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Evaluation of Structure of Powder-thixoformed A390 Alloy
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Hypereutectic A390 alloy has some exclusive specification among aluminum alloys because of its' excellent properties such as high wear resistance and low thermal expansion. In this research powder-thixoforming method, a compilation of powder and thixoforming methods is used for production of parts. In this method gas atomized powder of pre-fabricated alloy was consolidated by hot pressing under argon atmosphere and converted to an acceptable feedstock for thixoforming stage. The feedstock is reheated to semi solid region and rapidly transferred to a injection sleeve with central runner. The semi-solid feedstock is injected in a step die by a hydraulic press of 1 m/s ram speed. According to...
Evaluation of Porous NTI SMA Formation Mechanism, Pore Characteristics and Thermo-Mechanical Properties Produced by Power Metallurgy for Biomedical Application
, M.Sc. Thesis Sharif University of Technology ; Sadrnezhad, Khatiboleslam (Supervisor)
Abstract
Porous NiTi specimens were produced by elemental nickel and titanium powders and two different temporary space-holder consisting of NaCl and urea and conventional sintering method. Pore characteristic and morphology of porous NiTi specimens was investigated by optical and electron microscopy. Microstructure of specimens was probed using XRD and SEM. Suitable pore distribution and size for biomedical application was obtained using temporary space-holder method. Porosity content increases with increasing space holder powder. At 70 volume percent space-holder, best pore size and distribution with fully open pores, in size 200-500 µm, was obtained and pores are interconnected that suitable for...
Molecular Dynamic Simulation of Metal and Ceramic Nanopowder Compaction Process and Investigation on Effective Factors
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
In present research forming process of nanopowders, which is a part of powder metallurgy was investigated by molecular dynamics method. Powder metallurgy is a relatively new method for production of industrial parts by pouring powder into die and compaction to desired density. One can reach parts with higher quality and strength by decreasing size of powder’s particles and entering the nano scale. Particle with smaller size have higher specific surface and due more intensity to react. Classic methods for investigation of this process don’t cover the atomic scale effects, so using newer procedures such as molecular dynamics is highly recommended. In present research, at first compaction of...
Study of the Effects of Powder Dispensing Mechanism on Selective Laser Sintering Process
, M.Sc. Thesis Sharif University of Technology ; Movahhedy, Mohammad Reza (Supervisor)
Abstract
Additive manufacturing (Simply called A.M.) is a group of manufacturing technologies that is developing rapidly and is being used widely in some industries like car manufacturing, Aerospace and producing Biomedical devices, In a way that some researchers believe that A.M. methods will change the future of manufacturing. One of the most important A.M. techniques is the Selective Laser Sintering (SLS) method that is mostly used in industrial applications. A SLS machine has a lot of sub systems and mechanisms that have key role in the Laser Sintering process. One of the mechanisms of SLS machine is the Powder Dispensing mechanism that produce layers of unsintered powder as thin as 100 microns...
Investigation of the Effect of Temperature on Wear Behavior of 2024Al and 2024Al-20vol.%SiCp Composite
, M.Sc. Thesis Sharif University of Technology ; Seyyed Reihani, Morteza (Supervisor)
Abstract
In this research, friction and wear behaviors of 2024 Al and 2024 Al-20 vol.% SiC composite -prepared by powder metallurgy method- were investigated in the temperature range 20- 250°C. Dry sliding wear tests were conducted at a constant sliding velocity of 0.5 m/s, an applied load of 20 N, and a sliding distance of 2500m using a pin-on-disc apparatus. Some of the wear tests were carried out with artificially aged specimens in order to determine the aging effects. Worn surfaces and wear debris were also examined by using SEM, EDS and XRD techniques. All specimens showed a transition from mild to severe wear above a critical temperature. In the mild wear regime, the wear rate and the friction...
