Search published articles


Showing 509 results for in

A. Bahrami, M. R. Hosseini, M. Pazouki,
Volume 6, Issue 4 (12-2009)
Abstract

Abstract:

point of view. In this study, a shaking-table was used for concentrating a manganese ore sample from the Ghasem Abad

area in Kerman, Iran. Experiments were designed by using L

The influence of each variable and their interactions on the operation of the device was studied. The variables under

investigation were: table slope, table frequency, water flowrate, feed rate, and particle size. The manganese

concentrate grade, recovery, and separation efficiency were used as response variables. It was shown that water

flowrate, table slope, feed rate, and particle size are the significant variable on concentrate grade while, all the

variables influence manganese recovery. Also, water flowrate, table slope, and table frequency have an important

effect on manganese separation efficiency. Finally, three mathematical models were presented to predict the values of

each response variables.

Among all gravity concentration methods, the shaking-table is the most effective one from the metallurgical8 Taguchi design with five variables, each in two levels.

M. Esmailian,
Volume 7, Issue 1 (3-2010)
Abstract

Abstract:

transformation temperature and different ferrite morphologies in one Nb-microalloyed (HSLA) steel has been

investigated. Three different austenite grain sizes were selected and cooled at two different cooling rates for obtaining

austenite to ferrite transformation temperature. Moreover, samples with specific austenite grain size have been

quenched, partially, for investigation on the microstructural evolution.

In order to assess the influence of austenite grain size on the ferrite transformation temperature, a temperature

differences method (TDM) is established and found to be a good way for detection of austenite to ferrite, pearlite and

sometimes other ferrite morphologies transformation temperatures.

The results obtained in this way show that increasing of austenite grain size and cooling rate has a significant influence

on decreasing of the ferrite transformation temperature.

Micrographs of different ferrite morphologies show that at high temperatures, where diffusion rates are higher, grain

boundary ferrite nucleates. As the temperature is lowered and the driving force for ferrite formation increases,

intragranular sites inside the austenite grains become operative as nucleation sites and suppress the grain boundary

ferrite growth. The results indicate that increasing the austenite grain size increases the rate and volume fraction of

intragranular ferrite in two different cooling rates. Moreover, by increasing of cooling rate, the austenite to ferrite

transformation temperature decreases and volume fraction of intragranular ferrite increases.

The effect of different austenite grain size and different cooling rates on the austenite to ferrite

A. R. Hanifi,, A. Genson, M. J. Pomeroy, S. Hampshire,
Volume 7, Issue 1 (3-2010)
Abstract

Oxynitride glasses are found as grain boundary phases in silicon nitride ceramics. They are effectively alumino-silicate glasses in which nitrogen substitutes for oxygen in the glass network, and this causes increases in glass transition and softening temperatures, viscosities (by two to three orders of magnitude), elastic moduli and microhardness. Calcium silicate-based glasses containing fluorine are known to have useful characteristics as potential bioactive materials. Therefore, the combination of both nitrogen and fluorine additions to these glasses may give useful glasses or glass-ceramics with enhanced mechanical stability for use in biomedical applications. This paper reports glass formation and evaluation of glass thermal properties in the Ca-Si-Al-O-N-F system. Within the previously defined Ca-Si-Al-O-N glass forming region at 20 eq.% N, homogeneous, dense glasses are formed. However, addition of fluorine affects glass formation and the reactivity of glass melts. This can lead to fluorine loss as SiF4, and also nitrogen loss, leading to bubble formation and porous glasses. The compositional limits for both dense
and porous glass formation at 20 eq.% N and 5 eq.% F have been mapped. At high fluorine contents under conditions when Ca-F bonding is favoured, CaF2 crystals precipitate in the glass. The role of the different cations on glass formation in these oxyfluoro-nitride glasses is discussed.


R. Khoshhal, M. Soltanieh, M. Mirjalili,
Volume 7, Issue 1 (3-2010)
Abstract

Abstract:

titanium sheets in pure molten aluminum at 750

and X-Ray Diffraction Analysis results, TiAl

intermetallic layer thickness increases slowly at primary stages. After that an enhanced growth rate occurs due to layer

cracking and disruption. Presumably, reaction starts with solving titanium into the molten aluminum causing in

titanium super saturation and TiAl

intermetallic layer which consequently leads to TiAl

energy of intermetallic layer formation and growth was developed by measuring titanium thickness decreases.

