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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
351

A microtexture characterization of recrystallization and twinning in magnesium

Martin, Étienne January 2010 (has links)
The evolution of texture and microstructure during the deformation of two Mg-based (+Al, Mn, Zn) alloys has been studied under various conditions of temperature and strain rate. The tested materials were taken from AZ31 and AM30 extruded tubes. The mechanism of recrystallization was investigated by using uniaxial compression, while twinning was studied under uniaxial tension testing. Optical metallography, X-ray analysis and EBSD techniques were employed to study the texture and grain scale development. The first part of the investigation focused on the misorientations that apply to the different mechanisms of new grain formation during the hot compression of magnesium alloy AM30. This approach led to the identification of three types of microstructural features produced during deformation at high temperature (350°C at a strain rate of 0.001s-1). In the first, microbands were produced in grain interiors due to the accumulation of basal dislocations. Their orientation changes involve rotations of the basal planes to a more favorable orientation for glide, leading to geometric softening. In the second, two different types of DRX nuclei were observed, i.e. those formed i) by bulging and ii) by continuous dynamic recrystallization. Although visually distinct, the two mechanisms are formed as a result of dislocation-based processes that produce c-axis rotations toward the loading axis. For low misorientation angles, the boundary character is consistent with the accumulation of basal dislocations. Once nuclei of the latter two types have formed, however, only those orientations belonging to the RD-TD fibre are able to grow. In this way, recrystallization leads to the retention of the main characteristics of the initial RD-TD texture. The second part focused on the mechanisms associated with variant selection during contraction and double twinning. These twins are of practical interest since they have a high potential for texture randomization. For this purpose, magn / L'évolution des orientations cristallographiques préférentielles et de la microstructure de deux alliages de magnésium, soit AZ31 et AM30, a été étudiée à des températures et à des vitesses de déformation différentes. Les échantillons des deux alliages utilisés ont été prélevés sur des tubes extrudés. Des essais de traction et de compression uniaxiales ont été effectués dans le but de comprendre les mécanismes à l'origine de la formation des macles et des grains recristallisés. L'effet de la recristallisation sur les macles primaires (ou de contraction) et secondaires (ou d'extension) a finalement été étudié. La première partie de l'étude porte sur les relations de désorientation qui sont associées aux joints de grain qui se forment durant la compression de l'alliage de magnésium AM30 à haute température (soit 350 °C, et à une vitesse de déformation de 0.001s-1). Cette méthode de caractérisation a permis l'identification de trois types de composantes structurales. Premièrement, des microbandes se forment au centre des grains par l'accumulation de dislocations basales. Ces bandes produisent des rotations qui positionnent les plans de glissement basal de façon à faciliter le glissement des dislocations. Ainsi, un adoucissement géométrique est généré, ce qui a pour effet de diminuer la contrainte d'écoulement. Deuxièmement, la recristallisation engendre la formation de nouveaux grains aux joints des grains initiaux. Deux mécanismes de recristallisation sont observés : les nouveaux grains sont créés soit par la migration des joints de grain ou par recristallisation continue. Bien que visuellement distincts, ces deux mécanismes sont tout deux initiés par une accumulation de dislocations. Les résultats ont démontré que les nouveaux grains ayant une orientation similaire à celle des grains initiaux sont avantagés au niveau de la croissance. Ainsi, la recristallisation a tendance à retenir les orientations
352

