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Effect of rare-earth element additions on high-temperature mechanical properties of AZ91 magnesium alloy
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 36, Issue 12 , 2005 , Pages 3489-3494 ; 10735623 (ISSN) ; Nami, B ; Khoshkhooei, S ; Sharif University of Technology
Minerals, Metals and Materials Society
2005
Abstract
The present article focuses on the high-temperature mechanical properties of the magnesium alloy AZ91. The addition of rare-earth (RE) elements up to 2 wt pct improves both yield and tensile strengths at 140 °C by replacing the Mg17Al12 phase with RE-containing intermetallic compounds. This intermetallic phase is thermally and metallurgically stable and is expected to boost the grain-boundary strengthening. It also increases the resistance of grain boundaries to flow at high temperatures. Further increases of RE additions reduce strength and ductility due to growth of the Al11RE3 brittle phase, which has sharp edges. Still, at a 3 wt pct RE addition, the strength of the alloy at high...
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...
Stress–strain time-dependent behavior of A356.0 aluminum alloy subjected to cyclic thermal and mechanical loadings
, Article Mechanics of Time-Dependent Materials ; Vol. 18, issue. 3 , 2014 , p. 475-491 ; Ghodrati, M ; Azadi, M ; Rezvani Rad, M ; Sharif University of Technology
Abstract
This article presents the cyclic behavior of the A356.0 aluminum alloy under low-cycle fatigue (or isothermal) and thermo-mechanical fatigue loadings. Since the thermo-mechanical fatigue (TMF) test is time consuming and has high costs in comparison to low-cycle fatigue (LCF) tests, the purpose of this research is to use LCF test results to predict the TMF behavior of the material. A time-independent model, considering the combined nonlinear isotropic/kinematic hardening law, was used to predict the TMF behavior of the material. Material constants of this model were calibrated based on room-temperature and high-temperature low-cycle fatigue tests. The nonlinear isotropic/kinematic hardening...
Improvement of high temperature fatigue lifetime in AZ91 magnesium alloy by heat treatment
, Article Materials Science and Engineering A ; Volume 588 , December , 2013 , Pages 357-365 ; 09215093 (ISSN) ; Azadi, M ; Hossein Farrahi, G ; Winter, G ; Eichlseder, W ; Sharif University of Technology
2013
Abstract
In the present paper, an improvement in high temperature fatigue properties of the AZ91 magnesium alloy with rare earth elements has been obtained by a typical heat treatment, denoted by T6. For this objective, out-of-phase thermo-mechanical fatigue, room temperature and high temperature low cycle fatigue tests are performed to compare lifetimes. Several rare earth elements are initially added to the AZ91 alloy during a gravity casting process in permanent molds. Also, the type of the heat treatment is examined. Results of specimens with only the solution (the T4 heat treatment) and the solution with the ageing process (the T6 heat treatment) are compared under isothermal fatigue loadings....
Characterization of newly developed semisolid stir welding method for AZ91 magnesium alloy by using Mg-25%Zn interlayer
, Article Materials Science and Engineering A ; Volume 565 , 2013 , Pages 165-171 ; 09215093 (ISSN) ; Aashuri, H ; Kokabi, A. H ; Sharif University of Technology
2013
Abstract
Semisolid stir joining of AZ91 alloy was investigated by using mechanical stirring and Mg-25. wt%Zn interlayer. A 2. mm-thick interlayer was located between two 7.5. mm-thick AZ91 pieces. Then, they were heated to 530. °C, the semisolid temperature of both base metal and interlayer. A stirrer with a rotational speed of 1600. rpm was introduced into the weld seam. Optical microscopic and scanning electron microscope (SEM) investigation, microhardness test, shear punch test (SPT), and three points bending test were carried out to assess the properties of the joint. Results showed three distinctive zones: stir zone (SZ), compacted zone (CZ), and diffusional-mechanical affected zone (DMAZ). SEM...
