S.s. Sayyedain, H.r. Salimijazi, M.r. Toroghinejad, F. Karimzadeh.,
Volume 33, Issue 1 (7-2014)
Abstract
Due to their superior properties such as high specific strength, high creep resistance and high strength at elevated temperatures, aluminum composites reinforced with alumina nano particles are widely used for advanced purposes such as aerospace and auto industries. Lack of an appropriate welding process limits their applications. Transient liquid phase (TLP) bonding is one of the state-of-the-art joining processes. It is used for welding composites and advanced materials. Microstructure and mechanical properties of TLP bonding depend on the bonding time and temperature. In the current study, the effect of bonding time on the microstructure and bonding strength of the TLP diffusion bonded of Al2O3p/Al nanocomposite was investigated. A thin layer of copper deposited by electroplating was used as an interlayer. The bonding times of 20 and 40 min were not sufficient for completing the isothermal solidification, and the bonding strengths were not satisfactory. By increasing the bonding time to 60 min at constant bonding temperature of 580 ºC, the isothermal solidification was completed and the final joint microstructure consisted of soft α-Al phase with dispersed CuAl2 precipitated particles. Decreasing the amount of brittle eutectic structures in the joint seam by increasing the bonding time was the main reason for improvement of the joint shear strength. The maximum joint shear strength was achieved at 580 ºC for 60 min which was about 85% of the shear strength of the base material.
B. Binesh, A. Jazayerigharehbagh, A. R. Foroghi,
Volume 35, Issue 3 (12-2016)
Abstract
In this research, the TLP bonding of IN-738LC superalloy was investigated using MBF-20 amorphous foil produced by melt spinning process. The bonding process was carried out at 1035-1080°C for 30-60 min under the vacuum atmosphere. Microstructural investigations showed that the eutectic phases formed in non-isothermal solidified zone (ASZ) are consised of secondary phase borieds rich in nickel, chromium and nickel silicides. Nickel silicide fine precipitates are formed within γ solid solution via solid state precipitation during cooling. The centerline eutectic phases decreased with increase of the bonding time and decrease of amorphous foil thickness. It was found that isothermal solidification was completed when bonding was done at 1055°C for 30 min. However, the isothermal solidification rate decreased with increasing of the bonding temperature up to 1080°C. Unexpectedly, isothermal solidification rate decreased by increasing the tempretarure to 1080°C. The shear strength increased by completing isothermal solidification stage and eliminating brittle secondary phase particles in the centerline of bonding zone.
M. Jafari, M. Rafiei, H. Mostaan,
Volume 39, Issue 2 (8-2020)
Abstract
In this research, the effect of temperature and time on the properties of AISI420/SAF2507 dissimilar joint produced by transient liquid phase bonding process was investigated. A BNi-2 interlayer with 25 μm thickness was inserted between two dissimilar steel samples. The bonding process was performed at 1050 oC and 1100 oC for different bonding times. The microstructures of the joints were studied using optical microscope, scanning electron microscope and energy dispersive X-ray spectroscopy. Microhardness and tensile shear strength of bonded samples were investigated. Isothermal solidification was completed for the joints bonded at 1050 oC and 1100 oC for 45 min and 30 min, respectively. ASZ and ISZ areas of the bonding zone at the bonding temperature of 1050 oC indicated the highest (520 HV) and the lowest (300 HV) microhardness values, respectively. Sample bonded at 1050 oC for 1 min indicated the lowest tensile strength (196 MPa) and sample bonded at 1100 oC for 60 min indicated the highest tensile strength (517 MPa).
