Aluminum Alloys Research Papers - Academia.edu (original) (raw)

Premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder was analyzed as matrix in this research. Gas atomized powder Al-9Si with
20% volume fraction of SiC particles was used as reinforcement and added into the alloy with varied concentration. Mix
powders were compacted by dual action press with compaction pressure of 700 MPa. High volume fraction of SiC particles
gave lower green density due to resistance of SiC particles to plastic deformation during compaction process and resulted voids
between particles and this might reduce sinterability of this mix powder. Sintering was carried out under ultra high purity
nitrogen gas from 565◦
-580◦C for 1 hour. High content of premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder gave better sintering
density and reached up to 98% relative. Void between particles, oxide layer on aluminum powder and lower wettability between
matrix and reinforcement particles lead to uncompleted liquid phase sintering, and resulted on lower sintering density and
mechanical properties on powder with high content of SiC particles. Mix powder with wt90% of Alumix 431D and wt10% of
Al-9Si-vf20SiC powder gave higher tensile strength compare to another mix powder for 270 MPa. From chemical compositions,
sintering precipitates might form after sintering such as MgZn2, CuAl2 and Mg2Si. X-ray diffraction, DSC-TGA, and SEM
were used to characterize these materials.

- by
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- Sintering, Powder Metallurgy, Composites, Silicon Carbide
- by A.K., Vasudevan and +1
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- Mechanical Engineering, Civil Engineering, Titanium, Fatigue

Rotary degassing is one of the most frequently used melt treatment technologies used for processing liquid aluminum alloys. Despite this, the information available about the possible effects of this method on the double oxide-and nitride film (bifilm) content, especially when using different purging gases, is quite limited. For this reason, in this study, the effects of multiple rotary degassing treatments conducted with N 2 and Ar purging gases on the bifilm quantity of a casting aluminum alloy were compared. The characterization of the melt quality was realized by the computed tomographic (CT) analysis of reduced pressure test (RPT) specimens, image analysis, and scanning electron microscopy (SEM) of the fracture surfaces of K-mold samples. Based on the results, by the application of Ar as a purging gas, relatively low bifilm content can be achieved. On the other hand, while the use of N 2 leads to the formation of numerous small-sized nitride bifilms, which significantly increased the pore number density inside the RPT specimens. This can be associated with the nitride formation by the chemical reaction between the liquid aluminum alloy and the N 2 purging gas bubbles during the degassing treatments.

The paper provides an overview of tribological properties of nanocomposites with aluminium matrix. Nanocomposites represent a new generation of composite materials with better properties than conventional composite materials. The paper presents and explains the most common methods of nanocomposites production. In addition, the overview of tribological properties is presented through the equipment used for testing; amount, size and type of reinforcement; matrix material and manufacturing process; and test conditions. ARTICLE HISTORY Received 15 August 2016 Accepted 3 September 2016 Available online 30 September 2016

- by Mariem Prm
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- Aluminum Alloys, Chimie industrielle

The present study is aimed to understand the influence of dynamic precipitation on the low cycle fatigue (LCF) behavior of an under-aged (UA) AA6063 Al–Mg–Si alloy. This was accomplished by the estimation of plastic strain energy density (PSED) at varied isolated cycles during LCF of the UA alloy with subsequent comparison of these results with those of peak-aged (PA) and over-aged (OA) ones. The LCF tests of the UA alloy were carried out in the range of strain amplitudes of 0.2–1.0 % together with the evolution of hardness and tensile properties. The UA alloy shows Masing behavior, evaluated in terms of the variation of Bauschinger strain with plastic strain amplitude, and exhibits continuous hardening till failure unlike the PA and OA alloys. Higher average PSED value for the UA alloy in comparison to that for the PA and the OA alloys indicates dynamic precipitation during cycling; the magnitudes of average PSED were calculated using a proposed method. In addition, pronounced increase in the post LCF hardness values substantiate the dynamic precipitation.

