Loading...
Search for: precipitation
0.007 seconds
Total 326 records

    Improvement in Mechanical Properties of Microalloyed Steel 30MSV6 by a Precipitation Hardening Process

    , Article Journal of Iron and Steel Research International ; Volume 20, Issue 5 , 2013 , Pages 66-73 ; 1006706X (ISSN) Hajisafari, M ; Nategh, S ; Yoozbashizadeh, H ; Ekrami, A ; Sharif University of Technology
    2013
    Abstract
    The microstructural evolutions and mechanical properties of vanadium microalloyed steel (30MSV6) during precipitation hardening were studied. The effects of aging temperature and cooling rate on mechanical strength (yield strength and ultimate tensile strength) were similar. Increasing aging temperature or cooling rate firstly increased the mechanical strength of specimens up to their maximum values, which then decreased with further increase in aging temperature or cooling rate. Microstructural evolutions revealed that cooling rate had significant effects on the pearlite interlamellar spacing and size of pre-eutectoid ferrite. Unlike the effect of austenitizing temperature, the pearlite... 

    Avrami behavior of magnetite nanoparticles formation in co-precipitation process

    , Article Journal of Mining and Metallurgy, Section B: Metallurgy ; Volume 47, Issue 2 , 2011 , Pages 211-218 ; 14505339 (ISSN) Ahmadi, R ; Hosseini, H. M. R ; Masoudi, A ; Sharif University of Technology
    Abstract
    In this work, magnetite nanoparticles (mean particle size about 20 nm) were synthesized via coprecipitation method. In order to investigate the kinetics of nanoparticle formation, variation in the amount of reactants within the process was measured using pH-meter and atomic absorption spectroscopy (AAS) instruments. Results show that nanoparticle formation behavior can be described by Avrami equations. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were performed to study the chemical and morphological characterization of nanoparticles. Some simplifying assumptions were employed for estimating the nucleation and growth rate of magnetite nanoparticles  

    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
    Abstract
    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... 

    Spatial and temporal study of extreme precipitation over north of Iran

    , Article Global Nest Journal ; Volume 15, Issue 3 , 2013 , Pages 305-314 ; 17907632 (ISSN) Yousefi, Y ; Mohammadi, H ; Azizi, G. H ; Taghavi, F ; Masomnia, A ; Roradeh, H ; Masoompour, J ; Sharif University of Technology
    2013
    Abstract
    Two main focus of this study is the spatial and temporal analysis of annual 24-hour extreme precipitation amounts for different return periods, and the intra-annual variability of the frequency of month to month maximum rainfall using harmonic analysis. Data for analysis gathered from 51 stations that well-scattered at north of Iran (Caspian Sea's southern region). These data are analyzed using extreme values theory and harmonic analysis techniques. The results indicate that the Gen. Extreme Value (Jenkinson solution) is more appropriate than the linear Gumbel solution for the extreme value law. The maximum expected values of 200

    Experimental investigation and modeling of asphaltene precipitation due to Gas Injection

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 31, Issue 1 , 2012 , Pages 89-98 ; 10219986 (ISSN) Moradi, S ; Rashtchian, D ; Ganjeh Ghazvini, M ; Emadi, M. A ; Dabir, B ; Sharif University of Technology
    2012
    Abstract
    Asphaltene instability is one of the major problems in gas injection projects throughout the world. Numerous models have been developed to predict asphaltene precipitation; The scaling equation is an attractive tool because of its simplicity and not involving complex properties of asphaltene. In this work, a new scaling model is presented to account for asphaltene precipitation due to gas injection at reservoir conditions. Extensive published data from literature have been used in model preparation. To check predictive capability of the equation, miscible gas injection experiments are conducted for a southwest Iranian oil reservoir. Experimental results show that methane injection has... 

    Modeling of the mutual effect of dynamic precipitation and dislocation density in age hardenable aluminum alloys

    , Article Journal of Alloys and Compounds ; Volume 683 , 2016 , Pages 527-532 ; 09258388 (ISSN) Khani Moghanaki, S ; Kazeminezhad, M ; Sharif University of Technology
    Elsevier Ltd  2016
    Abstract
    A model has been proposed to capture the complex strain rate effect on dynamic precipitation of GP zones in an age-hardenable aluminum alloy. The contributions of vacancies and dislocations to dynamically formed GP zones have been specified in the model. It has been demonstrated that the proposed model is capable for predicting the contribution of each dynamic precipitation mechanisms, accurately, which are acting during deformation. Furthermore, the vacancy and dislocation evolutions during deformation have been considered in this modeling. The effect of strain rate by considering different mechanisms of dynamic precipitation of GP zones has been studied and confirmed by experimental data... 

