Showing 11 results for Atapour
B. Sadeghian, M. Atapour, A. Taherizadeh ,
Volume 1, Issue 1 (Journal OF Welding Science and Technology of Iran 2016)
Abstract
Today, steel to aluminum joints are used to facilitate transportation and fuel consumption. These joints are applied from nuclear, aerospace and naval to automobile and kitchen industries. According to previous studies fusion welding processes are not suitable methods for these joints, solid-state welding, especially friction stir welding, is a proper way to use for these joints. However, using this method for these two metals needs adequate prediction of temperature distribution and material flow to obtain enhanced joints. In this study, a finite element method is used to predict the temperature distribution. In addition, a computational fluid dynamics solution is coupled with the thermal solution. Therefore, the flow rate, strain rate and dynamic viscosity is obtained. Also, the joint morphology is predicted using the Level Set method. It is shown the material flow depends on flow rate, strain rate and dynamic viscosity and is intensively function of rotational speed. Additionally, offset to the aluminum side improves the morphology of the stir zone.
A. Behjat, M. Shamanian, M. Atapour, M. Ahl Sarmadi ,
Volume 2, Issue 1 (Journal OF Welding Science and Technology of Iran 2016)
Abstract
High-strength low alloy steels are a class of steels used in applications that require high strength and good weldability, including ship hulls, gas pipelines and oil industry. One way to build parts is fusion welding that create areas with a large grain size in the heat-affected zone and increased susceptibility to hydrogen cracking. One way to solve this problem is to use solid state friction stir welding process. In this study, microstructural evaluation and mechanical properties of friction stir welding X-60 cross sections examined by optical microscope and by tensile and micro-hardness tests. The results indicate that changing welding parameters and thereby, change the heat input during friction stir welding have a great impact on maximum temperature and cooling rate that cause creating ferrite and bainitic ferrite in the weld zone. This change in microstructure of weld zone cause to improve mechanical properties that increase yield strength from 380 MPa to 420 MPa .Also, the friction stir process cause increasing hardness of 220 Vickers to an average of 280 Vickers and uniform distribution of hardness in the cross-section of friction stir joints.
M. Ahl Sarmadi, M. Shamanian, M. Atapour, H. Edris, A. Behjat,
Volume 3, Issue 1 (Journal OF Welding Science and Technology of Iran 2017)
Abstract
In this study, the corrosion behavior of super duplex stainless steel UNS S32750 and tungsten arc welding with filler metals AWS ER2594 duplex stainless steel in acidic solution containing chloride ions have been investigated. Microstructure of weld joints evaluateby light and electron microscope and corrosion behavior examine by open circuit potential and cyclic polarization tests.The results showed that increas in heat input leads to a change in the distribution of alloying elements, formation of intermetallic phases around grain boundaries and the shifting balance between austenite and ferritein phases in weld region. Based on the cyclic polarization tests, cross-weld and base metal active behavior and have good corrosion resistance due to the presence of high alloying elements. As well as increase in heat input leads to an increase in current density and decrease in the pitting potential.
B. Sadeghian, A. Taherizadeh, M. Atapour, T Salehi, M Nosouhian,
Volume 3, Issue 1 (Journal OF Welding Science and Technology of Iran 2017)
Abstract
Aluminum to stainless steel joints are broadly used in industries in order to reduce fuel consumption. While fusion welding is not a suitable method to join these metals. solid state welding, like friction welding (FW), is an effective way to this process. However, risk of intermetallic compounds (IMCs) formation is probable in these welds. In previews investigations formation of FeAl3, Fe2Al5 and Fe4Al13 is reported. In this study, effect of different parameters on generated heat and temperature distribution that lead to formation of these compounds in a FW of aluminum alloy to stainless steel is investigated using Finite Element Method (FEM). Additionally, a mathematical modeling of the parameters is performed using Artificial Neural Network (ANN) and the optimum level of the parameters has been found.
R. Abdolvand, M. Atapour, M. Shamanian, A. Allafchian,
Volume 3, Issue 2 (Journal OF Welding Science and Technology of Iran 2018)
Abstract
Transient liquid phase bonding of UNS S32750 super duplex stainless steel to AISI 304 austenitic stainless steel using BNi-2 interlayer was carried out at 1050 oC for 45 min. Microstructure analyses of the joint were carried out using optical microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Microhardness indentation and shear strength test were performed to assess mechanical behavior of the joint. No eutectic contents was seen at the joint and thus Isothermal solidification was completed at 45 min bonding time. The shear strength of the joint was about 0.7 of duplex stainless steel shear strength. Froctographic studies revealed that the fracture mode was completely ductile in the case of the joint made at bonding time of 45 min.
, M. Ahl Sarmadi, M. Atapour, A. Behjat, H. Edriss, M. Vahman ,
Volume 4, Issue 1 (Journal OF Welding Science and Technology of Iran 2018)
Abstract
Galvanic corrosion is an ever-present problem in all different environments, particularly in tanks. The goal of this project is to develop a finite element model that can be used with experimental data to characterize the corrosion of a galvanic weldments couple in an electrolyte. In this study sample are welded by gas tungsten arc welding and friction stir welding. According to ASTM G8, Evaluation of corrosion properties examined with cyclic polarization test in 0.5 molar H2SO4 andthe information required to validate the model was prepared. The finite element model is developed using COMSOL and Math Module through derivation of equations describing corrosion thermodynamics and electrochemical kinetics. The results showed that reducing in heat input to improve galvanic corrosion behavior in the weld sample.In addition to result of simulation reveal sample that welded by gas tungsten arc method had higher current density galvanic corrosion in comparison with friction stir sample.
