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1
Lima, Diego Rodolfo Simões de. "Desenvolvimento e controle de processos de conformação da liga de magnésio AZ61." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/49295.
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O presente trabalho estuda a conformação da liga de magnésio AZ61 pelos processos de extrusão direta e forjamento, ambos a quente. No processo de extrusão, são submetidos à conformação corpos-de-prova da liga de magnésio AZ61 nos estados fundido e recristalizado. As geometrias de ferramenta são variadas e a influência destas variações sobre a força de processamento e propriedades mecânicas e microestrutura do material são analisada. Demonstra-se que a liga no estado inicialmente recristalizado tem propriedades mecânicas finais superiores à liga inicialmente fundida, embora demande de maior força de processamento. Demonstra-se também que a geometria de ferramenta tem influência sobre as respostas mecânicas obtidas das peças após extrusão. Referente ao processo de forjamento, a liga de magnésio AZ61 é processada apenas no estado recristalizado, variando-se a temperatura e o número de tapas de forjamento. Foi avaliada a influência destas variações de processo nas propriedades mecânicas finais da peça. Ao fim, percebe-se que ao se forjar as peças com múltiplas etapas de forjamento e temperaturas decrescentes, impede-se a recristalização do material, alcançando alto encruamento dos grãos, o que gera, na peça final, propriedades mecânicas superiores ao processo convencional.This thesis studies the deformation of a magnesium alloy AZ61 by forward extrusion and forging processes, at elevated temperatures. In the extrusion process, the samples were deformed in as cast and recrystallized conditions. The tools geometries were variated and the influences on processing force, mechanical properties and material microstructure were analyzed. Was found that the recrystallized samples have better mechanical properties than as cast samples, after extruded, although it requires more processing force. Also was found that the tool geometry influences on mechanical properties and microstructure of extruded magnesium alloy. Relatively to the forging process, magnesium alloy AZ61 was processed only in the recrystallized state, varying the process temperature and the number of forging steps. Aimed to evaluate the process variations influences on the mechanical properties and microstructure of the final parts. At the end, was observed that when forging parts with multi-step forging and decreasing temperatures, to prevent recrystallization of the material, achieving high strain hardening of the grains, which results in final part with superior mechanical properties to the conventional process.
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Bayandorian, Iman. "Magnesium alloy strip produced by a melt-conditioned twin roll casting process." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4506.
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Twin roll casting (TRC) offers a promising route for the economic production of Mg sheet, but unfortunately, it produces strip with coarse and non-uniform microstructures and severe centre line segregation. Recently, a novel magnesium strip casting process termed melt conditioned twin roll casting (MC-TRC) was developed that, compared with the conventional TRC process, emphasizes solidification control at the casting stage rather than hot rolling. This was achieved by melt conditioning under intensive forced convection prior to twin roll casting resulting in enhanced heterogeneous nucleation followed by equiaxed growth. In this study the development of TRC and MC-TRC processes and a microstructural comparison of the MC-TRC Mg-alloy strip with that of conventional TRC strip, have been investigated. Emphasis has been focused on the solidification behaviour of the intensively sheared liquid metal, and on the mechanisms for microstructural refinement and compositional uniformity in the MCTRC process. The results of the process development indicate that the MC-TRC process reduces considerably or eliminates defects such as the centre line segregation, voids and cracks at or near the strip surface that are always present in conventional TRC strip. The newly-designed homogenization treatment investigated for TRC and MC-TRC magnesium alloy strips was based on microstructural evolution obtained during heat treatment. The results of the MC-TRC strips showed a much faster recrystallization rate with finer recrystallized grains, which are due to more homogeneous and a finer grain size of the as-cast MC-TRC strips compared with the as-cast TRC strips. During down-stream processing, the effects of MC-TRC process on microstructural evolution of hot-rolled magnesium strips have been understood thoroughly by accurate control of the hot-rolling procedure during each step of strip thickness reduction. This study indicates that the MC-TRC strip requires fewer rolling steps when compared to TRC strip, thus offering reduced processing cost and carbon footprint. Mechanical properties at room temperature of MC-TRC as-cast and rolled sheets are much improved when compared with the conventional TRC as-cast and rolled sheets which can result in a higher quality of final components. The mechanical properties at elevated temperature shows for the first time that the higher elongation and lower yield strength of MC-TRC as-cast strips at a temperature close to its optimised hot-rolling temperature results in better ability for rolling and higher ductility of MC-TRC Mg strip compared with the TRC Mg strip.
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Guan, Xiaofei. "Novel process for recycling magnesium alloy employing refining and solid oxide membrane electrolysis." Thesis, Boston University, 2013. https://hdl.handle.net/2144/11005.
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Thesis (Ph.D.)--Boston UniversityMagnesium is the least dense engineering metal, with an excellent stiffness-to-weight ratio. Magnesium recycling is important for both economic and environmental reasons. This project demonstrates feasibility of a new environmentally friendly process for recycling partially oxidized magnesium scrap to produce very pure magnesium at low cost. It combines refining and solid oxide membrane (SOM) based oxide electrolysis in the same reactor. Magnesium and its oxide are dissolved in a molten flux. This is followed by argon-assisted evaporation of dissolved magnesium, which is subsequently condensed in a separate condenser. The molten flux acts as a selective medium for magnesium dissolution, but not aluminum or iron, and therefore the magnesium collected has high purity. Potentiodynamic scans are performed to monitor the magnesium content change in the scrap as well as in solution in the flux. The SOM electrolysis is employed in the refining system to enable electrolysis of the magnesium oxide dissolved in the flux from the partially oxidized scrap. During the SOM electrolysis, oxygen anions are transported out of the flux through a yttria stabilized zirconia membrane to a liquid silver anode where they are oxidized. Simultaneously, magnesium cations are transported through the flux to a steel cathode where they are reduced. The combination of refining and SOM electrolysis yields close to 100% removal of magnesium metal from partially oxidized magnesium scrap. The magnesium recovered has a purity of 99.6w%. To produce pure oxygen it is critical to develop an inert anode current collector for use with the non-consumable liquid silver anode. In this work, an innovative inert anode current collector is successfully developed and used in SOM electrolysis experiments. The current collector employs a sintered strontium-doped lanthanum manganite (La0.8Sr0.2Mn03-δ or LSM) bar, an Inconel alloy 601 rod, and a liquid silver contact in between. SOM electrolysis experiments with the new LSM-Inconel current collector are carried out and performance comparable to the state-of-the-art SOM electrolysis for Mg production employing the non-inert anode has been demonstrated. In both refining and SOM electrolysis, magnesium solubility in the flux plays an important role. High magnesium solubility in the flux facilitates refining. On the other hand, lower magnesium solubility benefits the SOM electrolysis. The dissolution of magnesium imparts electronic conductivity to the flux. The effects of the electronic conductivity of the flux on the SOM electrolysis performance are examined in detail through experiments and modeling. Methods for mitigating the negative attributes of the electronic conductivity during SOM electrolysis are presented.
4
Tantipaibulvut, Chairath. "An evaluation of the production of magnesium base alloy castings by the expendable pattern casting process." Thesis, Loughborough University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250959.
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Okcu, Isik Yilmaz. "Effect Of Process Parameters On Mechanical Properties Of High Pressure Die Cast Magnesium Az91 Components." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613896/index.pdf.
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Before beginning the experimental work of this study, a magnesium high pressure die casting facility is set up to manufacture magnesium cast parts for defence industry. In this thesis two components are cold chamber high pressure die casted using magnesium alloy AZ91 as raw material, and one component was manufactured using both aluminium alloy A.413, and magnesium alloy AZ91.
Mechanical properties of high pressure die casting parts depend on various parameters such as, thickness of the cast part, position of the cast part in the cavity, molten metal temperature, die temperature, piston speeds, and injection pressure. The aim of this study is to investigate the effects of section thickness of the cast part, position of the cast part in the die cavity, piston speeds, and molten metal temperature on mechanical properties of magnesium die cast parts. Tensile properties of products from Al A.413 and Mg AZ91 alloys are also compared.
Casting analysis software is used to simulate filling and temperature evolution of three different casting components. Piston speeds are first calculated from equations in the literature and then verified by using the software. Specimens for microstructural investigation, and mechanical tests are machined directly from the mass produced parts. Optical microscopy, and scanning electron microscopy investigations are carried out for grain size and porosity determination. Tensile tests are conducted for yield strength, ultimate tensile strength, and % elongation values. The results of casting analysis software simulations, grains size investigations, porosity investigations, and tensile tests are correlated to each other.
Optimum piston speeds, optimum molten metal temperatures are observed, effect of grain size and porosity concentrations on the effect of mechanical properties are compared. Weight of cast parts produced from Mg AZ91 are 35 % lower than that of Al A.413 parts. However, ultimate tensile strength of the cast parts produced from Mg AZ91 are found to be similar to the aluminium parts.
6
Ghasemi, Abyazani Alireza [Verfasser]. "Contribution to understanding the formation process and corrosion protection of the PEO coating on AM50 magnesium alloy / Alireza Ghasemi Abyazani." Clausthal-Zellerfeld : Universitätsbibliothek Clausthal, 2011. http://d-nb.info/1013490460/34.
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Klarner, Andrew Daniel. "Development of Mg-Al-Sn and Mg-Al-Sn-Si Alloys and Optimization of Super Vacuum Die Casting Process for Lightweight Applications." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1515083355012541.
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Ho, Yee Hsien. "In Vitro Behavior of AZ31B Mg-Hydroxyapatite Metallic Matrix Composite Surface Fabricated via Friction Stir Processing." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc862762/.
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Magnesium and its alloys have been considered for load-bearing implant materials due to their similar mechanical properties to the natural bone, excellent biocompatibility, good bioactivity, and biodegradation. Nevertheless, the uncontrollable corrosion rate in biological environment restrains their application. Hydroxyapatite (HA, Ca10(PO4)6(OH)2) is a widely used bio-ceramic which has bone-like mineral structure for bone fixation. Poor fracture toughness of HA makes it not suitable for load-bearing application as a bulk. Thus, HA is introduced into metallic surface in various forms for improving biocompatibility. Recently friction stir processing (FSP) has emerged as a surface modification tool for surface/substrate grain refinement and homogenization of microstructure in biomaterial. In the pressent efforts, Mg-nHA composite surface on with 5-20 wt% HA on Mg substrate were fabricated by FSP for biodegradation and bioactivity study. The results of electrochemical measurement indicated that lower amount (~5% wt%) of Ca in Mg matrix can enhance surface localized corrosion resistance. The effects of microstructure,the presence of HA particle and Mg-Ca intermetallic phase precipitates on in vitro behavior of Mg alloy were investigated by TEM, SEM, EDX,XRD ,and XPS. The detailed observations will be discussed during presentation.
