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    Directional solidification of Ni base superalloy IN738LC to improve creep properties

    , Article Materials Science and Technology ; Volume 16, Issue 5 , 2000 , Pages 579-586 ; 02670836 (ISSN) Kermanpur, A ; Varahraam, N ; Engilehei, E ; Mohammadzadeh, M ; Davami, P ; Sharif University of Technology
    IOM Communications Ltd  2000
    The high Cr, Ni base superalloy IN738LC has been directionally solidified on both laboratory and industrial scales using Bridgman and liquid metal cooling (LMC) methods respectively. In the Bridgman experiments, cylindrical rods were grown using a graphite chill with temperature gradient G = 5·0 K mm-1 and a water cooled copper chill with G = 8·5 K mm-1, and a wide range of withdrawal rates of R = 60, 120, 240, 600, and 1200 mm h-1. In the LMC rigs, several turbine blades were grown using a wide range of withdrawal rates of R = 120, 225, 330, 420, and 630 mm h-1. Grain and dendritic structures in both cylindrical and turbine blade specimens were evaluated in longitudinal and transverse... 

    Corrosion and time dependent passivation of Al 5052 in the presence of H2O2

    , Article Metals and Materials International ; Volume 22, Issue 4 , 2016 , Pages 609-620 ; 15989623 (ISSN) Batmanghelich, F ; Bagheri Hariri, M ; Sharifi Asl, S ; Yaghoubinezhad, Y ; Mortazavi, G ; Seo, Y ; Sharif University of Technology
    Korean Institute of Metals and Materials  2016
    Corrosion and time–dependent oxide film growth on AA5052 Aluminum alloy in 0.25M Na2SO4 solution containing H2O2 was studied using electrochemical impedance spectroscopy, potentiodynamic polarization, chronoamperometric and open circuit potential monitoring. It was found that sequential addition of H2O2 provokes passivation of AA5052 which ultimately thickens the oxide film and brings slower corrosion rates for AA5052. H2O2 facilitates kinetics of oxide film growth on AA 5052 at 25° and 60 °C which is indicative of formation of a thick barrier film that leads to an increment in the charge transfer resistance. Pitting incubation time increases by introduction of H2O2 accompanied by lower... 

    An investigation on the effect of carbon and silicon on flow behavior of steel

    , Article Materials and Design ; Volume 23, Issue 3 , 2002 , Pages 271-276 ; 02641275 (ISSN) Serajzadeh, S ; Karimi Taheri, A ; Sharif University of Technology
    Elsevier Ltd  2002
    The effect of carbon and silicon on the occurence of dynamic recrystallization as well as on the flow stress of steel was investigated. For this purpose, three grades of steels including low carbon, medium carbon and high silicon low carbon steel were examined. Single hit experiments at temperatures of 900-1200 °C and strain rate of 0.01-2 s-1 were performed to determine the phase transformation kinetics. Different socking times were utilized to detect the effect of initial austenite grain size on the kinetics of dynamic recrystallization and flow behavior of the steels. It was found that increasing the carbon content leads to a higher rate of dynamic recrystallization at high temperatures... 

    Properties of Fe-Ni-Cr alloy coatings by using direct and pulse current electrodeposition

    , Article Journal of Alloys and Compounds ; Volume 476, Issue 1-2 , 2009 , Pages 234-237 ; 09258388 (ISSN) Adelkhani, H ; Arshadi, M. R ; Sharif University of Technology
    This paper describes the effects of using direct and pulse current on composition and corrosion resistance of Fe-Ni-Cr alloy coatings. In both direct and pulse current electrodeposition, increasing the current density has a decreasing effect on Fe and Ni and an increasing influence on Cr. In pulse current electrodeposition, duty cycle has a greater effect than frequency on composition of the alloy coating, particularly in the range of 10-50%. In this range, by increasing the duty cycle, Ni decreases, Fe sharply increase and Cr shows an increasing trend. Following a study of the microhardness of coatings, it is determined that the microhardness increases about 1.5 times by pulse current... 

