Search for: austenite
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    A mathematical model for prediction of austenite phase transformation

    , Article Materials Letters ; Volume 58, Issue 10 , 2004 , Pages 1597-1601 ; 0167577X (ISSN) Serajzadeh, S ; Sharif University of Technology
    In this study, a model is developed to predict austenite phase transformation by means of Avrami's model and the finite element method. For doing so, the Avrami-type rate equation is evaluated with the modified Euler's method to handle the kinetics of phase change under non-isothermal conditions. Also, to simultaneously consider the effect of temperature variations on austenite decomposition, heat conduction equation is solved using a two-dimensional finite element approach. To establish the reliability of theoretical results, a comparison is made between simulated and experimental cooling curves for two grades of carbon steel. © 2003 Elsevier B.V. All rights reserved  

    Modelling of temperature history and phase transformations during cooling of steel

    , Article Journal of Materials Processing Technology ; Volume 146, Issue 3 , 2004 , Pages 311-317 ; 09240136 (ISSN) Serajzadeh, S ; Sharif University of Technology
    A mathematical model based on the finite element method and additivity rule has been developed to predict temperature history and microstructural changes during cooling of steel. The utilized model considers the effects of various factors including initial austenite grain size and its role on the kinetics of pearlite and ferrite transformations, amount of residual strain within the cooling material, heat of transformation and variation of thermo-physical properties of the steel during cooling. The model can be employed as a guideline to design new cooling programs for achieving the desired microstructure and mechanical properties. To verify the results of the modelling, time-temperature... 

    An investigation of the silicon role on austenite recrystallization

    , Article Materials Letters ; Volume 56, Issue 6 , 2002 , Pages 984-989 ; 0167577X (ISSN) Serajzadeh, S ; Karimi Taheri, A ; Sharif University of Technology
    The role of silicon on austenite recrystallization was investigated using hot compression experiments on a low carbon and a high silicon steel samples. The models were proposed to describe the hot deformation behavior of metals regarding dynamic recovery. The rate of static recrystallization was found lower in the silicon steel in comparison with low carbon steel. Silicon was found to produce a lower rate of dynamic recovery due to its effect on the austenite staking fault energy  

    Effect of intercritical annealing on retained austenite characterization in textured TRIP-assisted steel sheet

    , Article Materials Characterization ; Volume 57, Issue 4-5 , 2006 , Pages 408-413 ; 10445803 (ISSN) Emadoddin, E ; Akbarzadeh, A ; Daneshi, Gh ; Sharif University of Technology
    Optimization of high strength and high formability of multiphase cold rolled sheet TRIP-aided steels is based on the composition and the austempering conditions. The effect of intercritical annealing temperature on the volume fraction and carbon concentration of the retained austenite was investigated in two different TRIP-aided steels. Experimental results show that the optimum annealing temperatures are 860 °C for Al-containing and 810 °C for Si-containing TRIP steels. It was demonstrated that the measurement of retained austenite can be successfully performed for textured TRIP steels by XRD. © 2006 Elsevier Inc. All rights reserved  

    A study on austenite decomposition during continuous cooling of a low carbon steel

    , Article Materials and Design ; Volume 25, Issue 8 , 2004 , Pages 673-679 ; 02613069 (ISSN) Serajzadeh, S ; Karimi Taheri, A ; Sharif University of Technology
    Elsevier Ltd  2004
    In this work, a model based on the finite element method and assumption of second order phase transformation has been developed to predict temperature history and austenite decomposition kinetics during continuous cooling of a low carbon steel. In order to accurately assess the temperature field and transformation rate the effects of various factors such as work hardening role on the kinetics of transformation, interconnection between austenite phase change and thermo-physical properties of the steel, and initial austenite grain size have been considered in the model. To verify the results of the modelling, time-temperature histories during cooling of a low carbon steel has been determined... 

    Prediction of temperature distribution and phase transformation on the run-out table in the process of hot strip rolling

    , Article Applied Mathematical Modelling ; Volume 27, Issue 11 , 2003 , Pages 861-875 ; 0307904X (ISSN) Serajzadeh, S ; Sharif University of Technology
    Elsevier Inc  2003
    In this paper a mathematical model based on the finite element method and the Scheil additivity rule is presented for predicting the temperature distribution and phase transformation behavior on the run-out table during the hot strip rolling of a low carbon steel. The model considers the austenite to ferrite and pearlite transformations, the temperature-dependent material properties of the cooling austenite as well as the austenite work hardening effect on the kinetics of austenite transformation. To determine the validity of the model predictions, the time-temperature histories of a low carbon steel rod in different cooling media were measured and also hot rolling experiments were... 

