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Journal of Materials Science & Technology 2010年第12期26卷 1078-1082页

作者： S.Ahmadi H.arabi A.Shokuhfar Department of Material Science Faculty of EngineeringTarbiat Modares UniversityTehranIran Center of Excellence of Advanced Materials and Processing(CEAMP) Department of Metallurgy and Materials Science and EngineeringIran University of Science & Technology(IUST)NarmakTehranIran Department of Material Science Faculty of Mechanical EngineeringK.N.Toosi University of TechnologyTehranIran

Effects of multiple strengthening treatments （i.e. ag mechanical properties and stability of nanoscale prec in this research. Various tests such as hardness, tensi ng either at three or four consecutive temperatures） on pitated phases in an AA2090 alloy have been evaluated e, electrical resistance, differential scanning calorimetric （DSC）, and transmission electron microscopy （TEM） have been performed. The results show that the ultimate tensile strength （UTS） and the yield strength of the samples aged at four consecutive temperatures （i.e. natural aging＋190℃＋150℃＋100℃） can be increased approximately to 660 and 610 MPa, respectively. It is also found that precipitation of T1 phase occurs during multiple aging process of the alloy and the higher amounts of enthalpies shown in DSC charts are linked to higher volume fraction of this precipitate. Furthermore, TEM observations reveal that T1 phase has plate shape morphology and its crystal structure is in the form of hcp with lattice parameters of a=0.467 nm and c=0.878 nm.

关键词： Multiple strengthening Thermo mechanical treatment (TMT) Selected area electron diffraction (SAED) pattern Inter planar spacing (d)

Investigation on the homogenization treatment and element segregation on the microstructure of a γ/γ′-cobalt-based superalloy

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International Journal of Minerals,Metallurgy and Materials 2019年第2期26卷 222-233页

作者： Saeed Aliakbari Sani Hossein arabi Shahram Kheirandish Golamreza Ebrahimi School of Materials and Metallurgical Engineering Iran University of Science and Technology ((IUST)) School of Materials and Metallurgical Engineering Iran University of Science and Technology (IUST) Materials and Polymers Engineering Department Faculty of Engineering Hakim Sabzevari University

The aim of the present study was to investigate the effect of element segregation on the microstructure and γ′ phase in a γ/γ′ cobalt-based superalloy. Several samples were prepared from a cast alloy and homogenized at 1300°C for different times, with a maximum of 24 h. A microstructural study of the cast alloy using wavelength-dispersive spectroscopic analysis revealed that elements such as Al, Ti, and Ni segregated mostly within interdendritic regions, whereas W atoms were segregated within dendrite cores. With an increase in homogenization time, segregation decreased and the initial dendritic structure was eliminated. Field-emission scanning electron microscopy micrographs showed that the γ′ phases in the cores and interdendritic regions of the as-cast alloy were 392 and 124 nm, respectively. The size difference of γ′ was found to be due to the different segregation behaviors of constituent elements during solidification. After homogenization, particularly after 16 h, segregation decreased; thus, the size, chemical composition, and hardness of the precipitated γ′ phase was mostly uniform throughout the samples.

关键词： superalloy segregation homogenization microstructure γ′phase

Investigation on the dissolution of η phase in a cast Ni-based superalloy

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International Journal of Minerals,Metallurgy and Materials 2013年第1期20卷 42-48页

作者： M.R. Jahangiri H. arabi S.M.A. Boutorabi School of Metallurgy and Materials Engineering Iran University of Science and Technology Metallurgy Department Niroo Research Institute Center of Excellence for Advanced Materials & Processing Iran University of Science and Technology

The dissolution behavior of rI phase has been investigated in a cast Ni-based superalloy. The results showed that the platelets and blocks of η phase were formed within the interdendritic regions of the microstructure. Applying standard solution annealing at 1150-1160℃ for a period of 4 h did not result in the complete dissolution of η phase. For the complete dissolution of η phase without residual incipient melting, a 2-step solution annealing has been recommended. After dissolution at high tem- peratures, the TI phase transforms to two MC-type carbides： one is enriched in Ti, Nb, and Ta, and the other is of （Zr,Ti）C type.

关键词： superalloys nickel alloys phase transitions dissolution heat treatment carbides

Evaluation of the Electroslag Remelting Process in Medical Grade of 316LC Stainless Steel

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Journal of Materials Science & Technology 2009年第5期25卷 592-596页

作者： S.Ahmadi H.arabi A.Shokuhfar A.Rezaei Institute of Advanced Technologies for Metallic Materials Tarbiat Modares University Center of Excellence of Advanced Materials and Processing(CEAMP) Department of Metallurgy and Materials Science and EngineeringIran University of Science&Technology(IUST) Department of Material Science Faculty of Mechanical EngineeringK.N.Toosi University of Technology

This study is focused on the effects of electroslag remelting by prefused slag （CaO, Al2O3, and CaF2） on macrostructure and reduction of inclusions in the medical grade of 316LC （316LVM） stainless steel. Analysis of the obtained results indicated that for production of a uniform ingot structure during electroslag remelting, shape and depth of the molten pool should be carefully controlled. High melting rates led to deeper pool depth and interior radial solidification characteristics, while decrease in the melting rates caused more reduction of nonmetallic inclusions. Large shrinkage cavities formed during the conventional casting process in the primary ingots were found to be the cause of the fluctuation in the melting rate, pool depth and extension of equiaxed crystals zone.

