Metallic Materials Research Center

Tehrān, Iran

Metallic Materials Research Center

Tehrān, Iran

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Seifollahi M.,Iran University of Science and Technology | Kheirandish S.,Iran University of Science and Technology | Razavi S.H.,Iran University of Science and Technology | Abbasi S.M.,Metallic Materials Research Center | Sahrapour P.,Sharif University of Technology
ISIJ International | Year: 2013

In this paper, the shear deformation behavior of A286 Iron-based superalloy was studied with an emphasis on the influence of η phase on shear strength. The η (Ni3Ti phase precipitates at high temperature heat treatment or during services at the expense of gamma prime phase. According to the microstructural features, no evidences of η phase were found at 650 and 720°C. η phase precipitated at 780 and 840°C and the amount of it increased with an increase the time and temperature. Because of using the alloy as fasteners, investigation of shear properties and the influence of η phase on it are indispensable. The shear strength of the alloy with different volume fractions of η was examined. It was found that, with an increase of η volume fraction, the ultimate shear strength decreases. The shear punch fracture surfaces were also examined by the scanning electron microscopy. The fracture surfaces of sheared samples indicated that low and high volume fraction of η phase result in interior cracks and grain boundary decohesion, respectively. In fact, the fracture of weak grain boundary films (η phase produces this kind of decohesive cracking. © 2013 ISIJ.


Jafarzadeh K.,Metallic Materials Research Center | Valefi Z.,Metallic Materials Research Center | Ghavidel B.,Metallic Materials Research Center
Surface and Coatings Technology | Year: 2010

This paper reports a study of how the choice of plasma spray parameters, used during deposition of Al2O3-13%TiO2 coatings on carbon steel, influences the cavitation erosion properties of such coatings. The parameters studied are the power feeding rate and hydrogen flow rate. The surface and cross section of coatings before and after cavitation were also observed by scanning electron microscopy (SEM). The phases present in the coatings were characterized by X-ray diffraction method (XRD). The microscopic observations were used to study the inter-lamellar connection, porosity, unmelted particles and so on inside the coating. We also measured the roughness, microhardness, adhesion strength and cavitation erosion of the coatings. The XRD results showed that the coating includes different allotropes of Al2O3 such as α and γ. The cavitation erosion studies of the coatings were conducted by ultrasonic cavitation testing on the basis of ASTM G32 standard. It was found that cavitation erosion is accelerated around the unmelted particles and porosities. The results reveal that the cavitation resistance of the coating is determined by its microstructure and that increasing discontinuities (inside the coating) reduce its cavitation resistance. We have found that the coating obtained at hydrogen gas flow rate of 16L/min and powder feeding rate of 20g/min has the best cavitation resistance. © 2010 Elsevier B.V.


Tamasgavabari R.,Metallic Materials Research Center | Jafarzadeh K.,Metallic Materials Research Center | Madanipoor M.,Iranian Mineral Processing Research Center | Badri H.,Metallic Materials Research Center
Corrosion Engineering Science and Technology | Year: 2014

In this paper, the effect of surface oxidation on corrosion behaviour of Co-20?8Ni-6Al-10Cu-11Fe alloy in molten cryolite is investigated. The samples were produced by casting and then were oxidised at 1000°C for 10, 30 and 70 h respectively. The oxide layers were studied by scanning electron microscope (SEM) and X-ray diffraction (XRD). To determine the corrosion behaviour of the oxidised samples, they were exposed to molten cryolite at 930°C for 20 h. After corrosion, the samples were studied by SEM. The results showed that all the samples corroded, but the sample oxidised for 70 h, was more stable than the other and the other one that oxidised for 10 h, corroded severely.


