检索结果-南通市图书馆

International Journal of minerals,metallurgy and materials 2016年第7期23卷 779-792页

作者： m.A.mostafaei m.kazeminezhad Department of materials Science and Engineering Sharif University of Technology

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 recrystallization and transformation. The microstructural evolution of severely deformed low-carbon steel after ultra-rapid annealing is investigated based on the proposed regimes. Regarding the intensity and start temperature of the interaction, different microstructures consisting of ferrite and pearlite/martensite are formed. It is found that when the interaction is strong, the microstructure is refined because of the high kinetics of transformation and recrystallization. moreover, strain shifts an interaction zone to a relatively higher heating rate. Therefore, severely deformed steel should be heated at relatively higher heating rates for it to undergo a strong interaction.

关键词： low-carbon steel annealing microstructural evolution recrystallization phase transformation plastic deformation

microstructure and mechanical Properties in Dissimilar Butt Friction Stir Welding of Severely Plastic Deformed Aluminum AA 1050 and Commercially Pure Copper Sheets

在线全文

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2014年第8期30卷 826-834页

作者： H.Barekatain m.kazeminezhad A.H.Kokabi Department of materials Science and Engineering Sharif University of TechnologyAzadi AvenueTehranIran

In this study,AA 1050 aluminum alloy and commercially pure copper in annealed and severely plastic deformed conditions were *** technique used for imposing the severe strain to the sheets was constrained groove pressing（CGP） *** annealed and severely plastic deformed sheets were subjected to friction stir welding（FSW） at different rotation and traverse *** was placed in advancing *** offset of approximately 1 mm was used toward Al side for all welds.A range of welding parameters which can lead to acceptable welds with appropriate mechanical properties was *** the FSWed CGPed samples,it was observed that the welding heat input caused grain growth and decrease in hardness value at Al side of the stir *** was found that,generally the weakest parts of weld joints of annealed and CGPed samples were Al base metal and stir zone,*** investigations showed that several forms of intermetallic compounds were produced.

关键词： Friction stir welding Severe plastic deformation Aluminum Copper Intermetallics

Improvement in the mechanical properties of Al/SiC nanocomposites fabricated by severe plastic deformation and friction stir processing

在线全文

学校读者我要写书评

暂无评论

International Journal of minerals,metallurgy and materials 2017年第3期24卷 297-308页

作者： m.Sarkari Khorrami m.kazeminezhad Y.miyashita A.H.Kokabi Department of materials Science and Engineering Sharif University of Technology Department of mechanical Engineering Nagaoka University of Technology

Severely deformed aluminum sheets were processed by friction stir processing(FSP) with Si C nanoparticles under different conditions to improve the mechanical properties of both the stir zone and the heat affected zone(HAZ).In the case of using a simple probe and the same rotational direction(RD) of the FSP tool between passes,at least three FSP passes were required to obtain the appropriate distribution of ***,after three FSP passes,fracture occurred outward from the stir zone during transverse tensile tests;thus,the strength of the specimen was significantly lower than that of the severely deformed base material because of the softening phenomenon in the *** improve the mechanical properties of the HAZ,we investigated the possibility of achieving an appropriate distribution of nanoparticles using fewer FSP *** results indicated that using the threaded probe and changing the RD of the FSP tool between the passes effectively shattered the clusters of nanoparticles and led to an acceptable distribution of Si C nanoparticles after two FSP *** these cases,fracture occurred at the HAZ with higher strength compared to the specimen processed using three FSP passes with the same RD between the passes and with the simple *** fracture behaviors of the processed specimens are discussed in detail.