9
Cabrol, Elodie. "Étude et compréhension des mécanismes d'endommagement de surface de matrices de forgeage à chaud rechargées." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2015. http://www.theses.fr/2015EMAC0012.
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Dans le domaine du forgeage à chaud de pièces aéronautiques, les matrices en acier sont couramment rechargées, sur quelques millimètres d’épaisseur, par un alliage base cobalt (Stellite 21) déposé par procédé de soudage à l’arc (MIG). Dans le cadre de ce travail de thèse, ce rechargement « classique» est comparé à des rechargements Stellite 21 et Stellite 6 déposés par deux procédés émergents dans ce domaine, le PTA et le LASER. L’objectif est d’apporter des éléments de compréhension aux mécanismes d’endommagement de surface, notamment par écoulement plastique, de ces différents rechargements afin de dégager des voies d’amélioration pour augmenter la durée de vie des matrices. Pour cela, des essais tribologiques (semi-industriels et laboratoire) ont été mis en œuvre pour créer des endommagements de surface comparables à ceux observés sur matrices industrielles. Associées à ces essais, des investigations microstructurales, structurales et mécaniques multi-échelles ont été réalisées (traction, flexion, microdureté, MO, MEB, MEB-STEM, DRX, EBSD). Selon les couples « nuance/procédé » de rechargement, des mécanismes de déformation plastique par glissement des dislocations parfaites et par transformation de phase CFC en HC ont été identifiés. L’activation de ce dernier a pu être reliée à la température de transformation allotropique CFC/HC du cobalt. Cette température dépend à la fois (i) des éléments d’addition, variant en fonction de la nuance déposée (Cr, C,...), (ii) de la dilution (variation de la teneur en Fe) liée aux paramètres de soudage et (iii) du nombre de couches déposées. De plus, une influence significative de la transformation de phase sur l’évolution du coefficient de frottement a été mise en évidence. En effet, dans le cas où la transformation de phase n’est pas observée, le coefficient de frottement est stable durant l'essai alors qu'une chute de la courbe de coefficient de frottement a été reliée avec la transformation de phase CFC en HC. Parallèlement, l'écoulement plastique des dendrites est observé en extrême surface sur quelques dizaines de micromètre d'épaisseur dans la direction de glissement. Cet écoulement est associé à une forte texturation morphologique et cristallographique de la phase identifiée (CFC ou HC), avec une orientation des plans de plus grande densité atomique parallèlement à la surface de glissement. Les résultats montrent également que sous sollicitations tribologiques, un important durcissement est observé en surface (jusqu'à 90%) et une corrélation a pu être établie entre l'augmentation de la microdureté et le taux de déformation plastiqueIn the field of hot forging of aeronautical parts, the steel dies are commonly hardfaced, on few millimeters thick, by a cobalt-based alloy (Stellite 21) deposited by arc welding (MIG). As part of this thesis, this "classic" hardfacing is compared to Stellite 21 and Stellite 6 hardfacings deposited by two emerging processes in this area, the PTA and the LASER one. The objective is to assess surface damage mechanisms, especially induced by plastic strain, of these various hardfacings. Tribological tests (laboratory and semi-industrial) were used to create surface damage comparable to those observed in industrial dies. Associated with these tests, multiscale microstructural, structural and mechanical investigations have been performed (tensile, bending, microhardness, OM, SEM, STEM, XRD, EBSD). According to the « material/process » couple, plastic strain mechanisms by perfect dislocation glide and by FCC to HCP phase transformation have been identified. The activation of the latter has been connected to the temperature of the allotropic phase transformation (FCC/HCP) in cobalt. This temperature depends on (i) the alloying elements, varying according to the deposited grade (Cr, C, ...), (ii) the dilution (Fe content evolution) connected to the welding parameters and (iii) the number of deposited layer. Moreover, a significant influence of the phase transformation on the evolution of the friction coefficient has been evidenced. Indeed, if the phase transformation is not observed, the friction coefficient is stable during the test, while a drop of the friction coefficient curve is connected with the FCC to HCP phase transformation. Moreover, the plastic flow of dendrites is observed at the extreme surface, on a few tens of micrometres in thickness, in the direction of sliding. It is associated with a high morphologic and crystallographic texturing of the identified phase (FCC or HCP), with the highest atomic density planes mostly oriented parallel to the sliding surface. The results also show that, under tribological laodings, a significant hardening is observed on the surface (up to 90%) and a correlation has been established between the increase in the microhardness and the plastic deformation ratio
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Huang, Po-Yao, and 黃柏堯. "Study on Formability of Magnesium Alloy under Forging Process." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/tzhw3c.
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碩士國立臺灣科技大學
機械工程系
94
This study investigated the mechanical properties and forming characteristics of AZ31 and AZ61 magnesium alloys under hot working. Compression tests were carried out under various forming temperatures to study the relation of stress and strain. Then, the ring compression tests were carried out under various forming temperatures and friction conditions to determine the friction factor in the interface between the die and the specimen. In addition, flange forging were performed under various process parameters to find the best forming condition for low load and smooth surface. Finally, the optical microscope was used to analyze the change of microstructure and evaluate the relation between micro hardness and compression strain. It is expected to be helpful to academic research and related industry.
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Huang, Zun-Yao, and 黃圳遙. "Investigation on the formability of magnesium alloy bar under hot forging process." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/4t9skr.
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碩士國立臺灣科技大學
機械工程系
95
This study investigated the mechanical properties and forming characteristics of AZ61 magnesium alloys bar under hot working. Firstly we utilized high speed metal test machine of China Steel Co. Ltd. to carry out the compression tests under different forming temperatures and strain rates to obtain the stress-strain curves. Then, bearing cover of gear box in car components was selected as a carrier in hot forging to probe into the formability of magnesium alloys. And, the stress-strain data obtained from compression test under different forming temperatures and strain rates are applied to analyze the formability of the bearing cover by commercial package DEFORM. Finally, by comparing the analytical results of DEFORM simulation and the experimental results. we tried to figure out the method that can manufacture bearing cover perfectly with low forging load. we also evaluated how temperature influenced hardness and microstructure of the bearing cover .
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Ou, Yu-fu, and 歐育附. "Application of ANN to study formability of Magnesium Alloy under hot forging process." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/89714972174178636894.
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碩士國立臺灣科技大學
機械工程系
96
This study investigates the mechanical properties and forming characteristics of AZ31 and AZ61 magnesium alloy parts with different temperatures under hot forging. Process parameters considered in this study are the heating temperature of billet and the lubricants. A cylinderial parts with flange is adopted as a carrier, by changing the process parameters, this study try to find out the best forming condition for the forging parts of magnesium alloy with lower forging load. In addition, through the hardness test and the observation of microstructure of forged parts,the influence of heating temperature of billet and lubricant on the microstructure and strength of forged parts can be clarified. Finally, Artificial Neural Network (ANN) is applied to learn the data obtained from experiments and to predict the experimental result under new combination of process parameters. Confirmatory experiment is carried out to prove the usefulness of the ANN model.
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Su, Cyun-Fong, and 蘇群峰. "Study on the formability of magnesium alloy for valve cover under hot forging process." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/25436346803715738577.
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碩士國立臺灣科技大學
機械工程系
98
The study investigates the mechanical properties and forming characteristics of AZ31 and AZ61 magnesium alloys under hot forging. Firstly, finite element software DEFORM is applied to simulate the deformation behaviors of magnesium alloys valve cover under different process parameters. Process parameters considered in the simulation are materials heating temperatures, lubricants and punch speeds. The optimal forging condition can be obtained from evaluation of the completeness of filling of material in die cavity, forming load and stress and strain distribution. From the hardness distribution, material flow pattern and observation of microstructure of forged parts, we try to find out the factor that influence the formability of magnesium alloys valve cover. Finally, by comparing the analytical results of DEFORM simulation and the experimental results. We try to figure out the method that can manufacture valve cover perfectly with low forging load.
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Lee, Chung-Ham, and 李忠翰. "Study of Hybrid Casting and Forging Process and Mechanical Properties in AZ91D Magnesium Alloy." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/02697551179331628066.
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碩士國立成功大學
材料科學及工程學系碩博士班
92
In this study, castings with stepwise cross section are die cast with AZ91D magnesium alloy. The stepwise cross section has three different thicknesses, which are 15 mm, 10 mm and 5 mm, respectively. The aim of this study is to evaluate how high compression ratio is required to eliminate the porosities inside the preformed castings with various thicknesses and the maximum compression ratios that can be tolerated before these preformed castings fail. Furthermore, the ultimate tensile strength and microstructures of samples of three thicknesses with different compression ratios will be demonstrated. The experimental results of density measurement and tensile test reveal that for AZ91D magnesium alloy, it requires a compression ratio of 41% to eliminate most porosities (porosity content 0.77%~1.6%) in the casting section 15 mm thickness and a maximum compression ratio range of 41%~51% can be tolerated. Besides, it has a better tensile strength of 163 MPa. For the casting section of 10 mm in thickness, it requires 36% of compression ratio to eliminate most porosities (porosity content 0.61 % ~ 0.71 %) and a maximum compression ratio range of 47% ~58% can be tolerated. Besides, it has a better tensile strength about 222 MPa. For the casting section of 5 mm in thickness, it requires 36% to eliminate most porosities (porosity content 0.61% ~ 0.77%) and a maximum compression ratio range of 48% ~56% can be tolerated. Besides, it has a better tensile strength about 213 MPa. The microstructure observations of AZ91D magnesium alloy in the casting section 10 mm thickness showed that participate, Al12Mg17 is spread continuously in the grain boundaries. After the tensile test, the cross-sections of the fractures show that the fracture mode is intergranular brittle fracture. Increasing of compression ratio to 50%, the fracture mode is combined of intergranular and transgranular fracture, resulting into the increase of tensile strength. Then, the observations of fracture morphology in the section 10 mm thickness of 0% compression ratio reveal that some brittle features are at the fracture surface, and the brittle features are invariable when the compression ratio is increased to 50%.
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Lin, Chung-Chuan, and 林忠建. "A Study of Forging Process for AZ31B Magnesium Alloys and development of case forgings." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/21591941862466418089.
