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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 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...
TLP bonding of cast IN718 nickel based superalloy: Process-microstructure-strength characteristics
, Article Materials Science and Engineering A ; Volume 568 , 2013 , Pages 76-82 ; 09215093 (ISSN) ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
2013
Abstract
This paper aims at addressing the microstructure-strength characteristics relationship during transient liquid phase (TLP) bonding of cast IN718 nickel based superalloy using Ni-7. Cr-4.5. Si-3. Fe-3.2. B (wt%) amorphous interlayer. The progress of the isothermal solidification at different temperatures for different times is analyzed using a Larson-Miller parameter (LMP). It was found that there is direct relationship between isothermal solidification zone (ISZ) size and LMP. Results showed that in situation where isothermal solidification has not been completed, the ratio of athermal solidification zone (ASZ) size to the width of the total solidified zone is the controlling factor for...
Solute redistribution during transient liquid phase bonding of IN738LC with BNi-3 interlayer
, Article Materials Science and Technology ; Volume 24, Issue 4 , 2008 , Pages 449-456 ; 02670836 (ISSN) ; Ekrami, A ; Ohsasa, K ; Matsuura, K ; Sharif University of Technology
2008
Abstract
Redistribution of alloying elements in the transient liquid phase (TLP) bonding zone of IN738LC/ BNi-3/IN738LC was studied to investigate microstructural evolution in this area. Wavelength dispersive spectrometry and electron probe microanalysis revealed that, during non-isothermal solidification in the TLP bonding zone, enrichment of residual liquid phase with the positive segregating elements caused formation of intermetallic in the bonding zone. Scanning electron microscopy observation Indicated that the redistribution of alloying elements, between TLP bonding zone and base alloy, resulted In formation of a γ′ boundary layer, containing high density of fine γ′, around the bonding zone....
Microstructural Evaluation during dissimilar transient liquid phase bonding of TiAl/Ni-based superalloy
, Article Journal of Alloys and Compounds ; Volume 825 , June , 2020 ; Kaflou, A ; Gholamipour, R ; Pouranvari, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The paper aims at understanding solidification phenomena and solid state precipitations during dissimilar transient liquid phase bonding of γ-TiAl intermetallic compound to IN718 Ni-based superalloy using a quinary Ni–7Cr–3Fe–4.5Si–3.2B (wt%) filler metal. The mechanisms of intermetallic formation via solidification and solid state reactions are discussed. The joint is featured by the formation of Ni-rich solid solution in an isothermal solidification zone near to IN718, Ni-rich solid solution and isostructural binary phases solid solution designated as Al1-xNi3Six in an isothermal solidification zone near to TiAl, boride/silicide and boro-silicide formation during binary and ternary...
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) ; 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...
Effect of solidification mechanism on microstructure and mechanical properties of joint in TLP bonded Al2024-T6 alloy
, Article Science and Technology of Welding and Joining ; Volume 16, Issue 2 , Nov , 2011 , Pages 174-180 ; 13621718 (ISSN) ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
2011
Abstract
Transient liquid phase (TLP) bonding of Al2024-T6 alloy, using gallium (Ga) interlayer, has been investigated. Bonding process was carried out at 470°C for 6 min, and homogenising temperature and time were 495°C and 2 h respectively. Conventional TLP bonding using Ga interlayer was not an appropriate method for joining of Al2024. In this method, the boundary between two Al2024 specimens was not fully eliminated during bonding because of solidification with planar front. In addition, bonding zone was depleted of copper, and as a result, tensile and shear strength of joint decreased to 200 and 110 MPa respectively. TLP bonding under temperature gradient offered very good results in bonding of...
Role of base-metal composition in isothermal solidification during diffusion brazing of nickel-based superalloys
, Article Science and Technology of Welding and Joining ; Volume 23, Issue 1 , 2018 , Pages 13-18 ; 13621718 (ISSN) ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
The key feature of diffusion brazing, also referred to as transient liquid phase bonding, is isothermal solidification which precludes the formation of intermetallic in the joint centreline. Analysing the available data published in the literature showed that the composition of the nickel-based superalloys plays a strong role in determining the required time for obtaining intermetallic-free joint during diffusion brazing. This effect is not predictable by the standard conventional models. It is proposed that increasing the boride-forming elements in the base superalloy which promotes in situ boride precipitation at the diffusion-affected zone can accelerate the diffusion flux of the boron...