- by Supriya Nandy and +3
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- Phase Transformations, Mechanics of Fracture, Fatigue and Damage, Aluminum Alloys, Deformation Microstructure

Dry sliding wear behavior of electroless nickel-phosphorus (EN) coating of thickness ~35 μm deposited on a 7075-T6 aluminum alloy was studied. EN was deposited from a bath with sodium hypophosphite as a reducing agent. In as-deposited conditions, plating with 6-9 wt.% phosphorus has a mixture of amorphous and microcrystalline phase. Three pretreatments of Zn (zincate), Ni strike and absorbed hypophosphite layer were given to the substrate before EN coating to examine their wear performance. The surface morphology of the pretreatments was studied by a confocal laser scanning microscope. The performances of these pretreatments of EN were evaluated by dry sliding wear studies and followed by SEM studies. The results suggest that the wear behavior of EN mostly depends on the pretreatment conditions. Heat treatment at temperature of 400 °C can enhance the wear resistance properties for all types of pretreatment conditioned samples and in addition that the average coefficient of friction of 400 °C specimens (μav) had minimum value as compared to 200 °C specimens. Ni strike provided better interlocking adhesion between EN and Al and this pretreatment noticeably improved the wear, frictional and hardness behavior of the EN coatings on 7075 Al substrate and further enhanced it by heat treatment of 400 °C/h.

- by Sudagar Jothi
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- Use Wear Analysis, Corrosion, Casting, Aluminum

Grain refinement plays a crucial role in improving characteristics and properties of cast and wrought aluminum alloys. Generally Al–Ti, Al–Ti–B and Al–Ti–C master alloys are added to the aluminum alloys to grain refine the solidified product. Grain refiners are considered to provide benefits as improved feeding characteristics and castings speed in direct chill (DC) castings, uniform distribution of elements and improved homogeneity; reduce and evenly distributed porosity; elimination of hot tearing. These microstructural changes led to improve mechanical properties and increased machinability. Similarly Al-Sr master alloy as grain modifiers is used to modify the commercial Al-Si Alloy. The present paper attempts to review the effects of grain refinement and modifiers in the casthouse applications

- by aly el domiaty
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- Mechanical Engineering, Energy, Friction Stir Welding, Aluminum Alloys

Aluminium alloys are widely used in automotive industries. This is particularly due to the real need to weight saving for more reduction of fuel consumption. The typical alloying elements are copper, magnesium, manganese, silicon, and zinc. Surfaces of aluminium alloys have a brilliant lustre in dry environment due to the formation of a shielding
layer of aluminium oxide. Aluminium alloys of the 4xxx, 5xxx and 6xxx series, containing major elemental additives of Mg and Si, are now being used to replace steel panels in various automobile industries. In this work we are interested to investigate the mechanical properties of aluminium alloy by varying the percentage of silicon. The results showed that with the increasing of silicon content the solidification time increased, as also a decreasing the liquids temperature. The tensile strength of aluminium alloy is increased with increased silicon
content up to 6 %.

- by husain mehdi
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- Aluminum Alloys
- by Hm Mohyaldeen
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- Materials Science, Mechanical properties, Solidification, Aluminum Alloys

This article highlights and focuses on laser beam machining (LBM) of aluminum and its alloys. It begins by providing a brief overview of various conventional (chip forming) and nonconventional machining techniques employed for aluminum-based materials. Later, it explicitly provides features of LBM techniques employed for aluminum and its alloys for different types of machining.

This chapter reviews different coatings used on aluminum alloys.

- by ATUL TIWARI
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- Corrosion, Surface Coatings, Aluminum Alloys, Silicone

Ever more stringent regulations on greenhouse gas emissions from transportation
motivate efforts to revisit materials used for vehicles1. High-strength aluminium alloys
often used in aircrafts could help reduce the weight of automobiles, but are
susceptible to environmental degradation2,3. Hydrogen ‘embrittlement’ is often
indicated as the main culprit4; however, the exact mechanisms underpinning failure
are not precisely known: atomic-scale analysis of H inside an alloy remains a challenge,
and this prevents deploying alloy design strategies to enhance the durability of the
materials. Here we performed near-atomic-scale analysis of H trapped in
second-phase particles and at grain boundaries in a high-strength 7xxx Al alloy. We
used these observations to guide atomistic ab initio calculations, which show that the
co-segregation of alloying elements and H favours grain boundary decohesion, and
the strong partitioning of H into the second-phase particles removes solute H from
the matrix, hence preventing H embrittlement. Our insights further advance the
mechanistic understanding of H-assisted embrittlement in Al alloys, emphasizing the
role of H traps in minimizing cracking and guiding new alloy design.