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碩士國立高雄第一科技大學
機械與自動化工程所
92
At present time, the manufacturing of the case of Magnesium alloy is almost conducted by die casting process. But the thinner the case is, the more difficulty the die casting process proceeds and the less the yield is. The cost will get higher. However, the forging process is considered as the alternative method to produce the thinner case. In this study, the case of AZ31B Magnesium alloy is used as the vehicle to investigate the forging process technology. The results show that the optimum variables are 450℃ for forging temperature and 400℃ for die temperature. Then, the forging die is designed in according to the results of CAE simulation. After the forging dies are manufactured, the forging stages such as preform, blocking and finishing are conducted and the expected vehicles are finished. So, it is feasible for the design of forging process and forging dies in this study.
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Chang, Feng-Chi, and 張峰旗. "Study of Hybrid Casting and Forging Process in Aluminum and Magnesium Alloys." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/04834116465646666891.
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碩士國立成功大學
材料科學及工程學系
89
Abstract Hybrid casting and forging process combines the advantages of casting and forging processes. It is desirable to cast a near net shape first and subsequently forge it. Comparing with pure casting, the forging part of the hybrid process can eliminate the casting defects, such as air holes and shrinkage porosity, in the casting preform. Comparing with pure forging, the casting part of the hybrid process can reduce the procedure in forging. Basically, hybrid casting and forging process can be approaches in two ways. One is to use forging alloys. In this approach, the concerns are how many holes are created in the casting and how much compression is needed to eliminate all the holes in subsequent forging. The other approach is to use casting alloys. It is then concerned about what the largest compression ratio is before the preform is broken in forging. In this study, castings with stepwise cross section are die cast with 7075 aluminum alloy and AZ91D magnesium. The stepwise cross section has three different thicknesses, which are 15 mm, 10 mm and 5 mm. The first stage is to conduct insufficient filling experiments to validate the accuracy of the mold filling software. The verified mold filling software is then applied to design the die casting die to eliminate air entrapment in die casting. In his study, castings are first made and the shrinkage porosity is examined. Then, solidification simulations are conducted for that casting and Niyama criterion is employed to predict the occurrence of the shrinkage porosity with a prescribed value forε.With the criterion, shrinkage porosity is expected to form when G/√R value at the concerned location is smaller than a specific value,ε. G is the thermal gradient and R is the cooling rate. The value of ε changes when the size of the shrinkage porosity changes. The procedure is iterated with variousεvalues until the predicted porosity is consistent with the observed one. Then the particularεvalue is then designated as the criterion value for that particular size of porosity. The results show that the casting section of 5 mm thickness has rather small porosity because of its small shrinkage rate, 0.1 percent, and its shrinkage size is 0.398 mm. Through cross examination with the simulated results, the ε value is found to lie between 1 and 0.9. For the casting section of 10 mm thickness, it has medium size porosity because its shrinkage is 0.4 percent and its shrinkage size is 0.73 mm and the ε value is between 0.645 and 0.54. For the casting section of 15 mm thickness, it has rather large porosity because its shrinkage is 0.9 percent and its shrinkage size is 1.262 mm and its ε value is between 0.455 and 0.43. The second stage in this study is concerned about forging experiments. The purpose is to determine the minimal compression ratio required to eliminate all the porosities in the casting of 7075 aluminum alloy at 400 oC. The results show that it requires 40 % of compression ratio to eliminate all the air holes in the casting section of 5 mm thickness and the maximum compression ratio it can withstand is between 40 % and 45 %. For the casting section of 10 mm thickness, it requires 50 % of compression ratio to eliminate all the air holes and the maximum compression ratio it can withstand is between 62 % and 66 %. For the casting section of 15 mm thickness, it requires 52 % of compression ratio to eliminate all the air holes and the maximum compression ratio it can withstand is between 52 % and 65 %. The purpose of the forging experiments for AZ91D magnesium alloy is to determine the largest compression ratio the casting can withstand at 200 oC since AZ91D is not a forging alloy. The results show that the casting section of 15 mm thickness can withstand at least 40 % of the compression ratio. It is broken when the compression ratio exceeds 40 %. For the casting section of 10 mm thickness, it can withstand 42 % of the compression ratio. For the casting section of 5 mm thickness, it can withstand 60 % of the compression ratio. 中文摘要 i 英文摘要 iii 目錄 vi 表目錄 viii 圖目錄 ix 第一章 緒論 1 1.1 研究背景 1 1.2 文獻回顧 3 1.2.1 鑄鍛合一之探討 3 1.2.2 鋁合金鑄造及鍛造之探討 3 1.2.3 鎂合金壓鑄 4 1.2.4 數值模擬 6 1.2.5 縮孔模擬 7 1.3 研究目的與內容 9 第二章 理論基礎及數值方法 14 2.1 數值模擬 14 2.1.1控制方程式 14 2.1.2 自由表面的邊界條件 16 2.1.3邊牆的邊界條件 16 2.1.4 系統的分割 17 2.1.5 三度空間下流體的自由表面追蹤法則 17 2.1.6 氣體追蹤粒子方法 18 2.1.7 模擬解析程式模擬過程 18 2.2縮孔的模擬 19 2.2.1 凝固控制方程式 20 2.2.2 縮孔模擬指標 21 2.3鍛造理論 23 2.3.1塑流應力 23 2.3.2體積不變定律 23 第三章 鑄鍛合一實驗 26 3.1 7075鋁合金鑄鍛合一 26 3.1.1 7075鋁合金不足量充填實驗 26 3.1.2 7075鋁合金之模具設計 26 3.1.3 7075鋁合金的壓鑄 27 3.1.4 7075鋁合金壓鑄件的切割 27 3.1.5 7075鋁合金鍛造試驗 27 3.1.6 金相實驗 29 3.2 鎂合金鑄鍛合一 29 3.2.1 鎂合金不足量充填的實驗 29 3.2.2 模具設計 29 3.2.3 鎂合金的壓鑄 30 3.2.4 鎂合金試片的切割 30 3.2.5 鎂合金的鍛造試驗 30 3.2.6 金相實驗 31 第四章 結果與討論 43 4.1 7075鋁合金鑄造及鍛造特性的探討 43 4.1.1 不足量充填實驗與模擬結果 43 4.1.2 壓鑄模具的設計 43 4.1.3 鋁合金的壓鑄件 44 4.1.4 鋁合金鑄件的孔洞分佈 44 4.1.5 縮孔模擬預測 45 4.1.6 7075鋁合金壓縮試驗與密度量測的結果 46 4.1.7 金相的觀察 48 4.2 鎂合金鑄造及鍛造特性的探討 49 4.2.1 鎂合金模具設計與鑄造 49 4.2.2 鎂合金壓縮試驗與密度量測的結果 49 4.2.3 金相實驗 51 第五章 結論 103 5.1 7075鋁合金鑄鍛合一研究之結論 103 5.2 AZ91D鎂合金鑄鍛合一研究之結論 104 第六章 未來研究方向 105 參考文獻 106 表目錄 Table.1-1 7075鋁合金化學組成(wt.%) 10 Table.1-3 AZ91D鎂合金的化學組成(wt.%) 10 Table.1-2 7075鍛造用鋁合金之機械性質 11 Table.3-1 7075鍛造用鋁合金之熱物性質 33 Table.3-2 壓鑄機鑄造條件 34 Table.3-3 AZ91D之熱物性質 38 Table.3-4 鎂合金壓鑄條件 42 Table.4-1 7075之試片一密度對壓縮率的數據表 69 Table.4-2 7075之試片二密度對壓縮率的數據表 76 Table.4-3 7075之試片三密度對壓縮率的數據表 78 Table.4-4 7075之15mm厚的試片密度對壓縮率的數據表 80 Table.4-5 7075之10mm厚的試片密度對壓縮率的數據表 82 Table.4-6 7075之5mm厚的試片密度對壓縮率的數據表 84 Table.4-7 AZ91D之試片A的密度對壓縮率的數據表 90 Table.4-8 AZ91D之試片B的密度對壓縮率的數據表 92 Table.4-9 AZ91D之試片C的密度對壓縮率的數據表 94 Table.4-10 AZ91D之15mm厚的試片密度對壓縮率的數據表 96 Table.4-11 AZ91D之10mm厚的試片密度對壓縮率的數據表 98 Table.4-12 AZ91D之5mm厚的試片密度對壓縮率的數據表 100 圖目錄 圖1-1. 鎂合金熱室及冷室機 12 圖1-2. 鎂合金半固態射出機 13 圖2-1. 在網格(i,j,k)周圍26個網格及其溫度示意圖 25 圖3-1. 7075鋁合金鑄鍛合一實驗流程圖 32 圖3-2. 7075鑄件尺寸圖 35 圖3-3. 7075鋁合金鑄件3D立體圖 36 圖3-4. 650T鍛造試驗機 37 圖3-5. AZ91D鎂合金鑄鍛合一實驗流程圖 39 圖3-6. 鎂合金鑄件之3D立體圖 40 圖3-7. 鎂合金熱式壓鑄機 41 圖4-1. 250g的7075鋁合金充填時模擬與實驗的比較圖 52 圖4-2. 模具模擬圖之最上層 53 圖4-3. 模具模擬圖之中間層 54 圖4-4. 模具模擬圖之最下層 55 圖4-5. 7075鋁合金之鑄件 56 圖4-6. ADC12鋁合金之鑄件 57 圖4-7. 7075鋁合金試片的切割圖 58 圖4-8. 7075之試片一之切割面圖 59 圖4-9. 7075之試片二之切割面圖 60 圖4-10. 7075之試片三之切割面圖 61 圖4-11. 7075鋁合金之圓柱圖 62 圖4-12. ADC12鋁合金之圓柱圖 63 圖4-13. 7075之15mm厚度的試片，模擬與實際鑄件的縮孔圖 64 圖4-14. 7075之10mm厚度的試片(接近15mm厚度的試片的面)，模擬與實際鑄件的縮孔圖 65 圖4-15. 7075之10mm厚度的試片(接近5mm厚度的試片的面)，模擬與實際鑄件的縮孔圖 66 圖4-16. 7075之5mm厚度的試片，模擬與實際鑄件的縮孔圖 67 圖4-17. 7075之試片一密度V.S壓縮率 68 圖4-18. 7075之試片一5mm試片表面鍛壓的情況 70 圖4-19. 7075之試片一10mm試片表面鍛壓的情況 71 圖4-20. 7075之試片一10mm試片表面鍛壓的情況 72 圖4-21. 7075之試片一15mm試片表面鍛壓的情況 73 圖4-22. 7075之試片一15mm試片表面鍛壓的情況 74 圖4-23. 7075之試片二密度V.S壓縮率 75 圖4-24. 7075之試片三密度V.S壓縮率 77 圖4-25. 7075之15mm厚的密度V.S壓縮率 79 圖4-26. 7075之10mm厚的密度V.S壓縮率 81 圖4-27. 7075之5mm厚的密度V.S壓縮率 83 圖4-28. 7075之未經鍛造試片之金像圖 85 圖4-29. 比較7075之鍛造前後晶粒大小的變化 86 圖4-30. 450g鎂合金不足量充填模擬與實驗對照圖 87 圖4-31. 580g鎂合金不足量充填模擬與實驗對照圖 88 圖4-32. 鎂合金sample A壓縮率V.S密度的曲線圖 89 圖4-33. 鎂合金sample B壓縮率V.S密度的曲線圖 91 圖4-34. 鎂合金sample C壓縮率V.S密度的曲線圖 93 圖4-35. 鎂合金之15mm厚度的試片壓縮率V.S密度的曲線圖 95 圖4-36. 鎂合金之10mm厚度的試片壓縮率V.S密度的曲線圖 97 圖4-37. 鎂合金之5mm厚度的試片壓縮率V.S密度的曲線圖 99 圖4-38. 鎂合金AZ91D之金相圖 101 圖4-39. 鎂合金鍛造前後之金相圖 102
17
Hsieh, Hsin-Yi, and 謝馨毅. "A Study of Forging Process for AZ31B Magnesium Alloys of Mobil Phone Case." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/y6dm92.