    Wire-Based friction stir processing as a novel pathway for solid-state surface alloying of magnesium

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 52, Issue 11 , 2021 , Pages 4737-4741 ; 10735623 (ISSN) Zahiri Sabzevar, M ; Mousavizade, S. M ; Pouranvari, M ; Sharif University of Technology
    Springer  2021
    Wire-based friction stir processing is introduced as a solid-state surface alloying strategy for surface alloying of AZ31 magnesium alloy with aluminum, as a key alloying element in magnesium alloys. This technique enables the formation of a defect-free, grain refined and alloyed surface with the increased volume fraction of Mg-Al second phase, and thus, enhanced surface hardness. This simple technique provides a solid-state surface alloying pathway to improve the surface properties of the metallic materials. © 2021, The Minerals, Metals & Materials Society and ASM International  

    Single and double stage sintering of mechanically alloyed powder for nanostructured Ti6Al4V foams usable in cancellous scaffolds

    , Article International Heat Treatment and Surface Engineering ; Volume 7, Issue 1 , 2013 , Pages 43-48 ; 17495148 (ISSN) Sadrnezhaad, S. K ; Aryana, M ; Hassanzadeh Nemati, N ; Alizadeh, M ; Ebadifar, A ; Sharif University of Technology
    Mechanical alloying and sintering were used to fabricate nanostructured Ti6Al4V scaffolds of highly controllable pore geometry and fully interconnected porous network. Elemental powders were milled for different periods of time (10, 20, 30, 40 and 60 h), mixed with 40-60 vol.-% of 200-400 μm cuboidal NaCl, compacted at 500-600 MPa and sintered according to single or double stage heat treatment regimes at 790 and 950°C under vacuum. After sintering, the samples were soaked in distilled water to washout the NaCl. Foamy microstructures were obtained showing well shaped biopores and fragmentary embedded micropores. The shape of initial NaCl was copied into the biopores which had highly... 

    An Energetics Study of Formation of Some Organic Compounds in Fischer-Tropsch Synthesis by the Method of Unity Bond Index-Quadratic Exponential Potential (UBI-QEP)

    , M.Sc. Thesis Sharif University of Technology Javadi, Nabi (Author) ; Gobal, Fereydoon (Supervisor)
    The purpose of this project is the prediction of the activation barriers and enthalpy for elementary steps in the process of Fischer-Tropsch over the surfaces of Fe, Cu and Fe/Cu alloys catalyst by using of UBI-QEP method aiming at finding prediction of the activity and selectivity on the basis of energy criteria.
    UBI-QEP methods is based on conservation of bond index of adsorbed molecules and follow the quadratic exponential potential for energy, calculate the enthalpy and activation barriers of reaction pathways in a heterogeneous catalytic process and select the most desirable path to take.
    The elementary steps such as dissociation of CO, hydrogenation of carbidic carbon, C-C... 

    Development of fcc-Al nanoparticles during crystallization of amorphous Al–Ni alloys containing mischmetal: Microstructure and hardness evaluation [electronic resource]

    , Article Materials Science and Engineering A ; Volume 604, 16 May 2014, Pages 92-97 Mansouri, M. (Mehdi) ; Simchi, A ; Varahram, N ; Park, E. S ; Sharif University of Technology
    In the present work, fcc-Al nanoparticle development in Al90−xNi10MMx (MM: Ce mischmetal; x=2, 4) amorphous alloys was studied via non-isothermal differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, and nanoindentation test. Results showed that the crystallization of Al88Ni10MM2 alloy occurred by the precipitation of fcc-Al nanoparticles followed by the crystallization of Al11MM3 and Al3Ni phases. Transmission electron microscopy revealed that the aluminum precipitates had an average size of ~12 nm with a round morphology. Increasing the mischmetal content to 4 at% (Al86Ni10MM4 alloy) caused a three-stage crystallization process with a change in the size... 