Ghavam M.H.,Metallic Materials Research Center | Morakabati M.,Metallic Materials Research Center | Abbasi S.M.,Metallic Materials Research Center | Badri H.,Metallic Materials Research Center
International Journal of Materials Research | Year: 2014

The hot ductility of rolled IMI834 titanium alloy has been studied by conducting tensile tests with a strain rate of 0.1 s-1 and temperature range of 750 - 1 100 8C to obtain the optimum hot working conditions. The alloy showed minimum hot ductility in the lower alpha-beta region in the temperature range 750 - 950 8C. Further microstructural characterizations showed improvement in hot ductility by increasing temperature, which was attributed to reduction of volume fraction of high strength alpha phase. The best hot ductility was observed at 1 000 8C, i. e. in the upper alpha- beta region. The better hot ductility at higher temperature could be related to the increase in the volume fraction of beta phase and the occurrence of dynamic restoration phenomena. The second decline in hot ductility appeared at higher temperatures in the beta region and was attributed to the high stacking fault energy and self-diffusion of beta phase leading to limitation of dynamic recrystallization. © Carl Hanser Verlag GmbH & Co. KG.


Mohammadi Shore F.,Metallic Materials Research Center | Morakabati M.,Metallic Materials Research Center | Abbasi S.M.,Metallic Materials Research Center | Momeni A.,Hamedan University of Technology | Mahdavi R.,Metallic Materials Research Center
ISIJ International | Year: 2014

0.001 s-1-1 s-1 to study the hot ductility of Incoloy 901. Hot ductility of the material was optimized in range of 950°C-1 050°C and descended at either higher or lower temperatures. Dynamic recrystallization was the reason for the improvement of ductility at high temperatures. At lower temperatures, e.g. 850°C, dynamic precipitation of intermetallic phases could effectively inhibit dynamic recrystallization and resulted in poor hot ductility. At very high temperatures, e.g. 1 150°C, the hot ductility drop was due to the decohesion of particles/matrix interfaces. The insensitivity of material to flow localization was understood from the monotonic increase of the strain rate sensitivity over the studied temperature range. The peak strain of the material unexpectedly increased with increasing temperature up to 1 050°C and then decreased at higher temperatures. These results accounted for the possibility of dynamic precipitation of intermetallics at temperatures below 1 050°C and thereby delaying dynamic recrystallization. The hyperbolic sine constitutive equation was used to describe the dependence of tensile stress on deformation temperature and strain rate and the corresponding material constants were determined. The average apparent activation energy for the initiation of dynamic recrystallization was determined as 359 kJ mol-1. © 2014 ISIJ.


Momeni A.,Hamedan University of Technology | Abbasi S.M.,Metallic Materials Research Center
Journal of Alloys and Compounds | Year: 2015

The influence of chemical composition on the hot deformation behavior and dynamic recrystallization was studied by conducting hot compression tests on two low alloy steels, AISI 4135 and VCN200, over a temperatures range of 1000-1150 °C and at strain rates of 0.001 s-1 to 1 s-1. The activation energy of dynamic recrystallization in 4135 and VCN200 was determined as 374 kJ/mol and 435.3 kJ/mol, respectively. The different apparent activation energies (about 17%) were attributed to about 30% difference between the carbon equivalents of the steels. The results confirmed that the higher the alloying elements, the higher the peak stress and strain of DRX flow curves. The results were associated with the dragging force of solute atoms on the grain boundaries. A new formula was proposed as a chemical factor to quantify the influence of solute dragging on the dynamic recrystallization behavior. Simple power equations described how the peak stress and strain depends on the Zener-Hollomon parameter. The material constants of the developed equations were related to the proposed composition factor. Unlike to dynamic recrystallization, dynamic recovery did not delayed by solute dragging. © 2014 Elsevier B.V. All rights reserved.


Godarzi R.M.,Metallic Materials Research Center | Morakabati M.,Metallic Materials Research Center | Abbasi S.M.,Metallic Materials Research Center | Badri H.,Metallic Materials Research Center
International Journal of Materials Research | Year: 2015

In the present work, the effects of cold work and aging parameters on the microstructure and precipitation kinetics of Ni-Span-C 902 superalloy were studied. The solution treated alloy was cold-rolled to different deformations from 30 to 60% followed by aging in the temperature range of 450-850°C for different times, from 102 to 105 seconds. The results showed that the 50% cold-rolled alloy attained its maximum hardness by aging at 650°C for 105 seconds. This was concurrent with the fine distributed gamma' precipitates that appeared in the microstructure. By increasing temperature from 750 to 850 °C, overaging occurred due to the increase in gamma' particle size and the formation of epsilon-phase. The estimated activation energy of the preci-pitation reaction, based on Johnson-Mehl-Avrami-Kolmo- gorov analysis, was determined to be 254 kJ • mo-1 for the 50% cold-rolled alloy.


