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magnesium-alloy
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Mechanisms of joint formation throughout semisolid stir welding of AZ91 magnesium alloy
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 23, Issue 9 , September , 2013 , Pages 2585-2590 ; 10036326 (ISSN) ; Aashuri, H ; Kokabi, A ; Sharif University of Technology
2013
Abstract
Joining in the semisolid state is considered a possible method to join alloys to each other. The mechanisms taking part in semisolid stir welding of AZ91 alloys were investigated. Two 7.5 mm-thick AZ91 pieces and a 2 mm-thick Mg-25%Zn interlayer piece were placed in a heating plate. After holding for 3 min at a desired temperature, the weld seam was stirred by a rotational tool. The heating plate was travelled on a trolley at a constant speed of 4.6 cm/min. In addition, one sample was welded without interlayer. Evolution of welding as a function of stirring rate, tool shape and temperature was studied throughout this welding process with scanning electron and optical microscopes. Interlayer...
Effect of travel speed on quality and welding efficiency of friction stir welded AZ31B magnesium alloy
, Article International Journal of Engineering and Technology(UAE) ; Volume 7, Issue 3 , January , 2018 , Pages 94-99 ; 2227524X (ISSN) ; Selamat, N. F. M ; Sajuri, Z ; Kokabi, A. H ; Sharif University of Technology
Science Publishing Corporation Inc
2018
Abstract
Weight reduction is one of the most concerning issues of automotive and aircraft industries in reducing fuel consumption. Magnesium (Mg) alloys are the lightest alloys which can be used in the structure due to low density and high strength to weight ratio. Developing a reliable joining process of magnesium alloys is required due to limited ductility and low workability at room temperature. Friction stir welding (FSW) is a solid-state welding process that can be performed to produce sound joints in magnesium alloys. Researchers have performed investigations on the effect of rotation and travel speeds in FSW of AZ31B magnesium alloy. However, there is lack of study on the FSW parameters, i.e....
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...
The effects of annular electromagnetic stirring parameters on microstructure evolution of rheocast AZ91 magnesium alloy
, Article Journal of Materials Research and Technology ; Volume 8, Issue 2 , 2019 , Pages 2300-2308 ; 22387854 (ISSN) ; Aashuri, H ; Sharif University of Technology
Elsevier Editora Ltda
2019
Abstract
In the present study, an annular electromagnetic stirrer was used to fabricate the semi-solid slurry of AZ91 magnesium alloy under various conditions of electromagnetic intensities and times. The fabricated semi-solid slurry was injected into a step-die cavity, using a hydraulic jack with ram speed of 1 m/s. The effects of electromagnetic intensity, stirring time and step thicknesses on the microstructure evolution, shape factor, globules equivalent diameter, solid fraction and microhardness of samples were investigated. The experimental results showed that obtained optimal parameters of electromagnetic stirring were 55 (A) stirring current and 30 (s) stirring time. In this conditions, the...
The influence of the ratio of "rotational speed/traverse speed" (ω/v) on mechanical properties of AZ31 friction stir welds
, Article International Journal of Machine Tools and Manufacture ; Volume 46, Issue 15 , 2006 , Pages 1983-1987 ; 08906955 (ISSN) ; Kokabi, A. H ; Daneshi, G. H ; Shalchi, B ; Sarrafi, R ; Sharif University of Technology
2006
Abstract
The influence of different parameters such as welding pressure, rotational speed, and traverse speed on the weld properties has been evaluated earlier but there are some important parameters yet to be thoroughly investigated. In this study, an effort has been made to determine the influence of different ratios of rotational speed/traverse speed on mechanical properties of different zones of friction stir welded AZ31 magnesium alloy. Mechanical properties of different zones were determined by a shear punch test. It was found out that increasing the aforementioned ratio leads to a slight decrease in yield and ultimate strength of the stir zone and the transitional zone. It was also observed...
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....
