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Showing 28 results for Aluminium

Mirfakhraee B., Eshraghi H., Sar Poulaki H.,
Volume 2, Issue 1 (3-2005)
Abstract

Effect of MgO addition on reaction sintering of aluminium titanate was investigated using equimolar Al2O3 and TiO2 after firing the samples at 1400 C for four hours. Results showed that MgO addition enhanced the sintering process by magnesium aluminates formation, which led to lower porosity and improved densification of the samples. Physical and mechanical properties showed that samples containing 5 wt% MgO was the optimum composition.
Razaghian A., Yu D., Chandra T.,
Volume 2, Issue 3 (9-2005)
Abstract

Fracture behavior of a 7075 aluminium alloy reinforced with 15 Vol%. SiC particles was studied after T6 and annealing heat treatments under uniaxial tensile loading at room temperature. The scanning electron microscopy of fractured surfaces and EDS analysis showed:, that fracture mechanism changed from due mainly to fractured particle in T6 condition to interface decohesion in samples in annealed state. Different fracture mechanisms in annealed and T6 conditions can be ascribed mainly to the significant difference in the stress concentration levels around the particles. In T6 condition, very high local stress sufficient to cause fracture of particle can be generated during loading, while the presence of large precipitates at the particle/matrix interface produced interface decohesion leading to final fracture in the annealed state.
Zhang S.,
Volume 2, Issue 3 (9-2005)
Abstract

Hydration behavior and antioxidising effect of aluminium (AI) powder has been investigated. Bayerite Al (OH) 3 product layers formed on Al in pure water at 25-45°C were porous, so the hydration rate, although very slow at 25°C, increased rapidly with increasing temperature from 25 to 45°C. On further increasing temperature from 45 to 95°C, initial hydration rate increased, but changed little over long hydration periods due to formation of denser and more continuous product layers. At 100?C, due to rapid water-evaporation, hydration product layers (composed of Al (OH)3 and a small amount of boehmite AlO (OH) became detached from the Al surfaces, so offering less protection, so that the hydration rate of Al increased markedly. The presence of MgO or calcium aluminate cement (CAC) in water did not change the hydration product, but greatly accelerate the hydration rate of AI. Addition of even a small amount (e.g. 0.25 wt% of Al amount) of MgO or CAC to water accelerated significantly the hydration of Al, and with increasing level of MgO or CAC, the hydration extent increased markedly. Sol-gel Si02 coatings on Al were useful in improving the hydration resistance of Al, and did not have a negative effect on the behavior of Al as an antioxidant.
Seyyed Masood Bagheri , Jamal Zamani, Ali Mehdipour Omrani,
Volume 6, Issue 4 (12-2009)
Abstract

Abstract: The purpose of this study is to produce scarf joint through explosive welding process (EXW). The scarf weld is a process in which the final bond interface is oblique. With applying the explosive welding technique, this joint can create a metallic bond between similar or dissimilar metals. In this study, chamfered end of aluminum and copper plates were joined explosively and named scarf joint, employing changes in chamfered angle at different stand-off distance and explosive loading. The geometry of scarf joint enables consideration of both flyer and base plate thickness and explosive loading and the effects on mechanical properties of interface such as bond shear strength and micro-hardness can be investigated. Mathematical models developed for the interface properties of scarf joint to make relationship between the bond shear strength and explosive loading ratio. To check the adequacy of developed models, mechanical properties of interface, such as bond shear strength, predicted and compared with actual values in explosive cladding process. The results show reasonable agreement with theoretical predictions. Consequently, mathematical model which is based on scarf joints, can predict bond shear strength of cladding metals under desired explosive loading and flyer plate thickness
B. Tolaminejad, A. Karimi Taheri, H. Arabi, M. Shahmiri,
Volume 6, Issue 4 (12-2009)
Abstract