Welding High Strength Modern Line Pipe Steel

Goodall, Graeme January 2011 (has links)
The effect of modern mechanized girth welding on high strength line pipe has been investigated. The single cycle grain coarsened heat affected zone in three grade 690 line pipe steels and a grade 550 steel has been simulated using a Gleeble thermo-mechanical simulator. The continuous cooling transformation diagrams applicable to the grain coarsened heat affected zone resulting from a range of heat inputs applicable to modern mechanized welding have been established by dilatometry and metallography. The coarse grained heat affected zone was found to transform to lath martensite, bainite, and granular bainite depending on the cooling rate. The impact toughness of the steels was measured using Charpy impact toughness and compared to the toughness of the grain coarsened heat affected zone corresponding to a welding thermal cycle. The ductile to brittle transition temperature was found to be lowest for the steel with the highest hardenability. The toughness resulting from three different thermal cycles including a novel interrupted intercritically reheated grain coarsened (NTR ICR GC HAZ) that can result from dual torch welding at fast travel speed and close torch spacing have been investigated. All of the thermally HAZ regions showed reduced toughness that was attributed to bainitic microstructure and large effective grain sizes. Continuous cooling transformation diagrams for five weld metal chemistries applicable to mechanized pulsed gas metal arc welding of modern high strength pipe steel (SMYS>550 MPa) have been constructed. Welds at heat inputs of 1.5 kJmm-1 and 0.5 kJmm-1 have been created for simulation and analysis. Dilatometric analysis was performed on weld metal specimens cut from single pass 1.5 kJmm-1 as deposited beads. The resulting microstructures were found to range from martensite to polygonal ferrite. There is excellent agreement between the simulated and as deposited weld metal regions. Toughness testing indicates improved energy absorption at -20 °C with increased cooling time. / L'effet des méthodes modernes de soudage circonférentiel mécanisé sur des aciers à forte résistance utilisés pour les tubes de canalisation a été investigué. La zone affectée thermiquement ayant subi une croissance de grain lors d'un cycle thermique simple de soudage a été simulée pour trois grades d'acier à tubes de canalisation 690 et un grade d'acier 550 à l'aide d'un appareil de simulation thermomécanique Gleeble. Les diagrammes de transformation en refroidissement continu pour la zone affectée thermiquement ayant subi une croissance de grains ont été établis pour un spectre de chaleur induite représentatif du procédé de soudage mécanisé en utilisant la dilatométrie ainsi que des analyses métallographiques. Il résulte que la zone affectée thermiquement ayant subi une croissance de grain connaît un changement de phase vers une martensite massive, une bainite ou une bainite granulaire selon le taux de refroidissement rencontré. La résistance des aciers étudiés a été mesurée par essais Charpy et comparée à la résistance obtenue pour la zone affectée thermiquement ayant subi une croissance de grains correspondant à un cycle thermique de soudage. Le plus bas température de transition ductile-fragile a été obtenue pour les grades d'acier ayant la plus grande aptitude à la trempe. La résistance résultante des structures obtenues pour trois différents cycles thermique, notamment un nouveau cycle thermique interrompu par recuit intercritique similaire à l'effet que peut avoir un soudage à double torche à déplacement rapide et espacement réduit, a été étudié. Toutes les zones affectée thermiquement montrent une baisse de résistance causée par l'apparition d'une structure bainitique et la croissance des grains.Les diagrammes de transformations en refroidissement continu ont été établis pour 5 alliages de soudage applicable pour le soudage pulsé à l'arc sous gas des aciers à tube modernes à haute résistance. Des soudures avec un apport de chaleur de 1,5 kJmm-1 et 0,5 kJmm-1 ont été utilisées pour les simulations et les analyses. Des essais de dilatométrie ont été faits sur des échantillons prélevés des cordons de soudure déposés en une passe à 1,5 kJmm-1. L'observation métallographique des échantillons présente une structure allant de la martensite à la ferrite polygonale. Une excellente concordance a été établie entre la structure du métal obtenu par simulation et telle que déposé. Les tests de résistance indiquent une amélioration de l'énergie absorbée à -20°C lorsque le temps de refroidissement est plus long.
353