In this work, kinetics of intermetallic compounds formation in Al-Ti system was studied by immersingoC, 850 oC and 950 oC. According to Scanning Electron Microscopy3 is the only phase can form at the interface. Observations revealed that3 formation. At this stage, growth may be controlled by aluminum diffusion through3 formation at the interface of Ti-TiAl3. Furthermore, activation

A. H. Shafie Farhood, F. Akhlaghi,
Volume 7, Issue 1 (3-2010)
Abstract

Abstract:

structures in alloys. This method is based on pouring the melt through a small sized nozzle into a mould located at a

certain height under the crucible. This simple method generates globular structures without using equipments such as

impellers, electromagnetic stirrers, ultrasonic probes and cooling slopes. Therefore it is cost effective. In the present

study, the effect of casting size and mould casting modulus on the globular structure evolution in A356 aluminium alloy

specimens prepared by NMS process was investigated. The results showed that regardless of the different casting

modulus and their sizes, all the specimens exhibited globular structures. However, the size and shape factor of the

globules decreased with increased casting modulus and casting size indicating the influential effect of the surface area

of the mould in generating globular structures in this process.

Narrow Melt Stream (NMS) is a relatively new semisolid metal processing technique for producing globular

M. Banoee,z. Ehsanfar, N. Mokhtari,m. R. Khoshayand, A. Akhavan Sepahi, P. Jafari Fesharaki,h. R. Monsef-Esfahani,, A. R. Shahverdi,
Volume 7, Issue 1 (3-2010)
Abstract

Abstracts:

nanoparticles. All the extracts were used separately for the synthesis of gold nanoparticles through the reduction of

aqueous AuCl

gold ions to gold nanoparticles. The ethanol extract of black tea and its tannin free ethanol extract produced gold

nanoparticles in the size ranges of 2.5-27.5 nm and 1.25-17.5 nm with an average size of 10 nm and 3 nm, respectively.

The prepared colloid gold nanoparticles, using the ethanol extract of black tea, did not show the appropriate stability

during storage time (24 hours) at 4

showed no particle aggregation during short and long storage times at the same conditions. To the best of our

knowledge, this is the first report on the rapid synthesis of gold nanoparticles using ethanol extract of black tea and

its tannin free fraction.

In this research the ethanol extract of black tea and its tannin free fraction used for green synthesis of gold4¯. Transmission electron microscopy and visible absorption spectroscopy confirmed the reduction ofoC. In contrast, gold colloids, which were synthesized by a tannin free fraction

M. Adeli, M. Shekari, S. H. Seyedein, M. R. Aboutalebi,
Volume 7, Issue 2 (6-2010)
Abstract

Combustion synthesis is a special thermophysico-chemical process applied for production of intermetallic compounds. In the present work, a reaction–diffusion numerical model was developed to analyze the combustion synthesis of aluminide intermetallics by self-propagating high-temperature synthesis process. In order to verify the reliability of the numerical model, an experimental setup was designed and used to perform the combustion synthesis of nickel and titanium aluminides. The developed model was further used to determine the temperature history of a powder mixture compact during self-propagating high-temperature synthesis. The effect of compact relative density on combustion temperature and wave propagation velocity was also studied.


A.m. Rashidi, A. Amadeh,
Volume 7, Issue 2 (6-2010)
Abstract

Abstract:

nanocrystalline nickel samples with the grain size of ~25 nm were prepared via direct current electrodeposition and

aluminized for different durations by pack cementation method at 500

means of SEM, EDS and XRD techniques. According to results, short time aluminizing resulted in the formation of a

single aluminide layer whereas at long duration two distinct aluminide layers were formed. The growth kinetics of the

coating was non-parabolic at short times while it obeyed the parabolic law at long duration. The parabolic growth

rate constant of single phase coating formed on electrodeposited samples was about 30 ìm / h1/2 approximately 3 times

greater than the data reported for coarse grained nickel (8.4 ìm / h1/2). Meanwhile, the overall growth rate constant

was decreased to 11.7 ìm / h1/2, when double aluminide layers formed on nanocrystalline nickel.