Full textAbstract:
碩士國立高雄第一科技大學
機械與自動化工程所
96
Generally speaking the magnesium alloy of forming technique the manufacture has technologies and so on compression casting, half solid state forming, forging, ramming in the 3C product outer covering, the compression casting divides into the hot cell diecasting, the cold chamber pressure foundry process, half solid state forming, however work thickness wants thinly, forges for another feasible system regulation. This article mainly take the AZ31B magnesium alloy as a material, studies take the handset outer covering as of the develop products discusses its forging system regulation technology first to collect outer covering of the present handset, induces design of its outward appearance key, discusses feasibility of its forging forming, refers to the domestic and foreign magnesium alloy formation related literature to apply again the material in forging and the mold design, and uses the DEFORM simulation software to form tool of the CAE simulation analysis as forging, discusses the shell feasibilities in forging design and so on preliminary shaping, host forming, may obtain forming of load, the formed stress, the formed strain the blank after the simulation analysis and finally succeeds simulates completely preliminary shaping of tonnage approximately 63 tons the backfill andAnd the main formed tonnage 80 tons not attract approximately put on flaws and so on lack materials, and reference of as the following actual forging parameter. Then again the related achievement which arrives by the CAE simulation analysis separately carries on the forging formation temperature confirmation and the handset outer covering forging confirmation, when formation temperature confirmation material 420℃, mold warm 400℃ is the best formation result is also the formation tonnage approximately 80 tons, in the handset outer covering forging confirmation the preliminary shaping really hammers the formation approximately 80 tons again, advocates the formation really to hammer the formation approximately 90 tons, forms the acquaintance to the DEFORM simulation to be higher than again, in the result knows rationality of the CAE analysis. Finally carries on the size outward appearance confirmation and the section plane analysis, the forging thinnest thickness is the 0.55mm handset outer covering size and the vehicle difference ±0.03mm about, stud size highly and plate thickness compared to 3 above, non-forging flaw, if folds the material, attracts puts on, with the fissure, carries on the section plane understanding interior non-air gate production by the stud spot, the stud attacks the tooth spot entire not to have the flaw. By the above result demonstrated that this research is extremely feasible.
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Lin, Chien-hsien, and 林建賢. "A Study of Forging Process for AZ31B Magnesium Alloys of Shielding Case in Mobile Phone." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/fn5346.
Full textAbstract:
碩士國立高雄第一科技大學
機械與自動化工程所
96
In recent years, the 3C product has been developing towards being light, thin, short and small. The Magnesium alloys has the properties of light weight, high strength to density to ratio, good ability in EMI, quick heat dissipation and is completely recyclable. Their characteristics are compatible to the international trend of light weight, energy effective and environmental friendly. Due to these reasons, Magnesium alloys is acquiring more market share and becoming the most potential material for 3C product. Today, the main manufacturing process of Magnesium alloys product is die casting. However, the thinner the material, the more difficult the process. The surface defects unavoidably would happen while reducing the thickness of the product to a certain level. When the product defectiveness rate increases, the overall cost goes up. The purpose of my study of forging process is to break bottlenecks in the existing process of die casting, and therefore to overcome the product In this article, AZ31B Magnesium alloys is utilized to study the forging process of shielding case in mobile phone. DEFORM, an analysis software,is used as design tool and can effectively check the parameters of each step in entire process. Entire process is consisted of pre-forging and master forging. Pre-forging is to distribute the material, during which lay aside the alloy in 430℃ oven and 300℃ of die temperature. Master forging is to stabilize the part shape, during which lay aside the alloy in 300℃ oven and 200℃ of die temperature. When doing mass production with these parameters, consistent part dimensions can be achieved.
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Yang, Chia-Ling, and 楊家翎. "Stamp-forging Prouss for iPod casing of Magnesium alloy." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/07134945696542855218.
Full textAbstract:
碩士元智大學
機械工程學系
97
The aim of this study is to investigate the properties of stamp-forging process using an example of magnesic iPod casing. In this investigation, DeForm, an engineering software that enables designers to analyze metal forming, was applied in mold-flow simulation to derive the parameters for stamp-forging machining. According to the parameters derived by the numerical simulation, the mold had been created to manufacture the end product. Then, the accuracy of stamp-forging machining was evaluated using the tolerance between the end product and the output result of numerical simulation by DeForm. In this investigation, we got a significant promotion for mold development in both reliability and efficiency. Furthermore, it benefits to down the cost of production and enhance the duration of mold.
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Chen, Chi-Jung, and 陳啟榮. "Study on the flange forging of A6061 aluminum alloy and AZ61 magnesium alloy." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/65504651624431125778.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
91
Abstract This study is to investigate A6061 aluminum alloy and AZ61 magnesium alloy applied in the flange forging process. In the aluminum alloy part, firstly, FEM is used to simulate the workpiece’s warping amount during flange forging, then , based on the simulation results to design the forging dies , finally, verificatory experiments are carried out. According to the test of hardness and analysis of flow line, the work hardening and the fluid phenomenon of a material in the forming process can be obtained. After a series of analyses, workpiece’s warping amount in forging process are expected to be improved by controlling the metal flow during deformation. For the magnesium alloy part, it is mainly discussed that the characteristics of flange forging under different temperatures. Moreover, tests and analyses of hardness, flow line, metallography, composition, and microstructure are taken on finished products after forging . Through these tests and analyses , we try to realize the critical condition of cracking under flange forging and to find out the best forming condition of magnesium alloy .
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Huang, Kai-neng, and 黃楷能. "Study on Forging and Thread-rolling Processes of Magnesium Alloy Screws." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/97296768369940481507.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
99
This study investigated effects of the process parameters on the forging load and metal flow pattern during forging and thread-rolling these two process of LZ91 magnesium alloy small size screw by the finite element analysis. At first, Compression tests were carried out under various forming temperatures to study the flow stress. Then, FEM software DEFORM-2D is adopted to simulate forging and thread-rolling processes of small screw to analyze the formability and parameters. In one of this study, there are two stages in forging process, and found out that up-die velocity, temperatures and friction factors will affect the product quality and appearance; on the other part, it investigated the effect of friction factor and temperature under thread-rolling process, and found out that effective stress, effective strain, metal flow and height of thread will be affected. In addition, conduct forging and thread-rolling experiments by using universal testing machine with the mold self-designed, and MoS2 of lubricant, and comparing the analytical results to verify the suitability and accuracy of FEM for forging process. Finally, according to the analysis result of this study, engineers can take it as reference.
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Wang, Shao-Chun, and 王劭駿. "A Study of Die Design for Press Forging of Magnesium-Alloy Sheets." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/34648891761476199520.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
92
The superior properties of magnesium-alloy attracted attentions from the electronics industry recently. Although the principal manufacturing process of the magnesium-alloy products has been die casting, the press forging has considerable potential because of its competitive productivity and performance. So the press forging process of magnesium-alloys at elevated temperatures was studied in the present study by the finite element analysis and experiments. In the press forging process, the heights of the side wall and the defects on the bottom of the boss called ”flow through phenomenon ” are critical issues. In order to examine the effect of process parameters on these issues, the finite element software DEFORM was employed to simulate the press forging processes. According to the results of simulations, the influence of important process parameters such as the features of parts, friction conditions, temperature, punch shape and the thickness of sheet are obtained. After obtaining the material flow pattern in press forging, a cell phone case is used to investigate the die design technologies in press forging process. A method for die designing is established in this study. The forming process is divided into two stages including perform and finishing. By the forming results, it shows that this forming process is useful to avoid ”flow through phenomenon ” and raise the heights of the side wall. The analyzed results are also verified by experiments. The experimental results obtained in the present study show good agreement with simulations. Besides, different lubricants are tested. Lubricants graphite and MoS2 are suitable for the press forging of AZ magnesium-alloys at elevated temperature. The results of this study can be reference resources for related academic research and can also be used to develop related products for industry production.
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Biswas, Somjeet. "Evolution Of Texture And MIcrostructure During Processing Of Pure Magnesium And The Magnesium Alloy AM30." Thesis, 2010. http://etd.iisc.ernet.in/handle/2005/1258.
Full textAbstract:
Magnesium is the lightest metal that can be used for structural applications. For the reasons of weight saving, there has been an increasing demand for magnesium from the automotive industry. However, poor formability at room temperature, due to a limited number of slip systems available owing to its hexagonal close packed crystal structure, imposes severe limitations on the application of Mg and its alloys in the wrought form. One possibility for improving formability is to form the components superplastically. For this, it is necessary to refine the grain structure. A fine-grained material is also stronger than its coarse grain counterpart because of grain size strengthening. Moreover, fine-grained magnesium alloys have better ductility as well as a low ductile to brittle transition temperature, thus their formability at room temperature could be improved. In addition to grain refinement, the issues pertaining to poor formability or limited ductility of Mg alloys can be addressed by controlling the crystallographic texture. Recently, it has been shown that warm equal channel angular extrusion (ECAE) of magnesium led to reduction in average grain size and shear texture formation, by virtue of which subsequent room temperature rolling was possible. Based on the literature, it was also certain that, in order to make magnesium alloys amenable for processing, grain refinement needs to be carried out and the role of shear texture needs to be explored. Since processing at higher temperature would lead to relatively coarser grain size, large strain deformation at lower temperatures is desirable.