Ladle shrouds as flow control devices for tundish operations

Morales Higa, Ken January 2011 (has links)
The performance characteristics of a tundish, such as the flotation of inclusions and of slag entrainment, are largely influenced by the fluid flow phenomena. Physical and mathematical modeling in water is widely used to understand fluid flows in a tundish, and as a tool to improve, control and design procedures for high quality steel processing operations. These approaches were used to study the performance of fluid flow for a new design of ladle shroud. The new "Dissipative Ladle Shroud" (DLS) was studied, using a one third scale, delta shaped, four-strand tundish. The results were compared with those achieved with the standard ladle shroud. The standard k-ε turbulence model, together with the continuity and momentum equations, were employed in order to analyze, and visualize, the velocity fields generated within the tundish operating at steady state. Different cases have been analyzed, including a conventional ladle shroud (LS) with a bare tundish, and a tundish furnished with an impact pad. Similarly, the new design of the shroud (DLS) was studied under equivalent conditions. The physical experiments included the use of Particle Image Velocimetry (PIV) and conductivity tracer techniques. The PIV measured the instantaneous velocities at the outlet of the DLS and the LS at different flow rates, showing the detailed jetting characteristics of water leaving the two types of ladle shroud. Residence Time Distribution (RTD) curves were also obtained for the different flow arrangements previously mentioned, and the dispersion of a colored dye tracer was observed at different intervals of time during tundish operation, and analyzed using the video visualization technique. / Les caractéristiques de performance d'un répartiteur telles la flottaison des inclusions et de la scorie sont largement influencées par les phénomènes d'écoulement des fluides. Les modèles physiques et mathématiques sont communément utilisés pour comprendre la dynamique des fluides dans un répartiteur et pour améliorer, contrôler et concevoir les procédés de traitement d'acier de haute qualité. Cette approche a été utilisée pour étudier la performance de la dynamique des fluides avec un nouveau design de poche de couleé. La nouvelle "Dissipative Ladle Shroud" (DLS) a été étudiée en utilisant une échelle d'un tiers de répartiteur, en forme delta et possédant quatre drains de couleé. Les résultats ont été comparés avec ceux obtenues avec le poche de couleé normal. Le modèle de turbulence k-ε, avec les équations de conservation des masses et de quantité de mouvement, a été utilisé pour analyser et visualiser les champs de vitesse générés par l'opération du répartiteur en conditions stables. Différents cas ont été analysés, incluant un "conventional ladle shroud" (CLS) avec un répartiteur vide, et un répartiteur muni d'un bloc d'impact. De même, le nouveau design de poche de couleé (DLS) a été étudié sous des conditions équivalentes. Les expériences physiques incluent l'utilisation du "Particle Image Velocimetry" (PIV) et de techniques de traceur de conductivité. Le PIV mesure la vitesse instantanée à l'issue du DLS et du CLS à différents taux de flux, en montrant les caractéristiques détaillées du jet d'eau quittant les deux types de poche de couleé. Des courbes de Distribution des Temps de Résidence (RTD) ont également été obtenues pour les différents arrangements de flux précédemment mentionnés, et la dispersion d'un traceur de teinture colorée a été observée et analysé à différent intervalles de temps pendant l'opération du répartiteur en utilisant une vidéo de visualisation technique.
354