Effect of rare earth elements addition on thermal fatigue behaviors of AZ91 magnesium alloy
, Article Journal of Rare Earths ; Volume 27, Issue 2 , 2009 , Pages 255-258 ; 10020721 (ISSN) ; Saebnoori, E ; Sharif University of Technology
Chinese Society of Rare Earths
2009
Abstract
Influences of rare earth (RE) elements addition on thermal fatigue behaviors of AZ91 alloy were studied. Repeated heating and cooling cycles were applied on the samples at 170 and 210 °C to develop thermal fatigue cracks. Crack growth mechanisms and microstructural influences were investigated by optical and scanning electron microscopy (SEM) as well as energy dispersive X-ray spectroscopy (EDS). Thermal fatigue behaviors were observed to improve successively by addition of the RE up to 2wt.%. This improvement was attributed to the consummation of aluminum in melt by precipitation of the needle shaped Al11RE3 phases. This process was attributed to the reduction of Mg17Al12 phase volume...
Effect of magnesium addition on the wetting of alumina by aluminium
, Article Applied Surface Science ; Volume 255, Issue 19 , 2009 , Pages 8202-8206 ; 01694332 (ISSN) ; Halali, M ; Sharif University of Technology
2009
Abstract
In this report the wetting behaviour between polycrystalline alumina substrates and molten aluminium doped with magnesium as a wetting agent has been studied using the sessile drop technique. The time required for equilibrium attainment is investigated. To explore the formation of possible phases at the interface, electron microscopic studies along with EDX analysis have been employed. It is found that magnesium reduces the time and temperature required for equilibrium in the Al/Al2O3 system. The Al-7 wt% Mg and Al-10 wt% Mg alloys can wet alumina at temperatures as low as 900 °C. It is also found that molten aluminium doped with magnesium can wet polycrystalline alumina at temperatures...
Liquid segregation behavior of semi-solid AZ91 alloy during back extrusion test
, Article Journal of Alloys and Compounds ; Volume 477, Issue 1-2 , 2009 , Pages 822-827 ; 09258388 (ISSN) ; Aashuri, H ; Davami, P ; Narimannezhad, A ; Hadian, R ; Sharif University of Technology
2009
Abstract
The present work is focused on the segregation behavior of semi-solid AZ91 magnesium alloy with Ca content. For this purpose a simple back extrusion test was used and the semi-solid billet was fabricated through a cooling slope. Different shear rates were obtained by variation in ram speed and extrusion ratio. Microstructures of the extruded samples were investigated and liquid segregation was described by Darcy's law. Homogeneity was improved by using higher shear rates, produced either by increasing plunger velocity or extrusion ratio, while at very high shear rates the air was entrapped inside the wall of the extruded sample. © 2008 Elsevier B.V. All rights reserved
Effect of intermetallic compounds on the fracture behavior of dissimilar friction stir welding joints of Mg and Al alloys
, Article International Journal of Minerals, Metallurgy and Materials ; Volume 26, Issue 10 , 2019 , Pages 1285-1298 ; 16744799 (ISSN) ; Sajuri, Z ; Selamat, N. F. M ; Omar, M. Z ; Miyashita, Y ; Kokabi, A. H ; Sharif University of Technology
University of Science and Technology Beijing
2019
Abstract
Joining Mg to Al is challenging because of the deterioration of mechanical properties caused by the formation of intermetallic compounds (IMCs) at the Mg/Al interface. This study aims to improve the mechanical properties of welded samples by preventing the fracture location at the Mg/Al interface. Friction stir welding was performed to join Mg to Al at different rotational and travel speeds. The micro structure of the welded samples showed the IMCs layers containing Al12Mg17 (γ) and Al3Mg2 (β) at the welding zone with a thickness (> 3.5
An investigation on microstructure evolution, mechanical properties, and strain aging of Mg-1.8Zn-0.7Si-0.4Ca biomedical alloy processed by equal channel angular pressing
, Article Journal of Materials Engineering and Performance ; Volume 28, Issue 8 , 2019 , Pages 5207-5219 ; 10599495 (ISSN) ; Karimi Taheri, K ; Karimi Taheri, A ; Shaeri, M. H ; Sharif University of Technology
Springer New York LLC
2019
Abstract
The influence of equal channel angular pressing (ECAP) on microstructure and mechanical behavior, as well as, strain aging during ECAP and post-ECAP of Mg-1.8Zn-0.7Si-0.4Ca biomedical alloy was examined. The alloy in solid solution heat-treated condition was processed by ECAP with route BC at 350 and 400 °C. The specimens ECAPed at 350 °C were aged at 125 and 150 °C for different times. The hardness and shear punch test results indicated that performing ECAP at 350 °C for 4 passes increases the hardness and shear strength of the alloy from 48 HV and 110 MPa to 71 HV and 188 MPa, respectively. It was revealed that the average grain size of the alloy decreases from 78 µm to about 3 µm after 4...