The present thesis is an attempt to address these issues. The thesis has been divided in to eight chapters. The chapters 1 and 2 are dedicated to introduction and literature review on the subject that provides the foundation and motivation to the present work. Subsequent chapters deal with the research methodology, experimental and simulation results, discussion, summary and conclusion.
In the present investigation, two single phase alloys were chosen, the commercially pure magnesium and the magnesium alloy AM30. These materials were subjected to suitable processing techniques, detailed posteriori. A systematic analysis of microstructure and texture for each of the as-processed materials was performed by electron backscattered diffraction (EBSD) using a field emission gun scanning electron microscope (FEG-SEM). Bulk texture measurement by X-ray diffraction, neutron diffraction and local texture measurement by synchrotron X-rays were also carried out. In addition, dislocation density was measured using X-Ray diffraction line profile analysis (XRDLPA). The experimental textures were validated by using Visco-Plastic Self Consistent (VPSC) simulation. The details of experimental as well simulation techniques used in the present investigation is described in chapter 3.
To understand the philosophy of large strain deformation by shear in magnesium and its alloy, free end torsion tests could provide a guide line. Based on the understanding developed from these tests, further processing strategy could be planned. Therefore, a rigorous study of deformation behaviour under torsion was carried out. In chapter 4, the results of free end torsion tests carried out at different temperatures, 250⁰C, 200⁰C and 150⁰C and strain rates, 0.01 rad.s-1, 0.1 rad.s-1, 1 rad.s-1 are presented for both the alloys. In addition to the analysis of stress-strain behaviour, a thorough microstructural characterization including texture analyses pertaining to deformation and dynamic recrystallization was performed. Both pure Mg and the AM30 alloy exhibit similar ductility under the same deformation condition, while the strength of AM30 was more. The strain hardening rate decreased with temperature and increased with strain rate for both the materials. However, the strain hardening rate was always higher in case of the alloy AM30. Large amount of dynamic recrystallization (DRX) was observed for both the alloys.
The initial texture had an influence on the deformation behaviour under torsion and the resulting final texture. The initial non-axisymmetric texture of pure Mg samples led to nonaxisymmetric deformation producing ear and faces along the axial direction, and the final texture was also non-axisymmetric. An examination of the texture heterogeneity was carried out in one of the pure Mg torsion tested samples by subjecting it to EBSD examination at different locations of the surface along the axial direction. The strain induced on the ear portion was maximum, and in the face was lower. This has been attributed to the orientation of basal planes in the two regions.
The axisymmetric initial texture in case of the alloy AM30 led to the formation of axisymmetric texture with no change in the shape of the material. Owing to this simplicity, the occurrence of dynamic recrystallization (DRX) was studied in more detail for this alloy. The mechanism of texture development due to deformation as well as dynamic recrystallization could be tracked at every stage of deformation. A typical shear texture was observed with respect to the strain in each case. Very low fraction of twins was observed for all the cases indicating slip dominated deformation, which was validated by VPSC simulation. It was found that with the increase in strain during torsion, the fraction of dynamically recrystallized grains increased. The recrystallization mechanism was classified as “continuous dynamic recovery and recrystallization” (CDRR) and is characterized by a rotation of the deformed grains by ~30⁰ along c-axis.
After developing an understanding of large strain deformation behaviour of pure Mg and the alloy AM30 through torsion tests, the possibility of low temperature severe plastic deformation for both the materials by equal channel angular extrusion (ECAE) was explored. The outcome of this investigation has been presented in chapter 5. At first, ECAE of pure magnesium was conducted at 250⁰C up to 4 passes and then the temperature was reduced by 50⁰C in each subsequent pass. In this way, ECAE could be carried out successfully up to 8th pass with the last pass at room temperature. A grain size ~250 nm and characteristic ECAE texture with the fibres B and C2 were achieved. The AM30 alloy subjected to similar processing schedule as pure Mg, however, could be deformed only up to 6th pass (TECAE=150⁰C) without fracture. An average grain size ~ 420 nm and a texture similar to ECAE processed pure Mg was observed for this alloy. The difference in the deformation behaviour of the two alloys has been explained on the basis of the anisotropy in the stacking fault energy (SFE) in the case of pure Mg.
Neutron diffraction was carried out to confirm and validate the microtexture results obtained from the EBSD data, while the local texture measurement by synchrotron radiation was carried out at different locations of the ECAE samples to give a proper account of the heterogeneity in texture.
The effect of grain refinement was examined, deconvoluting the effect of shear in improving the strength and ductility using another severe plastic deformation technique, namely multi axial forging (MAF). In this process, the material was plastically deformed by a combination of uniaxial compression and plane strain compression subsequently along all the three axes. The details of this investigation has been presented in chapter 6. By this method, the alloy AM30 could be deformed without fracture up to a minimum temperature of 150⁰C leading to ultra-fine grain size (~400 nm) with very weak texture. A room temperature ductility ~55% was observed for this material.
Finally, a comparison of room temperature mechanical properties of the alloy AM30 was carried out for the ECAE and MAF processed conditions having similar grain size in order to observe the effect of texture formed during both the processes. A similar strength and ductility for both the cases was attributed to the orientation obtained from both the ECAE and MAF, which is away from the ideal end orientation for tensile tests. The final outcomes of the thesis has been summarized in chapter 7.
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Pan, Jie-Wei, and 潘介威. "Novel Process Development for Porous Magnesium Alloy." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/9x9r7w.
Full textAbstract:
碩士國立高雄第一科技大學
機械與自動化工程系先進製造科技碩士班
106
The research and development of the porous materials with lightweight currently focuses on effectively reducing the density but still retaining the characteristics of raw materials. They are getting more and more attention from the related industries due to having some distinguished properties that cannot be achieved by other materials. The manufacturing process of porous metal can be categoried into the melt line and powder line. The former is more suitable for the production of large parts. However, it is very difficult to make small parts because the process is limited by the size of the stirring devices during the process. On the other hand, the advantage of the powder line is suitable to produce the small parts or those parts with the special shape. Powder line produces porous metals using the blowing agent (TiH2, CaCO3, etc.), or the space holder (carbamide, NaCl, etc.). The use of carbamide as space holder through sintering dissolution process to produce porous magnesium is a simple but effective with low cost , short manufacturing cycle and can be mass-produced. Additionally, sintering dissolution process can control the porosity of the porous magnesium more easily. A sintering and dissolution process (SDP) is being developed for manufacturing porous magnesium, where spherical carbamide had selected as the space holder. In this paper, the dominate factors affecting the process quality such as pressure holding time, weight percentage of aluminum, proportion of carbamide, mixing time of powders, ultrasonic dissolution frequency, baking temperature, sintering temperature and sintering time were studied and analysed. The quality characteristics investigated are the uniformity of pores and the compressive strength. Finally, the Taguchi methods coupled with principal component analysis (PCA) are employed in the study for multiple quality characteristics optimization.
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CHENG, HONG YI, and 洪宜承. "Study on the formability of magnesium alloy for Bicycle parts under hot forging." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/6a5u43.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
99
This study investigates the formability of AZ31 and AZ61 magnesium alloy for bicycle parts under hot forging. Firstly, finite element software DEFORM is applied to simulate the deformation behaviors of magnesium alloys bicycle parts under different process parameters. The process parameters considered in the simulation are materials heating temperatures, lubricants and punch speeds. The optimal forging condition can be obtained from evaluation of the completeness of filling of material in die cavity, forming load and stress and strain distribution. The experimental conditions are set according to the optimal simulation results. Hot forging experiments are carried out with heating range from 220℃ to 350℃, different lubricants, punch speeds 0.9mm/s to study the formability of magnesium alloy for bicycle parts. The experimental results are compare with the DEFORM simulation results. The obtained forging loads and completeness of filling are in good agreement with the simulation results. The validity of the simulation model established in this study can be confirmed. Finally, from the measured result of hardness and metallographic observation of forged part, the influence of forming temperatures on the strength and microstructures of magnesium alloy for bicycle parts under forging process can be evaluated.
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Li, Yi-Syuan, and 李易軒. "Study on the formability of magnesium alloy for water pump blades under hot forging." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/59560043932411981549.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
100
This study attempts to conduct simulation and experiment analyses on AZ31 and AZ61 magnesium alloy water pump blades under hot forging, using Taguchi Methods and DEFORM 3D. The four parameters in this study material diameters, lubricities, punch speeds, and forming temperatures are distributed according to the schematization of the Taguchi Methods. The response analyses of the Taguchi Methods helps to sort out the four factors which influence forging loads. When the best combination of parametric values is achieved from the tabulated responses of the Taguchi Methods, the forming loads can be predicted and examined. A comparison between simulation and experiment on the different diameters of magnesium alloys also allows us to identify the factors causing forming defects. The impact of temperature on mechanical properties can be known through hardness analysis and metallographic observation on the end product of AZ31 and AZ61 magnesium alloy water pump blades respectively. Finally, a contrasting analysis between the DEFORM 3D simulation and our experiment shows that processing forging with the best parametric values derived from the Taguchi Methods is desirable in that punch loads can be effectively reduced. The result of this study serves to enhance the efficiency of magnesium alloy production and prolong the lifecycle of die.
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Chen, Hao-cheng, and 陳浩承. "Study on the formability of magnesium alloy for scooter piston head under hot forging." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/89653344480989361069.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
101
This study investigates the formability of AZ31 and AZ61 magnesium alloys used for motorcycle piston head under hot forging. A finite element program , DEFROM , is applied to simulate and analyze the deformation behavior of motorcycle piston head under different combinations of manufacturing parameters. In addition, magnesium alloy rods are adopted in the hot forging experiments. The purpose of this study is to find the optimal deformation conditions for motorcycle piston head by comparing simulated and experimental results. Process parameters considered in this study include material heating temperatures, type of lubricants, and punch speeds. Process parameters are changed to find the optimal deformation condition for the forging of magnesium alloy motorcycle piston heads. Expect to produce the products with low forming load and satisfactory contour. In this study the forged products are carried out hardness test , flow pattern and metallographic observation to identify the factors that affected the hot forging of magnesium alloy motorcycle piston heads. Finally, comparisons are made between the simulated results by DEFROM and that yielded by the piston head forging experiments, to find the forging method that can obtain perfect contour of piston head with lowest load.
