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Tsiagbe, Walter Yao. "Relaxation of weld residual stresses by post-weld heat treatment." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385842.
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King, Benjamin. "Welding and post weld heat treatment of 2.25%Cr-1%Mo steel." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060404.095844/index.html.
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Hodgson, David K. "The Post Weld Heat Treatment Response in the Heat Affected Zone of 2.25Cr-1Mo Steel." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1367416587.
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Walker, Jacob D. "Heat Transfer Analysis of Localized Heat-Treatment for Grade 91 Steel." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6045.
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Many of the projects utilizing Grade 91 steel are large in scale, therefore it is necessary to assemble on site. The assembly of the major pieces often requires welding in the assembly; welding drastically changes the superior mechanical properties of Grade 91 steel that it was specifically developed for. Therefore, because of the adverse effects of welding on the mechanical properties of Grade 91, it is necessary to do a localized post weld heat treatment.
In this study a localized post weld heat treatment is used to gather experimental data. The data is then used to derive unknown heat transfer coefficients that are necessary for theoretically modeling heat treatments. With the derived coefficients that have been found one can theoretically model heat treatment scenarios specific to the situations and provide results that are reliable and provide insight as to what parameters will provide the best results.
This research is very beneficial to the joining of metals industry because it provides a way to ensure the method used to heat treat the welded section is being properly done, and the required heat treatment is achieved. It is applicable to many different geometries so that it can be modified to specific situations.
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Champagne, Matthew. "Investigation of 2195 and 2219 Post Weld Heat Treatments for Additive Friction Stir Lap Welds." ScholarWorks@UNO, 2017. https://scholarworks.uno.edu/td/2402.
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To evaluate potential uses for friction stir welding in additive manufacturing, two separate parts were fabricated, one of 2195-T84 and the other 2219-T87, utilizing fixed pin techniques and additive lap welds. The parts were cut into samples, artificially aged and subjected to Rockwell hardness (HRB), Vickers hardness, micrographic photography, and metallographic imaging on both pre- and post- heat treatment. Additionally, tensile testing was performed on the heat-treated samples. A comparisons of test results showed a minimal increase in the yield strength of the 2195-T84 samples compared to as-welded tensile results obtained from a previous project. The ultimate tensile strength was reduced by approximately 16%. Further testing will be required to determine the nature of this reduction. No previous results were available for the as-welded 2219-T87, but UTS of the artificially aged samples was approximately 91% that of the parent material.
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Ohlsson, Jonas. "Effects of different heat treatments on hardness of Grade 91 steel." Thesis, Karlstads universitet, Avdelningen för maskin- och materialteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-32805.
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CCI Valve Technology AB is a company located in Säffle, Sweden, that manufactures and installs bypass valves. Due to requirements outside normal standards on the valve's hardness values, some measurements have had difficulties meeting such requirements. During this thesis work, tests were carried out to determine how to overcome the difficulties. The experiments focused on five different areas that may affect the components hardness, welding method, soaking temperature during post weld heat treatment, measuring procedure, component thickness and number of heat treatment cycles. The Grade 91 steel specimens that were examined consisted of five solid cylinders and three various pipes that were welded together by using shielded metal arc welding (SMAW) or gas tungsten arc welding (GTAW). Each pipe was sawed apart into three equal parts. All specimens were hardness tested and eight of the specimens' microstructure was studied with an optical microscope. The hardness measurement instruments used, LECO V-100-C2 and GE-MIC 10, are Vickers hardness testers, one stationary and the other one portable. The measuring results contain a vast number of different hardness measurement data. From the analyzed data, the conclusions were drawn that the most suitable soaking temperature during post weld heat treatment were 750° C, that the SMAW method creates a more stable hardness profile than the GTAW method, and that one heat treatment cycle is more beneficial than two or more.
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Norton, Seth Jason. "Development of a gleeble based test for post weld heat treatment cracking in nickel alloys /." Connect to resource, 2002. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1057177289.
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Norton, Seth J. "Development of a gleeble based test for post weld heat treatment cracking in nickel alloys." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1057177289.
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Berglund, Daniel. "Validation of models for welding and post weld heat treatment in product development of aerospace components /." Luleå, 2003. http://epubl.luth.se/1402-1544/2003/33.
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Widener, Christian Aragon Talia George E. "Evaluation of post-weld heat treatments for corrosion protection in friction stir welded 2024 and 7075 aluminum alloys." Diss., Click here for available full-text of this thesis, 2005. http://library.wichita.edu/digitallibrary/etd/2005/d004.pdf.
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Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering."December 2005." Title from PDF title page (viewed on February 8, 2007). Thesis adviser: George Talia. Includes bibliographic references leaves 192-203).
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Ballat-Durand, Dorick. "Microstructural characterization and optimization of linear friction welded titanium alloys joints through the influence of the process parameters and post-weld heat treatments." Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2499.
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Cette étude s’inscrit dans une démarche de réduction des coûts dus à l’utilisation croissante d’alliages de titane pour des applications structurelles, via des procédés d’assemblage à l’état solide, comme le soudage par friction linéaire (LFW). Cependant, les chargements thermomécaniques transmis au matériau au cours du LFW engendrent d’importantes transformations microstructurales pouvant affecter sévèrement la durabilité mécanique de l’assemblage. Ces transformations sont dépendantes à la fois de l’histoire thermomécanique du matériau et de ses éléments d’alliage. Ainsi, la compréhension des mécanismes régissant ces transformations en lien avec l’impact des configurations procédé et/ou de traitements thermiques sur ces dernières apparaît comme nécessaire pour des applications industrielles. Les travaux présentés dans ce document se focalisent sur la caractérisation/optimisation microstructurale de deux joints obtenus à partir de deux alliages sensiblement différents : le β-métastable Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti17) et le quasi-α Ti-6Al-2Sn-4Zr-2Mo (Ti6242). Une analyse détaillée des mécanismes impactant les transformations microstructurales et la résorption des défauts sera exposée en s’appuyant sur des études multi-techniques et multi-échelle. Ces campagnes expérimentales ont conduit à l’élaboration d’un traitement thermique permettant d’obtenir des comportements mécaniques quasi-homogènes au sein des structures soudées. De plus, les effets des principaux paramètres de LFW sur les microstructures ont été déterminés fournissant ainsi à la littérature des données essentielles pour la dissipation des défauts et le contrôle des textures de déformationThe present study follows up two major development axes focusing on the increase in use of Ti-alloys for structur applications through the use of solid-state joining processes such as Linear Friction Welding (LFW). Yet, the therm mechanical loads involved during LFW result in remarkable microstructural changes deeply affecting the associate mechanical performances. These changes are concomitant with the thermo-mechanical processing history and the alloyin compositions of the welded Ti-alloys. Hence, a correct understanding of the microstructure transformation mechanism induced by LFW is required as well as identifying the influence of the process conditions and/or complementary he treatments on these changes. This dissertation is endeavored at characterizing and optimizing the microstructures of two butt-joints of significantl different Ti-alloys: the ß-metastable Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti17) and the near-α Ti-6Al-2Sn-4Zr-2Mo (Ti6242). The extensive microstructural investigations will focus on identifying the mechanisms responsible for transforming the microstructures and for the formation/resorption of welding defects. These investigations will combine temperatur measurements, micrographs, crystallographic/chemical analysis, hardness/tensile tests. The resulting comprehension the microstructural changes will enable designing a heat treatment capable of a quasi-homogenization of the tensil behavior across the assemblies. Moreover, identifying the effects of the main process parameters on the microstructur will provide the literature with valuable insights on tailoring the process duration, the recrystallization/textur development, and the defect removal
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Kimpton, Claire Michelle. "Effects of post weld heat treatments on the fatigue of the inertia welded nickel based superalloy RR1000 at high temperatures." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1326/.
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To improve the efficiency of turbine aero engines, higher operating temperatures and weight savings are being investigated. Alloys such as RR1000 are being trialled as they perform better at higher temperatures than current nickel-based superalloys. To achieve weight savings, inertia welding is being trialled for turbine discs but current post weld heat treatments reduce fatigue life. In this investigation, a number of novel post weld heat treatments were trialled aimed at improving post weld microstructure and fatigue properties. Extensive microstructural characterisation and mechanical testing were used to assess the effect of these treatments on both parent and weld materials. Post weld heat treatment (PWHT) was found to have a great effect on the size and distribution of γ' and carbides, particularly when a PWHT temperature of 980ºC or above was used. The effect of this microstructural change on the hardness of the weld and parent material has also been characterised. Extensive total life fatigue testing was carried out at 650ºC. It was found that failure can occur in both the parent and weld material, although it is deduced that the yield stress of the weld needs to be surpassed to see weld failure (plasticity in the weld). Increasing dwell time at peak load reduced the life of these components. Two mechanisms for crack growth were observed with initiation either at the surface or at a large Hf rich particle subsurface. Oxidation was found to have a large effect on both initiation and growth of fatigue cracks. By introducing a sharp pre-fatigue crack into samples, static load testing was used to determine a threshold value of K (stress intensity factor) for growth and growth rates were plotted at different K values. It was seen in these tests that PWHT had a large effect on growth rates and threshold values of K.