Selenium removal from aqueous solutions

Geoffroy, Nicolas January 2011 (has links)
The aqueous chemistry of the reduction of selenious species by sodium dithionite, sodium sulfide, stannous chloride and sulfur dioxide/sulfite was studied. The resultant precipitates were characterized using different techniques, including scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. In the case of sodium dithionite, the research showed that, at initial pH below 1.7 and dithionite stoichiometric excess above three, less than 0.5 ug/L remained in solution less than a minute after the addition of the reagent. However, it was found that the precipitate, mainly composed of red amorphous selenium, was not stable in the presence of the dithionite decomposition by-products and partially redissolved after several hours. In the case of the reaction involving selenious acid and sulfide ions, the results showed that, below a pH of approximately 7.0, the precipitation reaction was complete in less than 10 minutes at a sulfide to selenium ratio above 1.8 with less than 5 ug/L of soluble selenium remaining in solution. The precipitate was deduced to be a Se-S solid solution consisting of ring molecules of the following SenS8−n formula. However, above pH 7 the removal of selenium was incomplete due to formation of a stable colloidal suspension. In the case of industrial solutions, high dissolved sulfur dioxide content (> 5g/L) decreases the effectiveness of the precipitation reaction. Concerning the removal of Se(IV) by tin(II), at an initial pH below 1.3 and molar ratios above two, less than 5 ug/L of selenium(IV) remained in solution after reduction. The reaction products, were determined to be composed of approximately equal amounts of tin selenide and tin dioxide with a small amount of selenium(IV) being adsorbed on the latter. Finally, it was found that Se(IV) can be reduced quantitatively at ambient temperature via a combination of sulfite reduction and ultra-acidification to a colloidal form that can be determined using turbidimetry. The developed technique was shown to be equally effective with real Se(IV)-bearing industrial solutions generated in a zinc concentrate roasting operation hence making the method particularly useful as on-line process monitoring and control tool. / La chimie aqueuse des réactions de réduction entre les ions sélénieux et le dithionite de sodium, le sulfure de sodium et les ions stanneux ont été étudiées. Les précipités résultant de cette réaction ont été caractérisés par différentes techniques comme la microscopie électronique à balayage, la diffraction à rayons X et la spectrométrie de photoélectrons induits par rayons X. Dans le cas du dithionite de sodium, ce projet a démontré que, pour un pH initial inférieur à 1.7 et un ratio stœchiométrique de dithionite supérieur à trois, moins de 0.5 ug/L de sélénium(IV) restait en solution moins d'une minute après l'addition du réactif. Par contre, le précipité, formé en majorité de sélénium rouge amorphe, n'était pas stable en présence des composés issus de la réaction de décomposition du dithionite et était partiellement re-dissous après quelques heures. Dans le cas de la réaction entre l'acide sélénieux et le sulfure de sodium, les résultats indiquaient que pour un ratio molaire sulfur/sélénium plus grand que 1.8 et un pH sous 7.0 la réaction de précipitation était complète et moins de 5 ug/L de sélénium (IV) restait en solution. Aucune précipitation n'a été constatée pour un pH plus élevé que 9.5 et la réaction était incomplète pour un pH entre 7 et 9.5. Le précipité semblait être composé d'une solution solide Se-S formé de molécules circulaires répondant à la formule SenS8−n. Par contre, pour un pH plus élevé que 7, la précipitation du sélénium était incomplète à cause de la formation d'un précipité de sélénium colloïdal. De plus, dans le cas des solutions industrielles, de hautes concentrations de dioxyde de souffre dissous (> 5g/L) diminuait l'efficacité de la réaction de précipitation.En ce qui concerne la réaction entre le sélénium(IV) et l'étain, pour un pH initial sous 1.3 et un ratio molaire étain/sélénium plus grand que deux, moins de 5 ug/L de sélénium restait en solution après la réaction. Les analyses ont révélé que le précipité était composé de parts approximativement égales de séléniure d'étain et de dioxyde d'étain et que ce dernier pouvait adsorber une petite quantité d'ions sélénieux. Finalement, ce projet a démontré que le sélénium(IV) peut être réduit, à la température ambiante, par une solution ultra-acide riche en sulfites. Une fois le sélénium précipité sous forme colloïdale, la concentration originale de celui-ci peut ensuite être déterminée par turbidimétrie. Par ailleurs, cette méthode est aussi efficace sur des solutions industrielles contenant du sélénium(IV) et peut donc être appliquée pour l'analyse en temps réel de cet élément.
355

