to temperatures as low as 436 K. This behaviour is confirmed by Raman spectroscopy measurements. This nanostructured glass with a high refractive index can be used in nonlinear optical applications as well as an optical thermo-sensor.

  19. Rapid solidification of Cu-Fe-Ni alloys

    Baricco, M.; Bosco, E.; Acconciaioco, G.; Rizzi, P.; Coisson, M


    Cu{sub 80-x}Ni{sub x}Fe{sub 20} (x=0, 5 and 20) alloys have been rapidly solidified by planar flow casting. X-ray diffraction (XRD) analysis of as-quenched ribbons shows bcc-Fe precipitates embedded in an fcc phase (x=0), two co-existing fcc solid solutions (x=5) and a complete solid solution of the parent elements (x=20). Thermal treatments in the temperature range between 400 and 600 deg. C give precipitation and spinodal decomposition reactions. These phase transformations have been evidenced from a variation of lattice constants, from a broadening of diffraction peaks and from TEM observations. The role of Ni content on competition between precipitation and decomposition reactions during rapid solidification and annealing is discussed in terms of thermodynamic arguments. Recent CALPHAD assessment of thermodynamic properties for Cu-Fe-Ni system has been used for an estimation of composition and volume fraction of equilibrium phases.

  20. Modelling of Mould Filling and Solidification of Castings

    Xu Zhian


    An experimental casting for validation has been designed. The casting is composed of two 50×600×2.5 (width×length×thick) thin-wall pieces. One downsprue is located in the middle. A pouring cup with a stopper is used. This design allows to using two different types of moulds simultaneously. An Al-10%Si alloy has been poured at different temperatures. Two effects have been studied: one is the pouring temperature and the other is the moulding method (namely by machine or manually). The filling length is proportional to the pouring temperature. The influence of different moulding methods on mould filling is more complicated. The filling length in the manual-made mould is 1.5 times as long as the one in the machine-made mould due to the different thermal conductivities. Vents have little influence. A finite volume based computer code which can simulate fluid flow during mould filling coupled with heat transfer as well as solidification has been developed in WTCM Foundry Center.. The code can predict cold shut during mould filling and shrinkage defects during solidification. The simulated results are in good agreement with the experiments.In the second part of the paper, an example is given which illustrates how to use computer simulation to aid designing the casting system. The final computational result is compared with the industrial casting. The process of designing castings by using simulation is completely different from the traditional way. The computer aided casting design offers the possibility to obtain a sound casting from the first time.

  1. Directional Solidification of Mercury Cadmium Telluride in Microgravity

    Lechoczhy, Sandor L.; Gillies, Donald C.; Szofran, Frank R.; Watring, Dale A.


    Mercury cadmium telluride (MCT) has been directionally solidified for ten days in the Advanced Automated Directional Solidification Furnace (AADSF) on the second United States Microgravity Payload Mission (USMP-2). A second growth experiment is planned for the USMP-4 mission in November 1997. Results from USMP-2 demonstrated significant changes between microgravity and ground-based experiments, particularly in the compositional homogeneity. Changes were also observed during the microgravity mission which were dependent on the attitude of the space shuttle and the relative magnitudes of axial and transverse residual accelerations with respect to the growth axis of the crystal. Issues of shuttle operation, especially those concerned with safety and navigation, and the science needs of other payloads dictated the need for changes in attitude. One consequence for solidification of MCT in the USMP4 mission is the desire for a shorter growth time to complete the experiment without subjecting the sample to shuttle maneuvers. By using a seeded technique and a pre-processed boule of MCT with an established diffusion layer quenched into the solid, equilibrium steady state growth can be established within 24 hours, rather than the three days needed in USMP-2. The growth of MCT in AADSF during the USMP-4 mission has been planned to take less than 72 hours with 48 hours of actual growth time. A review of the USMP-2 results will be presented, and the rationale for the USMP-4 explained. Pre-mission ground based tests for the USN4P-4 mission will be presented, as will any available preliminary flight results from the mission.

  2. Technology

    Xu Jing


    Full Text Available The traditional answer card reading method using OMR (Optical Mark Reader, most commonly, OMR special card special use, less versatile, high cost, aiming at the existing problems proposed a method based on pattern recognition of the answer card identification method. Using the method based on Line Segment Detector to detect the tilt of the image, the existence of tilt image rotation correction, and eventually achieve positioning and detection of answers to the answer sheet .Pattern recognition technology for automatic reading, high accuracy, detect faster

  3. Effect of Electrode Types on the Solidification Cracking Susceptibility of Austenitic Stainless Steel Weld Metal

    J. U. Anaele


    Full Text Available The effect of electrode types on the solidification cracking susceptibility of austenitic stainless steel weld metal was studied. Manual metal arc welding method was used to produce the joints with the tungsten inert gas welding serving as the control. Metallographic and chemical analyses of the fusion zones of the joints were conducted. Results indicate that weldments produced from E 308-16 (rutile coated, E 308-16(lime-titania coated electrodes, and TIG welded joints fall within the range of 1.5≤Creq./Nieq.≤1.9 and solidified with a duplex mode and were found to be resistant to solidification cracking. The E 308-16 weld metal had the greatest resistance to solidification cracking. Joints produced from E 310-16 had Creq./Nieq. ratio 1.9 and solidified with ferrite mode. It had a low resistance to solidification cracking.

  4. Effect of pulse magnetic field on solidification structure and properties of pure copper

    LIAO Xi-liang; GONG Yong-yong; LI Ren-xing; CHEN Wen-jie; ZHAI Qi-jie


    The application of pulse magnetic field to metal solidification is an advanced technique which can remarkably refine solidification structure. In this paper, the effect of pulse magnetic field on solidification structure,mechanical properties and conductivity of pure copper was experimentally investigated. The results showed that the solidification structure transformed from coarse columnar crystal to fine globular crystal with increasing pulse voltage.Increasing pulse voltage also improved the tensile strength. However, with the increase of pulse voltage, the elongation and electrical resistivity firstly decreased, then increased when the pulse voltage beyond a critical value. Moreover,in some conditions, pulse magnetic field can simultaneously improve the conductivity and mechanical property of pure copper.


    I. A. Pugachev


    Full Text Available A process of heat transfer in continuous casting mould is considered. The substantiated equations predict shell growth, temperature distributions, solidification rates and can be used for continuous casters control systems.

  6. Density and Mechanical Properties of Aluminum Lost Foam Casting by Pressurization during Solidification


    Porosity is thought to be severe in aluminum alloy castings produced by lost foam process due to the pyrolysis of the polystyrene foam pattern during pouring, which results in detrimental effect in mechanical property.The slow solidification rate promotes the formation of gassing pin holes, and relative weakness of the thermal gradients can cause micro-shrinkage if the outline of the part complicates feeding in the lost foam casting. One of the methods to eliminate the porosity is to apply high pressure to the molten metal like an isostatic forging during solidification. Fundamental experiments were carried out to evaluate the effect of the external pressure on the porosity and mechanical properties of A356.2 alloy bar in the lost foam casting. Solidification time and porosity decreased with increasing the applied pressure during solidification. Applying external pressure was effective in decreasing the porosity and increasing the elongation of the lost foam casting.

  7. Effect of Solidification Condition on Microstructure and Mechanical Properties of Single Crystal Superalloy


    CMSX-2 single crystals with different primary dendrite arm spacing were obtained on directional solidification apparatus with high temperature gradient (250 K/cm). The microstructure and elevated temperature stress rupture properties of these single crystals were examined and analyzed.

  8. In-situ observation of porosity formation during directional solidification of Al-Si casting alloys

    Zhao Lei


    Full Text Available In-situ observation of porosity formation during directional solidification of two Al-Si alloys (7%Si and 13%Si was made by using of micro-focus X-ray imaging. In both alloys, small spherical pores initially form in the melt far away from the eutectic solid-liquid (S/L interface and then grow and coagulate during solidification. Some pores can float and escape from the solidifying melt front at a relatively high velocity. At the end of solidification, the remaining pores maintain spherical morphology in the near eutectic alloy but become irregular in the hypoeutectic alloy. This is attributed to different solidification modes and aluminum dendrite interactions between the two alloys. The mechanism of the porosity formation is briefly discussed in this paper.

  9. Macrosegregation and Grain Formation Caused by Convection Associated with Directional Solidification Through Cross-Section Increase

    Ghods, Masoud; Lauer, Mark; Tewari, Surendra; Poirier, David; Grugel, Richard


    Cylindrical Al-7 wt% Silicon, Al-19 wt% Copper and Lead-6 wt% Antimony alloy samples were directionally solidified (DS) with liquid above, solid below, and gravity pointing down, in graphite crucibles having an abrupt cross-sectional increase. These alloys have similar solidification shrinkage but are expected to have different degrees of thermosolutal convection during solidification. Microstructures in the DS samples in the vicinity of the section change have been studied in order to examine the effect of convection associated with the combined influence of thermosolutal effects and solidification shrinkage. Extensive radial and axial macrosegregation associated with cross-section change is observed. It also appears that steepling and local primary alpha-phase remelting resulting from convection are responsible for stray grain formation at the reentrant corners. Preliminary results from a numerical model, which includes solidification shrinkage and thermosolutal convection in the mushy zone, indicate that these regions are prone to solutal remelting of dendrites.

  10. Microstructure Characteristics of Ni-Nb Near Eutectic Alloy during EBFZM Directional Solidification


    Microstructure Characteristic of Ni-Nb near eutectic alloy is systematically investigated during directional solidification with electron beam floating zone melting (EBFZM). The effect of the zone melting rate on the microstructure has also been studied.

  11. Stress/strain distributions for weld metal solidification crack in stainless steels


    This paper has simulated the driving force of solidification crack of stainless steels, that is, stress/strain field in the trail of molten pool. Firstly, the effect of the deformation in the molten pool was eliminated after the element rebirth method was adopted. Secondly, the influence of solidification shrinkage was taken into account by increasing thermal expansion coefficients of the steels at elevated temperatures. Finally, the stress/strain distributions of different conditions have been computed and analyzed. Furthermore, the driving force curves of the solidification crack of the steels have been obtained by converting strain-time curves into strain-temperature curves, which founds a basis for predicting welding solidification crack.

  12. Effect of vacuum on solidification process and microstructure of LFC magnesium alloy

    LIU Zi-li; LIU Xi-qin; XU Jiang; GUO Hua-ming; PAN Qing-lin; ZHOU Hai-tao


    Lost foam casting (LFC) is regarded as a cost-effective, environment-friendly vital option to the conventional casting process for production of near-net shape castings with high quality. Effect of vacuum on the solidification process and microstructure of LFC magnesium alloy were explored. The results indicate that vacuum plays a very important role in the heat transfer during mould filling and solidification periods, it increases the cooling rate of the filling melt, but greatly decreases the cooling rate of the casting during solidification period, and the solidification time of the casting is greater than that without vacuum. The microstructure of LFC magnesium alloy is rather coarse. Compared with that without vacuum, the microstructure of the LFC magnesium alloy under vacuum is more refined and has less precipitated β-phase, which is formed at the grain boundry and around the Al-Mn compound particle.

  13. In Situ Synchrotron X-ray Study of Ultrasound Cavitation and Its Effect on Solidification Microstructures

    Mi, Jiawei; Tan, Dongyue; Lee, Tung Lik


    Considerable progress has been made in studying the mechanism and effectiveness of using ultrasound waves to manipulate the solidification microstructures of metallic alloys. However, uncertainties remain in both the underlying physics of how microstructures evolve under ultrasonic waves, and the best technological approach to control the final microstructures and properties. We used the ultrafast synchrotron X-ray phase contrast imaging facility housed at the Advanced Photon Source, Argonne National Laboratory, US to study in situ the highly transient and dynamic interactions between the liquid metal and ultrasonic waves/bubbles. The dynamics of ultrasonic bubbles in liquid metal and their interactions with the solidifying phases in a transparent alloy were captured in situ. The experiments were complemented by the simulations of the acoustic pressure field, the pulsing of the bubbles, and the associated forces acting onto the solidifying dendrites. The study provides more quantitative understanding on how ultrasonic waves/bubbles influence the growth of dendritic grains and promote the grain multiplication effect for grain refinement.




    Large quantities of mercury are generated as a by-product during the processing of gold ore following mining operations. Newmont Mining Corporation (NMC), which operates some of the world's largest gold mines, sought a method to permanently ''retire'' its mercury by-products, thereby avoiding potential environmental liability. Sulfur Polymer Stabilization-Solidification (SPSS) is an innovative technology developed at Brookhaven National Laboratory (BNL) for treatment of mercury and mercury contaminated materials, such as soil, sludge and debris. BNL conducted a treatability study to determine the potential applicability of SPSS for treatment of Newmont mercury, and the treated product passed the U.S. Environmental Protection Agency (EPA) test for toxicity. The SPSS process has been shown to be effective on radioactive and nonradioactive mercury and mercury-contaminated materials with a pilot-scale batch system capable of producing 0.03 m{sup 3} (1 ft{sup 3}) per batch. Engineering scale-up issues are discussed and material property tests addressing these issues are described.

  15. Multiscale modelling and simulation of single crystal superalloy turbine blade casting during directional solidification process

    Xu Qingyan


    Full Text Available As the key parts of an aero-engine, single crystal (SX superalloy turbine blades have been the focus of much attention. However, casting defects often occur during the manufacturing process of the SX turbine blades. Modeling and simulation technology can help to optimize the manufacturing process of SX blades. Multiscale coupled models were proposed and used to simulate the physical phenomena occurring during the directional solidification (DS process. Coupled with heat transfer (macroscale and grain growth (meso-scale, 3D dendritic grain growth was calculated to show the competitive grain growth at micro-scale. SX grain selection behavior was studied by the simulation and experiments. The results show that the geometrical structure and technical parameters had strong influences on the grain selection effectiveness. Based on the coupled models, heat transfer, grain growth and microstructure evolution of a complex hollow SX blade were simulated. Both the simulated and experimental results show that the stray grain occurred at the platform of the SX blade when a constant withdrawal rate was used in manufacturing process. In order to avoid the formation of the stray crystal, the multi-scale coupled models and the withdrawal rate optimized technique were applied to the same SX turbine blade. The modeling results indicated that the optimized variable withdrawal rate can achieve SX blade castings with no stray grains, which was also proved by the experiments.

  16. Grout and glass performance in support of stabilization/solidification of ORNL tank sludges

    Spence, R.D.; Mattus, C.H.; Mattus, A.J.


    Wastewater at Oak Ridge National Laboratory (ORNL) is collected, evaporated, and stored in the Melton Valley Storage Tanks (MVST) and Bethel Valley Evaporator Storage Tanks (BVEST) pending treatment for disposal. In addition, some sludges and supernatants also requiring treatment remain in two inactive tank systems: the gunite and associated tanks (GAAT) and the old hydrofracture (OHF) tank. The waste consists of two phases: sludge and supernatant. The sludges contain a high amount of radioactivity, and some are classified as TRU sludges. Some Resource Conservation and Recovery Act (RCRA) metal concentrations are high enough to be defined as RCRA hazardous; therefore, these sludges are presumed to be mixed TRU waste. Grouting and vitrification are currently two likely stabilization/solidification alternatives for mixed wastes. Grouting has been used to stabilize/solidify hazardous and low-level radioactive waste for decades. Vitrification has been developed as a high-level radioactive alternative for decades and has been under development recently as an alternative disposal technology for mixed waste. The objective of this project is to define an envelope, or operating window, for grout and glass formulations for ORNL tank sludges. Formulations will be defined for the average composition of each of the major tank farms (BVEST/MVST, GAAT, and OHF) and for an overall average composition of all tank farms. This objective is to be accomplished using surrogates of the tank sludges with hot testing of actual tank sludges to check the efficacy of the surrogates.

  17. Effects of physical parameters on the cell-to-dendrite transition in directional solidification

    Wei, Lei; Lin, Xin; Wang, Meng; Huang, Wei-Dong


    A quantitative cellular automaton model is used to study the cell-to-dendrite transition (CDT) in directional solidification. We give a detailed description of the CDT by carefully examining the influence of the physical parameters, including: the Gibbs-Thomson coefficient Γ, the solute diffusivity Dl, the solute partition coefficient k0, and the liquidus slope ml. It is found that most of the parameters agree with the Kurz and Fisher (KF) criterion, except for k0. The intrinsic relations among the critical velocity Vcd, the cellular primary spacing λc,max, and the critical spacing λcd are investigated. Project supported by the National Natural Science Foundation of China (Grant Nos. 51271213 and 51323008), the National Basic Research Program of China (Grant No. 2011CB610402), the National High Technology Research and Development Program of China (Grant No. 2013AA031103), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20116102110016), and the China Postdoctoral Science Foundation (Grant No. 2013M540771).

  18. Stabilization/solidification of a municipal solid waste incineration residue using fly ash-based geopolymers.

    Luna Galiano, Y; Fernández Pereira, C; Vale, J


    The stabilization/solidification (S/S) of a municipal solid waste incineration (MSWI) fly ash containing hazardous metals such as Pb, Cd, Cr, Zn or Ba by means of geopolymerization technology is described in this paper. Different reagents such as sodium hydroxide, potassium hydroxide, sodium silicate, potassium silicate, kaolin, metakaolin and ground blast furnace slag have been used. Mixtures of MSWI waste with these kinds of geopolymeric materials and class F coal fly ash used as silica and alumina source have been processed to study the potential of geopolymers as waste immobilizing agents. To this end, the effects of curing conditions and composition have been tested. S/S solids are submitted to compressive strength and leaching tests to assess the results obtained and to evaluate the efficiency of the treatment. Compressive strength values in the range 1-9 MPa were easily obtained at 7 and 28 days. Concentrations of the metals leached from S/S products were strongly pH dependent, showing that the leachate pH was the most important variable for the immobilization of metals. Comparison of fly ash-based geopolymer systems with classical Portland cement stabilization methods has also been accomplished.

