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aluminum-alloy-a356
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Wear Behavior of the Nanostructured A356 Aluminum Alloy Induced by Severe Shot Peening
,
M.Sc. Thesis
Sharif University of Technology
;
Farrahi, Gholamhossein
(Supervisor)
Abstract
Wear is the most important cause of surface damage occurs by direct contact of surfaces. Increasing the quality and strength of surface against different kinds of destructive phenomena is significant in manufacturing of mechanical parts. Surface nanocrystallisation can improve the surface protection against wear and can be done by lazer beam and shot peening. In this investigation by sever shot peening process the surface of A356 Aluminium alloy transforms to nanocrystal structure. The dry sliding wear and friction behaviors of A356 Aluminum were evaluated using a pin-on-disk apparatus at ambient conditions. The stationary diameter of 5mm stainless steel pin produced a wear track (scar) on...
Semi Solid Rheocasting of A356 Aluminum Alloy by High Speed Injection
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Aluminum is the lightest industrial element after magnesium. As a result, aluminum alloys have many industrial usages because of their high specific strength. Semisolid casting is one of the processes that is capable of producing aluminum alloys with high mechanical properties. In this process, there are a wide variety of methods to prepare semisolid slurry, one of the best ways of which to produce globular structure is electromagnetic stirrer. In this research, the semisolid slurry of A356 aluminum alloy is fabricated by electromagnetic stirrer under different conditions of stirrer intensity current, stirring time and pouring temperature. Then the fabricated semisolid slurry is injected...
The Effect of Thickness and Heat Treatment on Residual Stress of Aluminum 356 Castings
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hosein (Supervisor) ; Varahram, Naser (Supervisor)
Abstract
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...
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 ; Aashuri, Hossein (Supervisor)
Abstract
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...
Effect of Grain Refining, Cooling Rate and Modification on Shrinkage Porosities in A356 Aluminum Alloy
, M.Sc. Thesis Sharif University of Technology ; Varahram, Naser (Supervisor)
Abstract
In this study, the influence of eutectic modification, grain refining and cooling rate on amount of shrinkage porosity in aluminium A356 alloy were investigated. Modification process for changing the morphology of eutectic silicon from needle like to fibrous like, use in aluminium – silicon alloys. This process often leads to increasing porosity in melt and affect harmfully on mechanical properties. For studying shrinkage porosity, the melt degassed completely to minimizing amount of gas in the melt. For modification, strontium in Al-10Sr master alloy and sodium in NaF salt used and for grain refining Al-10Ti and Al-5Ti-1B master alloys used. To study the effect of cooling rate, three mold...
Effect of Electromagnetic Vibration and Alternative current on A356 Microstructure
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
A356 Aluminium alloy has an abundant application in the aerospace and automobile industries. One of the most important problems of the alloy is in it’s microstructure after solidification with long dendrite grain of Aluminium.It is stated that solidied grains can be refined by electromagnetic vibration and an alternative electric feild applied simultaneously. To make electric field, electric current passed through the specimen. In order to change in microstructure, electromagnetic vibration was used. Then the effect of intensity of electromagnetic field and alternative electric current on microstructure was examined.Grain refining carried out at electric current 80A and magnetic flux of 13,...
Semisolid Stir Joining of AZ91 Alloy to A356 Alloy
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Today, Mg and Al as the widely used metals, make a special contribution to automotive, electronics and aerospace industries. Increasing the application of alloys of these metals, has extended the demand for reliable joint between alloys of these two metals. The main problem with the dissimilar joining of A356 alloy and AZ91 alloy is hard and brittle intermetallic compounds formation such as Mg17Al12 and Mg2Si which brings about welding strength reduction. By far, a large number of researches about dissimilar joining of AZ91 alloy and A356 alloy in semi-solid condition have not accomplished. In this method two fragments, one from AZ91 alloy and another from A356 alloy among which was a 2...
Investigation of Semisolid Microstructure of Aluminum A356 Alloy Prepared by Electromagnetic Stirring and Gas Induction
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Diverse methods of producing semi-solid metal have been the subject of extensive study for the past 40 years. Among all these methods, electromagnetic stirring (EMS) and gas induced semi solid (GISS) have been used on a commercial scale. Considering the fact that in previous studies the intensity of electromagnetic field in the central part of the stirring chamber was negligible, a hollow cylinder with an almost pure iron core was utilized in the central part of the chamber in order to intensify the electromagnetic field in the center and to introduce gas bubbles into the melt. Aluminum A356 alloy was stirred by a three phase electromagnetic stirrer and introduction of gas bubbles under...