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor) ; Seyed Reihani, Morteza (Supervisor)
Abstract
In this research, wear behaviors of 6061Al and 6061Al-20 vol% SiC composite -prepared by powder metallurgy method- were investigated in the temperature range 25- 200°C. Dry sliding wear tests were conducted at a constant sliding velocity of 0.34 m/s, an applied load of 20 N and 50N, and a sliding distance of 2450m using a pin-on-disc machine test. Some of the wear tests were carried out with artificially aged specimens in order to determine the aging effects on wear rate of composite. Worn surfaces and wear debris were also examined by using SEM and EDS techniques. Also for determining the effect of age hardening treatment on wear behavior of composite, specimens were solution treated at...
Producing Cu-TiB2 Nano Composite Using Powder Metallurgy Route and Study on its Mechanical and Physical Behavior
, M.Sc. Thesis Sharif University of Technology ; Pourazrang, Kazem (Supervisor) ; Abachi, Parvin (Supervisor)
Abstract
In applications such as high duty sliding contacts and other electrical components requiring good electrical- and thermal-conductivity, proper mechanical wear resistance in combination with arc erosion resistance are required.The Cu/TiB2 nano-composite seems to be a good candidate for such cases. At present work TiB2 nano-particles has been selected as reinforcement, due to its valuable properties, i.e., high melting point (2850 - 2900 °C), low linear CTE (8.10 µmm-1 °C-1), thermal conductivity (60.0 - 120 W/m-K) as well as low specific electrical resistivity (10 - 30 μΩ.cm) and high hardness (25-35 GPa HV). Additionally, there are limited articles which have focused on evaluation of...
Finite Element Modeling of Particle Distribution in Al/Powder Composite Sheets Processed by ARB for Manufacturing Aluminium Foams
, M.Sc. Thesis Sharif University of Technology ; Akbarzade, Abbas (Supervisor)
Abstract
In this study closed cell aluminum foam was manufactured through accumulative roll bonding (ARB). In this method, aluminum AA1050 strip was used as the matrix and calcium carbonate was selected as blowing agent powder. The strips were roll-bonded with reduction of 50% during each pass. The produced composite was then subjected to different foaming conditions in order to achieve foams with maximum porosity. Subsequently, influences of content of the blowing agent, time, pressure, number of rolling passes and heating rate on the percentage of porosities were evaluated. In optimum condition quantity of the blowing agent, foaming temperature, holding time and number of ARB passes were equal to 1...
Study of the MBR System for the Removal of Ethyl Benzene and Styrene from Petrochemical Wastewater and Process Optimization by Reducing Membrane Fouling
, Ph.D. Dissertation Sharif University of Technology ; Shayegan, Jalaloddin (Supervisor)
Abstract
In this thesis was investigated the effect of solid retention time (SRT), Hydraulic retention time (HRT), activated carbon and suspended carrier on styrene and ethylbenzene biological removal and also on membrane fouling. In addition to the typical analysis (COD, MLSS, MLVSS, and SVI), the flocculation ability, sludge particle size distribution (PSD), FTIR analysis, excitation-emission matrix (EEM) fluorescence spectroscopy, soluble microbial product (SMP), extracellular polymeric substance (EPS), microscopic observations, microbial activities, microorganism population, and filamentous bacteria are considered to determine sludge characteristics. This study was done in five sections: in the...
Modeling and Analysis of the Powder Deposition Mechanisms of Selective Laser Sintering Process
, M.Sc. Thesis Sharif University of Technology ; Movahedi, Mohamad Reza (Supervisor)
Abstract
Selective laser sintering is a technique which uses a laser as the power source to sintering some selected points at a bed of powder in order to create a solid structure. In this research the SLS mechanisms of powder deposition is simulated and surface smoothness and layer density created by each mechanism is computed. For this purpose roller, blade and hopper mechanisms are simulated. For this simulation, polyamide 12 (PA2200) which is a common material is used. In this simulation at first powder specifications are extracted according to the references and for particle shape instead of using the spherical particle shape we use a certain shape that is more close to reality which created by...