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Ren, Yao. "Investigation of residual stresses in X65 narrow-gap pipe girth welds." Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/16658.
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This research investigated the residual stresses in narrow-gap API 5L X65 pipe girth welds in as-welded and after post weld heat treatment (PWHT) conditions. The PWHT included global furnace and local practices. Non-destructive neutron diffraction (ND) strain scanning was carried out on selected pipe spools and strainfree reference samples for the determination of the lattice spacing before and after PWHT. The as-welded and post-heat treatment residual stresses measured in the pipe spools were examined and compared. Experimental work also included full residual stress mapping in the weldment and through-thickness measurement at weld centre and close to the external and internal pipe surfaces. The measured profiles were compared with the recommendations given in British flaw assessment procedure BS 7910 "Guide to methods for assessing the acceptability of flaws in metallic structures" and the UK nuclear industry's R6 procedure. The design, preparation and experimental neutron diffraction measurement procedures for the determination of the strain-free lattice parameter in various configurations of reference samples and in the required directions were discussed. The variability of the lattice spacing in the reference samples was found depended on the specimen manufacture methods and thermal process. Welding residual stresses were also simulated using finite element analysis (FEA) modelling approach. The simulated thermal cycles and transient strains at specific locations were compared with the experimental readings. The residual stress profiles derived from finite element model were compared with the measurements from neutron diffraction. It was found, the measured and simulated, as-welded - residual stress profiles showed good consistency in terms of stress distribution and magnitude to reasonable extent. Measurement results also indicated that local PWHT was effective in reducing the residual stresses in the pipes to a level similar to that achieved by a global approach.
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Teixeira, Marcos Antônio. "Avaliação de propriedades mecânicas e caracterização microestrutural de juntas soldadas do aço ASTM 335 grau P91 submetidas a diversas condições ao tratamento térmico de alívio de tensões." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-15032018-121705/.
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Os aços Grau 91 vêm sendo amplamente utilizados como componentes para trabalhar em elevadas temperaturas nas indústrias de geração de energia, petroquímica e refinarias de petróleo em consequência da sua excelente resistência a fluência e corrosão em altas temperaturas. Apesar destas notáveis propriedades têm sido encontradas dificuldades na soldagem do aço Grau 91, visto que pode apresentar valores de dureza fora dos limites especificados e provocando redução de diversas propriedades mecânicas. Foram confeccionadas juntas tubulares do aço Grau 91, por meio de soldagem usando o processo TIG na raiz e o processo Eletrodo Revestido nas camadas de soldagem subsequentes. As juntas soldadas foram submetidas ao tratamento térmico póssoldagem (TTPS) a 760°C com diferentes tempos de patamar (1h, 4h e 8h) e posteriormente, as propriedades mecânicas foram analisadas para verificar o atendimento aos requisitos normativos, por meio da realização de ensaios de tração convencional e à quente (540°C), impacto Charpy, dureza Vickers e caracterização microestrutural. Os resultados mostraram que as propriedades mecânicas do aço Grau 91 sofreram alterações, como uma melhor resistência ao impacto e diminuição da dureza com o aumento do tempo de patamar de temperatura, indicando que é possível obter uma melhor combinação de resistência mecânica e tenacidade com o tempo de patamar maior do que 4 horas no TTPS nas condições utilizadas.Grade 91 steels have been widely used as components to work at high temperatures in power generation plants, petrochemicals and oil refineries as a result of their excellent creep and corrosion resistance at high temperatures. Despite these remarkable properties, difficulties in welding Grade 91 have been encountered, as they may exhibit hardness values outside the specified limits and cause a reduction in various mechanical properties. Grade 91 tubular joints were made through welding by using the GTAW process at the root and the SMAW process in the subsequent welding layers. The welded joints were subjected to PWHT at 760°C with different tempering times (1h, 4h and 8h) and their mechanical properties were evaluated by performing conventional tensile, elevated-temperature tensile (540°C), Charpy V-notch impact toughness, Vickers hardness testing and microstructural characterization. Results indicated that mechanical properties of grade 91 steel change with increasing tempering time, and a better combination of strength and toughness can be reached with more than 4 hours of PWHT, under certain conditions.
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Ferrari, Marcello. "Soldagem de chapas grossas em aço baixa liga temperado e revenido ASTM A514 com aço carbono ASTM A36 pelo processo arame tubular." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-31032017-141554/.
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Neste trabalho foram determinadas as condições para a soldagem de chapas grossas de aço carbono ASTM A36 com aço baixo-liga temperado e revenido ASTM A514 Grau Q empregando-se o processo arame tubular. Para tanto foram soldadas diversas peças de testes com o intuito de se avaliar as condições mais adequadas de preparação e soldagem de juntas dissimilares destes materiais. A preparação foi realizada por meio de corte térmico. A temperatura de preaquecimento foi determinada através de modelos matemáticos, pelas recomendações das normas AWS D1.1 e DIN EN 1011-2 sendo posteriormente avaliada por intermédio do teste de soldabilidade tipo CTS Controlled Thermal Severity. Os parâmetros de soldagem foram determinados a partir da qualificação de um procedimento de soldagem, conforme a norma AWS D1.1. Foram avaliadas as consequências do emprego do tratamento térmico de alívio de tensões após soldagem (TTAT), pelos testes de dureza Vickers e impacto Charpy. A caracterização microestrutural foi realizada por meio de microscopia óptica e microscopia eletrônica de varredura. A caracterização das superfícies oxicortadas evidenciou os efeitos da descarbonetação e também da carbonetação. A temperatura de pré-aquecimento de 160°C determinada por meio da metodologia recomendada pelas normas AWS D1.1 e DIN EN 1011-2 mostrou-se satisfatória nos testes de soldabilidade. Foi possível a qualificação do procedimento de soldagem (EPS) com requisitos de impacto na condição \"como soldado\", porém na condição \"após TTAT\", os baixos valores de tenacidade obtidos no metal de solda, inferiores a 27J, não permitiram a qualificação de uma EPS com requisitos de impacto. Foi observada a ausência de trincas intergranulares tanto na zona afetada pelo calor quanto no metal de base ASTM A514, porém foi revelada a presença de microfases frágeis no metal de solda na condição \"como soldado\", especificamente na região da raiz, intensificadas pelo efeito da diluição. O aumento do teor de carbono na raiz, a presença de microfases frágeis, a grande fração de grãos colunares e de ferrita proeutetóide combinados com a baixa fração de ferrita acicular no metal de solda contribuíram para os baixos valores de tenacidade encontrados na condição \"como soldado\". Após o TTAT observou-se uma queda acentuada da tenacidade, inferior a 27J, do metal de solda devido à fragilização provocada pela precipitação e coalescimento de carbonetos de ferro.In this work it was determined the conditions for welding thick plate of ASTM A36 carbon steel with quenched and tempered low-alloy steel ASTM A514 Grade Q employing the Flux Cored Arc Welding (FCAW) process. For that several coupons of tests were welded in order to evaluate the most appropriate conditions for preparation and welding of these dissimilar materials. The preparation was carried out by means of thermal cutting. The preheat temperature was determined by mathematical models, the recommendations of standards AWS D1.1 and DIN EN 1011-2 being further evaluated using the CTS type weldability test - Controlled Thermal Severity. The welding parameters were determined by qualifying a welding procedure (WPS), according to AWS D1.1. The effects of post weld heat treatment (PWHT) were evaluated by Vickers hardness tests and Charpy. Microstructural characterization was performed by optical microscopy and scanning electron microscopy. The characterization of oxi-fuel cut surfaces showed the effects of decarburization and also carburization. The preheating temperature of 160 °C determined by calculation and the methodology recommended by the standards was satisfactory in weldability tests. It was possible qualification of welding procedure (WPS) with impact requirements in the condition \"as welded\" but the condition \"after PWHT\" low toughness values obtained in the weld metal, less than 27J, did not allow to qualify a WPS with toughness requirements. The absence of intergranular cracking was observed in both the heat affected zone as the base metal ASTM A514, but the presence of fragile microphase in the weld metal was revealed in the weld metal in the condition \"as welded\" specifically in the root region, intensified by the effect of dilution. The carbon increase at root, the presence of fragile microphase, the large fraction of columnar grains and proeutectoid ferrite combined with the low fraction of acicular ferrite in the weld metal contributed to the low toughness values found in the condition \"as welded \". After PWHT there was a sharp drop in toughness, less than 27J, in the weld metal due to embrittlement caused by precipitation and coarsening of iron carbides.
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Olsson, Erika, and Jenny Abrahamsson. "Utökade krav för svetsade stålkonstruktioner vid efterbehandling av svetsar." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-85968.
