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M. Rezvani, B. Eftekhari Yekta, V. K. Marghussian,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: The application of inexpensive materials such as copper, zinc, lead, iron and steel slag in
manufacturing of glass and glass-ceramic products in construction industry, lining materials as
anti-corrosion and anti-abrasion coatings in metals and etc, has led to considerable progress in
glass technology in recent years. The composition of slag glass-ceramics is mainly located in the
SiO2-Al2O3-CaO-MgO system, in which one of the most important problems is the lack of bulk
crystallization. To resolve the above-mentioned problem, the crystallization behavior of various
compositions containing different nucleating agents Cr2O3 , Fe2O3 and TiO2 in the single, double
and triple forms were studied by differential thermal analysis (DTA).The precipitated crystalline
phases was determined by the X-ray diffractometry and the micro-structural analysis was studies
using the SEM micrographs. The three point bending strength, micro-hardness and the chemical
resistance of the best composition were determined. According to the results, the resulted glassceramic
had a better specification than the stoneware floor tiles and the porcelain one, which are
considered as the two important competitors for it.
A. Ataie1,, S. Heshmati-Manesh1,, S. Sheibani1,, G. R. Khayati,y. Firozbakht,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: In this paper solid state reduction of high carbon ferrochromium-chromite composite
pellets in the temperature range of 900-1350°C was investigated. A two stage reduction
mechanism is proposed. The first stage is likely to be controlled by the chemical reaction with
activation energy of 127.2kJ/mol. In the second stage, solid state diffusion of carbon through the
reaction product layer is suggested to be rate controlling. The activation energy of this stage was
calculated to be 93.1kJ/mol. The reduction process was found to be favored by high temperatures
as well as high vacuum. The results also show that pre-milling of initial mixture has a negative
effect on the reduction degree.
M. Kazemi Pour, S. Sharafi,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: Hardfacing is one of the most useful and economical ways to increase the service life of
components subjected to abrasive wear. Iron based hardfacing alloys have long been considered
as candidate coatings for wear-resistant applications in industry. In the present work two layer of
Fe-34Cr-4.5C%wt hardfacing alloy was deposited on ASTM A36 carbon steel plates by SMAW
method. The microstructure consists of large primary and eutectic M7C3 carbides, metastable
austenite and small amount of secondary carbides. The microstructure was analyzed by optical
and scanning electron microscopes. In the same condition of size, shape, distribution and volume
fraction of carbides the as-welded matrix changed to martensite, tempered martensite and ferrite
by heat treatment processes. The wear resistance was measured by pin-on-disk method under loads
of 5, 10 and 20N and for sliding distance of 1500m. The results showed that the as-welded sample
with austenitic matrix has the most and the ferritic matrix specimen has the least wear resistance.
The predominate mechanisms for mass losses were determined to be micro-cutting, microploughing.
C. Dehghanian, Y. Mirabolfathi Nejad,
Volume 5, Issue 1 (3-2008)
Abstract
Abstract: Despite having a number of advantages, reinforced concrete can suffer rebar corrosion
in high–chloride media, resulting in failure of reinforced concrete structures. In this research the
corrosion inhibition capability of the mixture of calcium and ammonium nitrate of steel rebar
corrosion was investigated in the simulated concrete pore solution. Cyclic polarization and
Electrochemical Impedance Spectroscopy (EIS) techniques were applied on steel concrete pore
solution containing 2 weight percent sodium chloride (NaCl). Results show that such mixtures had
higher inhibition efficiency than calcium nitrate alone. The optimum concentration of the inhibitor
mixture was determined to be 45 mgr/lit.
A. R. Kamali, S. M. M. Hadavi, H. Razavizadeh, J. Fahim,
Volume 5, Issue 2 (6-2008)
Abstract
Abstract: Production of titanium aluminides in TiO2-Al-Ca system has been investigated. For this
purpose, different compositions of raw materials were studied in a special reaction vessel. In a
special case, the non-completed reaction of TiO2 with Al and Ca resulted in the production of
granulates of titanium aluminides especially Ti3Al and other Ti – Al phases as the metallic product
and Ca12Al14O33 as the non-metallic product. Remelting of metallic granulates led to production of
TiAl ingot.