Effects of Oxide Film on Tensile Properties of A356 Aluminium Alloys
, M.Sc. Thesis Sharif University of Technology ; Davami, Parviz (Supervisor) ; Varahram, Nasser (Supervisor)
Abstract
Since mechanical properties of cast Al-Si-Mg alloys are directly influenced by microstructural defects, understanding the characteristics of these defects and any interaction between them is important for improving the properties of castings. This study investigated the effect of the most common defects normally found in cast aluminium alloys namely, double oxide films, Fe-rich phases and prosity. A different level of each defect was introduced into castings to investigate their effects on tensile properties of A356 Alloy. Differents casting condition experiment produced different entrained oxide film, Fe-rich phases and porosity caused by shrinkage content, from low to high, were tested...
An Investigation into the Effect of Solidification Rates and Melt Filtration on the Tensile Properties of A356 Castings
, M.Sc. Thesis Sharif University of Technology ; Varahram, Naser (Supervisor) ; Davami, Parviz (Supervisor)
Abstract
A356 castings show different characteristics during tensile tests. This behavior emanates from casting defects such as pores and double oxide films. These defects lead to quick and unexpected failure during tensile tests. Secondary dendrite arm spacing of primary α phase, eutectic phase, volume fraction of pores and oxide films are the characteristics that affect the tensile property. N this study the effect of changing two characteristics on the microstructural constituents is investigated. The first one is cooling rates, and the second one is melt filtration by using different filter in the runner. According to the tensile properties, the effect of these changes on tensile properties...
An Investigation into the Microstructure and Mechanical Properties of Rheoforged A356 Alloy After Severe Plastic Deformation
, M.Sc. Thesis Sharif University of Technology ; Kazeminezhad, Mohsen (Supervisor) ; Aashuri, Hossein (Supervisor)
Abstract
Several studies are already on severe plastic deformation of wrought and cast aluminum alloys. Among these studies, no evidence of applying severe plastic deformation on the structure of rheocast or rheoforgedaluminum alloy can be found. So, in this research A356 alloy with globular structure was achieved using electromagnetic stirring and rheoforging. The optimum condition of globular structure with high sphericity was achievedafter holding the produced structure in semi-solid state for 10 min. Then, the effect of severe plastic deformation on mechanical and microstructural properties of this alloy and cast alloy was studied. The results show that with applying 3 passes of multidirectional...
Modeling Evaluation of Pressure Effect on Mold/Metal Interface Heat Transfer Coefficient in A356 Alloy
, M.Sc. Thesis Sharif University of Technology ; Varahram, Nasser (Supervisor) ; Davami, Parviz (Supervisor)
Abstract
Mold/metal interfacial heat transfer coefficient (IHTC) is the most important parameter that influences the solidification and the mechanical properties of a solidified product. The present work focuses on the determination and evaluation of pressure effect on interfacial heat transfer coefficient from the experimental cooling curves during unidirectional solidification of A356 alloy against water cooled Gray iron mold (chill). For this purpose, inverse heat conduction method is used. The results showed that IHTC is not constant, but varies with time, temperature and pressure during solidification. IHTC variation is related to coherency and critical solid fraction during...
Formation of Globular Microstructure by Electromagnetic Stirring and Rheocasting of Semi-Solid A356 Aluminum Alloy
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
The study on new rheoforming technologies of semi-solid alloys has recently been one main subject interesting many researchers and industrials, and so many new methods about preparing semi-solid alloy slurry and rheoforming process have been suggested. Among more than 20 proposed methods, only MHD (Magneto Hydro Dynamics) and EMS (electromagnetic stirring) methods has been industrialized. In this research, the semi-solid slurry of A356 aluminum alloy was fabricated by electromagnetic stirrer under different conditions of stirring current, stirring time and pouring temperatures. Then the semi-solid slurry prepared in optimum conditions was injected into a step-die cavity by a drop device and...
A356 Aluminum Alloy Joining By Local Semisolid Method
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Semisolid joining is a relatively new method that is started since 2002. So far, Aluminum alloys semisolid joining is not studied in details. In this research, by obtaining local semisolid region in the vicinity of the joining seam, two A356 Aluminum part were welded. Hot Nitrogen gas was used to prepare local semisolid region. Since the hot gas was not capable to produce the region by itself, samples were preheated. In experimental procedure, preheating plane type, hot gas temperature, gas flow, sample dimensions, and welding speed were investigated. Effects of each parameter were determined by microstructure studies and measuring the mechanical properties of welding seam. Results showed...
Joining of 304 Stainless Steel to Semi Solid A356 Aluminum Alloy and Investigation of Interfacial Bond
, M.Sc. Thesis Sharif University of Technology ; Aashuri, Hossein (Supervisor)
Abstract
A method of joining dissimilar metals in the semi solid state is presented. By this method bonding of Stainless steel and semisolid aluminum alloy took place in this research. By usage of thermomechanical treatment, dendritic microstructure of cast aluminum alloy changed to globular structure. The experimental process of bonding occurred at semisolid temperature stage of aluminum alloy in a predesigned mold by using a pressure equipment. The relationship between interfacial shear strength and solid fraction of aluminum alloy, bonding pressure and time of keeping pressure were studied by method of orthogonal experiment. By the usage of Taguchi method in designing experiments, plurality of...
