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Investigation on the Effect of Friction Stir Processing on the Fusion Weldability of Magnesium Alloys
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor) ; Movahedi, Mojtaba (Supervisor)
Abstract
Magnesium alloys, as the lightest structural alloys having a density of about one-fourth that of steels, offer significant potential for improving the energy efficiency of various transportation systems. Welding is a critical enabling manufacturing technology; therefore, the widespread application of a material is highly influenced by their weldability. Liquation and Liquation cracking are crucial weldability issues for fusion welding of cast AZ91 Mg alloy. The constitutional liquation of the coarse eutectic Mg17Al12 intermetallic phase is responsible for the occurrence of liquation cracking during fusion welding of this alloy. Here, friction stir processing (FSP) treatment, a successful...
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)...
Investigation of Hot Cracking Phenomena in Fusion Welding of High-Strength Aluminum Alloys and the Effect of Friction Stir Processing (FSP) Pre-Treatment on the Weldability of 7075 Aluminum Alloy
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor) ; Movahedi, Mojtaba (Supervisor)
Abstract
High-strength aluminum alloys are widely used in various industries; however, their usage is limited to solid-state welding or mechanical joints due to their low weldability. The main metallurgical challenge of alloy 7075 welding is hot cracking. Thus, the mentioned alloy is introduced as a "non-weldable alloys" category. In this study, the PMZ was investigated, and it was shown that precipitations play an essential role in intensifying the phenomenon of partial melting. On the other hand, the result of the mechanisms activated in the PMZ, called the "L" region, occurs in the grain boundaries during welding. Welded plate with FM1050 causes liquation cracking, while Welded plate with FM4043...
Critical review on fusion welding of magnesium alloys: metallurgical challenges and opportunities
, Article Science and Technology of Welding and Joining ; Volume 26, Issue 8 , 2021 , Pages 559-580 ; 13621718 (ISSN) ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
As the lightest structural alloys, magnesium alloys offer significant potential for improving the energy efficiency of various transportation systems. The lack of sufficient weldability of Mg alloys is a crucial barrier to their potential use in safety-critical applications. Porosity formation, grain structure engineering, solidification cracking, liquation, and liquation cracking are the key metallurgical challenges to obtain reliable and robust fusion welds in Mg alloys. This critical review highlights the current understating regarding controlling the metallurgical phenomena during fusion welding of Mg alloys and discusses the unresolved metallurgical challenges to shed light on the path...
An investigation into welding of 304 stainless steel to a medium carbon steel
, Article Welding in the World ; Volume 53, Issue SPECIAL ISSUE , 2009 , Pages 575-580 ; 00432288 (ISSN) ; Nasiri, A. M ; Kokabi, A. H ; Serajzadeh, S ; Sharif University of Technology
Abstract
In this work, fusion welding of CK45 carbon steel and 304 stainless steel was performed using GTAW technique. Both ER308-L and ERNi-1 filler metals with and without buttering conditions were employed. Then, the welded samples were studied utilizing optical metallography, scanning electron microscopy, microhardness, polarization and impact tests. It is observed that in the buttered specimens with nickel wire, the structure of weld metal was completely austenitic while the microstructure of unbuttered one was austenitic-ferritic and also, a carburized region in the weld metal next to the fusion line were observed. Microstructures and microhardness variation in the weld metal after socking at...
Microstructure-performance relationships in gas tungsten arc welded Hastelloy X nickel-based superalloy
, Article Materials Science and Engineering A ; Volume 793 , 2020 ; Kolagar, A. M ; Pouranvari, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
This study aims at understanding the metallurgical and mechanical response of Hastelloy X nickel-based superalloy to the thermal cycle of gas tungsten arc welding (GTAW), post welding solution treatment (ST), and aging. In the as-weld condition, the weldment was characterized by the formation of the M6C carbide, sigma phase, and micro-solidification cracks in the interdendritic zones of the weld metal, and constitutional liquation of M6C carbide in the heat-affected zone. It is demonstrated that neither the weld metal nor the heat-affected zone could adversely affect mechanical properties of the welded joint in as-weld condition. However, to alleviate the microstructural heterogeneity,...