关键词： Ultra clean steel Electroslag Radial solidification remelting Prefused slag Vertical solidification

Assessment of radioactivity levels in some oil samples from the western desert,Egypt

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Nuclear Science and Techniques 2007年第2期18卷 118-122页

作者： A. ABBADY A.M. EL-arabi W. RASHED Physics Department Faculty of Science South Valley University Qena Egypt

Distributions of natural gamma-emitting radionuclides were determined in 93 oil samples collected from some petroleum fields in the western desert of Egypt. The radioisotope activities in the area under investigation lay in the range of (21 ± 4) to (38 ± 13) Bq?L-1 for 226Ra, (9 ± 2) to (15 ± 5) Bq?L-1 for 232Th, and (154 ± 28) to (303 ± 54) Bq?L-1 for 40K. The mean values were 27, 12, and 201 Bq?L-1, respectively. Among oils, variations in radionuclide ac- tivities could be on account of differences in TDS, HCO3, and Ba, with high or low pH. In this environment, oil prop- erties differently affected the mobilization of natural radionuclides. The range of 226Ra variation had been compared with available data from other countries. The calculated absorbed dose rate ranged from 22.33 to 32.66 nGy?h-1 in lo- cation (B) and (E) respectively, which was less than the accepted value.

关键词：埃及西部沙漠地区油料样品放射性评估

Reducing resin content and board density without adversely affecting the mechanical properties of particleboard through controlling particle size

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Journal of Forestry Research 2011年第4期22卷 659-664页

作者： Mohammad arabi Mehdi Faezipour Heydar Gholizadeh Department of Wood & Paper Science and Technology Faculty of Nat- ural Resources University of Tehran P.O. Box 4111 Karaj 31587-77871 Iran Department of Agricultural Economics College of Agriculture and Natural Resources University of Tehran Karaj 31587-77871 Iran

Density and resin content are two factors that have a significant effect on the production cost of wood composite. However, particle size affects resin content and density, which suggests that the interaction of these three factors can be manipulated to reduce the board density and resin content of particleboard without adversely influencing its mechanical properties. Some mathematical functional forms based on resin content, board density and slenderness ratio were regressed and an appropriate form was chosen. According to analysis of the results using SHAZAM 9 software, the exponential function best fit the experimental data. Finally, ＂indifference curves＂ of mechanical properties were illustrated and analyzed. The results indicated that negative effects of density or resin content reduction on mechanical properties could be compensated for by controlling particles＇ slenderness ratio. Interestingly, increases in slenderness ratio compensated for the negative effects of decreases in resin content or board density on module of rupture （MOR） and module of elasticity （MOE）. Moreover, this ＂compensation ratio＂ intensified as resin content or density decreased and/or as the MOR or MOE increased. On the other hand, reduction in slenderness ratio indicated a comple- mentary effect on reducing internal bond （IB） strength, a result of decreases in resin content or density. Moreover, this ＂complementary ratio＂ was intensified as resin content or density decreased and/or as IB strength increased.

关键词： mechanical properties board density resin content slender-ness ratio partieleboard.

Estimation in the Complementary Exponential Geometric Distribution Based on Progressive Type-II Censored Data

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Communications in Mathematics and Statistics 2020年第4期8卷 409-441页

作者： Ozlem GürünlüAlma Reza arabi Belaghi Department of Statistics Faculty of SciencesMuğla SıtkıKoçman UniversityMuğlaTurkey Department of Statistics Faculty of Mathematical SciencesUniversity of TabrizTabrizIran

Complementary exponential geometric distribution has many applications in survival and reliability *** to its importance,in this study,we are aiming to estimate the parameters of this model based on progressive type-II censored *** do this,we applied the stochastic expectation maximization method and Newton-Raphson techniques for obtaining the maximum likelihood *** also considered the estimation based on Bayesian method using several approximate:MCMC samples,Lindely approximation and Metropolis-Hasting *** addition,we considered the shrinkage estimators based on Bayesian and maximum likelihood ***,the HPD intervals for the parameters are constructed based on the posterior samples from the Metropolis-Hasting *** the sequel,we obtained the performance of different estimators in terms of biases,estimated risks and Pitman closeness via Monte Carlo simulation *** paper will be ended up with a real data set example for illustration of our purpose.