    The effect of additives on the properties of HAp-Al2O3nano-composite powders

    , Article Journal of Ceramic Processing Research ; Volume 17, Issue 10 , 2016 , Pages 1033-1041 ; 12299162 (ISSN) Tayebi, S ; Mirjalili, F ; Samadi, H ; Nemati, A ; Sharif University of Technology
    Hanyang University  2016
    Abstract
    Hydroxyapatite is the most important bio ceramic, due to its structure and chemical composition which is similar to bone. Since feeble fracture toughness, brittleness and low tensile strength have restricted their use, for overcoming this problem, they were often used as a secondary component. HAp-Al2O3 nano-composite powder combined the benefits of biocompatibility of HAp and high strength of Al2O3. When HAp-Al2O3 nano-composite powders were sintered at a higher temperature than 1100- 1200°C, HAp was decomposed and converted to the second phase of TCP, due to the formation of calcium aluminate increasing decomposition speed of HAp to TCP at higher degree than 1100-1200°C temperatures;... 

    A TEM investigation on precipitation behavior of AEREX350 superalloy

    , Article 11th International Symposium on Superalloys, Superalloys 2008, Champion, PA, 14 September 2008 through 18 September 2008 ; January , 2008 , Pages 549-552 Sarmee, M ; Asgari, S ; Sharif University of Technology
    2008
    Abstract
    The influence of solution treatment on precipitation behavior of AEREX™350 was investigated using hardness testing, TEM and SEM. Samples were solution treated at 1050°C and 1075°C for 1 hr and then aged at 700°C, 750°C and 800°C for 1,2,4,8 and 25 hrs. It was found that different solution treatment may be used for different applications of AEREX™350  

    Optimization of Synthesis Method and Operational Improvement of High Temperature Water-gas Shift Catalyst

    , M.Sc. Thesis Sharif University of Technology Eshaghian, Razieh (Author) ; Baghghalha, Morteza (Supervisor) ; Kazemeini, Mohammad (Supervisor) ; Bahmani, Mohsen (Co-Advisor)
    Abstract
    The water-gas shift reaction, as a vital reaction in industry especially as a source of hydrogen for the manufacture of ammonia, is influential for all of the scientists and researchers in chemical engineering all around the world. In this research, high temperature water-gas shift (HTS) catalysts were investigated in order to study synthesis parameters and improvement of their performance and catalytic activity. The two catalyst categories; non pre-active and pre-active (magnetite-based samples, not requiring a reduction step prior to use) were prepared by co-precipitation method, using chloride, sulfate and nitrate metal (Fe, Cr, Cu) precursors and NaOH as precipitating agent (the aging... 

    The control of morphological and size properties of carbamazepine-imprinted microspheres and nanospheres under different synthesis conditions

    , Article Journal of Materials Research ; 2013 ; 08842914 (ISSN) Esfandyari Manesh, M ; Javanbakht, M ; Shahmoradi, E ; Dinarvand, R ; Atyabi, F ; Sharif University of Technology
    2013
    Abstract
    Potential applications of the molecularly imprinted polymers (MIPs) demand physical configurations in different size ranges. Nowadays, research on MIPs is focused on the development of new or improved morphologies, which involves control and modification of the different parameters during the synthesis. In this study, the effect of different synthesis conditions on the particle size and morphology is investigated. Carbamazepine-imprinted polymers were prepared using precipitation polymerization under various conditions such as: the amounts of cross-linker and functional monomers, initiator, porogen, temperature and time of polymerization. We studied the polymerization conditions to obtain... 

    Multi directional forging of 2024 Al alloy after different heat treatments: Microstructural and mechanical behavior

    , Article Transactions of the Indian Institute of Metals ; 2016 , Pages 1-13 ; 09722815 (ISSN) Asadi, S ; Kazeminezhad, M ; Sharif University of Technology
    Springer India 
    Abstract
    Improvement of mechanical properties and microstructure of 2024 aluminum alloy by performing a severe plastic deformation method, called multidirectional forging (MDF), and heat treatment was the aim of this research. In this work, the effects of different heat treatments such as annealing, solid solution, peak ageing and over ageing before MDF on mechanical properties and microstructure of the alloy were studied. Microstructure evolution during severe plastic deformation was considerably affected by the precipitates and non-shearable particles. On the other hand, the severe plastic deformation had different effects on precipitates in the microstructure. Fragmentation, scattering and... 