Strict requirements that are put on mechanical constructions from the aspect of increase of exploitation periods and reduction of their weights, therefore of
their prices as well, implicate developments and applications of new composite materials with matrices of lightweight metals. Composite materials with
metal matrices are used for engine cylinders, pistons, disc and drum brakes, Cardan shafts and for other elements in automotive and aviation industry. The
most important type of metallic materials is composite materials with matrices of aluminium alloys due to a set of their beneficial properties. Improvement
of mechanical, especially tribological properties of hybrid composites were provided by the use of certain reinforce materials such as SiC, Al2O3 and
graphite in defined weight or volumetric share. New developed hybrid composites with aluminium matrices have significantly higher resistance to wear,
higher specific stiffness and higher resistance to fatigue. By the increase of quantities of produced elements made of hybrid composites, decrease of their
prices is induced that even further enlarge their applications. The applications of aluminium hybrid composites are considered from the aspect and with
the focus on automotive industry

The relationship between microstructure and properties is not widely assessed in parts produced by additive manufacturing, particularly for aluminum. These relationships can be used by engineers to develop new materials, additive processes, and additively manufactured parts for a variety of applications. Thus, the tensile, compressive, and microstructural properties of common aluminum weld filler alloys (ER1100, ER4043, ER4943, ER4047, and ER5356) were evaluated following gas metal arc weld (GMAW)-based metal 3-D printing to identify optimal alloy systems for this type of additive manufacturing. The porosities in all test specimens were found to be less than 2%, with interdendritic shrinkage in 4000 series alloys vs. intergranular shrinkage in 5356. The 4000 series alloys performed better than 1100 and 5356 with respect to printed bead width, porosity, strength, and defect sensitivity. In comparison to standard wrought and weld alloys, the 3-D printed specimens exhibited similar or superior mechanical properties with only minor exceptions. Long print times allow for stress relieving and annealing that improved the print properties of the 4000 series and 5356 alloys. Overall the GMAW-based 3-D parts printed from aluminum alloys exhibited similar mechanical properties to those fabricated using more conventional processing techniques.

- by Joshua Pearce
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- Engineering, Materials Engineering, Mechanical Engineering, Materials Science

This work studies the quench-induced precipitation during continuous cooling of five Al-Mg-Si alloys over a wide range of cooling rates of 0.05-2 • 10 4 K/min using Differential Scanning Calorimetry (DSC), X-ray diffraction, optical-(OM), transmission electron-(TEM) and scanning electron microscopy (SEM) plus hardness testing. The DSC data shows that the cooling reactions are dominated by a high temperature reaction (typically 500 °C down to 380 °C) and a lower temperature reaction (380 °C down to 250 °C), and the microstructural analysis shows they are Mg2Si phase formation and B' phase precipitation, respectively. A new, physically-based model is designed to model the precipitation during the quenching as well as the strength after cooling and after subsequent age hardening. After fitting of parameters, the highly efficient model allows to predict accurately the measured quench sensitivity, the volume fractions of quench induced precipitates, enthalpy changes in the quenched sample and hardness values. Thereby the model can be used to optimise alloy and/or process design by exploiting the full age hardening potential of the alloys choosing the appropriate alloy composition and/ or cooling process. Moreover, the model can be implemented in FEM tools to predict the mechanical properties of complex parts after cooling.

- by Benjamin Milkereit
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- Kinetics, Differential scanning calorimetry, DSC, Aluminum Alloys