Abstract: Equal channel angular extrusion (ECAE) is a promising technique for production of ultra fine-grain (UFG) materials of few hundred nanometers size. In this research, the grain refinement of aluminium strip is accelerated by sandwiching it between two copper strips and then subjecting the three strips to ECAE process simultaneously. The loosely packed copper-aluminium-copper laminated billet was passed through ECAE die up to 8 passes using the Bc route. Then, tensile properties and some microstructural characteristics of the aluminium layer were evaluated. The scanning and transmission electron microscopes, and X-ray diffraction were used to characterize the microstructure. The results show that the yield stress of middle layer (Al) is increased significantly by about four times after application of ECAE throughout the four consecutive passes and then it is slightly decreased when more ECAE passes are applied. An ultra fine grain within the range of 500 to 600 nm was obtained in the Al layer by increasing the thickness of the copper layers. It was observed that the reduction of grain size in the aluminium layer is nearly 55% more than that of a ECA-extruded single layer aluminium billet, i.e. extruding a single aluminium strip or a billet without any clad for the same amount of deformation. This behaviour was attributed to the higher rates of dislocations interaction and cell formation and texture development during the ECAE of the laminated composite compared to those of a single billet
Arash Yazdani, Mansour Soltanieh, Hossein Aghajani,
Volume 6, Issue 4 (12-2009)
Abstract

Abstract: In this research plasma nitriding of pure aluminium and effect of iron elemental alloy on the formation and growth of aluminium nitride was investigated. Also corrosion properties of formed AlN were investigated. After preparation, the samples were plasma nitrided at 550oC, for 6, 9 and 12 h and a gas mixture of 25%H2-75%N2. The microstructure and phases analysis were investigated using scanning electron microscopy and X-ray diffraction analysis. Moreover corrosion resistance of samples was investigated using polarization techniques. The results showed that only a compound layer was formed on the surface of samples and no diffusion zone was detected. Dominant phase in compound layer was AlN. Scanning electron microscopy results showed that nitride layer has particulate structure. These nitrided particles have grown columnar and perpendicular to the surface. It was also observed that the existence of iron in the samples increases the nitrogen diffusion, thus growth rate of iron containing nitrides are higher than the others. Corrosion tests results showed that formation of an aluminium nitride layer on the surface of aluminium decreases the corrosion resistance of aluminium significantly. This is due to elimination of surface oxide layer and propagation of cracks in the formed nitride layer
A. H. Shafie Farhood, F. Akhlaghi,
Volume 7, Issue 1 (3-2010)
Abstract

Abstract:

structures in alloys. This method is based on pouring the melt through a small sized nozzle into a mould located at a

certain height under the crucible. This simple method generates globular structures without using equipments such as

impellers, electromagnetic stirrers, ultrasonic probes and cooling slopes. Therefore it is cost effective. In the present

study, the effect of casting size and mould casting modulus on the globular structure evolution in A356 aluminium alloy

specimens prepared by NMS process was investigated. The results showed that regardless of the different casting

modulus and their sizes, all the specimens exhibited globular structures. However, the size and shape factor of the

globules decreased with increased casting modulus and casting size indicating the influential effect of the surface area

of the mould in generating globular structures in this process.

Narrow Melt Stream (NMS) is a relatively new semisolid metal processing technique for producing globular

N. Anjabin, Karimi Taheri,
Volume 7, Issue 2 (6-2010)
Abstract

Abstract:

properties of AA6082 aluminum alloy. Considering that aging phenomenon affects the distribution of alloying element

in matrix, and the fact that different distribution of alloying elements has different impediments to dislocation

movement, a material model based on microstructure, has been developed in this research. A relative volume fraction

or mean radius of precipitations is introduced into the flow stress by using the appropriate relationships. The GA-based

optimization technique is used to evaluate the material constants within the equations from the uni-axial tensile test

data of AA6082 alloy. Finally, using the proposed model with optimized constants, the flow behavior of the alloy at

different conditions of heat treatment is predicted. The results predicted by the model showed a good agreement with

experimental data, indicating the capability of the model in prediction of the material flow behavior after different heat

treatment cycles. Also, the calculated flow stress was used for determination of the material property in Abaqus

Software to analyze the uniaxial compression test. The force- displacement curves of the analysis were compared to

the experimental data obtained in the same condition, and a good agreement was found between the two sets of results.