M. Chiani, M. Atapour,
Volume 5, Issue 2 ((Journal OF Welding Science and Technology) 2020)
Abstract
In this study, corrosion behavior of Ti-6Al-4V titanium alloy joint by friction stir welding with a rotational speed of 375 rpm and a travel speed of 100 mm/min was investigated. The welding procedure was carried out under β-transus temperature that was consisted of equiaxed grains in the stir zone. The corrosion behavior of the welded joint was investigated in 3.5% NaCl solution at temperatures of 25, 37 and 80 . Microstructure investigation of sample surfaces after electrochemical experiments was conducted using SEM. results revealed that the β phase was mainly corroded at all three testing temperatures, however the corrosion in the sample tested at 80 °C was more considerable.
S. Varmaziar, M. Atapour, Y. Hedberg,
Volume 8, Issue 1 (Journal OF Welding Science and Technology 2022)
Abstract
The influence of filler metals on the microstructure and corrosion behavior of AISI 316L welds was investigated. Gas Tungsten Arc welding (GTAW) process was applied to join the AISI 316L plates using ER 316L and ER 312 filler metals. The obtained microstructures were characterized by optical metallography and scanning electron microscope (SEM). Corrosion assessments were conducted in 3.5% NaCl using a three electrode cell. Open circuit potential and potentiodynamic polarization examinations were conducted on the welds and base metal. Microstructural evaluations indicated that a combination of austenite and ferrite phases was formed in the welds fabricated by both filler metals. Based on the micro hardness tests, the weld fabricated by ER 312 filler exhibited superior harness compared to the ER 316L weld. Corrosion evaluations also show that the weld metal obtained from two filler metals has a lower corrosion rate due to the higher amount of chromium and higher ferrite compared to the base metal. Also, the lower corrosion current of ER 312 weld metal compared to ER 316L weld metal is for this reason. In contrast to the base metal compared to the two welding metals, the result of the two filler metals has shown better pitting corrosion results according to the electrochemical tests and also the examination of the surfaces using an optical microscope after these tests, that these results are due to The presence of two phases of austenite and ferrite in the vicinity of each other in weld metals and the intensification of galvanic corrosion is due to the discharge of the austenite phase from chromium and molybdenum.
Hossein Abedi Chermahini, Mohammad Mahdi Piran, Ali Akbar Esmaeili Chamgordani, Masoud Atapour,
Volume 9, Issue 2 (Journal OF Welding Science and Technology 2024)
Abstract
In this research, the mechanical properties and microstructure of L316 grade stainless steel sheets welded using the resistance spot welding method with a copper interlayer were investigated. In this regard, two types Connection were considered: one without the interlayer and the other with the copper interlayer, connected at different currents. To select the optimal current for both types of connections, tensile tests were initially conducted. Following that, microstructural examinations, microhardness tests, elemental evaluations, and failure mode analyses were performed on the optimized samples. according to the results obtained, increasing the electric current raised the input heat in the weld pool to an appropriate level, improving the microstructural and mechanical properties of the weld region. Additionally, due to the optimal electric current in both samples "with and without" the interlayer, both samples experienced interfacial failure, indicating high strength at their joint and weld points. Changes in chemical composition across different weld areas were minimal, and element distribution was reported to be uniform throughout all regions. The highest hardness was observed from the base metal towards the center of the weld in the order of weld area > base metal > heat-affected zone, which corresponded with results from microstructural examinations.
Hossein Abedi Chermahini, Masoud Atapour, Mojtaba Esmail Zadeh,
Volume 9, Issue 2 (Journal OF Welding Science and Technology 2024)
Abstract
Nowadays, to achieve the simultaneous properties of multiple alloys in important applications such as automotive and aerospace, the use of surface coating methods is common. Coating through welding (cladding) is one of the widely used methods for surface modification of metal parts and sheets in the industry. Low-alloy steel AH36 is one of the steels used in shipbuilding, known for its toughness and good corrosion resistance, gaining significant recognition among other steels used in this industry. In this research, to improve the corrosion properties of this steel, the cladding process was performed using Gas Tungsten Arc Welding (GTAW) with copper/nickel filler wire. Two samples from coated and uncoated sections, termed base metal and weld metal, were prepared and subjected to microstructural and corrosion investigations. The results indicated an increase in grain size in the heat-affected zone of the weld metal sample, leading to a reduction in mechanical properties. The pitting potential for both base and weld metals was reported as -1.7 V and -0.5 V, respectively, indicating a greater capability of the weld metal for pitting repair in case of stable pit formation. The presence of only a single semicircle in the Nyquist plot indicates a single-loop equivalent circuit and confirms the absence of a passive layer. Additionally, resistance to pitting and charge transfer resistance was reported to be higher in the base metal compared to the weld metal
A. R. Nazari , A. Taherizadeh, M. Atapour,
Volume 10, Issue 1 (Journal OF Welding Science and Technology 2024)
Abstract
In this study, the microstructure and mechanical properties of dissimilar resistance spot welding of AISI 430 steel and S500 MC steel were investigated. To carry out this research, Taguchi's L9 array was used to determine the number of samples and determine the range of variables of each sample, and after welding the samples and performing the shear tensile test, the sample with the highest tensile shear strength (13740 N) and the highest amount of fracture energy (102160 Joules), was considered as the best example; Also, the variables of this sample, i.e., welding current of 12 kW, welding time of 12 cycles, and electrode force of 3 kN, had the highest signal-to-noise values, and these values were chosen among the best range of variables among the proposed variables. Then, a microhardness test was performed on the welded sample with the above variables, and microstructural studies were performed by optical microscope and scanning electron microscope. The hardness of the weld zone was observed to be about 400 Vickers, and the microstructure of the weld metal consisted of ferrite, martensite, and Widmannstatten ferrite.