Microstructure and hardness of friction stir processed AZ31 with SiCp
, Article International Journal of Modern Physics B ; Volume 22, Issue 18-19 , 2008 , Pages 2879-2885 ; 02179792 (ISSN) ; Nasiri, A. M ; Kokabi, A. H ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2008
Abstract
Friction stir processing (FSP) is a novel technique to produce ultrafine grained materials. Most of the researches conducted on FSP focus on aluminum alloys. Despite the potential weight reduction that can be achieved by using magnesium alloys, a few researches have been reported on FSP of magnesium alloys. In this work, the possibility of using FSP with and without SiC particles to modify the microstructure and hardness of commercial AZ31 is examined. SiC particles were uniformly dispersed into an AZ31 matrix by FSP. The mean grain size of the stir zone with the SiC particles was obviously smaller than the same zone without the SiC particles. SiC reinforced magnesium matrix composites...
Cyclic Behavior Modeling of Magnesium Alloy (AZ91) Under Thermo-Mechanical and Low Cycle Fatigue Loadings
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor)
Abstract
Magnesium alloys have been used in the production of light weight components in automobile industries (for example: the ladder frame and the valve cover) due to a good combination of low density (1740 kg/m3), the tensile strength (160-365 MPa) and the elastic modulus (45 GPa). For the design and the optimization of these components under various loadings and different conditions, it is necessary to determine fatigue properties of the material by using thermo-mechanical and low cycle fatigue tests at different temperatures. In thermo-mechanical fatigue tests, the temperature varies in a specific range with the mechanical strain. The goal of this research is to investigate low cycle fatigue...
Investigating the Effects of Heat Treatment and Y Addition on the Microstructure, Mechanical Properties and Corrosion Behavior of Bio-Degradable Mg–Si Alloys
, M.Sc. Thesis Sharif University of Technology ; Alizadeh, Reza (Supervisor)
Abstract
In Mg–Si alloys, both primary and eutectic Mg2Si particles normally appear with sharp edges, which can lead to weak mechanical properties as the result of stress concentration at the sharp corners of these brittle particles. On the other hand, the morphology, size and distribution of Mg2Si particles affect corrosion behavior of Mg–Si alloys. Thus, it would be of great importance to modify the morphology of these particles. In this study, microstructure modification mechanisms after 0.5 wt% Y addition and heat treatment (HT) at 420 ◦C for 24 h are comprehensively studied in hypo-eutectic Mg–1Si and hyper-eutectic Mg–2Si alloys. Microstructural observations were performed using optical and...
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...
Investigating Microstructure, Mechanical Properties and Corrosion Resistance of New Biodegradable Mg-2Zn-xAg-yCu (x=0-0.6,y=0-0.1) Alloys
, M.Sc. Thesis Sharif University of Technology ; Alizadeh, Reza (Supervisor) ; Sadrnezhaad, Khatiboleslam (Co-Supervisor)
Abstract
Magnesium has recently been considered as a biocompatible metal with mechanical properties close to bone for use in biological applications. On the other hand, the degradation properties of this metal in the physiological environment have made this metal superior to permanent biomaterials such as stainless steel, titanium alloys. The most important challenge of using this alkaline earth metal in the body environment is its rapid corrosion, which causes problems such as alkaline toxicity and loss of supporting role before complete tissue repair. In this study, Mg-Zn-Ag-Cu alloys were manufactured to improve mechanical strength, corrosion resistance and antibacterial properties. Finally, after...
Structure and corrosion behavior of oxide layer with Zr compounds on AZ31 Mg alloy processed by two-step plasma electrolytic oxidation
, Article Surface and Coatings Technology ; Vol. 238 , 2014 , pp. 75-79 ; ISSN: 02578972 ; Lee, K. M ; Sani, M. A. F ; Yoo, B ; Shin, D. H ; Sharif University of Technology
Abstract
The formation of the oxide layer with Zr compounds on AZ31 Mg alloy processed by two-step plasma electrolytic oxidation (PEO) has been investigated. After the PEO process first in an alkaline phosphate electrolyte and second in an acid electrolyte containing K2ZrF6, the microstructure, chemical composition, and phase composition of the oxide layers were analyzed via SEM, EDS, and XRD, respectively. The electrochemical reaction and the high temperature caused by the plasma discharges in the electrolyte were the main factors leading to the fabrication of an oxide layer containing Zr compounds on AZ31 Mg alloy. The micro-pores were filled with ZrO2 formed during the PEO process. The results of...