A novel constitutive equation has been proposed to predict the effect of aging treatment on mechanical

F. Gulshan, Q. Ahsan,
Volume 10, Issue 2 (6-2013)
Abstract

The probable reasons for evolution of weld porosity and solidification cracking and the structure- property relationship in aluminium welds were investigated. Aluminium plates (1xxx series) were welded by Tungsten Inert Gas (TIG) welding process, 5356 filler metal was used and heat input was controlled by varying welding current (145A, 175A and 195A). The welded samples were examined under optical and scanning electron microscopes and mechanical tests were performed to determine tensile and impact strengths. Secondary phase, identified as globules of Mg2Al3 precipitates, was found to be formed. Solidification cracking appeared in the heat affected zone (HAZ) and porosities were found at the weld portion. The tendency for the formation of solidification cracking and weld porosities decreased with increased welding current.
M. S. Kaiser,
Volume 10, Issue 3 (9-2013)
Abstract

Precipitation behaviour of wrought Al-6Mg alloys with ternary scandium and quaternary zirconium and titanium has been studied. Hardness measurements and resistivity studies are employed to assess the precipitation behaviour of scandium doped Al-6Mg alloy without or with quaternary additions of zirconium and titanium. Further, the kinetics of precipitations are studied by differential scanning calorimetric technique. Scandium has been observed to form fine coherent Al3Sc precipitates during ageing and these are responsible for strengthening of the alloys. The precipitation kinetics of Al3Sc depends on the diffusion of scandium in aluminium. Presence of fine coherent precipitates of Al3Sc impedes the migration of dislocations and increase the recovery temperature. The kinetics of recrystallisation is also delayed.
K. Tavighi, M. Emamy, A. R. Emami,
Volume 11, Issue 4 (12-2014)
Abstract

This study was undertaken to investigate the effects of Cu and solution heat treatment on the microstructure and hardness of cast Al-Al4Sr metal matrix composite. Different amounts of Cu (0.3, 0.5, 1, 3 and 5 wt.%) were added to the composite. Specimens were heat treated at 500 °C for 4 hours followed by water quenching. Microstructural studies were assessed by the use of optical microscope, scanning electron microscope (SEM) and x-ray diffractometry (XRD). The results showed that addition of 5 wt.% Cu reduces the length of large needle-like Al4Sr phase and refines the microstructure. In addition, the presence of Cu-intermetallics increases hardness of the composite. Cu mainly forms θ phase which segregates at the grain boundaries. Heat treatment partially dissolves Cu-intermetallics and homogenizes the distribution of θ phase in the matrix.
E. Badami, M. T. Salehi, S. H. Seyedein,
Volume 11, Issue 4 (12-2014)
Abstract

Hot deformation behavior of a medium Cr/Mn Al6061 aluminum alloy was studied by isothermal compression test at temperatures range of 320 to 480 °C and strain rates range of 0.001 to 0.1 s −1. The true stresstrue strain curves were analyzed to characterize the flow stress of Al6061. Plastic behavior, as a function of both temperature and strain rate for Al6061, was also modeled using a hyperbolic sinusoidal type equation. For different values of material constant α in the range of 0.001 to 0.4, values of A, n and Q were calculated based on mathematical relationships. The best data fit with minimum error was applied to define constitutive equation for the alloy. The predicted results of the proposed model were found to be in reasonable agreement with the experimental results, which could be used to predict the required deformation forces in hot deformation processes
A. Fattah-Alhosseini, M. Ranjbaran, S. Vajdi Vahid,
Volume 12, Issue 2 (6-2015)
Abstract