    Multi directional forging of 2024 Al alloy after different heat treatments: microstructural and mechanical behavior

    , Article Transactions of the Indian Institute of Metals ; Volume 70, Issue 7 , 2017 , Pages 1707-1719 ; 09722815 (ISSN) Asadi, S ; Kazeminezhad, M ; Sharif University of Technology
    Abstract
    Improvement of mechanical properties and microstructure of 2024 aluminum alloy by performing a severe plastic deformation method, called multidirectional forging (MDF), and heat treatment was the aim of this research. In this work, the effects of different heat treatments such as annealing, solid solution, peak ageing and over ageing before MDF on mechanical properties and microstructure of the alloy were studied. Microstructure evolution during severe plastic deformation was considerably affected by the precipitates and non-shearable particles. On the other hand, the severe plastic deformation had different effects on precipitates in the microstructure. Fragmentation, scattering and... 

    Deformation behavior and cavitation of AA2017 at elevated temperatures

    , Article Metals and Materials International ; 2020 Vaghefi, E ; Serajzadeh, S ; Sharif University of Technology
    Korean Institute of Metals and Materials  2020
    Abstract
    In this work, deformation behavior of AA2017-T4 at elevated temperatures was studied employing uni-axial tensile and creep experiments. Tensile tests were carried out at temperatures varying 150–500 °C under different strain rates then, a combination of neural network and dynamic material modeling was utilized to construct the processing maps. Furthermore, creep experiments were conducted to assess inelastic deformation behavior of the alloy at temperatures between 150 and 225 °C and stresses in the range of 150 to 230 MPa. Microstructural evaluations were carried out for determination of microstructural changes and formation of voids and cavities within the samples. The results showed that... 

    Asphaltene deposition in different depositing environments: Part 2. Real oil

    , Article Energy and Fuels ; Vol. 28, Issue. 6 , 2014 , Pages 3594-3603 ; ISSN: 08870624 Tavakkoli, M ; Panuganti, S. R ; Taghikhani, V ; Pishvaie, M. R ; Chapman, W. G ; Sharif University of Technology
    Abstract
    This paper is a continuation of our previous paper (part 1; 10.1021/ef401857t), which discussed the roles of different phenomena effecting the deposition of asphaltene from model oil systems and before the onset of asphaltene precipitation. The study in this paper is to understand the depositional tendency of asphaltene using a quartz crystal microbalance with dissipation (QCM-D) measurements and their corresponding modeling for real crude oil systems with emphasis after the onset of asphaltene precipitation  

    Effect of deep cryogenic treatment on wear resistance and tool life of M2 HSS drill

    , Article Journal of Materials Processing Technology ; Volume 206, Issue 1-3 , 12 September , 2008 , Pages 467-472 ; 09240136 (ISSN) Firouzdor, V ; Nejati, E ; Khomamizadeh, F ; Sharif University of Technology
    2008
    Abstract
    The influence of deep cryogenic treatment on wear resistance and tool life of M2 HSS drills in high-speed dry drilling configuration of carbon steels was studied. The experimental results indicated 77 and 126% improvement in cryogenic-treated and cryogenic- and temper-treated drill lives, respectively. The results of wear rate test were in agreement with drill life test. Chemical composition of chips were also reported to show the onset of seizure in drilling test and the consequence of seizure in promoting dissolution wear by diffusion mechanism. Wear resistance improvement was mainly attributed to the resistance of cryogenically treated drills against diffusion wear mechanism, due to the... 

    An investigation into the microstructure of friction-stir welded and artificially aged AA2017

    , Article Journal of Materials Engineering and Performance ; Volume 22, Issue 11 , 2013 , Pages 3566-3571 ; 10599495 (ISSN) Mirjalili, A ; Aval, H. J ; Serajzadeh, S ; Sharif University of Technology
    2013
    Abstract
    Microstructural changes in friction-stir welding (FSW) of artificially aged AA2017 were investigated. First, FSW was performed with rotational and linear speeds of 800 rpm and 40 mm/min, respectively. Then, microstructural studies by means of optical metallography and electron microscopy were conducted in different regions of the welded plates. Hardness testing was also employed to determine local strength and subsequent natural aging progress after welding. The results indicate that the considerable hardness degradation occurs in the thermo-mechanically affected zone owing to coarsening of semi-coherent precipitates. Grain refinement also takes place in the weld nugget as a result of... 

