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    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 texture development during friction stir processing of Al–Mg alloy sheets with TiO2 nanoparticles [electronic resource]

    , Article Materials Science and Engineering: A ; 27 May 2014, Volume 605, Pages 108–118 Khodabakhshi, F ; Simchi, A. (Abdolreza) ; Kokabi, A. H ; Nosko, M ; Simancik, F ; Svec, P ; Sharif University of Technology
    Aluminum matrix nanocomposites were fabricated by friction stir processing of Al–Mg alloy sheets with pre-placed TiO2 nanoparticles at a concentration of 2 to 6 vol%. Microstructural studies showed that solid state reactions between the metal matrix and TiO2 particles caused in situ formation of MgO and Al3Ti nanophases with an average size ~50 nm. These nanophases were homogenously distributed in an ultra-fine grain structure (0.2–2 µm) of the base metal. The results of pole figures evaluation obtained by electron back scattered diffraction studies revealed that the random orientation of initial annealed sheet was changed to components near to shear and silver texture in the friction stir... 

    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... 

    Reactive friction stir processing of AA 5052-TiO2 nanocomposite: process-microstructure-mechanical characteristics [electronic resource]

    , Article Journal of Materials Science and Technology ; 2014, Vol.0, Issue 0 Khodabakhshi, F ; Simchi, A. (Abdolreza) ; Kokabi, A. H ; Sadeghahmadi, M ; Gerlich, A. P ; Sharif University of Technology
    Friction stir processing (FSP) is a solid state route with a capacity of preparing fine grained nanocomposites from metal sheets. In this work, we employed this process to finely distribute TiO2 nanoparticles throughout an Al–Mg alloy, aiming to enhance mechanical properties. Titanium dioxide particles (30 nm) were preplaced into grooves machined in the middle of the aluminium alloy sheet and multipass FSP was afforded. This process refined the grain structure of the aluminium alloy, distributed the hard nanoparticles in the matrix and promoted solid state chemical reactions at the interfaces of the metal/ceramic particles. Detailed optical and electron microscopic studies showed that the... 

    Non-isothermal kinetic studies of crystallization in amorphous Al86Ni10MM4 alloy [electronic resource]

    , Article Journal of Non-Crystalline Solids ; 1 March 2014, Volume 387, Pages 36–40 Mansouri, M ; Simchi, A. (Abdolreza) ; Lee, J. I ; Park, E. S ; Varahram, N ; Sharif University of Technology
    Al86Ni10MM4 (MM: Mischmetal) amorphous ribbons were prepared by melt spinning on a child copper wheel. Non-isothermal crystallization kinetics of the amorphous alloy was studied by differential scanning calorimetry (DSC). The crystallized phases were determined by X-ray diffraction method and transmission electron microscopy. DSC traces were analyzed by Kissinger method to determine the apparent activation energy of crystallization. Changes in the activation energy (Eα) with progression of crystallization were also evaluated by differential iso-conversional method of Friedman. For the precipitation of nanometer-sized Al particles, the activation energy slightly increased with increasing the... 

    Mechanical- activated phase formation of NiTi in the presence of nanoparticles [electronic resource]

    , Article Journal of Nano ; October 2013, Volume 08, Issue 05 Farvizi, M ; Ebadzadeh, T ; Vaezi, M. R ; Simchi, A. (Abdolreza) ; Kim, H. S ; Sharif University of Technology
    Effect of Al2O3 nanoparticles (80 nm) on the grain structure and phase formation in Ni-50Ti system during high-energy mechanical alloying (MA) was studied. While the formation of NiTi B2 phase occurs progressively during MA, it is shown that the hard inclusions cause abrupt phase formation at short milling times, particularly at higher nano-Al2O3 contents. High-resolution transmission electron microscopy showed significant grain refinement in the presence of alumina nanoparticles to sizes less than 10 nm, which precedes the formation of semicrystalline structure and reduces the diffusion length and thus accelerates the phase formation. The composite powder reached steady-state MA condition... 

    Microstructural features, texture and strengthening mechanisms of nanostructured Al6063 alloy processed by powder metallurgy [electronic resource]

    , Article Journal of Materials Science and Engineering: A ; 15 May 2011, Volume 528, Issue 12, Pages 3981–3989 Asgharzadeh, H ; Simchi, A. (Abdolreza) ; Kim, H. S ; Sharif University of Technology
    Nanostructured AA6063 (NS-Al) powder with an average grain size of ∼100 nm was synthesized by high-energy attrition milling of gas-atomized AA6063 powder followed by hot extrusion. The microstructural features of the consolidated specimen were studied by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) techniques and compared with those of coarse-grained AA6063 (CG-Al) produced by hot powder extrusion of gas-atomized powder (without using mechanical milling). The consolidated NS-Al alloy consisted of elongated ultrafine grains (aspect ratio of ∼2.9) and equiaxed nanostructured grains. A high fraction (∼78%) of high-angle grain boundaries with average... 

