Sharif Digital Repository

An examination of the influence of rolling path change on the static recrystallization behavior of commercial purity aluminum was performed in the present work. Aluminum strips were cold rolled to a reduction of 50 % under various rolling sequences, i.e. single-pass, double-pass from one direction and with reverse directions, and were then annealed in 290 °C for different durations, while mechanical evaluations such as hardness and tensile tests were used to study the mechanical response of cold deformed and annealed samples. It was indicated that a variation in the recrystallization kinetics of the cold rolled aluminum strips takes place when the rolling path is altered from single to... 

One of the important parts of each transformer is core. It is made from multilayer silicon steel sheets. Silicon steel has high magnetic permission, high electrical resistance and minimum hysterics loss. In different metal forming process, lubrication is done for reducing friction effects. In this research, effect of 3 different type lubricants, mineral material (castor oil), organic material (glycerol), and semi organic material (paraffin) with and without additive (graphite) is investigated. Also, effect of 2 industrial lubricants (suds and motor oil) is compromised with above lubricants. Results show the best lubricant for second cold rolling of silicon steel is semi organic (paraffin)... 

This paper describes the effects of using direct and pulse current on composition and corrosion resistance of Fe-Ni-Cr alloy coatings. In both direct and pulse current electrodeposition, increasing the current density has a decreasing effect on Fe and Ni and an increasing influence on Cr. In pulse current electrodeposition, duty cycle has a greater effect than frequency on composition of the alloy coating, particularly in the range of 10-50%. In this range, by increasing the duty cycle, Ni decreases, Fe sharply increase and Cr shows an increasing trend. Following a study of the microhardness of coatings, it is determined that the microhardness increases about 1.5 times by pulse current... 

The application of electropulsing treatment (EPT) is studied on the microstructure and hardness of cold-rolled low carbon steel. The effects of electrical pulses on the grain refinement, precipitate size evolution and hardness are investigated. It is found that applying electrical pulse decreases the grain and precipitate size and increases the hardness in the early stages of electropulsing, but the grain and precipitate size is increased and the hardness is decreased by continuing electropulsing. Also, the effect of electropulsing treatment variables as well as treated time and number of periods are discussed. It is demonstrated that increasing treated time can accelerate achieving maximum... 

In this paper, we report on a periodic metallo-dielectric structure that supports geometry-induced surface plasmons in the sub-terahertz regime. The proposed structure is made up of a dielectric-coated metallic grating sandwiched by parallel metal plates. Based on the modal analysis of 2D and 3D structures, the impact of a metal cladding and a customized dielectric coating on the dispersion relation and field distribution of the guided surface wave is investigated. It is found that modal field confinement is improved in the presence of a metal cladding without narrowing the operational bandwidth of the waveguide. Moreover, a customized subwavelength-sized dielectric coating based on... 

In this paper, we report on a periodic metallo-dielectric structure that supports geometry-induced surface plasmons in the sub-terahertz regime. The proposed structure is made up of a dielectric-coated metallic grating sandwiched by parallel metal plates. Based on the modal analysis of 2D and 3D structures, the impact of a metal cladding and a customized dielectric coating on the dispersion relation and field distribution of the guided surface wave is investigated. It is found that modal field confinement is improved in the presence of a metal cladding without narrowing the operational bandwidth of the waveguide. Moreover, a customized subwavelength-sized dielectric coating based on... 

The microstructure of cold rolled Al–6Mg alloy is investigated after two steps annealing at different coupled temperatures of 250–320 °C and 320–400 °C for various times. Dynamic strain aging behavior in terms of serrated flow and strain rate sensitivity is investigated. The effect of three microstructural features, cell structure, recovered and recrystallized microstructures, on the strain rate sensitivity is elucidated. Two steps annealing process is utilized to capture the effect of recovery and precipitation phenomena on recrystallization and dynamic strain aging behaviors. The results show that the negative strain rate sensitivity of cold rolled specimen increases to positive values in... 