The effect of gap size on the microstructure and mechanical properties of the transient liquid phase bonded FSX-414 superalloy
, Article Materials and Design ; Volume 40 , September , 2012 , Pages 130-137 ; 02641275 (ISSN) ; Ekrami, A ; Sharif University of Technology
Elsevier
2012
Abstract
Optimization of transient liquid phase (TLP) bonding variables is essential to achieve a joint free from deleterious intermetallic constituents as well as with appropriate mechanical properties. In this research, TLP bonding of FSX-414 superalloy was performed using the MBF-80 interlayer. The effects of bonding time (1-30. min) and gap size (25-100 μm) were studied on the joint microstructure and its mechanical properties. Continuous centerline eutectic phases, characterized as nickel-rich and chromium-rich borides, were observed at the joints with incomplete isothermal solidification. The globular and acicular phases were seen at diffusion affected zone (DAZ). These phases could be...
The effect of TLP bonding temperature on microstructural and mechanical property of joints made using FSX-414 superalloy
, Article Materials Science and Engineering A ; Volume 546 , June , 2012 , Pages 291-300 ; 09215093 (ISSN) ; Ekrami, A ; Khan, T. I ; Sharif University of Technology
2012
Abstract
The bonding temperature is an important parameter for optimization of the Transient Liquid Phase (TLP) bonding process in order to achieve a sound joint with good mechanical properties. However, the bonding temperature used can also be restricted by the microstructural stability of the base metal. In this study, the effect of bonding temperature (1050-1200 °C) on the joint microstructure and mechanical properties was studied for TLP bonding of FSX-414 superalloy using MBF-80 interlayer with thickness of 50 μm. Increasing bonding temperature from 1050 to 1150 °C caused reduction in the time required for complete isothermal solidification in agreement with models based on the diffusion induced...
Transient liquid phase bonding of FSX-414 superalloy at the standard heat treatment condition
, Article Materials Characterization ; Volume 66 , 2012 , Pages 38-45 ; 10445803 (ISSN) ; Ekrami, A ; Sharif University of Technology
2012
Abstract
The as-cast samples of FSX-414 Co-based superalloy were heat treated at the standard solution and aging heat treatment cycles. Specimens for joining were cut from the as-cast ingot. Transient liquid phase (TLP) bonding was carried out at the standard solution cycle, using MBF-30 interlayer. Also, bonded specimens were homogenized at the standard aging condition. The microstructure of the as-cast, heat treated and TLP bonded specimens were studied. These studies showed that the non-uniform distributed carbides of the as-cast specimen were replaced by uniform ones during the heat treatment. Eutectic M 23C 6 carbides were observed in all specimens. Due to the complete isothermal solidification,...
Microstructural changes of FSX-414 superalloy during TLP bonding
, Article Defect and Diffusion Forum ; Volume 312-315 , 2011 , Pages 399-404 ; 10120386 (ISSN) ; 9783037851173 (ISBN) ; Ekrami, A ; Sharif University of Technology
Abstract
The as-cast FSX-414 Co-based superalloy samples were solution treated at 1150°C for 4h and then aged at 980°C for 4h. Specimens for joining were cut from the as-cast ingot and TLP bonding carried out at the same conditions as for the solution and solution+aging treatment, using MBF-30 interlayer. Microstructures were studied for as-cast, heat treated and TLP bonded specimens. These studies showed that the ununiform distributed carbides of MC type in the as-cast specimens replaced by M23C6 type carbides with uniform distribution in the heat treated microstructure. Due to complete isothermal solidification, no eutectic structure in the bond region were wasobserved, but some intermetallics in...
Effect of bonding temperature on microstructure development during TLP bonding of a nickel base superalloy
, Article Journal of Alloys and Compounds ; Volume 469, Issue 1-2 , 2009 , Pages 270-275 ; 09258388 (ISSN) ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
2009
Abstract
The effect of bonding temperature on microstructure of a transient liquid phase (TLP)-bonded GTD-111 nickel base superalloy, using a Ni-Si-B interlayer, was investigated. At low bonding temperatures microstructure of the joint centerline is controlled by B diffusion. However, at high bonding temperature effect of base metal alloying elements on the joint microstructure development was more pronounced. Effects of bonding temperature on the formation of secondary precipitates in diffusion-affected zone and isothermal solidification time were also analyzed. It was found that above a critical temperature, formation of borides in diffusion-affected zone is suppressed and the time required for...