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Microstructural evolution in the transient-liquid-phase bonding area of IN-738LC/BNi-3/IN-738LC
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 39, Issue 10 , 2008 , Pages 2389-2402 ; 10735623 (ISSN) ; Ekrami, A ; Ohsasa, K ; Matsuura, K ; Sharif University of Technology
2008
Abstract
Transient-liquid-phase (TLP) bonding of the IN-738LC base alloy with BNi-3 interlayer was investigated in this article. Effects of the TLP bonding thermal cycle on the base alloy were studied microstructurally and macrostructurally. Microscopic investigation revealed that the microstructural evolution in the TLP bonding area was affected substantially by the bonding temperature. Therefore, a critical bonding temperature (Tcr) was defined for TLP bonding of IN-738LC/ BNi-3/IN-738LC samples. Unlike bonding below Tcr, TLP bonding at temperatures higher than Tcr resulted in formation of individual γ-γ' colonies in the adjacent base alloy to TLP bonding zone and caused significant reduction in...
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 ; Kokabi, A. H ; Sharif University of Technology
Abstract
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...
Microstructural and mechanical evaluation of submerged arc welded HSLA 4135 steel by modeled and manufactured granular Cr-Mo bonded active basic flux
, Article Journal of Materials Processing Technology ; Volume 290 , 2021 ; 09240136 (ISSN) ; Mohammadmirzaei, M ; Ebadi, M ; Kokabi, A. H ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Bead-on-plate submerged arc welding was performed on the AISI 4135 heat-treatable low-alloy (HTLA) steel using S2 welding wire and granular Cr-Mo basic flux. The Cr-Mo active flux was produced by the bonded -unfused method. The alloying elements were introduced into the weld metal by active flux. Two methods were introduced for calculating the recovery rate (η) of the alloying elements. Moreover, by defining the slag factor (α) of the process and η of the alloying elements, the amount of a specific element transferred from flux into WM was calculated by the proposed equation. Likewise, microstructure evolutions, inclusions characteristics, longitudinal tensile, indentation, and CVN impact...
Microstructural and mechanical evaluation of submerged arc welded HSLA 4135 steel by modeled and manufactured granular Cr-Mo bonded active basic flux
, Article Journal of Materials Processing Technology ; Volume 290 , 2021 ; 09240136 (ISSN) ; Mohammadmirzaei, M ; Ebadi, M ; Kokabi, A. H ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Bead-on-plate submerged arc welding was performed on the AISI 4135 heat-treatable low-alloy (HTLA) steel using S2 welding wire and granular Cr-Mo basic flux. The Cr-Mo active flux was produced by the bonded -unfused method. The alloying elements were introduced into the weld metal by active flux. Two methods were introduced for calculating the recovery rate (η) of the alloying elements. Moreover, by defining the slag factor (α) of the process and η of the alloying elements, the amount of a specific element transferred from flux into WM was calculated by the proposed equation. Likewise, microstructure evolutions, inclusions characteristics, longitudinal tensile, indentation, and CVN impact...
Study of microstructural evolution and phase's morphology after partial remelting in A356 alloy
, Article Semi-Solid Processing of Alloys and Composites 10 - Selected, peer reviewed papers from the 10th International Conference on Semi-Solid Processing of Alloy and Composites, S2P 2008, Aachen, 16 September 2008 through 18 September 2008 ; Volume 141-143 , 2008 , Pages 367-372 ; 10120394 (ISSN); 9771012039401 (ISBN) ; Bigdeli, M ; Hajian Heidary, M ; Khomamizadeh, F ; Sharif University of Technology
Trans Tech Publications Ltd
2008
Abstract
In this work, effective parameters of SIMA process to obtain non dendritic microstructure in A356 alloy were investigated. In addition, the effect of SIMA process on the evolution of morphology of silicon and intermetallic phases in this alloy was studied. Microstructure images obtained from optical microscopy and SEM observation showed that increase in plastic work up to 40% and then holding of samples in the semi solid state at temperature of 580°C, causes that primary dendritic structure changes to non dendritic, fine and globular structure, but optimum reheating time completely depended on initial thickness of samples. If all parameters of SIMA process are the same, the grain boundaries...