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Stålindustrin står för 7 % av världens koldioxidutsläpp. För att minska industrins miljöpåverkan är ett alternativ att introducera konstruktioner i höghållfasta stål eftersom det ger möjlighet till slankare konstruktioner och därmed mindre materialåtgång. Användning av höghållfasta stål i svetsade konstruktioner kan dock vara problematiskt då de utsätts för utmattningslaster vilket kan leda till oanade brott i konstruktionen. För att förbättra svetsade konstruktioner mot utmattning kan PWT tillämpas.I arbetet undersöktes möjligheterna till implementering av PWT i tillverkningsstadiet samt eventuella hinder till varför metoden inte används. För att bilda en uppfattning om möjligheten till alternativa metoder för att öka utmattningshållfastheten för en svets har gällande myndighetskrav samt normer för utförande av vanliga svetsar undersökts. Genom intervjuer har åsikter från olika aktörer inhämtats för att besvara frågeställningarna.Efter genomförd undersökning konstaterades att den bristande förmågan att kontrollera spänningar i en svets är en bidragande faktor till varför PWT i dagsläget inte används i tillverkningsstadiet inom byggbranschen. Intervjun med Trafikverket resulterade i alternativet att ta fram en särskild kravspecifikation enligt Krav Brobyggande, som vid godkännande skapar möjlighet för implementering av PWT. Krav Brobyggande är Trafikverkets dokument men krav och råd för brobyggande i Sverige.The steel industry stands for 7 % of the worlds emission of carbon dioxide. An alternative to reduce the environmental impact of the industry is to introduce structures of high strength steel since it provides opportunity for slimmer structures and thereby less material consumption. However, the use of high strength steel in welded structures can be problematic when exposed to fatigue loads, which can lead to unsuspected breaks in the structure. To improve welded structures against fatigue PWT can be implemented.The possibilities for implementation of PWT during manufacturing and possible obstacles as to why it should not be used was investigated in this thesis. To form a perception for the possibilities of alternative welding methods to increase fatigue strength the existing regulations and norms of execution for as welded conditions was examined. Opinions from different participants in the construction process were interviewed to answer the questions at issue.The lacking ability to verify stress in a weld was concluded to be a contributing factor as to why PWT is not currently used during the manufacturing process in the construction industry. The interview with Trafikverket resulted in the alternative to create a specific requirement specification according to demands in Krav Brobyggande. Approval of the specific requirement specification could lead to possibility to implement PWT in the construction industry. Krav Brobyggande is Trafikverkets document with demands and advice for bridge construction in Sweden.
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Barlow, D. "Stress relief cracking in A533B and A508C1 2 pressure vessel steels." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233221.
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Crook, Nolan Tracy. "Control of Post-Weld Fracture Toughness in Friction Stir Processed X-80 HSLA Steel." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9162.
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The present study investigates the fracture toughness of FSW X-80 HSLA steel welds. Weld cooling rate and peak temperature were varied among welds; indirectly manipulated through FSW travel speed, rpm, and weld preheat. Fracture toughness was tested according to ASTM 1820 standard along the weld centerline using surface-notched SEB specimen cooled to -40 °C. This study resulted in a reliable, repeatable process for generating friction stir welds with CTOD’s consistently above that of the original base metal. CTOD and microstructure of friction stir welds can be selected by controlling weld cooling rate and peak temperature. Material properties and microstructure similar to the original base metal can be recreated throughout the weld stir zone. CTOD of FSW X80 has a strong inverse linear correlation with post-weld cooling rate.
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Yan, Pei. "High frequency induction welding & post-welding heat treatment of steel pipes." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609702.
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Su, Lan. "Effects of post-harvest treatment and heat stress on the antioxidant properties of wheat." College Park, Md.: University of Maryland, 2006. http://hdl.handle.net/1903/3864.
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Thesis (M.S.) -- University of Maryland, College Park, 2006.Thesis research directed by: Dept. of Nutrition and Food Science. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Abdelaal, Maged Mohamed Elsayed. "Effect of post- processing heat treatment on flexural strength of zirconia for dental applications." Thesis, University of Iowa, 2016. https://ir.uiowa.edu/etd/3031.
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Purpose: the purpose of this study was to evaluate the effect of annealing heat treatment on biaxial flexural strength and reliability of 3Y-TZP, sintered at various temperatures.
Materials & methods: 3Y-TZP blanks were pre-sintered at 850°C for 2 hours and sliced into discs (20x1.2mm). Specimens were randomly assigned to 5 groups and subsequently sintered at various temperatures ranging from 1350°C to 1650°C for 2 hours. For each sintering temperature, specimens were divided into three treatment groups. One group (n=20) was left as-sintered as control. One group was air-abraded with 50 micron aluminum oxide powder (n=20). The last group was air-abraded and heat-treated at 1250°C for 20 minutes (n=20). In addition, polished specimens (n=5 per sintering temperature) were prepared to study microstructure, grain size and indentation crack patterns. The mean density was measured by helium pycnometry. The percent porosity was calculated from measured and theoretical density. The mean grain size was determined by the linear intercept method on atomic force micrographs. Crystalline phases were analyzed by x-ray diffraction (XRD). Biaxial flexural strength (BFS) was tested according to ISO standard 6872 using a Universal Testing Machine. Polished specimens were thermally etched, gold coated and Vickers indentations were produced under a 98N load. Indentation crack patterns were analyzed by Scanning Electron Microscopy (SEM) on digital images. The length ratio of trans-granular to inter-granular fracture was determined. Results were analyzed by Kruskal-Wallis test and Turkey's adjustment for multiple comparisons. A 0.05 level of segnificance was used. Reliability was evaluated by weibull analysis.
Results: There was an inverse relationship between density and sintering temperature Spearman rank correlation r = -0.982, p<0.0001). Statistically significant differences were found between all the groups (p<0.0001, exact Kruskal-Wallis test). There was strong evidence of an increase in the percentage of porosity with increasing sintering temperature Spearman rank correlation r=1.00, exact p = 0.017). The mean real grain size increased with sintering temperature. Analysis of XRD data showed that the monoclinic phase as well as ferro-elastic domain switching were present for all air-abraded groups. A small amount of monoclinic phase was also present in groups sintered at 1600°C and 1650°C. In The mean BFS was higher for all air-abraded groups compared to as-sintered or air abraded and heat-treated groups. Air-abraded groups sintered at 1350, 1450, 1550, and 1600°C showed the highest mean BFS (1552.97±200.85, 1502.29±102.36, 1391.4±108.3, 1258.5±114.8 MPa), respectively. The highest Weibull moduli (reliability) were obtained with the heat-treated group sintered at 1550°C (19.8), air-abraded group sintered at 1450°C (17.6) and heat-treated group sintered at 1350°C (15.4). The group sintered at 1650°C was the least reliable, independently of treatment state. Based on the data analysis of both the biaxial flexural strength and Weibull modulus, it was found that, the optimal treatment combination was obtained for the air-abraded group sintered at 1450°C, followed by the air-abraded group sintered at 1550°C. Crack patterns analyses showed that the proportion of trans-granular fracture increased with sintering temperature.
Conclusions: Annealing heat treatment is not recommended after any adjustments, as it does not improve the reliability of the material. Crack patterns and flexural strength are strongly influenced by the crystalline phase composition of the material. Sintering at 1600°C and 1650°C is not recommended due to the corresponding decrease in mechanical properties independently of treatment. Air-abrasion of zirconia sintered at 1450°C or 1550°C led to the best combination of high strength and reliability.
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Ervin, Jennifer Kelly. "Post Heat Treatment Effects of Ti-6Al-4V Produced via Solid Freeform Electron Beam Melting." NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-05012008-105845/.
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Traditionally, Ti-6Al-4V components are fabricated by forging or casting. However, these methods of production require expensive dies or molds. The cost per part is very high for those parts produced in low quantities. The solid freeform electron beam melting process aims to produce high dimensional tolerance parts with similar mechanical properties at a lower cost by melting Ti-6Al-4V powder in a layer by layer fashion using high energy electrons. Due to the directional solidification effects, the microstructure seen in this process consists of a columnar grain structure along the growth direction and an equiaxed structure at the cross-sectional growth plane. This type of structure is thought to contribute to the anisotropy of tensile properties discovered in previous research. Although, preferred orientation of the α laths may play a role as well. Heat treatments above the β transus are performed in order to improve the tensile properties, specifically ductility, with intensions to remove preferred orientation and to disunite the columnar grain structure. Tensile testing, fractography, optical microscopy, and x-ray diffraction are used to characterize and compare the as-processed and β heat treated electron beam melted specimens. It is found for all β treated conditions, the ductility increases compared to the as-processed specimens, although the strength decreases. The mode of fracture changes from ductile dimple rupture in the asprocessed condition to transgranular cleavage with ductile dimple rupture for the heat treated specimens. The macrostructure and microstructure in the as-processed and heat treated specimens contrasted greatly. The macrostructure changes from a fully columnar structure to a mixture of columnar and equiaxed grains. A fine acicular microstructure is observed in the as-processed samples, whereas a broad lamellar colony microstructure is formed during heat treatment. The presence of a colony microstructure is a possible reason for the improvement in ductility. From the x-ray data obtained, the preferred orientation is not reduced but instead increases after heat treating in the β region which likely is a result of the favorable rearrangement of slip systems due to the change in α lath orientation.
