
Ahmad BahmaniIranian Research Organization for Science and Technology | IROST · Advanced Materials and Revewable Energies
Ahmad Bahmani
PhD in Materials Science and Engineering
Assistant Professor (IROST)
CEO (ARTofMag)
About
56
Publications
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1,127
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Introduction
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March 2013 - December 2014
Publications
Publications (56)
The effects of different elements including Al, Sn and Zn with ability of solution hardening on corrosion behavior of a Mg alloy have been studied. The microstructure was analyzed and the electrochemical and immersion techniques were used for corrosion studies. Scanning kelvin probe force microscopy (SKPFM) was utilized to analyze the volta-potenti...
Extruded Mg alloy (ZAXM4211) was subjected to multi-directional forging (MDF) at different temperatures from 180 to 300 °C. Microstructure was analyzed using optical microscope (OM), scanning electron microscope (SEM), electron backscattered diffraction (EBSD), and X-ray diffraction (XRD) studies. Tensile and compression properties were evaluated a...
An extruded Mg alloy was subjected to the screw rolling (SR) at different temperatures. The microstructure, corrosion behavior, and mechanical properties were analyzed. Electrochemical and immersion techniques were applied for corrosion behavior analysis. Moreover, scanning Kelvin probe force microscopy (SKPFM) was utilized to measure the surface V...
Up to the date of writing this article, a quantitative analysis between corrosion rate and combined microstructural parameters including composition, grain size, and precipitations has not been reported. Hence, a literature review was carried out on these parameters to understand the quantitative effect of each one on the corrosion rate of Mg and M...
An attempt was made to develop a corrosion-resistant, high-strength Mg alloy using multi-directional forging (MDF). An extruded alloy as well as pure Mg was MDFed at temperatures between 220 and 340°C with 40°C intervals. Grains, second phase distribution, and Volta-potential difference between second phases and matrix were measured. Moreover, tens...
Mg-Zn-Ca-Mn materials micro-alloyed by Gd, Nd, Ce, and La rare-earth and Sr alkaline elements were developed. Optical and scanning electron microscopy, X-ray diffraction spectroscopy, tensile test, immersion, and electrochemical tests were applied to analyze microstructure, mechanical properties, and corrosion behavior. While the development of the...
With the growing interest in lightweight materials, magnesium and its alloys have received substantial attention for replacing existing alloys. After investigating the mechanical alloying process of Mg-Ca alloys and determining the optimum parameters for milling in part I of this study, the current research aims to examine the second step: the sint...
The synergetic effect of strontium (Sr) and rare earth elements (RE) on the corrosion properties of as-cast Mg–9Al–1Zn alloy were studied. Via the addition of 0.5 wt-% RE and 0.5 wt-% Sr (RE/Sr ratio of 1), a remarkable reduction in the corrosion rate of AZ91 was observed. The reason was found to be related to the decrement of the micro-galvanic co...
The effects of Ca addition on the microstructure and oxidation properties of a new Mg alloy were studied. The oxidation behavior of the alloys was analyzed by thermal analysis and material characterization of the alloys exposed in flame environment; and both electrical and induction furnaces. Moreover, the surface layers were characterized using fi...
Magnesium (Mg) alloys have several advantages, such as low density, high specific strength and biocompatibility. However, they also suffer weak points, such as high corrosion, low formability and easy ignition, which makes their applications limited. Many studies have been conducted to overcome these disadvantages and further improve the advantages...
A novel Mg-0.7Ca alloy was prepared by the mechanical alloying (MA) process. Different variables were examined in order to obtain the optimum sample with the best milling behavior and potential sinterability. The structural studies were carried out using X-ray Diffractometer (XRD) and scanning electron microscopy (SEM). Crystallite size and lattice...
MgO-based ceramic layers were in-situ synthesized on a novel Mg-based substrate via plasma electrolytic oxidation (PEO). To investigate the effects of electrolyte composition on the morphological characteristics of the obtained layers, three different ion arrangements were applied. Morphological investigations via scanning electron microscopy and e...
In the present study, various processes have been carried out on the extruded Mg-4Zn-4Al-0.6Ca-0.5Mn (wt.%) alloy to achieve a low corrosion rate Magnesium (Mg) alloy. Microstructure studies revealed that the extruded alloy contained the needle-like Al-Mn second phases and the globular and elongated (Mg,Al)2Ca + ϕ(AlMgZn) phases. After solution tre...
Compressive deformation behavior at room temperature and the high temperatures was studied for Zr33Hf8Ti6Cu32Ni10Co5Al6 developed HEBMG and Cu47Zr47Al6 BMG alloys. Compressive strain-stress curves at room temperature showed that with the development of HEBMG, ductility and fracture stress improved by 58% and 5.4%, respectively. The high density of...
In this study, new non-equiatomic high entropy bulk metallic glass (HEBMG) Zr33Hf8Ti6Cu32Ni10Co5Al6 was developed according to the Cu47Zr47Al6 prototype BMG. Kinetic studies were performed with non-isothermal DSC for the BMG and the HEBMG, and their thermal properties were compared. Calculation of activation energies by different methods indicated...