Alloy development can simplify low-cost gas metal arc weld (GMAW)-based 3-D printing by making it easier to print quality parts with minimal metallurgical or welding experience. Previous work found good properties in aluminum alloys, particularly in the aluminum-silicon 4943 (Al-5.5%Si-0.4%Mg) and 4047 (Al-11.6%Si) alloys. These alloys were easy to print, but could benefit from alloying to increase ductility and to minimize or redistribute porosity. The purpose of this study was to modify 4943 and 4047 alloys and rapidly screen their performance for use as feedstock for improved 3-D printability. The 4047 and 4943-based alloys were modified with additions of magnesium, strontium, titanium boride, and combinations thereof. Wedge-shaped castings were used to efficiently screen alloying additions over the same ranges of solidification rates as those observed in GMAW-based 3-D printing. The alloying additions were most effective at modifying the high-silicon 4047 alloy whereas no change in microstructure was observed in the low-silicon 4943 alloy. Strontium was an effective modifier of the high-silicon alloy. Titanium boride was not observed to have a grain refining effect on aluminum dendrites on its own, although the combination of strontium and titanium boride produced the most refined eutectic structure in the high-silicon alloy. Future work should evaluate the singular effects of strontium, titanium boride, and the combination of strontium and titanium boride additions in weld-based 3-D printing.

- by Joshua Pearce
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- Welding Technology, Welding Engineering, 3D printing, Additive Manufacturing

The purpose of this research is to know the effect of Heat Treatment Hardening-Tempering Alloy AlMgSi-Fe12% foundry result to hardness and toughness. The test was carried out on raw material and material test specimen after obtaining Hardening heat treatment at 600 ℃ and quenching with SAE 20 oil medium. While Tempering variation at temperature 200 ℃, temperature 250 ℃ and temperature 300 ℃ with detention time for 15 min at each temperature, each heat treatment. Hardness testing method is done by standard micro Vickers test method with 100 gf loading. The result of raw material testing for hardness value is 60,92 VHN. Test results after heat treatment process at temperature 200 ℃ cause hardness value increased by 63,50 VHN. At temperature 250℃ cause hardness value decreased to 59,94 VHN. At temperature 300 ℃ cause hardness value increase to 76,98 VHN.

- by Wardoyo Wardoyo
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- Casting, Aluminum, Metal Casting, Aluminum Alloys

This article investigates the effects of Cr addition on microstructure, mechanical properties and fluidity of as-cast aluminum (LM6) alloy. Presence of 0.05, 0.1 and 0.15 wt.% Cr were add to LM6 melting greensand cast. There is no relationship between Cr addition and Si morphology. The Cr addition had modified the Fe intermetallics to irregular shapes. The mechanical properties such as toughness and hardness of LM6 had increase with increase the Cr value. The β-phases have largest surface to volume ratio, hence they have the largest interfacial region with the melt and are the most detrimental intermetallic to the fluidity. The sludge formation and consuming Si and shifts the local chemical composition of the melt to the aluminum side of the phase diagram increase with Cr addition, which has lower fluidity than base alloy.

- by Madridge Journals
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- Microstructure, Aluminum Alloys, LM6 alloy, Chromuim

Over the past decade thermomechanical models of the direct chill (DC) casting process have been developed in an effort to mitigate casting defects such as hot tearing as well as to develop a more scientific understanding of the thermal stress and strains which develop during the casting process. A key input to these models is the constitutive behavior of the material in the solid state under thermomechanical conditions that are typical of those experienced during DC casting (strain rates from 1 × 10−1 s−1 to 1 × 10−5 s−1 and temperatures from solidus down to room temperature). This research work presents use of an empirical model (the extended Ludwik equation) to predict the high and low temperature constitutive behavior of aluminum alloys in the solid state under deformation conditions relevant for DC casting. The effect of temperature, strain and strain rate has been studied for three commercially important alloys, namely: AA3104, AA5182 and AA6111. Material parameters used in the constitutive equation were calculated based on experimental measurements using a Gleeble 3500. To validate the constitutive equations developed, complex thermomechanical history tests were performed using the Gleeble 3500 that more closely resemble those experienced by the material during industrial DC casting. These measurements were then compared to the material response based on an ABAQUS finite element (FE) simulation of the test which modeled the material behavior using tabular data and included the effects of temperature, strain and strain rate. When using a commercial FE package such as ABAQUS, it was found that strain softening needs to be considered in situations where the temperature is changing during the simulation. An empirical model was developed to account for strain softening which occurs during continuous cooling tests based on the measured work hardening parameter “n”.