A new energy-based isothermal and thermo-mechanical fatigue lifetime prediction model for aluminium-silicon-magnesium alloy
, Article Fatigue and Fracture of Engineering Materials and Structures ; Volume 36, Issue 12 , 2013 , Pages 1323-1335 ; 8756758X (ISSN) ; Azadi, M ; Winter, G ; Eichlseder, W ; Sharif University of Technology
2013
Abstract
In this paper, a new fatigue lifetime prediction model is presented for the aluminium-silicon-magnesium alloy, A356.0. This model is based on the plastic strain energy density per cycle including two correction factors in order to consider the effect of the mean stress and the maximum temperature. The thermal term considers creep and oxidation damages in A356.0 alloy. To calibrate the model, isothermal fatigue and out-of-phase thermo-mechanical fatigue (TMF) tests were conducted on the A356.0 alloy. Results showed an improvement in predicting fatigue lifetimes by the present model in comparison with classical theories and also the plastic strain energy density (without any correction...
Effect of temperature on microstructural evolution and subsequent enhancement of mechanical properties in a backward extruded magnesium alloy
, Article International Journal of Advanced Manufacturing Technology ; 2017 , Pages 1-12 ; 02683768 (ISSN) ; Mirjavadi, S. S ; Salandari Rabori, A ; Sharif University of Technology
Abstract
The capability of backward extrusion (BE) method was assessed to achieve modified structures in AZ80 magnesium alloy. At first, 3D-Deform was employed to simulate the deformation flow through the deformed cup which gives an evidence from the flow behavior of the material. The material was processed via BE method at various temperatures of 250, 350, and 450 °C. Metallographic investigations were conducted in three different regions of the BE-processed cup (wall, bottom, and flow channel). The main feature observed at the wall of the BE cup was the presence of mechanical twins, the frequency of which was reduced by raising the process temperature. The flow localization in the form of shear...
Effect of temperature on microstructural evolution and subsequent enhancement of mechanical properties in a backward extruded magnesium alloy
, Article International Journal of Advanced Manufacturing Technology ; Volume 95, Issue 9-12 , 2018 , Pages 3155-3166 ; 02683768 (ISSN) ; Mirjavadi, S. S ; Salandari-Rabori, A ; Sharif University of Technology
Springer London
2018
Abstract
The capability of backward extrusion (BE) method was assessed to achieve modified structures in AZ80 magnesium alloy. At first, 3D-Deform was employed to simulate the deformation flow through the deformed cup which gives an evidence from the flow behavior of the material. The material was processed via BE method at various temperatures of 250, 350, and 450 °C. Metallographic investigations were conducted in three different regions of the BE-processed cup (wall, bottom, and flow channel). The main feature observed at the wall of the BE cup was the presence of mechanical twins, the frequency of which was reduced by raising the process temperature. The flow localization in the form of shear...
A comparative study between friction stir processing and friction stir vibration processing to develop magnesium surface nanocomposites
, Article International Journal of Minerals, Metallurgy and Materials ; Volume 27, Issue 8 , 2020 , Pages 1133-1146 ; Abbasi, M ; Abdollahzadeh, A ; Kokabi, A. H ; Sharif University of Technology
University of Science and Technology Beijing
2020
Abstract
Friction stir processing (FSP) can be used to improve surface composites. In this study, a modified method of FSP called friction stir vibration processing (FSVP) was applied to develop a surface composite on AZ91 magnesium alloy. In this technique, the workpiece is vibrated normal to the processing direction. The results illustrated that compared with the FSP method, the FSVP caused a better homogeneous distribution of SiC particles in the microstructure. The results also showed that matrix grains of friction stir vibration processed (FSV-processed) samples ((26.43 ± 2.00) µm) were finer than those of friction stir processed (FS-processed) specimens ((39.43 ± 2.00) µm). The results...