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You, Chen-wei, and 游振偉. "Study on the formability of magnesium alloy for valve side cover under hot forging." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/49186518068343976645.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
98
This study investigates the formability of AZ31 and AZ61 magnesium alloy for valve side cover under hot forging. Finite element software, DEFORM, is applied to simulate the forming behaviors. The process parameters of simulation considered in this study are established material mechanical properties, heating temperatures of the sheet, punch speeds, constant friction factor, preform shape of billets. The variation of forming loads and completeness of filling in the die cavity are discussed under different process parameters. The experimental conditions are set according to the optimal simulation results. Hot forging experiments are carried out to study the formability of magnesium alloy for valve side cover. Finally, from the measured result of hardness and metallographic observation of forged part, the influence of forming temperatures on the strengths and microstructures of magnesium alloy for valve side cover under forging process can be evaluated. The experimental results are compare with the DEFORM simulation results. The obtained forging loads and completeness of filling are in good agreement with the simulation results. The validity of the simulation model established in this study can be confirmed.
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Sheu, Fong-Yuh, and 許豐裕. "Analysis of Process Parameters for Non-Isothermal Forging of Titanium Alloy." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/96153325501743798693.
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Xu, Feng-Yu, and 許豐裕. "Analysis of Process Parameters for Non-Isothermal Forging of Titanium Alloy." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/16367358029462762937.
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CHAN, SHUANG-YUAN, and 詹雙源. "Isothermal Sheet Formability of Magnesium Alloy and Grain Refine of Magnesium by ECAE Process." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/06181793031538598665.
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LI, TSUNG-LIN, and 李宗霖. "Study on the formability of magnesium alloy for pulley boss part with rib under hot forging." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/23t8wk.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
99
This study investigates the formability of AZ31 and AZ61 magnesium alloy for pulley boss part with rib under hot forging. Finite element software, DEFORM, is applied to simulate the forming behaviors. The process parameters of simulation considered in this study are constant friction factor, die radius, draft angle and the formability of the rib of the pulley boss part with rib . The variation of forming loads and completeness of shape of pulley boss part with rib are discussed under different process parameters. The experimental conditions are set according to the optimal simulation results. Hot forging experiments with heating range from 220℃ to 350℃, different friction factors, punch speeds 0.9mm/s are carried out to study the formability of magnesium alloy for pulley boss part with rib. Finally, from the measured result of hardness and metallographic observation of forged part, the influence of forming temperatures on the strengths and microstructures of magnesium alloy for pulley boss part with rib under forging process can be evaluated. The experimental results are compare with the DEFORM simulation results. The obtained forging loads and completeness of shape of pulley boss part with rib are in good agreement with the simulation results. The validity of the simulation model established in this study can be confirmed.
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Wang, Pao-Te, and 王寶德. "Study on the formability of magnesium alloy for bearing cover of the car under hot forging." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/93814136005946231551.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
96
This study investigates the formability of AZ31 and AZ61 magnesium alloy for bearing cover of the car under hot forging. Firstly high speed metal test machine of China steel Co. Ltd. is used to carry out the compression tests under different forming temperature and strain rates to obtain the stress-strain curves. Then, the stress-strain data obtained from compression test under different dies are applied to analyze the formability of magnesium alloy for bearing cover of the car under forging by commercial package DEFORM. Besides, hot forgings of magnesium alloy for bearing cover of car are carried out to study the formability of magnesium alloy, and to find the best forging condition. Finally, from the measured result of hardness and metallographic observation of forged part, the influence of forming temperatures on the strength and microstructure of magnesium alloy under forging of bearing cover of car are evaluated.
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周村憲. "Hot Extrusion Process of Magnesium Alloy Sheet Under Converging Die." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/61001003155159072097.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
91
Most parts of Mg Alloys are produced by die casting in industry. In general, products of die casting tend to have inferior mechanical properties compare with the forged parts. Furthermore, SF6, which has a strong global warming potential in environmental issues, is required as a protective gas in the die casting process. It is desirable to form the Mg alloys under hot extrusion having good mechanical properties and without any possible danger to the environment. During the hot extrusion of magnesium alloy, its structure is HCP, which has fewer slide surfaces than aluminum alloy. Experimental results show that if the hot extrusion of magnesium alloy sheets is performed under a die that has a high extrusion ratio of 35.9, and a fixed speed is adopted, all the final products carry defects. Further experiments are performed on the extrusion of magnesium alloy sheets by the multi-speed method , sound sheets can be obtained. In this study, using Taguchi experimental method , the experimental sequence is planned. Through ANOVA technique and from the test results of extruded material we can find the relationship between the process parameters and the mechanical properties of the products. Then the optimal combination of process parameters can be found.
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Wang, Kae-Horng, and 王凱弘. "Studies on Process Parameters for Four-Hammer Radial Forging of Titanium Alloy." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/95762081711427104793.
Full textAbstract:
碩士國立成功大學
機械工程學系
86
Four-hammer radial forging is a relatively complicated process for the plastic forming of metal. It has many advantages over the conventional forging processes, especially the high productivity. However different process parameters must be considered in radial forging due to the special forming kinematics. The purpose of this study is to investigate the influence of these process parameters by using the 2D and 3D finite element code DEFORM to simulate the radial process and compared with the macro-structure of the real product.Through the systematic simulation studies, the critical process parameters, such as the billet temperature left the heating furnace, the reduction of the area and the feed rate of the billet, were identified. The effects of these process parameters on the penetratation of the forging, forging load, and also the stress of die were studied in this thesis.Finally, some useful guidelines for selecting the process parameters of radial forging based on the results of process analysis were obtained.
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Chen, Jia-Sian, and 陳嘉賢. "Formability Analysis of Aluminum Alloy for Bevel Gear under Cold Forging Process." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/8xvb9n.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
99
Gears are one of the most important parts in mechanical facilities due to the high efficiency of transmitting force and motion from one shaft to the other. Those are used widely not only in aviation industry but also automobile industry. However, comparing with traditional metal cutting process, forging process offers mass production and reduces waste of material. Therefore, this study presents the cold closed-die forging process, a novel forming technique gear in forging bevel gear with both numerical and experimental studies. The study could be divided in the following steps: First, finite element method (FEM) was carried out to evaluate punch load and material flow for forming tool design. Second, punch and die were fabricated to perform closed-die forging process based on FEM results. Finally, verification of the load-stroke curve between experimental and numerical results was preformed. The results show that the numerical results are in good agreement with experimental results. The findings provide useful information for the improvement of the design of closed-die forging process.
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Lim, Tiong-wei, and 林長偉. "Quality evaluation of AZ91D recycling magnesium alloy in die-casting process." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/86721732930185342635.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
95
In general die casting factory, large volume of recycling AZ91D magnesium alloy materials were used. Although the recycled manufacturing supplier’s materials meet the standard norm, due to the difference of recycled material used the quality of the die casting parts was influenced widely and the understanding of the causes are limitedly. The main purpose of this research is to understand the influences of recycling AZ91D magnesium alloy to the mechanical property and corrosion resistance of the die casting parts. By choosing three existing reputed brand AZ91D material, to compare with own manufacturing magnesium alloy by using 100% pure magnesium, mixture of 30% pure magnesium with 70% recycling magnesium, mixture of 70% pure magnesium with 30% recycling magnesium, and 100% recycling magnesium. Different testing specimens are made by ingot without fabrication and by die-casting process. Through the analysis of chemical compositions, metallography, tensile strength test, impact test, hardness test and corrosion resistance testing, we try to clarify the characteristic of different combination of magnesium. From the analysis of a large number of test data, we realign that the main compositions like Al, Mn, Zn, Si, Fe, Ni, Cu, etc. which can influence the properties of the die-casting parts. Besides, the pollution of casting oxides, plunger lubrication oil and die release agents during die-casting process and the impurities of flux and residue during smelting are also influence the properties of the parts. To widen the use of all recycling AZ91D magnesium alloy can significantly reduce the manufacturing cost. The results detained in this study can be offered to the recycled material manufacturer and die casting factory for reference.
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Fan, Yu-Hsuan, and 范裕璿. "Study on the formability of magnesium alloy sheet under embossing process." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/61615587814820445359.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
98
This study investigates the formability of AZ31 magnesium alloy sheet when pressing the product with concave and convex shapes by embossing process. Firstly, finite element software DEFORM is applied to simulate the effect of process parameters on forming characteristics under embossing process. Process parameters considered in the study includes die radius, constant friction factor, draft angle and indentation depth of embossing. By the changes of process parameters, the forming loads and completeness of die pattern with concave and convex shapes are discussed. Secondly, take one set of simulated parameters to fabricate an experimental die, embossing experiments are carried out by using magnesium alloy sheet, the experimental results are compared with the simulated results to prove the accuracy of simulation model. Finally, from the measurement of hardness and metallographic observation of embossed part, the influence of forming temperatures on the strengths and microstructures of magnesium alloy sheet under embossing process can be evaluated.
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LI, CHIA-LUN, and 李嘉倫. "A Simulation Analysis of the Metal Flow Line of Cross Joint with Magnesium Alloy AZ31 during Hot Forging." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/15212788680012108979.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系碩士班
101
This study was conducted using DEFORM-3D to simulate the metal flow with different processes by hot forging, using rods to form a cross joint. The distribution of the metal flow of cross joint is analog while the punch are activation with single and counter directions. Analog hot forging forming, the material properties of magnesium alloy AZ31 and interfaces factor between tools are obtained by applying cylindrical compression and ring compression test respectively. The true stress - true strain curve is completed by the cylindrical compressed with different temperatures and strain rates. Applying ring compress test for the height and diameter reduction rate, the constant shear friction factor (m) is obtained from the calibration curve completed Altan etc. The results of simulation are compared with the experimental data to determine the agreement. The cross joint during hot forging using punch action with single and counter directions are simulation to investigate the effect of the metal flow line, affected by the products of the web thickness, diameter, projections, ribs wide, cross the width of the rib round, under different temperatures, strain rates and friction factors. The simulation of the metal flow line of the cross joint of AZ31 magnesium alloy can provide useful forming predicate during hot forging.