    Correlation between Luder strain and retained austenite in TRIP-assisted cold rolled steel sheets

    , Article Materials Science and Engineering A ; Volume 447, Issue 1-2 , 2007 , Pages 174-179 ; 09215093 (ISSN) Emadoddin, E ; Akbarzadeh, A ; Daneshi, G. H ; Sharif University of Technology
    In developed multiphase high strength, high formability TRIP-aided steel, Luders bands are observed similar to conventional low carbon steels. Retained austenite as the most effective constituent in TRIP steels, is responsible for Luders band formation as well as other properties such as formability, physical and mechanical properties. In the present study, a correlation between the Luders strain and the retained austenite characterization is proposed and verified by experimental evidences of the work carried out on two types of TRIP steel sheets. Intercritical annealing of cold rolled TRIP steels at different temperatures change the volume fraction of the retained austenite as well as the... 

    Investigation of the effect of tungsten substitution on microstructure and abrasive wear performance of in situ vc-reinforced high-manganese austenitic steel matrix composite

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 44, Issue 8 , 2013 , Pages 3826-3835 ; 10735623 (ISSN) Moghaddam, E.G ; Karimzadeh, N ; Varahram, N ; Davami, P ; Sharif University of Technology
    Particulate VC-reinforced high-manganese austenitic steel matrix composites with different vanadium and tungsten contents were synthesized by conventional alloying and casting route. Microstructural characterizations showed that the composites processed by in situ precipitation of the reinforcements were composed of V8C7 particulates distributed in an austenitic matrix. It was observed that addition of tungsten to austenite increases work-hardening rate of subsurface layer during pin-on disk wear test. The maximum abrasive wear resistance was achieved at tungsten content equal to 2 wt pct. However, excessive addition of tungsten promoted the formation of W 3C phase and reduced the abrasive... 

    Anisotropy of retained austenite stability during transformation to martensite in a TRIP-assisted steel

    , Article Steel Research International ; Volume 84, Issue 3 , 2013 , Pages 297-303 ; 16113683 (ISSN) Emadoddin, E ; Akbarzadeh, A ; Petrov, R ; Zhao, L ; Sharif University of Technology
    Retained austenite as a key constituent in final microstructure plays an important role in TRansformation Induced Plasticity (TRIP) steels. The volume fraction, carbon concentration, size, and morphology of this phase are the well-known parameters which effects on the rate of transformation of retained austenite to martensite and the properties of steel, are studied by many researchers. Of the transformation of retained austenite to martensite under strain in a TRIP steel is studied in this paper. The experimental results show that the transformation rate of retained, austenite with similar characteristics, to martensite in differently processed TRIP steel samples, exhibits an anisotropic... 

    Damage development during the strain induced phase transformation of austenitic stainless steels at low temperatures

    , Article Modelling and Simulation in Materials Science and Engineering ; Volume 29, Issue 4 , 2021 ; 09650393 (ISSN) Homayounfard, M ; Ganjiani, M ; Sasani, F ; Sharif University of Technology
    IOP Publishing Ltd  2021
    The strain-induced martensitic transformation greatly affects the plastic behavior of the metastable austenitic stainless steels. The martensitic transformation continuously changes the initially homogeneous material into a strongly heterogeneous bi-phase one. In addition to the hardening behavior, this phenomenon would influence the damage growth and load-carrying capacity of the material during the plastic deformation. In this study, plastic behavior of the material AISI 304 including the hardening and damage growth, has been examined at low temperature; where a high rate of martensitic transformation affects the microstructure strongly. Experimental analysis and microscopic observations... 

