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    Production of Globular Structure of Al A356, Using Both Electromagnetic Stirrer and Gas induced Semi Solid (GISS) Process

    , M.Sc. Thesis Sharif University of Technology yekani, Farnoush alsadaat (Author) ; Aashuri, Hossein (Supervisor)
    Production of semi solid slurry and creating the globular alloy structure is possible in the ways of Electromagnetic stirring and Gas induced semi solid, which are used widely in industrial scale. Because of the weak magnetic field in the middle part of stirrer, this part is being emptied of melt. As a result, The porous graphite cone is used in this part in order to inject the gas bubbles.In this research, the semi solid A356 Aluminum alloy, is produced under different durations and stirring flux using a three phase Electromagnetic stirrer and injection of the Argon gas. Consequently the slurry was transferred to a mold and compacted by a drop weight. By investigating and analyzing the... 

    Parametric Investigation on Microstructure and Mechanical Properties of Ultrasonic Spot welded Aluminium and Copper Sheets

    , M.Sc. Thesis Sharif University of Technology Yosefi, Ali (Author) ; Kokabi, Amir Hossain (Supervisor) ; Abedini, Rezvan (Co-Supervisor)
    Ultrasonic metal welding is a solid state welding process and is widely used in welding the connections of lithium-ion battery batteries in hybrid and plug-in hybrid vehicles. This welding process has advantages over fusion welding processes such as; Shorter time, no heat affected area, optimal energy consumption, cheaper equipment and no harm to the environment. The aim of this study was to investigate the effect and optimization of time, normal pressure and oscillation amplitude parameters in order to achieve the maximum tensile-shear test force and T-peel test in the dissimilar welding of 1050 aluminum and copper (purity above 99.9%). In order to achieve the optimal state of welding... 

    Electrodeposition of Ag-Pd Alloy for Enhancing Corrosion Resistance

    , M.Sc. Thesis Sharif University of Technology Yari, Mohammad Hossein (Author) ; Dolati, Abolghasem (Supervisor)
    Silver is a resistant metal against the oxidation under normal atmospheric conditions, but it reacts readily with sulfur bearing species in the environment and corrodes. Alloying silver with more noble elements, such as Palladium, is a promising approach for increasing corrosion resistance against the sulfur pollutants. The purpose of this research is to develop a plating bath for deposition of Silver-Palladium alloy with acceptable appearance and higher corrosion resistance than pure silver. For this purpose, a bath based on thiosulfate complexing agent was investigated. In this solution, with a bath containing 10 mM of each cation, deposits with palladium content of 6, 11 and 14 % were... 

    The Effect of Thickness and Heat Treatment on Residual Stress of Aluminum 356 Castings

    , M.Sc. Thesis Sharif University of Technology Ganji Moqadam, Omid (Author) ; Ashuri, Hosein (Supervisor) ; Varahram, Naser (Supervisor)
    The purpose of this research is to investigate the residual stresses generates during solidification of a casting part and the effect of casting geometry and thermal treatment conditions on these stresses. The pattern was designed with to arms to ensure tensile tension. CO2 process was used for modeling and due to the high hardness of the mold, it also acts as a constraint and exacerbates the tension. To measure tensions in parts, two methods consist of Hole Drilling, and an innovative method based on heat treatment and dimension change have been used. The results of the two methods show the same values of stress. The Hole Drilling method is a verified and high-precision method, which is... 

    Mechanical Property and Structural Changes of Pure Magnesium and AZ91 Alloy Using ECAP Process

    , M.Sc. Thesis Sharif University of Technology Garmroodi, Peiman (Author) ; Assempour, Ahmad (Supervisor)
    In recent years, severe plastic deformation processes have been widely used to correct the grain size of metals. One of these methods is equal channel angular pressing. In this research, the improvement of mechanical property and structural changes of pure magnesium and AZ91 alloy after the ECAP process are investigated. The mold is made of H13 steel with a 90-degree channel crossing angle and a zero-degree external curve angle. The purpose of this study is to find the smallest average grain size at the optimum temperature on these materials. First, pure magnesium and AZ91 are subjected to the ECAP process at temperatures of 250, 300, 350, and 400 °C to calculate the best operating... 