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Chang, Shu-Hua, and 張書樺. "Multi-Axes Forging Die and Process Design for an Aluminium Alloy Stem of Bike." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/78825391119817095086.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系碩士班
96
The configuration and functionality of bike are varied in a complex way. As a result, the geometry design of bike components is more and more complex. The conventional forging press with one-direction of action is not able to forge and eject smoothly due to the interference of complicated part geometry with the die cavity. A 3D press with multi-direction of action is able to forge and eject the forming parts with no occurrence of die interference. The production integration and process flow of a 3D press are improved owing to the flexibility of multi-axel movement. In this thesis, design methods of the die geometry, die bearing, and forging process are proposed. FEM simulations were carried out to analyze the forming process; two hollow products of bike were forged using the developed design methodology. A special die configuration design of one cavity coping with two punches was proposed to produce similar product with different dimension of axial length in the same die. The end bar and the stem of bike were adopted to demonstrate the one-step and two-step forging process design. The stem product is not able to be ejected after forging in a one-direction forming press. The one-step and two-step forging processes were designed for a multi-direction 3D forging press. The complicated punch designs were proposed to produce a single specification product in the one-step forging process. The preform and punch designs were proposed to produce multi-specification products in the two-step forging process with a die configuration of one-cavity and two-punch. The multi-step design is not only able to lower the forging and clamping loads but also avoid the folding defects.
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Lin, Cho-Wei, and 林哲偉. "Study on Simulation and Microstructure of Ti-6Al-4V alloy in Upset Forging Process." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/55447213358207099673.
Full textAbstract:
碩士國立中正大學
機械系
90
Ti-6Al-4V is a dual phase alloy consisting of α and β phases. It is used extensively in aeronautical, mechanical, chemical, and medical industries for its excellent mechanical, physical, and chemical properties. The first part of this work is to acquire phase transformation temperature by using the differential thermal analysis. The result showed that the transformation temperature for α+β to β phase was 966℃. The second part of this work was to carry out the upset forging by using Gleeble simulator. The deformation characteristics Ti-6Al-4V alloy in upset forging under isothermal conditions have been investigated in both β and (α+β) phase ranges. Various microstructures and flow curves were obtained from the isothermal upset forging. The third part of this work was to simulate the deformation processes of the upset forging using finite element analysis. The flow curves obtained in second part of this work were then used as constitutive model in the finite element analysis. The results showed that the shape deformation of the model was in good agreement with the deformed specimens after upset forging experiment. Also, the flow curves were applied as a constitutive model for the numerical simulation on the rolling process of Ti-6Al-4V bar. The relationships between resulting temperature/strain distributions obtained from rolling simulation and computer-simulated isothermal upset forging and the microstructure obtained from physical simulation were interpreted. A map of microstructure distribution on the cross section of the forged bar could thus be constructed for a better prediction of microstructure after forging and rolling process.
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Su, Yi-Chung, and 蘇義忠. "Process simulation and die design for aluminum alloy hot forging of a bike component." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/60189551178495075857.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系
98
This study aims at the simulation of the inter-heating forging process of aluminum alloy A6061 for the design of the forging mold (or die) used in the motorbikes, and the commerce software, DEFORM, with finite element method DEFORM is the most extensively utilized (introduction) in current dynamic analysis. Compressing the round rod made of aluminum alloy A6061 with ∮36mm x 115mm by various impulse velocity into the depth of 16mm in 3.0, 1.5, or 0.75 seconds, respectively. This study uses these simulations of forging forming to find the optimal velocity for A6061 concerning the temperature variation and forming effect in material. This study experienced a support rack (or prop stand) of motorcycle front running-board. This experimented part has been mass produced by a good reputation company. This forging process refers to the design and the performing, which is a traditional method to make the aluminum alloy forging mold. and consider the mold needs a continuous testing and modification. Also, In order to prove the software DEFORM of finite element method forges the feasibility analyzed in simulation of the inter-heating forging process of aluminum alloy A6061. Using forging forming analysis designs the coarse mold for the forging and the precision mold for the finish parts. To detect the insufficient filling and the stacking issues frequently encountered during the hard forging process by using DEROM to analyze forging and forming processes. Using the DEFORM software could shorten the developing time of a forging mold from four weeks to two to three weeks. Consider the forming effects from different profiles and locations of coarse mold by forging simulation and analysis to find out the optimal forging process. This study had verified not only the feasibility of the finite element analysis software but also revised the design of the forging mold from this practical product.
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Hadadzadeh, Amir. "Mathematical Modeling of the Twin Roll Casting Process for Magnesium Alloy AZ31." Thesis, 2013. http://hdl.handle.net/10012/7230.
Full textAbstract:
Although Twin Roll Casting (TRC) process has been used for almost 60 years in the aluminum industry, TRC of magnesium is relatively new. In TRC, molten metal is fed onto water-cooled rolls, where it solidifies and is then rolled. Solidification of the molten metal starts at the point of first metal-roll contact and is completed before the kissing point (point of least roll separation) of the two rolls. The unique thermo-physical properties inherent to magnesium and its alloys, such as lower specific heat and latent heat of fusion and larger freezing ranges (in comparison with aluminum and steel) make it challenging for TRC of this alloy. Therefore, a comprehensive understanding of the process and the interaction between the casting conditions and strip final quality is imperative to guarantee high quality twin roll cast strip production. A powerful tool to achieve such knowledge is to develop a mathematical model of the process.
In this thesis, a 2D mathematical model for TRC of AZ31 magnesium alloy has been developed and validated based on the TRC facility located at the Natural Resources Canada Government Materials Laboratory (CanmetMATERIALS) in Hamilton, ON, Canada. The validation was performed by comparing the predicted exit strip temperature and secondary dendrite arm spacing (SDAS) through the strip thickness with those measured and obtained by experiments. The model was developed in two stages, first a thermal-fluid model was developed followed by validation and then a thermal-fluid-stress model was developed. This is the first time a comprehensive thermal-fluid-stress model has been developed to simulate the TRC process for magnesium alloys. The work has led to new knowledge about the TRC process and its effects on magnesium strip quality including the following:
1) Using ALSIM and ANSYS® CFX® commercial packages a 2D mathematical model of thermal-fluid-stress behavior of the magnesium sheet during TRC was successfully developed and validated.
2) An average value of 11 kW/m2°C for the Heat Transfer Coefficient (HTC) was found to best represent the heat transfer between the roll and the strip during TRC casting of AZ31 using the CanmetMATERIALS facility.
3) Modeling results showed that increasing casting speed, casting thicker strips and applying higher HTCs led to less uniform microstructure through thickness in terms of SDAS.
4) Simulations showed the importance of casting parameters such as casting speed and set-back distance on the thermal history and stress development in the sheet during TRC; higher casting speeds led to deeper sumps and higher exit temperatures as well as lower overall rolling loads and lower total strains experienced during TRC.
5) The effect of roll diameter on the thermal history and stress development in the strip was also studied and indicated how larger roll diameters increased the surface normal stress and rolling loads but had little effect on the mushy zone thickness.
6) The correlation between the mechanisms of center-line and inverse segregation formation and thermo-mechanical behavior of the strip was performed. The modeling results suggested that increasing the set-back distance decreases the risk of both defects. Moreover, increasing the roll diameter reduces the propensity to inverse segregation but has a minor effect for center-line segregation formation.
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Chang, Chun-ming, and 張俊明. "A Construction of Process Parameters for Magnesium Alloy Tube Components during Hydroforming." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/3gs9vz.
Full textAbstract:
碩士國立虎尾科技大學
動力機械工程研究所
94
Abstract Due to the light weight and magnetic ray insulation characteristics in magnesium alloy material, it is widely utilized in 3C electronic components and automobile parts. However, its formability is very poor due to the phenomenon of negative rate strain hardening appeared as the deformation in large strain range, so it is usually formed as die casting or casting manner, leads to much scrap and the manufacturing cost is thus increased. The purpose of this study is to construct a series of process parameters for magnesium alloy tube components during hydro-forming and may offer the data resulting from theanalysis as a guideline for magnesium alloy forming in industry. AZ31 magnesium alloy tube is used as the billet for hydro-forming with hydraulic pressure as the main forming power combining with the mechanical auxiliary force to fabricate the tubing products. Finite element software DEFORM-2D/3D is adopted to investigate the forming situations for some in common use fitting tubes, which include T type fitting, rectangle tube, tube bulge forming and irregular tube forming etc.. By changing process parameter, such as punch speed, hydraulic pressure, die-workpiece interface friction and die geometry shape etc. to investigate the material flow of tube fitting, wall thickness variations, and stress and strain distributions. By qualifying the smallest wall thickness of tube fitting requirement and forming sequences completed or not, analysis synthesis and overall judgment to establish an admissible level of process parameter range for complete tube manufacture, or getting optimal process conditions. The results show that suitable mechanical force can help material flow, avoid large strain deformation falling into the area of negative rate strain hardening and enhance magnesium alloy become easy forming, make tube fitting may be formed successfully.
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Chang, Wen-Long, and 張文龍. "An assessment of numerical parameter influencing springback of magnesium alloy forming process." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/17266119679077081429.
Full textAbstract:
碩士國立高雄第一科技大學
機械與自動化工程所
93
The aim of this thesis is to assess of numerical parameter influencing spring-back of magnesium alloy(AZ31) forming process. A Taguchi method is applied to look for the factors resulting minimum spring back of magnesium alloy with experiment and analysis for L die. In this work, numerical parameters influencing spring back have been evaluated quantitatively using experiment and analysis. The parameters important for spring back have been assessed form comparison of the numerical results with the experimental results. The factors of the spring back effect in this study include temperature, the radius of punch, the forming depth, and die clearance with three levels respectively. They have been assessed comprehensively and quantitatively using the Taguchi table, L27. After Taguchi experiment we can find the best levels that are 200 celsius, 3 mm radius of punch, 7 mm forming depth and 0.5 mm die clearance. It has been shown that temperature is the most significant factor influencing spring back. The parameters of the spring back influence in this study include young’s modulus, hardening modulus, anisotropic hardening parameter, and yield stress. Each temperature parameters have been evaluated quantitatively using the Taguchi method in order to reduce deviation. The results of the maximum deviation of predicted angle after spring back form experimental are from 23% down to 10%. The temperature is proportional to the young’s modulus of magnesium, but disproportional to the yield stress.