    Prediction of temperature variations and kinetics of austenite phase change on the run-out table

    , Article Materials Science and Engineering A ; Volume 421, Issue 1-2 , 2006 , Pages 260-267 ; 09215093 (ISSN) Serajzadeh, S ; Sharif University of Technology
    In this paper, a mathematical model has been developed to determine temperature distribution on the run-out table. The variational formulation and the finite element method have been employed to solve the governing conduction-convection equation. In order to avoid numerical instabilities due to the convection term, the heat transfer equation is first transformed to the standard form and then Raylieght-Ritz approximation technique and the finite element method have been utilized to solve the equation. To include the effect of phase transformation during cooling of steel, a second-order rate equation for describing austenite decomposition kinetics is coupled with the heat transfer model. A... 

    On the comparison of microstructural characteristics and mechanical properties of high-vanadium austenitic manganese steels with the Hadfield steel

    , Article Materials Science and Engineering A ; Volume 532 , 2012 , Pages 260-266 ; 09215093 (ISSN) Moghaddam, E. G ; Varahram, N ; Davami, P ; Sharif University of Technology
    In this study, high-vanadium austenitic manganese steel (HV-AMS) alloys and the standard Hadfield steel were investigated. The microstructure of these high-vanadium alloyed Hadfield steels was studied thoroughly using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) and was compared to the Hadfield steel. The hardness and unnotched Charpy impact strength of HV-AMS alloys and Hadfield steel were examined at ambient temperature in the as-cast and heat-treated conditions. A pin-on-disk wear test at linear speed of 10. m/min and a 55. N normal load was employed to evaluate the wear behavior of both steel samples. Microstructural results showed that varying... 

    Ferritic-austenitic stainless steels dissimilar resistance spot welds: Metallurgical and failure characteristics

    , Article Science and Technology of Welding and Joining ; Volume 21, Issue 6 , 2016 , Pages 438-445 ; 13621718 (ISSN) Pouranvari, M ; Khorramifar, M ; Hoveida Marashi, S. P ; Sharif University of Technology
    Taylor and Francis Ltd  2016
    The paper addresses the microstructure and failure characteristics of dissimilar resistance spot welds between austenitic stainless steel and ferritic stainless steel. The fusion zone (FZ) of dissimilar welds exhibited complex microstructure consisting of ferrite, austenite and martensite. The development of this triplex structure in the FZ was explained by analysing the phase transformation path and austenite stability. Results showed that all dissimilar welds failed in partial thickness-partial pull-out failure mode. It was shown that the fraction of the nugget fracture of the weld is reduced by increasing the FZ size improving the mechanical performance of the weld. Peak load and energy... 

    Simulation of recrystallization and martensite revision in 304L austenitic stainless steel after multi-pass rolling processes

    , Article Multiscale and Multidisciplinary Modeling, Experiments and Design ; Volume 3, Issue 4 , 2020 , Pages 227-244 Alavi, P ; Serajzadeh, S ; Sharif University of Technology
    Springer Science and Business Media B.V  2020
    In this work, non-isothermal annealing of cold-rolled 304L austenitic stainless steel was studied at temperatures ranging between 400 and 800 °C. In the first place, a dual-phase structure containing work-hardened austenite and strain-induced martensite was produced by means of multi-pass plate rolling, and then, the deformed steel was subjected to annealing heat treatments. To determine the distribution of stored strain energy in the rolling operations, an elastic–plastic finite-element modeling was conducted. Afterwards, an artificial neural network technique was coupled with the thermal-cellular automata model for prediction of martensite reversion, temperature history, and... 

    Effect of rolling strain on transformation induced plasticity of austenite to martensite in a high-alloy austenitic steel

    , Article Journal of Materials Processing Technology ; Volume 203, Issue 1-3 , 2008 , Pages 349-354 ; 09240136 (ISSN) Bigdeli Karimi, M ; Arabi, H ; Khosravani, A ; Samei, J ; Sharif University of Technology
    Current studies show a growing interest on transformation induced plasticity (TRIP) in austenitic steels. Most researches are based on inducing plasticity via tensile stresses, so it seems interesting to accomplish these researches by compressive stresses. Rolling process is a suitable choice to make compressive stresses. In present work, the effects of a wide range of rolling strains (5%-60%) at 0 and 24 °C on the austenite to martensite transformation were investigated on high-alloy austenitic steel. For this purpose, XRD, hardness test and magnetic measurements were used. Results show that by increasing the amount of rolling strain, transformation of austenite to martensite generally... 