关键词： friction stir processing plastic deformation aluminum silicon carbide nanocomposites mechanical properties

Effects of non-isothermal annealing on microstructure and mechanical properties of severely deformed aluminum samples:modeling and experiment

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous metals Society of China 2019年第6期29卷 1127-1137页

作者： A.R.KHODABAKHSHI m.kazeminezhad Department of materials Science and Engineering Sharif University of Technology

In order to investigate the evolution of microstructure and flow stress during non-isothermal annealing,aluminum samples were subjected to strain magnitudes of 1, 2 and 3 by performing 2, 4 and 6 passes of multi-directional forging. Then, the samples were non-isothermally annealed up to 150, 200, 250, 300 and 350 ℃. The evolution of dislocation density and flow stress was studied via modeling of deformation and annealing stages. It was found that 2, 4 and 6 passes multi-directionally forged samples show thermal stability up to temperatures of 250, 250 and 300 ℃, respectively. modeling results and experimental data were compared and a reasonable agreement was observed. It was noticed that 2 and 4 passes multi-directionally forged samples annealed non-isothermally up to 350 ℃ have a lower experimental flow stress in comparison with the flow stress achieved from the *** underlying reason is that the proposed non-isothermal annealing model is based only on the intragranular dislocation density evolution, which only takes into account recovery and recrystallization phenomena. However, at 350℃ grain growth takes place in addition to recovery and recrystallization,which is the source of discrepancy between the modeling and experimental flow stress.

关键词： severe plastic deformation multi-directional forging non-isothermal annealing dislocation density-based model microstructure mechanical properties

Effects of heat input in friction stir welding on microstructure and mechanical properties of AA3003-H18 plates

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous metals Society of China 2015年第7期25卷 2147-2155页

作者： B.ABNAR m.kazeminezhad A.H.KOKABI Department of materials Science and Engineering Sharif University of Technology

The non-heat-treatable AA3003-H18 plates were joined by friction stir welding（FSW） to achieve a proper joint by optimizing the welding *** this purpose,the effects of heat input on microstructure and mechanical properties of the welded samples were investigated by changing the ratios of rotational speed（800-1200 r/min） to travel speed（40-100 mm/min）（w/v）.It was revealed that the grain growth rate was strongly increased with the increase of the heat input by rotational speed at constant travel speed,while the grain growth rate was slightly increased with the increase of the heat input by travel speed at constant rotational ***,hardness reduction was observed in the stir zone at higher rotational speed compared with that at lower *** interesting observation was that various welding parameters do not have noticeable effect on the tensile strength of the FSW ***,it has been observed that the fracture location of tensile test specimens was placed in the heat-affected zone（HAZ）on the advancing side at lower travel speed,while at higher travel speed,it was placed at the HAZ/thermomechanical affected zone（TmAZ） interface on the retreating side.

关键词： AA3003-H18 alloy friction stir welding heat input microstructure mechanical properties

Butt joining of Al-Cu bilayer sheet through friction stir welding

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous metals Society of China 2012年第12期22卷 2925-2929页

作者： R.BEYGI m.kazeminezhad A.H.KOKABI Department of materials Science and Engineering Sharif University of Technology

Butt joining of Al–Cu bilayer sheet produced by cold roll bonding was studied through friction stir welding (FSW). A defect free joint was obtained. Flow patterns and mixing of two layers during FSW were investigated. microstructural investigations and hardness profile measurements were carried out. It is shown that material flow in stir zone leads to the formation of banding structure in Cu layer at advancing side. Traces of Al particles along with Al–Cu intermetallic compounds exist in the fined grain region of this banding structure which leads to higher hardness values.

关键词： bilayer sheet Al-Cu sheet friction stir welding microstructure

Influence of cerium ions on structure-dependent magnetic properties of Ba-Sr m-type hexaferrite nanocrystals

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第2期42卷 364-372,I0005页

作者： Ram A.Pawar Sunil m.Patange P.m.Dighe Sher Singh meena Abdullah GAl-Sehemi mehboobali Pannipara Santosh S.Jadhav Department of Physics ArtsCommerce and Science CollegeAhmednagar413711MaharashtraIndia Department of Physics Shri Krishna MahavidyalayaGunjotiDistOsmanabad413606MaharashtraIndia Padmashri Vikhe Patil College of Arts Science and CommercePravaranagarA/P.Loni(Kd)Tal.RahataDistAhmednagar413713MaharashtraIndia Solid State Physics Division Bhabha Atomic Research CentreMumbai400085MaharashtraIndia Department of Chemistry King Khalid UniversityAbha61413Saudi Arabia Department of Physics D.S.M's ArtsCommerce and Science CollegeJintur431509MaharashtraIndia