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Wei, Lin Yi, and 林益瑋. "Study on Hot Extrusion Process and Mechanical Property of AZ31 Magnesium Alloy Sheet." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/31903307543547978161.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
93
In this research, three converging dies (semi angles of die are 20°, 30°, and 40°) are used to investigate the influence of process parameters to the mechanical properties in the hot extrusion of AZ31 magnesium alloy sheets. The process parameters considered in this study are the heating temperature of billet, the temperature of container, the initial speed of extrusion and the lubricant. Orthogonal arrays (L27) is used to arrange the experimental procedures of magnesium alloy sheet extrusion under extrusion ratio 35.9. In addition, the formability of AZ31 magnesium alloy sheet under converging dies will be investigated by using Multi Speed Method (MSM). Since the microstructure of magnesium alloy is Hexagonal Closed-Packed (HCP), there is only a sliding face in the bottom of the structure. Therefore, if we use fixed speed method to extrude the sheet, it is difficult to deform under room temperature, in contrast, when using Multi Speed Method sound sheet can be yielded. Incidentally, the timing of adjusting initial speed of extrusion also affects the formability in hot extrusion process. For the purpose of investigating the tensile strength of extruded sheet, the quality measurement and optimal condition analysis of Taguchi Method are used to obtain the optimal conditions of hot extrusion process in AZ31 magnesium alloy sheet. Moreover, the material temperature, the initial speed of extrusion and the lubricant are changed to observe the effect on formability of extrusion process and mechanical property of extruded sheet. Finally, using the Optical Microscope (OM) to observe the variance of microstructure of extruded parts to clarify the relationship between process parameters and mechanical properties of the products.
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Hsu, Chin-Yu, and 許欽宇. "Improving the hydrogen absorption abilities of magnesium based alloy by polyol process treatment." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/29398523209435941572.
Full textAbstract:
碩士國立臺灣海洋大學
材料工程研究所
96
Our experiment was focus on metal hydrogen storage material to improve hydrogen absorption kinetic. Mg99Ni1-Xwt% Pd (X=0, 0.2, 1) and Mg90Ni10-X wt% Pd (X=0, 0.2, 1) alloys were melted and ball milled under an argon atmosphere. XRD phase analysis reveals Mg2Ni peak in both the melted and ball-milled alloys. The Mg2Ni and Pd have both catalytic and synthetic effects on improving the hydrogen sorption kinetics of the alloy. The results of thermodynamic analysis of magnesium hydride correspond to the values of differential scanning calorimetry measurements. Ball milled Mg99Ni1-Xwt% Pd (X=0, 0.2, 1) and Mg90Ni10-Xwt% Pd (X=0, 0.2, 1) were doped with Pd nanoparticles via a polyol process. Such a process allows a great amount of Pd particles and cluster mounted on the Mg-based alloy powder surface. The hydrogen absorption rate of Mg-based alloy have been improved greatly.
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Sabat, Rama Krushna. "Evolution of Microstructure and Texture during Severe Plastic Deformation of a Magnesium-Cerium Alloy." Thesis, 2014. http://etd.iisc.ernet.in/handle/2005/2956.
Full textAbstract:
Magnesium alloys have poor formability at room temperature, due to a limited number of slip systems owing to the hexagonal closed packed structure of magnesium. One possibility to increase the formability of magnesium alloys is to refine the grain size. A fine grain magnesium alloy shows high strength and high ductility at room temperature, hence an improved formability. In addition to grain refinement, the formability of Mg alloys can be improved by controlling crystallographic texture. Severe plastic deformation (SPD) processes namely, equal channel angular pressing (ECAP) and multi-axial forging (MAF) have led to improvement in room temperature mechanical property of magnesium alloys. Further, it has been reported that by adding rare earth elements, room temperature ductility is enhanced to nearly 30%. The increase in property is attributed to crystallographic texture. Many rare earth elements have been added to magnesium alloys and new alloy systems have been developed. Amongst these elements, Ce addition has been shown to enhance the tensile ductility in rolled sheets at room temperature by causing homogeneous deformation. It has been observed that processing of rare-earth containing alloys below 300°C is difficult. Processing at higher temperatures leads to grain growth which ultimately leads to low strength at room temperature. The present thesis is an attempt to combine the effect SPD and rare earth addition, and to examine the overall effect on microstructure and texture, hence on room temperature mechanical properties. In this thesis, Mg-0.2%Ce alloy has been studied with regard to the two SPD processes, namely, ECAP and MAF. The thesis has been divided into six chapters. Chapter 1 is dedicated to introduction and literature review pertaining to different severe plastic deformation processes as applied to different Mg alloys. Chapter 2 includes the details of experimental techniques and characterization procedures, which are commonly employed for the entire work.
Chapter 3 addresses the effect of ECAP on the evolution of texture and microstructure in Mg-0.2%Ce alloy. ECAP has been carried out on two different initial microstructure and texture in the starting condition, namely forged and extruded. ECAP has been successfully carried out for the forged billets at 250°C while cracks get developed in the extruded billet when ECAP was done at 250°C. The difference in the deformation behaviour of the two alloys has been explained on the basis of the crystallographic texture of the initial materials. The microstructure of the ECAP materials indicates the occurrence of recrystallization. The recrystallization mechanism is identified as “continuous dynamic recovery and recrystallization” (CDRR) and is characterized by a rotation of the deformed grains by ~30⁰ along c-axis. The yield strengths and ductility of the two ECAP materials have been found quite close. However, there is a difference in the yield strength as well as ductility values when the materials were tested under compression. The extruded billet has the tension compression asymmetry ~1.7 while the forged material has the asymmetry as ~2.2. After ECAP, the yield asymmetry reduces to ~1 for initially extruded billet, while for the initially forged billet the yield asymmetry value reduces to ~1.9.
In chapter 4, the evolution of microstructure and texture was examined using another severe plastic deformation technique, namely multi axial forging (MAF). In this process, the material was plastically deformed by plane strain compression subsequently along all three axes. In this case also two different initial microstructures and texture were studied, namely the material in as cast condition and the extruded material. The choice of initial materials in this case was done in order to examine the effect of different initial grain size in addition to different textures. By this method, the alloy Mg-0.2%Ce could be deformed without fracture at a minimum temperature of 350⁰C leading to fine grain size (~3.5 µm) and a weak texture. Grain
refinement was more in the initial cast billets compared to the initial extruded billet after processing. The mechanism of grain refinement has been identified as twin assisted dynamic recrystallization (TDRX) and CDRR type. The mechanical properties under tension as well as under compression were also evaluated in the present case. The initially extruded billet has shown low tension compression asymmetry (~1.2) than cast billet (~1.9), after MAF. Chapter 5 addresses the exclusive effect of texture on room temperature tensile properties of the alloy. Different textures were the outcomes of ECAP and MAF processes. In this case, in order to obtain an exact role of texture, a third of deformation mode, rolling, was also introduced. All the processed materials were annealed to obtain similar grain size but different texture. A similar strength and ductility for ECAP and MAF, where the textures were qualitatively very different, was attributed to the fact that texture of both the ECAP and MAF processed materials, was away from the ideal end orientation for tensile tests. In chapter 7, the final outcomes of the thesis have been summarized and scope for the future work has been presented.
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Chen, You-Rong, and 陳宥蓉. "Effect of different temperature forging process of AZ31/SiCp magnesium matrix composites on their mechanical properties and microstructure." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/89zmkg.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
107
Magnesium-based composites have superior mechanical properties comparing with magnesium alloys by adding a reinforcement such as ceramic particles, fibers or whiskers to the metal matrix. The metal matrix presents form good bonding with the reinforcement. The mechanical properties of the composite then are further improved. In this study, AZ31 magnesium alloy was added with 0.5 wt.% by weight of silicon carbide particles(SiCp) of reinforcement in order to obtain uniform material composition. The prepared magnesium-based composite material is subjected to T4 treatment to eliminate segregation and homogenize the material for subsequent processing. Afterwards, the magnesium-based composites were subjected to secondary processing, and the mechanical properties and microstructure of the magnesium-based composites were investigated and studied using different forging temperatures. From the experimental results, it can be found that adding additional SiCp in the matrix can effectively enhance the material's strength and ductility through grain refinement. Through T4 heat treatment, the β-Mg_17 Al_12 phase can be dissolved in the material and aluminum precipitates. The precipitation of this phase increase the ductility of the material. Two kinds of temperatures forging experiment enables dynamic recrystallization of the material to refine the grain size and increase its ductility and tensile strength. And a small agglomeration phenomenon was found in the composite material added by SiCp, which is presumed to be the main cause of the decrease in the elongation of the material. The experimental results show that the AZ31 magnesium alloy is forged at 150°C to obtain the best mechanical properties (YS: 74.1 MPa ,UTS: 135.9 MPa ,EL%: 3.7%),and the AZ31/0.5 wt.% SiCp forged at 150 °C obtain the best EL%(4.9%), but the YS (83.6 MPa) and the UTS (152.2 MPa) at 220°C were improved.
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Li, Yi-Wei, and 李一葳. "A Study of the Simulation of a Boss and a Rib of a Rectangular Case of Magnesium Alloy AZ31 by Hot Forging." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/71595077631849671411.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系
103
In this study, DEFORM 3D software was used to simulate the prediction of different processes of forming boss and rib by press forging blanks and investigate the influences that defects have on the relative ratio of different parts. Simulations were performed to create flow-through, stacked material, and other defects, as well as other forming states, during the formation of different boss and rib on rectangular cases using press forging. When simulating hot forging, the material properties of magnesium alloy AZ31 were obtained from a cylinder compression test. The availability of the material properties was determined by the true stress-true strain curves, which were obtained from the cylinder compression test at different temperatures and under a fixed strain rate. Subsequently, the material library of finite element simulations were inputted to confirm the usability of the material properties. When simulating boss and rib, press forging simulations were conducted with different relative ratios and different deviations. Then, the influences that different ratios had on flow-through, folding, and changes in forming were analyzed. Finally, different friction factors were employed in the simulations and subsequent formations were observed and used as a reference for assessment. In terms of the influences of the different boss ratios, results showed that a reduction in the relative diameter ratio effectively improved flow-through, and a reduction in height ratio influenced flow-through depth. In terms of the influences of the different rib ratios, results showed that different relative rib heights influences rib fill, changes in rib length ratio influences the difference in height during rib forming, and adjustments to relative rib thickness ratio influences rib fill. In terms of boss and rib deviation, the folding was significantly larger with the increase in deviation. In addition, the opening of the stacked boss changed with different deviation. With the increase in friction factors, the flow-through and folding were reduced during boss forming. The generation of folding was decreased with a reduced height difference during rib forming. Both the height differences in sidewall and the forming load were increased with the increase in friction factors when forming a rectangular frame.