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Ibrahim, Hamdy Ibrahim. "Bioresorbable Magnesium-Based Bone Fixation Hardware: Alloy Design, Post-Fabrication Heat Treatment, Coating, and Modeling." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1503678544356525.
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Petersson, Viktor, and Johan Gustafsson. "Beräkningsmetoder för verifiering av svetsar med inriktning på PWT." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-85760.
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Stål är ett material som används i olika byggnadskonstruktioner. I de byggnadskonstruktioner som utsätts för upprepade belastningar kan utmattning ske i materialet. Utmattning leder till permanenta skador i form av sprickbildning och slutligen brott. I svetsade konstruktioner är det ofta svetsar som har den lägsta utmattningsstyrkan. För att förbättra en svets utmattningsstyrka finns efterbehandlingsmetoder som benämns Post Weld Treatment (PWT). Idag används den beräkningsmetod som är föreskriven i Eurokod vid verifiering av svetsar. Beräkningsmetoden är förenklad och kan underskatta objektets livslängd med hänsyn till utmattning. Syftet med arbetet är att studera olika dimensioneringsmetoder som behandlar utmattningsbelastade svetsar samt hur tillämpning av PWT kan förbättra en typsvets livslängd. Målet med arbetet är att studera en typsvets och visa skillnaden i antalet lastcykler mellan beräkningsmetoderna samt hur många lastcykler samma typsvets förväntas öka med PWT. Teorin och resultaten utgår från vetenskapliga artiklar, litteraturstudier och enfallstudie som behandlar både en genomsvetsad stumsvets samt en kälsvets lokaliserade på en I-balk. Resultatet pekar mot att den metod som används idag underskattar livslängden och att PWT kan markant kan förbättra en svetsutmattningsstyrka.Steel is a material used in various building structures. Fatigue can occur in the material if building structures is exposed for repeated loads. Fatigue leads to permanent damages such as crack initiations and fracture. It is common that welds in welded structures have the lowest fatigue strength. A welds fatigue strength can be improved with treatments termed Post Weld Treatment (PWT). Today a welds fatigue strength is verified with a method described in Eurocode. The calculation method is simplified which can underestimate the objects number of lifecycles regarding fatigue. The purpose with this essay is to study different structural design methods for fatigue exposed welds and how many lifecycles a typeweld will increase when applying PWT. The goal with this essay is to study a typeweld and calculate the number of lifecycles between the calculation methods and to show how many lifecycles the same type weld will increase when applying PWT. The results and theory are based on scientific articles, literature studies and a casestudy which both contains a through welded butt weld and a fillet weld placed on an I-beam. The results points at that the calculation method that is used today underestimates the number of lifecycles and that the number of lifecycles increased significant after PWT.
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Carlson, Mark. "Post-Exercise Responses During Treatment Delays do not Affect the Physiological Responses to Cooling in Cold Water in Hyperthermic Individuals." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24392.
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Victims of exertional heat stroke (EHS) in whom treatment is delayed have higher rates of multi-organ failure and a greater number of fatalities. Death related to EHS is preventable, through immediate treatment via cold-water immersion (CWI). To date little is known about the influence of treatment delays on core cooling following EHS. Thus we sought to examine the effects of treatment delays on cardiovascular and thermal responses prior to, during, and following CWI treatment in individuals with exercise-induced hyperthermia.
Our findings demonstrate that treatment delays resulted in a sustained level of hyperthermia and cardiovascular strain that significantly increased the time an individual is at risk to the potential lethal effects of EHS. Moreover, we report that cold water immersion treatment is powerful enough to overcome the adverse effects of treatment delays and rapidly reduce core temperatures while facilitating the re-establishment of blood pressure towards normal resting levels.
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Goel, Sneha. "Post-treatment of Alloy 718 produced by electron beam melting." Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-13547.
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Electron beam melting (EBM), a metal additive manufacturing (AM) process, has received considerable industrial attention for near net shape manufacture of complex geometries with traditionally difficult-to-machine materials. This has fuelled considerable academic interest in investigating EBM of Alloy 718, a nickel ironbased superalloy possessing an exciting combination of good mechanical behaviour and cost effectiveness. EBM production of Alloy 718 is particularly promising for aerospace and other sectors which value rapid production of components with large scope for design flexibility. The EBM builds are characterized by presence of inevitable defects and, anisotropy within a build is also a concern. Consequently, as-built Alloy 718 has to be subjected to post-build thermal-treatments (post-treatments) to ensure that the parts eventually meet the critical service requirements. Not withstanding the above, limited knowledge is available about optimal post-treatments for EBM-built Alloy 718. Therefore, the main focus of the work presented in this thesis was to systematically investigate the response of EBM-built material to post-treatments, which include hotisostatic pressing (HIPing), solution treatment (ST), and aging. HIPing of EBM-built Alloy 718 led to more than an order of magnitude reduction in defect content, which was reduced from as high as 17% to < 0.2% in samples built with intentionally introduced porosity to investigate limits of defect closure achievable through HIPing. In addition, HIPing also caused complete dissolution of δ and γ" phases present in the as-built condition, with the latter causing dropin hardness of the material. HIPing had no effect on the carbides and inclusions such as TiN, Al2O3 present in the built material. The evolution of microstructure during ST and aging was systematically investigated. Growth of potentially beneficial grain boundary δ phase precipitates was found to cease after a certain duration of ST, with samples subjected to prior-HIPing exhibiting lesser precipitation of the δ phase during ST. While the specimen hardness increased onaging, it was observed to plateau after a duration significantly shorted than the specified ASTM 'standard' aging cycle. Therefore, prima facie there are promising prospects for shortening the overall heat treatment duration. A combination of HIPing, ST, and aging treatments in a single uninterrupted cycle was also explored. Future work involving incorporation of a shortened heat treatment schedule in a combined cycle can have significant industrial implications.Articles submitted to journals and unpublished manuscripts are not included in this registration
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Hsu, Melissa Karen. "Effect of Post Manufacture Thermal Dip Treatment on Proteolysis of Commercial String Cheese During Storage." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/924.
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String cheese, a Mozzarella cheese, has the unique ability to string in fibrous strands when pulled apart. Graders judge string cheese by its stringy texture; samples with copious amounts of string are awarded high ratings. But just as the texture of natural cheeses softens with time, the stringy texture of string cheese can diminish with age too.
Age related softening in cheese is due primarily to an important biochemical event known as proteolysis, which is attributed to inherent milk proteinases, residual coagulant activity, and enzymes from the lysis of starter culture microorganisms. It is hypothesized that a post manufacture heat treatment of string cheese could inactivate these proteolytic enzymes and slow or eliminate proteolysis during storage. Therefore, the main objective of this study was to determine the effects of a post manufacture thermal dip treatment on proteolytic activity in packaged, commercial string cheese. Proteolysis was examined qualitatively by Urea-PAGE electrophoresis, quantitatively by measuring percentage of water-soluble nitrogen (%WSN), and by using a scoring method to analyze stringy texture during refrigerated storage.
Fresh, commercial string cheese was sourced on two separate occasions and treated six days after manufacture. Treatment consisted of dipping the packaged cheese sticks in water baths at 55°C, 75°C, and 95°C for 30 and 60 seconds. String cheese that did not undergo treatment served as the control. Treated and control cheeses were stored at 4°C until sampling for Urea-PAGE, WSN extraction, and texture analysis on days 1, 11, 22, 29, 49, 91, and 172 after treatment.
The degree of β-CN breakdown was not observed to be different between all treatment levels throughout the storage period. This was not expected since Mozzarella cheese exposed to a higher temperature should have more plasmin activity than that of cheese exposed to a lower temperature. There was a trend of slightly more intact αs1-CN in the most severely treated string cheese (95°C for 60s) when compared to the control at the final time point of the study. This suggests the possibility of successful inactivation of residual coagulant, intracellular enzymes, or other proteolytic enzymes in the string cheese at this treatment. However, only storage time had a significant effect on %WSN (p
The research completed in this study provides insight of the proteolytic effects from a thermal treatment process applied post string cheese manufacture. Though relationships between the treatments to the extent of secondary proteolysis and stringy texture were not significant, it was still found that there was more intact αs1-CN due to one of the treatments. These results suggest that it is possible that the use of other heat treatment parameters, longer storage period, or a combination of the two could show a significant relationship between thermal treatment and proteolysis. These results also suggest that further work to improve shelf life of string cheese or other cheese varieties through the concept of a post manufacture heat treatment may be promising.
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Dai, Tao Dai. "Effect of Postweld Heat Treatment on the Properties of Steel Clad with Alloy 625 for Petrochemical Applications." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523572474171801.
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Liu, Jie [Verfasser], Norbert [Akademischer Betreuer] Huber, and Mathias [Akademischer Betreuer] Göken. "Phase transformations and stress evolution during laser beam welding and post heat treatment of TiAl-alloys / Jie Liu. Betreuer: Norbert Huber ; Mathias Göken." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2015. http://d-nb.info/1073611051/34.
