Aluminum Alloy Metal Matrix Research Articles

ARTIFICIAL NEURAL NETWORK (ANN) APPROACH TO PREDICTION OF DIFFUSION BONDING BEHAVIOR (SHEAR STRENGTH) OF SiCP REINFORCED ALUMINUM METAL MATRIX COMPOSITES

In this study, Artificial Neural Network approach to prediction of diffusion bonding behavior of SiCP reinforced aluminum alloy metal matrix composites, manufactured by powder metallurgy process, were obtained using a back-propagation neural network that uses gradient descent learning algorithm. A powder Al-Mg-Si matrix was employed with particulate SiC at 5-10-20 (wt) % fractions. MMC’s were fabricated by powder mixing and hot pressing at 600oC below liquation temperature. Diffusion bonding was carried out under protective atmosphere (argon) at 550, 575, 600 and 625oC process temperatures for 20, 40 and 60 minutes with a load of 0.25 MPa, below those which would cause macrodeformation. Microstructure examination at bond interface were investigated by optical microscopy, SEM. Specimens were tested for shear strength and metallographic evaluations. After the completion of experimental process and relevant test, to prepare the training and test (checking) set of the network, results were recorded in a file on a computer. In neural networks training module, different SiC reinforcement fractions (wt), different temperatures and welding periods were used as input, shear strength of bonded specimens at interface were used as outputs. Then, the neural network was trained using the prepared training set (also known as learning set). At the end of the training process, the test data were used to check the system accuracy. As a result the neural network was found successful in the prediction of diffusion bonding shear strength and behavior. * Department of Metal, Faculty of Technical Education, University of Firat, 23119 Elazig, Turkey, mtaskin@firat.edu.tr ** Department of Metal, Faculty of Technical Education, University of Firat, 23119 Elazig, Turkey, ucaligulu@firat.edu.tr *** Department of Metal, Faculty of Technical Education, University of Firat, 23119 Elazig, Turkey, hdikbas@firat.edu.tr ARTIFICIAL NEURAL NETWORK (ANN) APPROACH TO PREDICTION OF DIFFUSION BONDING BEHAVIOR (SHEAR STRENGTH) OF SiCP REINFORCED ALUMINUM METAL MATRIX COMPOSITES Taskin, Caligullu ve Dikbas, 2008 1812

Neural network based prediction of mechanical properties of particulate reinforced metal matrix composites using various training algorithms

Recently, artificial neural networks are used as an interdisciplinary tool in many applications. There are various training algorithms used in neural network applications. In this study, it is aimed to investigate the effect of various training algorithms on learning performance of the neural networks on the prediction of bending strength and hardness behaviour of particulate reinforced Al–Si–Mg metal matrix composites (MMCs). Al 2O 3/SiC particulates reinforced MMC was produced by using stir casting process. Al 2O 3/SiC powder mix obtained from Al 2O 3/SiC ceramic cake, which was produced firing of aluminium sulphate aqueous solution and SiC mix before stir casting. In the experimental processes, during fabrication, stirring was applied to create a vortex for addition reinforcing particles and the production of aluminium alloy metal-matrix composites. 10 vol.% of dual ceramic powder with different SiC particle size range mix was inserted in liquid aluminium by using stir casting under Ar pressure to obtain dual particulates reinforced MMCs. This mixing was achieved successfully; microstructure, bending strength and hardness properties of the composites were tested. Bending strength and hardness behaviour were predicted with four different training algorithms using a back-propagation neural network. The training and test sets of the neural network were initially prepared using experimental results that were obtained and recorded in a file on a computer. Test results revealed that bending strength and hardness resistance of the composites increased with decrease in ductility, with decrease size of the reinforcing SiC particulates in the aluminium alloy metal matrix. In the training and test modules of the neural network, different SiC particles size (μm) range was used as input and bending strength and hardness behaviour were used as output in the produced MMCs. After the preparation of the training set, the neural network was trained using four different training algorithms. For each algorithm, the results were analyzed. The test set was used to check the system accuracy for each training algorithm at the end of learning. In conclusion, Levenberg–Marquardt (LM) learning algorithm gave the best prediction for bending and harness behaviours of aluminium metal matrix composites.