    Investigation into the Effect of Adding Sr on Microstructure, Mechanical Properties and Biodegradability Behavior of Biodegradable Mg-Zn-Sr Alloys

    , M.Sc. Thesis Sharif University of Technology Gerashi, Ehsan (Author) ; Alizadeh, Reza (Supervisor)
    Biodegradable implants are new generation of implants that require no secondary surgery for their removal. Mg exhibits a great potential to be used as the biodegradable implant. However, mechanical properties and biocorrosion behavior of Mg are not suitable for being used as biodegradable implants. In this study, effects of Sr additions, heat treatments (T4 and T6), and multi-directional forging on the microstructural evolution, mechanical properties and biocorrosion behavior of Mg-4Zn-xSr alloys, and also the effect of hydrothermal coating on the biocorrosion behavior of Mg-4Zn-0.3Sr alloy were investigated. Potentiodynamic polarization and hydrogen evolution methods were used to... 

    Control of Elements Ratio in Alloy Deposition System

    , M.Sc. Thesis Sharif University of Technology Kishani Farahani, Esmat (Author) ; Rashidian, Bijan (Supervisor)
    Nowadays, thin film alloy deposition has much importance. These alloys are used for various opto-electronic device applications such as liquid crystal displays, flat panel displays, plasma displays, solar cells and computer memories. Exact control of elements ratio in alloy is one of the important issues in deposition of thin film alloys. In alloy deposition with electron beam gun method from its elements, uniformity improvement of each layer is a way to maintain elements ratio in different parts of sample. This uniformity has much importance especially in optical coatings such as high quality antireflection coatings, highly selective filters and low loss reflectance coatings. In this... 

    The Effect of Cu Powder during Friction Stir Welding of Severely Deformed Al on the Microstructure and Mechanical Properties

    , M.Sc. Thesis Sharif University of Technology Kiani Renani, Behzad (Author) ; Kokabi, Amir Hossein (Supervisor) ; Kazeminezhad, Mohsen (Supervisor)
    In order to increase the strength of metals such as aluminum, severe plastic deformation processes can be used. Due to the fact that the dimensions of their products are usually small due to limitations, the connection of severely deformed sheets can be considered. Friction stir welding seems to be suitable for this purpose as a solid state process, but due to the significant amount of strain energy stored in this type of sheet, after recrystallization in the stir zone and the surrounding areas often experience severe grain growth. In this research, the 1050 aluminum sheets are severely deformed by constrained groove pressing (CGP) process were subjected to friction stir welding.... 

    Thermo-Mechanical Analysis of Gas Tungsten Arc Welding Process and Effect of Welding Sequence

    , M.Sc. Thesis Sharif University of Technology Kohandehghan , Ali Reza (Author) ; Serajzadeh, Siamak (Supervisor) ; Kokabi, Amir Hossein (Supervisor)
    In this work, mathematical models are employed to predict transient temperature field, fluid flow within the melt zone and distribution of thermal and residual stresses during and after GTAW process. At the first step, fluid flow in the weld pool and transient temperature field within the metal being welded are determined by simultaneously solving the equations of conservation of mass, energy and momentum. To do so, a commercial finite volume base-program, FLUENT, is utilized. In the next step, temperature distribution during cooling as well as resulting thermal and residual stresses are predicted by means of a commercial finite element base program, ABAQUS. The employed models are capable... 

    Comparison of the Effect of Controlled Annealing on Accumulative Roll Bonded 5083 Aluminum Alloy and AZ31 Magnesium Alloy Sheets

    , M.Sc. Thesis Sharif University of Technology Kalani, Amir Reza (Author) ; Akbarzadeh, Abbas (Supervisor)
    Lightweight aluminum and magnesium alloy sheets do not generally possess as much strength as steel sheets and their strength need to be increased by a suitable process such as Accumulative Roll Bonding (ARB). One of the most important limitations of ARB is the low ductility and formability of the sheets produced by this process. In the present research conducted on the 5083 aluminum and AZ31 magnesium alloy sheets efforts have beem made to overcome this limitation by heating up the sheets whether during metal forming process as hot deformation or as distinct controlled annealing process subsequent to the deformation, in order to develop the application domain of the sheets. Results... 