The effects of calcium addition at microalloying levels and hot extrusion process on the modification of the microstructure and enhancement of the mechanical properties of the Mg-3Si metal matrix composite (MMC) were studied. Electron backscatter diffraction (EBSD), X-ray diffraction (XRD), cooling curve thermal analysis, simulation based on the fi...
Tensile strength of aluminum castings has been improved by employing surge and filter in a conventional non-pressurizing gating system. For this purpose, three non-pressurizing bottom-gating systems were designed where the first design was a simple design with no filter and no surge, in the second design filter and in the third one surge was added...
In the present study, a new biodegradable Mg-Zn-Cu magnesium alloy was introduced for biological applications. The microstructural analysis showed the formation of MgZnCu intermetallics for the Mg-2Zn-0.1Cu alloy and also the Mg(Zn,Cu)2 compounds for the Mg-2 Zn alloys with higher Cu contents. Moreover, the hot extrusion was applied for the grain r...
Dendrite coherency or dendrite impingement is an important factor for determining solidification microstructure and casting defects of alloys. In this research, the effect of various cooling rates and Al-5Ti-1B grain refiner contents on the dendrite coherency point (DCP) characteristics of an Al-Si-Mg alloy designated as A357 has been studied. The...
A differential speed rolling (DSR) technique that provides capability of producing large-scale materials with fine grains and controlled texture in a continuous manner has attracted several researchers and industries. In this study, we tried to review the articles related to DSR and especially the high-ratio DSR (HRDSR) technique that is associated...
Effect of calcium (Ca) addition in a novel magnesium (Mg) alloy including zinc, aluminum,
and manganese from multimodal approaches was investigated to achieve a high strength
and low corrosion rate material. Tensile and compression tests were carried out to
measure the mechanical properties and precise analysis such as hydrogen evolution,
weight lo...
The present invention relates to a magnesium alloy comprising calcium (Ca) and manganese (Mn) as a main component, and having a very low corrosion rate and high yield strength by using a multi directional forging process. According to the present invention, the magnesium alloy is characterized in that a magnesium comprising 0.2-1.5 wt% of Ca and 0....
A new Mg alloy was cast, then extruded and finally MDFed at 180oC (MDF180) and 300oC (MDF300). The corrosion behavior was evaluated using the electrochemical and immersion techniques and mechanical property was assessed by using tension and compression tests. The microstructures were analyzed using OM, SEM, TEM, XRD and thermodynamic calculations a...
The present invention relates to a magnesium alloy and a method of manufacturing the same. According to one embodiment of the present invention, Zn: 3.0-6.0% by weight, Al: 0.0-3.0% by weight, Ca: 0.3-2.0% by weight, Mn: 0.1-1.5% by weight, the rest is magnesium and inevitable impurities And a magnesium alloy, processed in a screw rolling process.
Grain refinement and enhanced mechanical properties of Mg-2Zn-xCa alloys (with a wide range of calcium contents from 0 to 5 wt%) were studied in both as-cast and extruded conditions. It was revealed that Ca addition can effectively refine the grain size of the ingots based on the growth restriction factor (GRF) mechanism, where at high Ca additions...
This study investigates the cracking behavior of oxide layers formed on molten metals and alloys including pure zinc, Zn–4 wt%Al (ZAMAK3) and Al–(0.5–2) wt%Ca in dynamic oxidation condition by injecting gas bubbles into the molten metal during the pouring process. The crack characteristics of the oxide layers were studied using a field emission sca...
NiAl-TiC composites were synthesised by volume combustion (VC) method from elemental powders to improve the mechanical properties and high temperature performance of nickel aluminide. Synthesised specimens with porous nature were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (E...
NiAl-TiC composites were synthesised by volume combustion (VC) method from elemental powders to improve the mechanical properties and high temperature performance of nickel aluminide. Synthesised specimens with porous nature were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (E...
This book is about the dialect and folklore of people of Fashand.
The book is in persian.
The effect of Sr addition on corrosion behaviour of AZ31 was investigated. The corrosion properties were characterized by immersion, electrochemical, scanning Kelvin probe microscopy and microstructural experiments. With increasing Sr concentration, the Vf of Al-Sr precipitates increases. Furthermore, SKPFM results show that Al-Sr and Al-Mn precipi...
Surface turbulence during the filling of the mold triggers the entrainment of oxide films, which appears to be detrimental to the soundness of the final casting. Nonpressurized and bottom-gating systems have been employed in order to avoid such casting defects by reducing the surface velocity of the liquid metal. However, recent studies have shown...
Accepted paper: Understanding the occurrence of the surface turbulence in a nonpressurized
bottom gating system: Numerical simulation of the melt flow pattern
The present study investigated the effects of initial Hydrogen level and cooling rate on ultimate tensile strength of commercial Al-A319 alloys. Three hydrogen levels (0.01, 0.2, and 0.41 mL/100 grams of melt) and five cooling rate were studied. Total of 45 tensile test bars was prepared (three hydrogen levels × five cooling rate × three repeats)....