An Investigation into the Microstructure and Mechanical Properties of Biodegradable Magnesium Alloys Composite-carbon Nanotube Produced by the Mechanical Alloying and Powders Pressing Processes
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
Properties of biomaterials, especially in application as planting, can be controlled and optimized by alloying and hardening sedimentation. In recent years, the study on the simultaneous improvement of mechanical properties, toughness and corrosion behavior of magnesium composite by carbon nanotubes (CNTs) is very limited. In this study, the behavior of mechanical properties and corrosion of magnesium alloy composites with different percentages of CNTs have been investigated. The production of magnesium alloy composite by powder metallurgy and aging process have been used as effective methods for improving mechanical properties and increasing the corrosion resistance of magnesium alloys. For...
Feasibility Study of Services of Metal 3D Printer in Iran's Industry
, M.Sc. Thesis Sharif University of Technology ; Mostafavi, Mostafa (Supervisor)
Abstract
One of the best ways to overcome the weaknesses of technology services in different industries is right technology transfer with feasibility in the country. 3D painters have been recently widely used industrially in different countries. The 3D printer is one of the new emerging technologies, enabling the production of every 3D objects with any complexity. 3D printing has provided the possibility of producing, in fastest, more economics and regardless of those complexities. By transfer of this kind of technology and proper management, a huge transformation can created in all industries and factories. To do this, there are several technologies of 3D printing, that each of them used in various...
Experimental Investigation of Henna powder as an Additive to Drilling Fluid
, M.Sc. Thesis Sharif University of Technology ; Masihi, Mohsen (Supervisor) ; Shadizadeh, Reza (Supervisor)
Abstract
A critical property in designing drilling fluids is the concerns for environmental damages and cost efficiency of mud additives used to complete a well safely and economically. Designing drilling fluids for harsh environments such as high temperature, high salinity formation water, lime and cement contamination demands proper selection of deflocculant (thinner) materials to achieve a successful drilling operation. This study presents a novel thinner material that satisfies the goal of an environmentally and economically acceptable mud in drilling lime contamination areas where drilling carbonate formations with high concentration of calcium ions tends to flocculate clay particles in...
Experimental Study and Simulation of Ultrasonic Vibration Effect on Powder Spreading in Selective Laser Sintering Process
, M.Sc. Thesis Sharif University of Technology ; Movahhedi, Mohamadreza (Supervisor)
Abstract
Selective laser sintering is an additive manufacturing technique based on fusion of powder bed, wherein after spreading a powder layer, a focused laser beam directs onto selected points of powder bed to fuse powder particles together. This process is repeated layer by layer until the final part is created. Although utilization of blade as a conventional powder spreading (CPS) mechanism has a good compression ability, the fixed contact line between blade and powder bed surface results in improper powder flowability and increasing shear forces applied on underneath layer. In this study, in order to obtain the basis for conducting practical experiments, discrete element simulation of powder...
The effect of Cobalt Replacement by Nickel on Microstructure, Physical and Mechanical Properties of WC-Co Hardmetals
, M.Sc. Thesis Sharif University of Technology ; Pourazerang, Kazem (Supervisor) ; Abachi, Parvin (Supervisor)
Abstract
WC-Co hardmetals that are produced through powder metallurgy rout are vastely used as wear resistant parts. In these materials hard particles of wolfram carbide are embodied in a cobalt binder. Because of their high hardness and adequate toughness, hardmetals have found wide range of applications in cutting tool industry. During the last decades a number of researches have been carried out to improve their mechanical and wear properties by different binders and carbide particle sizes. Because of high hardness, Tungsten carbide has a good wear resistant. It has very low thermal expansion coefficient and high wetting ability with molten metals. Unlike high hardness, it has limited toughness....