Phase and microstructural evolution of low carbon MgO-C refractories with addition of Fe-catalyzed phenolic resin
, Article Ceramics International ; 2018 ; 02728842 (ISSN) ; Bavand vandchali, M ; Nemati, A ; Golestani Fard, F ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In the present paper, phase and microstructural characterization of low carbon MgO-C refractories with addition of Fe-catalyzed phenolic resins as binder were investigated. Initially, phenolic resin was modified using various amounts of Fe particles as catalyst originated from iron nitrate ([Fe(NO3)3·9H2O]). The MgO-C matrix compositions were prepared by using 7% of modified phenolic resin, shaped and cured at 200 °C for 24 h. The cured samples were coked in the temperature range from 800 to 1400 °C and then characterized by XRD and FE-SEM techniques. Based on attained results, in-situ graphitic carbons, particularly in carbon nanotubes (CNTs) network were gradually formed from Fe-catalyzed...
Effect of interlayers on softening of aluminum friction stir welds
, Article Materials Science and Engineering A ; Volume 727 , 2018 , Pages 1-10 ; 09215093 (ISSN) ; Movahedi, M ; Kokabi, A. H ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Effects of the zinc, copper and brass interlayers were studied on the microstructure evolution and mechanical properties of the wrought aluminum friction stir welds. Optical and scanning electron microscopes (SEM) as well as X-ray diffraction (XRD) analysis were used for investigation of the distribution, dissolution and reactions of the interlayers, grain structure in the stir zone and fracture surfaces. Longitudinal and transverse tensile and microhardness tests were also carried out in order to evaluate the mechanical properties of the welds. The results showed that without insertion of the interlayer, the joint efficiency (ratio of the weld strength to the aluminum base metal strength)...
Heat transfer on topographically structured surfaces for power law fluids
, Article International Journal of Heat and Mass Transfer ; Volume 121 , 2018 , Pages 857-871 ; 00179310 (ISSN) ; Moosavi, A ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The three-dimensional power law fluid flow through rough microchannels has been studied numerically to determine the effects of the topographic structures on the thermal and hydrodynamic characteristics of the system. Rectangular, triangular and sinusoidal element shapes have been considered in order to investigate the effects of roughness height, width, pitch and channel separation on the pressure drop and heat transfer. Uniform wall heat flux boundary condition has been applied for all the peripheral walls. The results indicate that the global heat transfer performance can be improved or reduced by the roughness elements at the expense of pressure head when compared with the smooth...
Phase and microstructural evolution of low carbon MgO-C refractories with addition of Fe-catalyzed phenolic resin
, Article Ceramics International ; Volume 45, Issue 3 , 2019 , Pages 3390-3406 ; 02728842 (ISSN) ; Bavand vandchali, M ; Nemati, A ; Golestani Fard, F ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In the present paper, phase and microstructural characterization of low carbon MgO-C refractories with addition of Fe-catalyzed phenolic resins as binder were investigated. Initially, phenolic resin was modified using various amounts of Fe particles as catalyst originated from iron nitrate ([Fe(NO3)3·9H2O]). The MgO-C matrix compositions were prepared by using 7% of modified phenolic resin, shaped and cured at 200 °C for 24 h. The cured samples were coked in the temperature range from 800 to 1400 °C and then characterized by XRD and FE-SEM techniques. Based on attained results, in-situ graphitic carbons, particularly in carbon nanotubes (CNTs) network were gradually formed from Fe-catalyzed...
Influence of new superhydrophobic micro-structures on delaying ice formation
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 595 , 2020 ; Taeibi Rahni, M ; Javadi, K ; Davoudian, S. H ; Miller, R ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Drop motion on different types of new proposed micro-structure surfaces has been numerically investigated to find the optimum structure in view point of ice formation delaying. The droplet automatically moves on the inclined surfaces due to gravity forces. To validate the numerical algorithm, three different bench mark problems have been considered. The results indicate that the present algorithm is trustable for the presented numerical simulations. Then the validated numerical approach has been used to simulate droplet motion on nine proposed superhydrophobic surfaces in the same conditions. Comparison the drop motion on different micro-structure surfaces at different time indicate that...