Yazdani M.,Sharif University of Technology | Abbasi S.M.,Metallic Materials Research Center | Taheri A.K.,Sharif University of Technology | Momeni A.,Hamedan University of Technology
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2013

Hot compression tests were carried out on a Fe-29Ni-17Co alloy in the temperature range of 900 °C to 1200 °C and at strain rates of 0.001-1 s-1. Dynamic recrystallization was found responsible for flow softening during hot compression. The flow behavior was successfully analyzed by the hyperbolic sine equation and the corresponding material constants A, n and α were determined. The value of apparent activation energy was determined as 423 kJ/mol. The peak and steady state strains showed simple power-law dependence on the Zener-Hollomon parameter. The dynamic recrystallization kinetics was analyzed using Avrami equation and the corresponding exponent was determined to be about 2.7. This value, higher than 2 reported in the literatures, is associated with the mechanism of continuous dynamic recrystallization in the studied alloy. The flow curve up to the peak was modeled by the Cingara equation and the strain exponent, c, was determined about 0.85. The higher value of c compared with the value of 0.2 which has been reported for some stainless steels fortified the idea of extended dynamic recovery or continuous dynamic recrystallization in the studied alloy. © 2013 The Nonferrous Metals Society of China.


Seifollahi M.,Iran University of Science and Technology | Razavi S.H.,Iran University of Science and Technology | Kheirandish S.,Iran University of Science and Technology | Abbasi S.M.,Metallic Materials Research Center
Journal of Materials Engineering and Performance | Year: 2013

In this research, the mechanism of eta (η-Ni3Ti) phase precipitation in iron-nickel-based A286 superalloy was assessed during aging heat treatment in the temperature range between 650 and 900 C for the times of 1-30 h. Optical microscopy, scanning electron microscopy, differential thermal analysis, and x-ray diffractometry were used to describe the η phase transformation. The results showed that the major precipitates at temperatures below 840 C were γ′ and η. The η phase started to precipitate at the expense of the γ′ phase after prolonged aging. The η phase existed in the samples aged at temperature higher than 760 C with cellular morphology. The η volume fraction increased with increasing heat treatment time. In addition, when the aging temperature was increased from 760 to 820 C, the η volume fraction increased and then decreased after 840 C. The η phase morphology also changed from cellular to Widmanstätten- type during aging. The time-temperature-precipitation diagrams of these morphologies are presented. The results indicated the differences in precipitation mechanisms of η phase at 840 and 860 C. © 2013 ASM International.


Tamasgavabari R.,Metallic Materials Research Center | Jafarzadeh K.,Metallic Materials Research Center | Madanipoor M.,Iranian Mineral Processing Research Center | Badri H.,Metallic Materials Research Center
Anti-Corrosion Methods and Materials | Year: 2015

Purpose – The purpose of this paper was the investigation of corrosion behaviour of Ni-6Al-10Cu-11Fe-15Cr alloy, as a candidate material for inert anodes in aluminium electrolysis industries. Design/methodology/approach – The samples were prepared by casting, and then were oxidized at 1,000°C for 30, 70 and 100 hours, respectively. To determine corrosion resistant of the samples, they were exposed to molten cryolite at 930°C for 70 hours. Then the surface layers were studied. Findings – Results showed that by extension of corrosion time, thickness of oxide layers increases. In addition, it was found that Al2O3 and Cr2O3 are the major oxide compounds that appear on the surface of the sample. Originality/value – In this paper, the Ni-6Al-10Cu-11Fe-15Cr nickel base alloy has been selected to study its corrosion behaviour in molten cryolite as a candidate for inert anodes. It was found out that by addition Al and Cr into the alloy composition, due to formation of Al2O3 and Cr2O3 following oxidation, the substrate was protected from corrosion attacks. © Emerald Group Publishing Limited.

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