    Synthesis of a nanostructured MgH2–Ti alloy composite for hydrogen storage via combined vacuum arc remelting and mechanical alloying [electronic resource]

    , Article Journal of Materials Letters ; 15 April 2011, Volume 65, Issue 7, Pages 1120–1122 Mahmoudi, N ; Kaflou, A ; Simchi, A. (Abdolreza) ; Sharif University of Technology
    To improve the hydrogen kinetics of magnesium hydride, TiCr1.2Fe0.6 alloy was prepared by vacuum arc remelting (VAR) and the alloy was co-milled with MgH2 to process nanostructured MgH2–5 at.% TiCr1.2Fe0.6 powder. The hydrogen desorption properties of the composite powder were studied and compared with pure magnesium hydride. X-ray diffraction (XRD) analysis showed that the composite powder prepared by VAR/mechanical alloying (MA) procedure consisted of β-MgH2, γ-MgH2, bcc Ti–Cr–Fe alloy, and small amount of MgO. The average size of particles and their grain structure after 4 h MA were determined by a laser particle size analyzer and XRD method and found to be 194 nm and 11 nm, respectively.... 

    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... 

    Hot workability of ultrafine-grained aluminum alloy produced by severe plastic deformation of Al6063 powder and consolidation [electronic resource]

    , Article Materials Science Forum ; Volume 667-669, 2011, Pages 979-984 Asgharzadeh, H. (Hamed) ; Simchi, A. (Abdolreza) ; Seop Kim, Hyoung ; Sharif University of Technology
    Al6063 powder was subjected to severe plastic deformation via high-energy mechanical milling to prepare ultrafine-grained (UFG) aluminium alloy. Uniaxial compression test at various temperatures between 300 and 450 °C and strain rates between 0.01 and 1 s-1 was carried out to evaluate hot workability of the material. Microstructural studies were performed by EBSD and TEM. The average activation energy and strain rate sensitivity of the hot deformation process were determined to be 280 kJ mol-1 and 0.05, respectively. The deformation temperature and applied strain rate significantly affected the grain structure of UFG Al alloy. A finer grain structure was obtained at lower temperatures and... 

    Cryogenic friction-stir processing of ultrafine-grained Al-Mg-TiO2 nanocomposites

    , Article Materials Science and Engineering A ; Vol. 620, issue , 2014 , pp. 471-482 ; ISSN: 09215093 Khodabakhshi, F ; Gerlich, A. P ; Simchi, A ; Kokabi, A. H ; Sharif University of Technology
    Submerged friction-stir processing under cryogenic conditions was employed to fabricate ultrafine-grained nanocomposites with enhanced mechanical characteristics. Al-Mg alloy sheet with 3vol% TiO2 nanoparticles were processed under air (ambient temperature), a water-dry ice medium (~-25°C), and liquid nitrogen. It is shown that a homogenous distribution of reinforcement particles throughout the metal matrix is attained at a rotational speed of 1400rpm and a traverse velocity of 50mm/min after 4 passes. In situ formation of Al3Ti and MgO nanophases during multi-pass processing is shown by transmission electron microscopy. Under the cryogenic cooling condition, ultrafine grains and cellular... 

    Microstructrual evolution of aluminum 6061 alloy through tube channel pressing

    , Article Materials Science and Engineering A ; Vol. 615 , 2014 , pp. 139-147 ; ISSN: 09215093 Farshidi, M. H ; Kazeminezhad, M ; Miyamoto, H ; Sharif University of Technology
    The evolution of microstructure and the mechanical properties of an aluminum 6061 alloy tube subjected to a novel severe plastic deformation process called tube channel pressing were studied. Results show that the tube channel pressing causes an impressive grain refinement and strengthening of the material. As an illustration, mostly ultrafine grained tube (D-=760nm) bearing the yield strength of 352. MPa can be obtained after 5 passes of tube channel pressing. Additionally, the tube channel pressing causes the heterogeneous grain refinement resulting in a bimodal distribution of size of grains after 7th pass. Therefore, it can be inferred that the main microstructure refining mechanism... 

    Fabrication localized surface plasmon resonance sensor chip of gold nanoparticles and detection lipase-osmolytes interaction

    , Article Applied Surface Science ; Vol. 314, issue , 2014 , Pages 138-144 ; ISSN: 01694332 Ghodselahi, T ; Hoornam, S ; Vesaghi, M. A ; Ranjbar, B ; Azizi, A ; Mobasheri, H ; Sharif University of Technology
    Co-deposition of RF-sputtering and RF-PECVD from acetylene gas and Au target were used to prepare sensor chip of gold nanoparticles (Au NPs). Deposition conditions were optimized to reach a Localized Surface Plasmon Resonance (LSPR) sensor chip of Au NPs with particle size less than 10 nm. The RF power was set at 180 W and the initial gas pressure was set at 0.035 mbar. Transmission Electron Microscopy (TEM) images and Atomic Force Microscopy (AFM) data were used to investigate particles size and surface morphology of LSPR sensor chip. The Au and C content of the LSPR sensor chip of Au NPs was obtained from X-ray photoelectron spectroscopy (XPS). The hydrogenated amorphous carbon (a-C:H)... 