In this research, aluminizing behavior of ultra fine-grained nickel was investigated. For this purpose,oC. The aluminide layers were examined by

N. Anjabin, Karimi Taheri,
Volume 7, Issue 2 (6-2010)
Abstract

Abstract:

properties of AA6082 aluminum alloy. Considering that aging phenomenon affects the distribution of alloying element

in matrix, and the fact that different distribution of alloying elements has different impediments to dislocation

movement, a material model based on microstructure, has been developed in this research. A relative volume fraction

or mean radius of precipitations is introduced into the flow stress by using the appropriate relationships. The GA-based

optimization technique is used to evaluate the material constants within the equations from the uni-axial tensile test

data of AA6082 alloy. Finally, using the proposed model with optimized constants, the flow behavior of the alloy at

different conditions of heat treatment is predicted. The results predicted by the model showed a good agreement with

experimental data, indicating the capability of the model in prediction of the material flow behavior after different heat

treatment cycles. Also, the calculated flow stress was used for determination of the material property in Abaqus

Software to analyze the uniaxial compression test. The force- displacement curves of the analysis were compared to

the experimental data obtained in the same condition, and a good agreement was found between the two sets of results.

A novel constitutive equation has been proposed to predict the effect of aging treatment on mechanical

M.sh. Bafghi, A.h. Emami, A. Zakeri, J. Vahdati Khaki,
Volume 7, Issue 2 (6-2010)
Abstract

Abstract:

has been investigated. It has been shown that the mechanism of leaching reaction is diffusion through the product layer

and does not undergo any change as a result of mechanical activation in a wide range of experimental conditions.

Leaching rate is strongly influenced by milling intensity and the effect of ball to powder mass ratio is stronger than

milling time. Curve fitting of experimental data shows that leaching rate constant is approximately a linear function

of ball to powder mass ratio, while it obeys a power function with regard to the milling time.

The kinetics of chalcopyrite leaching in a ferric sulfate media for raw and mechanically activated samples

K. Christine Stella, A. Samson Nesaraj,
Volume 7, Issue 2 (6-2010)
Abstract

Abstract:

as magnetic materials, semiconductors, pigments, catalysts, refractories and electronic ceramics. In this paper, we

reported the preparation of NiAl

The resulting powder was chracterized by XRD, particle size analysis and SEM. The XRD patterns show that the

combustion technique was excellent to prepare single – phased cubic NiAl

found to be around 14 nm. From the particle size analysis, it was found that the 50 % of the particles lie below 30

µm. The micrographs show the formation of fluffy agglomerates composed of fine particles.

Spinels constitute an advanced group of materials with great technologial appeal, being able to be applied2O4 spinels by low temperature combustion technique using glycine and urea as fuels.2O4 particles and the crystallite sizes were

M. Nusheh*, H. Yoozbashizadeh,
Volume 7, Issue 2 (6-2010)
Abstract

Abstract:

the competition between the precipitation of cobalt ions and evolution of hydrogen gas on the cathode surface during

the reduction process in a sulfate bath, investigation on the mechanism of metal precipitation is of great importance.

In the present work, study on the kinetics of cobalt electrowinning and the mechanism of the involved reactions have

been carried out. The obtained results, confirm the mechanism of cobalt precipitation by depletion of hydroxides. The

effects of temperature and scan rate parameters were studied on electrowinning of cobalt by cyclic voltammetry

technique. The diffusion coefficient and rate constant of the reactions were measured and calculated by performed

experiments.

Nowadays cobalt is mostly produced through the electrowinning process of sulfate solutions. Regarding to

Mr Mohammadtaher Safarzadeh, Mr Seyed Mohammad Ali Boutorabi, Mr Asghar Arab,
Volume 7, Issue 3 (8-2010)
Abstract

The effects of anodizing condition and post treatment on the growth of nickel nanowires, were investigated. A two-step anodizing process was applied in phosphoric and oxalic acid solution. Nickel electrochemical plating was applied to fill Anodic Aluminum Oxide (AAO) pores. For pore filling enhancement, AAO surfaces were treated by silver predeposition. After electroplating, aluminum and oxide layer of some specimens were removed. The results showed that silver preplating increases the pore filling and as the applied voltage becomes higher, the pores diameter decreases.
Saber Khoshjavan, Mohammad Heidary, Dr Bahram Rezai,
Volume 7, Issue 3 (8-2010)
Abstract

