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crystal-microstructure
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Development of fcc-Al nanoparticles during crystallization of amorphous Al–Ni alloys containing mischmetal: Microstructure and hardness evaluation [electronic resource]
, Article Materials Science and Engineering A ; Volume 604, 16 May 2014, Pages 92-97 ; Simchi, A ; Varahram, N ; Park, E. S ; Sharif University of Technology
Abstract
In the present work, fcc-Al nanoparticle development in Al90−xNi10MMx (MM: Ce mischmetal; x=2, 4) amorphous alloys was studied via non-isothermal differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, and nanoindentation test. Results showed that the crystallization of Al88Ni10MM2 alloy occurred by the precipitation of fcc-Al nanoparticles followed by the crystallization of Al11MM3 and Al3Ni phases. Transmission electron microscopy revealed that the aluminum precipitates had an average size of ~12 nm with a round morphology. Increasing the mischmetal content to 4 at% (Al86Ni10MM4 alloy) caused a three-stage crystallization process with a change in the size...
Age-hardening behavior and phase identification in solution-treated AEREX 350 superalloy
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 37, Issue 7 , 2006 , Pages 2051-2057 ; 10735623 (ISSN) ; Sharif University of Technology
2006
Abstract
This article presents results of an investigation on age-hardening behavior of superalloy AEREX 350. Microhardness testing was employed to evaluate the age-hardening response of the alloy while optical, scanning, and transmission electron microscopy techniques were used to characterize the major phases formed during the aging process. No significant hardening was found in solution-treated samples aged at temperatures up to about 680 °C. Aging at 700 °C up to 950 °C, however, caused a characteristic hardening response. This hardening was concurrent with the formation of γ', an ordered phase with L12 structure, as fine precipitate distributed throughout the fcc matrix. In the temperature range...
Improvement of grain structure and mechanical properties of a land based gas turbine blade directionally solidified with liquid metal cooling process
, Article Materials Science and Technology ; Volume 24, Issue 1 , 2008 , Pages 100-106 ; 02670836 (ISSN) ; Mehrara, M ; Varahram, N ; Davami, P ; Sharif University of Technology
2008
Abstract
The manufacturing process of a directionally solidified (DS) IN738LC turbine blade, produced with the liquid metal cooling (LMC) process was improved based on process modelling. The improvement involved varying the system dimensions in the baffle area and optimising the mould thickness, design and the withdrawal parameters. The grain structure of the DS blades produced exhibits a well defined <001> texture with a few stray grains near the blade top compared to the previous design. Some blades were given to a two stage heat treatment followed by tension tests at 25 and 650°C as well as creep tests at 152 MPa/982°C and 340 MPa/850°C. The yield and tensile strength of improved DS blades were...
Remanent magnetization of Fe1-xCox fine particles
, Article 4th International Conference on Magnetic and Superconducting Materials, MSM'05, Agadir, 5 September 2006 through 8 September 2006 ; Volume 3, Issue 9 , 2006 , Pages 3281-3284 ; 18626351 (ISSN) ; Zoriasatain, S ; Akhavan, M ; Sharif University of Technology
2006
Abstract
Fine Fe1-xCox grains with various values of × have been grown via the borohydride method in the presence of different magnetic fields, H0. In this method, the presence of magnetic moments at the bcc lattice sites of iron causes the formation of acicular single domain grains with a nearly 0.2 μm length. The magnetic field, H0, sets the magnetic moment of SD grains parallel to each other and forms some chains of these particles. This is equivalent to the presence of an effective internal field that increases the remanent magnetization, Mr. From the SW model point of view, the remanent magnetization of sample is determined by Boltzman distribution function at the two minimum energies. In fact,...
Thermal and grain-structure simulation in a land-based turbine blade directionally solidified with the liquid metal cooling process
, Article Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science, Warrendale ; Volume 31, Issue 6 , 2000 , Pages 1293-1304 ; 10735615 (ISSN) ; Varahram, N ; Davami, P ; Rappaz, M ; Sharif University of Technology
Minerals, Metals & Materials Soc (TMS)
2000
Abstract
The thermal field and the grain structure of a cored superalloy turbine blade, which has been directionally solidified with the liquid metal cooling (LMC) process, has been simulated in three dimensions using a cellular automaton (CA) coupled with finite-element (CAFE) model. The cooling induced by the liquid aluminum bath has been replaced by a heat-transfer coefficient, whose temperature- and time-dependence has been adjusted on the basis of natural convection simulations and dimensionless analyses. The simulated grain structure and crystallographic texture have been compared with the microstructure, and the electron back-scattered diffraction (EBSD) results were obtained for a real blade....
