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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...
A New Approach Towards Modified Single Drop Microextraction Using Solvents with Densities Higher than Water
, M.Sc. Thesis Sharif University of Technology ; Bagheri, Habib (Supervisor)
Abstract
In the present work, the combination of single drop liquid phase microextraction and gas chromatography-mass detector (GC-MS) was used for determination of pesticides, Clodinafop, Haloxyfop and Fenoxyprop in natural water samples. a novel techniques based on SDME for develop in which solvents with higher density than water was successfully used. this technique could overcome some limitations of conventional SDME such as instability of organic droplet and limited stirrer rate in which result increasing the mass transfer rate and extraction efficiency. Experimental liquid phase microextraction (LPME) conditions, such as extracting solvent, stirring rate, micro drop volume, extraction time, pH...
Effect of the bonding time on the microstructure and mechanical properties of a transient-liquid-phase bonded in718 using a Ni-Cr-B filler alloy
, Article Materiali in Tehnologije ; Volume 47, Issue 5 , 2013 , Pages 593-599 ; 15802949 (ISSN) ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
2013
Abstract
The paper aims at addressing the effect of the bonding time on the metallurgical and mechanical properties of a transient-liquid-phase (TLP) bonded IN718 nickel-based superalloy using an Ni-15.2Cr-4B (%) amorphous filler alloy. The results showed that after a partial isothermal solidification, the residual liquid in the joint centerline transformed, during the cooling, to non-equilibrium eutectic-type microconstituents composed of Ni-rich boride, Cr-rich boride and eutectic γ-solid solution phase. The complete isothermal solidification which resulted in a formation of an intermetallic-free joint centerline occurred after a holding period 40 min at the bonding temperature of 1100 °C. An...
Microstructure and mechanical properties of dual phase steels, with different martensite morphology, produced during TLP bonding of a low C-Mn steel
, Article Metals and Materials International ; Volume 22, Issue 5 , 2016 , Pages 856-862 ; 15989623 (ISSN) ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
Korean Institute of Metals and Materials
Abstract
In this research, production of ferrite - martensite dual phase Steels with different martensite morphology was considered during transient liquid phase bonding of a low carbon steel. The steel was bonded using an iron base interlayer with melting point of 1443 K and 40 μm thickness. Bonding process carried out at 1473 K, under pressure of 0.5 MPa, at different holding time of 10, 20, 30 and 40 minutes. Microstructural studies of joint region showed that isothermal solidification completed at the bonding time of 40 minutes. Microstructure of joints made at the bonding time of 10, 20, and 30 minutes consists of two distinct region, athermal and isothermal solidified zones. Microstructure of...
An investigation on the sintering behavior of high strength Al-Zn-Mg-Cu alloy prepared from elemental powders
, Article 2006 Powder Metallurgy World Congress and Exhibition, PM 2006, Busan, 24 September 2006 through 28 September 2006 ; Volume 534-536, Issue PART 1 , 2007 , Pages 489-492 ; 02555476 (ISSN); 0878494197 (ISBN); 9780878494194 (ISBN) ; Sirnchi, A ; Danninger, H ; Arvand, A ; Sharif University of Technology
Trans Tech Publications Ltd
2007
Abstract
In the present work, the sintering behavior of high strength Al-5.6Zn-2.5Mg-1.6Cu (in wt.%) alloy compacts was investigated. Green parts made by pressing of mixed elemental powders were sintered at different temperatures between 400 and 600°C The effect of the sintering temperature on density, dimensional change and microstructure of the Al alloy was studied. Microstructural evaluation was accompanied by XRD and DSC methods in order to determine the temperature and chemical composition of the liquid phases formed during sintering. It was found that three transient liquid phases are formed at 420, 439 and 450°C Microstructural study revealed the progressive formation of sintered contacts due...