In this study, corrosion behaviour of A356-10 vol.% SiC composites casted by gravity and squeeze casting is evaluated. For this purpose, prepared samples were immersed in HCl solution for 1h at open circuit potential. Tafel polarization and electrochemical impedance spectroscopy (EIS) were carried out to study the corrosion resistance of composites. The Tafel polarization and EIS studies of the corrosion behaviour of the A356-10 vol.% SiC composites showed that the corrosion resistance of the composite casted by squeeze casting was higher than that of the composites casted by gravity in selected corrosion media. Also, the Tafel polarization and EIS studies revealed that the corrosion current densities of both composites increase with the increase in the concentration of HCl. The micrographs of scanning electron microscope (SEM) clearly showed the squeeze casting composite exhibits a good dispersion/matrix interface compared to that of the composites produced by gravity casting
M. Abbas, S. Nisar, A. Shah, F. Imtiaz Khan,
Volume 12, Issue 2 (6-2015)
Abstract

Aluminium base alloy (Al-Cu-Si) was reinforced with silicon carbide (SiC) particles, in various percentage compositions from 0-20 wt%. Silicon carbide particle size of 20µm was selected. The molten slurry of SiC reinforced base aluminium metal was casted through green and dry sand casting methods and solidification process was carried out under ambient conditions. A selected population of total casted samples were subjected to T6 heat treatment process, followed by evaluation of mechanical properties of hardness, tensile strength and impact loading. The micro sized SiC particles were preheated up to 300C prior pouring into the melted metal, for subsequent removal of residual gases and moisture content. A continuous manual stirring method was used for homogenous distribution of reinforced particle in molten slurry. The experimental results revealed that the highest parameters of hardness, impact energy and tensile strength were achieved in the T6 heat treated specimens having highest percentage composition (20%) of Silicon Carbide (SiC) particles
D. Gharailou, A. Abbasi,
Volume 12, Issue 3 (9-2015)
Abstract

Effect of electro migration on crystal structures of platinum nanowire (Nano bridge) during Nano-gap formation is investigated by means of Transmission Electron Microscopy (TEM). Selected area diffraction patterns as well as bright field images are used for this investigation. There were severely recessions in the polycrystalline Nano bridge and crystal structures around the nanogap changed completely during electro migration. Due to Joule heating, original small crystal with random orientation disappeared and newly crystals with a preferred orientation grew. They have [111] orientations (respect to beam direction) with slight misorientations. α and θ was defined to calculate the misorientation and used to represent Nano-gap formation mechanism. The calculation gives the breaking of Nano bridge occurred along grain boundaries in most of Nano bridges. The controlling system during eletromigration may affect on the shapes of tips so that the shape of tips in Nano bridges, in which feedback control is applied, is more symmetric than others. The effect of temperature on atomic diffusivity might be the reason of the behaviour. {422} could be a preferred surface plane for mass transport in platinum Nano bridge in which atoms move along it
M. Amuei, M. Emamy, R. Khorshidi, A. Akrami,
Volume 12, Issue 3 (9-2015)
Abstract

In this study, Al2014 alloy refined with Al-5%Ti-1%B master alloy was prepared by strain-induced melt activated (SIMA) process. The main variables of the SIMA process were cold working, holding time and temperature in semi-solid state. Cold working was applied on specimens by upsetting technique to achieve 10%, 20% and 30% height reduction. Cold worked specimens were heat treated in semi-solid state at 585 °C, 595 °C, 605 °C, 615 °C, 625 °C and 635 °C and were kept in these temperatures for different times (20 and 30 min). Observations through optical and scanning electron microscopy were used to study the microstructural evaluation. The results revealed that fine and globular microstructures are obtained by applying 30 % height reduction percentage and heat treating in 625 °C for 30 min. Comparison between refined and unrefined Al2014 alloy after applying SIMA process showed that Al-5%Ti-1%B master alloy has no significant effect on average globule size but makes the final structure more globular.
E. Khoshomid Aghdam, R. Naghizadeh, H. R. Rezaie,
Volume 12, Issue 3 (9-2015)
Abstract