A study on non-isothermal static recrystallization during hot rolling of carbon steels
, Article Materials and Manufacturing Processes ; Volume 28, Issue 3 , 2013 , Pages 236-241 ; 10426914 (ISSN) ; Serajzadeh, S ; Sharif University of Technology
2013
Abstract
In this article, the effects of hot rolling parameters on static recrystallization, mechanical properties, and final microstructures of a low carbon steel have been investigated. A numerical analysis was first employed to determine distributions of temperature, strain, and strain rate during hot rolling and then the predicted results were combined with the additivity rule together with Avrami equation to evaluate the progress of non-isothermal static recrystallization after hot rolling. In the next stage, hot rolling experiments have been performed under different rolling conditions to assess the effects of rolling layout on microstructures and mechanical properties of the rolled steel. The...
Influence of stored strain on fabricating of Al/SiC nanocomposite by friction stir processing
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 46, Issue 5 , May , 2015 , Pages 2021-2034 ; 10735623 (ISSN) ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
Springer Boston
2015
Abstract
In this work, 1050 aluminum (Al) sheets were annealed and severely deformed by 1, 2, and 3 passes of constrained groove pressing process to obtain the various initial stored strain values of 0, 1.16, 2.32, and 3.48, respectively. Friction stir processing (FSP) was then applied using SiC nanoparticles to fabricate Al/SiC nanocomposite with approximately 1.5 vol pct reinforced particles. Microstructural examinations revealed that an increase in the initial stored strain of the base metal led to the formation of finer grain structure after 1 pass of FSP. The finer grain structure occurred in the stir zone where a sufficient amount of nanoparticles with a relatively proper distribution existed....
The correlation of stir zone texture development with base metal texture and tool-induced deformation in friction stir processing of severely deformed aluminum
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 48, Issue 1 , 2017 , Pages 188-197 ; 10735623 (ISSN) ; Kazeminezhad, M ; Miyashita, Y ; Kokabi, A. H ; Sharif University of Technology
Springer Boston
2017
Abstract
The texture development during friction stir processing (FSP) of 1050 aluminum severely deformed at the strain magnitude of 2.32 was comprehensively discussed. It was observed that the component B¯ of the ideal shear texture along with the cube texture was developed in the severely deformed base metal. The effects of base metal texture on the texture development of stir zone, thermo-mechanically affected zone, and heat-affected zone during FSP were examined. Also, the developed texture components in the vicinity of the FSP tool and the stir zone were correlated to the deformation induced by the rotating tool which consisted of pin and shoulder. The observed texture components in the...
The effect of prestrain temperature on kinetics of static recrystallization, microstructure evolution, and mechanical properties of low carbon steel
, Article Journal of Materials Engineering and Performance ; Volume 27, Issue 5 , 2018 , Pages 2049-2059 ; 10599495 (ISSN) ; Karimi Taheri, K ; Karimi Taheri, A ; Sharif University of Technology
Springer New York LLC
2018
Abstract
In this research, the samples of a low carbon steel sheet were rolled up to a thickness prestrain of 67% at three different temperatures consisted of room, blue brittleness, and subzero temperature. Microhardness, SEM, and tensile tests were carried out to evaluate the static recrystallization kinetics defined by the Avrami equation, microstructural evolution, and mechanical properties. It was found that the Avrami exponent is altered with change in prestrain temperature and it achieves the value of 1 to 1. 5. Moreover, it was indicated that prestraining at subzero temperature followed by annealing at 600 °C leads to considerable enhancement in tensile properties and kinetics of static...
Effect of current density on electrochemical phosphating of stainless steel 316L
, Article TMS 2009 - 138th Annual Meeting and Exhibition, San Francisco, CA, 15 February 2009 through 19 February 2009 ; Volume 3 , 2009 , Pages 613-620 ; 9780873397407 (ISBN) ; Afshar, A ; Sharif University of Technology
2009
Abstract
In this study two cation coating of calcium and zinc has been developed on stainless steel 316L by electrochemical method. Cathodic current used as an accelerator for phosphating process and the effects of current density on microstructure of the phospahted layer and the time needed for termination of the phosphating process has been evaluated by potential-time, SEM, EDS, etc. Results indicate that higher current densities in electrochemical phosphating will result in heavier phospahted layer with finer crystal size which in turn deteriorates the quality of the layer by its higher porosity. Chemical analysis of the layer reveals that using the electrochemical method for phosphating of...
