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Mechanical Property and Structural Changes of Pure Magnesium and AZ91 Alloy Using ECAP Process
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
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 ; Alizadeh, Reza (Supervisor)
Abstract
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...
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 ; Akbarzadeh, Abbas (Supervisor)
Abstract
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...
Investigation of Microstructural Characteristics and Mechanical Properties of Microalloyed Magnesium X0 via Severe Plastic Deformation Process with Cyclic Closed Die Forging
, M.Sc. Thesis Sharif University of Technology ; Akbarzadeh, Abbas (Supervisor)
Abstract
Nowadays, the application of magnesium alloys as biodegradable implants in the medical industry has garnered significant attention. However, the low mechanical properties and rapid degradation rate of pure magnesium implants in the biological environment have hindered their widespread use for clinical applications. Magnesium-calcium alloys, due to their low degradation rate and promotion of faster bone healing, have become attractive choices for orthopedic applications. Nevertheless, the micro alloy X0 used in this study lacks sufficient strength and flexibility, limiting its potential applications. Utilizing severe plastic deformation methods to create ultrafine microstructures can greatly...
Processing Thin Magnesium Tubes by TCAP Process with Trapezoidal Geometry and Fabrication of Magnesium Microtubes with a Novel Method
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
Due to compability of Magnesium with the body, it is a suitable material for making biodegradable stents, Althogh, its mechanical properties are not desirable for stent application. Accordingly, lately, magnesium’s microstructure and mechanical properties have been improved using various methods, including the process of severe plastic deformation (SPD). Many severe plastic deformation methods have been introduced for the fabrication of ultrafine grain tubes till now, which the process of tubular channel angular pressing (TCAP) is the most effective one. In the first part of the research, Magnesium tubes with a thickness of 1 mm were processed using the TCAP with a trapezoidal channel, and...
Improvement of Mechanical Properties of a Mg-Zn alloy using the Micro Alloying Elements
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
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...
Study on Factor Involved in Multi-step Two Phase CO2 Sequestration Process
, Ph.D. Dissertation Sharif University of Technology ; Shaygan Salek, Jalaloddin (Supervisor) ; Kariminia, Hamid Reza (Supervisor)
Abstract
The increase in CO2 concentration and its effect on ecosystem and global warming make carbon sequestration inevitable for now and future. Ex-situ carbonation of mineral ores is one of the studied sequestration methods. This method is permanent and safe in comparison with others. This process is carried out in four steps and two phases in this dissertation. At the first stage magnesium was extracted from its mineral silicate ore (Mixture of serpentine and olivine) by hydrochloric acid (HCl) and was dissolved in liquid phase as ion. After that the resultant leachate of extraction step was purified from unwanted ions extracted from minerals in two steps by precipitation formed by increasing pH....
Surveying The Biodegradation Behavior, Biocompatibility and Mechanical Properties of Mg-4Zn-xAl-0.2Ca Alloys
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah (Supervisor)
Abstract
Due to their favorable biodegradability, Magnesium and its alloys have always attracted such a lot of research interests for making temporary implants. With the same direction, Mg-4Zn-0.2Ca has recently absorbed lots of research interests, due to its excellent biocompatibility. As the most regarded draw back concerned with this alloy, poor corrosion resistance is frequently discussed. Accordingly, in the present work it has been tried to come over this problem by addition different amount of aluminum, including 1, 3, 5, 7.5, and 10 percent, to this alloy; without causing any negative effect on its biocompatibility, and to present a new alloy composition with modified degradation behavior....
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...
An Investigation on Mechanical Properties of Mg-CNT Composites Produced using the Casting Process
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
Since the discovery of nanomaterials, the nanotubes have found special considerations. The high strength beside the low density, have attracted the interest of the scientists and engineers. Nowadays, one of the common methods to produce composites with high specific strength is to utilize of the nanotubes in the matrix of lightweight metals and alloys such as magnesium and aluminum. Recent researches indicate that very limited focus has been given to the production and properties of the magnesium - carbon nanotube composites and their workability. In this research, magnesium alloy - carbon nanotube composite is produced by casting method and its strength and workability are investigated as...