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Mansfield, Anna Katharine. "The effects of post-fermentation and post-bottling heat treatment on Cabernet Sauvignon (V. vinifera L.) glycosides and quantification of glycosidase activities in selected strains of Brettanomyces bruxellensis and Oenococcus oeni." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34176.
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Thermal processing has been used as a means of modifying the sensory aspects of wine. Cabernet Sauvignon wines were heated prior to dejuicing (3ºC per day from 25ºC to 42ºC) or after bottling (42ºC for 21 days) to determine the effects on total glycosides and glycosidic fractions. Total and phenol-free glycosidic concentrations in the wine and skins were quantified by analysis of glycosyl-glucose. Pre-dejuicing thermal vinification resulted in higher total glycosides (12%), phenol-free glycosides (18%), total hydroxycinnamates (16%), large polymeric pigments (LPP) (208%) small polymeric pigments (SPP) (41%), and lower monomeric pigments (42%) in wines. Skins had lower total glycosides (-16%), and no significant difference in phenol-free glycosides. Post-bottling heat treatment resulted in lower total (-15%) and phenol-free (-16%) glycosides, increased hue (25%), a 62% increase in LPP and a 29% decrease in monmeric pigments.
A second study investigated the potential of enological spoilage microorganisms to affect wine aroma, flavor, and color. The activities of b-glucosidase were determined in model systems for fourteen strains of Brettanomyces bruxellensis yeast and nine strains of lactic acid bacteria (Oenococcus oeni). All Brettanomyces strains and seven Oenococcus strains exhibited enzymatic activity. B. bruxellensis b-glucosidase activity was primarily intracellular; O. oeni showed some extracellular activity. Yeasts and bacteria showing activity greater than 1000 nmole mL-1 g -1 for Brettanomyces, or 100 nmole mL-1 g -1 for Oenococcus, were evaluated for their effect on Viognier grape glycosides. Neither was active on native grape glycosides.Master of Science
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Westin, Elin M. "Welds in the lean duplex stainless steel LDX 2101 : effect of microstructure and weld oxide on corrosion properties." Licentiate thesis, KTH, Materials Science and Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9299.
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Duplex stainless steels are a very attractive alternative to austenitic grades due to their higher strength and good corrosion performance. The austenitic grades can often be welded autogenously, while the duplex grades normally require addition of filler metal. This is to counteract segregation of important alloying elements and to give sufficient austenite formation to prevent precipitation of chromium nitrides that could have a negative effect on impact toughness and pitting resistance. The corrosion performance of the recently-developed lean duplex stainless steel LDX 2101 is higher than that of 304 and can reach the level of 316. This thesis summarises pitting resistance tests performed on laser and gas tungsten arc (GTA) welded LDX 2101. It is shown here that this material can be autogenously welded, but additions of filler metal, nitrogen in the shielding gas and use of hybrid methods increases the austenite formation and the pitting resistance by further suppressing formation of chromium nitride precipitates in the weld metal. If the weld metal austenite formation is sufficient, the chromium nitride precipitates in the heat-affected zone (HAZ) could cause local pitting, however, this was not seen in this work. Instead, pitting occurred 1–3 mm from the fusion line, in the parent metal rather than in the high temperature HAZ (HTHAZ). This is suggested here to be controlled by the heat tint, and the effect of residual weld oxides on the pitting resistance is studied. The composition and the thickness of weld oxide formed on LDX 2101 and 2304 were determined using X-ray photoelectron spectroscopy (XPS). The heat tint on these lean duplex grades proved to contain significantly more manganese than what has been reported for standard austenitic stainless steels in the 300 series. A new approach on heat tint formation is consequently presented. Evaporation of material from the weld metal and subsequent deposition on the weld oxide are suggested to contribute to weld oxide formation. This is supported by element loss in LDX 2101 weld metal, and nitrogen additions to the GTA shielding gas further increase the evaporation.
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Westin, Elin M. "Welds in the lean duplex stainless steel LDX 2101 : effect of microstructure and weld oxides on corrosion properties." Licentiate thesis, Stockholm : Industriell teknik och management, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9299.
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Kassam, Tahsin Ali. "The effects of Alumina purity, TICUSIL® braze preform thickness and post-grinding heat treatment on the microstructure, mechanical and nanomechanical properties of Alumina-to-Alumina brazed joints." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/15311.
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Alumina-to-alumina brazed joints were formed using 96.0 and 99.7 wt.% Al2O3 ceramics in as-ground and in ground and heat treated conditions using TICUSIL® (68.8Ag-26.7Cu-4.7Ti wt.%) braze preforms of thicknesses ranging from 50 to 250 μm. Brazing was conducted in a vacuum of 1 x 10-5 mbar at 850 °C for 10 minutes. Joint strengths were evaluated using four-point bend testing and were compared to the flexural strengths of standard test bars according to ASTM C1161-13. Post-grinding heat treatment, performed at 1550 °C for 1 hour, did not affect the average surface roughness or grain size of either grade of alumina but affected their average flexural strengths, with a small increase for 96.0 wt.% Al2O3 and a small decrease for 99.7 wt.% Al2O3. Post-grinding heat treatment led to secondary phase migration, creating a fissured 96.0 wt.% Al2O3 surface. This affected the reliability of 96.0 wt.% Al2O3 brazed joints, in which braze infiltration was observed. As the TICUSIL® braze preform thickness was increased from 50 to 150 μm, the average strengths of both 96.0 and 99.7 wt.% Al2O3 brazed joints improved. This occurred due to a microstructural evolution, in both sets of joints, which was studied using SEM, TEM and nanoindentation techniques. An increase in the TICUSIL® braze preform thickness increased the amount of Ti which was available to diffuse to the joint interfaces. This led to increases in both, reaction layer and braze interlayer thicknesses. Excess Ti in joints that were made using TICUSIL® braze preforms thicker than 50 μm, led to relatively hard Cu-Ti phases in an Ag-Cu braze interlayer. Cu-Ti phase formation, which may have reinforced joint strength whilst also reducing CTE mismatch at the joint interface, also led to Ag-rich braze outflow at the joint edges. Brazed joints made using as-ground 96.0 wt.% Al2O3 consistently outperformed brazed joints made using as-ground 99.7 wt.% Al2O3, due to the formation of Ti5Si3 phases at locations where the Ti-rich reaction layer intersected with the triple pocket grain boundary regions of the as-ground 96.0 wt.% Al2O3 surface.
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Hussain, Mursheda. "Vapor CdCl2 Processing of CdTe Solar Cells." Scholar Commons, 2004. https://scholarcommons.usf.edu/etd/1088.
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Polycrystalline CdS/CdTe thin film solar cells are among the leading candidates for low-cost, large scale terrestrial photovoltaic applications. CdTe has a high absorption coefficient and it can absorb the radiant energy within less than 2 µm of thickness. This makes it suitable for thin film applications. CdTe has a band gap of 1.45 eV at room temperature, which is nearly optimum for photovoltaic conversion efficiency under the AM 1.5 solar spectrum. The theoretical maximum efficiency for CdTe solar cells is 29%. However, to-date the experimental value is in the 16 % range.
In most cases CdTe cells are subjected to a post-growth heat treatment which involves annealing in the presence of CdCl2. The treatment results in significant increases in conversion efficiency (η) and all three solar cell parameters Voc, FF, and Jsc.
In this work, several variations of the CdCl2 treatment were used on more than 100 samples to investigate their effects on the solar cell parameters. A vapor CdCl2 method was applied for the treatment with various source temperatures, substrate temperatures, and treatment times. The cells were characterized by dark and light J-V and spectral response (SR) measurements.
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Silva, Breno Mont'Alverne Haddade. "Efeito do tratamento térmico sobre a sorção e solubilidade, tenacidade à fratura e grau de conversão de compósitos restauradores diretos." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/23/23140/tde-22122010-114112/.