In vertical gravity casting, surface turbulence, the entrainment of oxide films into the bulk liquid cause detrimental effect on quality of production. For avoiding these defects, non-pressurized and bottom-gating systems are strongly recommended for reducing the surface velocity of the liquid metal entering into the mold cavity at the early stages...
A 2-D numerical model was developed to predict the shape of weld pool in stationary GTA welding of commercial pure aluminium, without considering fluid flow in the weld pool. A Gaussian current density and heat input distribution on the surface of the workpiece were considered. The parameters of Gaussian distribution were modified by comparing calc...
Effects of sprue base size and design on flow pattern during aluminum gravity casting have been investigated by employing different sprue base sizes and using computational fluid dynamics (CFD). Calculations was carried out using SUTCAST simulation software based on solving Navier-Stokes equation and tracing the free surface using SOLA-VOF algorith...
Effects of sprue base size and design on flow pattern during aluminum gravity casting have been investigated by employing different sprue base sizes and using computational fluid dynamics (CFD). Calculations was carried out using SUTCAST simulation software based on solving Navier-Stokes equation and tracing the free surface using SOLA-VOF algorith...
اين كتاب از مجموعه 4 جلدي متالورژي براي همه است كه توسط بخش انتشارات شركت مهندسي آرتاپژوهش كاوه تهيه شده است
اين كتاب با زباني كه براي همه متخصصان و مهندسان آشنا باشد، به بررسي مباني پايه اي شناخت مواد مي پردازد.
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...
While it is well recognized that microstructure controls the physical and mechanical prop-
erties of a material, the complexity of the microstructure often makes it difficult to be sim-
ulated by analytical or numerical techniques. In this paper we present a suitable approach
to compute microstructures within a casting using the finite element techniq...
Effects of surface turbulence on surface oxide folding have been studied numerically. Bifilms are an unfavorable nucleation sites for volume defects such as cracks, gas bubbles and shrinkage cavities. Major parameter promoting bifilm formation is surface turbulence. This parameter could be characterized by surface velocity exceeding a critical valu...
During the mold filling process, surface turbulence cause the entrainment of oxide films into the bulk liquid which are detrimental to the cast integrity. For avoiding these defects, non-pressurized and bottom-gating systems are strongly recommended for reducing the surface velocity of the liquid metal entering into the mold cavity at the early sta...
An official Persian translation of the Prof. John Campbell's 2nd reputed book, "Castings Practice: 10 Rules of Castings"
Filter has a significant effect on the gating system design. This tool in spite of simplicity and low cost profoundly affects the metallurgical quality of the cast part. This is due to the
gridding mechanism and tendency of laminar flow and removing inclusions when using
filters. In the present work the simulation of fluid flow with free surface...
Questions
Questions (28)
Usually people talk about anodic branch, however, there are some slope changes in the cathodic branch. would you please let me know what do the arrows in the attached file shows? I mean why the slope changes in those points?
We know Cr can form a stainless steel. But can one explains me a detail for this corrosion phenomena.
I will appreciate if you please consider the following items when you answer.
1. Pilling-bedworth (PB) ratio of Iron is 1.9 and hence it should be passive by its own. What is the main role of Cr/Cr2O3/Cr(OH)2 on the surface film? why this Cr containg layer is passive while Cr-free layer is not?
For different purposes, molten metals will be in contact with a ceramic material. For example a furnace nozzle guides the melt flow to the mold is usually made from a thermo-chemical resistant ceramic.
- However, in the case of Mg metal, chemical reactions and temperature drop are very fast.
- Beside, mechanical strength and elongation must be high enough to suffer mechanical shocks.
- Moreover, machinability and density of a ceramic material must be good enough to form in the desired shape.
I will highly appreciate if you let me know your answers and reasons in this regard.
#Magnesium
#Oxidation
#Flamability
#
Best regards,
Anybody can help me how I should I open and analyze the microCT files with the extension of "dcm"?
I opened the file from a studied bone using a software called "File Viewer Lite" and opened the file as it is shown in the attached image. But it seems it is one of the cross section of the studied bone and unfortunately, it is one the images among ~500 images and all images need to be opened individually which may cause I can not recognize where should I focus.
Is there any software that can help in this regard?
any comment and opinion is very very welcomed.
#microCT
#invivo
#Implant
#ImageAnalysis
#CT
#Computerized
#tomography
Dear Researchers,
Hope all be safe and healthy and far from Covid-19,
I would like to ask your opinion about you overall purpose of doing research.
Throughout the history, researchers have tried to discover our world's physical phenomena. There must be several reasons behind of these researches such as curiosity, power, fame, humanity and so on.
I will appreciate if you let me know your reason for the research.
It is very important to understand the real reason of our researches and designing our future research map.
Best wishes,
I am looking for the statistical graphs or data showing how much wrought Mg alloys is produced in the world. The graph may compare the cast and wrought alloys. Any data in this regard is appreciated.
I found some graphs like this but it does not show the contribution of wrought Mg alloys in the whole market.
Best regards,
#Magnesium
#Magnesium_Alloy
#Mg
#Wrought_Alloy
#Statistics