Free swelling index (FSI) is an important parameter for cokeability and combustion of coals. In this research, the effects of chemical properties of coals on the coal free swelling index were studied by artificial neural network methods. The artificial neural networks (ANNs) method was used for 200 datasets to estimate the free swelling index value. In this investigation, ten input parameters such as moisture, volatile matter (dry), fixed carbon (dry), ash (dry), total sulfur (organic and pyretic)(dry), (British thermal unit (Btu)/lb) (dry), carbon (dry), hydrogen (dry), nitrogen (dry) as well as oxygen (dry) were used. For selecting the best model for this study the outputs of models were compared. A three-layer ANN was found to be optimum with architecture of ten and four neurons in first and second hidden layer, respectively, and one neuron in output layer. Results of artificial neural network shows that training, testing and validating data’s square correlation coefficients (R2) achieved 0.99, 0.92 and 0.96, respectively. The sensitivity analysis showed that the highest and lowest effects of coal chemical properties on the coal free swelling index were nitrogen (dry) and fixed carbon (dry), respectively. Keywords: Coal Chemical Properties, Free Swelling Index, Artificial Neural Networks (ANNs), Cokeability and Back Propagation Neural Network (BPNN).
Mrs Somaye Alamolhoda, Dr Saeed Heshmati-Manesh, Dr Abolghasem Ataie,
Volume 7, Issue 3 (8-2010)
Abstract

In this research an ultra-fine grained composite structure consisting of an intermetallic matrix together with dispersed nano-sized Al2O3 obtained via mechanical activation of TiO2 and Al in a high energy ball mill and sintering of consolidated samples. Phase composition and morphology of the milled and sintered samples were evaluated by XRD and SEM techniques Thermal behavior of the powder sample milled for 8 hours was evaluated by DTA technique. DTA results showed that, the reaction happens in two steps. The first step is the aluminothermic reduction of TiO2 with Al. XRD observations reveals that minor amount of Ti3Al phase formed during reduction reaction together with TiAl and Al2O3 major phases. This intermetallic phase disappeared when sintering temperature was increased to 850 ºC. The second step in DTA is related to a reaction between residual Al in the system (partly dissolved in TiAl lattice) and the Ti3Al phase produced earlier at lower temperatures. SEM micrographs reveal that by completion of the reduction reaction more homogeneous and finer microstructure is observable in sintered samples.
Khodamorad Abbaszadeh, Shahram Kheirandish, Hassan Saghafian,
Volume 7, Issue 3 (8-2010)
Abstract

The effects of lower bainite volume fraction on tensile and impact properties of D6AC ultrahigh strength steel were studied in the current work. To obtain mixed microstructures containing martensite and different volume fractions of the lower bainite, specimens were austenitized at 910° C, then quenched in a salt bath of 330°C for different holding times, finally quenched in oil. In order to obtain fully martensitic and bainitic microstructures, direct oil quenching and isothermal transformation heat treatment for 24 hours were used respectively. All specimens were double tempered at 200°C for 2 hours per tempered. Microstructures were examined by optical and scanning electron microscopes. Fracture morphologies were studied by scanning electron microscopy (SEM). Results showed that both yield and ultimate tensile strength generally decreased with an increase in volume fraction of lower bainite. However, a few exceptions were observed in the mixed microstructures containing 12% lower bainite, showing a higher strength than the fully martensitic microstructure. This can be explained on the basis of two factors. The first is an increase in the strength of martensite due to the partitioning of the prior austenite grains by lower bainite resulting in the refinement of martensite substructures. The second is a plastic constraint effect leading to an enhanced strength of lower bainite by the surrounding relatively rigid martensite. Charpy V-notch impact energy and ductility is improved with increasing the volume fraction of lower bainite.
A. Jafaria, S. H. Seyedeina, M. R. Aboutalebia, D. G. Eskinb, L. Katgermanb,
Volume 7, Issue 3 (8-2010)
Abstract