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O tratamento térmico em compósitos restauradores diretos foi realizado a fim de verificar a influência sobre algumas propriedades, tais como a sorção, solubilidade, tenacidade à fratura e grau de conversão. Foram utilizados três compósitos: um nanoparticulado, um microhíbrido e um microparticulado. Duas fontes de luz (Halógena e LED) e dois períodos (48h e 28dias) de armazenagem, com exceção da solubilidade. O tratamento térmico foi realizado em estufa convencional (170o C por 5min), sendo metade dos corpos de prova (cps) tratados e a outra, apenas fotoativada.Para sorção e solubilidade, foram confeccionados 60 cps de acordo com os fatores analisados (n=5) em uma matriz metálica circular de dimensões 15 mm x1 mm. Para o cálculo da sorção e solubilidade, os cps foram pesados em uma Balança Analítica,inicialmente após a confecção do cp, 1hora, 24h, 48h, 7d, 14, 21 e 28d, a fim de estabelecer Massa Inicial (Mi) Massa absorvida (Ma) e Massa dessecada (Md). Para a tenacidade à fratura, foram confeccionados 240 cps de acordo com os fatores analisados (n=10) em uma matriz metálica de dimensões internas 25 mm x 5mm x 2,8 mm. O método utilizado foi o Single Edge Notch-Beam(SENB), com um entalhe de 2,3 mm posicionado no centro da matriz. Os cps eram levados à máquina universal para o ensaio de flexão e, após a ruptura, as superfícies de fratura eram analisadas no estereomicroscópio, para, em seguida, obter as imagens e calcular as dimensões do cps para inserir naequação da tenacidade à fratura.Já para o grau de conversão foram confeccionados 36 cps em uma matriz de acetato circular de 15 mm x 1 mm, posicionados entre duas lâminas microscópicas (n=3). O cálculo do grau de conversão foi determinado por espectroscopia no infravermelho (FTIR).Em geral, os estudos apresentaram uma influência significante do tratamento térmico, Dos resultados para a sorção o compósito, em geral, diminuiu,comparado aos grupos somente fotoativados em ambos os períodos. Entre as interações analisadas (Fonte de Luz X Período) foi significante para todos os grupos. Para a solubilidade a interação (Fonte de luz X Tratamento térmico foi significante para todos os grupos. Quanto à tenacidade à fratura, apenas o fator tratamento foi significante para os compósitos nanoparticulado e microhíbrido. Já para os microparticulados, houve influência dos fatores principais e dasinterações(Fonte de Luz X Período) e Fonte de Luz X Tratamento Térmico). De maneira geral, houve um aumento dos valores de tenacidade para todos os grupos. Já para o grau de conversão, houve um aumento significativo com relação ao tratamento e os períodos analisados dos compósitos. O tratamento térmico, em geral, influenciou positivamente as propriedades estudadas. Sendo assim, a opção de realizar o tratamento térmico nos compósitos de acordo com as propriedades e fatores analisados, torna a técnica passível de ser recomendada.The post-curing heat treatment in direct composite treatment was done to verify the influence on some properties like sorption, solubility, fracture toughness and the degree of conversion. During the referred study it was used three composites: nanoparticle, a microhybrid and a microfill. Two sources of light (Halogen and LED) and two periods (48 hours and 28 days) for each one, but not to solubility. The postcuringwas done in dry heat sterilizer of 170º C for five minutes for, half of the test samples (TS) were treated and the other half were only photoactivated. It was made 60 TS to sorption and solubility according to the analyzed factors (n=5) in a 15mm x 1mm round metal matrix. To calculate sorption and solubility the TS were weighted in a analytical balance, right after the beginning of the production in 1 hour, 24 hours, 7days, 14 days, 21 days and 28 days respectively in order to establish the initial absorbed mass (Mi), the absorbed mass (Ma) and the desiccated mass (Md ). It was produced 240 TS to the fracture toughness according to factors (n=10) in a 25mm x 5mm x 2,8mm in metallic matrix. The Single Edge Notch-Beam (SENB), was the used method during this study with a notch of 2,3mm placed in the center of the matrix. The TS were taken to a universal machine to flexural test so after the rupture referred surface fractures were analyzed in a stereomicroscope and then it was possible to get the images to calculate the size of the TS to insert the calculus of the fracture toughness. To degree conversion were made 36 TS in a 15mm x 1mm circular acetate matrix placed between two microscopes slides (n=3). The degree conversion was determined a infrared spectroscopy (FTIR). In general the study showed a significant influence in relation post-curing heat treatment. In both periods the sorption of the composites have decreased in general comparison to the photoactivated only. The interactions(light source versus period) was significant for all groups. To solubility the interaction (light source versus post-curing heat treatment) was significant for all groups. In reference to fracture toughnessonly post curing heat treatment factor was significant to the nanoparticle and microhybrid composites. In other hand the microfill composite were influenced by the main factors and by the interactions (light source X periods) and (llght source X heat cured). In general there was an increase of the fracture toughness value in all groups. In relation to the degree conversion there was an increase significant of the composite during heat cured and analyzed periods. The post-curing heat treatment influenced all the studied properties of the direct composite in a positive way. Therefore the option of doing the heat cured treatment in the composites according to the properties and the analyzed factor is technically possible to be done.
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Guéroult, Bertrand. "Influence de la microstructure sur la resistance a l'usure des ceramiques : etude de traitements post-frittage et developpement d'un essai de rayage." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0094.
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On a cherche a mettre en evidence les differents effets de la microstructure et des proprietes intrinseques des materiaux etudies (al::(2)o::(3), sic, sialon) sur les mecanismes d'enlevement de matiere lors de l'usure par frottement a sec. Des modifications microstructurales ou morphologiques ont ete tentees par divers traitements de frittage ou de post-frittage. En particulier, on a etudie les effets du pressage isostatique chaud et de l'implantation ionique sur les proprietes mecaniques et tribologiques du sialon fritte. On a developpe un essai de rayage pour remplacer les essais d'indentation mal adaptes du fait du role joue par les debris d'usure consideres comme un troisieme corps. On a etudie les mecanismes creant ces debris ou les faisant evoluer. Il apparait que le rayage et l'usure des ceramiques, deux phenomenes lies a la creation de debris (avec ou sans circulation), doivent etre consideres comme faisant appel principalement au caractere plastique de debris agglomeres
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Idowu, Oluwaseun Ayodeji. "Heat Affected Zone Cracking of Allvac 718Plus Superalloy during High Power Beam Welding and Post-weld Heat Treatment." 2010. http://hdl.handle.net/1993/3911.
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The present dissertation reports the findings of a study of cracking behavior of a newly developed superalloy, Allvac 718Plus during high power beam welding and post-weld heat treatment. Microstructures of the base alloy, heat affected zone (HAZ) and fusion zone (FZ) of welded and post-weld heat treated (PWHT) coupons were examined by the use of standard metallographic techniques involving optical microscopy, analytical scanning electron microscopy (SEM) and analytical transmission electron microscopy. Moreover, grain boundary segregation behavior of boron atoms during pre-weld heat treatments was evaluated using secondary ion mass spectroscopic system.
In the first phase of the research, 718Plus was welded using a low and high heat input CO2 laser to assess its weld cracking response. Detailed examination of the welds by analytical electron microscopic technique revealed the occurrence of cracking in the HAZ of low heat input welds, while their FZ was crack free. However, both the FZ and HAZ of high heat input welds were crack-free. Resolidified constituents were observed along the cracked grain boundaries of the lower heat input welds, which indicated that HAZ cracking in this newly developed superalloy was associated with grain boundary liquation. However, despite a more extensive liquation of grain boundaries and grain interior in the HAZ of high heat input welds, no cracking occurred. This was attributed to the combination of lower welding stresses generated during cooling, and relaxation of these stresses by thick intergranular liquid.
Although HAZ cracking was prevented by welding with a high heat input laser, it resulted in a significant damage to the parent microstructure through its extensive liquation. Thus, the use of low heat input welding is desirable. However, this resulted in HAZ cracking which needs to be minimized or eliminated. Therefore, during the second phase of this research, the effects of pre-weld thermal processing on the cracking response of 718Plus were investigated. Results from the quantification of the cracking of the alloy showed that HAZ cracking may be significantly reduced or eliminated through an adequate selection of pre-weld thermal cycle.
In the third stage of this research, crack-free welds of 718Plus were post-weld heat treated using standard thermal schedules. A significant solid state cracking of the alloy occurred during the PWHT. The cracking was attributed to the presence of embrittling phases on HAZ grain boundaries, coupled with aging contraction stresses that are generated by a considerable precipitation of gamma prime phase during aging.
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Tsai, Ho-jin, and 蔡和晉. "A study of Mn content on the post-weld heat treatment processes of AA7003 Weldments." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/26739510997653184962.
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碩士國立臺灣科技大學
機械工程系
96
The objective of this study is to investigate the effects of Mn content on the mechanical properties of AA7003 weldments after various post-weld heat treatment processes. Weldments were prepared w/o ER5356 filler, and were subjected to artificial aging, T6, T73 and RRA heat treatment precesses. Optical metallographic observation, microhardness test, tensile test, EPMA, SEM, SCC test and TEM observation were conducted to characterize the mechanical properties of these heat-treated weldments. Experimental results show that T73 temper is the most suitable post-weld heat treatment process to produce weldment with right characteristics. Solid solution process can enhance the high inter-diffusion efficiency of Zn and Mg atoms between weld and base metal in low Mn AA7003 aluminum alloy. The Mg content of ER5356 filler metal makes the weld having high probability to precipitate out fine and widely-dispersed particles to improve strength of AA7003 weldments but possessing lower SCC resistance. TEM observations of welds(with filler) after T6 temper showed that relatively large size of η’ precipitates, comparing with the precipitate size of base metal, were observed. Welds after T73 temper, the microstructure is chacterized by the presence of large and scattered precipitates at grain boundary, as well as wide precipitation free zone(PFZ). The microstructure of welds after RRA process is a combination of those produced by T6 and T73 temper, widely-dispersed η’ precipitates inside the grain as well as large and scattered precipitates at grain boundary.