Plasma electrolytic oxidation and corrosion protection of friction stir welded AZ31B magnesium alloy-titanium joints
, Article Surface and Coatings Technology ; Volume 393 , 2020 ; Rogov, A ; Skeldon, P ; Zhou, X ; Yerokhin, A ; Aliabadi, A ; Ghorbani, M ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Joining of dissimilar light metals by friction stir welding (FSW) is of interest to reduce weight and fuel consumption in the transport sector. Such coupled metals may need protective surface treatments, e.g. against wear or corrosion, for some applications. In this work, the formation of plasma electrolytic oxidation (PEO) coatings in a silicate-based electrolyte for corrosion protection of FSW AZ31B magnesium alloy-titanium joints has been studied. The joints, if unprotected, may be susceptible to severe galvanic corrosion in chloride-containing environments. The coatings were characterized by scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. Mg2SiO4 and...
Effect of second-phase particle size and presence of vibration on AZ91/SiC surface composite layer produced by FSP
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 30, Issue 4 , 2020 , Pages 905-916 ; Abbasi, M ; Abdollahzadeh, A ; Mirsalehi, S. E ; Sharif University of Technology
Nonferrous Metals Society of China
2020
Abstract
An improved method of friction stir processing (FSP) was introduced for the processing of AZ91 magnesium alloy specimens. This novel process was called “friction stir vibration processing (FSVP)”. FSP and FSVP were utilized to develop surface composites on the studied alloy while SiC nanoparticles were applied as second-phase particles. The effect of reinforcing SiC particles with different sizes (30 and 300 nm) on different characteristics of the composite surface was studied. The results indicated that the microstructure was refined and mechanical properties such as hardness, ductility, and strength were enhanced as FSVP was applied. Furthermore, it was concluded that the effect of...
Fatigue life prediction of pre-corroded AZ31 magnesium alloy based on surface topology
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; 2021 ; 09544062 (ISSN) ; Adibnazari, S ; Sharif University of Technology
SAGE Publications Ltd
2021
Abstract
This research explored the corrosion effect of NaCl solution on the surface quality of AZ31 magnesium alloy. Cubic-shaped specimens were immersed in standard 3.5% NaCl solution for 1, 2, 3, and 4 hours. The size of corrosion pits, fatigue crack propagation area, and surface topology were characterized. Fatigue tests were carried out on pre-corroded AZ31 specimens under different stress amplitudes. The correlation between the corrosion time and the virtual crack size was obtained. The virtual crack size is a new parameter that can relate the corrosion to the fatigue life. A new model was proposed to map the surface topology on the virtual crack size of pre-corroded AZ31 magnesium alloy. The...
Effects of heat treatment on the corrosion behavior and mechanical properties of biodegradable Mg alloys
, Article Journal of Magnesium and Alloys ; Volume 10, Issue 7 , 2022 , Pages 1737-1785 ; 22139567 (ISSN) ; Alizadeh, R ; Gerashi, E ; Asadollahi, M ; Langdon, T. G ; Sharif University of Technology
National Engg. Reaserch Center for Magnesium Alloys
2022
Abstract
Biodegradable magnesium (Mg) alloys exhibit great potential for use as temporary structures in tissue engineering applications. Such degradable implants require no secondary surgery for their removal. In addition, their comparable mechanical properties with the human bone, together with excellent biocompatibility, make them a suitable candidate for fracture treatments. Nevertheless, some challenges remain. Fast degradation of the Mg-based alloys in physiological environments leads to a loss of the mechanical support that is needed for complete tissue healing and also to the accumulation of hydrogen gas bubbles at the interface of the implant and tissue. Among different methods used to...