In this work, softening kinetics after cold rolling has been simulated using a coupled finite element-cellular automata model. Firstly, a two-dimensional rigid plastic finite element analysis has been developed to assess strain field and the stored energy accumulation during cold rolling as well as the initial condition of the mesoscopic model. Then, the cellular automata scheme has been employed to calculate the progress of static recrystallization at a given temperature while a dislocation-base model was simultaneously utilized to consider the effect of recovery on static softening process and final microstructures. The model has been examined on isothermal annealing of cold rolled AA5052... 

In the present research, the effect of residual stress distribution on the static strain aging (SSA) phenomenon in cold rolled steel was investigated. A three-dimensional model was employed to evaluate the residual stress distributions within the rolled strips, and hole drilling experiments were also performed to verify the data obtained from the mathematical model. Hardness and tensile tests were then performed on the cold rolled samples at different temperatures and aging periods, and the results of these tests were utilised to assess SSA behaviour after different rolling programs. The results show that SSA occurs within the cold rolled steel in the employed aging period, and its kinetics... 

Vertical copper oxide nanoflakes were synthesized on a Cu foil through oxidation in alkaline conditions. X-ray photoelectron spectroscopy showed that after exposing the nanoflakes to an Escherichia coli bacterial suspension, the outermost surface of the nanoflakes was chemically reduced through the glycolysis process of the bacteria. Current-voltage (I-V) characteristics of the nanoflakes (measured perpendicular to surface of the Cu foil by using conductive atomic force microscopy) indicated that electrical resistivity of the nanoflakes increased about one order of magnitude after exposure to the bacterial suspension. The nanoflakes reduced by the bacterial suspension could also be... 

Various morphologies of CuO/Cu(OH)2 nanostructures with different adsorbed -OH contents were synthesized on an acid-treated Cu foil through variation of NaOH concentration from 0 to 50 mM with an in situ oxidation method. X-ray diffractometry and X-ray photoelectron spectroscopy (XPS) indicated formation of CuO on the Cu(OH)2 crystalline phase at a growth temperature of 60°C for 20 h. Antibacterial activity of the nanostructures against Escherichia coli bacteria was studied in the dark and under light irradiation. The nanostructures grown at a NaOH concentration of 30 mM showed the highest surface area and the strongest antibacterial activity among the samples. After elimination of the... 

In this study, static strain aging behaviour of cold rolled steel strips was considered with emphasis on the distribution of residual hydrostatic stress developed during temper rolling. In order to assess residual stress distribution produced by the temper rolling, a three-dimensional model was first employed. Then, samples were rolled at a reduction of 4% under single and double pass rolling programmes and the kinetics of static strain aging phenomenon as well as the required activation energies were then evaluated using hardness and tensile tests on the deformed samples. Considering the predicted residual hydrostatic stress distribution, it was found that tensile hydrostatic stresses... 

The influence of annealing treatment on macro- and micro-texture of cold-rolled FeCo-7.15V ferro-magnetic ultra-thin foils were studied. The microstructural studies performed by field emission scanning electron microscope (FE-SEM) showed the formation of paramagnetic precipitations ((Fe, Co)3V) during annealing. During cold rolling of the FeCo-7.15V magnet, the texture components of type (113)[110], (001)[110], (111)[110], and (111)[121], all related to α and γ-fibers were formed. X-ray diffraction (XRD) and local texture measurements performed by electron backscatter diffraction (EBSD) were made on the annealed samples. Both methods revealed that the recrystallized samples have texture... 

Purpose - The purpose of this paper is to study the kinetics of static recovery in cold-rolled aluminum alloy under different heating rates. Design/methodology/approach - Deformation modeling was first performed to assess the distributions of plastic strain and stress within the deformed alloy. In the next stage, thermal analysis and the rate equation of static recovery were employed to determine the progress of static recovery under non-isothermal conditions. Accordingly, a thermal finite element analysis and the Runge-Kutta method were utilized to handle the transient heat conduction and the progress of static recovery. Finally, low temperature annealing heat treatments were conducted to... 

