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The optimum combination of tool rotation rate and traveling speed for obtaining the preferable corrosion behavior and mechanical properties of friction stir welded AA5052 aluminum alloy
, Article Materials and Design ; Volume 50 , 2013 , Pages 620-634 ; 02613069 (ISSN) ; Gholami Shiri, S ; Yaghoubinezhad, Y ; Mohammadi Rahvard, M ; Sharif University of Technology
Elsevier Ltd
2013
Abstract
This study attempts to find an optimum combination of the welding tool rotation rate (ω) and traveling speed (υ), concerning the corrosion and mechanical properties of Friction Stir Welded (FSWed) AA5052 Aluminum alloy. The effect of the tool speeds on the FSWed AA5052 are investigated via potentiodynamic polarization, open circuit potential (OCP) monitoring, test of the susceptibility to intergranular corrosion, weight loss, tension and micro-hardness tests. Optical microscope and Scanning Electron Microscopy (SEM) were employed for studying the morphology and analyzing the probable intergranular attacks. It was found that by increasing υ up to 200. mm/min at ω=400 rpm, the microstructural...
"investigation on the Effects of Number of Rows in SMAW on Properties of Stainless Steel Clad with Carbon Steel Base Metal and Optimizing Properties of the Clad"
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor) ; Dolati, Abolghasem (Supervisor)
Abstract
Dilution is a parameter with significant effects in SMAW process. As this factor is in a range of 25-35% in SMAW process, it can increase the portion of base metal in the weld metal. During cladding carbon steel by stainless steel, this parameter causes reaching different composition as the number of weld rows increases. The aim of this project firstly is to investigate the effects of this parameter and then achieving the same properties in different welding rows. Suggested electrodes are as follows; E316-L16 three-row, KST 309-L16 for two-row and KST 310-16 for one-row welds. Corrosion behavior of each clad have been studied and the results show that; although by changing the electrodes the...
Impact of phase transformation on mechanical properties anisotropy of commercially pure titanium
, Article Materials and Design ; Volume 37 , 2012 , Pages 223-227 ; 02641275 (ISSN) ; Ekrami, A ; Ziaei Moayyed, A. A ; Sharif University of Technology
Abstract
Effects of microstructure and texture, before and after phase transformation, on the anisotropy of the mechanical properties and fracture behaviors of commercially pure titanium were studied. Before phase transformation, due to the split distribution of basal texture the activation of different deformation systems led to mechanical properties anisotropy. Although the fracture mechanism in both specimens was voids nucleation, growth and coalescence, the shape, size and distribution of dimples were affected by active deformation systems. However, after phase transformation, basal plains in most grains were aligned with the transverse direction. This texture component led to the activation and...
The effects of MM38.2Co46.4Ni15.4 alloy additions on the mechanical properties of a Nd12.8Fe 79.8B7.4-type sintered magnet
, Article Materials Letters ; Volume 60, Issue 4 , 2006 , Pages 555-558 ; 0167577X (ISSN) ; Kianvash, A ; Sharif University of Technology
2006
Abstract
The mechanical properties of the Nd-Fe-B-based alloys are closely related to their microstructures. It was found that the Co and Ni additions to the Nd2Fe14B (Φ) matrix phase and reduction in the amounts of rare earth (RE)-rich (n) and B-rich (η) grain boundary phases are very effective in improving the mechanical properties. The addition of a MM 38.1(MM: Misch Metal)-Co46.4-Ni15.5 alloy to a ternary Nd12.8Fe79.8B7.4-type alloy by a binary powder blending technique resulted in a considerable increase in bending and compressive strength, and a significant decrease in impact strength. The solid solution hardening of the matrix phase by Co and Ni and the presence of intergranular cracks within...
Effect of sintering temperature and siliconcarbide fraction on density, mechanical properties and fracture mode of alumina-silicon carbide micro/nanocomposites
, Article Materials and Design ; Volume 37 , May , 2012 , Pages 251-255 ; 02641275 (ISSN) ; Baharvandi, H ; Abdizadeh, H ; Purasad, J ; Fathi, A ; Ahmadi, H ; Sharif University of Technology
2012
Abstract
In this study Al2O3-SiC micro/nanocomposites have been fabricated by mixing alumina nanopowders and silicon carbide micro/nanopowders, followed by hot pressing at 1550, 1600, 1650 and 1700°C. The density, mechanical properties and fracture mode of Al2O3-SiC composites containing different volume fractions (2.5%, 5%, 7.5%, 10% and 15%) of micro/nanoscale SiC particles were investigated and compared with those of alumina. The relative density of composites could reach values very close to theoretical density, especially after sintering at 1700°C. However, relative density declined by increasing the SiC fraction at the same sintering temperature. The flexural strength of composites was best for...