The Investigation on Hydroxyapatite Coating on Magnesium Alloy and Its Properties
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah (Supervisor)
Abstract
Magnesium and its alloys are biodegradable materials with mechanical properties similar to the bone tissue, therefore these materials are suitable for producing orthopedic implants. Unfortunately Magnesium and its alloys are corroded too fast in physiological environment which is the main obstacle for usage of these materials as orthopedic implants. Producing Hydroxyapatite(HA) coatings on surface of Magnesium and its alloys is one of the popular and useful methods for reducing the corrosion rate in physiological environment. HA is a biocompatible and bioactive coating with the ability to bond chemically with the bone tissue and therefore it is largely used as a bioactive coating on the...
Mechanical Properties Refinement of Magnesium Alloy AZ91 via Cyclic Compression-Expansion Extrusion (CCEE) Method
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
Cyclic Contraction Expansion Extrusion (CCEE) is a new Severe Plastic Deformation (SPD) method used to refine the microstructure and improve mechanical properties of Magnesium AZ91 alloy. In this study, different CCEE process zones are investigated via optical microscopy to understand this process better. The average grain size in the contraction zone decreased to 8.5 microns from an initial value of 106 microns. In the expansion zone, the average grain size was equal to 4.8 microns. Microhardness tests were conducted to study the improvements in mechanical properties. Microhardness of the sample increased from the initial value of 66 HV to 74.4 HV in the contraction zone and 88 HV in...
Investigation Hydrogen Properties of Nano Composite MgH2-Ti Cr1.2Fe0.6 Nano Crystalline Synthesized by Mechanical Alloying and Vacuum Arc Re-Melting(VAR)
,
M.Sc. Thesis
Sharif University of Technology
;
Simchi, Abdol Reza
(Supervisor)
Abstract
In this research, nano composite MgH2-TiCr1.2 Fe0.6 nano crystalline was synthesized by mechanical alloying and Vacuum arc re-melting (VAR). the effect of Milling conditions and adding nano crystalline TiCr1.2 Fe0.6 as a catalyst on the structure and hydrogen desorption properties of MgH2 were studied. MgH2 powder grain size after 4 hours milling gained to 15nm and strain network reached to 0.8%. Determined that the increasing of accumulated lattice strain because of mechanical milling combined with adding nano crystalline alloy TiCr1.2 Fe0.6 significantly improve the properties of MgH2 hydrogen desorption. After an hour mill working, high pressure phase of γ-MgH2 was appeared in...
Improving Mechanical and Biological Behavior of Mg-2ag Alloy: Effects of Y Addition, Heat Treatment and Coating
, M.Sc. Thesis Sharif University of Technology ; Alizadeh, Reza (Supervisor)
Abstract
Biodegradable Mg-Ag alloys are promising implants for bone tissue regeneration due to their unique ability to reduce inflammation and infection after implantation with the presence of silver. However, their biological performance, including biodegradability, needs further improvement. In this regard, the effects of adding yttrium element, solution heat treatment and coating on the microstructure, biodegradability behavior, mechanical properties and biological characteristics of a cast Mg-2Ag alloy were studied. Addition of 1 wt% of yttrium caused grain refinement in the microstructure and solid solution heat treatment led to a significant decrease in the volume fraction of secondary phases....
Debismuthizing of Lead with Alkaline and alkaline Earth Elements
, M.Sc. Thesis Sharif University of Technology ; Yoozbashizadeh, Hossein (Supervisor) ; kaflou, Ali (Supervisor)
Abstract
Lead produced by pyrometallurgy method has a number of impurities. Most of these eimpurities can easily be removed, but this property does not apply in the case of bismuth. Since chemical properties of bismuth are close to the lead, refining of bismuth below 250 ppm is difficult and expensive. Because of problems related to electrochemical discussion of the batteries, bismuth it is possible to reduce below than 20 ppm. Jollivet and Dittmer process is capable of reducing bismuth below 20 ppm. As the main goal of this project is to reduce bismuth to small amounts, Jollivet process was used. Potassium needed for Jollivet process, produced by electrolysis of Potassium chloride salt....