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Hsin-Ching and 楊欣璟. "Effect of Post-weld Heat Treatment on the Mechanical Properties of Dissimilar Aluminum Alloy 5083 and 7005 TIG welds." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/6z9ggc.
Full textAbstract:
碩士國立中央大學
機械工程學系在職專班
106
Because of the high specific strength and good corrosion aluminum alloys have been used extensively since the period of energy crises. Aluminum has greater thermal conductivity and larger thermal expansion than steels. Therefore, the weldability of aluminum alloys is not as good as steels. It is very important to study the weldability of dissimilar joint of aluminum alloys. The purpose of this research was to systematically study the weldability of aluminum alloys under Tungsten Inert Gas Arc Welding (TIG). The base metals used were 5083 and 7005 with filler metal of ER5183. Different post weld heat treatments of the weldments were conducted. A series of experiments including tensile test, microhardness test, optical metallography and SEM analysis were used to determine the releationship between mechanical properties and microstructures of the alumimum weldments. The experimental results indicate that there is no obvious difference between the 5083 weldments because they are non-heat-treatable aluminum alloys. Proper post weld heat treatment (full heat treatment) can increase the mechanical properties of the 5083-7005 dissimilar weldments. Post weld full heat treatment has a great influence on mechanical properties of the heat-affected zone of 7005 weldment.
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Huang, Chun-Jung, and 黃俊榮. "The Influence of Aluminum Content on Hot Cracking and Post-Weld Heat Treatment of Magnesium Alloys." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/77394568961342471379.
Full textAbstract:
博士國立交通大學
機械工程學系
100
The aims of this study are to investigate the effect of aluminum content on hot cracking and post-weld heat treatment of AZ series magnesium alloys. Part one, the AZ series magnesium alloys' hot cracking susceptibility is affected by aluminum content. The spot varestraint testing is used to evaluate the hot cracking susceptibility of AZ series magnesium alloys, namely AZ31, AZ61 and AZ80. The effect of augment strain and the numbers of thermal cycles on the cracking susceptibility are investigated, and the total crack length is used to evaluate the hot cracking susceptibility. The results indicate that both the increase of aluminum content in magnesium alloys and multiple thermal cycles cause the total length of W.M.HAZ's cracks to become longer. Al content plays an important role in the hot cracking mechanism. The non-equilibrium solidification process precipitates Al to unsolidified alloy liquid during alloys solidification. When there is more Al content, the more precipitation (Mg17Al12) with low melting point is produced at grain boundaries. The heat produced in the welding process causes Mg17Al12 liquefaction to form grain boundaries liquefaction. Pulled by the augment strain, the grain boundaries liquefaction shows hot cracking. To sum up, the Al content of AZ series magnesium alloys can be used to assess the hot-cracking susceptibility. The hot cracking susceptibility of AZ80 is higher than that of AZ61 and AZ31. The second part investigates the post-welding heat treatment of AZ series magnesium alloy weldment. AZ31, AZ61 and AZ80 are welded in butt welding by semi-GTAW, using AZ61 as filler metal. T6 heat treatment, solution treatment + artificial aging, are imposed on three types of magnesium weldment. The Mg17Al12 precipitates in grain and grain boundaries at fusion and base metal after T6 treatment. With more aging time, the more Mg17Al12 is produced in grain and grain boundaries. AZ80's precipitation hardening effect is the best among AZ series magnesium alloys. The results indicate that Mg17Al12's quantity affects the Hv hardness and tensile strength of weldment. Thus, AZ80 has the best hardening effect after post-welding heat treatment, because it has more Al content that it can precipitate much Mg17Al12 to improve mechanical properties. It is noteworthy that over aging effect occurs during 8 to 16hours of aging time. Experimental results show that the aging time reaches over 8 hours, Mg17Al12 will be refined. So long aging time can replace the function of alloying elements Zn of AZ80.
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Filmalter, Rudi. "The effect of repeated post weld heat treatment on the mechanical properties of ASTM A302 grade B." Thesis, 2016. http://hdl.handle.net/10539/20098.
Full textAbstract:
A dissertation submitted to the Faculty of Engineering and the Built
Environment, University of the Witwatersrand, in fulfilment of the
requirements for the degree of Master of Science in Engineering.
Johannesburg 2015Erosion-corrosion on ash lock internal surfaces means that these equipment are continuously refurbished through weld build-up, followed by post weld heat treatment (PWHT). The deterioration of mechanical properties of the ash locks after numerous PWHT cycles has been a concern. A graphical prediction model based on experimental work on this material grade has been derived previously to predict the mechanical properties after a number of PWHT cycles. The validity of the model was, however, questioned. Ash lock, 210AL-3401, was scrapped for the purpose of testing the effect of several PWHT cycles on the mechanical properties and microstructure to determine whether the current model is valid or needs to be optimised. Test samples of the ASTM A 302 Grade B manganese-molybdenum material were cut from the shell and top dome parent metal and shell-to-dome weld of the test ash lock and subjected to a number of additional simulated PWHT cycles with holding times ranging from 2 to 100 hours. This was followed by mechanical testing, i.e. tension -, hardness - and Charpy V-notch impact testing, in accordance with SA-370, and metallographic examination after each PWHT cycle. Test results showed that actual measured tensile properties for the shell and dome samples were generally higher than what was predicted by the current model and, similar to hardness, followed an overall downward trend with increasing PWHT cycles for the shell, dome and weld. Impact toughness for the shell and dome was mostly above the minimum required values, but after 100 hours of additional PWHT impact toughness was below the minimum required values when tested at 0°C and above minimum required values when tested at higher temperatures. Impact toughness for the shell-to-dome weld showed an overall increase with increasing PWHT. Metallographic examination showed an overall increase in quantity and size of molybdenum carbides and spheroidisation of the cementite phase for the shell and dome samples with increasing PWHT. Significant coarsening of the carbides together with an increase in the level of spheroidisation resulted in a rapid decrease in tensile properties and impact toughness with increasing PWHT. Similar effects were observed on the microstructure of the weld samples, but no significant effect on impact toughness was observed.
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Lu, Hsin-Chang, and 盧信璋. "The effect of post-weld heat treatment on the microstructure and mechanical properties of Ti-alloy EBW weldment." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/75316050820988899216.
Full textAbstract:
碩士國立交通大學
工學院精密與自動化工程學程
100
Ti-6Al-4V alloy at different observation of welding heat treatment before influence on their mechanical characteristic and microstructure, followed by electron beam welding study the effect of heat-treatment process before and after the welding together with the microstructure and mechanical property investigation of welded sample. The optimal heat-treatment parameters can therefore be obtained by the above test results. The results of the heat-treatment study conducted under varied stress-relief temperatures and Solution aging treatment have shown that Effect of stress-relief with aging treatment after welding, and stress-relief the selected temperature and time and the aging treatment of selected temperature and time are similar, therefore has the same microstructure, and stress relief heat treatment after welding weld does not affect their strength and toughness.
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李俊賢. "The Influence of Post-Weld Heat Treatments on The Mechanical Properties of Ti-6Al-6V-2Sn Laser Welds." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/59018129192623815369.
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jack, lin chung, and 林忠傑. "The Effect of Cold Working and Post-weld Heat Treatment on the Mechanical Properties of Aluminum Alloy 1050 Weldment." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/10843256642381657995.
Full textAbstract:
碩士國立臺灣師範大學
工業教育研究所
88
Abstract Because the characteristics of "high strength to weight"ratio, easy formability and good corrosion resistance and oxygen resistance, aluminum and its alloys have been applied extensively in industry.Some problems obtained from welding process can heavily influence the mechanic properties of aluminum alloy weldment. The problems can be eliminated only by proper welding skills and post weld treatments. The purpose of this research is to study the ability of weld in aluminum alloys weldments under pre-weld cold working and post-weld heat treatment and post-weld cold working. The base metal materials are 1050 aluminum alloys with filler metal of ER4043. A series of experiments including tensile test, microhardness test, optical microscope metallography observation and SEM(Scanning Electron Microscope) were used to determine the relationship among the condition of cold working, weld structure of HAZ(Heat-Affected Zone) and type of heat treatments. A series of experiment results and observations indicated that pre-weld cold working can increase the strength and improve the quality of 1050 aluminum alloys. After pre-weld cold working of weldment can reduce their elongation slightly , however, their uitimate tensile strength and microhardness can be enhanced except the fusion zone.And post-weld with 200℃,8 hour heat treatment can not improve the mechanical properties of 1050 aluminum alloys. After post-weld with cold working, 1050 aluminum alloys can greatly enhance its mechanical properties(tensile strength and microhardness)in base metal zone, heat affected zone . The result form SEM(Scanning Electron Microscope) observations indicated that ductile fracture surface occurred in all tensile tested specimen no matter what treatments
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LIN, SHENG-XIAN, and 林勝賢. "The effects of nitrogen added to shielding gas and post-weld heat treatment on the weldability of duplex stainless steels 2205." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/46604279265746268528.