Hot tensile properties and microstructural evolution of as cast NiTi and NiTiCu shape memory alloys
, Article Materials and Design ; Volume 32, Issue 1 , January , 2011 , Pages 406-413 ; 02641275 (ISSN) ; Aboutalebi, M ; Kheirandish, S ; Taheri, A. K ; Abbasi, S. M ; Sharif University of Technology
2011
Abstract
Hot tensile properties of as cast NiTi and NiTiCu shape memory alloys were investigated by hot tensile test at temperature range of 700-1100°C using the strain rate of 0.1s-1. The NiTi alloy exhibited a maximum hot ductility at temperature range of 750-1000°C, while the NiTiCu alloy showed it at temperature range of 800-1000°C. It was found that at temperatures less than 750°C, diffusion-assisted deformation mechanism was inactive leading to semi-brittle type of failure and limited ductility in both alloys. Also it was found that at temperature range of 800-1000°C, dynamic recrystallization is dominant leading to high ductility. Likewise, the fracture surface of the specimens presenting the...
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...
A comprehensive evaluation between the efficiency of different treatments in modifying the properties and behavior of magnesium alloys as degradable biomaterials
, Article Materials and Corrosion ; Volume 68, Issue 9 , 2017 , Pages 995-1003 ; 09475117 (ISSN) ; Afshar, A ; Sharif University of Technology
Abstract
The addition of alloying elements to magnesium leads to microstructural refinement and improves its properties. However, this strategy is accompanied by another concurrent phenomenon − that is − intergranular segregation and the formation of secondary phases in grain boundaries, deteriorating the properties. In this work, the efficacy of two main factors on modifying the mechanical properties and corrosion behavior of Mg-4Zn-1Al-0.2Ca alloy was investigated separately: 1) dissolution of secondary phases; and 2) grain refinement. Based on the results, heat treatment of the as-cast alloy can increase the UTS from 174.4 to 213.2 MPa, decrease the corrosion current density from 81 to 49 μA/cm2,...
Investigating the solid-state diffusion at the interface of Ni/Ti laminated composite
, Article Journal of Manufacturing Processes ; Volume 75 , 2022 , Pages 670-681 ; 15266125 (ISSN) ; Yarigarravesh, M ; Assari, A. H ; Amin, N. H ; Tayyebi, M ; Paidar, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The fabrication of Ni/Ti laminated composite via cross accumulative roll bonding (CARB) and subsequent annealing treatment has been studied. The relationships between annealing conditions and microstructure at interfaces of Ni/Ti have been investigated by SEM, XRD, and EDS analyses. The results show that the layers were well-bonded by the CARB process, and by increasing the temperature and time of annealing treatment, the interfacial layers grew as a result of the interdiffusion of Ni and Ti atoms. The main intermetallic phases were NiTi and NiTi2, both of which obeyed linear kinetics of growth. However, the calculated activation energy of NiTi was lower than that of NiTi2, indicating the...
Co-sintering of M2/17-4PH powders for fabrication of functional graded composite layers
, Article Journal of Composite Materials ; Volume 44, Issue 4 , 2010 , Pages 417-435 ; 00219983 (ISSN) ; Simchi, A ; Sharif University of Technology
2010
Abstract
Stepwise-graded composite layer of M2 tool stel and 17-4PH stainless steel was fabricated by a simple powder layering technique and the isothermal and nonisothermal sintering response of the bilayer were examined. It was shown that the materials exhibit poor compatibility during co-sintering, i.e., the amount of mismatch shrinkage is significant. An improved compatibility was obtained by adding 0.2 wt% B to the stainless steel powder. Formation of relatively dense layer at the bonding zone indicated an enhanced densification rate at the interface. Microstructural studies showed formation of a ferritic interface in M2/17-4PH composite and elongated grains with an intergranular boride phase...