    Effect of Cryogenic Treatment on Distribution of Residual Stress and Wear Resistance of AISI 316 and AISI 304 Stainless Steel

    , M.Sc. Thesis Sharif University of Technology Sarkarde, Rezvan (Author) ; Farrahi, Gholamhossein (Supervisor)
    Various methods are used to improve the behavior of steel parts. Cryogenic treatment is one of the prevalent methods used for this purpose. It is not a substitute process but rather a supplement to conventional heat treatment process. In this Study the effect of the minimum temperature and the time of cryogenic treatment on wear resistance and residual stress of stainless steel AISI 316 and AISI 304 were studied. For this purpose conventional heat treatment, deep cryogenic treatment (24, 48 and 72 hours) and shallow cryogenic treatment (5, 10 and 15 hours) were performed on the samples. The wear resistance were measured by Pin-on-disk test according to the standard G99-95 (under the load of... 

    Deformation Behavior and Effect of Strain Path on Strain-Induced Martensite Transformation in Austenitic Stainless Steel

    , M.Sc. Thesis Sharif University of Technology Lotfinia, Mahshad (Author) ; Serajzadeh, Siamak (Supervisor)
    In some of the austenitic stainless steels, the strain-induced martensite transformation occurs during the deformation processing owing to instability of austenite phase at low temperatures. In this study, formation of strain-induced martensite as well as the impact of strain path on the rate of martensite transformation in 316L austenitic stainless steel were investigated. At first, the multi-pass cold rolling experiments at room temperature and -8 ℃ were conducted in which both direct and reverse rolling layouts were taken into account. Then, as the third path, the uni-axial tensile loading with an appropriate strain rate was considered. After that, in order to examine the mechanical and... 

    An Investigation on Multistage Strain Aging Using Rolling Process on Mechanical and Formability of Stainless Steel 304L

    , M.Sc. Thesis Sharif University of Technology Mousavinia, Ali (Author) ; Karimi Taheri, Ali (Supervisor) ; Akbarzadeh Changiz, Abbas (Supervisor)
    Austenitic stainless steels have extensive and special mechanical properties because of austenite to α΄-martensite transformation due to plastic work. Obtaining a process path that provides maximum strength and flexibility and minimum α΄-martensite content (α΄-martensite increases corrosion current) in these steels is important in the industry. Applying the aging process after applying plastic strain (single-stage aging) results in an increase in strength of up to 200 MPa and an increase in hardness of up to 60 Vickers. However, single-stage aging does not cause significant changes in the amount of α΄-martensite in steel and in the temperature range of 400 to 500 ° C, it causes a slight... 

    The effect of gas mixture of post-oxidation on structure and corrosion behavior of plasma nitrided AISI 316 stainless steel

    , Article Applied Surface Science ; Volume 283 , 2013 , Pages 584-589 ; 01694332 (ISSN) Karimzadeh, N ; Moghaddam, E. G ; Mirjani, M ; Raeissi, K ; Sharif University of Technology
    In this research, microstructure and corrosion properties of plasma nitriding and post-oxidation treated AISI 316 austenitic stainless steel have been studied. The plasma nitriding treatment was carried out at 450 C for 5 h in a D.C. plasma setup with a gas mixture of 25% N2-75% H2 followed by post-oxidation in gas mixtures of O2/H2: 1/3, 1/5, 1/9 and 1/12 for 30 min. The treated samples were characterized by SEM, XRD and roughness testing. Potentiodynamic and cyclic polarization tests were also employed to evaluate the corrosion resistance of the samples. The results showed that plasma nitriding treatment decreases corrosion resistance of the steel substrate. However, post-oxidizing... 

    Modeling of austenite to ferrite transformation

    , Article Bulletin of Materials Science ; Volume 35, Issue 3 , 2012 , Pages 395-398 ; 02504707 (ISSN) Kazeminezhad, M ; Sharif University of Technology
    In this research, an algorithm based on the Q-state Potts model is presented for modeling the austenite to ferrite transformation. In the algorithm, it is possible to exactly track boundary migration of the phase formed during transformation. In the algorithm, effects of changes in chemical free energy, strain free energy and interfacial energies of austenite-austenite, ferrite-ferrite and austenite-ferrite during transformation are considered. From the algorithm, the kinetics of transformation and mean ferrite grain size for different cooling rates are calculated. It is found that there is a good agreement between the calculated and experimental results