  19. Solidification of radioactive liquid wastes. A comparison of treatment options for spent resins and concentrates

    Roth, A. [Hansa Projekt Anlagentechnik GmbH, Hamburg (Germany); Willmann, F. [Westinghouse Electric Germany GmbH, Mannheim (Germany); Ebata, M. [Toshiba Corporation Power Systems Company, Isogo-Ku, Yokohama (Japan); Wendt, S. [Hansa Projekt Anlagentechnik GmbH, Hamburg (Germany)


    Ion exchange is one of the most common and effective treatment methods for liquid radioactive waste. However, spent ion exchange resins are considered to be problematic waste that in many cases require special approaches and pre-conditioning during its immobilization to meet the acceptance criteria for disposal. Because of the function that they fulfill, spent ion exchange resins often contain high concentrations of radioactivity and pose special handling and treatment problems. Another very common method of liquid radioactive waste treatment and water cleaning is the evaporation or diaphragm filtration. Both treatment options offer a high volume reduction of the total volume of liquids treated but generate concentrates which contain high concentrations of radioactivity. Both mentioned waste streams, spent resins as well as concentrates, resulting from first step liquid radioactive waste treatment systems have to be conditioned in a suitable manner to achieve stable waste products for final disposal. The most common method of treatment of such waste streams is the solidification in a solid matrix with additional inactive material like cement, polymer etc. In the past good results have been achieved and the high concentration of radioactivity can be reduced by adding the inactive material. On the other hand, under the environment of limited space for interim storage and the absence of a final repository site, the built-up of additional volume has to be considered as very critical. Moreover, corrosive effects on cemented drums during long-term interim storage at the surface have raised doubts about the long-term stability of such waste products. In order to avoid such disadvantages solidification methods have been improved in order to get a well-defined product with a better load factor of wastes in the matrix. In a complete different approach, other technologies solidify the liquid radioactive wastes without adding of any inactive material by means of drying

  20. Transport processes in directional solidification and their effects on microstructure development

    Mazumder, Prantik [Iowa State Univ., Ames, IA (United States)


    The processing of materials with unique electronic, mechanical, optical and thermal properties plays a crucial role in modern technology. The quality of these materials depend strongly on the microstructure and the solute/dopant fields in the solid product, that are strongly influenced by the intricate coupling of heat and mass transfer and melt flow in the growth systems. An integrated research program is developed that include precisely characterized experiments and detailed physical and numerical modeling of the complex transport and dynamical processes. Direct numerical simulation of the solidification process is carried out that takes into account the unsteady thermo-solutal convection in the vertical Bridgman crystal growth system, and accurately models the thermal interaction between the furnace and the ampoule by appropriately using experimentally measured thermal profiles. The flow instabilities and transitions and the nonlinear evolution following the transitions are investigated by time series and flow pattern analysis. A range of complex dynamical behavior is predicted with increasing thermal Rayleigh number. The route to chaos appears as: steady convection → transient mono-periodic → transient bi-periodic → transient quasi-periodic → transient intermittent oscillation-relaxation → stable intermittent oscillation-relaxation attractor. The spatio-temporal dynamics of the melt flow is found to be directly related to the spatial patterns observed experimentally in the solidified crystals. The application of the model to two phase Sn-Cd peritectic alloys showed that a new class of tree-like oscillating microstructure develops in the solid phase due to unsteady thermo-solutal convection in the liquid melt. These oscillating layered structures can give the illusion of band structures on a plane of polish. The model is applied to single phase solidification in the Al-Cu and Pb-Sn systems to characterize the effect of convection on the macroscopic

  1. Towards a Map of Solidification Cracking Risk in Laser Welding of Austenitic Stainless Steels

    Bermejo, María-Asunción Valiente; DebRoy, Tarasankar; Hurtig, Kjell; Karlsson, Leif; Svensson, Lars-Erik

    In this work, two series of specimens with Hammar and Svensson's Cr- and Ni-equivalents (Creq+Nieq) = 35 and 45 wt% were used to cover a wide range of austenitic grades. These were laser welded with different energy inputs achieving cooling rates in the range of 103 °C/s to 104 °C/s. As high cooling rates and rapid solidification conditions could favour fully austenitic solidification and therefore raise susceptibility to solidification cracking, the solidification modes of the laser welded specimens were compared to the ones experienced by the same alloys under arc welding conditions. It was found that high cooling rates experienced in laser welding promoted fully austenitic solidification for a wider range of compositions, for example specimens with (Creq+Nieq) = 35% under arc welding cooling conditions at 10 °C/s showed fully austenitic solidification up to Creq/Nieq = 1.30, whilst the same specimens laser cooled at 103 °C/s showed fully austenitic solidification up to Creq/Nieq = 1.50 and those cooled at 104 °C/s showed it up to Creq/Nieq = 1.68. Therefore, high cooling rates extended the solidification cracking risk to a wider range of Creq/Nieq values. This work also compares the cooling rates experimentally determined by thermocouples to the computed cooling rates calculated by a highly-advanced computational model. The distance between the thermocouple's wires and the thermal resistance of thermocouples together with the small size of the weld pools proved to be practical limitations in the experimental determination of cooling rates. However, an excellent agreement was found between computed and experimental solidus isotherms at high energy input settings. For low energy input settings cooling rate was in the order of magnitude of 104 °C/s, whilst for high energy input settings cooling rate was found to be in the order of magnitude of 103 °C/s.

  2. Application of the dual reciprocity boundary element method for numerical modelling of solidification process

    E. Majchrzak


    Full Text Available The dual reciprocity boundary element method is applied for numerical modelling of solidification process. This variant of the BEM is connected with the transformation of the domain integral to the boundary integrals. In the paper the details of the dual reciprocity boundary element method are presented and the usefulness of this approach to solidification process modelling is demonstrated. In the final part of the paper the examples of computations are shown.

  3. Part III. Kinetics of the (Zn - Coating Deposition During Stable and Meta-Stable Solidifications

    Wołczyński W.


    Full Text Available Two different steel substrates are applied to the hot dip (Zn - coating formation. The influence of the substrate composition on the (Zn - coating thickening is recorded. Morphologies of both coatings are compared to each other. The transition from stable into meta-stable solidification is revealed. The criterion for the competition between stable and meta-stable solidification is applied to justify the analyzed transition.

  4. Mechanics of transport phenomena in multi-component sessile drops with solidification

    Su, Yeong-Jen; Yang, Wen-Jei; Liu, Jiaching


    The mechanics of transport phenomena in multicomponent sessile drops with internal solidification is determined on the basis of an experimental study. A shadowgraph-schlieren system and a microscope-video system are used for the study. It is suggested that present data can be used to enhance the solid or crystal quality in a reduced-gravity environment where both thermo- and diffuso-capillary effects of solidification and crystal growth are dominant.

  5. Derivation and application of time step model in solidification process simulation


    The heat transfer during the casting solidification process includes the heat radiation of the high temperature casting and the mold, the heat convection between the casting and the mold, and the heat conduction inside the casting and from the casting to the mold. In this paper, a formula of time step in simulation of solidification is derived, considering the heat radiation, convection and conduction based on the conservation of energy. The different heat transfer conditions between the conv...

  6. Turbulent Fluid Flow and Heat Transfer Calculation in Mold Filling and Solidification Processes of Castings


    Based on the time-averaging equations and a modified engineering turbulence model, the mold filling and solidification processes of castings are approximately described. The algorithm for the control equations is briefly introduced, and some problems and improvement methods for the traditional method are also presented. Both calculation and tests proved that, comparing with the laminar fluid flow and heat transfer, the simulation results by using the turbulence model are closer to the real mold filling and solidification processes of castings.

  7. Modeling of Coalescence and Separation of Liquid Droplets During Solidification of Immiscible Alloys

    Lirong; Tong; Nagy; El-Kaddah


    Directional solidification methods are being used f or in-situ production of metallic immiscible composites. A quantitative understa nding of the dynamic behavior and growth kinetics of the nucleated second phase during solidification is necessary to produce homogeneous dispersion in solidifi ed composites. This paper presents a mathematical model for describing the grow th of nucleated dispersed phase in the two-liquid phase region ahead of the sol idification front and the entrapment of these droplets...

  8. Investigation of solidification behavior of the Sn-rich ternary Sn–Bi–Zn alloys

    S Mladenović


    Full Text Available Solidification properties and microstructure of six as-cast Sn–Bi–Zn alloys with 80 at.% of Sn and variable contents of Bi and Zn were experimentally investigated using the scanning electron microscopy (SEM with energy-dispersive X-ray spectroscopy (EDS and differential scanning calorimetry (DSC. The experimentally obtained results were compared with predicted phase equilibria according to the calculation of phase diagram (CALPHAD method and by the Scheil solidification simulation.


    Burns, H.


    The U.S. Department of Energy (DOE) tasked MSE Technology Applications, Inc. (MSE) with evaluating grouts that include gamma radiation shielding materials to solidify surrogates of liquid aqueous radioactive wastes from across the DOE Complex. The Savannah River Site (SRS) identified a High Activity Waste (HAW) that will be treated and solidified at the Waste Solidification Building (WSB) for surrogate grout testing. The HAW, which is produced at the Mixed Oxide Fuel Fabrication Facility (MFFF), is an acidic aqueous wastestream generated by the alkaline treatment process and the aqueous purification process. The HAW surrogate was solidified using Portland cement with and without the inclusion of different gamma radiation shielding materials to determine the shielding material that is the most effective to attenuate gamma radiation for this application.

  10. Two-dimensional phase-field study of competitive grain growth during directional solidification of polycrystalline binary alloy

    Takaki, Tomohiro; Ohno, Munekazu; Shibuta, Yasushi; Sakane, Shinji; Shimokawabe, Takashi; Aoki, Takayuki


    Selections of growing crystals during directional solidification of a polycrystalline binary alloy were numerically investigated using two-dimensional phase-field simulations. To accelerate the simulations, parallel graphics processing unit (GPU) simulations were performed using the GPU-rich supercomputer TSUBAME2.5 at the Tokyo Institute of Technology. Twenty simulations with a combination of five sets of different seed orientation distributions and four different temperature gradients covering dendritic and cellular growth regions were performed. The unusual grain selection phenomenon, in which the unfavorably oriented grains preferentially grow instead of the favorably oriented grains, was observed frequently. The unusual selection was more remarkable in the cellular structure than in the dendritic structure.

  11. Utilization of coal fly ash in solidification of liquid radioactive waste from research reactor.

    Osmanlioglu, Ahmet Erdal


    In this study, the potential utilization of fly ash was investigated as an additive in solidification process of radioactive waste sludge from research reactor. Coal formations include various percentages of natural radioactive elements; therefore, coal fly ash includes various levels of radioactivity. For this reason, fly ashes have to be evaluated for potential environmental implications in case of further usage in any construction material. But for use in solidification of radioactive sludge, the radiological effects of fly ash are in the range of radioactive waste management limits. The results show that fly ash has a strong fixing capacity for radioactive isotopes. Specimens with addition of 5-15% fly ash to concrete was observed to be sufficient to achieve the target compressive strength of 20 MPa required for near-surface disposal. An optimum mixture comprising 15% fly ash, 35% cement, and 50% radioactive waste sludge could provide the solidification required for long-term storage and disposal. The codisposal of radioactive fly ash with radioactive sludge by solidification decreases the usage of cement in solidification process. By this method, radioactive fly ash can become a valuable additive instead of industrial waste. This study supports the utilization of fly ash in industry and the solidification of radioactive waste in the nuclear industry.

  12. Geometrical modulus of a casting and its influence on solidification process

    F. Havlicek


    Full Text Available Object: The work analyses the importance of the known criterion for evaluating the controlled solidification of castings, so called geometrical modulus defined by N. Chvorinov as the first one. Geometrical modulus influences the solidification process. The modulus has such specificity that during the process of casting formation it is not a constant but its initial value decreases with the solidification progress because the remaining melt volume can decrease faster than its cooling surface.Methodology: The modulus is determined by a simple calculation from the ratio of the casting volume after pouring the metal in the mould to the cooled mould surface. The solidified metal volume and the cooled surface too are changed during solidification. That calculation is much more complicated. Results were checked up experimentally by measuring the temperatures in the cross-section of heavy steel castings during cooling them.Results: The given experimental results have completed the original theoretical calculations by Chvorinov and recent researches done with use of numerical calculations. The contribution explains how the geometrical modulus together with the thermal process in the casting causes the higher solidification rate in the axial part of the casting cross-section and shortening of solidification time. Practical implications: Change of the geometrical modulus negatively affects the casting internal quality. Melt feeding by capillary filtration in the dendritic network in the casting central part decreases and in such a way the shrinkage porosity volume increases. State of stress character in the casting is changed too and it increases.

  13. Microstructures, micro-segregation and solidification path of directionally solidified Ti-45Al-5Nb alloy

    Liang-shun Luo


    Full Text Available To investigate the effect of solidification parameters on the solidification path and microstructure evolution of Ti-45Al-5Nb (at.% alloy, Bridgman-type directional solidification and thermodynamics calculations were performed on the alloy. The microstructures, micro-segregation and solidification path were investigated. The results show that the β phase is the primary phase of the alloy at growth rates of 5-20 μm•s-1 under the temperature gradients of 15-20 K•mm-1, and the primary phase is transformed into an α phase at relatively higher growth rates (V >20 μm•s-1. The mainly S-segregation and β-segregation can be observed in Ti-45Al-5Nb alloy at a growth rate of 10 μm•s-1 under a temperature gradient of 15 K•mm-1. The increase of temperature gradient to 20 K•mm-1 can eliminate β-segregation, but has no obvious effect on S-segregation. The results also show that 5 at.% Nb addition can expand the β phase region, increase the melting point of the alloy and induce the solidification path to become complicated. The equilibrium solidification path of Ti-45Al-5Nb alloy can be described as , in which βR and γR mean the residual β and γ.

  14. Modeling of Cooling and Solidification of TNT based Cast High Explosive Charges

    A. Srinivas Kumar


    Full Text Available Cast trinitrotoluene (TNT based high explosive charges suffer from different defects such as cracks, voids, etc. One of the quality control measures is to cool the castings gradually, so that the entire charge solidifies without a large temperature gradient from core to the periphery of the cast charge. The fact that the solidification of high explosive casting starts from the periphery (cooler side and travels towards the center enables us to predict the solidification profile of TNT based explosive castings. Growth of solidification thickness and cooling temperature profiles of TNT based cast high explosive charges are predicted as functions of time and space using unsteady state heat transfer principles, associated with heat balance at solid to liquid interface as a moving boundary of solidification. This will enable adoption of proper quality control during solidification of the molten TNT to eliminate inherent drawbacks of cast high explosive charges. The solidification profiles of TNT based cast charges under controlled and natural conditions are predicted and the model is validated against 145 mm diameter TNT cast charge which is found to be in broad agreement with experiments.Defence Science Journal, Vol. 64, No. 4, July 2014, pp.339-343, DOI:

  15. The solidification of two-phase heterogeneous materials:Theory versus experiment

    KIM; Tongbeum


    The solidification behavior of two-phase heterogeneous materials such as close-celled aluminum foams was analytically studied.The proposed analytical model can precisely predict the location of solidification front as well as the full solidification time for a two-phase heterogeneous material composed of aluminum melt and non-conducting air pores.Experiments using distilled water simulating the aluminum melt to be solidified(frozen)were subsequently conducted to validate the analytical model for two selected porosities(ε),ε=0 and 0.5.Full numerical simulations with the method of finite difference were also performed to examine the influence of pore shape on solidification.The remarkable agreement between theory and experiment suggests that the delay of solidification in the two-phase heterogeneous material is mainly caused by the reduction of bulk thermal conductivity due to the presence of pores,as this is the sole mechanism accounted for by the analytical model for solidification in a porous medium.

  16. Solidification kinetics of a Cu-Zr alloy: ground-based and microgravity experiments

    Galenko, P. K.; Hanke, R.; Paul, P.; Koch, S.; Rettenmayr, M.; Gegner, J.; Herlach, D. M.; Dreier, W.; Kharanzhevski, E. V.


    Experimental and theoretical results obtained in the MULTIPHAS-project (ESA-European Space Agency and DLR-German Aerospace Center) are critically discussed regarding solidification kinetics of congruently melting and glass forming Cu50Zr50 alloy samples. The samples are investigated during solidification using a containerless technique in the Electromagnetic Levitation Facility [1]. Applying elaborated methodologies for ground-based and microgravity experimental investigations [2], the kinetics of primary dendritic solidification is quantitatively evaluated. Electromagnetic Levitator in microgravity (parabolic flights and on board of the International Space Station) and Electrostatic Levitator on Ground are employed. The solidification kinetics is determined using a high-speed camera and applying two evaluation methods: “Frame by Frame” (FFM) and “First Frame - Last Frame” (FLM). In the theoretical interpretation of the solidification experiments, special attention is given to the behavior of the cluster structure in Cu50Zr50 samples with the increase of undercooling. Experimental results on solidification kinetics are interpreted using a theoretical model of diffusion controlled dendrite growth.