The present study is a systematic effort to investigate the structure-sensitive magnetic parameters of Ce^(3+) substituted Ba-Sr hexaferrite nanocrystals chemically formulated as Ba_(0.5)Sr_(0.5)Ce_(x)Fe_(12-x)O_(19) where x=0.0-0.2 with Δx=*** hexaferrite powders were prepared using the sol-gel self-ignition route and structurally characterized by means of powder X-ray diffraction and Fourier transform infrared *** creation of the m-type hexaferrite phase within the synthesized samples was revealed from the Rietveld refinement of the X-ray *** occurrence of a secondary phase of CeO_(2) was revealed within the hexaferrites for the substitution,x> *** refined X-ray diffraction data were utilized to compute the lattice parameters,X-ray density,and lattice parameter *** crystal structure plotted from the refined XRD data reveals the occupancy of the ions at different lattice *** XPS data of the hexaferrite were analyzed to confirm the oxidation states of the constituent *** nanocrystalline nature of the hexaferrites was revealed from the crystallite sizes calculated using Scherer's *** analysis of FTIR spectra confirms that only a fraction of Ce^(3+)accommodated in the lattice and the remaining Ce content reside in the form of the CeO_(2) *** morphology of the hexaferrites was analyzed from the FESEm profiles of the ferrite *** magnetic behavior study was performed by analyzing the Curie temperature,hysteresis loops,and hyperfine interactions by means of susceptibility,V.S.m,and mossbauer spectroscopy,*** hexaferrites with increasing coercivity,decreasing saturation magnetization,and decreasing Curie temperature are reported in the *** substituted Ce^(3+)ions inhibit the grain growth and create lattice imperfections giving rise to hexaferrites with tuned magnetic parameters suitable for different applications.

关键词： Ba-Sr hexaferrite Ce^(3+)substitution XPS Saturation magnetization Coercivity m?ssbauer spectroscopy

Frequency-dependent viscoelasticity effects on the wave attenuation performance of multi-layered periodic foundations

在线全文

学校读者我要写书评

暂无评论

Applied mathematics and mechanics(English Edition) 2024年第3期45卷 407-424页

作者： m.SAFI m.VAKILIFARD m.J.mAHmOODI Faculty of Civil Water&Environmental EngineeringShahid Beheshti UniversityTehran ***Iran Faculty of mechanical and Energy Engineering Shahid Beheshti UniversityTehran ***Iran

In this paper,layered periodic foundations(LPFs)are numerically examined for their responses to longitudinal and transverse modes in the time and frequency *** different unit-cells,i.e.,2-layer,4-layer,and 6-layer unit-cells,comprising concrete/rubber,concrete/rubber/steel/rubber,and concrete/rubber/steel/rubber/lead/rubber materials,respectively,are taken into ***,the viscoelasticity behavior of the rubber is modeled with two factors,i.e.,a frequency-independent(FI)loss factor and a linear frequency-dependent(FD)loss *** the extraction of the complex dispersion curves and the identification of the band gaps(BGs),the simulations of wave transmission in the time and frequency domains are performed using the COmSOL *** parametric studies evaluate the effects of the rubber viscoelasticity models on the dispersion curves and the wave transmission for the longitudinal and transverse *** results show that considering the rubber viscoelasticity enhances the wave attenuation ***,the transverse-mode damping is more sensitive to the viscoelasticity model than its longitudinal *** 6-layer unit-cell LPF exhibits the lowest BG,ranging from 4.8 Hz to 6.5 Hz.