关键词： Bayesian analysis Complementary exponential geometric(CEG)distribution Progressive type-II censoring Maximum likelihood estimators SEM algorithm Shrinkage estimator

Mathematical modeling and simulation of the interface region of a tri-layer composite material,brass-steel-brass,produced by cold rolling

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International Journal of Minerals,Metallurgy and Materials 2009年第2期16卷 189-196页

作者： H. arabi S.H. Seyedein A. Mehryab B. Tolaminejad School of Metallurgy and Materials Engineering Iran University of Science and TechnologyIUSTNarmakTehranIran

The object of this study was to find the optimum conditions for the production of a sandwich composite from the sheets of brass-steel-brass. The experimental data obtained during the production process were used to validate the simulation program, which was written to establish the relation between the interface morphology and the thickness reduction amount of the composite. For this purpose, two surfaces of a steel sheet were first prepared by scratching brushing before inserting it between two brass sheets with smooth surfaces. Three sheets were then subjected to a cold rolling process for producing a tri-layer composite with various thick- nesses. The sheet interface after rolling was studied by different techniques, and the bonding strength for each rolling condition was determined by peeling test. Moreover, a relation between interfacial bonding strength and thickness reduction was found. The simulation results were compared with the experimental data and the available theoretical models to modify the original simulation program with high application efficiency used for predicting the behavior of the interface under different pressures.

关键词： sandwich composite cold rolling mathematical simulation metallic bonding interface

Gamma-ray measurements of natural radioactivity in sedimentary rocks from Egypt

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Nuclear Science and Techniques 2006年第2期17卷 123-128页

作者： A.M.EL-arabi Adel G.E.ABBADY A.S.HUSSEIN Physics Department Faculty of Science South Valley University Qena Egypt Radiation Protection Department Nuclear Power Plants Authority Egypt

The aim of this study was to measure concentrations and distributions of natural radionuclides occurring in rocks. The activity concentrations (Bq·kg-1) of the naturally occurring radionuclides 226Ra, 232Th, and 40K in sedi- mentary rock samples from Eastern Desert (Um El-Huetat), Nile Valley (Gebel Owina) and from southwest Sinai (Wadi Ghweiba) were measured using a high-purity germanium detector. The samples under investigation (clay, shale and sandstone) were used as raw materials in the construction industry (bricks, ceramics, cement, fillers, etc.). Though the sediments of Egypt have already been investigated in the geological and mineralogical aspects, it is necessary to investigate the natural radioactivity in order to complete their classification. The average concentration values of 226Ra, 232Th, 40K in the surveyed samples were 47 ± 7 , 21± 5, 393±19 ***-1 (clay); 23 ± 5, 30 ± 6, 563 ± 24 ***-1 (shale); and 17 ± 4, 14 ± 4, 299 ± 17 ***-1 (sandstone), respectively. All sediment samples have radium equivalent activities ranging from 55 to 115 Bq·kg-1, lower than the limit set in the OECD Report (370 Bq·kg-1). The overall mean outdoor terrestrial gamma dose rates fluctuate from 28 to 55 nGy·h-1. The external gamma radiation dose due to natural radionuclides present in the samples have been computed and compared with the global averages. In terms of the radiation safety, the natural radioactivity of the sediment in Egypt is below the recommended limits of the gamma dose rate. Therefore, they can be used for all kinds of public buildings.

关键词：天然放射性核素页岩沙岩埃及

A Comparative Study of the Electronic and Magnetic Properties of Gd_5Ge_4 and Gd_5Si_4 Compounds

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Communications in Theoretical Physics 2014年第12期61卷 903-908页

作者： Z.Momeni Larimi A.Amirabadizadeh A.Yazdani H.arabi Department of Physics Faculty of Science University of Birjand P.O.Box 97175-615 Birjand Iran Tarbiat Modares University Tehran P.O.Box 14115-175 Iran Department of Physics Faculty of Basic Science Ferdowsi University Mashhad Iran

We present a comparative study of electronic structure and magnetic properties of Gd5Si4 and Gd5Ge4compounds using first principles full potential linearized augmented plane wave(FP-LAPW) method based on density functional theory(DFT) using the WIEN2 k code. The local-spin density approximation with correlation energy(LSDA+U) method has been used as the exchange-correlation potential. The optimized lattice constants are in good agreement with the experimental data. The total and partial density of states(DOS) of Gd5Si4 and Gd5Ge4show the difference in Si 3p-Gd 5d and Ge 4p-Gd 5d hybridization, which have an effective role in indirect exchange *** addition, the magnetic moments of Gd, Si, and Ge atoms and the compounds are calculated to clarify the differences in the magnetic properties of these compounds.

关键词： magnetocaloric compound density functional theory electronic and magnetic properties exchange interaction