  17. The R/D of high power proton accelerator technology in China

    Guan Xialing


    In China, a multipurpose verification system as a first phase of our ADS program consists of a low energy accelerator (150 MeV/3 mA proton LINAC) and a swimming pool light water subcritical reactor. In this paper the activities of HPPA technology related to ADS in China, which includes the intense proton ECR source, the RFQ accelerator and some other technology of HPPA, are described.

  18. Processing of alnico permanent magnets by advanced directional solidification methods

    Zou, Min; Johnson, Francis; Zhang, Wanming; Zhao, Qi; Rutkowski, Stephen F.; Zhou, Lin; Kramer, Matthew J.


    Advanced directional solidification methods have been used to produce large (>15 cm length) castings of Alnico permanent magnets with highly oriented columnar microstructures. In combination with subsequent thermomagnetic and draw thermal treatment, this method was used to enable the high coercivity, high-Titanium Alnico composition of 39% Co, 29.5% Fe, 14% Ni, 7.5% Ti, 7% Al, 3% Cu (wt%) to have an intrinsic coercivity (Hci) of 2.0 kOe, a remanence (Br) of 10.2 kG, and an energy product (BH)max of 10.9 MGOe. These properties compare favorably to typical properties for the commercial Alnico 9. Directional solidification of higher Ti compositions yielded anisotropic columnar grained microstructures if high heat extraction rates through the mold surface of at least 200 kW/m2 were attained. This was achieved through the use of a thin walled (5 mm thick) high thermal conductivity SiC shell mold extracted from a molten Sn bath at a withdrawal rate of at least 200 mm/h. However, higher Ti compositions did not result in further increases in magnet performance. Images of the microstructures collected by scanning electron microscopy (SEM) reveal a majority α phase with inclusions of secondary αγ phase. Transmission electron microscopy (TEM) reveals that the α phase has a spinodally decomposed microstructure of FeCo-rich needles in a NiAl-rich matrix. In the 7.5% Ti composition the diameter distribution of the FeCo needles was bimodal with the majority having diameters of approximately 50 nm with a small fraction having diameters of approximately 10 nm. The needles formed a mosaic pattern and were elongated along one crystal direction (parallel to the field used during magnetic annealing). Cu precipitates were observed between the needles. Regions of abnormal spinodal morphology appeared to correlate with secondary phase precipitates. The presence of these abnormalities did not prevent the material from displaying superior magnetic properties in the 7.5% Ti composition

  19. Oscillatory cellular patterns in three-dimensional directional solidification.

    Tourret, D; Debierre, J-M; Song, Y; Mota, F L; Bergeon, N; Guérin, R; Trivedi, R; Billia, B; Karma, A


    We present a phase-field study of oscillatory breathing modes observed during the solidification of three-dimensional cellular arrays in microgravity. Directional solidification experiments conducted onboard the International Space Station have allowed us to observe spatially extended homogeneous arrays of cells and dendrites while minimizing the amount of gravity-induced convection in the liquid. In situ observations of transparent alloys have revealed the existence, over a narrow range of control parameters, of oscillations in cellular arrays with a period ranging from about 25 to 125 min. Cellular patterns are spatially disordered, and the oscillations of individual cells are spatiotemporally uncorrelated at long distance. However, in regions displaying short-range spatial ordering, groups of cells can synchronize into oscillatory breathing modes. Quantitative phase-field simulations show that the oscillatory behavior of cells in this regime is linked to a stability limit of the spacing in hexagonal cellular array structures. For relatively high cellular front undercooling (i.e., low growth velocity or high thermal gradient), a gap appears in the otherwise continuous range of stable array spacings. Close to this gap, a sustained oscillatory regime appears with a period that compares quantitatively well with experiment. For control parameters where this gap exists, oscillations typically occur for spacings at the edge of the gap. However, after a change of growth conditions, oscillations can also occur for nearby values of control parameters where this gap just closes and a continuous range of spacings exists. In addition, sustained oscillations at to the opening of this stable gap exhibit a slow periodic modulation of the phase-shift among cells with a slower period of several hours. While long-range coherence of breathing modes can be achieved in simulations for a perfect spatial arrangement of cells as initial condition, global disorder is observed in both

  20. Impact-activated solidification of cornstarch and water suspensions

    Waitukaitis, Scott Russell

    Liquids typically offer little resistance to impacting objects . Surprisingly, dense suspensions of liquids mixed with micron-sized particles can provide tremendous impact resistance, even though they appear liquid like when left at rest or perturbed lightly. The most well-known example is a dense mixture of cornstarch and water, which can easily provide enough impact resistance to allow a full-grown person to run across its surface. Previous studies have linked this so-called ``shear thickening'' to experiments carried out under steady state shear and attributed it to hydrodynamic interactions or granular dilation. However, neither of these explanations alone can account for the stress scales required to keep a running person above the free surface. This thesis investigates the mechanism for this impact resistance in dense suspensions. We begin by studying impact directly and watching a rod as it strikes the surface of a dense suspension of cornstarch and water. Using high-speed video and embedded force and acceleration sensing, we show that the rod motion leads to the rapid growth of a solid-like object below the impact site. With X-ray videography to see the dynamics of the suspension interior and laser sheet measurements of the surface profile, we show how this solid drags on the surrounding suspension, creating substantial peripheral flow and leading to the rapid extraction of the impactor's momentum. Suspecting that the solidification below the rod may be related to jamming of the particle sub-phase, we carry out 2D experiments with macroscopic disks to show how uniaxial compression of an initially unjammed system can lead to dynamic jamming fronts. In doing so, we show how these fronts are sensitive to the system's initial packing fraction relative to the point at which it jams and also discover that the widths of these fronts are related to a diverging correlation length. Finally, we take these results back to the suspension, where we perform careful, speed

  1. Effect of strontium and solidification rate on eutectic grain structure in an AI-13 wt% Si alloy

    Liao Hengcheng; Bi Juanjuan; Zhang Min; Ding Ke; Jiang Yunfeng; Cai Mingdong


    The influence of strontium addition and solidification rate on eutectic grain structure in a near-eutectic AI-Si alloy was investigated. The characteristic temperature of eutectic nucleation (TN),minimum temperature prior to recalescence (TM),and the growth temperature (TG) during cooling were determined by quantitative thermal analysis. All characteristic temperatures were found to decrease continuously with increasing Sr content and solidification rate. Microstructural analysis also revealed that the eutectic grain size decreases with increasing Sr content and solidification rate. Such eutectic grain refinement is attributed to the increased actual under-cooling ahead of the liquid/solid interface during solidification.

  2. The size effect on solidification in eutectic bismuth-tin (Bi-Sn) nanowires by in-situ annealing processes.

    Chen, Shih-Hsun; Wang, Chiu-Yen; Chen, Lih-Juann; Liu, Tzeng-Feng; Chaol, Chuen-Guang


    The size effects on solidification and the formation mechanism of the segmented eutectic Bi-43Sn nanowires during in situ annealing have been investigated. A directional solidification along the wire axis limits the segmented eutectic nanowire to arrange axially during the in situ annealing processes due to directional solidification. In 70 nm nanowires, the small size confines the convection in liquid, which results in differences in the microstructure and composition profiles between 70 and 200 nm nanowires. In the vacuum hydraulic pressure injection process, the directional cooling helps the formation of single crystal, and the isotropic solidification leads to polycrystalline microstructure.

  3. Stabilization/solidification of munition destruction waste by asphalt emulsion.

    Cervinkova, Marketa; Vondruska, Milan; Bednarik, Vratislav; Pazdera, Antonin


    Destruction of discarded military munitions in an explosion chamber produces two fractions of hazardous solid waste. The first one is scrap waste that remains in the chamber after explosion; the second one is fine dust waste, which is trapped on filters of gas products that are exhausted from the chamber after explosion. The technique of stabilization/solidification of the scrap waste by asphalt emulsion is described in this paper. The technique consists of simple mixing of the waste with anionic asphalt emulsion, or two-step mixing of the waste with cationic asphalt emulsion. These techniques are easy to use and the stabilized scrap waste proves low leachability of contained heavy metals assessed by TCLP test. Hence, it is possible to landfill the scrap waste stabilized by asphalt emulsion. If the dust waste, which has large specific surface, is stabilized by asphalt emulsion, it is not fully encapsulated; the results of the leaching tests do not meet the regulatory levels. However, the dust waste solidified by asphalt emulsion can be deposited into an asphalted disposal site of the landfill. The asphalt walls of the disposal site represent an efficient secondary barrier against pollutant release.

  4. Solidification microstructures in single-crystal stainless steel melt pools

    Sipf, J.B.; Boatner, L.A.; David, S.A.


    Development of microstructure of stationary melt pools of oriented stainless steel single crystals (70%Fe-15%Ni-15%Cr was analyzed. Stationary melt pools were formed by electron-beam and gas-tungsten-arc heating on (001), (011), and (111) oriented planes of the austenitic, fcc-alloy crystals. Characterization and analysis of resulting microstructure was carried out for each crystallographic plane and welding method. Results showed that crystallography which favors ``easy growth`` along the <100> family of directions is a controlling factor in the microstructural formation along with the melt-pool shape. The microstructure was found to depend on the melting method, since each method forms a unique melt-pool shape. These results are used in making a three-dimensional reconstruction of the microstructure for each plane and melting method employed. This investigation also suggests avenues for future research into the microstructural properties of electron-beam welds as well as providing an experimental basis for mathematical models for the prediction of solidification microstructures.

  5. Multiphysics and multiscale modelling of ductile cast iron solidification

    D. Gurgul


    Full Text Available The presented model of ductile cast iron solidification is a typical sample of multiphysics and multiscale engineering system. This model takes into consideration the different time and spatial scales of accounted phenomenon of microstructure formation: heat diffusion, components mass diffusion in the liquid and solid phases, thermodynamic of phase transformation under the condition of inhomogeneous chemical composition of growing and vanishing phases, phase interface kinetics and grains nucleation.The results of two-dimensional modelling of the microstructure formation in the ductile cast iron (so called - Ductile Iron - DI are pre-sented. The cellular automaton model (CA was used for the simulation. Six states of CA cells were adopted to three phases above men-tioned (liquid, austenite and graphite and to three two-phase interfaces. For the modelling of concentration and temperature fields the numerical solution was used. The parabolic nonlinear differential equa-tions with a source term were solved by using the finite difference method and explicit scheme. The overlapping lattices with the same spatial step were used for the concentration field modelling and for the CA. The time scale of the temperature field for this lattice is about 104 times shorter. Due to above reasons the another lattice was used with a multiple spatial step and the same time step.

  6. Acceleration of solidification of mining mortars; Erstarrungsbeschleunigung von Bergbaumoerteln

    Schade, S.; Mueller, A. [Weimar Univ. (Germany). Lehrstuhl ``Aufbereitung von Baustoffen und Wiederverwertung``


    The aim was to establish in laboratory tests to what extent water glass can be used as a solidification accelerator for free-flowing mining mortars. The following modification possibilities resulted for the mortar systems used in the mining industry: The currently used accelerator water glass can be replaced by chloride-based accelerators. The necessary added quantity is 3 to 5% by weight. The use of a granulate is one way of improving the processibility without increasing the water/solids ratio. The new system can make an important contribution to cost reduction in the mining industry. The mining mortar system modified with granulate and processed with accelerator A could acquire importance as a stowing material in particular for the eastern German potash mining industry in hard salt. (orig.) [Deutsch] In Laborversuchen sollte herausgefunden werden, inwieweit Wasserglas als Erstarrungsbeschleuniger fuer Bergbaufliessmoertel ersetzt werden kann. Folgende Modifizierungsmoeglichkeiten fuer die im Bergbau verwendeten Moertelsysteme ergaben sich: Der momentan eingesetzte Beschleuniger Wasserglas kann durch chloridhaltige Beschleuniger abgeloest werden. Die notwendige Zugabemenge betraegt 3 bis 5 Massen-%. Die Verwendung eines koernigen Granulats zeigt einen Weg fuer die Verbesserung der Verarbeitbarkeit ohne Erhoehung des W/F-Werts auf. Das neue System kann fuer den Bergbau einen entscheidenden Beitrag zur Kostensenkung leisten. Besonders fuer den ostdeutschen Kalibergbau im Hartsalz koennte das mit Granulat modifizierte und mit dem Beschleuniger A verarbeitete Bergbaumoertelsystem als Hohlraumversatz Bedeutung erlangen. (orig.)

  7. Superior metallic alloys through rapid solidification processing (RSP) by design

    Flinn, J.E. [Idaho National Engineering Laboratory, Idaho Falls, ID (United States)


    Rapid solidification processing using powder atomization methods and the control of minor elements such as oxygen, nitrogen, and carbon can provide metallic alloys with superior properties and performance compared to conventionally processing alloys. Previous studies on nickel- and iron-base superalloys have provided the baseline information to properly couple RSP with alloy composition, and, therefore, enable alloys to be designed for performance improvements. The RSP approach produces powders, which need to be consolidated into suitable monolithic forms. This normally involves canning, consolidation, and decanning of the powders. Canning/decanning is expensive and raises the fabrication cost significantly above that of conventional, ingot metallurgy production methods. The cost differential can be offset by the superior performance of the RSP metallic alloys. However, without the performance database, it is difficult to convince potential users to adopt the RSP approach. Spray casting of the atomized molten droplets into suitable preforms for subsequent fabrication can be cost competitive with conventional processing. If the fine and stable microstructural features observed for the RSP approach are preserved during spray casing, a cost competitive product can be obtained that has superior properties and performance that cannot be obtained by conventional methods.

  8. Solidifications/stabilization treatability study of a mixed waste sludge

    Spence, R.D. [Oak Ridge National Lab., TN (United States); Stine, E.F. [International Technologies Corp., Knoxville, TN (United States). Technology Development Lab.


    The Department of Energy Oak Ridge Operations Office signed a Federal Facility Compliance Agreement with the US Environmental Protection Agency Region IV regarding mixed wastes from the Oak Ridge Reservation (ORR) subject to the land disposal restriction provisions of the Resource Conservation and Recovery Act (RCRA). This agreement required treatability studies of solidification/stabilization (S/S) on mixed wastes from the ORR. This paper reports the results of the cementitious S/S studies conducted on a waste water treatment sludge generated from biodenitrification and heavy metals precipitation. For the cementitious waste forms, the additives tested were Portland cement, ground granulated blast furnace slag, Class F fly ash, and perlite. The properties measured on the treated waste were density, free-standing liquid, unconfined compressive strength, and TCLP performance. Spiking up to 10,000, 10,000, and 4,400 mg/kg of nickel, lead, and cadmium, respectively, was conducted to test waste composition variability and the stabilization limitations of the binding agents. The results indicated that nickel, lead and cadmium were stabilized fairly well in the high pH hydroxide-carbonate- ``bug bones`` sludge, but also clearly confirmed the established stabilization potential of cementitious S/S for these RCRA metals.

  9. Hydrothermal Solidification of Diatomite and Its Heat Insulating Property

    TONG Yu; GAO Jian; XIA Feng; XU Dawei; SONG Lili; YANG Wenrui; ZENG You


    To meet the commercial requirements of inorganic heat insulators,the mixture of diatomite and Ca(OH) 2 are evenly dispersed,mold-compacted,and then hydrothermally solidified due to the formation of tobermorite under an autoclaved process.Systematic investigations of the preparation conditions (including mix ratio,autoclaved factors,mold pressure,etc)were carried out to optimize the serving properties of such toberrnorite-based products.As a result,a compressive strength of more than 30 MPa was realized for the specimen in high density( about 1.30( g·cm-3) ).On the contrary,the specimen in light weight for example 0.63 ( g ·cm-3 ) typically showed a thermal conductivity of around 0.12 ( W· m-1· K-1 ).The present work developed a feasible way to produce and to control the serving properties of diatomite-based heat insulators by a process of hydrothermal solidification,in which the optimized value of Ca/Si ratio was proposed to be 0.6 ~ 0.7,while the water content is 25 % in weight,and hydrothermal reaction is performed at 180 ℃ for no more than 24 hours.

  10. Evolution of grain structures during directional solidification of silicon wafers

    Lin, H. K.; Wu, M. C.; Chen, C. C.; Lan, C. W.


    The evolution of grain structures, especially the types of grain boundaries (GBs), during directional solidification is crucial to the electrical properties of multicrystalline silicon used for solar cells. To study this, the electric molten zone crystallization (EMZC) of silicon wafers at different drift speeds from 2 to 6 mm/min was considered. It was found that orientation was dominant at the lower drift velocity, while orientation at the higher drift velocity. Most of the non-∑GBs tended to align with the thermal gradient, but some tilted toward the unfavorable grains having higher interfacial energies. On the other hand, the tilted ∑3GBs tended to decrease during grain competition, except at the higher speed, where the twin nucleation became frequent. The competition of grains separated by ∑GBs could be viewed as the interactions of GBs that two coherent ∑3n GBs turned into one ∑3nGB following certain relations as reported before. On the other hand, when ∑ GBs met non-∑ GBs, the non-∑ GBs remained which explained the decrease of ∑ GBs at the lower speed.

  11. Pulsatile instability in rapid directional solidification - Strongly-nonlinear analysis

    Merchant, G. J.; Braun, R. J.; Brattkus, K.; Davis, S. H.