关键词： layered metamaterial periodic foundation complex dispersion curve wave transmission diagram

Engineering of efficient visible light photocatalysts:Ti_(1-x+y)Cu_(x)La_(y)O_(2)(x=0.03;y=0,0.005,0.01) compositions

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第3期42卷 497-505,I0003页

作者： S.m.Yakout A.m.Youssef Inorganic Chemistry Department National Research Centre(NRC)El Buhouth StDokkiCairo12622Egypt

In dye-photocatalysis, widening the wavelengths absorption range of catalysts as well as aborting the recombination of the photoexcited charge carriers(electrons-holes pairs) are of paramount *** the current study, we report the photocatalytic characteristics of four compositions composed of TiO_(2),Ti_(0.97)Cu_(0.03)O_(2), Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)powders for two harmful dyes(Congo red and methylene blue). The X-ray diffraction technique verified the configuration of mixed anatase and rutile phases in pure TiO_(2)and Ti_(0.97)Cu_(0.03)O_(2)powders while Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)powders possess anatase phase only. The changes of the band gap structure and dimensions of the unit cell volume of TiO_(2)confirm the substitution of Ti^(4+)sites by Cu^(2+)and La^(3+)ions. Remarkable widening of wavelengths absorption with formation of long absorption tails were found in TiO_(2)(3.13 e V) through insertion of La^(3+)plus Cu^(2+)ions. Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)samples exhibit a visible light band gap of 2.3 and 2.7 e V, respectively. Based on SEm images, incorporation of Cu^(2+)and La^(3+)ions influences the surface morphology of TiO_(2). The resulting Ti_(0.97)Cu_(0.03)O_(2), Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)powders present enhanced photocatalytic activity towards Congo red dye degradation compared to pure one under natural solar spectrum. The best Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)catalyst exhibits superior photocatalytic activity of 96% for 10 ppm CR dye in 20 min as well as above average photocatalytic efficiency of 63% for 30 ppm CR dye in 120 min. As well, it showed acceptable photodegradation activity of 52% for 30 ppm mB solution in 140 min of sunlight irradiation. The heightened photodegradation efficiency of Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)catalyst can be clarified in terms of higher ch

关键词： Semiconductor TiO_(2) Rare earths Congo red methylene blue Solar spectrum Photodegradation

Nonlinear dynamic modeling of planar moving Timoshenko beam considering non-rigid non-elastic axial effects

在线全文

学校读者我要写书评

暂无评论

Applied mathematics and mechanics(English Edition) 2024年第3期45卷 479-496页

作者： m.ABBASI GAVARI m.R.HOmAEINEZHAD Faculty of mechanical Engineering K.N.Toosi University of TechnologyTehran 19991-43344Iran

Due to the importance of vibration effects on the functional accuracy of mechanical systems,this research aims to develop a precise model of a nonlinearly vibrating single-link mobile flexible *** manipulator consists of an elastic arm,a rotary motor,and a rigid carrier,and undergoes general in-plane rigid body motion along with elastic transverse *** accurately model the elastic behavior,Timoshenko’s beam theory is used to describe the flexible arm,which accounts for rotary inertia and shear deformation *** applying Newton’s second law,the nonlinear governing equations of motion for the manipulator are derived as a coupled system of ordinary differential equations(ODEs)and partial differential equations(PDEs).Then,the assumed mode method(Amm)is used to solve this nonlinear system of governing equations with appropriate shape *** assumed modes can be obtained after solving the characteristic equation of a Timoshenko beam with clamped boundary conditions at one end and an attached mass/inertia at the *** addition,the effect of the transverse vibration of the inextensible arm on its axial behavior is *** the axial rigidity,the effect makes the rigid body dynamics invalid for the axial behavior of the ***,numerical simulations are conducted to evaluate the performance of the developed model,and the results are compared with those obtained by the finite element *** comparison confirms the validity of the proposed dynamic model for the *** to the mentioned features,this model can be reliable for investigating the system’s vibrational behavior and implementing vibration control algorithms.

关键词： planar moving Timoshenko beam non-rigid non-elastic axial effect as-sumed mode method(Amm) nonlinear motion analysis