    A comprehensive study on the microstructure of high strength low alloy pipeline welds

    , Article Journal of Alloys and Compounds ; Vol. 597 , June , 2014 , pp. 142-147 ; ISSN: 09258388 Beidokhti, B ; Kokabi, A. H ; Dolati, A ; Sharif University of Technology
    The microstructural characteristic of HSLA welds containing different amounts of titanium were evaluated carefully. It was observed that the microstructure of welds consisted of ferrite with mixed morphologies, and small amounts of pearlite and martensite-austenite micro-constituents. Because of insufficient time for diffusion of carbon, formation of pearlite lamellae could not be completed in the weld region. Martensite was formed from carbon enrichment of austenite during nucleation and growth of acicular ferrite and bainitic ferrite. While coarse manganese sulfide particles had weak interface strength with matrix and formed some micro-fissures; increasing titanium amount of welds... 

    Thermokinetic study of Fischer-Tropsch synthesis on Fe2Cu 1 and FeCu surfaces with comparison to Fe(110) and Cu(111) catalysts by the UBI-QEP method

    , Article Journal of the Iranian Chemical Society ; Vol. 11, issue. 5 , 2014 , pp. 1305-1310 ; SSN: 1735-207X Javadi, N ; Sajjadifar, S ; Sharif University of Technology
    The purpose of this study is to predict the activation barriers and enthalpy for elementary steps in the process of Fischer-Tropsch (F-T) on the surfaces of Fe(110), Cu(111) and Fe/Cu alloys catalyst using "Unity Bond Index-Quadratic Exponential Potential" method aimed at predicting the activity and selectivity on the basis of energy criteria. The elementary steps, such as dissociation of CO, hydrogenation of carbidic carbon, C-C chain growth by insertion of CH2 versus CO into the metal-alkyl bonds, and chain termination, which lead to hydrocarbons (alkanes versus α-olefins) or oxygenates are discussed in detail. The results show that metallic Fe(110) is necessary to produce the carbidic... 

    Electrochemical behavior of nanostructured fe-pd alloy during electrodeposition on different substrates

    , Article Journal of Electrochemical Science and Technology ; Volume 9, Issue 3 , 2018 , Pages 202-211 ; 20938551 (ISSN) Rezaei, M ; Haghshenas, D. F ; Ghorbani, M ; Dolati, A ; Sharif University of Technology
    Korean Electrochemical Society  2018
    In this work, Fe-Pd alloy films have been electrodeposited on different substrates using an electrolyte containing [Pd(NH3)4]2+ (0.02 M) and [Fe-Citrate]2+ (0.2 M). The influences of substrate and overpotential on chemical composition, nucleation and growth kinetics as well as the electrodeposited films morphology have been investigated using energy dis-persive X-ray spectroscopy (EDS), current-time transients, scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) patterns. In all substrates – brass, copper and sputtered fluorine doped tin oxide on glass (FTO/glass) – Fe content of the electrodeposited alloys increases by increasing the overpotential.... 

    Evaluation of simultaneous effect of melt filtration and cooling rate on tensile properties of A356 cast alloy

    , Article Iranian Journal of Materials Science and Engineering ; Volume 16, Issue 3 , 2019 , Pages 44-51 ; 17350808 (ISSN) Khakzadshahandashti, A ; Davami, P ; Pirmohammadi, M ; Sharif University of Technology
    Iran University of Science and Technology  2019
    B The combined influence of both melt filtration and cooling rate on the microstructure and mechanical properties of A356 cast alloy was studied. A step casting model with five different thicknesses was used to obtain different cooling rates. The effect of melt filtration was studied by using 10 and 20 pores per inch (PPI) ceramic foam filters in the runner. Results showed that secondary dendrite arm spacing decreased from 80 μm to 34 μm with increasing cooling rate. Use of ceramic foam filters in the runner led to the reduction of melt velocity and surface turbulence, which prevented the incorporation of oxide films and air in the melt and consequently had an overall beneficial effect on... 