Sintering Improvement of Nano Hydroxyapatite Bodies by Magnesium Incorporation and Using Microwave Sintering
, M.Sc. Thesis Sharif University of Technology ; Sadrnejhad, Khatiboleslam (Supervisor) ; Behnam Ghader, Ali Asghar (Supervisor)
Abstract
Magnesium is one of most important elements in bio hedroxyapatite. Magnesium effects on all stages of bone growth metabolism. Also increases bone’s osteoblastic and osteoclastic activities. That’s why incorporation of Mg ions into hudroxyapatite structure has become one of interesting fields for bone implants production. In addition Mg can improve sintering and mechanical properties of HAp. Thet’s why in this investigation the effect of incorporated Mg into HAp structure has been studied. Three kinds of powders have been prepared to perform this study. Pure HAp nano powder produced via sol-gel method, Mg contain HAp nano powder produced via sol-gel method and a mixture of nano HAp and nano...
Synthesis of Magnesium Nanoparticles with Ball Mill
, M.Sc. Thesis Sharif University of Technology ; Sadrnezhaad, Khatiboleslam (Supervisor)
Abstract
In recent years magnesium nanoparticles due to their noticeable differences from bulk and their wide applications in various branches including the ability to absorb hydrogen, application in batteries, activation of propellant, different applications in biochemistry and strengthening secondary phase in composites, are well under investigation. The objective of this study is to find an easy, economical and high purity method to obtain magnesium nanoparticles and to introduce an innovative approach of magnesium nanoparticles synthesis in an industrial scale. To achieve this goal, milling process is applied. Micron-sized magnesium powders with different amounts of sodium chloride salt powders...
An Investigation into Microstructure and Mechanical Properties of Al/Mgo Composite Fabricated by Friction Stir Processing
, M.Sc. Thesis Sharif University of Technology ; Movahedi, Mojtaba (Supervisor) ; Kokabi, Amir Hossein (Supervisor)
Abstract
In this research, the strength and wear resistance of aluminum 5083 was improved by using composites with magnesium oxide nanoparticles (MgO-20nm) and friction stir processing. The effect of the number of process passes and rotational speed variables, considering the number of one, three, and five passes at rotational speeds of 700, 1000, 1300, 1600, and 1900 rpm, was investigated on the mechanical properties and wear behavior of the composite. To determine the appropriate weight percentage of MgO powder, the longitudinal tensile strength of three composites with different weight percentages of 3, 4.7, and 6 were compared. The linear movement speed of the tool was selected as a constant...
The Effects of Temperature, Strain Rate and Number of Passes on Ecap Processing of WE43 Magnesium Alloy
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor) ; Akbarzadeh, Abbas (Supervisor)
Abstract
Equal Channel Angular Pressing (ECAP) is one of the most applicable severe plastic deformation procedures (SPD) which results in improvement of strength and ductility through grain refinement. WE43 magnesium alloy belongs to a group of alloys for medical industry because of its good biocompatibility. In this study, equal channel angular pressing was performed at different temperatures, strain rates and number of passes on strip-shape samples to achieve proper mechanical properties. Tensile properties, hardness and microstructural evolutions were evaluated and the results were analyzed according to the EDS test. Results shows that at 380 ℃ and 440 ℃ grain refinement was accomplished by...
The Effects of Composition on Hardness and Toughness of ZrO2-Based Ceramics
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor)
Abstract
The purpose of this thesis is the construction of hard and tough Zirconia bodies from economical raw materials using minimum sintering time and temperature.
Stabilizers cause tetragonal particles to be remained in cubic phase. Most additives are Ca, Ce, Mg and Y ions the whole of which are rare earth elements and make solid solutions with Zirconia.
In this project different percents of CaO, MgO, CeO2, and Y2O3 were mixed with ZrO2 and they were sintered after granulation, cold pressing and Cold Isostatic Pressing. Using jar milling and fast milling, the particle size of purchased ZrO2 was reduced to 0.7 um. The whole needed additives were purchased with particle size below 300 nm....
Stabilizers cause tetragonal particles to be remained in cubic phase. Most additives are Ca, Ce, Mg and Y ions the whole of which are rare earth elements and make solid solutions with Zirconia.
In this project different percents of CaO, MgO, CeO2, and Y2O3 were mixed with ZrO2 and they were sintered after granulation, cold pressing and Cold Isostatic Pressing. Using jar milling and fast milling, the particle size of purchased ZrO2 was reduced to 0.7 um. The whole needed additives were purchased with particle size below 300 nm....