Surface charge characterization and flotation of an ultramafic nickel ore

Uddin, Salah January 2012 (has links)
AbstractAbout 300 million tonnes of inferred Ni resource in ultramafic hosted rocks is present in 'Thompson Nickel Belt' in north central Manitoba. The processing challenges result from electrostatic interaction between pentlandite (the main Ni-mineral) and serpentine (the main gangue and one of the MgO minerals). As a contribution to meeting the challenge, the thesis examines the role of particle and bubble surface charge and the effect of fibre disintegration on flotation behavior of an ultramafic Ni ore sample. For surface charge characterization the sedimentation potential technique was used. A novel integrated device was developed to measure sedimentation potential, conductivity and pH simultaneously. Maxwell's model was used to calculate volume fraction of dispersed phase from conductivity, and zeta potential, when appropriate, was calculated from the Smoluchowski equation. The technique was validated by showing good agreement with iso-electric point for alumina, silica and bubble suspensions with electrophoresis measurements. The technique was extended to characterize mixed minerals including ultramafic ore, and bubbles in the presence of particles. The results provided some evidence of metal ion adsorption on particles and the possibility of non-hydrophobic particle attachment to bubbles. The latter was reinforced by visualization studies of a pendant bubble exposed to particle suspensions.A novel fibre disintegration strategy was devised combining both chemical (acid) and physical (grinding) treatment based on work to enhance carbon dioxide uptake by serpentine. Using HCl, subsequent conventional flotation (amyl xanthate, soda ash and MIBC) gave significantly improved results over the untreated ore. Using H2SO4, arguably the practical option led to flotation without collector due to elemental sulphur formation on pentlandite, and without frother due to high ionic strength solutions. Improved Ni grade-recovery with higher MgO mineral rejection was achieved. Structural changes in the fibres were followed using various spectroscopic techniques and a mechanism of fibre disintegration suggested. / Environ 300 millions de tonnes de ressources inférées de Ni ultramafiques hébergé est présent dans 'ceinture nickélifère de Thompson' dans le centre-nord du Manitoba. Le traitement des défis résultant de l'interaction électrostatique entre pentlandite (le principal Ni-minéraux) et la serpentine. En tant que contribution à relever le défi, la thèse examine le rôle des particules et la charge de surface des bulles et l'effet de la désintégration des fibres sur le comportement de flottaison d'un échantillon de minerai de nickel ultramafiques. Pour la caractérisation de charge de surface de la technique de sédimentation potentielle a été utilisée. Un nouveau dispositif intégré a été développé pour mesurer le potentiel de sédimentation, la conductivité et le pH simultanément. Le modèle de Maxwell a été utilisée pour calculer la fraction volumique de phase dispersée de la conductivité, et le potentiel zêta, le cas échéant, a été calculée à partir de l'équation de Smoluchowski. La technique a été validée en montrant un bon accord avec l'iso-électrique de point pour les suspensions d'alumine, de silice et de bulles avec des mesures d'électrophorèse. La technique a été étendue afin de caractériser les minéraux mélangés, y compris de minerai ultramafiques, et des bulles dans la présence de particules. Les résultats ont fourni des preuves de ion métallique adsorption sur les particules et la possibilité de l'attachement des particules non-hydrophobe à bulles. Ce dernier a été renforcée par des études de la visualisation d'une bulle Pendentif exposés à des suspensions de particules.Une stratégie nouvelle fibre de désintégration a été conçu combinant à la fois chimique (acide) et physiques (broyage) un traitement basé sur le travail pour améliorer l'absorption du dioxyde de carbone par la serpentine. En utilisant HCl, à la suite de flottation conventionnelle (amyl xanthate, la cendre de soude et de MIBC) a donné des résultats nettement améliorés au cours des minerais non traités. Utiliser H2SO4, sans doute l'option la pratique conduit à de flottaison sans collecteur due à la formation du soufre élémentaire sur la pentlandite, et sans buse due à des solutions à haute force ionique. Amélioration de qualité Ni-reprise avec le rejet supérieur de MgO de a été atteint. Les changements structurels dans les fibres ont été suivis en utilisant diverses techniques de spectroscopie et d'un mécanisme de désintégration de fibre suggéré.
356