Structural changes during synthesizing of nanostructured W-20 wt% Cu composite powder by mechanical alloying
, Article Materials Science and Engineering A ; Volume 445-446 , 2007 , Pages 86-93 ; 09215093 (ISSN) ; Simchi, A ; Razavi Hesabi, Z ; Sharif University of Technology
2007
Abstract
Nanostructured W-20 wt% Cu composite powder was synthesized by mechanical alloying (MA) in an Attritor ball mill. The morphological changes and structural evolution of the composite powder during MA was studied by employing scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), laser particle size analyzer (LPS), inductively coupled plasma (ICP) spectrometry, atomic absorption spectrophotometery (AAS), and the bulk powder density measurement. The results were compared with those obtained from attrition milling of monolithic W and Cu powders processed at the same condition. Whereas the milling mechanism of the monolithic powders follow the ductile (for Cu)...
Post-consumer recycled high density polyethylene/polypropylene blend with improved overall performance through modification by impact polypropylene copolymer: morphology, properties and fracture resistance
, Article Polymer International ; Volume 70, Issue 12 , 2021 , Pages 1701-1716 ; 09598103 (ISSN) ; Sharifi, H ; Sharif University of Technology
John Wiley and Sons Ltd
2021
Abstract
The effect of an impact polypropylene copolymer (IPC) having excellent stiffness–toughness balance on the microstructure and properties of a blend comprising 80 wt% recycled high density polyethylene (rHDPE) and 20 wt% recycled isotactic polypropylene (rPP) was studied. Morphological observations revealed improved interfacial interactions, a finer dispersion state and a more homogeneous phase morphology upon IPC incorporation into the blend up to 20 wt%. Flexural modulus, flexural strength, tensile strength and tensile ductility were steadily increased with IPC loading, and exhibited 13%, 14%, 35% and 520% improvement at 20 wt% IPC. A monotonic rise in Izod impact energy, accompanied by a...
Mechanical-activated phase formation of niti in the presence of nanoparticles
, Article Nano ; Volume 8, Issue 5 , 2013 ; 17932920 (ISSN) ; Ebadzadeh, T ; Vaezi, M. R ; Simchi, A ; Kim, H. S ; Sharif University of Technology
2013
Abstract
Effect of Al2O3 nanoparticles (80 nm) on the grain structure and phase formation in Ni-50Ti system during high-energy mechanical alloying (MA) was studied. While the formation of NiTi B2 phase occurs progressively during MA, it is shown that the hard inclusions cause abrupt phase formation at short milling times, particularly at higher nano-Al 2O3 contents. High-resolution transmission electron microscopy showed significant grain refinement in the presence of alumina nanoparticles to sizes less than 10 nm, which precedes the formation of semicrystalline structure and reduces the diffusion length and thus accelerates the phase formation. The composite powder reached steady-state MA condition...
On the constitutive modeling and microstructural evolution of hot compressed A286 iron-base superalloy
, Article Journal of Alloys and Compounds ; Volume 564 , 2013 , Pages 13-19 ; 09258388 (ISSN) ; Abbasi, S. M ; Momeni, A ; Karimi Taheri, A ; Sharif University of Technology
2013
Abstract
The hot working behavior of A286 was studied using hot compression tests over temperature range of 950-1100 °C and at strain rates of 0.001-1 s -1. The flow curves of the material over the studied temperatures and strain rates were typical of dynamic recrystallization. However, some points reflected a change in the mechanism of softening with the change of strain rate. The relation between flow stress, deformation temperature and strain rate was examined via power-law, hyperbolic sine and exponential constitutive equations and the hyperbolic sine function was found more appropriate. The peak strain increased with strain rate up to 0.01 s-1 and then unexpectedly decreased at higher strain...
Constitutive analysis and microstructural evolution in hot working of nanostructured Al6063
, Article Proceedings of the International Euro Powder Metallurgy Congress and Exhibition, Euro PM 2012, 16 September 2012 through 19 September 2012, Basel ; Volume 1 , September , 2012 ; 9781899072361 (ISBN) ; Simchi, A ; Sharif University of Technology
European Powder Metallurgy Association (EPMA)
2012
Abstract
Flow curves and microstructural changes of nanostructured Al6063 alloy produced by mechanical alloying followed by hot extrusion were investigated by means of uniaxial compression test in the temperature range between 300 and 450 °C and strain rate range between 10-2 and 1 s-1. The analysis of flow curves were performed by a hyperbolic sine law equation and the stress exponent and activation energy were determined to be 2.9 and 228 kJ mol-1, respectively. The microstructural constituents for elaboration of deformation mechanisms were observed by TEM and EBSD under FEG-SEM. The microstructural observations determine that dynamic recovery through the formation of subgrains within the grains...
