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grain-growth
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Abnormal grain growth in alumina dispersion-strengthened copper produced by an internal oxidation process
, Article Scripta Materialia ; Volume 58, Issue 11 , 2008 , Pages 966-969 ; 13596462 (ISSN) ; Simchi, A ; Sharif University of Technology
2008
Abstract
Cu-2.7 vol.% Al2O3 (15 nm) composite was synthesized by an internal oxidation and hot extrusion process. The grain growth at elevated temperatures was studied and compared with extruded copper powder. Abnormal grain growth via a mechanism analogous to that of site-saturated phase transformation was observed. The critical grain size for the abnormal growth was determined to be 1.1 ± 0.2 μm. The growth rate decreased with time until the grain size approaching a final value ranging from 7.9 to 13.3 μm depending on the temperature. © 2008 Acta Materialia Inc
Effects of chemical composition on nanocrystallization kinetics, microstructure and magnetic properties of finemet-type amorphous alloys
, Article Metals and Materials International ; Volume 19, Issue 4 , 2013 , Pages 643-649 ; 15989623 (ISSN) ; Castellero, A ; Rizzi, P ; Tiberto, P ; Hosseini, H. R. M ; Baricco, M ; Sharif University of Technology
2013
Abstract
In this study, the kinetics of nanocrystallization of amorphous Fe 73.5Si13.5B9Nb3Cu1 (F1) and Fe77Si11B9Nb2.4Cu0.6 (F2) alloys is investigated. The microstructure and magnetic properties of the nanocrystalline alloys are compared. The crystallization temperature of F2 alloy is shifted towards lower temperatures with respect to F1. Thus, the crystalline volume fraction and the crystalline grain size at specific annealing temperature for the F2 alloy are higher than for the F1 alloy, accounting for the higher coercive force of F2 alloy with respect to the one of F1 alloy. According to isoconversional methods, the activation energy for crystallization is variable as a function of transformed...
Grain growth kinetics and electrical properties of CuO doped SnO2-based varistors
, Article Journal of Alloys and Compounds ; Volume 770 , 2019 , Pages 784-791 ; 09258388 (ISSN) ; Nemati, A ; Maleki Shahraki, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Up to now, attempts for developing coarse-grained SnO2-based varistors which exhibit high nonlinearity property at lower voltage have become a challenge without any prominent result because of its unknown grain growth mechanism. In this study, the effect of CuO addition to SnO2-based varistors as a grain growth enhancer additive on microstructural development, grain growth kinetics, and electrical properties was investigated. The characterization of grain growth kinetics showed that CuO addition encouraged grain growth and enhanced the grains size as it could be seen in the activation energy which decreased from 594 kJ/mol to 364 kJ/mol. In the samples with a low amount of CuO, the solute...
Microstructure, Properties and Kinetic Characterization in SnO2-Based Varistor with Addition of CuO Nano Particle
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor) ; Seyyed Reyhani, Morteza (Supervisor)
Abstract
The aim of this study is to investigate the effect of Copper oxide on the microstructure, properties, and grain growth kinetic in Tin oxide- Based varistors. Copper oxide was mixed in Tin oxide with different concentration, including 0, 0.1, 0.25, 0.5, and 1 mol% and the samples were sintered at 1250, 1300, and 1350 oC. Then, phase and microstructural characterization was investigated and consequently, electrical properties were evaluated. According to results, Copper Oxide with forming the liquid phase through the sintering process, accelerated grain growth. It was found that, by increasing concentration of CuO, mean grain size was increased from 2.6 µm in 1250 oC and 5 hours to 17.1 µm...
An analytical and experimental investigation on the normal grain growth in metals using the Monte Carlo method
, Article Materials and Design ; Volume 28, Issue 9 , 2007 , Pages 2533-2539 ; 02613069 (ISSN) ; Karimi Taheri, A ; Sharif University of Technology
Elsevier Ltd
2007
Abstract
The prediction of material microstructure is of great interest to the material designers since the property and performance of materials depend strongly on their microstructures. In this work, a Monte Carlo approach is used to investigate the normal grain growth of aluminum and pure copper. The grain growth was calculated at certain temperatures using the grain growth law and compared with the simulation results by varying the Q as a parameter of simulation lattice orientation for pure aluminum. Also the results predicted by the Monte Carlo method showed a good agreement with the experimental results of grain growth of pure cooper. It was found that increase in Q increases the accuracy of...