Processing and properties of C-Si-Mn trip steels

Di Chiro, Andrew. January 1997 (has links)
In the processing of steels, various types of alloy compositions and heat treatments have been used to improve strength and ductility. Unfortunately, these methods are usually accompanied by a decrease in formability. It has been well recognized that the presence of retained austenite, in microstructures which include ferrite and bainite, can significantly strengthen the steel and improve ductility by transforming to martensite under an applied stress or strain. This is the basic principal behind the TRIP (transformation-induced plasticity) effect. / In this work, the effects of thermomechanical processing (TMP) and chemical composition on the structure and properties of C-Si-Mn TRIP steels were investigated. It was found that the addition of Nb to these steels not only increases the volume fraction of retained austenite, but also improves the total elongation and tensile properties. It was also revealed that the combination of strength and ductility is further optimised by varying the C content in the steel. For C-Si-Mn Nb-bearing TRIP steels, the bainite transformation conditions are the critical parameters in dictating the final mechanical properties. / The effects of retained austenite characteristics on the mechanical properties were examined. Although the retained austenite volume fraction is indeed a key factor in controlling the final properties, there are other parameters that must be considered, such as the morphology, particle size, solute enrichment and the mechanical stability of the retained austentite. In this work, the approach involved a systematic investigation of the effects of TMP parameters on the state of the retained austenite characteristics and finally, an evaluation of the final mechanical properties. It was revealed that, for a given ferrite/bainite structure, the tensile strength and total elongation are controlled by the volume fraction and the mechanical stability of the retained austenite. Increasing the mechanical stability of retained austenite leads to transformation at higher strains. (Abstract shortened by UMI.)
357

Low temperature oxidation of used lubricating oil

Di Lalla, Sergio. January 1997 (has links)
In order to deal with the negative impacts associated with disposal of used oils by thermal remediation, a study of the material under combustion-like conditions was undertaken. Two used motor oils were subjected to slow heating using a Thermogravimetric Analyzer coupled with a Fourier Transform Infrared Spectrometer. Based on the results obtained, mechanisms of the general transformation process the oil undergoes and the evolution of the solid particles were proposed. The presence of Polycyclic Aromatic Hydrocarbons (PAHs), considered hazardous, was observed and individual PAHs were identified. The results show that initial oxygen content in the oil plays a significant role in the thermal remediation process, primarily leading to smaller, more compact final residues. This may have significant implications In terms of leachability of toxic metals. The insight gained here can be utilized in further studies to understand and then possibly control, the process in practical combustion systems.
358

The effect of zinc stearate on the compaction and sintering characteristics of a Ti-6%A1-4%V hydride-dehydride powder /

Ederer, Leslie. January 1999 (has links)
Powder metallurgy (P/M) processing has become an important technique replacing many casting applications, especially for the fabrication of refractory metals where very high melting temperatures are required. Improvement in powder production, cleanliness and characterization techniques, combined with an increased understanding of basic compaction and sintering principles and a need for metals with high strength to weight ratios has led to an increased interest in titanium powder utilization. P/M techniques for Ti-6Al-4V powder can enable the production of high quality parts at lower processing temperatures and cost. For most applications prealloyed powder produced by the hydride-dehydride process (HDH) is used, due to the lower cost of this powder as compared to Ti-6Al-4V powder produced by other methods. / General characterization of a Ti-6Al-4V HDH powder and the effects of using a zinc stearate on the green and sintered density were examined at different compaction pressures and sintering temperatures. (Abstract shortened by UMI.)
359