    In the rapid directional solidification of a dilute binary alloy, analysis reveals that, in addition to the cellular mode of Mullins and Sekerka (1964), there is an oscillatory instability. For the model analyzed by Merchant and Davis (1990), the preferred wavenumber is zero; the mode is one of pulsation. Two strongly nonlinear analyses are performed that describe this pulsatile mode. In the first case, nonequilibrium effects that alter solute rejection at the interface are taken asymptotically small. A nonlinear oscillator equation governs the position of the solid-liquid interface at leading order, and amplitude and phase evolution equations are derived for the uniformly pulsating interface. The analysis provides a uniform description of both subcritical and supercritical bifurcation and the transition between the two. In the second case, nonequilibrium effects that alter solute rejection are taken asymptotically large, and a different nonlinear oscillator equation governs the location of the interface to leading order. A similar analysis allows for the derivation of an amplitude evolution equation for the uniformly pulsating interface. In this case, the bifurcation is always supercritical. The results are used to make predictions about the characteristics of solute bands that would be frozen into the solid.

  12. Directional Solidification of Bi-Sn on USMP-4

    Abbaschian, Reza; deGroh, H., III; Leonardi, E.; Timchenko, V.; deVahlDavis, G.


    The experiments used MEPHISTO hardware to study the solidification and melting behavior of bismuth alloyed with 1 at% tin. Three samples, each approximately 900 mm long and 6mm in diameter, were used. A portion of each sample also included a 2 mm diameter growth capillary, to assist in the formation of a single grain. One sample provided the Seebeck voltage generated during melting and freezing processes. Another provided temperature data and Peltier pulsed demarcation of the interface shape for post flight analysis. The third sample provided resistance and growth velocity measurements, as well as additional thermal data. The third sample was also quenched at the end of the mission to preserve the composition of the liquid near the interface for post flight determination. A total of 450mm of directionally solidified samples were preserved for post mission structural and compositional characterization. Substantial differences were observed in the Seebeck signal between the ground-based experiments and the space-based experiments. The temperature gradient in the liquid for the ground-based experiments was significantly lower than the temperature gradient in the liquid for the space-based experiments.

  13. Stabilization and solidification of chromium-contaminated soil

    Cherne, C.A.; Thomson, B.M. [Univ. of New Mexico, Albuquerque, NM (United States). Civil Engineering Dept.; Conway, R. [Sandia National Labs., Albuquerque, NM (United States)


    Chromium-contaminated soil is a common environmental problem in the United States as a result of numerous industrial processes involving chromium. Hexavalent chromium [Cr(VI)] is the species of most concern because of its toxicity and mobility in groundwater. One method of diminishing the environmental impact of chromium is to reduce it to a trivalent oxidation state [Cr(III)], in which it is relatively insoluble and nontoxic. This study investigated a stabilization and solidification process to minimize the chromium concentration in the Toxicity Characteristic Leaching Procedure (TCLP) extract and to produce a solidified waste form with a compressive strength in the range of 150 to 300 pounds per square inch (psi). To minimize the chromium in the TCLP extract, the chromium had to be reduced to the trivalent oxidation state. The average used in this study was an alluvium contaminated with chromic and sulfuric acid solutions. The chromium concentration in the in the in situ soil was 1212 milligrams per kilogram (mg/kg) total chromium and 275 mg/kg Cr(VI). The effectiveness of iron, ferrous sulfate to reduce Cr(VI) was tested in batch experiments.

  14. A phenomenological approach of solidification of polymeric phase change materials

    Bahrani, Seyed Amir; Royon, Laurent; Abou, Bérengère; Osipian, Rémy; Azzouz, Kamel; Bontemps, André


    Phase Change Materials (PCMs) are widely used in thermal energy storage and thermal management systems due to their small volume for a given stored energy and their capability for maintaining nearly constant temperatures. However, their performance is limited by their low thermal conductivity and possible leaks while in the liquid phase. One solution is to imprison the PCM inside a polymer mesh to create a Polymeric Phase Change Material (PPCM). In this work, we have studied the cooling and solidification of five PPCMs with different PCMs and polymer fractions. To understand the heat transfer mechanisms involved, we have carried out micro- and macrorheological measurements in which Brownian motion of tracers embedded in PPCMs has been depicted and viscoelastic moduli have been measured, respectively. Beyond a given polymer concentration, it was shown that the Brownian motion of the tracers is limited by the polymeric chains and that the material exhibits an elastic behavior. This would suggest that heat transfer essentially occurs by conduction, instead of convection. Experiments were conducted to measure temperature variation during cooling of the five samples, and a semi-empirical model based on a phenomenological approach was proposed as a practical tool to choose and size PPCMs.

  15. Melt flow effect on interface stability during directional solidification

    Fedorov, O. P.; Mashkovskiy, A. G.


    In the framework of the phenomenological macroscopic continuum theory using the approximation of a flat frontier layer the stability of solid-liquid interface at the directional solidification under melt motion along the interface is studied. The stability conditions are reduced to determination of eigenvalues of boundary value problem for infinitesimal disturbances of stationary process. In case of stagnant melt it is shown that in the plane "wave number-pulling rate" there are two areas of instability for low and large pulling rates divided by the area of steady-steady growth. Neutral stability curve calculated for rather large pulling rates for succinonitrile-acetone (SCN-Ac) system is close to the relevant values received by Mullins and Sekerka, while the absolute values of critical growth rates are of the same order of magnitude as the experimental ones. Melt flow along the interface leads to emergence of the third area of instability which is characterized by small values of wave numbers. When increasing the melt flow rate the area of instability extends towards great values of wave numbers.

  16. Solidification crack susceptibility of aluminum alloy weld metals


    The susceptibilities of the three aluminum alloys to solidification crack were studied with trans-varestraint tests and tensile tests at elevated temperature. Their metallurgical characteristics, morphologies of the fractured surface and dynamic cracking behaviors at elevated temperature were analyzed with a series of micro-analysis methods. The results show that dynamic cracking models can be classified into three types. The first model has the healing effect which is called type A. The second is the one with deformation and breaking down of metal bridge, called type B. The last one is with the separation of liquid film along grain boundary, called type C.Moreover, the strain rate has different effects on crack susceptibility of aluminum alloys with different cracking models. ZL101 and 5083 alloys belong to type A and type C cracking model respectively, in which strain rate has greater effect on eutectic healing and plastic deformation of metal bridge. 6082 alloy is type B cracking model in which the strain rate has little effect on the deformation ability of the liquid film.

  17. Experimental study of directional solidification of aqueous ammonium chloride solution

    Chen, C. F.; Chen, Falin


    Directional solidification experiments have been carried out using the analog casting system of NH4Cl-H2O solution by cooling it from below with a constant-temperature surface ranging from -31.5 C to +11.9 C. The NH4Cl concentration was 26 percent in all solutions, with a liquidus temperature of 15 C. It was found that finger convection occurred in the fluid region just above the mushy layer in all experiments. Plume convection with associated chimneys in the mush occurred in experiments with bottom temperatures as high as +11.0 C. However, when the bottom temperature was raised to +11.9 C, no plume convection was observed, although finger convection continued as usual. A method has been devised to determine the porosity of the mush by computed tomography. Using the mean value of the porosity across the mush layer and the permeability calculated by the Kozeny-Carman relationship, the critical solute Rayleigh number across the mush layer for onset of plume convection was estimated to be between 200 and 250.

  18. Directional solidification of Al-Cu-Ag alloy

    Boeyuek, U.; Kaya, H. [Erciyes University, Department of Science Education, Education Faculty, Kayseri (Turkey); Marasli, N.; Keslioglu, K. [Erciyes University, Department of Physics, Faculty Arts and Sciences, Kayseri (Turkey); Cadirli, E. [Nigde University, Department of Physics, Faculty Arts and Sciences, Nigde (Turkey)


    Al-Cu-Ag alloy was prepared in a graphite crucible under a vacuum atmosphere. The samples were directionally solidified upwards under an argon atmosphere with different temperature gradients (G=3.99-8.79 K/mm), at a constant growth rate (V=8.30 {mu}m/s), and with different growth rates (V=1.83-498.25 {mu}m/s), at a constant gradient (G=8.79 K/mm) by using the Bridgman type directional solidification apparatus. The microstructure of Al-12.80-at.%-Cu-18.10-at.%-Ag alloy seems to be two fibrous and one lamellar structure. The interlamellar spacings ({lambda}) were measured from transverse sections of the samples. The dependence of interlamellar spacings ({lambda}) on the temperature gradient (G) and the growth rate (V) were determined by using linear regression analysis. According to these results it has been found that the value of {lambda} decreases with the increase of values of G and V. The values of {lambda} {sup 2}V were also determined by using the measured values of {lambda} and V. The experimental results were compared with two-phase growth from binary and ternary eutectic liquid. (orig.)

  19. Tests of absorbents and solidification techniques for oil wastes

    Lin, M.; MacKenzie, D. R.


    A representative of each of six classes of commonly used adsorbents was chosen for a series of tests. After reviewing ASTM and other related standard tests, uncomplicated procedures were developed for carrying out specific tests to determine absorbency for simulated oil waste and for water, under static and simulated transportation (repetitive shock) conditions. The tests were then applied to the six representative absorbents. Solidification tests were performed using these absorbents saturated with oil and loaded to 50% of saturation. The binders used were Portland I cement and Delaware Custom Material (DCM) cement shale silicate. Samples were checked for proper set, and the amounts of free liquid were measured. Another series of tests was performed on samples of simulated oil waste without absorbent, using Portland cement and DCM cement shale silicate. Samples were checked for proper set, free liquid was measured, and compressive strengths were determined. The state-of-the-art parameters were identified which satisfy NRC disposal criteria for solidified radioactive waste. The literature was reviewed for alternative methods of managing oil wastes. Conclusions are drawn on the relative utility of the various methods. 17 references, 3 tables.

  20. "Legālo narkotiku" rāmējumu salīdzinājums mediju saturā, ekspertu un sabiedrības pārstāvju vērtējumos

    Kovalevskis, Mikus


    Bakalaura darba tēma ir „”Legālo narkotiku” rāmējumu salīdzinājums mediju saturā, ekspertu un sabiedrības pārstāvju vērtējumos”. Pētījuma mērķis ir uzzināt, cik aktuāla ir „legālo narkotiku” problemātika interneta portālu un saturā un salīdzināt, kāda attieksme par „legālajām narkotikām” dominē mediju publikācijās, sabiedrības pārstāvju un ekspertu viedokļos, un, kā šie jautājumi tiek rāmēti. Veicot rāmējumu analīzi, konstatēts, ka mediji neinformē kā pasargāties no „legāl...

  1. Solidification drug nanosuspensions into nanocrystals by freeze-drying: a case study with ursodeoxycholic acid.

    Ma, Yue-Qin; Zhang, Zeng-Zhu; Li, Gang; Zhang, Jing; Xiao, Han-Yang; Li, Xian-Fei


    To elucidate the effect of solidification processes on the redispersibility of drug nanocrystals (NC) during freeze-drying, ursodeoxycholic acid (UDCA) nanosuspensions were transformed into UDCA-NC via different solidification process included freezing and lyophilization. The effect of different concentrations of stabilizers and cryoprotectants on redispersibility of UDCA-NC was investigated, respectively. The results showed that the redispersibility of UDCA-NC was RDI-20 °C lyophilization. The hydroxypropylmethylcellulose and PVPK30 were effective to protect UDCA-NC from damage during lyophilization, which could homogeneously adsorb into the surface of NC to prevent from agglomerates. The sucrose and glucose achieved excellent performance that protected UDCA-NC from crystal growth during lyophilization, respectively. It was concluded that UDCA-NC was subjected to agglomeration during solidification transformation, and the degree of agglomeration suffered varied with the type and the amounts of stabilizers used, as well as different solidification conditions. The PVPK30-sucrose system was more effective to protect UDCA-NC from the damage during solidification process.

  2. Solidification in Soft-Contact Continuous Casting Mold with Alternating Electromagnetic Field


    A three-dimensional coupled mathematical model for steel flow and solidification in a soft-contact EMC (Electro-Magnetic Casting) mold was developed. Non-staggered grid system with BFC (Body Fitted Coordinate) for the steel flow and solidification considering the complex geometry of the electromagnetic mold and the irregular meniscus shape of the melt were used. This mathematical model was applied to investigate the steel flow and solidification, and the effect of electromagnetic parameters on steel solidification in a 100 mm×100 mm square billet soft-contact mold. Numerical results showed that the electromagnetic induction heat mainly affects the distribution of steel temperature at upper part of EMC mold especially in the vicinity of meniscus. Consequently the steel temperature near the free surface is increased distinctly, and the hot-top condition is formed at the top of mold. It was clearly seen that the solidification start point shifts downward under the three-phase point by applying alternative electromagnetic field. As a result, the initial shell thickness gets thinner and the shell length shorter.


    Charles W. Solbrig; Kenneth J. Bateman


    The goal of this work is to produce a ceramic waste form (CWF) that permanently occludes radioactive waste. This is accomplished by absorbing radioactive salts into zeolite, mixing with glass frit, heating to a molten state 915 C to form a sodalite glass matrix, and solidifying for long-term storage. Less long term leaching is expected if the solidifying cooling rate doesn’t cause cracking. In addition to thermal stress, this paper proposes that a stress is formed during solidification which is very large for fast cooling rates during solidification and can cause severe cracking. A solidifying glass or ceramic cylinder forms a dome on the cylinder top end. The temperature distribution at the time of solidification causes the stress and the dome. The dome height, “the length deficit,” produces an axial stress when the solid returns to room temperature with the inherent outer region in compression, the inner in tension. Large tensions will cause cracking of the specimen. The temperature deficit, derived by dividing the length deficit by the coefficient of thermal expansion, allows solidification stress theory to be extended to the circumferential stress. This paper derives the solidification stress theory, gives examples, explains how to induce beneficial stresses, and compares theory to experimental data.

  4. A combined enthalpy / front tracking method for modelling melting and solidification in laser welding

    Duggan, G.; Mirihanage, W. U.; Tong, M.; Browne, D. J.


    The authors present an integrated meso-scale 2D numerical model for the simulation of laser spot welding of a Fe-Cr-Ni steel. The melting of the parent materials due to the applied heating power is an important phenomenon, leading to the formation of the weld pool and the subsequent conditions from which solidification proceeds. This model deals with the dynamic formation of the weld pool whereby melting may be occurring at a given location while solidification has already commenced elsewhere throughout the weld pool. Considering both melting and possible simultaneous solidification in this manner ensures a more accurate simulation of temperature distribution. A source based enthalpy method is employed throughout the calculation domain in order to integrate the melting model with the UCD front tracking model for alloy solidification. Melting is tracked via interpolation of the liquidus isotherm, while solidification is treated via both the tracking of the advancing columnar dendritic front, and the nucleation and growth of equiaxed dendrites using a volume-averaging formulation. Heterogeneous nucleation is assumed to take place on TiN grain refiner particles at a grain refiner density of 1000 particles per mm2. A mechanical blocking criterion is used to define dendrite coherency, and the columnar-to-equiaxed transition within the weld pool is predicted.

  5. MPS solidification model. Analysis and calculation of macrosegregation in a casting ingot

    Poirier, D. R.; Maples, A. L.


    Work performed on several existing solidification models for which computer codes and documentation were developed is presented. The models describe the solidification of alloys in which there is a time varying zone of coexisting solid and liquid phases; i.e., the S/L zone. The primary purpose of the models is to calculate macrosegregation in a casting or ingot which results from flow of interdendritic liquid in this S/L zone during solidification. The flow, driven by solidification contractions and by gravity acting on density gradients in the interdendritic liquid, is modeled as flow through a porous medium. In Model 1, the steady state model, the heat flow characteristics are those of steady state solidification; i.e., the S/L zone is of constant width and it moves at a constant velocity relative to the mold. In Model 2, the unsteady state model, the width and rate of movement of the S/L zone are allowed to vary with time as it moves through the ingot. Each of these models exists in two versions. Models 1 and 2 are applicable to binary alloys; models 1M and 2M are applicable to multicomponent alloys.

  6. Solidification characterization of a new rapidly solidified Ni-Cr-Co based superalloy

    Wu, Kai, E-mail: [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Liu, Guoquan [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Hu, Benfu [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Li, Feng [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ (United Kingdom); Zhang, Yiwen [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); High Temperature Materials Research Institution, CISRI, Beijing 100081 (China); Tao, Yu; Liu, Jiantao [High Temperature Materials Research Institution, CISRI, Beijing 100081 (China)


    The solidification characterization of a new rapidly solidified Ni-Cr-Co based superalloy prepared by plasma rotating electrode process was investigated by means of optical microscope, scanning electron microscope, and transmission electron microscope. The results show that the solidification microstructure changes from dendrites to cellular and microcrystal structures with decreasing powder size. The elements of Co, Cr, W and Ni are enriched in the dendrites, while Mo, Nb and Ti are higher in the interdendritic regions. The relationships between powder size with the average solid-liquid interface moving rate, the average interface temperature gradient and the average cooling rate are established. Microsegregation is increased with larger powder size. The geometric integrity of MC Prime type carbides in the powders changes from regular to diverse with decreasing powder size. The morphology and quantity of carbides depend on the thermal parameters and non-equilibrium solute partition coefficients during rapid solidification. - Highlights: Black-Right-Pointing-Pointer The relations of solidification thermal parameters with powder size are established. Black-Right-Pointing-Pointer The relation of non-equilibrium solute partition with powder size is investigated. Black-Right-Pointing-Pointer The solidification microstructure is related to thermal parameters. Black-Right-Pointing-Pointer The segregation behavior is linked to non-equilibrium partition coefficients. Black-Right-Pointing-Pointer The morphology and quantity of carbides depend on the above combined factors.