An Elastoplastic Stress Analysis of Aluminum Alloy Metal-Matrix Composite Beams under a Transverse Linearly Distributed Load by Use of Anisotropic Elasticity Theory

Beams are structural elements loaded transversely in general conditions. This loading causes shear forces and bending moment. In this study, an analytical elastoplastic stress analysis is carried out on simply supported stainless steel fiber-reinforced aluminum alloy metal-matrix composite beams under linearly distributed load by use of anisotropic elasticity theory. In the elastoplastic solution, the material is assumed to be perfectly plastic. Sample problems are given for various angles analytically. The yielding begins at the upper and lower surfaces of the beam at the same distances from the ends. The intensity of residual stress component of σ x is a maximum at the upper and lower surfaces whereas the residual stress component of τ xy is maximum on the x axis of the beam. The composite beams can be strengthened by using the residual stresses.

Abrasive wear of Al2O3 particle reinforced 2024 aluminium alloy composites fabricated by vortex method

Abstract The wear behaviour of varying size and weight fraction of particles up to 30 wt% Al 2 O 3 particles reinforced 2024 Aluminium alloy Metal Matrix Composites (MMCs) fabricated by a vortex method was investigated in a pin on disc abrasion test apparatus against different SiC abrasives at room conditions. Wear tests performed under the load of 2 N against SiC abrasive papers of 20 (600 grit), 46 (320 grit) and 60 μm (240 grit). The effects of sliding distance, Al 2 O 3 particle content and size, and abrasive grit sizes on the abrasive wear properties of the composites have been evaluated. The main wear mechanisms were identified using a scanning electron microscope. The results showed that Al 2 O 3 particles reinforcement improved the abrasion resistance against all the abrasives used, and the abrasive wear resistance decreased with an increase in the sliding distance and the abrasive grit size. The wear resistance of the composites was considerably bigger than that of the aluminium alloy and increased with increasing Al 2 O 3 particles content and size.

Production and mechanical properties of Al 2O 3 particle-reinforced 2024 aluminium alloy composites

2024 aluminium alloy metal matrix composites (MMCs) reinforced with three different sizes and weight fractions of Al 2O 3 particles up to 30 wt.% were fabricated by a vortex method and subsequent applied pressure. The effects of Al 2O 3 particle content and size of particle on the mechanical properties of the composites such as hardness and tensile strength were investigated. The density measurements showed that the samples contained little porosity, and the amount of porosity in the composites increased with increasing weight fraction and decreasing size of particles. Scanning electron microscopic observations of the microstructures revealed that the dispersion of the coarser sizes of particles was more uniform while finer particles led to agglomeration of the particles and porosity. The results show that the hardness and the tensile strength of the composites increased with decreasing size and increasing weight fraction of particles.

The tensile response and fracture behavior of 2009 aluminum alloy metal matrix composite

Abstract In this research paper the tensile properties and fracture characteristics of aluminum alloy 2009 discontinuously reinforced with silicon carbide particulates (SiC p ) are presented and discussed. The increased strength of the Al 2009/SiC p composite is attributed to the synergistic influences of residual stresses generated due to intrinsic differences in thermal expansion coefficients between the composite constituents, strengthening from constrained plastic flow and triaxiality in the ductile aluminum alloy metal matrix due to the presence of ceramic particle reinforcements. Fracture on a microscopic scale comprised of cracking of the individual and clusters of SiC particles present in the microstructure. Final fracture of the composite resulted from crack propagation through the matrix between the clusters of reinforcing SiC particles. The key mechanisms governing the tensile fracture process are elucidated.

Effect of Particulate Silicon Carbide on Cyclic Plastic Strain Response and Fracture Behavior of 6061 Aluminum Alloy Metal Matrix Composites

In this paper, the cyclic stress response and cyclic stress–strain response characteristics, cyclic strain resistance and low-cycle fatigue life, and mechanisms governing the deformation and fracture behavior of aluminum alloy 6061 discontinuously reinforced with silicon carbide (SiC) particulates are presented and discussed. Two different volume fractions of the carbide particulate reinforcement phase in the aluminum alloy metal matrix are considered. The composite specimens were cyclically deformed using fully reversed tension–compression loading under total strain-amplitude-control. The stress response characteristic was observed to vary with strain amplitude. The plastic strain-fatigue life response was found to degrade with an increase in carbide particulate content in the metal matrix. The fracture behavior of the composite is discussed in light of the interactive influences of composite microstructural effects, cyclic strain amplitude and concomitant response stress, deformation characteristics of the composite constituents and cyclic ductility.