Effect of liquation on the tensile properties of cast Mg–9Al–1Zn Alloy fusion welds
, Article Science and Technology of Welding and Joining ; Volume 25, Issue 8 , 2020 , Pages 698-705 ; Jiryaei Sharahi, H ; Movahedi, M ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
This paper aims at understanding the role of liquation and solidification phenomena on the tensile properties of arc welded cast AZ91 magnesium alloy. Owing to its refined microstructure, the fusion zone exhibited improved ductility/strength compared to the base metal. It is demonstrated that the partially melted zone (PMZ) which is characterised by constitutional liquation of eutectic β-Mg17Al12 phase is the weakest link in the weldment. The reduced strength and ductility associated with the liquation phenomena are due to the increased volume fraction and thickness of the eutectic β-Mg17Al12 in the PMZ as well as the formation of liquation micro-cracks in a network of brittle intermetallic...
Microstructural evolution of AZ91 alloy containing 3%Ca prepared by cooling slope
, 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 427-432 ; 10120394 (ISSN); 9771012039401 (ISBN) ; Aashuri, H ; Davami, P ; Narimannezhad, A ; Foroughi, A ; Kiani, M ; Sharif University of Technology
Trans Tech Publications Ltd
2008
Abstract
Globulization of the grain refined AZ91 magnesium alloy with Ca on a cooling slope was investigated. Dendritic morphology of the grains was transferred into round and well distributed small particles as a result of grain-refinement effect of Ca in the alloy. Semi-solid holding of the alloy was carried out at different temperatures to improve the spherecity of the globules. Results show that, remelting at 540 °C for 30 min provides the best shape factor for the alloy. The study of coarsening kinetic in this alloy showed lower growth rate alternative other research which used same condition for produce semi-solid billet just in using Ca
Wire-Based friction stir processing as a novel pathway for solid-state surface alloying of magnesium
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 52, Issue 11 , 2021 , Pages 4737-4741 ; 10735623 (ISSN) ; Mousavizade, S. M ; Pouranvari, M ; Sharif University of Technology
Springer
2021
Abstract
Wire-based friction stir processing is introduced as a solid-state surface alloying strategy for surface alloying of AZ31 magnesium alloy with aluminum, as a key alloying element in magnesium alloys. This technique enables the formation of a defect-free, grain refined and alloyed surface with the increased volume fraction of Mg-Al second phase, and thus, enhanced surface hardness. This simple technique provides a solid-state surface alloying pathway to improve the surface properties of the metallic materials. © 2021, The Minerals, Metals & Materials Society and ASM International
Formability of tri-layered IF240/AZ31/IF240 composite with strong bonding: experimental and finite element modeling
, Article Journal of Materials Engineering and Performance ; Volume 30, Issue 11 , 2021 , Pages 8402-8411 ; 10599495 (ISSN) ; Akbarzadeh, A ; Hadiyan, B ; Hashemi, R ; Sharif University of Technology
Springer
2021
Abstract
In this work, the formability of a hybrid material of Interstitial-Free 240 (IF240) steel and AZ31 magnesium alloy as IF240/AZ31/IF240 tri-layered sheets was investigated. For this purpose, the bonding feasibility of the high-formability IF240 steel and low-formability AZ31 sheets was first assessed. Then, the hot formability behavior of the manufactured laminated composite was evaluated. The rolling of the preheated samples established the layer bonding. The bonding strength was determined using the shear punch test. The texture and its effects on the forming behavior were studied using the x-ray Goniometry method. Nakazima dome tests were employed at ambient and elevated temperatures to...