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Widener, Christian Aragon. "Evaluation of post-weld heat treatments for corrosion protection in friction stir welded 2024 and 7075 aluminum alloys." Diss., 2005. http://hdl.handle.net/10057/612.
Full textAbstract:
This dissertation presents the results of an investigation into the corrosion resistance of friction stir welding (FSW) for aerospace structures. Two of the most common aerospace aluminum alloys, 2024 and 7075, were investigated. In the as-welded condition, both alloys were found to be highly susceptible to exfoliation corrosion, and 7075 was found to be susceptible to stress corrosion cracking as well. The goal of this research was to identify proper initial temper selection and postweld aging treatments for enhancing the corrosion resistance of both 2024 and 7075 alloys, and their dissimilar joints. A large number of heat treatments were investigated for 7075 in the T6 and T73 tempers, including retrogression re-aging (RRA). Heat treatments were also investigated for 2024-T3 and 2024-T81. Samples were evaluated for resistance to exfoliation corrosion using optical microscopy. Microhardness, electrical conductivity, tension, and fatigue crack propagation tests were also performed on the samples. Beneficial heat treatments were found for both alloys as well as for their dissimilar joints."December 2005."
Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering
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Chang, Chin-Chun, and 張進春. "The Study of Hot Cracking Characteristic and Post-weld Heat Treatment of Dissimilar Welding on the High-strength Aluminum Alloys for Aerospace Applications." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/81790887254945874251.
Full textAbstract:
博士國立交通大學
機械工程學系
100
The objectives of this research are to investigate the hot cracking characteristics of weldment of high-strength aluminum alloys and aluminum-scandim alloys, and the effect of post-weld heat treatment of on the mechanical properties of high-strength aluminum alloys. This research includes two parts. The first part is on the susceptibility of hot cracking of high-strength aluminum alloys A2024, A2219 and A7050, and the hot cracking susceptibility of the aluminum-scandium alloys M6, M7B, M7E and M9H4. The second part is to study the effect of post-weld heat treatment on the mechanical properties and microstructure for dissimilar welding of high-strength aluminum alloys A7050/ A7075 and A2024/A7050. In the first two parts, the spot varestraint testing was used to evaluate the hot cracking sensitivity of those material. The influence of augment strain. and muti-thermal cycles on the hot cracking suscepitbility were investigated. The total crack length was measured and calcuated to evalute the hot cracking susceptibility. The results indicate that: the number of cracks increases with increasing augmented strain. This phenomenon occurs in both the fusion and the heat-affected zones. The number of thermal cycles also has a significant influence on the heat-affected zone. A2024 and A7050 have similar tendencies to be subjected to hot cracking, greater than A2219. With increasing numbers of thermal cycles, the hot cracks show the same tendency, A2024>A7050>A2219.The Energy Dispersive Spectrometer composition analysis results show that, the Cu segregation is increases with the number of thermal cycles. In the Al-Sc alloys, the effect of number of thermal cycles. and augment strain processes were evaluted and compared for the M6, M7B, M7E and M9H4 alloys. In the fusion zone, no significant results were obserred on the hot cracking sensitivity. In the weld metal heat affected zone, the number of cracks increases with increasing augmented strain and the number of thermal cycles with the different Al-Sc alloys by the thermal cycles. The trend of hot cracking sensitivity of the total crack length show that M9H4> M7E> M7B> M6. M6 and M9H4 have the Cu element segregation in the vicinity of grain boundaries, and are the Cu segregation increases with the number of thermal cycles. So that the M6 and M9H4 are segregation-induced liquation mechanism in the partially melted zone. In the grain boundaries of the heat-affected zone of M7B, M7E alloys, the content of Zn element increase significantly, but Mg content does not. These two kinds of alloys are purely grain boundary liquation. On cracking fracture surface, the experiment results show three distinct regions in the fusion zone, dendritic area (D area), dendritic-flat area(D-F area) and the flat area (F area), to confirmed the fusion zone belong to the solidification cracking. In the heat affected zone, the results indicate the brittleness fracture phenomenon along grain boundary on the fracture surface, and it is presented in the form of liquefied hot cracking. Finally, the second portion that of this desseration is to discuss the similarty and dissimilarty for A7050/A7075, A2024/A7050 similar and dissimilar welding for high-strength aluminum alloys. The Gas Tungsten Arc Welding(GTAW) was used to weld butt joint with different filler materials, such as ER5183, ER5356, ER5556 and ER2319. The post-weld heat treatment processes were carried out to evalute and analysis on the effect of the mechanical properties and microstructure. The experiment results showed that the yielding and ultimate tensile strength of weldment on the post-weld not-heat treatment has singificantly declinc to lower than 60% of the base metal strength, post-weld heat treatment can be improved and promoted the weldment mechanical properties, These are still slightly lower than the base metal. In conclusion, the weldment weakest place is still at the weld. And then uses ER5356 or ER5556 filler, it can get the optimal mechanical properties when the weldment of post-weld heat treatment are executed artificial aging and over-aging. In tensile fracture surface, its still has the morphology of ductile facture.
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Lin, I. Shin, and 林宜勳. "The study of microstructure and mechanical properties on the dissimilar welding and post-weld heat treatment with A7075 / A7050 high strength aluminum alloys." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/31071700542655814554.
Full textAbstract:
碩士國立交通大學
工學院精密與自動化工程學程
101
The article was investigated on the A7050 and A7075 dissimilar welding and it’s mechanical properties for post-weld heat treatment process. In this experiment, tungsten inert gas (TIG) welding process was utilized to make weldments with filler metals of ER5183 and ER5356 and ER5556. The effect of heat treatment of natural aging (T1), solution treatment(T4), and solution treatment plus artificial aging(T6) on the weldment were investigated. The tensile test, microhardness test, and optical microscope were used to study the mechanical properties and microstructures the effect of different trace elements on the material mechanical properties and microstructure is also determined. After T4 or T6 heat treatment, multiple precipitates were found in heat affected zone(HAZ) grain and grain boundaries. The microhardness, ultimate tensile strength, and yield strength of the heat treated weldment were greatly enhanced by the heat treatment. The fractured surface of T1 treatment shows dimple appearance indicating some ductility. In T6 treatment, some region maintain dimple surface, some region tend to brittleness cracking.
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Huang, Chung-yu, and 黃重瑜. "The effect of a post-weld heat treatment on the metallurgical and mechanical properties of SS400 and S45C dissimilar joints welded by the gas shielded flux cored arc welding." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/34082947695265937431.
Full textAbstract:
碩士國立中央大學
光機電工程研究所
103
Ships, bridges, pressure vessels, industrial machinery, automobile, rolling stock and many other fields are all produced by welding technology. The common problem in these fields is associated with welding process. The maximum hardness of the heat affected zone (HAZ) and the cold cracking susceptibility of welds are results in Weldability of steel. It would generate harder HAZ, cold crack susceptibility and residual stress in weldment, when steel is welded non uniform heating and cooling in weld metal and in base metal. To slow the heating and cooling rate of the base metal and weld heat affected zone is the best way to minimize difficulties above. However there are many methods to solve it and one of them is preheating and post weld heat treatment (PWHT). Preheating and PWHT have been widely employed in welding operation for preventing cold cracking and the maximum hardness in HAZ. The weldments with double V groove type were butt-welded by multiple passes as shown in Fig. 2. An automated Gas shielded Flux-Cored Arc Welding (FCAW-G) machine was used, with a welding wire of diameter 1.2 mm and CO2 shielding gas at 20 Lmin-1 flow rate, conforming to the American Welding Society standards AWS A5.20. In this study, it investigate the effects of preheating and PWHT on the microstructure, mechanical properties of JIS G3101 SS400 structural steel and AISI 1045 midium carbon steel dissimilar joints. It would eliminate the maximum hardness in the S45C HAZ and increase the toughness of the weldment. The welding process would be standardized which base on the obtained optimization parameters, in order to ensuring the welding quality from different workers that could reach the demands of industry.
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Oliveira, Diogo Brízido Caldas. "Electron Beam Welding of TZM plates." Master's thesis, 2015. http://hdl.handle.net/10362/31890.
Full textAbstract:
Recently, many efforts have been made to join molybdenum and its alloys, such as TZM, due to their interest for industrial applications. However, it has a poor weldability due to high thermal conductivity and high melting temperature, sensitivity to gas impurities and lack of solid state transformations leading to coarse grain formation. Electron beam welding (EBW) is a high energy density process, and welding TZM can result in a smaller fusion and heat affected zones. The aim of this study was to perform an exploratory investigation on the ability of EBW to weld TZM, focusing on the major process parameters, the clamping system and evaluate the effect on the weld tensile strength. The selection of the parameter values and their refinement was performed using design of experiments.
Sound welds were obtained, free of pores, cracks and misalignments. A dedicated clamping system was designed, manufactured, and proved to be of major importance. Tensile strength was close to 80% of the base material, which is remarkably good for this alloy. Pre- and post-weld treatment had no significant effect on the welding strength. However, further work is needed to minimize grain coarsening, eventually by stirring the molten pool using beam deflection.