Settling of silicon carbide particles in cast metal matrix composites

The success of metal matrix composites as potential materials for the manufacture of engineering components depends on closer control of their microstructure during processing. One of the important factors influencing the microstructure is settling of the particles during liquid processing of these composites. In this paper settling of SiC particles in cast aluminium alloy metal matrix composite was studied as function of particle size, weight fraction and melt temperature during isothermal holding and solidification experiments. Isothermal holding of A356 aluminium alloy reinforced with 20 wt.% of silicon carbide particles showed that settling occurs at significantly slower rates than predicted by theoretical models. The results also showed that the melt temperature appears to have a slight effect on the settling behaviour. Experiments on settling during mixing and solidification revealed that at low melt temperatures the volume fraction of particles does not affect the rate of settling but as the melt temperature increases the particles tend to settle when present in lower volume fractions.

Application of a novel multilayer spray forming technology in the preparation of large dimension aluminium alloy blanks

Principle of multilayer spray forming and preparation technique of tubes and billets by it were presented and described in the article. The marked characteristic of multilayer spray forming technology is the to-and-fro movement of spray system, so the preform is deposited layer by layer with the surface of the deposit retaining relatively low temperature during the spray forming process. The two outstanding advantages of multilayer spray forming are as follows: suitable for manufacturing large dimension blanks, higher solidification cooling rate. Now Al-Fe-V-Si alloy (8009) and SiC particle reinforced aluminium alloy metal matrix composite billets of 300–600 mm in diameter and tubular blanks of size up to 650 mm in outer diameter, 360 mm in inner diameter and 1 200 mm in length have been made with the technology. After extrusion, the material has good properties.

Microstructure and Grain Growth Behavior of an Aluminum Alloy Metal Matrix Composite Processed by Disintegrated Melt Deposition

In this study, a silicon-carbide particulate (SiCp), reinforced aluminum alloy-based, metal-matrix composite was synthesized using disintegrated melt deposition. Microstructural characterization of the disintegrated melt deposition processed composite samples revealed the presence of columnar-equiaxed shaped grain structure, noninterconnected porosity associated with the reinforcing carbide particulates, improved interfacial integrity between the reinforcement and the aluminum alloy matrix coupled, and a near uniform distribution of the reinforcing SiC particulates in the alloy matrix. An examination of grain growth with the objective of delineating the effects of the silicon carbide particulates revealed a diminishing to minimal role of the reinforcing phase with an increase in temperature from 450 to 590 °C.

The quasi-static response and fracture behavior of a thermomechanically processed aluminum alloy metal–matrix composite

In this paper, the influence of thermomechanical processing on the tensile response and fracture behavior of a disintegrated melt deposited aluminum alloy metal–matrix composite is presented and discussed. The uniaxial tensile properties of the as-processed composite is compared with an extruded counterpart. The tensile properties and fracture behavior of the of the as-processed and extruded composites are rationalized in light of the mutually interactive influences of stress state and intrinsic composite microstructural effects.

Miniature thermal cycling tests on aluminium alloy metal matrix composites

A new miniaturised electrothermomechanical test system has been used to study the thermal cycling response of a number of aluminium alloy metal matrix composites reinforced with either Al203 or SiC particles. Tests were also performed on a monolithic 2618 aluminium alloy for comparison. The system showed good test discrimination between the different materials for both constant load-constant temperature (creep) tests and constant load-temperature cycling (50–200°C) tests. The system was also used to compare the yield behaviour at 200°C, and the thermal expansion and thermal diffusivity of several of the materials.

Influence of matrix alloying elements on reactive synthesis of 2124 aluminium alloy metal matrix composites

In situ TiB2 particle reinforced Al alloys are produced by reactive synthesis from elemental and prealloyed powders. The influence of 2124 alloying elements on the reactive synthesis is evaluated with a comparison of elemental AI, elemental AI-Cu mixture, and 2124 Al prealloyed powders as matrix materials. Experimental investigations by differential scanning calorimetry and dilatometry showed that the presence of Cu leads to an increase in the reaction rate during the formation of intermediate reaction products in comparison with the elemental Al matrix. X-ray diffraction of the reaction products showed a more complete conversion of the intermediate Al3 Ti as a result of Cu addition. The Cu has no influence on the TiB2 particle size, but the TiB2 morphology changed from pure hexagonal to a more rounded morphology.