Electrical conductivity and microstructure of sintered ferrous materials: Sintered iron
, Article Powder Metallurgy, London ; Volume 43, Issue 3 , 2000 , Pages 209-218 ; 00325899 (ISSN) ; Danninger, H ; Sharif University of Technology
Inst of Materials
2000
Abstract
The viability of electrical conductivity as a tool for describing the microstructure of sintered iron compacts was investigated, the sintering temperature being varied from dewaxing to high temperature sintering. The relationships between formation of sintered contacts, presence of lubricants, and mechanical properties were evaluated through determination of conductivity and effective load bearing cross-section Ac. The latter parameter was measured via quantitative fractography of specimens impact fractured at 77 K. The role of porosity and sintering temperature on grain growth in iron was also evaluated using quantitative metallography. It was found that the conductivity of pressed compacts...
Stabilization of nanostructured materials using fine inert ceramic particles
, Article Ceramics International ; Volume 36, Issue 2 , 2010 , Pages 793-796 ; 02728842 (ISSN) ; Rahaei, M. B ; Abdi, M. S ; Sadrnezhaad, S. K ; Sharif University of Technology
2010
Abstract
Modified versions of the Zener drag equation were obtained by evaluating a non-random distribution of incoherent ceramic particles in a nano-crystalline material. Analytical investigation of particle-boundary correlation indicates that the limiting grain size would be proportional to fV -1/3 for fV larger than 2.96%. The limiting grain size can be obtained by a combination of random and non-random Zener drag pressure in the case of volume fractions smaller than 2.96%
The effects of intermediate and post-annealing phenomena on the mechanical properties and microstructure of constrained groove pressed copper sheet
, Article Materials Science and Engineering A ; Volume 515, Issue 1-2 , 2009 , Pages 162-168 ; 09215093 (ISSN) ; Mani, A ; Kazeminezhad, M ; Sharif University of Technology
2009
Abstract
Commercial purity copper sheets were subjected to a severe plastic deformation technique known as constrained groove pressing (CGP). The effect of pass number, intermediate and post-annealing on the yield strength, hardness and final microstructure of the copper specimens were investigated. The initial pass increases the strength much more than the subsequent passes. Intermediate and post-annealing up to 300 °C cannot change the mechanical properties significantly and even in some cases improve the strength and hardness while reduce the hardness inhomogeneity. Microstructure after post-annealing at elevated temperatures shows abnormal grain growth. © 2009 Elsevier B.V. All rights reserved
The relation between particle size and transformation temperature of gibbsite to αLPHA-alumina
, Article Mineral Processing and Extractive Metallurgy: Transactions of the Institute of Mining and Metallurgy ; 2020 ; Nemati, A ; Arzani, K ; Baghshahi, S ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
The transformation of gibbsite to α-alumina occurs in the range 1100 to 1300°C. The higher the calcination temperature, the larger the crystallites and this leads to abnormal grain growth. The main goal of this research was to reduce the transformation temperature of gibbsite to α-alumina by reducing the gibbsite particles size. The sodium content of the gibbsite used in the study was reduced to less than 0.1% by washing it in HCl solution. It was then ground in a fast mill at ambient conditions for different times then calcined at different temperatures. The microstructure, particles size and thermal behaviour of the samples were examined with SEM, XRD, XRF, PSA and STA, respectively. In a...
The relation between particle size and transformation temperature of gibbsite to αLPHA-alumina
, Article Mineral Processing and Extractive Metallurgy: Transactions of the Institute of Mining and Metallurgy ; Volume 131, Issue 2 , 2022 , Pages 111-121 ; 25726641 (ISSN) ; Nemati, A ; Arzani, K ; Baghshahi, S ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
The transformation of gibbsite to α-alumina occurs in the range 1100 to 1300°C. The higher the calcination temperature, the larger the crystallites and this leads to abnormal grain growth. The main goal of this research was to reduce the transformation temperature of gibbsite to α-alumina by reducing the gibbsite particles size. The sodium content of the gibbsite used in the study was reduced to less than 0.1% by washing it in HCl solution. It was then ground in a fast mill at ambient conditions for different times then calcined at different temperatures. The microstructure, particles size and thermal behaviour of the samples were examined with SEM, XRD, XRF, PSA and STA, respectively. In a...