Fatigue life prediction of pre-corroded AZ31 magnesium alloy based on surface topology
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 236, Issue 7 , 2022 , Pages 3623-3635 ; 09544062 (ISSN) ; Adibnazari, S ; Sharif University of Technology
SAGE Publications Ltd
2022
Abstract
This research explored the corrosion effect of NaCl solution on the surface quality of AZ31 magnesium alloy. Cubic-shaped specimens were immersed in standard 3.5% NaCl solution for 1, 2, 3, and 4 hours. The size of corrosion pits, fatigue crack propagation area, and surface topology were characterized. Fatigue tests were carried out on pre-corroded AZ31 specimens under different stress amplitudes. The correlation between the corrosion time and the virtual crack size was obtained. The virtual crack size is a new parameter that can relate the corrosion to the fatigue life. A new model was proposed to map the surface topology on the virtual crack size of pre-corroded AZ31 magnesium alloy. The...
Biodegradation behavior of polymethyl methacrylate−bioactive glass 45S5 composite coated magnesium in simulated body fluid
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 32, Issue 7 , 2022 , Pages 2216-2228 ; 10036326 (ISSN) ; Jafari, H ; Pishbin, F ; Mohammadi, R ; Simchi, A ; Sharif University of Technology
Nonferrous Metals Society of China
2022
Abstract
The biodegradation behavior of Mg, coated by polymethyl methacrylate as well as polymethyl methacrylate (PMMA)−bioactive glass (BG) composite was investigated. Electrophoretic deposition and dip coating techniques were adopted to prepare composite coating using a suspension of different percentages of the above two chemical materials. The deposited coatings were characterized using SEM, EDS, FTIR, and water contact angle measurements. Biodegradation behavior study of the coated Mg was performed using linear polarization, impedance spectroscopy, and immersion tests in simulated body fluid. The compact and homogeneous composite coating was developed as evidenced by electron microscopy results....
The effect of different rare earth elements content on microstructure, mechanical and wear behavior of Mg-Al-Zn alloy
, Article Materials Science and Engineering A ; Volume 527, Issue 7-8 , 2010 , Pages 2027-2035 ; 09215093 (ISSN) ; Masoudi, A ; Khomamizadeh, F ; Sharif University of Technology
2010
Abstract
The effect of Rare earths addition to AZ91 magnesium alloy and its influence on the microstructure and mechanical properties was investigated in this study. Addition of cerium rich misch metal to AZ91 alloy resulted in formation of needle shape particles, which had a very high thermal stability, providing superior mechanical properties compared to AZ91 magnesium alloy. As a result, the grain boundaries were less susceptible for grain boundary sliding at high temperatures. The steady state creep rates were specified and for the AZ91 alloy and the results indicate a mixed mode of creep behavior, with some grain boundary effects contributing to the overall behavior. However for the RE added...
An Investigation into the Effect Of Severe Plastic Deformation by Equal Channel Angular Extrusion (Ecae) Process on Mechanical and Microstructural Properties of a Mg-Zn Alloy
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
The specific properties of some of magnesium alloys have caused these alloys to be used in medical and industrial applications. Adding new elements and applying severe plastic deformation to these alloys have been considered as a clue for improving their mechanical properties. The aim of this project is to improve the mechanical properties of a magnesium alloy by using new alloying elements and applying the ECAP process.
In this project, a new magnesium alloy by composition of Mg-1.78Zn-0.72Si-0.41Ca was cast. After casting, solution treating and annealing of the alloy were studied. Then, the effect of ECAP process on microstructure and mechanical properties of the annealed and solution...
In this project, a new magnesium alloy by composition of Mg-1.78Zn-0.72Si-0.41Ca was cast. After casting, solution treating and annealing of the alloy were studied. Then, the effect of ECAP process on microstructure and mechanical properties of the annealed and solution...
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...
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...