    Determination of tearing energy from uniaxial tension tests of aluminum alloy sheet

    , Article Journal of Materials Processing Technology ; Volume 147, Issue 2 , 2004 , Pages 185-190 ; 09240136 (ISSN) Mahmudi, R ; Mohammadi, R ; Sepehrband, P ; Sharif University of Technology
    Tearing energy of AA5010 aluminum alloy sheets has been studied by the single tensile testing (STT) and multiple tensile testing (MTT) methods. The total energy required to tear the specimens was assumed to be composed of two components; one associated with uniform plastic deformation, which occurs in the work-hardening range of the material, and the other with post-uniform deformation and tearing which leads to the failure of the specimens. In the STT method, tearing energy was calculated by subtracting the plastic deformation energy, dissipated in the uniform deformation range, from the total energy absorbed by a single specimen during tension. In the MTT method, which uses different... 

    Aging behavior and tensile properties of squeeze cast AL 6061/SIC metal matrix composites

    , Article Scientia Iranica ; Volume 11, Issue 4 , 2004 , Pages 392-397 ; 10263098 (ISSN) Ehsani, R ; Seyed Reihani, S. M ; Sharif University of Technology
    Sharif University of Technology  2004
    In this work, the production and properties of Al 6061/SiC composites, made using a squeeze casting method, were investigated. SiC preforms were manufactured by mixing SiC powder, having a 16 and 22 pm particle size, with colloidal silica as a binder. 6061 Al melt was squeeze cast into the pores of the SiC preform to manufacture a DRA composite containing 30v/o reinforcement. The aging behavior, tensile properties and fracture mechanism of the cast material were studied. The results show that higher hardness, yield strength, tensile strength and Young's modulus can be obtained by the addition of SiC particles to 6061 Al alloy, whereas tensile elongation decreases. This is mainly caused by a... 

    Surveying The Biodegradation Behavior, Biocompatibility and Mechanical Properties of Mg-4Zn-xAl-0.2Ca Alloys

    , M.Sc. Thesis Sharif University of Technology Homayun, Bahman (Author) ; Afshar, Abdollah (Supervisor)
    Due to their favorable biodegradability, Magnesium and its alloys have always attracted such a lot of research interests for making temporary implants. With the same direction, Mg-4Zn-0.2Ca has recently absorbed lots of research interests, due to its excellent biocompatibility. As the most regarded draw back concerned with this alloy, poor corrosion resistance is frequently discussed. Accordingly, in the present work it has been tried to come over this problem by addition different amount of aluminum, including 1, 3, 5, 7.5, and 10 percent, to this alloy; without causing any negative effect on its biocompatibility, and to present a new alloy composition with modified degradation behavior.... 

    Production of nanostructured Ni-Ti-Ag alloy by mechanical alloying [electronic resource]

    , Article Advanced Materials Research ; Volume 829, 2014, 67-72 Rostami, A. (Abbas) ; Sadrnezhaad, Khatiboleslam ; Bagheri, Gh. Ali ; Sharif University of Technology
    Because of corrosion resistance and antibacterial effects, shape memory Ni-Ti-Ag alloy can be considered for different biomedical applications. Mechanical alloying is used to produce nanostructured Ni-Ti-Ag alloy from elemental powders. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) are used to characterize the product. Results show that after 1h milling, homogenous distribution of the elements occurs; while no intermetallic compounds is observed. After 3h milling, titanium dissolves in nickel to form amorphous and nanostructured solid phases. Peaks of B2 phase appear in the XRD pattern after the 3h milling of the powder mixture. Sintering of the 3h-milled... 