Investigation of Sintering Behavior of BaTiO3 Nanoparticles Synthesized Via Hydrothermal Method
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor) ; Simchi, Abdolreza (Supervisor)
Abstract
In the present work, Barium Titanate nanoparticles were synthesized by a facile hydrothermal method at 180oC for 4 hours and their sintering behavior was studied. The characterization tests illustrated that the obtained powder was BaTiO3 single phase with excess Ti content from stoichiometric composition. The average particle size of about 50 nm and a narrow particle size distribution was noticed. SEM investigations showed that the samples sintered at temperatures less than 1250oC had plate-like grains. This behavior resulted from twin plates existed in the grains and facetted grain boundaries. At the temperatures more than 1250oC, the grains became polygonal due to the formation of trace...
A Study on the Thermal Stability and Microstructure of Nanocrystalline Al-Ti(Ni) Alloys Synthesized by Mechanical Alloying
, M.Sc. Thesis Sharif University of Technology ; Maddah Hosseini, Hamid Reza (Supervisor) ; Seyyed Reihani, Morteza (Supervisor)
Abstract
In the present investigation, the mechanical alloying (MA) technique was employed to produce nanocrystalline Al-Ti Powder mixtures. Elemental Al and Ti powders were mixed with different compositions (0, 5, 10, and 20 wt.% Ti) and then, milled in a vibratory mill up to 7 hr. The variations of powder morphology and particle size, apparent and tap densities, microstructure, grain size, lattice strain, and microhardness were studied with increasing the milling time. While dissolution of Ti in the Al matrix resulted to the formation of supersaturated Al-Ti solid solution in the samples containing 5 and 10 wt.% Ti, the specimen with 20 wt.% Ti, eventually, led to nanocomposite powder with...
Investigation of limiting grain size and microstructure homogeneity in the presence of second phase particles using the Monte Carlo method
, Article Journal of Materials Processing Technology ; Volume 195, Issue 1-3 , 2008 , Pages 195-203 ; 09240136 (ISSN) ; Karimi Taheri, A ; Sharif University of Technology
2008
Abstract
The prediction of material microstructure is of great interest to the material designers since the property and performance of materials depend strongly on their microstructures. In this research the Monte Carlo method and grain growth phenomenon have been used to predict the limiting grain size in the presence of second phase particles. The results showed a good agreement with the previous published results predicted by the analytical models. It was found that the lattice orientation parameter, Q, strongly affects the kinetic of the grain growth. The experimental and theoretical results of limiting grain size predicted by Monte Carlo method showed that by decreasing the value of Q the...
Master sintering curves of a nanoscale 3Y-TZP powder compacts
, Article Ceramics International ; Volume 35, Issue 2 , 2009 , Pages 547-554 ; 02728842 (ISSN) ; Simchi, A ; Dourandish, M ; Golestani Fard, F ; Sharif University of Technology
2009
Abstract
The sintering behavior of commercially available granulated ZrO2-3 mol% Y2O3 (3Y-TZP) powder compacts with an aggregate size of 75 nm was studied. The shrinkage response of the powder compacts during non-isothermal sintering was measured in a sensitive dilatometer at different heating rates. Densification and grain growth were also studied after isothermal firing in air according to different sintering cycles. The sintering and grain growth activation energy was estimated to be QS = 485 ± 12 kJ mol-1 and QG = 546 ± 23 kJ mol-1, respectively. Using the estimated Q-values, the master curves for sintering and grain growth were established and used for prediction of the densification and...
Optimum temperature for recovery and recrystallization of 52Ni48Ti shape memory alloy
, Article Materials and Design ; Volume 28, Issue 6 , 2007 , Pages 1945-1948 ; 02613069 (ISSN) ; Mirabolghasemi, S. H ; Sharif University of Technology
Elsevier Ltd
2007
Abstract
Results of recent studies on the effect of heat treatment after cold rolling on mechanical properties and transformation temperatures of the cast 52Ni48Ti alloys are described. It is seen that stress-induced martensite is formed when both the as-rolled and the low-temperature (≤400 °C) heat-treated samples are strained. Martensite reorientation due to the stress action occurs in samples heat treated at 500 °C and higher. Optimum recovery occurs below 600 °C resulting in hardness reduction. Recrystallization starts at 600 °C resulting in parent phase yield stress enhancement. Yield stress starts to decrease when grain growth and order-disorder transformation both occur above 700 °C. © 2006...