A. Hassani, R. Ravaee,
Volume 5, Issue 2 (6-2008)
Abstract
Abstract: To ensure the rail transportations safety, evaluation of fatigue behavior of the rail steel
is necessary. High cycle fatigue behaviour of a rail steel was the subject of investigation in this
research using fracture mechanics. Finite element method (FEM) was used for analyzing the
distribution of the stresses on the rail, exerted by the external load. FEM analysis showed that the
maximum longitudinal stresses occurred on the railhead. To find out about the relation of crack
growth with its critical size, and to estimate its lifetime, the behaviour of transverse cracks to rail
direction was studied using damage tolerance concept. It revealed that transverse crack growth
initially occurred slowly, but it accelerated once the crack size became larger. Residual service
life was calculated for defective segments of the rails. In addition, allowable crack size for
different non-destructive testing intervals was determined the allowable crack size decreased as
the NDT intervals increased.
A. Allahverdi, E. Najafi Kani, S. Esmaeilpoor,
Volume 5, Issue 2 (6-2008)
Abstract
Abstract: The use of alkali-activated cementitious materials especially over the past decades has
significantly been increased. The goal of this research is to investigate the effects of silica modulus
and alkali concentration on alkali-activation of blast-furnace slag. In this research, the most
important physical characteristics of cementitious systems, i.e. the 28-day compressive strength
and final setting time, were studied by changing influencing parameters such as silica modulus,
i.e. SiO2/Na2O, (0.44, 0.52, 0.60, and 0.68) and Na2O concentration (4, 6, 8 and 10% by weight of
dry binder) at a constant water-to-dry binder ratio of 0.25. Final setting time of the studied
systems varies in the range between 55-386 minutes. The obtained results show that systems cured
at an atmosphere of more than 95% relative humidity at room temperature exhibit relatively high
28-day compressive strengths up to 107 MPa.
A. Moosavi, A. Aghaei,
Volume 5, Issue 2 (6-2008)
Abstract
Abstract: Auto-ignited gel combustion process has been used for producing a red hematite-zircon
based pigment. The combustible mixtures contained the metal nitrates and citric acid as oxidizers
and fuel, respectively. Sodium silicate (water glass) was used as silica source for producing zircon
phase. X-Ray Diffractometery, Electron Microscopy and Simultaneous Thermal Analysis were used
for characterization of reactions happened in the resulted dried gel during its heat-treatment.
L* a* b* color parameters were measured by the CIE (Commission International de I'Eclairage)
colorimetric method. This research has showed that solution combustion was unable to produce
coral pigment as the end product of combustion without the need for any further heat treatment
process.
William L. Headrick,, Alireza Rezaie, William G. Fahrenholtz,
Volume 5, Issue 2 (6-2008)
Abstract
gasification (BBLG). One particularly harsh application is linings for gasifiers used in the
treatment of black liquor (BL). Black liquor is a water solution of the non-cellulose portion of the
wood (mainly lignin) and the spent pulping chemicals (Na2CO3, K2CO3, and Na2S). Development
of new refractory materials for the black liquor gasification (BLG) application is a critical issue
for implementation of this technology. FactSage® thermodynamic software was used to analyze
the phases present in BL smelt and to predict the interaction of BL smelt with different refractory
compounds. The modeling included prediction of the phases formed under the operating
conditions of high temperature black liquor gasification (BLG) process. At the operating
temperature of the BLG, FactSage® predicted that the water would evaporate from the BL and that
the organic portion of BL would combust, leaving a black liquor smelt composed of sodium
carbonate (70-75%), potassium carbonate (2-5%), and sodium sulfide (20-25%). Exposure of
aluminosilicates to this smelt leads to significant corrosion due to formation of expansive phases
with subsequent cracking and spalling. Oxides (ZrO2, CeO2, La2O3, Y2O3, Li2O, MgO and CaO)
were determined to be resistant to black liquor smelt but non-oxides (SiC and Si3N4) would oxidize
and dissolve in the smelt. The other candidates such as MgAl2O4 and BaAl2O4 were resistant to
sodium carbonate but not to potassium carbonate. LiAlO2 was stable with both sodium carbonate
and potassium carbonate. Candidate materials selected on the basis of the thermodynamic
calculations are being tested by sessile drop test for corrosion resistance to molten black liquor
smelt. Sessile drop testing has confirmed the thermodynamic predictions for Al2O3, CeO2, MgO
and CaO. Sessile drop testing showed that the thermodynamic predictions were incorrect for ZrO2.