    Hydrogen desorption properties of MgH 2–TiCr 1.2 Fe 0.6 nanocomposite prepared by high-energy mechanical alloying [electronic resource]

    , Article Journal of Power Sources ; 2011, Vol. 196, No.10, P.4604-4608 Mahmoudi, N. (Nafiseh) ; Kaflou, A ; Simchi, A. (Abdolreza) ; Sharif University of Technology
    In the present work, high-energy mechanical alloying (MA) was employed to synthesize a nanostructured magnesium-based composite for hydrogen storage. The preparation of the composite material with composition of MgH2–5at% (TiCr1.2Fe0.6) was performed by co-milling of commercial available MgH2 powder with the body-centered cubic (bcc) alloy either in the form of Ti–Cr–Fe powder mixture with the proper mass fraction (sample A) or prealloyed TiCr1.2Fe0.6 powder (sample B). The prealloyed powder with an average crystallite size of 14nm and particle size of 384nm was prepared by the mechanical alloying process. It is shown that the addition of the Ti-based bcc alloy to magnesium hydride yields a... 

    Microstructure and mechanical properties of oxide-dispersion strengthened Al6063 alloy with ultra-fine grain structure

    , Article Metallurgical & Materials Transactions. Part A ; Mar2011, Vol. 42 Issue 3, p. 816-824 Asgharzadeh, H ; Simchi, A. (Abdolreza) ; Kim, H. S ; Sharif University of Technology
    The microstructure and mechanical properties of the ultra-fine grained (UFG) Al6063 alloy reinforced with nanometric aluminum oxide nanoparticles (25 nm) were investigated and compared with the coarse-grained (CG) Al6063 alloy (~2 μm). The UFG materials were prepared by mechanical alloying (MA) under high-purity Ar and Ar-5 vol pct O2 atmospheres followed by hot powder extrusion (HPE). The CG alloy was produced by HPE of the gas-atomized Al6063 powder without applying MA. Electron backscatter diffraction under scanning electron microscopy together with transmission electron microscopy studies revealed that the microstructure of the milled powders after HPE consisted of ultra-fine grains... 

    Facile synthesis of monodisperse thermally immiscible Ag-Ni alloy nanoparticles at room temperature

    , Article Bulletin of Materials Science ; Vol. 37, issue. 6 , 2014 , pp. 1447-1452 Tabatabaei, S ; Sadrnezhaad, S. K ; Sharif University of Technology
    Ag and Ni are immiscible, mainly due to their large lattice mismatch. This paper reports on their nanoscale formation of solid solution at room temperature by simple reduction reactions which lead to the amorphous Ag-Ni alloy nanoparticles (ANPs) with mono-disperse distribution. Microscopic and spectroscopic studies confirmed dependence of the alloy composition on size of nanoparticles. In the presence of different ligands such as sodium citrate, polyvinyl alcohol and potassium carbonate a mixture of silver oxide and Ag-Ni ANPs was achieved. Stoichiometry of the Ag-Ni ANPs was also found to be strongly dependent on ligands of the reduction reaction and further study shows without any ligand... 

    Non-isothermal aging of a high-Zn-containing Al–Zn–Mg–Cu alloy: microstructure and mechanical properties

    , Article Materials Science and Technology (United Kingdom) ; 2017 , Pages 1-10 ; 02670836 (ISSN) Emami Kervee, S ; Pourshayan, P ; Nasrollahnezhad, F ; Khani Moghanaki, S ; Kazeminezhad, M ; Logé, R. E ; Nobakht, S ; Sharif University of Technology
    The non-isothermal aging behaviour of a newly developed Al–Zn–Mg–Cu alloy containing 17 wt-% Zn was investigated. Hardness and shear punch tests demonstrated that during non-isothermal aging, the mechanical properties of the alloy first increased and then decreased. The best properties were obtained in a sample which was non-isothermally aged upto 250°C with heating rate of 20°C min−1, due to the presence of η′/η (MgZn2) phases. This was confirmed by differential scanning calorimetery. After homogenisation, residual eutectic phases remained at triple junctions or in a spherical form. During aging, these phases transformed into rodlike S (Al2CuMg)-phase at 400°C, with sizes ranging from 50 to...