    Microstructure, mechanical properties, corrosion behavior and cytotoxicity of Mg-Zn-Al-Ca alloys as biodegradable materials

    , Article Journal of Alloys and Compounds ; Vol. 607 , 2014 , Pages 1-10 ; ISSN: 09258388 Homayun, B ; Afshar, A ; Sharif University of Technology
    Recently, considerable attentions have been paid to alloy Mg-4Zn-0.2Ca for biomedical applications due to its suitable biocompatibility and acceptable mechanical properties. In this work, the effects of the addition of different amounts of Al on microstructure, mechanical properties, degradation behavior, and biocompatibility of this alloy were investigated. The corrosion behaviors of the alloys were investigated through polarization tests, chronoamperometry analysis, immersion tests, and EIS experiments. The mechanical properties were analyzed by using tensile tests and compression tests. The results showed that the addition of Al up to 3 wt.% considerably modifies the degradation behaviors... 

    Microstructure evolution and microhardness of friction stir welded cast aluminum bronze

    , Article Journal of Materials Processing Technology ; Vol. 214, issue. 8 , August , 2014 , pp. 1524-1529 ; ISSN: 09240136 Rizi, M. S ; Kokabi, A. H ; Sharif University of Technology
    Microstructural characteristics and mechanical properties of a friction stir welded cast aluminum bronze (Cu-9Al-1Fe), produced by a sand casting method, have been investigated at tool rotation of 850-1500 rpm and traverse speed of 50-100 mm/min. Refinement of the primary coarse cast microstructure in the base metal was seen after friction stir welding. Microstructure of the stir zone was characterized in four distinct areas of non-isometric fine grains while a significant grain growth was noticed in some of the areas. Conditions of grain growth are defined with high heat input intensity and low heat transfer capability. The grain size was observed to decrease after FSW, resulting in a... 

    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... 

    Effect of bonding parameters on microstructure development during TGTLP bonding of Al7075 alloy

    , Article Philosophical Magazine ; Vol. 94, issue. 11 , Mar , 2014 , pp. 1166-1176 ; ISSN: 14786435 Afghahi, S. S. S ; Ekrami, A ; Farahany, S ; Jahangiri, A ; Sharif University of Technology
    The effect of temperature, pressure and bonding time on microstructure of temperature gradient transient liquid phase (TGTLP) diffusion bonded Al7075 alloy using liquid gallium interlayer was investigated. The selected bonding method relies on using the minimum amount of liquid gallium on faying surfaces, using a very fast heating rate to reach the joining temperature and imposing a temperature gradient across the bond region. The microstructure of the diffusion bonded joints was evaluated by light optical microscopy, scanning electron microscopy and energy dispersive spectroscopy (EDS). Results show that by increasing the temperature, pressure and time of joining, a more uniform... 

    Thermo-mechanical stress analysis of thermal barrier coating system considering thickness and roughness effects

    , Article Surface and Coatings Technology ; Vol. 243 , 2014 , pp. 91-99 ; ISSN: 02578972 Moridi, A ; Azadi, M ; Farrahi, G. H ; Sharif University of Technology
    Cast aluminium-silicon alloy, A356.0, is widely used in automotive and aerospace industries because of its outstanding mechanical, physical, and casting properties. Thermal barrier coatings can be applied to combustion chamber to reduce fuel consumption and pollutions and also improve fatigue life of components. The purpose of the present work is to simulate stress distribution of A356.0 under thermo-mechanical cyclic loadings, using a two-layer elastic-visco-plastic model of ABAQUS. The results of stress-strain hysteresis loop are validated by an out of phase thermo-mechanical fatigue test. Different thicknesses from 300 to 800. μm of top coat and also roughness of the interfaces are... 

    Thermo-mechanical behaviours of light alloys in comparison to high temperature isothermal behaviours

    , Article Materials at High Temperatures ; Vol. 31, issue. 1 , 2014 , pp. 12-17 ; ISSN: 09603409 Azadi, M ; Farrahi, G. H ; Winter, G ; Eichlseder, W ; Sharif University of Technology
    In this article, out-of-phase thermo-mechanical fatigue (TMF) behaviours of light alloys were investigated in comparison to their high temperature low cycle fatigue (LCF) behaviours. For this objective, strain based fatigue tests were performed on the A356 aluminium alloy and on the AZ91 magnesium alloy. Besides, TMF tests were carried out, where both strain and temperature changed. The fatigue lifetime comparison demonstrated that the TMF lifetime was less than that one under LCF loadings at elevated temperatures for both light alloys. The reason was due to severe conditions in TMF tests in comparison to LCF tests. The temperature varied in TMF test but it was constant under LCF loadings....