    Experimental and modelling investigations of asphaltene precipitation during pressure depletion and gas injection operations

    , Article Petroleum Science and Technology ; Vol. 32, issue. 15 , August , 2014 , pp. 1868-1875 ; ISSN: 10916466 Nakhli, H ; Alizadeh, A ; Afshari, S ; Kharrat, R ; Ghazanfari, M ; Sharif University of Technology
    Abstract
    Asphaltene precipitation problems manifest themselves in different stages of oil reservoirs production. Experimental and modeling investigations are, therefore, employed as promising tools to assist in predictions of asphaltene precipitation problems and selection of proper production facilities. This study concerns experimental and modeling investigations of asphaltene precipitation during natural production and gas injection operations for a heavy Iranian crude oil at reservoir conditions. First, with design and performance of high pressure-high temperature experiments, asphaltene precipitation behavior is comprehensively investigated; the effects of pressure and temperature are fully... 

    Solidification and solid state phenomena during TLP bonding of IN718 superalloy using Ni-Si-B ternary filler alloy

    , Article Journal of Alloys and Compounds ; Volume 563 , 2013 , Pages 143-149 ; 09258388 (ISSN) Pouranvari, M ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
    2013
    Abstract
    This paper addresses solidification and solid state precipitation phenomena during transient liquid phase (TLP) bonding of wrought IN718 nickel base superalloy using Ni-4.5Si-3.2B (wt.%) ternary filler alloy. The solidification sequence of the residual liquid in the joint centerline was found to be (1) formation of proeutectic γ, followed by (2) γ/Ni3B eutectic reaction, followed by (3) ternary eutectic of γ/Ni 3B/Ni6Si2B. Extensive fine Ni3Si formed within the eutectic-γ via solid state precipitation during cooling. Extensive Cr-Mo-Nb rich boride precipitates were formed in the substrate region due to boron diffusion into the base metal during bonding process. The implications of the phase... 

    A modified thermodynamic modeling of wax precipitation in crude oil based on PC-SAFT model

    , Article Fluid Phase Equilibria ; Volume 429 , 2016 , Pages 313-324 ; 03783812 (ISSN) Mashhadi Meighani, H ; Ghotbi, C ; Jafari Behbahani, T ; Sharif University of Technology
    Elsevier  2016
    Abstract
    Wax precipitation may occur in production or transportation of crude oil form field which is a serious problem in petroleum industry. Flow assurance issues concerning wax precipitation make it necessary to develop a precise thermodynamic model to predict the wax appearance temperature and amount of precipitation at different conditions. In this work a new procedure has been proposed to characterize crude oil based on the SARA test considering the wax and asphaltene as single pseudo components. Two scenarios have been investigated for the survey of the crude oil characterization, with and without asphaltene pseudo component. Also, in this work, the Perturbed Chain form of the Statistical... 

    Kinetics of oxygen adsorption on ZnS nanoparticles synthesized by precipitation process

    , Article Materials Science- Poland ; Volume 34, Issue 2 , 2016 , Pages 260-265 ; 20831331 (ISSN) Ahmadi, R ; Sadrnezhad, S. K ; Namivandi Zangeneh, R ; Oghabian, M. A ; Sharif University of Technology
    Walter de Gruyter GmbH 
    Abstract
    ZnS nanoparticles were synthesized through a one-step precipitation process. Effect of time and temperature on the formation reaction was investigated. The synthesized samples were characterized by X-ray diffraction (XRD), ultraviolet (UV) visible absorption and photoluminescence (PL) spectrophotometry. Based on XRD and UV-Vis data, the particles produced at 70 °C had a mean particle size of about 5 nm. Increasing time and temperature of the synthesis reaction resulted in photoluminescence intensification. PL spectroscopy helped understanding the adsorption kinetics of oxygen on ZnS nanoparticles during the precipitation synthesis process. Fabrication of ZnS structures with appropriate...