  7. High Magnetic Field-Induced Formation of Banded Microstructures in Lamellar Eutectic Alloys During Directional Solidification

    Li, Xi; Fautrelle, Yves; Gagnoud, Annie; Ren, Zhongming; Moreau, Rene


    The influences of high magnetic field (up to 12 T) on the morphology of Pb-Sn and Al-Al2Cu lamellar eutectics during directional solidification were investigated. The experimental results indicate that, along with a decrease in eutectic spacing, the banded structure forms at lower growth speeds under high magnetic field and the band spacing decreases as the magnetic field increases. Moreover, the application of a magnetic field enriches the Cu solute in the liquid ahead of the liquid/solid interface during directional solidification of an Al-Al2Cu eutectic alloy. The effects of high magnetic field on the eutectic points of non-ferromagnetic alloys and the stress acting on the eutectic lamellae during directional solidification have been studied. Both thermodynamic evaluation and DTA measurements reveal that the high magnetic field has a negligible effect on the eutectic points of non-ferromagnetic alloys. However, the high magnetic field caused an increase of the nucleation temperature and undercooling. The numerical results indicate that a considerable stress is produced on the eutectic lamellae during directional solidification under high magnetic field. The formation of a banded structure in a lamellar eutectic during directional solidification under high magnetic field may be attributed to both the buildup of the solute in the liquid ahead of the liquid/solid interface and the stress acting on the eutectic lamellae.

  8. Influence of Processing Parameters on the Solidification Behavior of Single-Crystal CMSX-4 Superalloy

    Wang, Fu; Ma, Dexin; Bogner, Samuel; Bührig-Polaczek, Andreas


    The microstructural evolution of a superalloy, single-crystal CMSX-4 solidified at different withdrawal rates was investigated using a directional solidification quenching method. Analyses of the cross-sections within mushy zones generated the evolution of the solid volume fractions ( f s) during the reduction in the temperature and the solidification sequences. At the withdrawal rate of 0.3 mm min-1, f s increases by about 81 pct within the first 23 pct of the solidification interval, whereas it increases by about 64 pct at the withdrawal rate of 0.7 mm min-1. The Bower-Brody-Flemings model can characterize the evolution tendency of f s curve at the lower withdrawal rate, while it can not only describe the changing tendency of f s, but also precisely predict the f s values at higher withdrawal rate. With increasing withdrawal rate, the solidification intervals of the γ dendrite and γ/ γ' eutectics are increased. In addition to this, the forming site of the γ/ γ' eutectic at the lower withdrawal rate lags behind that at the higher withdrawal rate. At both the withdrawal rates the solidification of the γ/ γ' eutectic islands commences with the γ/ γ' core formed on the surface of the γ dendrites, then progressed spatially and developed the coarse γ/ γ' structure.

  9. Phase-field simulation of dendritic solidification using a full threaded tree with adaptive meshing

    Yin Yajun; Zhou Jianxin; Liao Dunming; Pang Shengyong; Shen Xu


    Simulation of the microstructure evolution during solidification is greatly beneficial to the control of solidification microstructures. A phase-field method based on the ful threaded tree (FTT) for the simulation of casting solidification microstructure was proposed in this paper, and the structure of the ful threaded tree and the mesh refinement method was discussed. During dendritic growth in solidification, the mesh for simulation is adaptively refined at the liquid-solid interface, and coarsened in other areas. The numerical results of a three-dimension dendrite growth indicate that the phase-field method based on FTT is suitable for microstructure simulation. Most importantly, the FTT method can increase the spatial and temporal resolutions beyond the limits imposed by the available hardware compared with the conventional uniform mesh. At the simulation time of 0.03 s in this study, the computer memory used for computation is no more than 10 MB with the FTT method, while it is about 50 MB with the uniform mesh method. In addition, the proposed FTT method is more efficient in computation time when compared with the uniform mesh method. It would take about 20 h for the uniform mesh method, while only 2 h for the FTT method for computation when the solidification time is 0.17 s in this study.

  10. Primary solidification phases of the Sn-rich Sn-Ag-Cu-Ni quaternary system

    Chang, Cheng-An; Chen, Sinn-Wen; Chiu, Chen-Nan; Huang, Yu-Chih


    The eutectic and near-eutectic Sn-Ag-Cu solders are the most promising lead-free solders, and nickel is frequently used as the barrier layer material. Nickel dissolves into the molten Sn-Ag-Ni alloy during the soldering process, and the ternary solder becomes a Sn-Ag-Cu-Ni quaternary melt near the nickel substrate. Liquidus projection is the projection of the liquidus trough and it delineates the boundaries of various primary solidification phases. Information of liquidus projection is helpful for understanding the alloys’ solidification behavior. This study prepared the Sn-Ag-Cu-Ni alloys of various compositions at the Sn-rich corner. The alloys were melted at higher temperatures and solidified in air. The solidified alloys were metallographically examined to determine the phases formed, especially the primary solidification phases. No ternary or quaternary compounds were found. The knowledge of the primary solidification phases, phase formation sequences, and reaction temperatures determined in this study were put together with all of the available liquidus projections of the constituent ternary systems to determine the primary solidification phases of the quaternary Sn-Ag-Cu-Ni system at the Sn-rich corner.

  11. Solidification Structure of Continuous Casting Large Round Billets under Mold Electromagnetic Stirring

    Tao SUN; Feng YUE; Hua-jie WU; Chun GUO; Ying LI; Zhong-cun MA


    The solidification structure of a continuous casting large round billet was analyzed by a cellular-automaton-finite-element coupling model using the ProCAST software.The actual and simulated solidification structures were compared under mold electromagnetic stirring (MEMS)conditions (current of 300 A and frequency of 3 Hz).There-after,the solidification structures of the large round billet were investigated under different superheats,casting speeds,and secondary cooling intensities.Finally,the effect of the MEMS current on the solidification structures was obtained under fixed superheat,casting speed,secondary cooling intensity,and MEMS frequency.The model accurately simulated the actual solidification structures of any steel,regardless of its size and the parameters used in the continuous casting process.The ratio of the central equiaxed grain zone was found to increase with decreasing su-perheat,increasing casting speed,decreasing secondary cooling intensity,and increasing MEMS current.The grain size obviously decreased with decreasing superheat and increasing MEMS current but was less sensitive to the casting speed and secondary cooling intensity.

  12. Cell partitioning during the directional solidification of trehalose solutions.

    Hubel, A; Darr, T B; Chang, A; Dantzig, J


    Previous studies have demonstrated that ice/cell interaction influences post thaw viability and specific cryoprotective agents can affect those interactions. Trehalose, a disaccharide, has been shown to have a protective benefit during conventional slow freezing. Existing theories have been put forth to explain the protective benefit of trehalose during desiccation and vitrification, but these theories do not explain the protective benefit observed during conventional freezing protocols. The overall objective of this investigation was to characterize cell/ice interactions in the presence of trehalose using non-planar freezing conditions. To that end, lymphoblasts suspended in phosphate buffered saline solution with various levels of trehalose (0, 10, 100, and 300 mM) were frozen on a directional solidification stage. The partitioning of cells into the interdendritic space or engulfment by an advancing dendrite was determined as a function of velocity and solution composition. For a given temperature gradient, the fraction of cells entrapped into the interdendritic region increased with increasing velocity. With small additions of trehalose (10 mM), the velocity at which cells were entrapped in the interdendritic region increased. At high trehalose concentrations (100, 300 mM), interface morphology was significantly different and cells were engulfed by the advancing interface. Dehydration of cells in the region shortly before and after the interface was significant and depended upon of the type of interaction experienced by the cell (entrapped vs. engulfed). These studies suggest that one potential mechanism for the action of trehalose involves changing the ice/cell interactions during conventional slow freezing.

  13. Stabilization/solidification of selenium-impacted soils using Portland cement and cement kiln dust

    Moon, Deok Hyun, E-mail: [W.M. Keck Geoenvironmental Laboratory, Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Department of Environmental Engineering, Chosun University, Gwangju 501-759 (Korea, Republic of); Grubb, Dennis G. [W.M. Keck Geoenvironmental Laboratory, Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Schnabel Engineering, LLC, 510 East Gay Street, West Chester, PA 19380 (United States); Reilly, Trevor L. [W.M. Keck Geoenvironmental Laboratory, Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030 (United States)


    Stabilization/solidification (S/S) processes were utilized to immobilize selenium (Se) as selenite (SeO{sub 3}{sup 2-}) and selenate (SeO{sub 4}{sup 2-}). Artificially contaminated soils were prepared by individually spiking kaolinite, montmorillonite and dredged material (DM; an organic silt) with 1000 mg/kg of each selenium compound. After mellowing for 7 days, the Se-impacted soils were each stabilized with 5, 10 and 15% Type I/II Portland cement (P) and cement kiln dust (C) and then were cured for 7 and 28 days. The toxicity characteristic leaching procedure (TCLP) was used to evaluate the effectiveness of the S/S treatments. At 28 days curing, P doses of 10 and 15% produced five out of six TCLP-Se(IV) concentrations below 10 mg/L, whereas only the 15% C in DM had a TCLP-Se(IV) concentration <10 mg/L. Several treatments satisfied the USEPA TCLP best demonstrated available technology (BDAT) limits (5.7 mg/L) for selenium at pozzolan doses up to 10 times less than the treatments that established the BDAT. Neither pozzolan was capable of reducing the TCLP-Se(VI) concentrations below 25 mg/L. Se-soil-cement slurries aged for 30 days enabled the identification of Se precipitates by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX). XRD and SEM-EDX analyses of the Se(IV)- and Se(VI)-soil-cement slurries revealed that the key selenium bearing phases for all three soil-cement slurries were calcium selenite hydrate (CaSeO{sub 3}.H{sub 2}O) and selenate substituted ettringite (Ca{sub 6}Al{sub 2}(SeO{sub 4}){sub 3}(OH){sub 12}.26H{sub 2}O), respectively.

  14. Fluidized-bed-combustion ash for the solidification and stabilization of a metal-hydroxide sludge.

    Knoll, K L; Behr-Andres, C


    Fluidized-bed-combustion (FBC) ash is a by-product from a developing technology for coal-fired power plants that will economically reduce air emissions to meet requirements of the Clean Air Act. FBC ash has physical and chemical properties similar to Portland cement, but only has moderate success as a pozzolan in concrete applications due to low compressive strengths. However, FBC ash has proven effective for use as a binder for the solidification and stabilization (S/S) of metal-bearing sludges. Physical and chemical characterization procedures were used to analyze FBC ash and a metal-bearing sludge obtained from a hazardous waste treatment facility to develop 12 different S/S mix designs. The mix designs consist of four binder designs to evaluate sludge-to-binder ratios of approximately 0, 0.5, and 1. Portland cement is used as a control binder to compare unconfined compressive strengths and Toxicity Characteristic Leaching Procedure (TCLP) analyses from different ratios of the FBC ash streams: fly ash, char, and spent bed material (SBM). Compressive strengths ranging from 84 lbs per square inch (psi) to 298 psi were obtained from various mix designs containing different sludge-to-ash ratios cured for 28 days. All the mix designs passed the TCLP. Recoveries from leaching for each metal were less than 5% for most mix designs. Results of unconfined compressive strengths, TCLP, and percent recovery calculations indicate that the mix design containing approximately a 1:1 ratio of fly ash to char-and-sludge is the best mix design for the S/S of the metal-bearing sludge.

  15. Utilization of fly ash for stabilization/solidification of heavy metal contaminated soils

    Dermatas, D.; Meng, X. [Stevens Inst. of Technology, Hoboken, NJ (United States)


    Pozzolanic-based stabilization/solidification (S/S) is an effective, yet economic technological alternative to immobilize heavy metals in contaminated soils and sludges. Fly ash waste materials were used along with quicklime (CaO) to immobilize lead, trivalent and hexavalent chromium present in contaminated clayey sand soils. The degree of heavy metal immobilization was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) as well as controlled extraction experiments. These leaching test results along with X-ray diffraction (XRD), scanning electron microscope and energy dispersive x-ray (SEM-EDX) analyses were also implemented to elucidate the mechanisms responsible for immobilization of the heavy metals under study. Finally, the reusability of the stabilized waste forms in construction applications was also investigated by performing unconfined compressive strength and swell tests. Results suggest that the controlling mechanism for both lead and hexavalent chromium immobilization is surface adsorption, whereas for trivalent chromium it is hydroxide precipitation. Addition of fly ash to the contaminated soils effectively reduced heavy metal leachability well below the non-hazardous regulatory limits. However, quicklime addition was necessary in order to attain satisfactory immobilization levels. Overall, fly ash addition increases the immobilization pH region for all heavy metals tested, and significantly improves the stress-strain properties of the treated solids, thus allowing their reuse as readily available construction materials. The only potential problem associated with this quicklime/fly ash treatment is the excessive formation of the pozzolanic product ettringite in the presence of sulfates. Ettringite, when brought in contact with water, may cause significant swelling and subsequent deterioration of the stabilized matrix. Addition of minimum amounts of barium hydroxide was shown to effectively eliminate ettringite formation.

  16. On the role of solidification modelling in Integrated Computational Materials Engineering “ICME”

    Schmitz, G. J.; Böttger, B.; Apel, M.


    Solidification during casting processes marks the starting point of the history of almost any component or product. Integrated Computational Materials Engineering (ICME) [1-4] recognizes the importance of further tracking the history of microstructure evolution along the subsequent process chain. Solidification during joining processes in general happens quite late during production, where the parts to be joined already have experienced a number of processing steps which affected their microstructure. Reliable modelling of melting and dissolution of these microstructures represents a key issue before eventually modelling ‘re’-solidification e.g. during welding or soldering. Some instructive examples of microstructure evolution during a joining process obtained on the basis of synthetic and simulated initial microstructures of an Al-Cu binary model system are discussed.

  17. In Situ Observation of Solidification Process of AISI 304 Austenitic Stainless Steel

    HUANG Fu-xiang; WANG Xin-hua; ZHANG Jiong-ming; JI Chen-xi; FANG Yuan; YU Yan


    The solidification process of AISI 304 stainless steel during cooling at a rate of 0.05 K/s has been observed in situ using a confocal scanning laser microscope(CSLM).The results show that the δ phase appeared first in liquid steel,as the temperature decreased,the γ phase precipitated prior at δ-grain boundary at 1452.2℃,the liquid steel disappeared at 1431.3℃,and then theγphase precipitated on the δ ferrite.Based on the Scheil-GulliVer solidification model,the solidification processes of AISI 304 stainless steel are simulated using the Scheil model in Thermo-Calc.and the simulation results agree well with the results observed in the experiment.

  18. Mathematical Model of Fluid Flow and Solidification in Mold Region of Continuous Slab Casting

    谭利坚; 沈厚发; 柳百成


    To simulate the phenomena in the mold region of continuous casting by coupling fluid flow and solidification, a three-dimensional mathematical model has been developedbased on the K-ε turbulence equations and the SIMPLER algorithm. A pseudo source term was introduced into the energy equation to account for the latent heat and kinetic energy. The fluid flow in the mushy zone was calculated by defining the fluid viscosity as a function of the solid fraction in the mushy zone. Fine meshes in the solid region improve convergence and reduce iteration time. Comparison of the fluid flow and temperature distribution with and without solidification shows that although the solid shell in the mold is thin, it still greatly affects the flow pattern. The numerical results obtained provide details of the fluid flow and solidification phenomena which can be used to optimize the nozzle structure and other process parameters in continuous casting.

  19. Derivation and application of time step model in solidification process simulation


    The heat transfer during the casting solidification process includes the heat radiation of the high temperature casting and the mold, the heat convection between the casting and the mold, and the heat conduction inside the casting and from the casting to the mold. In this paper, a formula of time step in simulation of solidification is derived, considering the heat radiation, convection and conduction based on the conservation of energy. The different heat transfer conditions between the conventional sand casting and the permanent mold casting are taken into account in this formula. The characteristics of heat transfer in the interior and surface of the casting are also considered. The numerical experiments show that this formula can avoid computational dispersion, and improve the computational efficiency by about 20% in the simulation of solidification process.

  20. Derivation and application of time step model in solidification process simulation

    GONG Wen-bang


    Full Text Available The heat transfer during the casting solidification process includes the heat radiation of the high temperature casting and the mold, the heat convection between the casting and the mold, and the heat conduction inside the casting and from the casting to the mold. In this paper, a formula of time step in simulation of solidification is derived, considering the heat radiation, convection and conduction based on the conservation of energy. The different heat transfer conditions between the conventional sand casting and the permanent mold casting are taken into account in this formula. The characteristics of heat transfer in the interior and surface of the casting are also considered. The numerical experiments show that this formula can avoid computational dispersion, and improve the computational efficiency by about 20% in the simulation of solidification process.

  1. Filling and solidification of TiAl melt in centrifugal field

    SHENG Wen-bin


    A model was established based on the combination of the equation of continuity,the equation of conservation of momentum and the equation of general energy to describe the filling and solidification of TiAl melt by permanent mold centrifugal casting. The model was solved numerically and the filling and solidification processes in the centrifugal field were discussed. The results indicate that the centrifugal field essentially influences the filling and solidification processes of TiAl melt. The melt will first fill the cavity along the back boundary until it reaches the end. After the end is fully filled,the whole cavity will be filled gradually by the way that free surface of the melt moves towards the entrance,hence the entrance is the last part to be filled. Furthermore,the mechanism by which internal defects can be formed in centrifugally cast TiAl components were interpreted.

  2. Experimental study on directional solidification of Al-Si alloys under the influence of electric currents

    Räbiger, D.; Zhang, Y.; Galindo, V.; Franke, S.; Willers, B.; Eckert, S.