MgAl2O4/Ti(C,N) composites were synthesized through aluminothermic reaction between Al,TiO 2,MgO powders and phenolic resin in coke bed condition. Effect of addition of carbon black and sugar into the mixture at different temperatures were investigated. The phases and microstructures of samples were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). MgAl 2O4 /Ti(C,N) composites without additive were obtained after heat treatment at 1600˚C. With addition of carbon black TiC, TiN and Ti(C,N) were appeared after firing at 1400˚C and formation of spinel/Ti(C,N) composites were completed at 1600˚C. In sample containing sugar, MgAl2O4 -Ti(C,N) composite were completely synthesized at 1400˚C. In this sample crystallite size of Ti(C,N) were 32 nm and carbon content of titanium carbonitride (Ti(C,N)) reached to 0.442 value.
A. Abbasian, M. Kashefi, E. Ahmadzade-Beiraki,
Volume 12, Issue 3 (9-2015)
Abstract

Precipitation hardening is the most common method in the strengthening of aluminium alloys. This method relies on the decrease of solid solubility with temperature reduction to produce fine precipitations which impede the movement of dislocations. The quality control of aluminium alloy specimens is an important concern of engineers. Among different methods, non-destructive techniques are the fastest, cheapest and able to be used for all of parts in a production line. To assess the ability of eddy current as a non-destructive method in the evaluation of precipitation hardening of aluminium alloys, 7075 aluminium alloy specimens were solution treated at 480°C for 1 hr. and followed by water quenching. Afterwards, the specimens were aged at different temperatures of 200, 170, 140, 110 and 80°C for 8 hr. Eddy current measurements was conducted on the aged specimens. Hardness measurement and tensile test were employed to investigate the mechanical properties. It was demonstrated that eddy current is effectively able to separate the specimens with different aging degree due to the change of electrical conductivity during aging process
E. Barati, Kh. Farmanesh,
Volume 12, Issue 4 (12-2015)
Abstract

The purpose of this research is to achieve the optimal parameters for producing forged aluminium alloy 7075 aircraft door bracket by using finite element modelling (FEM) with commercial DEFORM-3D V6.1 and physical simulations with plasticine and Plexiglas dies. Also, forging speed has been examined as the main factor for controlling to produce a part without any defects. The results of Physical Simulation showed that the flow pattern has good agreement with the results of FEM that based on the use of hydraulic presses with initial billet and dies temperatures 410 and 400 ° C, respectively, and different forging speeds 5, 10 and 15 mm/sec. Distribution of effective strain rate, effective strain, effective stress, temperature , forging force and dies­ wear showed improvement the results in forging speed of 5 mm/sec. Processing map of Aluminium alloy 7075 also checked out at constant strain 0.5, indicated that the specified area of the forged part is located in a safe area. Forging force in optimized forging speed 5 mm/sec showed that the forging process using a 1000-ton press can be done easily


E. Gharibshahiyan, A. Honarbakhsh Raouf,
Volume 13, Issue 4 (12-2016)
Abstract

Friction welding is widely used in various industries. In friction welding, heat is generated by conversion of mechanical energy into thermal energy at the interface the work pieces during pin rotation under pressure. A three-dimensional thermo mechanical simulation of friction stir welding (FSW) processes is carried out for Aluminium Alloys of 6061and 7050 where the simulation results are compared directly with the measured temperature histories during FSW after process. The objective of the present work is to study and predict the heat transient generated in alloy aluminium plate welded by FSW method. A three dimensional model was developed by LS-Dyna software and heat cycles have been proposed during the welding of aluminium alloys 6061 and 7050. In this research, the simulations were carried out with linear velocity in the range of 140 to 225 mm/min and pin rotational speeds of 390 and 500 rpm. Increase in pin rotational speed, from 390 to 500 rpm, resulted in greater temperatures which translated to rise of recorded temperature of top and bottom of the specimens. This is in turn to a wider HAZ. In addition, it was observed that raising the linear velocity had an opposite effect. Finally, results of experimental and numerical data were correlated and validated



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