ABSTRACT Macrosegregation has been received high attention in the solidification modeling studies. In the present work, a numerical model was developed to predict the macrosegregation during the DC Casting of an Al-4.5wt%Cu billet. The mathematical model developed in this study consists of mass, momentum, energy and species conservation equations for a two-phase mixture of liquid and solid in an axisymmetric coordinates. The solution methodology is based on a standard Finite Volume Method. A new scheme called Semi-Implicit Method for Thermodynamically-Linked Equations (SIMTLE) was employed to link energy and species equations with phase diagram of the alloying system. The model was tested by experimental data extracted from an industrial scale DC caster and a relatively good agreement was obtained. It was concluded that a proper macrosegregation model needs two key features: a precise flow description in the two-phase regions and a capable efficient numerical scheme
Z. Ghaferi, K. Raeissi, M. A. Golozar,, A. Saatchi, S. Kabi,
Volume 7, Issue 4 (10-2010)
Abstract

Abstract:

current densities. Electrochemical impedance spectroscopy (EIS) results showed that the codeposition mechanism of

tungsten in Ni-W deposition is the reduction of tungsten oxide which changed to the reduction of tungsten-containing

ion complexes at higher current densities. In Co-W electrodeposition, the tungsten codeposition takes place via

reduction of tungsten oxide, although, the role of tungsten-containing complexes at higher current densities cannot be

ruled out. The surface morphology of Ni-W coatings was crack-free and was strongly dependent on deposition current

density. In addition, higher grain size and lower tungsten content were obtained by increasing the current density. In

Co-W coatings, no obvious variation in surface morphology was observed except for the fine cracks appeared at

higher current densities. In this system the grain size remained almost constant with increasing current density. The

microhardness values of Ni-W and Co-W coatings decreased due to the increase in the grain size and/or decrease in

tungsten content.

Ni-W and Co-W alloy nanocrystalline coatings were electrodeposited on copper substrate at different

H. Rafiee*,, S. Rastegari, H. Arabi, M. Mojaddami,
Volume 7, Issue 4 (10-2010)
Abstract

Abstract:

activity gas diffusion process has been investigated in this research. Effects of coating temperature and aluminum

concentration in powder mixture on formation mechanism were studied using optical and scanning electron

microscopes, EDS and X-ray diffraction (XRD) techniques. For this purpose two different packs containing 1 and 2

wt% aluminum powder, were used for coating the samples at two temperatures, 850ºC and 1050ºC. The ratio of Al to

activator was kept constant in both packs. By increasing the Al content in high activity powder mixture, the

concentration of diffused Al increased in the coating layers, and the thickness of coating increased. At 1050ºC as the

rate of diffused Al to the interdiffusion zone increased, this zone gradually transformed to outer coating phases. At

850ºC coating formed by inward diffusion of Al, but at 1050ºC it was initially formed by inward diffusion of Al followed

by outward diffusion of Ni.

Formation mechanism of an aluminide coating on a nickel base superalloy IN738LC via a single step high

Y. Fouad,
Volume 7, Issue 4 (10-2010)
Abstract

Abstract: Rotating bending fatigue tests have been performed using smooth specimens of a rolled AZ31 magnesium alloy in laboratory air at ambient temperature. Fatigue strength and characteristic was evaluated and fracture mechanism was discussed on the basis fracture surface analysis. Electrical polishing (EP) as well as deep rolling (ball burnishing (BB)) U-notched specimens were performed on two groups of samples, to evaluate optimum conditions for fatigue life. The microstructure and tensile properties of roll cast (RC) Mg- 3% Al- 1% Zn (AZ31) was investigated. The fatigue strength of 107 cycles around 100 MPa for deep rolling while it was around 40 MPa for Electrical polishing. It was very important to understand the effect of (ball burnishing (BB)) conditions on the hardness of the surface through to the core. The two procedures improved the fatigue performance, but better improve in results were found in ball burnishing. The growth of small cracks initiated at the surface coincided with the FCP characteristic after allowing for crack closure for large cracks, but the operative fracture mechanisms were different between small and large cracks. At the subsurface crack initiation site, smooth facets were always present regardless of applied stress level.

Page 6 from 26     

© 2022 All Rights Reserved | Iranian Journal of Materials Science and Engineering

Designed & Developed by : Yektaweb