Effect of TLP Bonding on Microstructure and Thermal Fatigue Properties of Co-Based FSX-414 Superalloy
, Ph.D. Dissertation Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor)
Abstract
In this research, transient liquid phase (TLP) bonding of FSX-414 superalloy was investigated using MBF-80 interlayer. The bonding was performed at different temperatures (1050-1200oC) for various times (1-120min). Also, different gap sizes were studied using the interlayer with various thicknesses (25-100µm). Homogenizing treatment was performed at different temperatures (1175-1225oC) and times (1-6h) for the samples with complete isothermal solidification. The microstructure of the samples were studied using the optical, scanning electron and transmission electron microscopes. Also, XRD, SEM/EDS, SEM/WDS and TEM/EDS analyses were used to analyse the observed phases at the joints. To...
Production of zinc oxide nanoparticles by liquid phase processing: An investigation on optical properties
, Article 2nd International Conference on Diffusion in Solids and Liquids, DSL-2006, Aveiro, 26 July 2006 through 28 July 2006 ; Volume 553 , 2007 , Pages 252-256 ; 02555476 (ISSN); 0878494383 (ISBN); 9780878494385 (ISBN) ; Youzbashizade, H ; Sharif University of Technology
Trans Tech Publications Ltd
2007
Abstract
In the recent years, many researchers have been interested in nanoparticles because of their unique properties. In this study, a method for producing ZnO nanoparticle colloids is proposed. The colloids were characterized by spectroscopic analyzer. By absorption spectrum study, we found out that colloids were consisted of nanoparticles with less than 10 nanometer size. The quantum confinement effect in these spectrums was recognized through blue shift of onset absorption wavelengths. These wavelengths shift from 370 nm to 340 nm by decreasing the particles size. Transmittion electron micrographs showed formation of zinc oxide nanoparticles
Aging response of transient liquid phase bonded wrought IN718 superalloy: Influence of post-bond heat treatment
, Article Science and Technology of Welding and Joining ; Vol. 19, issue. 2 , February , 2014 , pp. 105-110 ; ISSN: 13621718 ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
Abstract
Aging response of transient liquid phase Nb bearing wrought IN718 nickel base superalloy is studied. The aging behaviour of the joint is influenced by low Nb+Al+Ti content of isothermal solidification zone (ISZ) and formation of Nb-Cr-Mo based boride precipitates in diffusion affected zone (DAZ). It was shown that applying a post-bond heat treatment which was able to eliminate the diffusion induced boride precipitates in DAZ and increase the Nb+Al+Ti content of the ISZ improved the aging response and shear strength of the joint
Transient liquid phase bonding of wrought IN718 nickel based superalloy using standard heat treatment cycles: Microstructure and mechanical properties
, Article Materials and Design ; Volume 50 , 2013 , Pages 694-701 ; 02641275 (ISSN) ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
Elsevier Ltd
2013
Abstract
Transient liquid phase (TLP) diffusion bonding is a preferred joining/repairing technique for nickel based superalloy. In this research, TLP bonding process carried out according to the standard heat treatment cycles for wrought IN718 base material in order to permit the combining of these two thermal operations. The results showed that the standard solution treatments at 1000 and 1050. °C for 60. min can result in completion of isothermal solidification in IN718/Ni-Cr-Fe-Si-B/IN718 system producing an entirely intermetallic free joint centerline. Two distinct microstructural zones were formed in the bonding affected zone: isothermal solidification zone (ISZ) which consists of single phase...
Determining an optimum catalyst for liquid-phase dehydration of methanol to dimethyl ether
, Article Applied Catalysis A: General ; Volume 349, Issue 1-2 , 2008 , Pages 6-12 ; 0926860X (ISSN) ; Kazemeini, M ; Aghaziarati, M ; Sharif University of Technology
2008
Abstract
The liquid-phase dehydration of methanol to dimethyl ether was investigated over various materials including synthetic zeolites, namely, ZSM-5, Y, Mordenite, Ferrierite and Beta as well as silica and alumina. The key characters investigated were the Si/Al ratio and cation exchange. The results showed that the Mordenite zeolite exchanged with H+ exhibited the highest activity in dehydration of methanol. After finding the most active catalyst, the Mordenite zeolite was modified with Cu, Zn, Ni, Al, Zr, Mg and Na via wet-impregnation method to further improve its selectivity, and characterized by AAS, XRD, NH3-TPD, NH3-FT-IR and BET surface area techniques. It was found that these materials...