Here in this research, we report on surface engineering of bulk Cu2O photocathode thorough employing nanostructured materials. Nanorods (NRs) of copper oxide with average lengths of 150 nm have been synthesized by anodization of Cu foil in aqueous KOH electrolyte, followed by annealing treatment. Several heating processes were examined to reach pure Cu2O nanostructures and lastly the moderate annealing procedure at 700 °C under Ar gas flow resulted in pure Cu2O nanostructures, confirmed by XRD analysis. Surface modified nanorod/bulk Cu2O electrode was prepared by spin coating of sediments suspension of anodized drop on bulk Cu2O film fabricated through thermal oxidation method, followed by... 

Stress-relieved Al-Mn-Si specimens were constrained groove pressed (CGPed) and in the following, cold-rolled under different strains of 0.47, 0.8 and 1.27. Dual strained sheets were isothermally heat treated at 150, 250, and 350 °C. Microstructure survey revealed that generated shear-bands by CGP acted as talent sites for further strain-induced grain boundary migration (SIGBM) during annealing. SEM micrographs pointed out that coarse particles (1 μm <) had not preferential positions within the aluminum matrix and often comminuted into fine dispersoids (0.5 μm >) under heavy strains. Assessment of the softening fraction (Rrec) depicted that greater accumulated strains along with higher... 

NiTi shape memory alloy (SMA) ingots were produced by vacuum induction melting/casting unit. The effect of microstructure on the hot (1000C) and cold (room temperature) rolling workability of cast samples was investigated. Microstructure of the cast samples was related to the type of crucible which used for melting and the average vacuum pressure of VIM furnace. Optical microscope, scanning electron microscope (SEM), and energy dispersive technology (EDS) methods were used to inspect the origins of observed cracks after rolling processes. The results showed that the formation of both Ti4Ni2O and TiC impurities formed due to inappropriate melting conditions had detrimental effects on... 

Relationship between microstructure and mechanical properties of transient liquid phase-bonded joints of GTD-111 nickel-base superalloy using a Ni-Si-B interlayer was investigated. Shear strength and hardness profile of the joints were discussed with respect to the bond microstructure. In the bonding condition, in which isothermal solidification has not been accomplished completely, eutectic constituent which has the highest hardness in the bond region is the preferential failure source. Additionally, it was found that when isothermal solidification is completed, the extent of γ′ formation in the bond region is the controlling factor for joint strength. Shear strength of bonds after... 

This study investigates the effect of cold rolling prior to inter-critical annealing on microstructure and mechanical properties of ferrite-martensite dual phase steel. Samples were heated to 850 °C for 1 h followed by oil quenching, then the steel sheet were cold rolled by 0%,10%,15% and 20% reduction in thickness. The inter-critical annealing treatment (750 °C, 120min) was performed to generate a ferrite-martensite microstructure. Microstructural studies showed that increasing the applied cold rolling, leading to increase in volume fraction of martensite and decrease in ferrite grain size. Mechanical properties of dual phase steel were measured by tensile, impact and hardness tests.... 

Ni-Co/SiC nanocomposite coatings were electrodeposited in a modified watt type of Ni-Co bath containing 20 nm SiC particles to be codeposited. Potentiodynamic polarization tests were conducted to study the effect of the SiC particulates on the electrodeposition of Ni and Co. Scanning electron microscopy was used to assess the morphology of the Ni-Co alloy and Ni-Co/SiC nanocomposite coatings. The distribution of the particulates in the matrix was considered by means of transmission electron microscopy. Applying nanomechanical testing instruments coupled to atomic force microscopy, mechanical properties of the alloy and composite coatings were studied and compared. The presence of 11 vol.%...