Experimental Investigation of Effective Parameters on Performance of Micro-sized Bio-electrochemical Systems
, M.Sc. Thesis Sharif University of Technology ; Yaghmaei, Soheila (Supervisor)
Abstract
This study is a report on the fabrication of a novel single-chamber micro-structure microbial fuel cell consisting of spiral anode chamber. A 3×3 cm plexiglass plate with 1 mm thickness was used as main body. A spiral microchannel (1 mm in width and 226 mm in length) was cut using a laser beam as an anodic compartment. Two types of microbial fuel cells with the same anode electrode (stainless steel mesh) and different cathode electrodes (stainless steel mesh and carbon cloth) were constructed in order to investigate the effect of cathode electrode material on microbial fuel cell performance. In both batch and continuous mode, higher power density was obtained by microbial fuel cell with...
TLP Bonding of Ferrite - Martensite Dual Phase Steel and Comparison with Fusion Welding Method
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor)
Abstract
In this study, low carbon plain steels joined with TLP bonding method using Fe-44Ni-7B-4Mo interlayer, The bonding parameters (holding time, temperature) have been changed to find optimum conditions of TLP bonding. Microstructure and properties of joints have also been investigated. Dual phase processing of the used steel has been carried out during joints homogenization. Microstructural studies with scanning electron microscope and optical microscope showed that isothermal solidification completed at holding for 50 minutes at the bonding temperature of 1180℃. These parameters are taken as optimum conditions of TLP bonding. Microstructure of the isothermally solidified zone (joint region)...
An electron back-scattered diffraction study on the microstructure evolution of severely deformed aluminum AI6061 alloy
, Article IOP Conference Series: Materials Science and Engineering ; Vol. 63, Issue. 1 , 30 June- 4 July , 2014 ; ISSN: 17578981 ; Taheri, A. K ; Kim, H. S ; Sharif University of Technology
Abstract
In this paper dynamic strain ageing behavior in an Al-Mg-Si alloy related to equal channel angular pressing (ECAP) was investigated. In order to examine the combined plastic deformation and ageing effects on microstructure evolutions and strengthening characteristics, the Al6061 alloy were subjected to φ=90° ECAP die for up to 4 passes via route Bc at high temperatures. For investigating the effects of ageing temperature and strain rate in ECAP, Vickers hardness tests were performed. The combination of the ECAP process with dynamic ageing at higher temperatures resulted in a significant increase in hardness. The microstructural evolution of the samples was studied using electron...
Effects of current density on microstructure and corrosion property of coating on AZ31 Mg alloy processed via plasma electrolytic oxidation
, Article Magnesium Technology ; February , 2014 , pp. 345-349 ; ISSN: 15454150 ; ISBN: 9781118888162 ; Einkhah, F ; Sani, M. A. F ; Ko, Y. G ; Shin, D. H ; Sharif University of Technology
Abstract
The effects of the current density on the microstructure and the corrosion property of the coating on AZ31 Mg alloy processed by the plasma electrolytic oxidation (PEO) were investigated. The present coatings were produced in an acid electrolyte containing K2ZrF6 with three different current densities, i.e., 100, 150, and 200 mA/cm2. From the microstructural observations, as the applied current density was increased, the diameter of micro-pores formed by the plasma discharges with high temperature increased. The coatings on AZ31 Mg alloy were mainly composed of MgO, ZrO 2, MgF2, and Mg2Zr5O12 phases. The results of potentiodynamic polarization clearly showed that the PEO-treated AZ31 Mg...
The effect of Ti on mechanical properties of extruded in-situ Al-15 pct Mg2Si composite
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 44, Issue 9 , September , 2013 , Pages 4366-4373 ; 10735623 (ISSN) ; Bahrami, A ; Pech Canul, M. I ; Sharif University of Technology
2013
Abstract
This work was carried out to investigate the effect of different Ti concentrations as a modifying agent on the microstructure and tensile properties of an in-situ Al-15 pctMg2Si composite. Cast, modified, homogenized small ingots were extruded at 753 K (480°C) at the extrusion ratio of 18:1 and ram speed of 1 mm/s. Various techniques including metallography, tensile testing, scanning electron microscopy were used to characterize the mechanical behavior, microstructural observations, fracture mechanisms of this composite. The results showed that 0.5 pctTi addition and homogenizing treatment were highly effective in modifying Mg2Si particles. The results also exhibited that the addition of Ti...
