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An Investigation into the Effect of Solidification Rates and Melt Filtration on the Tensile Properties of A356 Castings
, M.Sc. Thesis Sharif University of Technology ; Varahram, Naser (Supervisor) ; Davami, Parviz (Supervisor)
Abstract
A356 castings show different characteristics during tensile tests. This behavior emanates from casting defects such as pores and double oxide films. These defects lead to quick and unexpected failure during tensile tests. Secondary dendrite arm spacing of primary α phase, eutectic phase, volume fraction of pores and oxide films are the characteristics that affect the tensile property. N this study the effect of changing two characteristics on the microstructural constituents is investigated. The first one is cooling rates, and the second one is melt filtration by using different filter in the runner. According to the tensile properties, the effect of these changes on tensile properties...
Solidification of Fluid Inside the Pipeline to Fix or Replace the Defective Component
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Hassan (Supervisor)
Abstract
Pipe freezing has become well established in industry as a method of short-termisolation in order to carry out maintenance or repairs. It is often necessary to repair system components without plant shutdown or drainage of system having many piping structures which may have hazardous or expensive fluid. Therefore, a series of tests has been arranged to investigate the ice plug formation in two standard pipes with different diameter size. The freeze zone on the pipe has been created by means of an aluminum jacket which liquid nitrogen flows in it. In the tests the freezing time, amount of liquid nitrogen usage andthe pressure tolerance of ice plug have been determined. Moreover, the numerical...
A comprehensive study on the complete charging-discharging cycle of a phase change material using intermediate boiling fluid to control energy flow
, Article Journal of Energy Storage ; Volume 35 , 2021 ; 2352152X (ISSN) ; Mohammadi, O ; Faghiri, S ; Shafii, M. B ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The low melting and solidification rates of phase change materials (PCM), which traces back to their low thermal conductivity coefficient, has led the application of these materials to face limitations. This paper aims to explore the effectiveness of a novel method called intermediate boiling fluid (IBF) in speeding up the energy storage and transfer processes in PCMs during a complete charging-discharging cycle. Throughout this novel technique, paraffin and acetone are utilized as PCM and IBF, respectively. In the solidification process, there is no direct contact between the cold source and the molten paraffin, while acetone, as an intermediate fluid, is being boiled via absorbing...
Investigation on the Effect of Cooling Rate on the Solidification Behavior and Microstructure of Al 713 alloy using Thermal Analysis Technique
, M.Sc. Thesis Sharif University of Technology ; Varahram, Nasser (Supervisor)
Abstract
Considering the limited number of works on investigation of solidification characteristics of Al-Zn-Mg-Cu cast alloys as well as the applications of this alloy system in aerospace industries, the solidification conditions of Al 713 alloy were investigated in this study. In order to achieve this goal, a number of experiments were designed and conducted including quantometry, thermal analysis, metallography and hardness measurements. In this thesis, effects of cooling rate on secondary dendritic arms spacing as well as solidification parameters including nucleation temperature, solidification time and temperature range, dendrite coherency point and formation temperature of intermetallic...
Conventional vs. temperature-gradient transient liquid phase bonding of stainless steel 304 using a multi-component (Fe–Ni–Mo–B) filler metal
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 53, Issue 11 , 2022 , Pages 4081-4100 ; 10735623 (ISSN) ; Ekrami, A ; Sharif University of Technology
Springer
2022
Abstract
The application of the multi-component Fe-based filler metals (FMs) for transient liquid phase (TLP) bonding of AISI 304 austenitic stainless steel has been overshadowed by dissimilar interlayers merely due to their shorter isothermal solidification time. However, the latter usually suffers from low efficiency in terms of mechanical properties even after homogenization of heat treatment. This study shows that by imposing a temperature gradient across the bond line during the TLP bonding process (TG-TLP), it is possible to reduce the isothermal solidification time significantly. This renews the interest in utilizing multi-component Fe-based FMs. In this regard, the TG-TLP bonding process was...
On the inability of the moving interface model to predict isothermal solidification time during transient liquid phase (TLP) bonding of ni-based superalloys
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 53, Issue 1 , 2022 , Pages 126-135 ; 10735623 (ISSN) ; Ghasemi, A ; Salmasi, A ; Sharif University of Technology
Springer
2022
Abstract
Understanding diffusion-induced isothermal solidification time during transient liquid phase bonding is vital in producing intermetallic-free robust joints. The isothermal solidification completion time is overestimated by the existing analytical models, even by the closest one to the real bonding conditions, known as the moving interface model. It was found that the boride formation in the diffusion affected zone of Ni-based superalloy upon using B-containing filler metals is one of the reasons behind the inability of the moving interface model to predict the isothermal solidification completion time accurately, which has received scant attention in the literature. Moreover, simplified...
Super-fast discharge of phase change materials by using an intermediate boiling fluid
, Article International Communications in Heat and Mass Transfer ; Volume 115 , 2020 ; Mohammadi, O ; Rahgozar, I ; Shafii, M. B ; Ahmadi, M. H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The low thermal conductivity of phase change materials (PCM) results in the slowdown in the discharging process of PCM which limits the usability of these materials in the field of Thermal Energy Storage (TES). In this research, an innovative solution is proposed to significantly accelerate the solidification speed, up to two orders of magnitude greater than conventional methods. Using acetone as the intermediate boiling fluid (IBF), the paraffin discharge rate as a phase-change material is significantly improved which is known as super-fast discharge (SFD) in this article. In this method, liquid acetone takes the heat by boiling in liquid paraffin and causes it to solidify. As the liquid...
The impact of employing carbon nanotube and Fe3O4 nanoparticles along with intermediate boiling fluid to improve the discharge rate of phase change material
, Article Applied Thermal Engineering ; Volume 215 , 2022 ; 13594311 (ISSN) ; Rahgozar Abadi, I ; Mohammadi, O ; Khademi, A ; Behshad Shafii, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Despite the fact that solid–liquid phase change materials (PCMs) have various applications in thermal energy storage systems, the low solidification rate of PCMs, which is due to the low thermal conductivity has limited the range of applications of PCMs. One of the methods of increasing the solidification rate of PCMs is using a boiling fluid as an intermediary between the solid–liquid PCM and the condenser to prevent the direct contact between the phase change material and the condenser tubes, this method is also known as the intermediate boiling fluid (IBF) method. The IBF method has been shown to significantly increase the solidification rate (2 orders of magnitude). In this study, the...