The effects of nano Mgo on physical and mechanical properties of Al 2O3-SiC composites
, Article Journal of Ceramic Science and Technology ; Volume 3, Issue 1 , 2012 , Pages 29-34 ; 21909385 (ISSN) ; Surani, F ; Abdizadeh, H ; Baharvandi, H. R ; Sharif University of Technology
2012
Abstract
In this research, the effects of nano-sized MgO in Al2O 3-SiC composites were investigated. The overall changes in the density and mechanical properties of sintered samples (hardness, bending strength and toughness) were evaluated. After mixing, drying and uniaxial compaction of the powders, they were first heat-treated at low temperature in an electric furnace to remove any residuals. They were then heat-treated at high temperature (1700 °C) inside a graphite furnace in argon atmosphere for sintering (at normal and high pressure). The content of MgO in the Al 2O3-10 vol% SiC composite was 0, 500, 1000, and 1500 ppm. Thefracture toughness(KIC)of sintered composite with 10...
Disabling of nanoparticle effects at increased temperature in nanocomposite solders
, Article Journal of Electronic Materials ; Volume 41, Issue 7 , 2012 , Pages 1907-1914 ; 03615235 (ISSN) ; Roshanghias, A ; Ashayer, R ; Kotadia, H. R ; Khomamizadeh, F ; Kokabi, A. H ; Clode, M. P ; Miodownik, M ; Mannan, S. H ; Sharif University of Technology
2012
Abstract
The use of nanoparticles to control grain size and mechanical properties of solder alloys at high homologous temperature is explored. It is found that silica nanoparticles in the 100 nm range coated with 2 nm to 3 nm of gold can be dispersed within solders during the normal reflow soldering process, and that these particles are effective in hardening the solder and restricting dynamic grain growth during compression testing at low homologous temperature. As the homologous temperature increases towards 0.75, the effects of the nanoparticles on both mechanical properties and dynamical grain growth reduce, and by homologous temperatures of 0.86 the effects have completely disappeared. This...
Microstructure and mechanical properties of WC-10Co cemented carbide containing VC or (Ta, Nb)C and fracture toughness evaluation using different models
, Article International Journal of Refractory Metals and Hard Materials ; Volume 31 , 2012 , Pages 141-146 ; 02634368 (ISSN) ; Abachi, P ; Simchi, A ; Sharif University of Technology
Abstract
This article describes a study on WC-10Co cemented carbides with different percent of grain growth inhibitors. Samples were prepared by the conventional powder metallurgy method, using WC and Co powder and different concentrations of VC and (Ta, Nb)C powder. All samples were processed using a hot isostatic press (HIP) and the effect of grain growth inhibitors on the microstructure and mechanical properties were investigated. Additionally, microstructure and powder particle morphology were examined using scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS). The specimen's microstructure proved that the addition of VC is more effective at suppressing grain growth than...
The annealing phenomena and thermal stability of severely deformed steel sheet
, Article Materials Science and Engineering A ; Volume 528, Issue 15 , June , 2011 , Pages 5212-5218 ; 09215093 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
2011
Abstract
However, there are many works on annealing process of SPDed non-ferrous metals, there are limit works on annealing process of SPDed low carbon steel. Therefore, in this study the annealing responses after constrained groove pressing (CGP) of low carbon steel sheets have been investigated. The sheets are subjected to severe plastic deformation at room temperature by CGP method up to three passes. Nano-structured low carbon steel sheets produced by severe plastic deformation are annealed at temperature range of 100-600 °C for 20. min. The changes of their microstructures after deformation and annealing are studied by optical microscopy. The effects of large strain and annealing temperature on...
Fabrication of AZ31/Al2O3 nanocomposites by friction STIR processing
, Article Reviews on Advanced Materials Science ; Volume 28, Issue 1 , 2011 , Pages 85-89 ; 16065131 (ISSN) ; Kim, H. S ; Kokabi, A. H ; Abachi, P ; Shahraki, B. K ; Sharif University of Technology
2011
Abstract
The aim of this paper is to fabricate AZ31/Al2O3 nanocomposites by friction stir processing (FSP). Due to severe plastic deformation, dynamic recrystallization, and grain growth retardation by nanoparticles during the FSP processing, ultrafine grained microstructures with homogeneous distribution of the nanoparticles were produced. With increasing rotational speed, as a result of the increased plastic deformation and heat generation, increased grain size of the matrix, and simultaneously shattering effect of rotation cause a uniform nanoparticle distribution. By the large plastic deformation, texture of the matrix evolved and especially the (0002) basal plane was developed