M. Divandari,, H. Arabi, H. Ghasemi Mianaei,
Volume 5, Issue 3 (9-2008)
Abstract
Abstract: Thermal fatigue is a stochastic process often showing considerable scatter even in
controlled environments. Due to complexity of thermal fatigue, there is no a complete analytical
solution for predicting the effect of this property on the life of various components, subjected to
severe thermal fluctuations. Among these components, one can mention car cylinder, cylinder head
and piston which bear damages due to thermal fatigue. All these components are usually produced
by casting techniques. In order to comprehend and compare the thermal fatigue resistance of cast
Al alloys 356 and 413, this research was designed and performed. For this purpose, several
samples in the form of disc were cast from the two alloys in sand mould. The microstructures of the
cast samples were studied by light microscopy in order to choose the samples with the least
amounts of defects for thermal fatigue tests. The results of thermal fatigue tests showed that the
nucleation of microcracks in Al-356 alloy occurred at shorter time relative to those occurred in Al-
413 alloy under the same test conditions. In addition, the density of micro-cracks in Al-356 alloy
was more than that of Al-413 alloy. The results of fractography on 356 alloy indicated that the
cracks were generally nucleated from inter-dendritic shrinkage porosities and occasionally from
the interface of silicon particles with the matrix. The growth of these micro cracks was along the
dendrite arms. Fractography of 413 alloy fracture surfaces showed that nucleation of microcracks
was often associated with silicon particles.
H. Naffakh,, M. Shamanian, F. Ashrafizadeh,
Volume 5, Issue 3 (9-2008)
Abstract
Abstract: The investigation is carried out to characterize welding of AISI 310 austenitic stainless
steel to Inconel 657 nickel-chromium superalloy. The welds were produced using four types of
filler materials: the nickel-based corresponding to Inconel 82, Inconel A, Inconel 617 and
austenitic stainless steel 310. This paper describes the effects of aging treatment on the joint. The
comparative evaluation was based on microstructural features and estimation of mechanical
properties. While Inconel A exhibited highest thermal stability and mechanical properties
(hardness and ultimate strength), Inconel 82 weld metal also showed good thermal stability and
mechanical properties. On the other hand, welds produced with Inconel 617 and 310 SS filler
materials showed weak thermal stability and failed in the weld metals. It is therefore concluded
that for the joint between Inconel 657 and 310 stainless steel, Inconel A and Inconel 82 filler
materials offered the best compromises, respectively.
M. Ghalambaz, M. Shahmiri,
Volume 5, Issue 3 (9-2008)
Abstract
Abstract: Cooling slope-casting processing is a relatively new technique to produce semisolid cast
feedstock for the thixoforming process. Simple equipment, ease of operation, and low processing
costs are the main advantages of this process in comparison with existing processes such as
mechanical stirring, electromagnetic stirring, etc. The processing parameters of cooling slope
casting are length, angle and the material of the inclined plate and their combinations, which
usually affect the micro structural evolutions of the primary solid phase.