- by Alankar Alankar
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- Corrosion, Casting, Aluminum Alloys, Materials Characterization
- by Rafael Colás
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- Casting, Aluminum, Metal Casting, Aluminum Alloys

The cooling rate of aluminum alloy powders prepared by ultrasonic gas atomization process was calculated through the convection heat transfer principle. A simple and theoretical model is established, which can be expressed as vertical bar dT(d)/dt vertical bar =12/rho.C-p . (T-d - T-f) . k(g)/d(2). The average cooling rates of Al-Ni-Ce-Fe-Cu alloy powders prepared by argon gas atomization and by helium gas atomization are about 10(4)similar to 10(7) K/s and 10(5)similar to 10(8) K/s, respectively. The critical cooling rate is calculated to be 3.74 x 10(5) K/s for Al-Ni-Ce-Fe-Cu alloy amorphous powders prepared by argon gas atomization. The cooling rates of gas-atomized powder particles estimated from secondary dendrite arm spacing are in consistence to those predicted from the theoretical model.

- by Sheng Guo
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- Heat Transfer, Amorphous Alloys, Cooling Rate, Gas Atomized Powder

High mechanical properties, fatigue, pressure tight and low porosity are requirements of aluminum cylinder heads and blocks related with the quality of liquid metal. With secondary alloys can be possible to reach these characteristics. But, several control stages are necessary from row material (Al scrap) to final stage: liquid metal in the holder furnace. In order to measure the quality of liquid metal, several samples with the PreFil®-Footprinter Unit were taken along the route of melting process. The tracking of the process include melting at reverberatory furnace, fluxing, liquid treatment and degassing. The results showed areas to improve with operational practices and new degassing equipments and use of fluxes treatment.

- by Eulogio Velasco
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- Aluminum Alloys

Prediction of tribological characteristics of hybrid composites with A356 matrix using artificial neural networks (ANN) was performed in this paper. During experiment next parameters were varied: sliding speed, load, sliding distance and wt.% of reinforcement. The obtained experimental results were used to form the artificial neural network in which were varied number of neurons in the hidden layer, number of layers, the activation function and the function of training. Training of the neural network was performed for the wear rate, and optimal regression coefficient was equal to 0.994, for the network 4-15-10-1. Using neural networks to predict the wear rate greatly reduces the time and cost of experiment.

- by Blaza Stojanovic and +2
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- Engineering, Materials Engineering, Mechanical Engineering, Materials Science

In this work, experimental and numerical analyses of repairs on carbon fiber reinforced epoxy (CFRE) substrates, with CFRE and aluminum alloy doublers typical of aircraft structures, are presented. The substrates have a bridge gap of 12.7 mm (simulated crack), repaired with twin doublers joined with riveted, adhesive bonded, and hybrid joints. The performance of the repairs using different doubler materials and joining techniques are compared under static loading. The experimental results show that riveted joints have the lowest strength, while adhesive bonded joints have the highest strength, irrespective of the doubler material. Finite element analysis (FEA) of the studied joints is also performed using commercial FEA tool Abaqus. In the FEA model, point-based fasteners are used for the rivets, and a cohesive zone contact model is used to simulate the adhesive bond. The FEA results indicate that the riveted joints have higher tensile stresses on the metal doublers compared to the composite doublers. As per the failure modes, interestingly, for hybrid joints using composite doublers, the doublers fail due to net-section failure, while, for hybrid joints using metal doublers, it is the composite substrate that fails due to net-section failure. This suggests vulnerability of the composite structures to mechanical fastener holes. Lastly, the Autodesk Helius composite tool is used for prediction of first-ply failure and ply load distribution, and for progressive failure analysis of the composite substrate.

- by Jose I. Rojas and +1
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- Mechanical Behavior Of Materials, Fatigue, Mechanical properties, Aluminium Alloys