    Designing A Colorimetric Sensor Array Based on Gold, Silver and Gold-Silver Alloy Nanoparticles for Detection and Discrimination of Pesticides

    , M.Sc. Thesis Sharif University of Technology Kalantari, Kimia (Author) ; Hormozinezhad, Mohammad Reza (Supervisor)
    Due to the widespread use of pesticides and their harmful effects on humans and wildlife, monitoring their residual amounts in crops is critically essential but still challenging regarding the development of high-throughput approaches. Herein, a colorimetric sensor array has been proposed for discrimination and identification of triazole fungicides using monometallic and bimetallic silver and gold nanoparticles. Aggregation-induced behavior of AgNPs, AuNPs and Au-AgNPs in the presence of four triazole fungicides produced a fingerprint response pattern for each analyte. Pattern recognition methods, including linear discriminant analysis (LDA) and hierarchical cluster analysis, have been... 

    Application of Dynamics Multi-scale Modeling of Dislocation in Nano-Crystalline Materials

    , M.Sc. Thesis Sharif University of Technology Karimi, Hossein (Author) ; Khoei, Amir Reza (Supervisor)
    Dislocations are one of the most important classes of defects in crystals. They have significant effects on the physical properties of crystals. They could be primarily created during the formation of a crystal or during the loading on specimen. Dislocation’s movement due to stress is the main cause of crystal plasticity. Since dislocation is a change in perfect crystal structure it is possible to identify it in the molecular level. However, the high computational cost of the MD level, has led researchers to using the multi-scale methods. Researchers have used many various multi-scale methods to study dislocations. The method used in this paper is based on energy. Total energy of system for... 

    Design and Manufacture of Friction Stir Spot Welding (FSSW) Machine with Ability of Refilling and Study on Effects of Welding Parameters on Al1100 Joint

    , M.Sc. Thesis Sharif University of Technology Karimpour, Omid (Author) ; Kokabi, Amir Hossein (Supervisor)
    Friction Stir Spot Welding (FSSW) with ability of refilling weld’s keyhole, is one of the new solid state joining processes which have gained many applications, especially in automobile industry. Considering newness of the process, first part of this study has been dedicated to design and manufacture of a FSSW machine which is done entirely by author of this study. Second part was survey on effect of parameters such as Tool rotation speed, Weld time, and Forge time for refilling the hole, on properties of an aluminum joint. After welds were made, specimens were subjected to Lap-shear tensile test, after that, studies on macro and microstructure have been carried out. Generally an increase in... 

    Refilled Friction Stir Spot Joining of Aluminum to Polymer Sheets

    , M.Sc. Thesis Sharif University of Technology Karami Pabandi, Hossein (Author) ; Kokabi, Amir Hossein (Supervisor) ; Movahedi, Mojtaba (Supervisor)
    Today, dissimilar joining of metal to polymer is in increasing demand in automotive and aerospace industries. Conventional methods for dissimilar joining of metal to polymer have limitations such as need for complex system and high surface sensitivity. Therefore, in this study, it has been tried to join pre-drilled aluminum sheets to polymer, based on frictional heat and creation of interlocks between the base parts. Refilling the hole is the main advantage of the method. AA5052 sheet with 2 mm thickness and polypropylene reinforced with 3 wt% short-carbon-fiber composite were used as primary materials. The effect of hole diameter in 4 and 5.5 mm and tool rotational speed in 500, 1000, 1500... 

    Harvesting Energy from Magnetic Shape Memory Alloys in Plannar Loading

    , M.Sc. Thesis Sharif University of Technology Karamian Manesh, Mohammad Javad (Author) ; Sayyadi, Hassan (Supervisor)
    Harvesting energy by magnetic shape memory alloy has many advantages against other various methods which harvested from environmental vibrations and has been considered due to high long longevity, large strain amplitude and good performance in low frequencies. These materials can display up to % recoverable strain in response to the application of a magnetic field or compressive mechanical stress. Microstructure of these materials changes under applying mechanical loading and/or magnetic field which cause magnetic vector rotating in magnetic domain. Change in magnetization of these materials, lead to harvesting energy by considering Faraday's law of induction. The model of this... 