In order to clarify the effect of the processing parameters on the evolution of the particle size,
based on experimental investigation, Artificial Neural Network (ANN) was applied to predict the
primary silicon crystals (PSCs) size of semisolid cast ingot via a cooling slope casting process of
Al-20%(wt.%) Si alloy.
The results demonstrated that the ANN, with 2 hidden layers and topology (4, 3), could predict the
primary particle size with a high accuracy of 94%. The sensitivity analysis also revealed that
material of the cooling slope had the largest effect on particle size.
M. Keyanpour-Rad, S. Keyanpour-Rad,
Volume 5, Issue 3 (9-2008)
Abstract
Abstract: A novel dust free alginate impression material was formulated and prepared, comprising
an alginate polyvinylpyrrolidone and tetraflouroethylene resins, a mixture of liquid paraffin and
dimethylpolysiloxane oil as the dust generation controlling agents and processed diatomaceous
earth filler which was obtained from Iranian ore. No dusting was detected during the mixing of the
powder and the conventional properties of the impression material, like working and setting times
and compressive strength were in the range of the required specifications for alginate dental
impressions. The compressive strength was measured to be 2.6 times of the minimum requirement
for such fast setting impressions.
A. Poladi, M. Zandrahimi,
Volume 5, Issue 3 (9-2008)
Abstract
Abstract: Austenitic stainless steels exhibit a low hardness and weak tribological properties. The
wear behaviour of austenitic stainless steel AISI 316 was evaluated through the pin on disc
tribological method. For investigating the effect of wear on the changes in microstructure and
resistance to wear, optical microscopy and scanning electron microscope were used. The hardness
of the worn surfaces was measured with a micro-hardness tester. Worn surfaces were analyzed
through X-ray diffraction. Results showed that with increasing the sliding distance and applied
load, the austenite phase partially transformed to ά martensite, and there was no trace of ε phase
detected. Due to the formation of probably hard and strong martensite phase, as the sliding
distance and applied load increased, the hardness and the wear resistance of the material was
increased. Wear mechanism was on the base of delamination and abrasion.
M. Shahmiri, S. Murphy,
Volume 5, Issue 4 (12-2008)
Abstract
Abstract: The microstructural features of the early stage of ordering of the intermetallic compound Pt2FeCu have been
examined using optical and transmission electron microscopy in conjunction with X-ray diffraction technique. It was
found that the compound has similar morphological alteration to that of FePt in which the ordering cannot be
suppressed by rapid quenching.
The early stage of ordering transformation was initiated at temperatures above the critical value of 1178 oC, by a
homogeneous nucleation of the intermediate short range ordered particles and ultra rapid directional-induced
heterogeneous growth (burst type). As the result of these combined mechanisms, twin –related ordered domains have
been formed which in turn minimize the strains produced by ordering reaction in polycrystalline material. The
individual grain was divided up by different sizes of twin-related ordered domain bonded with {101} habit planes.
S. Kianfar,, S. H. Seyedein, M. R.aboutalebi,
Volume 5, Issue 4 (12-2008)
Abstract
Abstract: The horizontal continuous casting process has received a significant attention for near net shape casting of
non ferrous metals and alloys. Numerical Simulation has been widely used for process design and optimization of
continuous casting process.
In the present study, a 3-dimensional heat flow model was developed to simulate the heat transfer and solidification in
a horizontal billet continuous casting system in which the air gap formation and its effect on heat extraction rate from
solidifying billet was also considered. In order to test the developed model, it was run to simulate the heat transfer
and solidification for an industrial billet caster. The predicted temperature distribution within the mold and billet was
compared with those measured on the industrial caster in which a good agreement was obtained.
Finally, parametric studies were carried out by validated model to evaluate the effects of different parameters on
solidification profile and temperature distribution within the model brass billet. The microstructure of cast billet was
analyzed to determine the secondary dendrite arm spacing (SDAS) under different cooling conditions. Based on
measured SDAS and predicted solidification rate a correlation between SDAS and cooling rate was proposed for
continuously cast brass billet.