Effect of Transient Liquid Phase(TLP)Diffusion Bonding on Fatingue Properties of Al 6061-SiC Composite
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor)
Abstract
In the research transient liquid phase bonding of AL6061-SiC composite was performed using copper as interlayer. The joining praocess was performed in various tetemperatures (560c and 580c and 600c) And times (6 and 8 hours). Optimum Joining condition was determined by using optical and of the joint, micro hardness test was performed from the bonding zone to the bulk of the base composite. The fatigue endurance limit of Al6061-SiC composite was determined by several fatigue tests and TLP bonded samples were loaded under achieved endurance limit stress. Finally fatigue fracture surface of both base composite and TLP bonded samples were studied by using of scanning electronic microscope
Effect of Carbon Content on Mechanical Properties of TLP Bonded Ferrite- Martensite Dual Phase Steels
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor)
Abstract
During the last few years researchers have drawn much attention to HSLA steels because of the application of these steels in many industries. Ferrite-martensite dual phase(DP) steels are one of the most common HSLA steels which are currently used. Combination of these two phases provides good strength along with good ductility. Joining and welding of these steels has always been an important challenge. The aim of this study is to examine applicability of TLP method for joining and dual phase processing of this steels at the same time. Microstructural and mechanical examination of the bonded specimens showed that isothermal solidification occurred during holding for 50 min at the...
Microstructure development during transient liquid phase bonding of GTD-111 nickel-based superalloy
, Article Journal of Alloys and Compounds ; Volume 461, Issue 1-2 , 11 August , 2008 , Pages 641-647 ; 09258388 (ISSN) ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
2008
Abstract
Transient liquid phase (TLP) bonding was used to join a nickel-based superalloy GTD-111 using a Ni-Si-B amorphous interlayer, MBF30. Bonding was carried out at 1100 °C with different holding time under vacuum. Joint region microstructure was studied by optical and scanning electron microscopy. Microstructural studies showed that before completion of isothermal solidification, bond region consists of four distinct zones: centerline eutectic structure due to athermal solidification, solid solution phase due to isothermal solidification, diffusion-induced boride precipitates and base metal. Complete isothermal solidification, which prevents formation of centerline eutectic constituent, occurred...
Supersolidus liquid phase sintering of Al6061/SiC metal matrix composites
, Article Powder Metallurgy ; Volume 52, Issue 1 , 2009 , Pages 28-35 ; 00325899 (ISSN) ; Simchi, A ; Sharif University of Technology
2009
Abstract
The aim of the present work is to study the effect of reinforcement content and sintering temperature on the densification and microstructural development during sintering of Al6061/SiC composite compacts. Prealloyed Al6061 powder was mixed with various amounts of SiC particles up to 27 vol.-% and compacted at 350 MPa. Sintering was carried out in a dry nitrogen atmosphere at 580-620°C. It was shown that the presence of SiC particles retards the densification of the prealloyed powder during solid phase sintering and liquid phase sintering. This effect is particularly noticeable at SiC fractions higher than ∼9 vol.-%, at which continuous networks of the hard particles are formed. Increasing...
The Effect of Pressure on Microstructure and Mechanical Properties of TLP Bonded Dual Phase Steels
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor)
Abstract
Dual Phase ferritic-martensitic steels are kind of high strength low alloy steels (HASLA) which are widely used in industry because of their strength and formability. Since welding of dual phase steels in conventional welding methods causes structural change and Subsequently alters mechanical properties of both weld zone and heat affected zone(HAZ), additional operations which are not commercially viable is needed to achieve a dual phase structure in structurally changed regions. In this study, transient liquid phase (TLP) bonding method is used during dual phasing process in order to preserve dual phase ferritic-martensitic structure and avoid extra heat treatment. Applied pressure during...