The objective of this research is to study the strain forming limits of Al-Mg alloy (5083) sheet, fabricated by equal channel angular rolling process (ECAR) at room temperature. For this purpose, the ECAR process was executed at room temperature in three passes. Mechanical properties, micro-hardness, and microstructure were investigated after the ECAR process. Uniaxial tensile tests of the ECAR process produced samples and showed that yield and ultimate stresses increase, while the uniform elongation to fracture decreases in comparison with the annealed state. There was a continuous hardness enhancement by increasing the number of the ECAR passes. After the third pass, the amount of hardness raised by 73% in comparison with the annealed sample. In the fourth pass, the hardness reduced slightly, that was attributed to the strain saturation in room temperature and was followed by high surface cracks. In the annealed condition, the average grain size was 45µm, and after the third ECAR pass, this amount was reduced to 10µm. Furthermore, the forming limit diagrams (FLDs) were determined experimentally, using the Nakazima test. The obtained results show that after the third pass, the Post-print of "HR Rahimi, M Sedighi, R Hashemi, (2018) Forming limit diagrams of fine-grained Al 5083 produced by equal channel angular rolling process, Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 232(11), 922-930. https://doi.org/10.1177/1464420716655560 2 FLDs' level move downward, meaning that a reduction occurred in the forming limits of ECARed samples.

- by Emanoil LINUL
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- Steel, Aluminum Alloys, Experimental Tests, Conductors

The presence of inclusions such as oxides, carbides or refractory particles can be harmful to the mechanical and surface characteristics of castings. Inclusion-rich metals result in lower fluidity and feeding capability during casting. Nowadays, solid fluxes are widely used in foundries in order to reduce the inclusion content of aluminium melts. In this study, the effect of four different fluxes on the melt quality was studied. First, the inclusion content of the flux-treated melt, and then the properties of the fluxes (i.e. chemical composition and melting temperature) were examined.

- by Gábor Gyarmati
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- Materials Science, Materials Science and Engineering, Casting, Metal Casting

Investigation of tribological behaviour of the hybrid composite, whose substrate is Al/Si alloy A356, reinforced with 10 wt. (%) of silicon carbide (SiC) and 0 and 5 wt. (%) of graphite (Gr) is presented in this paper by application of the Taguchi method. The composites are obtained by the compocasting procedure. The tribological investigations were realised on the tribometer with the block-on-disc contact pair in lubricating conditions and for the two values of the sliding speed, 0.25 and 1 m/s, two values of load 40 and 120 N and two values of the sliding path, 1200 and 2400 m. The wear traces were measured within the experiment, namely the wear intensities were calculated and results analysis was performed by application of the ANOVA technique. The strongest influence on the wear intensity was exhibited by the normal load (39.05%), then follow wt. (%) of the reinforcer (26.84%), the sliding speed (20.93%) and the sliding path (10.72%). The smallest wear appears in hybrid composite Al/SiC/Gr with 5 wt. (%) of the graphite reinforces, at the lowest load of 40 N, sliding speed of 1 m/s and along the sliding path of 2400 m. The main aim of their study is to provide new information and knowledge about the tribological behaviour of hybrid composites with a base of Al-Si alloy A356 reinforced with 10 wt. (%) SiC and with the addition of 0 and 5 wt.% Gr under lubricated sliding conditions.

- by Blaza Stojanovic
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- Engineering, Materials Engineering, Mechanical Engineering, Materials Science
- by 선기 김
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- Mechanical Engineering, Materials Science, Aluminum Alloys, Continuous Casting
- by aly el domiaty
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- Mechanical Engineering, Energy, Friction Stir Welding, Aluminum Alloys

—In this study, AA5083 aluminum alloy plate of thickness 4mm have been welded by conventional fusion welding process Pulsed Current tungsten inert gas (PCTIG) welding and friction stir welding (FSW) process. The welding process was performed with different process parameters and the joints has been investigated to find their microhardness properties, SEM Images (Scanning Electron Microscope) and Chemical Analysis properties.Vickers hardness tester was used to characterize the hardness of the weld area for both the welding process. Then Scanning Electron microscope is used to analyses the size and shapes of the grains at weld zone and heat affected zone. Taking into consideration the process conditions and requirements, FSW and TIG processes Next test is chemical analysis test on Edax Energy dissipate machine and compared with each other to understand the advantages and disadvantages of the welding processes. Microstructural examination reveals that smaller grain sizes are obtained in the weld centre of FS welded specimens due to recrystallization, where as grain growth has been observed in TIG welded Specimen due to severe heat input. The Vickers hardness test results show that among the two welding methods employed, FSW has yielded the best mechanical properties and found that evaporation of magnesium is more in Pulsed TIG welding compared with FSW process.

