Sharif Digital Repository

Magnesium and its alloys have gained significant popularity due to their light weight and their potential for use as bioresorbable materials. However, their application is limited in practice due to their relatively poor corrosion resistance. Several methods are available for improving the corrosion resistance of Mg alloys for bio-applications such as using different coatings, alloying, and modifying the microstructural parameters such as the grain size and the crystallographic texture. This review provides a comprehensive summary of the effects of crystallographic texture and twinning, as one of the most important deformation mechanisms of Mg and Mg alloys, on the corrosion behavior.... 

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... 

To improve the hydrogen kinetics of magnesium hydride, TiCr1.2Fe0.6 alloy was prepared by vacuum arc remelting (VAR) and the alloy was co-milled with MgH2 to process nanostructured MgH2–5 at.% TiCr1.2Fe0.6 powder. The hydrogen desorption properties of the composite powder were studied and compared with pure magnesium hydride. X-ray diffraction (XRD) analysis showed that the composite powder prepared by VAR/mechanical alloying (MA) procedure consisted of β-MgH2, γ-MgH2, bcc Ti–Cr–Fe alloy, and small amount of MgO. The average size of particles and their grain structure after 4 h MA were determined by a laser particle size analyzer and XRD method and found to be 194 nm and 11 nm, respectively.... 

Accumulative roll bonding (ARB) is one of the effective severe plastic deformation methods for developing very fine grained nanostructures. In the present work, grain refinement and microstructural changes of magnesium AZ31 alloy during ARB process was investigated. Sheet specimens up to 256 cold welded layers (eight ARB cycles) were prepared. Evolution of the microstructure was observed using optical microscopy. It is shown that various mechanisms such as rotational recrystallisation (RRX) and twinning are involved in grain refinement at different passes. Increasing the number of ARB cycles leads to an ultra fine grain (UFG) microstructure (almost 500 nm) surrounded by nanoscale grain zones... 

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.... 

The aim of this study is to determine the determine effects of magnesium supplementation on anthropometric indices Consist of body weight (BW), waist circumference (WC), body mass index (BMI) and body fat percentage (BF%). In this systematic review and dose-response meta-analysis, we searched PubMed, Cochrane Library, Scopus, Web of Science and Google Scholar from databases inception up February 2020 for relevant randomized controlled trials. Quality of evidence was evaluated using the Cochrane Collaboration Tool. All of outcome in this meta-analysis were pooled using Random Effect Model. Analysis of dose-response for magnesium dosage was carried out using a fractional polynomial model. The... 

The solution equilibria of magnesium (II) complex formed with bidentate ligand of dopamine in acidic media (pH=∼4-∼6) have been studied in cosolvent systems at 15, 25, 35 ± 0.1° C and 1=0.2 mol.dm-3 sodium chloride, using phosphate buffer, with spectrophotometric methods. Evidence for the 2:1 complex was not observed for magnesium. The stability constant of the complex was determined KMg(HL)+ = ∼9 and the resulting free-energy changes obtained. The protonation constant of dopamine was determined under the above conditions. The results are discussed in terms of the effect of solvent on protonation and complexation  

In this study, the influence of the sample position (anode) on the incorporation of nano/micro alumina particles on the AZ31B magnesium alloy substrate was investigated by plasma electrolytic oxidation (PEO) coating. For characterized this effect, Scanning electron microscopy (SEM), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and pin-on-disk test were used to the evolution of the microstructure, corrosion resistance, and the wear behavior of the films. Based on the obtained results, the effect of the anode position from vertical to horizontal is dependent on particle size and it can be influenced only on the incorporation of nanoparticles. The... 

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... 

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... 

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... 

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 effects of the most important parameters of hot pressing, including temperature, time and pressure on densification, microstructure and infrared transparency of MgF2 ceramics are discussed. The results show that the absorption or scattering of incident radiation is strongly dependent on the amount of porosity. By increasing the temperature or the pressure, transparency at infrared wavelengths has been increased due to the rise in density. For the longer hot pressing times, a continuous increase in density and infrared transparency has been seen as well. Cold pressing before hot press has minor effects on the density and infrared transparency of MgF2. © 2008 Elsevier B.V. All rights... 

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... 

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... 

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...