Microstructure based modelling of flow behaviour of Al-Mg-Si alloy at different temper conditions
, Article Materials Science and Technology (United Kingdom) ; Volume 29, Issue 8 , 2013 , Pages 968-974 ; 02670836 (ISSN) ; Karimi Taheri, A ; Sharif University of Technology
2013
Abstract
A new integrated physically based constitutive model was developed for an age hardenable Al- Mg-Si alloy. The kinetics of precipitation during various stages of aging was modelled. The precipitate features consisted of particle radius and volume fraction obtained from the kinetics model, which was used to compute the alloy yield strength/hardness. A published multiinternal variable workhardening model was improved to take into account the effects of solute solution and precipitates on the alloy hardening capacity after performing different cycles of aging treatment. The flow curves and hardness predicted by the model were in good agreement with the experimental results. The model is able to...
Investigation of the effect of tungsten substitution on microstructure and abrasive wear performance of in situ vc-reinforced high-manganese austenitic steel matrix composite
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 44, Issue 8 , 2013 , Pages 3826-3835 ; 10735623 (ISSN) ; Karimzadeh, N ; Varahram, N ; Davami, P ; Sharif University of Technology
2013
Abstract
Particulate VC-reinforced high-manganese austenitic steel matrix composites with different vanadium and tungsten contents were synthesized by conventional alloying and casting route. Microstructural characterizations showed that the composites processed by in situ precipitation of the reinforcements were composed of V8C7 particulates distributed in an austenitic matrix. It was observed that addition of tungsten to austenite increases work-hardening rate of subsurface layer during pin-on disk wear test. The maximum abrasive wear resistance was achieved at tungsten content equal to 2 wt pct. However, excessive addition of tungsten promoted the formation of W 3C phase and reduced the abrasive...
Microstructure-Mechanical properties relation of tlp-bonded fsx-414 superalloy: effect of homogenization design
, Article Journal of Materials Engineering and Performance ; Volume 24, Issue 4 , April , 2015 , Pages 1687-1696 ; 10599495 (ISSN) ; Ekrami, A ; Khan, T. I ; Sharif University of Technology
Springer New York LLC
2015
Abstract
Co-based FSX-414 superalloy is especially used for first-stage nozzles of gas turbines. Transient liquid phase (TLP) bonding has potential as repair process for these nozzles. In this study, homogenization of TLP-bonded FSX-414 superalloy at optimum bonding condition (1150 °C/5 min) was conducted at 1175, 1200, and 1225 °C for 1, 3, and 6 h. Homogenization at 1175 °C/1 h had no effect on removing the diffusion-affected zone (DAZ) phases. Increasing the time to 6 h was effective in removing DAZ phases and boride phases formed due to liquefaction, but compositional homogenization was not complete. Homogenization at 1200 °C for 1 h caused boride phases to form adjacent to the joint and in the...
Investigation into dynamic strain aging behaviour in high carbon steel
, Article Ironmaking and Steelmaking ; Volume 37, Issue 2 , Jul , 2010 , Pages 155-160 ; 03019233 (ISSN) ; Sadeghi, A. R ; Akhgar, J. M ; Serajzadeh, S ; Sharif University of Technology
2010
Abstract
In this work, the phenomenon of dynamic strain aging in a high carbon steel is studied and different initial microstructures including fine and coarse pearlite structures are considered. Tensile tests at different temperatures and strain rates are performed to evaluate the occurrence of dynamic strain aging and mechanical properties as well as to calculate apparent activation energies for onset and termination of dynamic strain aging. The results show that dynamic strain aging occurs for both microstructures while the initial microstructures alters the activation energies for appearance and termination of this phenomenon. The microstructural studies illustrate that a combination of cementite...
High voltage SnO2 varistors prepared from nanocrystalline powders
, Article Journal of Materials Science: Materials in Electronics ; Volume 21, Issue 2 , 2010 , Pages 199-205 ; 09574522 (ISSN) ; Shojaee, S. A ; Nemati, A ; Sani, M. A. F ; Sharif University of Technology
2010
Abstract
In this study, SnO 2-based varistors were prepared from mechanically activated nanocrystalline powders. Nanocrystalline powders were derived by subjecting the initial powders to intensive high-energy activation with different times and ball to powder ratio. The effect of activation parameters on the powder properties and sintering temperature, as well as microstructural, micro-electrical and macro-electrical properties of the final specimens was evaluated. Varistors derived from high-energy mechanical activation exhibit a higher density (98.3% relative density) and more refined microstructure upon sintering at 1,300 °C in comparison varistors prepared from conventional powders. Breakdown...