Quantification of the reduced pressure test

La-Orchan, Wittaya January 1994 (has links)
The concentration of hydrogen is one of the most important parameters in liquid aluminum processing because it is responsible for gas porosity which affects casing quality, ie. pressure tightness, mechanical properties etc. In order to gain optimum quality, the amount of hydrogen dissolved in liquid aluminum must be known prior to casting. This has led to the development of several techniques to quantify hydrogen in liquid aluminum. Among these is the Reduced Pressure Test (RPT). The RPT is simple, very inexpensive and commonly used in aluminum foundries to obtain a qualitative evaluation of the melt hydrogen level. / In this thesis the development of the RPT to a truly quantitative level is discussed. This includes redesigning of the steel mold and the application of a riser. The mold was redesigned to improve the test sensitivity while a CO$ sb2$-bonded sand riser was applied in order to eliminate volumetric shrinkage and ensure a constant volume sample. As the sample has a constant volume, either the sample weight or density can be used to quantify the hydrogen content. The simplest technique is to use the sample weight. / Several parameters that affect the test sensitivity and reproducibility were studied, such as chamber pressure, amount of inclusions, pouring temperature, and mold temperature. It was found that there are two important parameters that strongly affect the test; chamber pressure and amount of inclusions. The lower the chamber pressure the better the test sensitivity but the poorer the test reproducibility. Increasing the amount of inclusions improves the test sensitivity. / The constant volume sample can be used to predict the amount of hydrogen in the melt for various types of alloys including 319, 356, 357 and 413 within a reasonable margin of error. The error as measured by this technique was found to be in the range of $ pm$0.025-0.049 ml./100 g.Al. if the sample weight is used, and in the range of $ pm$0.025-0.047 ml./100 g,Al. if the sample density is used. / A simple mathematical model based on a mass balance approach was developed to calculate pore size and sample density. The model predicts the density accurately for various types of alloys and different melt treatments.
360

Thermal analysis of aluminum foundry alloys by a novel heat pipe probe

Meratian Isfahani, Mahmood January 1995 (has links)
A new application of heat pipes is introduced. The present research deals with the development of a heat pipe for the on-line quality control of liquid aluminum silicon foundry alloys. / Thermal analysis is a technique whereby a small quantity of a melt is allowed to solidify while its cooling curve is recorded. Analysis of the cooling curve with standard mathematical algorithms allows one to determine a number of useful parameters that characterize the liquid and solid states of the material. In aluminum-silicon casting alloys thermal analysis is often used to assess the grain size and degree of eutectic modification of the alloy before pouring. / A novel probe has been developed for conducting thermal analysis of aluminum alloy melts. The probe, which resides in the melt, need not be withdrawn as it solidifies a small sample (i.e. button) at a predetermined cooling rate. Once the cooling curve results have been acquired, the probe can be instructed to remelt the frozen button and await instructions for analyzing a fresh sample. / The operating principle of this novel device is based on heat pipe technology. In simple terms, a heat pipe consists of a condenser and an evaporator which contain a relatively small quantity of working substance fluid. As heat is absorbed by the evaporator, the liquid phase of the working substance is vaporized and subsequently condensed on the condenser walls from which heat is extracted. / It has been shown that the designed probe, which is classified as a gas loaded annular thermosyphon, is completely workable in the range of conditions typically encountered in the thermal analysis of aluminum alloys. The thermal analysis results obtained with this new technique are in a good agreement with those of conventional thermal analysis. In addition, the new method is applicable to a wider range of operating conditions and is easier to use. Based on the semi-continuous nature of the new method, it does not need pre-preparation (materials, labour, pre-heating, thermocouple installation for each test, isolation of the sampling cup, etc.) to start thermal analysis. Also, from a cooling rate point of view, the system is well controllable. Moreover, it is shown that the probe is simple in construction, easy to use, and intelligent enough to provide semi-continuous thermal analysis. There are no consumable materials and moving parts. / Thermal analysis results are reported for pure aluminum, hypoeutectic aluminum silicon (356) and eutectic aluminum silicon (413) casting alloys. Agreement in the results between the new and conventional systems is shown to be excellent. Finally, a heat transfer/solidification model of the heat pipe thermal analysis probe is derived and validated.

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