    The application of electric currents during solidification can cause grain refinement in metallic alloys. However, the knowledge about the mechanisms underlying the decrease in grain size remains fragmentary. This study considers the solidification of Al-Si alloys under the influence of electric currents for the configuration of two parallel electrodes at the free surface. Solidification experiments were performed under the influence of both direct currents (DC) and rectangular electric current pulses (ECP). The interaction between the applied current and its own induced magnetic field causes a Lorentz force which produces an electro-vortex flow. Numerical simulations were conducted to calculate the Lorentz force, the Joule heating and the induced melt flow. The numerical predictions were confirmed by isothermal flow measurements in eutectic GaInSn. The results demonstrate that the grain refining effect observed in our experiments can be ascribed solely to the forced melt flow driven by the Lorentz force.

  3. Solidification Structure Refining of 430 Ferrite Stainless Steel With TiN Nucleation

    SHI Cai-xia; CHENG Guo-guang; LI Zhan-jun; ZHAO Pei


    The thermodynamics of TiN precipitation in liquid steel of 430 ferrite stainless steel has been calculated to find out the condition of TiN precipitation during the initial solidification stage. The difference in the solidification structure of 430 ferrite stainless steel has been discussed through comparative tests of vacuum induction furnace melt-ing with different contents of Ti. It has been found that the equiaxed grain proportion can be increased from 20% to 69% as the content of Ti from 0.1% up to 0.4%. The size of the TiN particles precipitated is 1--3 μm and the number of TiN particles is about (200--300)/μm2. It is found that the effect of using TiN to refine the solidification structure has been confirmed under the strict process condition used for 430 ferrite stainless steel.

  4. Solidification of a colloidal hard sphere like model system approaching and crossing the glass transition.

    Franke, Markus; Golde, Sebastian; Schöpe, Hans Joachim


    We investigated the process of vitrification and crystallization in a model system of colloidal hard spheres. The kinetics of the solidification process was measured using time resolved static light scattering, while the time evolution of the dynamic properties was determined using time resolved dynamic light scattering. By performing further analysis we confirm that solidification of hard sphere colloids is mediated by precursors. Analyzing the dynamic properties we can show that the long time dynamics and thus the shear rigidity of the metastable melt is highly correlated with the number density of solid clusters (precursors) nucleated. In crystallization these objects convert into highly ordered crystals whereas in the case of vitrification this conversion is blocked and the system is (temporarily) locked in the metastable precursor state. From the early stages of solidification one cannot clearly conclude whether the melt will crystallize or vitrify. Furthermore our data suggests that colloidal hard sphere glasses can crystallize via homogeneous nucleation.

  5. Effect of Rectangle Wave Pulse Current on Solidification Structure of ZA27 Alloy


    The effect of rectangle wave pulse current on solidification structure of ZA27 alloy was studied.The results show that the wave pattern relies on the frequency range of harmonic wave and the energy of pulse current within the frequency range of pulse current.Imposed pulse current could induce the solidification system to oscillate.The frequency range and the relevant energy distribution of pulse current exert an influence on the amount of atoms involved for forming critical nucleus, the surface states of clusters in melt, the oscillating state of melt on the surface of clusters, the active energy of atom diffusion , the frequnce response of the resonance of bulk melt and the absorbability of the solidification system to the external work.Rectangle wave pulse current involves rich harmonic waves; the amplitudes of high order of harmonic waves are higher and reduce slowly, so it has a better effect on inoculation and modification.

  6. Effects of Space Environment on Flow and Concentration During Directional Solidification

    Benjapiyaporn, C.; Timchenko, V.; Leonardi, E.; deVahlDavis, G.; deGroh, H. C., III


    A study of directional solidification of a weak binary alloy (specifically, Bi - 1 at% Sn) based on the fixed grid single domain approach is being undertaken. The enthalpy method is used to solve for the temperature field over the computational domain including both the solid and liquid phases; latent heat evolution is treated with the aid of an effective specific heat coefficient. A source term accounting for the release of solute into the liquid during solidification has been incorporated into the solute transport equation. The vorticity-stream function formulation is used to describe thermosolutal convection in the liquid region. In this paper we numerically investigate the effects of g-jitter on directional solidification. A background gravity of 1 micro-g has been assumed, and new results for the effects of periodic disturbances over a range of amplitudes and frequencies on solute field and segregation have been presented.

  7. A 3-phase model for mixed columnar-equiaxed solidification in DC casting of bronze

    Hao, J.; Grasser, M.; Wu, M.; Ludwig, A.; Riedle, J.; Eberle, R.


    A three-phase Eulerian approach is used to model the columnar-to-equiaxed transition (CET) during solidification in DC casting of technical bronze. The three phases are the melt, the solidifying columnar dendrites and the equiaxed grains. They are considered as spatially interpenetrating and interacting continua by solving the conservation equations of mass, momentum, species and enthalpy for all three phases. The so defined solidification model is applied to a binary CuSn6 DC casting process as a benchmark to demonstrate the model potentials. Two cases are studied: one considering only feeding flow and one including both feeding flow and equiaxed sedimentation. The simulated results of mixed columnar and equiaxed solidification are presented and discussed including the occurrence of CET, phase distribution, feeding flow, equiaxed sedimentation and their influence on macrosegregation.

  8. Analysis on the non-equilibrium dendritic solidification of a binary alloy with back diffusion

    Chung, J.D. [Seoul National University Graduate School, Seoul (Korea, Republic of); Yoo, H.S. [Soong Sil University, Seoul (Korea, Republic of); Lee, J.S. [Seoul National University, Seoul (Korea, Republic of)


    Micro-Macro approach is conducted for the mixture solidification to handle the closely linked phenomena of microscopic solute redistribution and macroscopic solidification behavior. For this purpose, present work combines the efficiency of mixture theory for macro part and the capability of microscopic analysis of two-phase model for micro part. The micro part of present study is verified by comparison with experiment of Al-4.9 mass% Cu alloy. The effect of back diffusion on the macroscopic variables such as temperature and liquid concentration, is appreciable. The effect, however, is considerable on the mixture concentration and eutectic fraction which are indices of macro and micro segregation, respectively. According to the diffusion time, the behavior near the cooling wall where relatively rapid solidification permits short solutal diffusion time, approaches Scheil equation limit and inner part approaches lever rule limit. (author). 23 refs., 13 figs., 1 tab.

  9. Formation of a two-phase microstructure in Fe-Cr-Ni alloy during directional solidification

    Fu, J. W.; Yang, Y. S.; Guo, J. J.; Ma, J. C.; Tong, W. H.


    The formation and evolution of a two-phase coupled growth microstructure in AISI 304 stainless steel are investigated using a quenching method during directional solidification. It is found that the two-phase microstructure, which is composed of coupled growth of thin lathy delta ferrite (δ) and austenite (γ), forms from the melt first during solidification. As solidification proceeds, the retained liquid transforms into austenite directly. On cooling, the subsequent incomplete solid-state transformation from ferrite to austenite results in the disappearance of the thinner lathy delta ferrite, and the final two-phase coupled growth microstructure is formed. The formation mechanism of the two-phase coupled growth microstructure is analyzed theoretically based on the nucleation and constitutional undercooling (NCU) criterion. Transmission electron microscope (TEM) and EDS analyses were carried out to identify the phases and determine the phase composition, respectively.

  10. Characteristics of S/L Interface Evolution during High Rate Directional Solidification


    The present paper aims to the characterization of high rate direction solidification on Al-Mn and Al-Cu alloys. It is indicated that the relevant cooling rate of high rate directional solidification is defined within 100~103 K/s that is located in the region between near-equilibrium slow growth rate and rapid solidification rate beyond equilibrium condition, and at the meantime there occurred a series of turning effect of interface stability and morphologies.With the increase of growth velocity the interface with planar front evolved to cells and dendrites at the stage of near-equilibrium and with further increase of growth rate they transformed reversely from dendrites to cell structure and then to absolute stability of planar interface. An explanation based on effective constitutional supercooling about the evolution of interface morphologies with the change of growth rate was proposed.

  11. Simulation on solidification of an Al-Ni alloy under electromagnetic stirring

    Sha Minghong


    Full Text Available The microstructure of Al-Ni alloy has a significant influence on its performance, while electromagnetic stirring is one of the most effective methods for control of solidification structure of Al alloy. To investigate the effect of electromagnetic stirring on the solidification of the ingot, the solidification of the Al-50Ni alloy in vacuum with electromagnetic stirring was described by numerical simulation in this paper; and a three dimensional mathematical model was established. The electromagnetic field was simulated by ANSYS software and the thermal-flow field was simulated by FLUENT software. The coupling between the electromagnetic field and the thermal-flow field was implemented by user-defined subroutines. It is found that the current intensity has significant influences on the fluid flow and the microstructure of the alloy. The simulation results agree well with the experimental results, and the optimum current intensity under the exprimental conditions is 80 A, while the frequency is 50 Hz.

  12. The Crystallization of Poly (3-dodecylthiophene) in an Oriented Solidification Environment


    The crystallization behaviors of poly (3-dodecylthiophene) (P3DDT) under two different oriented solidification conditions, I.e., two different relative relations (90° and 180°) between the directions of gravity and solidification, were investigated. X-ray diffraction results reveal that although similar layered structures are formed, under the condition of the relative relation 180°, temperature gradient has greater effects on the perfect degree of the layered structures of P3DDT. It also can be concluded that after recrystallization, the layered structures of P3DDT can be improved at relative relation 90o, but the orderly degree of the arrangements of alkyl side chains are not improved yet, even is reduced for both of the oriented solidification conditions.

  13. Solidification and remelting of Al through Al2O3 fibrous preform under centrifugal force

    HU Guo-xin; LIU Jian-ju; ZHANG Li-xiang; TIAN Qin-wei


    The solidification and remelting of molten aluminum through a porous preform under centrifugal force field were modeled numerically. The results show that the transient solidification and remelting phenomena appear on the infiltration front and can be divided into two distinct regions: the remelting region and solid-liquid congruent melting region. The decrease of porosity always results in the increase of moving velocity difference between the infiltration front and the remelting front, which leads to the increase of the solid-liquid congruent region extent. But for the decrease of the rotational frequency, the difference of moving velocity between infiltration front and remelting front decreases, which leads to the decrease of regional extent. The infiltration front moving velocity is mainly influenced by the centrifugal infiltration pressure, whereas the remelting front moving velocity is mainly influenced by the material thermodynamics. The transient solidification and remelting phenomena are the intercoupling results between the centrifugal infiltration dynamics and the material thermodynamics.

  14. A solidification constitutive model for NIKE2D and NIKE3D

    Raboin, P.J.


    This memo updates the current status of a solidification material model development which has been underway for more than a year. Significant modeling goals such as predicting cut-off stresses, thermo-elasto-plasticity, strain rate dependent plasticity and dynamic recovery have been completed. The model is called SOLMAT for solidification material model, and while developed for NIKE2D, it has already been implemented in NIKE3D and NIT03D by B. Maker. This memo details the future development strategy of SOLMAT including liquid and solid constitutive improvements, coupling of deviatoric and dilatational deformation and a plan to switch between constitutive theories. It explains some of the difficulties associated solidification modeling and proposes two experiments to measure properties for using SOLMAT. Due to the sensitive nature of these plans in relation to programmatic and CRADA concerns, this memo should be treated as confidential document.

  15. Solidification Features of Ti45Al Alloys with Different Boron Addition

    Weidong Wang; Yingche Ma; Bo Chen; Ming Gao; Kui Liu; Yiyi Li


    The effects of boron on the solidification behaviors of Ti45AlxB alloys were studied by high temperature samples. These samples were melted at 1823 K, followed by cooling to the designated temperature, and then quickly water-quenched to preserve the solidification features. Optical microscopy and scanning electron microscopy analysis shows that the solidus temperature of Ti45AI was really reduced by 20 K when adding 0.8 at. pct B, and it was also observed that boride precipitated before the appearance of β phase. Besides, solidification structure confirmed that B addition does not obviously refine β phase, α grain refinement by certain amount of B in alloy probably clarifies the mechanism of B refining lamellar microstructure at room temperature.

  16. Analysis of melting and solidification behaviour of glass-forming alloys by synchrotron radiation

    Baser, T.A.; Baricco, M. [Dipartimento di Chimica, Universita di Torino (Italy); NIS, Torino (Italy); Bostrom, M. [The European Synchrotron Radiation Facility, (ESRF), Grenoble (France); Stoica, M. [Leibniz-Institut fuer Festkorper- und Werkstoffforschung Dresden (Germany); Yavari, A.R. [Laboratorie de Thermodynamique et Physico-chimie Metallurgique (LTPCM-UMR 5614), Institut National Polytechnique de Grenoble, CNRS (France)


    This paper aims to study the melting and solidification behaviour of Fe48Cr15Mo14Y2C15B6 and Cu50Zr50 glass-forming alloys by in-situ synchrotron X-ray diffraction from data obtained at the European Synchrotron Radiation Facility (ESRF). Melting and solidification behaviour for both alloys were measured by high temperature differential scanning calorimetry (HTDSC). The phase identification was performed by Rietveld refinement of diffraction patterns collected as a function of temperature. The phase mixture on melting and solidification has been clarified, confirming that in-situ X-ray diffraction by synchrotron radiation is a powerful technique for the study of phase transformations in alloys. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  17. Quantitative characterization of mns inclusions in S355 steel regarding to solidification rate

    Mahmutović Aida


    Full Text Available A practice of special interest for metallurgical steelmaking is the relationship between redistribution of solute elements and dendrite microsegregation that occurs during solidification. These phenomena have a significant impact on the final properties of cast and forged products. In this paper, a calculation of the characteristic chemical phases in S355 steel using a software program Thermo-Calc is presented. Also, the paper presents experimental measurements of the dendrites size and non-metallic inclusions using optical and electron probe microanalyzer, as well as the calculation of the local solidification rate on the particular example. These phenomena are of special interest when it comes to thin castings and higher cooling rates. Thin castings require higher quality of casting surface, corresponding distribution, and character than those of non-metallic inclusions. Thermo-calc software was used for calculation of equilibrium phases, temperature ranges of solidification of tested material, and temperature range for developing characteristic equilibrium phase. It was found that during solidification and cooling processes manganese sulphide inclusions were formed. Additionally, accurate values for solidus and liquidus temperatures, which coincide with the values of solidus and liquidus temperatures obtained by the Thermo Calc, were calculated. Using optical and electron probe microanalyzer, the type of inclusions were confirmed, whereas chemical composition and size measurement of dendrites, and formed non-metallic inclusions were determined. Mapping and Linescan methods were used to examine the size and exact chemical composition of sulphides in atomic percents. Using secondary dendrites local solidification rate was calculated (for casting surface area solidification rate was 5 K/s. This paper gives contribution to better understanding the influence of cooling rate on casting microstructure formation and dendrites, which essentially

  18. Nanoparticle Capture During Directional Solidification of Nano-Sized SiC Particle-Reinforced AZ91D Composites.

    Zhu, Qiaobo; Liu, Hongchang; Li, Wenzhen; Gao, Weiming; Li, Qiushu


    The capture/push behavior of a particle in front of a solidification interface was analyzed theoretically and experimentally in this work. Van der Waals force, viscous force, and force due to interfacial energy played important roles in the particle capture/push process. Directional solidification experiments were conducted with nano-sized SiC particle-reinforced AZ91D composites to observe the distribution of nanoparticles in different solidification morphologies under varied cooling rates. When the composite solidified with plane manner, the nanoparticles could be captured by the solidification front and distributed uniformly in the matrix. When solidified with columnar or equiaxial manners, the nanoparticles could be captured by the solidification front but distributed uniformly only in the grain boundary as a result of the difference in interfacial energy and wettability between SiC/α-Mg and SiC/eutectic phase. Theoretical prediction of particle capture was in agreement with the experiment results.

  19. Particle incorporation in metallic melts during dendritic solidification-undercooling experiments under reduced gravity

    Lierfeld, T. [Institute of Space Simulation, German Aerospace Center (DLR), D-51170 Cologne (Germany); Institute of Materials, Ruhr-University Bochum, D-44780 Bochum (Germany)], E-Mail:; Gandham, P. [Institute of Space Simulation, German Aerospace Center (DLR), D-51170 Cologne (Germany); Department of Metallurgical and Materials Engineering, IITM, Chennai (India); Kolbe, M. [Institute of Space Simulation, German Aerospace Center (DLR), D-51170 Cologne (Germany); Schenk, T. [Experiments Division (ID19), ESRF, F-38043 Grenoble (France); Laboratoire de Physique des Materiaux, EdM de Nancy, F-54042 Nancy (France); Singer, H.M. [Laboratory for Solid State Physics, Swiss Federal Institute of Technology ETH, CH-8093 Zurich (Switzerland); Eggeler, G. [Institute of Materials, Ruhr-University Bochum, D-44780 Bochum (Germany); Herlach, D.M. [Institute of Space Simulation, German Aerospace Center (DLR), D-51170 Cologne (Germany)


    The interaction of ceramic particles with a dendritic solid/liquid-interface has been investigated by undercooling experiments with different levels of convection: (i) in a terrestrial electromagnetic levitation facility and (ii) in TEMPUS, a facility for containerless processing, under low gravity conditions during parabolic flights. Entrapment of particles in ground experiments and engulfment of a significant fraction of submicron particles under low gravity conditions are attributed to the lower level of convection in the latter experiments and to morphological features of dendritic solidification. X-ray radiography has been used for in situ observations of directional solidification in Al{sub 90}Cu{sub 10} with alumina particles.