- by IJAERS Journal
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- Aluminum Alloys, Chemical Analysis
- by FERGYANTO GUNAWAN
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- Corrosion, Casting, Aluminum Alloys, Materials Characterization

Elemental powders of Al, Cu, Mg and x wt.% CNT (x: 0-2.5) were blended and milled in the high-energy ball mill for 4 h. Milled powders of Al alloy-CNT composites were subsequently consolidated by upset forging followed by hot extrusion. Even though the particle size of milled powders of Al alloy-CNT composites decreased with the addition of CNT, there is no significant effect on crystallite size. Raman spectra indicated that the nanocrystalline structure of CNT is retained after milling. Yield and ultimate tensile strengths increased with CNT content and Al alloy-2.5 wt.% CNT exhibited an enhancement of 56 and 73%, respectively, when compared to Al alloy in solutionized condition. The improvement in mechanical properties of Al alloy-CNT composites is due to ultra-fine grain size, finer second-phase precipitates and uniform dispersion of CNT.

Tribological behaviour of a hybrid composite with the aluminium alloy base A356 reinforced by 10 wt. % SiC and 5 wt. % of graphite is treated in this paper. The optimization of tribological behaviour was conducted through the application of Taguchi method. Hybrid composites were obtained in the compocasting procedure. Tribological examinations were executed on the block on disc tribometer with the variation of two different load values (20 and 30 N), three sliding speed values (0.25, 0.5 and 1 m/s) and three sliding distance values (30, 90 and 150 m). All the examinations were carried out in conditions with no lubrication existing. The analysis of the wear rate was conducted using the ANOVA method of analysis. The greatest impact on the wear rate has the load (62.11 %), then the sliding speed (32.88 %), and the least the sliding distance (2.57 %). The interaction of the factors does not have a significant impact on the wear rate.

- by Blaza Stojanovic and +2
- •
- Engineering, Materials Engineering, Mechanical Engineering, Materials Science

Alloy beams and beam like elements are principal constituents of many structures and widely used in high speed machinery, aircraft and light weight structures. Crack is a damage that often occurs on members of structures and may cause serious failures of structures. In this research the natural frequency of a cracked cantilever beam is investigated by finite element method by using of ANSYS program with different crack depth and location effect. The beam material studied is aluminum alloy, titanium alloy, copper alloy and magnesium alloy. A comparison is made between these alloys and conclude optimized result between them. The increase of the beam length result in a decrease in the natural frequencies of the composite beam and also shows that an increase of the depth of cracks lead to a decrease in the value of natural frequencies.

- by IJREI Journal and +1
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- Aluminum Alloys, Copper Alloys

This paper presents tribological characteristics of hybrid composites with aluminium
matrix, reinforced with silicon carbide (SiC) and graphite (Gr). Newly
formed Al/SiC/Gr hybrid composites are the combination of the two different hybrid
materials. Namely, hard particles of silicon carbide increase the hardness and
resistance to wear, while soft particles of graphite improve lubrication and reduce
friction coefficient and wear. It is possible to obtain Al/SiC/Gr hybrid composites
by different methods of casting. Tribological tests show that load, sliding speed,
sliding distance, content and size of reinforcement particles influence the size
and the type of wear and friction coefficient of Al/SiC/Gr hybrid composites with
aluminium matrix.

- by Blaza Stojanovic and +1
- •
- Materials Engineering, Materials Science, Composite Materials and Structures, Ceramics (Ceramics)

An Al-10Ni-8Y (at.%) alloy was atomized by Ar gas atomization in a close-coupled nozzle atomizer. The microstructure, phase composition, and thermal stability of the as-atomized powder were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis and differential scanning calorimetry. Activation energies for different crystallization reactions were calculated using both Kissinger and Ozawa methods. The supercooled liquid region DeltaT(x) (= T-x - T-g, where T-x and T-g are crystallization onset temperature and glass transition temperature, respectively) was detected to be in the range of 14-24 K. Also presented were attempts to determine the critical particle size for amorphous structure.

- by Sheng Guo
- •
- Amorphous Alloys, Gas Atomized Powder, Aluminum Alloys