    Production of Zirconium based Amorphous Alloy by Mechanical Alloying and Sintering Al-based Composite with Amorphous Particles

    , M.Sc. Thesis Sharif University of Technology Karami, Soleyman (Author) ; Pourazarang, Kazem (Supervisor) ; Abachi, Parvin (Supervisor)
    Production of copper-zirconium amorphous alloys by mechanical alloying and the process of changing crystal structure to amorphous, was examined. The amount of progress of amorphization has been checked by x-ray analysis after different hours of milling. By increasing the percentage of zirconium in this type of alloy, the process of amorphization has been improved. But There is a limiting factor which is due to the tendency of zirconium to produce oxide and nitride phase. Also, the effect of excessive elements on crystal structure changing has been checked. Hence, adding elements like nickel or aluminum has a different effect on the process of amorphization. adding aluminum to the system... 

    Investigation and Optimization of Ni-P-Zn Electroless Alloy Coatings

    , M.Sc. Thesis Sharif University of Technology Kordijazi, Amir (Author) ; karam, SaeedAllah (Supervisor) ; Dolati, Abolghasem (Supervisor)
    An optimization condition for obtaining Ni-Zn-P electroless alloy coating has been developed. The sulphate bath with sodium hypophosphate as a reducer and sodium citrate and ammonium chloride as complexing agents were used. The effect of variation in the pH level , temperature , time of deposition and reactants concentration on stability of bath, coating composition, microstructure, microhardness and corrosion resistance of coatings was investigated. The composition of coatings was obtained by using the EDAX analysis. To investigate coating morphology, SEM images were taken and to study the corrosion behavior of coatings potentidynamic polarization, Electrochemical Impedance Spectroscopy... 

    Improvement of Mechanical Properties of a Mg-Zn alloy using the Micro Alloying Elements

    , M.Sc. Thesis Sharif University of Technology Cheraghi Heyvedi, Hamid (Author) ; Karimi Taheri, Ali (Supervisor)
    The development of new wrought magnesium alloys for automotive industry has increased in recent years due to their high potential as structuralmaterials for low density and high strength/weight ratio demands. However, the poor mechanical properties of the magnesium alloys have led tosearch a new kind of magnesium alloys for better strength and ductility.In this research,a new type of magnesium alloy based on Mg-Zn-Si-Ca system has been developed using the permanent gravity casting process. For comparison, an alloy without Siby the same method was also produced. The effects of trace Si addition on the microstructure and mechanical properties in magnesium alloy with composition of... 

    An Investigation on the Fatigue Behaviour of Friction Stir Welded Aluminum 7075 Alloy Sheets

    , M.Sc. Thesis Sharif University of Technology Chaychi Maleki, Arash (Author) ; Kokabi, Amir Hossein (Supervisor) ; Ekrami, Ali Akbar (Supervisor)
    The purpose of the present study was to investigate the effects of friction stir welding parameters on the fatigue life of friction stir welded sheets of Aluminum 7075 alloy. The welding process was carried out under three different rotational speeds and three different welding speeds and specimens were extracted transversely to be used for rotating-bending fatigue tests. Optical microscope and SEM images were used respectively for studying the microstructure of the weld zone and fractography. It was the indicated that an increase in the welding speed or a decrease in the rotational speed will result in an increase in the fatigue life  

    Investigation of Hot Cracking Phenomena in Fusion Welding of High-Strength Aluminum Alloys and the Effect of Friction Stir Processing (FSP) Pre-Treatment on the Weldability of 7075 Aluminum Alloy

    , M.Sc. Thesis Sharif University of Technology Pirjamadi, Alireza (Author) ; Pouranvari, Majid (Supervisor) ; Movahedi, Mojtaba (Supervisor)
    High-strength aluminum alloys are widely used in various industries; however, their usage is limited to solid-state welding or mechanical joints due to their low weldability. The main metallurgical challenge of alloy 7075 welding is hot cracking. Thus, the mentioned alloy is introduced as a "non-weldable alloys" category. In this study, the PMZ was investigated, and it was shown that precipitations play an essential role in intensifying the phenomenon of partial melting. On the other hand, the result of the mechanisms activated in the PMZ, called the "L" region, occurs in the grain boundaries during welding. Welded plate with FM1050 causes liquation cracking, while Welded plate with FM4043...