  20. Rapid directional solidification in Sn-Cu lead-free solder

    Jun Shen; Yongchang Liu; Houxiu Gao


    An experimental study on the microstructures of a rapid directionally solidified metallo-eutectic Sn-Cu alloy was carried out.This material is an important alloy that is used as a lead-free solder. The results showed that the kinetic undercooling due to the rapid solidification process led to the formation of a pseudoeutectic zone, whereas the hypereutectic reaction produced the regular lamellar structure in the hypereutectic Sn-1.0Cu alloy. The corresponding arm spacing in the obtained lamellar phases decreased gradually with the increase of the applied cooling rate, which corresponded well with the prediction of a rapid directional solidification model.

  1. A Study on Solidification and Melting of Water around Spine-fin Tube

    Hirasawa, Yoshio; Takegoshi, Eisyun; Konya, Hiroshi; Tajima, Ikuo

    The authors have studied the phase change process of composite materials containing conductive solids in order to improve the heat transfer characteristics of phase change materials. In this study, experiments for the solidification and melting of water around a spine-fin tube are carried out, and the phase change volume and temperature distribution in the water are measured. As a result, the solidification and melting process are promoted considerably by the heat conduction of the fin and the natural convection in the lower side of the spine-fin tube for the melting process.

  2. Development of thermal simulation system for heavy section ductile iron solidification


    A new reliable thermal simulation system for studying solidification of heavy section ductile iron has been developed using computer feedback control and artificial intelligent methods. Results of idle test indicate that the temperature in the system responses exactly to the inputted control data and the temperature control error is less than ± 0.5 %. It is convenient to simulate solidification of heavy section ductile iron using this new system. Results of thermal simulation experiments show that the differences in nodularity and number of graphite nodule per unit area in the thermal simulation specimen and the actual heavy section block is less than 5 % and 10 %, respectively.

  3. Numerical simulation on rapid melting and nonequilibrium solidification of pure metals and binary alloys

    惠希东; 陈国良; 杨院生; 胡壮麒


    A heat and mass transfer modelling containing phase transformation dynamics is made for pure metals and binary alloys under pulsed laser processing. The nonequilibrium effects of processing parameters and physical properties are evaluated on the melting and solidification of pure metals (Al, Cu, Fe and Ni) and Al-Cu alloys. It is shown that the energy intensity of laser beam and physical properties of metals and the solute concentration of alloys have important effect on the interface temperature, melting and solidification velocity, melting depth and non-equilibrium partition coefficient. This situation is resulted from the interaction of heat transfer, redistribution of solute, solute trapping and growth kinetics.

  4. A Combined Numerical-Experimental Approach to Quantify the Thermal Contraction of A356 During Solidification

    Macht, J. P.; Maijer, D. M.; Phillion, A. B.


    A process for generating thermal contraction coefficients for use in the solidification modeling of aluminum castings is presented. Sequentially coupled thermal-stress modeling is used in conjunction with experimentation to empirically generate the thermal contraction coefficients for a strontium-modified A356 alloy. The impact of cooling curve analysis on the modeling procedure is studied. Model results are in good agreement with experimental findings, indicating a sound methodology for quantifying the thermal contraction. The technique can be applied to other commercially relevant aluminum alloys, increasing the utility of solidification modeling in the casting industry.

  5. The effects of solidification and atomization on rare-earth alloys

    Anderson, Iver E.; Osborne, M. G.; Ellis, T. W.


    This article discusses the results of experiments involving the application of atomization techniques to the production of three selected rare-earth intermetallic (REI) materials. High-pressure gas atomization and centrifugal atomization into a rotating quench bath have been used to process the alloys. Rapid-solidification processing by atomization techniques is of great benefit since optimum performance of these REI materials demands chemical and structural homogeneity. The results demonstrate that such careful solidification microstructure control is required if the benefits of REI-alloy properties are to be realized with maximum processing efficiency.

  6. Simulation of the aluminum alloy A356 solidification cast in cylindrical permanent molds


    A mathematical model based on the control volume method with fixed mesh was selected in order to simulate the solidification of cylindrical castings poured in permanent steel mold. The latent heat was incorporated using the effective specific heat. The application of the model allowed us to obtain the solidification front and the temperature fields at any time from the pouring. The mold was made of the SAE 1010 steel. Two mold temperatures were evaluated: 25°C and 300°C. The mathematical mode...

  7. Phase transformation and liquid density redistribution during solidification of Ni-based superalloy Inconel 718

    Wang Ling


    Full Text Available The influences of chemical segregation and phase transformation on liquid density variation during solidification of Ni-based supperalloy Inconel 718 were investigated using SEM and EDS. It was found that significant segregation in liquid prompts high Nb phase to precipitate directly from liquid, which results in the redistribution of alloy elements and liquid density in their vicinity. The term “inter-precipitate liquid density” is therefore proposed and this concept should be applied to determine the solidification behavior of superalloy Inconel 718.

  8. Improved solidification influence modelling for Eulerian fuel-coolant interaction codes

    Ursic, Mitja, E-mail: mitja.ursic@ijs.s [Jozef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); Leskovar, Matjaz; Mavko, Borut [Jozef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia)


    Steam explosion experiments revealed important differences in the efficiency between simulant alumina and oxidic corium melts. The experimentally observed differences are importantly attributed to the differences in the melt droplets solidification and void production, which are limiting phenomena in the steam explosion process and have to be adequately modelled in fuel-coolant interaction codes. This article focuses on the modelling of the solidification effect. An improved solidification influence modelling approach for Eulerian fuel-coolant interaction codes was developed and is presented herein. The solidification influence modelling in fuel-coolant interaction codes is strongly related to the modelling of the temperature profile and the mechanical effect of the crust on the fragmentation process. Therefore the first objective was to introduce an improved temperature profile modelling and a fragmentation criterion for partly solidified droplets. The fragmentation criterion was based on the established modified Weber number, which considers the crust stiffness as a stabilizing force acting to retain the crust under presence of the hydrodynamic forces. The modified Weber number was validated on experimental data. The application of the developed improved solidification influence modelling enables an improved determination of the melt droplet mass, which can be efficiently involved in the fine fragmentation during the steam explosion process. Additionally, also the void production modelling is improved, because it is strongly related to the temperature profile modelling in the frame of the solidification influence modelling. Therefore the second objective was to enable an improved solidification influence modelling in codes with an Eulerian formulation of the droplet field. Two additional transported model parameters based on the most important droplets features regarding the fuel-coolant interaction behaviour, were derived. First, the crust stiffness was

  9. Microprestress-Solidification Theory for Concrete Creep. II: Algorithm and Verification

    Bazant, Z. P.; Hauggaard-Nielsen, Anders Boe; Bajewa, S.


    The companion paper in this issue (Bazant et al. 1997) presents a generalization of the solidification theory. Compared to the previous solidification theory, the generalization is better justified by the understanding of the physical processes involved in the effects of aging and drying...... on the creep of concrete. It remains to formulate a numerical algorithm for practical application of this new theory in finite-element programs and to compare the new theory to the main available experimental data. This is the purpose of this paper. All the definitions and notations introduced in the preceding...

  10. (AADSF) Advanced Automated Directional Solidification Furnace Onboard STS-87 USMP-4


    The purpose of the experiments for the Advanced Automated Directional Solidification Furnace (AADSF) is to determine how gravity-driven convection affects the composition and properties of alloys (mixtures of two or more materials, usually metal). During the USMP-4 mission, the AADSF will solidify crystals of lead tin telluride and mercury cadmium telluride, alloys of compound semiconductor materials used to make infrared detectors and lasers, as experiment samples. Although these materials are used for the same type application their properties and compositional uniformity are affected differently during the solidification process.

  11. Domain of oscillatory growth in directional solidification of dilute binary alloys.

    Babushkina, Evgenia; Bessonov, Nicholas M; Korzhenevskii, Alexander L; Bausch, Richard; Schmitz, Rudi


    The oscillatory growth of a dilute binary alloy has recently been described by a nonlinear oscillator equation that applies to small temperature gradients and large growth velocities in the setup of directional solidification. Based on a one-dimensional stability analysis of stationary solutions of this equation, we explore in the present paper the complete region where the solidification front propagates in an oscillatory way. The boundary of this region is calculated exactly, and the nature of the oscillations is evaluated numerically in several segments of the region.

  12. A finite element modeling on the fluid flow and solidification in a continuous casting process

    Kim, T.H.; Kim, D.S. [Hanyang University Graduate School, Seoul (Korea); Choi, H.C. [Agency for Defence Development, Taejon (Korea); Kim, S.W. [Hanyang University, Seoul (Korea); Lee, S.K. [Chung Buk National University, Chungju (Korea)


    The coupled turbulent flow and solidification is considered in a typical slab continuous casting process using commercial program FIDAP. Standard {kappa}-{epsilon} turbulence model is modified to decay turbulent viscosity in the mushy zone and laminar viscosity is set to a sufficiently large value at the solid region. This coupled turbulent flow and solidification model also contains thermal contact resistance due to the mold powder and air gap between the strand and mold using an effective thermal conductivity. From the computed flow pattern, the trajectory of inclusion particles was calculated. The comparison between the predicted and experimental solidified shell thickness shows a good agreement. (author). 27 refs., 11 figs., 2 tabs.

  13. Modelling the solidification of ductile cast iron parts with varying wall thicknesses

    Bjerre, Mathias Karsten; Tiedje, Niels Skat; Thorborg, Jesper


    ] with a 2D FE solution of the heat conduction equation is developed in an in-house code and model parameters are calibrated using experimental data from representative castings made of ductile cast iron. The main focus is on the influence of casting thickness and resulting local cooling conditions......In the present paper modelling the solidification of cast iron parts is considered. Common for previous efforts in this field is that they have mainly considered thin walled to medium thickness castings. Hence, a numerical model combining the solidification model presented by Lesoultet al. [1...

  14. Modeling of the Formation of AlN Precipitates During Solidification of Steel

    Kalisz D.


    Full Text Available The study was carried out computer simulations of the formation process of AlN precipitates in the solidification of steel. The chemical composition of steel and non-metallic inclusions formed was determined using the commercial software FactSage. Calculated amount of precipitates formed during cooling of steel between the liquidus and solidus temperatures under conditions of thermodynamic equilibrium. In parallel, the computations were performed using your own computer program. It was found that aluminum nitride is formed at the final stage of solidification, and the condition of its formation is low oxygen content in steel.

  15. Modeling of the Formation of AlN Precipitates During Solidification of Steel

    D. Kalisz


    Full Text Available The study was carried out computer simulations of the formation process of AlN precipitates in the solidification of steel. The chemical composition of steel and non-metallic inclusions formed was determined using the commercial software FactSage. Calculated amount of precipitates formed during cooling of steel between the liquidus and solidus temperatures under conditions of thermodynamic equilibrium. In parallel, the computations were performed using your own computer program. It was found that aluminum nitride is formed at the final stage of solidification, and the condition of its formation is low oxygen content in steel.

  16. Critical assessment of methods for treating airborne effluents from high-level waste solidification processes

    Christian, J.D.; Pence, D.T.


    Off-gas treatment systems are reviewed for high-temperature processes which are being developed for the solidification of high-level liquid wastes from nuclear fuel reprocessing plants. A brief description of each of the processes is given and detailed analyses are made of the expected magnitudes of airborne effluent release rates from each system. The estimated release rates of the various processes are compared with present and anticipated regulatory limits. A number of recommendations are made for additional development studies to better understand and control certain airborne effluents from the solidification processes.

  17. Phase field modeling of multiple dendrite growth of AI-Si binary alloy under isothermal solidification

    Sun Qiang; Zhang Yutuo; Cui Haixia; Wang Chengzhi


    Phase field method offers the prospect of being able to perform realistic numerical experiments on dendrite growth in metallic systems. In this study, the growth process of multiple dendrites in Ai-2-mole-%-Si binary alloy under isothermal solidification was simulated using phase field model. The simulation results showed the impingement of arbitrarily oriented crystals and the competitive growth among the grains during solidification. With the increase of growing time, the grains begin to coalesce and impinge the adjacent grains. When the dendrites start to impinge, the dendrite growth is obviously inhibited.

  18. Phase-field model of isothermal solidification with multiple grain growth

    Feng Li; Wang Zhi-Ping; Zhu Chang-Sheng; Lu Yang


    This paper develops a new phase-field model for equiaxed dendrite growth of multiple grains in multicomponent alloys based on the Ginzberg-Landau theory and phase-field model of a single grain. Taking Al-Cu and Al-Cu-Mg alloys for example, it couples the concentration field and simulates the dendrite growth process of multiple grains during isothermal solidification. The result of the simulation shows dendrite competitive growth of multiple grains, and is reapplied to the process of dendrite growth in practical solidification.

  19. Directional solidification of metal-gas eutectic and fabrication of regular porous metals


    Directional solidification of metal-gas eutectic (Gasar) is a novel process for making regular porous metals.This process is based on a solid-gas eutectic reaction involving a gaseous medium and a metal or a ceramic phase, and allows an easy control of the porosity, such as its pore size, pore orientation and morphology in a wide range by properly adjusting its melting and solidification conditions. The latest progress and our research work in this field are reviewed in this paper.

  20. Laser ablation ICP-MS investigation of solute element distributions during Al-Si solidification

    Nafisi, Shahrooz [Center for University Research on Aluminum (CURAL), University of Quebec at Chicoutimi, Chicoutimi, QC, G7H 2B1 (Canada); Cox, Richard [Department of Earth Sciences, University of Quebec at Chicoutimi, Chicoutimi, QC, G7H 2B1 (Canada); Ghomashchi, Reza [Center for University Research on Aluminum (CURAL), University of Quebec at Chicoutimi, Chicoutimi, QC, G7H 2B1 (Canada)]. E-mail:


    During solidification of an alloy, solute elements may pile up ahead of the growing interface due to their lower solubility within the solid material, when the distribution or partition coefficient is less than unity. In this paper, laser ablation inductively coupled plasma mass spectrometry, LA-ICP-MS, as a new method, is used to analyze solute distribution within primary {alpha}-Al particles formed during solidification of hypoeutectic Al-Si alloys. The results are further compared with those obtained from electron probe micro-analysis, EPMA, of the same specimens. There is a good agreement between the results obtained by both techniques.

  1. Directional solidification of metal-gas eutectic and fabrication of regular porous metals

    Yuan LIU


    Full Text Available Directional solidification of metal-gas eutectic (Gasar is a novel process for making regular porous metals.This process is based on a solid-gas eutectic reaction involving a gaseous medium and a metal or a ceramic phase, and allows an easy control of the porosity, such as its pore size, pore orientation and morphology in a wide range by properly adjusting its melting and solidification conditions. The latest progress and our research work in this field are reviewed inthis paper.

  2. Al-Si-Re Alloys Cast by the Rapid Solidification Process / Stopy Al-Si-Re Odlewane Metodą Rapid Solidification

    Szymanek M.


    Full Text Available The aim of the studies described in this article was to present the effect of rare earth elements on aluminium alloys produced by an unconventional casting technique. The article gives characteristics of the thin strip of Al-Si-RE alloy produced by Rapid Solidification (RS. The effect of rare earth elements on structure refinement, i.e. on the size of near-eutectic crystallites in an aluminium-silicon alloy, was discussed. To determine the size of crystallites, the Scherrer X-ray diffraction method was used. The results presented capture relationships showing the effect of variable casting parameters and chemical composition on microstructure of the examined alloys. Rapid Solidification applied to Al-Si alloys with the addition of mischmetal (Ce, La, Ne, Pr refines their structure.

  3. Solidification Structure and Macrosegregation of Billet Continuous Casting Process with Dual Electromagnetic Stirrings in Mold and Final Stage of Solidification: A Numerical Study

    Jiang, D.; Zhu, M.


    Coupling macroscale heat transfer and fluid flow with microscale grain nucleation and crystal growth, a mixed columnar-equiaxed solidification model was established to study the SWRT82B steel solidification structure and macrosegregation in 160 mm × 160 mm billet continuous casting with dual electromagnetic stirrings in mold and final stage of solidification (M-EMS and F-EMS). In the model, the phases of liquid, columnar, and equiaxed were treated separately and the initial growing equiaxed phase, which could move freely with liquid, was regarded as slurry. To obtain the equiaxed grains nucleation and columnar front evolution, the unit tracking method and the columnar front tracking model were built. The model was validated by magnetic induction intensity of stirrer, billet surface temperature, and carbon segregation. The equiaxed phase evolution and the solute transport with effect of fluid flow and grains transport were described in this article. The results show that the equiaxed phase ratio will not increase obviously with higher current intensity of M-EMS, while the negative segregation near the strand surface becomes more serious. The negative segregation zone near the billet center and the center positive segregation come into being with the effect of equiaxed grains sedimentation and liquid thermosolutal flow. It is also found that the liquid solute transport in the F-EMS zone becomes the main factor with higher current intensity rather than the solidification rate, and therefore, the final billet center segregation decreases first and then turns to rise with the current intensity. The optimal current intensities of M-EMS and F-EMS proposed for SWRT82B billet continuous casting are 200 and 400 A, respectively.

  4. Solidification Structure and Macrosegregation of Billet Continuous Casting Process with Dual Electromagnetic Stirrings in Mold and Final Stage of Solidification: A Numerical Study

    Jiang, D.; Zhu, M.