Production and Evaluation of Fracture Behavior of Al-Dra Laminated Composites
, M.Sc. Thesis Sharif University of Technology ; Bagheri, Reza (Supervisor) ; Seyyed Reihani, Morteza (Supervisor)
Abstract
Particulate ceramic reinforced aluminum matrix composites have high specific strength and stiffness; however, low fracture toughness and deformability have restricted their industrial applications. Among the methods introduced to overcome this shortcoming is fabricating the layered composites which contain alternative layers of aluminum (Al) and discontinuously reinforced aluminum (DRA). In this study, two different routes; i.e., "Powder extrusion - Casting - Rolling" and "Powder extrusion - Roll bonding" were employed to produce layered Al-DRA composites. After production of Al6061/SiCp composites via hot powder extrusion, mentioned processes were utilized to make DRA-Al-DRA laminate. In...
Effect of iron Powder in Electrical Conductivity of Concrete
, M.Sc. Thesis Sharif University of Technology ; Joghataie, Abdolreza (Supervisor)
Abstract
Performance and mechanical properties of concrete such as tensile strength, compressive strength, conductivity, etc change with creation and emission of cracks. As health monitoring of important structures is a vital subject that demands a large amount of budget annualy. Studying problems and disadvantages of concrete is one of the most important branches of research.
There are many ways to detect damage in concrete. Electrical resistance method that has been used in this thesis. In this study, an instrument called Risistivity Meter is used to measuring the electrical conductivity. This instrument measured the electrical conductivity, that it can be appropriate way to detect cracks...
There are many ways to detect damage in concrete. Electrical resistance method that has been used in this thesis. In this study, an instrument called Risistivity Meter is used to measuring the electrical conductivity. This instrument measured the electrical conductivity, that it can be appropriate way to detect cracks...
An Investigation on Microstructure and Mechanical Properties of TLP Bonded Al/SiC Composite Using Powder Technique
, M.Sc. Thesis Sharif University of Technology ; Ekrami, A.A (Supervisor) ; Bagheri, REZA (Supervisor)
Abstract
In this research Al6061-SiC composite bonding was done by transient liquid phase method using powder copper intermediate layer. In the first stage feasibility of making this junction in ambient condition was studied. In order to find process optimum temperature, experiments were performed in 560°C, 570°C, 580°C and 590°C for 2 hours. Optical microscopy, scanning electron microscopy and EDS analysis were utilized for this study. Moreover, shear strength determination test was done to assess and compare mechanical properties and also to determine the optimum bonding temperature.
In second stage, base composite and bonded specimens were homogenized in 530°C for 5 and 10 hours. Effect of...
In second stage, base composite and bonded specimens were homogenized in 530°C for 5 and 10 hours. Effect of...
A Study on Application of ECTFE Powder Coating Technique in Nuclear Industry
, M.Sc. Thesis Sharif University of Technology ; Samadfam, Mohammad (Supervisor)
Abstract
At a unit in zirconium production plant under the supervision of Soure Co. nuclear grade zirconium is produced. In the process it is required that hafnium get separated from Zirconium. Zirconium and hafnium separation are performed by nitric acid (4N) and hydrochloric acid (4N). This isolation environment is considerably corrosive and damaging for the equipment. Powder coating is one of the solutions to deal with the corrosion. To do so, electrostatic powder coating method was used for ECTFE polymer. After the coating, according to spark test, roughness analysis, thickness, elasticity and adhesion; temperature and time of the spraying and the spraying of top coating was determined. In...
Transient Liquid phase Bonding of Low Carbon Mangenese Steel to Austenitic Stainless Steel by Pure Cu Foil
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor) ; Seyyed Reihani, Morteza (Supervisor)
Abstract
In the present research, transient liquid phase bonding of dissimilar st52 low carbon manganese steel to 304 stainless steel by pure Cu foil, in induction furnace and SIC furnace, was investigated. Samples were bonded in induction and SIC furnace at 1150 0C for different bonding times. Samples were then cut transversely and cross section of samples was examined by optical and scanning electron microscope. Complete isothermal solidification time was more than 9 hours and 90 minutes for SIC and induction furnace, respectively. Micro hardness and shear strength tests were done on samples bonded in optimum condition. Shear strength of none homogenized samples which had been bonded in SIC...