Modelling of Pressure Effect on Metal/Mold Interface Resistance in the A356 Aluminium Alloy Casting Process
, M.Sc. Thesis Sharif University of Technology ; Davami, Parviz (Supervisor) ; Varahram, Naser (Supervisor)
Abstract
The computer simulation of freezing patterns in castings has done much to broaden our understanding of casting and mold system design. The structural integrity of shaped castings is closely related to the time–temperature history during solidification, and the use of casting simulation could do much to increase this knowledge in the foundry industry. However, some uncertainties must be eradicated, particularly heat transfer at the metal/mold interface. The accurate knowledge of interfacial heat transfer coefficients is necessary for accurate modeling of castings. The present work focuses on the determination of transient mold–environment and metal–mold heat transfer coefficients during...
A mathematical model for prediction of microporosity in aluminum alloy A356
, Article International Journal of Advanced Manufacturing Technology ; Volume 64, Issue 9-12 , April , 2013 , Pages 1313-1321 ; 02683768 (ISSN) ; Hatami, N ; Varahram, N ; Davami, P ; Shabani, M. O ; Sharif University of Technology
2013
Abstract
In the present work, a mathematical model was developed based on finite difference method to predict the microporosity distribution in A356 aluminum alloy casting. Heat, mass, and gas conservation equations were solved in this model. Moreover, Darcy's equation was considered in the mushy zone. Results show that the distribution and concentration of microporosities in cast parts vary with both cooling rate and initial gas content. Simulation results were compared with experimental data where proportionally good agreement with experimental results was found. Finally, a complex cast part was simulated presenting the ability of the model to predict the porosities in industrial cast parts
Severe plastic deformation of rheoforged aluminum alloy A356
, Article Materials Science and Engineering A ; Volume 558 , 2012 , Pages 371-376 ; 09215093 (ISSN) ; Kazeminezhad, M ; Aashuri, H ; Sharif University of Technology
2012
Abstract
In this research, the electromagnetic stirring (EMS) process was used to produce semi-solid slurry with globular structure from cast A356 aluminum alloy. Then the slurry was forged in a die, which named rheoforging process. Utilizing multidirectional forging (MDF), the effect of severe plastic deformation on microstructure and mechanical properties of this alloy in dendritic and globular states was investigated. Shear punch, micro- and macro-hardness tests were used to study the mechanical properties of these samples. For metallographic examinations, the optical microscope equipped with the Clemex ® image analyzer software was used. Optimum globular structure of rheoforged specimens was...
Comparison of microstructural changes in a SIMA processed A356 aluminum alloy after unidirectional compression and rolling: Effect of pressure depth
, Article Semi-Solid Processing of Alloys and Composites 10 - Selected, peer reviewed papers from the 10th International Conference on Semi-Solid Processing of Alloy and Composites, S2P 2008, Aachen, 16 September 2008 through 18 September 2008 ; Volume 141-143 , 2008 , Pages 391-396 ; 10120394 (ISSN); 9771012039401 (ISBN) ; Bigdeli, M ; Mahdavi, A ; Khomamizadeh, F ; Sharif University of Technology
Trans Tech Publications Ltd
2008
Abstract
In this study, in order to compare effect of unidirectional compression and rolling on final microstructure of strain induced melt activated (SIMA) A356 aluminum alloy, rectangular samples with dimensions of 3cm×5cm in area and 1cm in thickness and cylindrical specimens with 2.5cm in diameter and 1cm in length, have been prepared for rolling and compressing processes, respectively. Then, these samples were plastically deformed at a same strain in ambient temperature. Afterward, the strained samples were cut into equal quarters. In the next stage, to produce globular microstructure, these specimens were partially remelted in 580°C for different times. Results obtained from light microscopy...
Viscosity estimation of semi-solid alloys by drop weight backward extrusion test under high speed deformation
, Article Semi-Solid Processing of Alloys and Composites 10 - Selected, peer reviewed papers from the 10th International Conference on Semi-Solid Processing of Alloy and Composites, S2P 2008, Aachen, 16 September 2008 through 18 September 2008 ; Volume 141-143 , 2008 , Pages 379-384 ; 10120394 (ISSN); 9771012039401 (ISBN) ; Aashuri, H ; Khosravani, A ; Foroughi, A ; Sharif University of Technology
Trans Tech Publications Ltd
2008
Abstract
A simple method for estimating the apparent viscosity of semi-solid alloys was investigated. A drop weight of 50Kg and backward extrusion equipments were used to test the deformation. Backward extrusion was employed in a closed die system due to the very little separation of liquid from solid phases compared with other methods at very high deformation rate. The half of the calculated impact velocity, 700mm/s was considered as an average velocity for deformation during the test, since the slop of the velocity changes against time is constant in the middle stage of the deformation. The initial height of the sample and the thickness of the residual compressed solid at the bottom of the cup were...