    Coupling macroscale heat transfer and fluid flow with microscale grain nucleation and crystal growth, a mixed columnar-equiaxed solidification model was established to study the SWRT82B steel solidification structure and macrosegregation in 160 mm × 160 mm billet continuous casting with dual electromagnetic stirrings in mold and final stage of solidification (M-EMS and F-EMS). In the model, the phases of liquid, columnar, and equiaxed were treated separately and the initial growing equiaxed phase, which could move freely with liquid, was regarded as slurry. To obtain the equiaxed grains nucleation and columnar front evolution, the unit tracking method and the columnar front tracking model were built. The model was validated by magnetic induction intensity of stirrer, billet surface temperature, and carbon segregation. The equiaxed phase evolution and the solute transport with effect of fluid flow and grains transport were described in this article. The results show that the equiaxed phase ratio will not increase obviously with higher current intensity of M-EMS, while the negative segregation near the strand surface becomes more serious. The negative segregation zone near the billet center and the center positive segregation come into being with the effect of equiaxed grains sedimentation and liquid thermosolutal flow. It is also found that the liquid solute transport in the F-EMS zone becomes the main factor with higher current intensity rather than the solidification rate, and therefore, the final billet center segregation decreases first and then turns to rise with the current intensity. The optimal current intensities of M-EMS and F-EMS proposed for SWRT82B billet continuous casting are 200 and 400 A, respectively.

  5. Front tracking in the numerical simulation of binary alloy solidification

    Simpson, James Edward


    A model for directional solidification in dilute binary alloys is presented. The energy equation is solved for the temperature field, while the species equation is solved for the solute distribution. Either the vorticity-vector potential formulation or the pressure-velocity formulation is used to solve the governing equations for the velocity field. The constitutive equations are solved using a fully transient scheme. A variety of fast numerical schemes for solving sparse systems are used in the solution procedure. A single domain approach is used for the solution scheme for the energy and concentration equations. The effects of phase-change (energy equation) and solute rejection at the advancing solid/liquid interface (concentration equation) are handled via the introduction of appropriate source terms. The numerical approach was validated by comparing numerical results to data from a series of experiments of the Bridgman growth of pure succinonitrile. These experiments were performed as part of this work and are explained in detail. The numerical results agree well with the experimental data in terms of interface shape, temperature and velocity data. The key contribution of this work is the investigation of the Bridgman crystal growth of bismuth-tin in support of NASA's MEPHISTO project. The simulations reported in this work are among the first fully transient simulations of the process; no simplifying steady state approximations were used. Results are obtained for Bi-Sn alloys at a variety of initial concentrations and gravity levels. For most of the work, the solid/liquid interface temperature is assumed to be constant. For the richer alloy (Bi-1.0 at.% Sn) the results indicate that a secondary convective cell, driven by solutal gradients, forms near the interface. The magnitude of the velocities in this cell increases with time, causing increasing solute segregation at the solid/liquid interface. At lower gravity levels, convection-induced segregation is

  6. Three-Dimensional Stereoscopic Tracking Velocimetry and Experimental/Numerical Comparison of Directional Solidification

    Lee, David; Ge, Yi; Cha, Soyoung Stephen; Ramachandran, Narayanan; Rose, M. Franklin (Technical Monitor)


    Measurement of three-dimensional (3-D) three-component velocity fields is of great importance in both ground and space experiments for understanding materials processing and fluid physics. The experiments in these fields most likely inhibit the application of conventional planar probes for observing 3-D phenomena. Here, we present the investigation results of stereoscopic tracking velocimetry (STV) for measuring 3-D velocity fields, which include diagnostic technology development, experimental velocity measurement, and comparison with analytical and numerical computation. STV is advantageous in system simplicity for building compact hardware and in software efficiency for continual near-real-time monitoring. It has great freedom in illuminating and observing volumetric fields from arbitrary directions. STV is based on stereoscopic observation of particles-Seeded in a flow by CCD sensors. In the approach, part of the individual particle images that provide data points is likely to be lost or cause errors when their images overlap and crisscross each other especially under a high particle density. In order to maximize the valid recovery of data points, neural networks are implemented for these two important processes. For the step of particle overlap decomposition, the back propagation neural network is utilized because of its ability in pattern recognition with pertinent particle image feature parameters. For the step of particle tracking, the Hopfield neural network is employed to find appropriate particle tracks based on global optimization. Our investigation indicates that the neural networks are very efficient and useful for stereoscopically tracking particles. As an initial assessment of the diagnostic technology performance, laminar water jets with and without pulsation are measured. The jet tip velocity profiles are in good agreement with analytical predictions. Finally, for testing in material processing applications, a simple directional solidification

  7. Small hazardous waste generators in developing countries: use of stabilization/solidification process as an economic tool for metal wastewater treatment and appropriate sludge disposal.

    Silva, Marcos A R; Mater, Luciana; Souza-Sierra, Maria M; Corrêa, Albertina X R; Sperb, Rafael; Radetski, Claudemir M


    The aim of this study was to propose a profitable destination for an industrial sludge that can cover the wastewater treatment costs of small waste generators. Optimized stabilization/solidification technology was used to treat hazardous waste from an electroplating industry that is currently released untreated to the environment. The stabilized/solidified (S/S) waste product was used as a raw material to build concrete blocks, to be sold as pavement blocks or used in roadbeds and/or parking lots. The quality of the blocks containing a mixture of cement, lime, clay and waste was evaluated by means of leaching and solubility tests according to the current Brazilian waste regulations. Results showed very low metal leachability and solubility of the block constituents, indicating a low environmental impact. Concerning economic benefits from the S/S process and reuse of the resultant product, the cost of untreated heavy metal-containing sludge disposal to landfill is usually on the order of US$ 150-200 per tonne of waste, while 1tonne of concrete roadbed blocks (with 25% of S/S waste constitution) has a value of around US$ 100. The results of this work showed that the cement, clay and lime-based process of stabilization/solidification of hazardous waste sludge is sufficiently effective and economically viable to stimulate the treatment of wastewater from small industrial waste generators.

  8. A macroscopic constitutive model of temperature-induced phase transition of polycrystalline Ni{sub 2}MnGa by directional solidification

    Zhu, Yuping, E-mail:; Gu, Yunling; Liu, Hongguang


    Directional solidification technology has been widely used to improve the properties of polycrystalline Ni{sub 2}MnGa materials. Mechanical training can adjust the internal organizational structures of the materials, reduce the stress of twin boundaries motion, and then result in larger strain at lower outfield levels. In this paper, we test the microscopic structure of Ni{sub 2}MnGa polycrystalline ferromagnetic shape memory alloy produced by directional solidification and compress it along two axes successively for mechanical training. The influences of pre-compressive stresses on the temperature-induced strains are analyzed. The macroscopic mechanical behaviors show anisotropy. According to the generating mechanism of the macroscopic strain, a three-dimensional constitutive model is established. Based on thermodynamic method, the kinetic equations of the martensitic transformation and inverse transformation are presented considering the driving force and energy dissipation. The prediction curves of temperature-induce strains along two different directions are investigated. And the results coincide well with the experiment data. It well explains the macroscopic anisotropy mechanical behaviors and fits for using in engineering.

  9. Influence of mixture ratio and pH to solidification/stabilization process of hospital solid waste incineration ash in Portland cement.

    Sobiecka, Elzbieta; Obraniak, Andrzej; Antizar-Ladislao, Blanca


    Solidification/stabilization (S/S) is an established utilization technology to treat hazardous wastes. This research explored the influence of pH (3-12) on the immobilization of heavy metals present in five mixtures of hospital solid waste incinerator ash and Portland cement, following two different processes of waste solidification/stabilization (cement hydration and granulation). In general, cement hydration process resulted in more stable products than granulation process. A high ash content in the mixture with Portland cement (60wt%) resulted in the highest immobilization of Pb(2+) and Cu(2+), while a low ash content in the mixture (10wt%) resulted in the lowest leachability of Zn(2+). When ash and Portland cement was mixed in equal proportions (50wt%) the highest encapsulation was observed for Ni(2+), Cd(2+) and Cr(3+). Neutral and weak alkaline pH values within the range pH=7-8 resulted in the lowest leachability of the monitored heavy metals.

  10. Influence of forced convection on solidification and remelting in the developing mushy zone

    Wu, M.; Vakhrushev, A.; Ludwig, A.; Kharicha, A.


    The mushy zone and solid shell formed during solidification of a continuous casting are mostly uneven, and this unevenness of shell growth might lead to surface defects or breakout. One known example is the unevenness of shell growth at the impingement point between the jet flow (coming from submerged entry nozzle) and the solidification front. This phenomenon is primarily understood as the local remelting caused by the superheat of the melt, which is continuously brought by the jet flow towards the solidification front. A recent study of the authors [Metall. Mater. Trans. B, 2014, in press] hinted that, in addition to the aforementioned superheat-induced local remelting (1), two other factors also affect the shell growth. They are (2) the advection of latent heat in the semi-solid mushy zone and (3) the enhanced dissipation rate of energy by turbulence in the bulk-mush transition region. This paper is going to perform a detailed numerical analysis to gain an insight into the flow-solidification interaction phenomena. Contributions of each of the above factors to the shell formation are compared.

  11. An integrated meso-scale numerical model of melting and solidification in laser welding

    Duggan, G.; Tong, M.; Browne, D. J.


    The authors present an integrated numerical model for the simulation of laser spot welding of an aluminium alloy at meso-scale in 2D. This model deals with the melting of the parent materials which form the weld pool and the subsequent solidification of the liquid metal in the pool, during the welding process. The melting of the parent materials due to the applied heating power is an important phenomenon, which determines the conditions at the onset of solidification, such as the geometry of the weld pool and the distribution of the temperature field. An enthalpy method is employed to predict the melting during the heating phase of welding. A Gaussian distribution is used to model the heat input from the laser. Once the laser beam is switched off and the melting halts, solidification commences. The UCD front tracking model [1,2] for alloy solidification is applied to predict the advancement of the columnar dendritic front, and a volume-averaging formulation is used to simulate nucleation and growth of equiaxed dendrites. A mechanical blocking criterion is used to define dendrite coherency, and the columnar-to-equiaxed transition within the weld pool is predicted.


    Barbora Lyčkova


    Full Text Available One of the common treatment methods for the hazardous waste is the cement and cement-lime based solidification/stabilization (S/S. This article deals with the possibility of currently used recipe modification using fluidized bed heating plant ashes as an agent.

  13. Recovery and safer disposal of phosphate coating sludge by solidification/stabilization.

    Ucaroglu, Selnur; Talinli, Ilhan


    Solidification/stabilization (S/S) of automotive phosphate coating sludge (PS) containing potentially toxic heavy metals was studied. The hazardous characteristics of this waste were assessed according to both Turkish and U.S. Environmental Protection Agency (EPA) regulations for hazardous solid waste. Unconfined compressive strength (UCS) and leaching behavior tests of the solidified/stabilized product were performed. Solidification studies were conducted using Portland cement (PC) as the binder. UCS was found to decrease with increasing waste content. It was found that recovery of the waste for construction applications was possible when the waste content of the mortar was 20% and below, but solidification for safe disposal was achieved only when higher waste concentrations were added. Cu, Cr, Ni, Pb and Zn were found to be significantly immobilized by the solidification/stabilization process. Ni and Zn, which were present at particularly high concentrations (2.281 and 135.318 g/kg respectively) in the PS, had highest the retention levels (94.87% and 98.74%, respectively) in the PC mortars. The organic contaminants and heavy metals present in PS were determined to be immobilized by the S/S process in accordance with the BS 6920 standard. Thus, the potential for hazardous PS waste to adversely impact human health and the environment was effectively eliminated by the S/S procedure. We conclude that S/S-treated PS is safe for disposal in landfills, while recovery of S/S-treated PS constituents remains possible.

  14. Solidification microstructures in a short fiber reinforced alloy composite containing different fiber fractions

    JING Qing-xiu


    Full Text Available The solidification microstructures and micro-segregation of a fiber reinforced Al-9 Cu alloy, containing different volume fractions of Al2O3 short fibers about 6 μm diameter and made by squeeze casting have been studied. The results indicate that as volume fraction of fiber Vf increases, the size of final grains becomes finer in the matrix. If λf /λ>1, the fibers have almost no influence on the solidification behavior of the matrix, so the final grains grow coarse, where λf is the average inter-fiber spacing and λ is the secondary dendrite arm spacing. While if λf /λ<1, the growth of crystals in the matrix is affected significantly by the fibers and the grain size is reduced to the value of the inter-fiber spacing. The fibers influence the average length of a solidification volume element L of the matrix and also influence the solidification time θt of the matrix. As a result of fibers influencing L and θt, the micro-segregation in the matrix is improved when the composite contains more fibers, although the level of the improvement is slight. The Clyne-Kurz model can be used to semi-quantitatively analyze the relationship between Vf and the volume fraction fe of the micro-segregation eutectic structure.

  15. Thermoelastic Stability Analysis of Solidification of Pure Metals on a Coated Planar Mold of Finite Thickness

    Demir, Mehmet Hakan; Yigit, Faruk


    A theoretical model for investigating the thermoelastic instability/mechanism during pure metal solidification on a coated mold of finite thickness is developed. This study extends the previous theoretical works on growth instability during solidification process by investigating the effects of an added coating layer. Mold coating is one of the most important factors controlling the heat transfer rate, and hence it has a very important role on the solidification rate and the development of microstructure. In this model, thermal and mechanical problems are coupled through the pressure-dependent contact resistances at mold/coating and coating/shell interfaces. The thermal diffusivities of solidified shell, coating, and mold materials are assumed to be zero. This assumption provides us to solve heat transfer problem analytically. A linear perturbation method is used to simplify complexity of the modeled solidification problem, and governing equations are solved numerically using a variable step variable order predictor-corrector algorithm. The effects of coating layer thickness and coupling rates at shell/coating and coating/mold interfaces are investigated in detail. The results show that coating thickness has destabilizing effect on the growth instability when the coupling rates are small. However, when these coupling rates are increased individually or together, the destabilizing effect of coating thickness turns to be stabilizing. On the other hand, coupling rates have generally destabilizing effects on the process, but an increase in the thickness of coating leads to diminishing coupling rates effect in some cases.

  16. Validation of a 3D multi-physics model for unidirectional silicon solidification

    Simons, P.; Lankhorst, A.M.; Habraken, A.; Faber, A.J.; Tiuleanu, D.; Pingel, R.


    A model for transient movements of solidification fronts has been added to X-stream, an existing multi-physics simulation program for high temperature processes with flow and chemical reactions. The implementation uses an enthalpy formulation and works on fixed grids. First we show the results of a

  17. Solidification of Cu-Water nanofluid in a trapezoidal cavity: A CFD study

    Sharma, R. K.; Ganesan, P.; Metselaar, I. H.


    A numerical study has been carried out to investigate the solidification of a binary mixture of water and Cu nanoparticles inside a horizontal trapezoidal cavity of different aspect ratio under specific given boundary conditions for temperature and concentration gradients. The vertical side walls of the cavity are insulated while the top wall temperature is kept lower than that of the bottom wall. The effect of parameters such as the ratio of the cavity length to height (aspect ratio), the cold wall temperature (-5 to -30 °C) and the initial temperature of the nanofluid (0 °C to16 °C) on solidification time is investigated. The moving solid-liquid interface is obtained using Enthalpy-porosity technique in the model. We found that the solidification time decreases with the increase of the aspect ratio (i.e., a longer trapezoidal cavity) and the decrease of cold wall temperature. Aspect ratio is found to give a prominent effect. However, the initial temperature of fluid does not affect the solidification time much.

  18. Solidification microstructures in a short fiber reinforced alloy composite containing different fiber fractions


    The solidification microstructures and micro-segregation of a fiber reinforced Al-9 Cu alloy, containing different volurne fractions of Al2O3 short fibers about 6μm diameter and made by squeeze casting have been studied. The results indicate that as volume fraction of fiber Vf increases, the size of final grains becomes finer in the matrix. If λf/λ> 1, the fibers have almost no influence on the solidification behavior of the matrix, so the final grains grow coarse, where λf is the average inter-fiber spacing and λ is the secondary dendrite arm spacing. While if λf/λ< 1, the growth of crystals in the matrix is affected significantly by the fibers and the grain size is reduced to the value of the inter-fiber spacing. The fibers influence the average length of a solidification volume element L of the matrix and also influence the solidification time θt of the matrix. As a result of fibers influencing L and θt, the micro-segregation in the matrix is improved when the composite contains more fibers, although the level of the improvement is slight. The Clyne-Kurz model can be used to semi-quantitatively analyze the relationship between Vf and the volume fraction fe of the micro-segregation eutectic structure.

  19. Lattice constant and hardness of InSb:Bi bulk crystals grown by vertical directional solidification

    Maske, Dilip; Deshpande, Manisha; Choudhary, Rashmi; Gadkari, Dattatray


    Ingots of the Bi doped InSb (InSb1-xBix) bulk semiconductor crystals were grown by specially designed Vertical Directional Solidification (VDS) technique. Substrates of seven crystals grown with various composition values of x (0 ≤ x 0.05.

  20. Effect of alloying elements on solidification of primary austenite in Ni-Mn-Cu cast iron

    A. Janus


    Full Text Available Within the research, determined were direction and intensity of alloying elements influence on solidification way (directional orvolumetric of primary austenite dendrites in hypoeutectic austenitic cast iron Ni-Mn-Cu. 50 cast shafts dia. 20 mm were analysed.Chemical composition of the alloy was as follows: 1.7 to 3.3 % C, 1.4 to 3.1 % Si, 2.8 to 9.9 % Ni, 0.4 to 7.7 % Mn, 0 to 4.6 % Cu, 0.14 to0.16 % P and 0.03 to 0.04 % S. The discriminant analysis revealed that carbon influences solidification of primary austenite dendrites most intensively. It clearly increases the tendency to volumetric solidification. Influence of the other elements is much weaker. This means that the solidification way of primary austenite dendrites in hypoeutectic austenitic cast iron Ni-Mn-Cu does not differ from that in an unalloyed cast iron.