The Effect of Interlayer Composition on Microstructure and Mechanical Properties of Transient Liquid Phase Bonded Dual Phase Steels
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor)
Abstract
Interlayer composition as one of the most important factors of TLP bonding could affect bonding region composition and microstructure that both of them govern the mechanical properties of the joint. Due to the risk of substrate microstructure degradation , welding of dual phase steel needs more cautions. TLP bonding ideally acquires joints having more similar microstructure to substrate. Moreover , using this method could avoid the change of base metal microstructure when heat treatment of carbon steel is postponed until after bonding. Fe-based , Ni-based and commercially pure Cu are three different composition has been studied in this work. The bonded samples were investigated by optic and...
Transient Liquid Phase Bonding of AA6061/SiC
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor) ; Sayyed Reyhani, Morteza (Supervisor)
Abstract
Composites are made to obtain several mechanical and physical properties selectively. But joining and manufacturing of complex shapes restricts their usages. Transient liquid phase (TLP) bonding is a novel method for joining of these materials without any defects that occur in other welding methods, such as melting or solid state methods. In this research, temperture gradiant TLP bonding of AA6061/SiC/15p using gallium as interlayer was performed. To obtain the optimum conditions, joining was performed at 260, 310, 360 and 410 ˚C, and pressure of 5 and 10 Mpa with holding time of 5 and 10 minutes, the joined samples then solutionized at 530˚C for 70 minutes. Optical and scanning electron...
The Effect of Interlayer Thickness on Microstructure and Mechanical Properties of TLP Bonding on Dual Phase Steel
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor)
Abstract
In this study, the effect of the Cu interlayer thickness was studied on St52 steel. Specimens with different thickness of the interlayer, were subjected to 1150 °C at different times. Isothermal solidification was completed for the thickness of the 50 μm, 30 μm, and 10 μm in 30, 25 and 20 minutes. Afterwards, homogenizing and dual-phase heat treatment were used for 75 minutes at 730°C. Optical microscopy and SEM were used to analyze the microstructure of the joints. Mechanical properties of the joints, including micro hardness of different parts of the joint and also shear strength of the joint zone were studied. The results show that after homogenizing treatment, microstructure and harness...
Microstructural and Mechanical Properties of TLP Bonded SS 304 with Fe-base Interlayer
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor)
Abstract
Cooling sandwich panels are one of the components of the heat exchangers used to cool the components of the sandwich panels . One of the applications of TLP Bonding for steel can be called cooling sandwich panels. In this research , TLP of 304 Stainless Steel , using Fe-base interlayer at 1200 C has been investigated . Cross section of bonded samples were examined by optical and scanning electron microscopes. Microscopy results revealed that 2h is sufficient for completion of isothermal solidification and there is no eutectic compound at bonding zone . Bonding in this condition resulted in the free precipitates in the diffusion affected area. By analyzing eutectic phase in bonding areas at...
The Effect of Some Production Parameters on Microstructure, Physical and Mechanical Properties of Powder Metallurgically Produced (90W-7Ni-3Fe) Heavy Alloy
, M.Sc. Thesis Sharif University of Technology ; PourAzarang, Kazem (Supervisor) ; Abachi, Parvin (Supervisor)
Abstract
In applications requiring high density and good mechanical properties, tungsten heavy alloys are of interest [1]. Due to lack of intermetallic phase in microstructure of 90W-7Ni-3Fe alloy, it is more attractive to use. At present work, the powder metallurgically produced specimens were cold swaged. At this work, during the production and swaging, some parameters were changed. Powders of tungsten, nickel and iron were milled for an hour with the speed of 50 rpm in Retsch Planetry/PM 400 MA ball mill. At the first route, elemental powders mixture after 1 minute were reached to 30MPa, after that were heated at rate of 50°C/min to 1500°C in vacuum (hot press or HP). At the second route, powders...