H. Shahmir, M. Nili Ahmadabadi, F. Naghdi,
Volume 5, Issue 4 (12-2008)
Abstract
Abstract: In the present study the effect of thermomechanical treatment (cold work and annealing) on the
transformation behavior of NiTi shape memory alloys was studied. Differential scanning calorimetry was used to
determine transformation temperature and its relation to precipitates and defects. Three alloys including Ti-50.3at.%
Ni, Ti-50.5at.% Ni (reclamated orthodontic wires) and 50.6at.% Ni alloy were annealed at 673 K and 773 K for 30
and 60 min after 15% cold rolling. It was found that the transformation characteristics of these alloys are sensitive to
annealing treatment and composition. The temperature range of transformation is broadened during cold working and
after subsequent annealing, the intermediate phase was appeared. The peaks become sharper and close together on
each cooling and heating cycle with increasing annealing temperature and time
J. Saaedi, H. Arabi, Sh. Mirdamadi, Th. W. Coyle,
Volume 5, Issue 4 (12-2008)
Abstract
Abstract: Two different coating microstructures of Ni-50Cr alloy were obtained on a stainless steel substrate by
changing combustion characteristics of a high velocity oxy-fuel (HVOF) process and the size distribution of feed
powder during coating process. Use of the finer feed powder and leaner fuel in oxygen/fuel ratio (i.e. using a ratio
much less than stoichiometric ratio) led to formation of an extremely dense coating with high oxide content. Heat
treating of this coating at 650ºC for 4 hours caused the formation of an intermetallic sigma phase having Cr7Ni3
stoichiometry. Formation of this phase has been reported occasionally in thin films not in thermal spray coatings, as
reported for the first time in this research. In addition no sigma phase was detected in the HVOF as-deposited coating
with low oxide content after heat treatment of the samples. Therefore, due to the limited number of papers available in
the subject of formation of phase in either Ni-Cr bulk alloys or coatings, it is considered appropriate to show up a
case in this field. In this work, the formation of sigma phase in Ni-50Cr coating deposited by HVOF technique and
heat treated at 650ºC was discussed and then the coating was characterized.
A.nouri, Sh.kheirandish, H. Saghafian,
Volume 5, Issue 4 (12-2008)
Abstract
Abstract: In the current work, the strain hardening behavior of dual-phase steels with different silicon content (0.34-
2.26 Wt. %) was examined using the modified Crussard-Jaoul analysis. It was shown that these dual-phase steels
deform in two stages over a uniform strain range. Each stage exhibited a different strain hardening exponent varying
with silicon content. At the first stage, work hardening exponent remind significantly constant, while during the second
stage, it decreased with increasing silicon content from 0.34% to 1.51% and then increased for the higher silicon
contents (1.51% to 2.26%). It was found that the strain hardening behavior of these steels was predominantly affected
by the volume fraction of martensite at low silicon contet and the ferrite strengthening induced by silicon at the higher
silicon content. The effect of silicon content on the volume fraction of martensite and tensile properties were also
considered.
M. Mossanef, M. Soltanieh,
Volume 5, Issue 4 (12-2008)
Abstract
Abstract: The possibility of vanadium carbide coating formation on AISI L2 steel was studied in molten salt bath containing 33 wt% NaCl- 67 wt% CaCl2. In this research, the effects of time, temperature and bath composition on growing layer thickness were studied. The vanadium carbide coating treatment was performed in the NaCl-CaCl2 bath at 1173, 1273 and 1373 K temperatures for 3, 6, 9 hours and in bath containing 5, 10, 15, 25 wt% ferrovanadium. The presence of VC formed on the surface of the steel substrate was confirmed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis. The layer thickness of vanadium carbide and surface hardness ranged between 4.8 to 25.7 µm and 2645 to 3600 HV, respectively. The kinetics of layer growth was analyzed by measuring the depth of vanadium carbide layer as a function of time and temperature. The mean activation energy for the process is estimated to be 133 kJ/ mol.