Effect of starting microstructure through severe plastic deformation and Ultra-Rapid annealing of Low-Carbon steel
, Article Steel Research International ; Volume 87, Issue 11 , 2016 , Pages 1527-1533 ; 16113683 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
Wiley-VCH Verlag
Abstract
In this research, low-carbon steel sheets with two different microstructures containing carbides (as-received steel) and pearlites (austenitized steel) are subjected to severe plastic deformation (SPD), and ultra-rapid annealing (URA) is applied with the heating rate of 200 °C s−1 up to the intercritical temperature near Ac1. Microstructure of SPDed as-received steel after URA is consisted of fully refined ferrite grains surrounded by fine pearlites; but for SPDed austenitized steel, grain refinement is not observed, and microstructure is consisted of martensite and high fraction of coarse non-recrystallized ferrite. Presence of carbides for SPDed as-received steel leads to strong...
Microstructural evolution during ultra-rapid annealing of severely deformed low-carbon steel: strain, temperature, and heating rate effects
, Article International Journal of Minerals, Metallurgy and Materials ; Volume 23, Issue 7 , 2016 , Pages 779-792 ; 16744799 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
University of Science and Technology Beijing
Abstract
An interaction between ferrite recrystallization and austenite transformation in low-carbon steel occurs when recrystallization is delayed until the intercritical temperature range by employing high heating rate. The kinetics of recrystallization and transformation is affected by high heating rate and such an interaction. In this study, different levels of strain are applied to low-carbon steel using a severe plastic deformation method. Then, ultra-rapid annealing is performed at different heating rates of 200–1100°C/s and peak temperatures of near critical temperature. Five regimes are proposed to investigate the effects of heating rate, strain, and temperature on the interaction between...
Influence of ambient and cryogenic temperature on friction stir processing of severely deformed aluminum with SiC nanoparticles
, Article Journal of Alloys and Compounds ; Volume 718 , 2017 , Pages 361-372 ; 09258388 (ISSN) ; Kazeminezhad, M ; Miyashita, Y ; Saito, N ; Kokabi, A. H ; Sharif University of Technology
Abstract
The texture, microstructure, and mechanical properties of severely deformed aluminum subjected to friction stir processing (FSP) with SiC nanoparticles under ambient and cryogenic temperatures are comprehensively investigated. Even one pass of FSP in the ambient temperature results in the formation of quite large grain structure with random texture in the heat affected zone (HAZ). It suggests the occurrence of static recrystallization and subsequent grain growth because of the appreciable strain stored within the base metal. One FSP pass under condition of cryogenic temperature causes to the development of bimodal grain size distribution in HAZ, including the elongated grains with interior...
Investigation of microstructure effect on fretting fatigue crack initiation using crystal plasticity
, Article Fatigue and Fracture of Engineering Materials and Structures ; 2018 ; 8756758X (ISSN) ; Farrahi, G. H ; Karimpour, M ; Bahai, H ; Majzoobi, G. H ; Sharif University of Technology
Blackwell Publishing Ltd
2018
Abstract
The onset of fretting fatigue is characterized by material microstructural changes in which the extent of the damage is comparable to grain size, and hence, the microstructure characteristics could have a significant effect on fatigue crack initiation. In this paper, a three-dimensional finite element crystal plasticity framework is presented for simulation of the fretting fatigue. Controlled Poisson Voronoi tessellation (CPVT) method is employed to generate the polycrystalline region. In the CPVT method, regularity parameter controls the shape of grains. In this study, the impact of grain size and regularity parameter on crack initiation life and initiation site has been investigated....
Correlation between isothermal crystallization properties and slow crack growth resistance of polyethylene pipe materials
, Article Polymer Testing ; Volume 80 , 2019 ; 01429418 (ISSN) ; Pircheraghi, G ; Rashedi, R ; Sepahi, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this study, three PE100 polyethylene materials with fairly different short chain branch distributions were used to characterize the relation between thermal properties and creep test failure time. The samples were thermally characterized using isothermal and non-isothermal differential scanning calorimetry (DSC). The three resins showed different behavior after fitting on the Avrami equation. N-100J2 sample, in which short chain branches (SCBs) are located on longer molecule chains, has a lower chain mobility and higher crystallization time, while N-100J1 has the opposite crystallization properties. Also, these samples had different Avrami index, n. Microstructural evaluation of these...