Influence of matrix alloying elements on reactive synthesis of 2124 aluminium alloy metal matrix composites

Influence of matrix alloying elements on reactive synthesis of 2124 aluminium alloy metal matrix composites

Cyclic plastic strain response and fracture behavior of 2080 aluminum alloy metal matrix composite

A study has been made to understand the role of composite microstructure on failure through mechanisms governing the quasi-static and cyclic fracture behavior of aluminum alloy X2080 discontinuously-reinforced with silicon carbide (SiC) particulates. Two different volume fractions of the carbide particulate reinforcement phase, in the aluminum alloy matrix, are considered. Quasi-static fracture of the composite comprised cracking of the individual and clusters of particulates present in the microstructure. Particulate cracking increased with reinforcement content in the aluminum alloy matrix. Final fracture occurred as a direct result of crack propagation through the matrix between particulate clusters. The composite specimens were cyclically deformed under fully-reversed, total strain-amplitude-controlled cyclic straining, giving lives of less than 10 4 cycles to failure. The plastic strain-fatigue life response was found to degrade with an increase in carbide particulate content in the metal matrix. The cyclic fracture behavior of the composite is discussed in light of concurrent and mutually interactive influences of composite microstructural effects, matrix deformation characteristics, cyclic plastic strain amplitude and resultant response stress.

Interface reactions in squeeze cast Saffil fibre/piston alloy composites

High resolution scanning transmission electron microscopy techniques were used to analyse the reaction layer formed between the fibre and metal in aluminium alloy metal matrix composites. It was found that the reaction layer formed between the fibre and metal was uniform and that the layer was not affected by the phases present in the adjacent metal. It was also found that the reaction layer was the same irrespective of whether it formed next to a region of binder (SiO2 or Al.SiO2) or of fibre (δ-Al2O3 or Al.SiO2). The layer formed with this system is assumed to be MgAl2O4. Further experiments were carried out using high spatial resolution Auger spectroscopy. Analysis of samples fractured under ultra high vacuum conditions revealed that the metal/fibre interface fractured at the MgAl2O4 layer. The evidence presented strongly suggests that the interface layer wasformed by a reaction between the metal and the atmosphere, rather than by a reaction between the metal and the fibre. It was also shown that the MgAl2O4 layer is the weakest point in the interface region.

Formation of MgAI2O4 at interface between a squeeze cast piston alloy and Saffil fibre reinforcement

An investigation was carried out into the formation of the spinel MgAl204 phase on the surface of fibres in aluminium alloy metal matrix composites. Three castings were made by squeeze casting ceramic fibre preforms. The following preforms were used with piston alloy AE109: a Saffil fibre preform with a Si02 binder, a Saffil fibre preform deoxygenated before casting with a Si02 binder, and an aluminosilicate fibre preform with a CaF2 binder. Interface analysis was performed by a high resolution scanning transmission electron microscope using a windowless, energy dispersive spectrometry detector and parallel electron energy loss spectrometry. It was found that the MgAI204 phase was formed initially during the casting process by a reaction between the alloy and the oxygen within the air spaces of the preform. The Si02 binder was not reduced during casting or during cooling even though diffusion of magnesium and aluminium atoms has been reported in the literature. The contact angle between the metal and the fibres was dependent on the thickness of the oxide layer formed on the molten metal and not on the interfacial energies of the metal and fibres. The oxide thickness was ∼30 nm, which is consistent with a contact angle of ∼150° in air.

Biaxial cyclic analysis of Al 2O 3p-6061 Al composite

Proportional and non-proportional biaxial cyclic tests were carried out on cylindrical specimens of 20% Al 2O 3p 6061 aluminum alloy metal matrix composite in the T0 (annealed) and T6 (quenched and artifically aged) conditions. These results were then compared to those found using a three-dimensional (3D) finite element analysis on a representative unit cell. A special material model, capable of accurately describing the behaviour of metals under multiaxial and non-proportional loads was used to simulate the elastic-plastic aluminum matrix. Comparison of unit cell results using sphere and cube shaped reinforcements shows that the unit cell using a spherical inclusion produces less hardening and lower yield stresses but agrees well with experimental values. Under cyclic equibiaxial loading the modulus of the annealed specimen was found to drop rapidly with increasing numbers of cycles. While the model was able to predict the initial hysteresis loops it could not represent the decrease in stiffness without the addition of further damage parameters. This change in the modulus is attributed to decohesion at the matrix-reinforcement interface. The model is much more accurate than the conventional kinematic and isotropic hardening models and predicts the overall composite behaviour fairly accurately.

Transient thermal analysis of solidification in a centrifugal casting for composite materials containing particle segregation

One-dimensional heat-transfer analysis during centrifugal casting of aluminum alloy and copper base metal matrix composites containing Al2O3, SiCp, and graphite particles has been studied. The model of the particle segregation is calculated by varying the volume fraction during centrifugal casting, and a finite difference technique has been adopted. The results indicate that the thickness of the region in which dispersed particles are segregated due to the centrifugal force is strongly influenced by the speed of rotation of the mold, the solidification time, and the density difference between the base alloy and the reinforcement. In the case where the base alloy density is larger than that of the particles, the thickness of the particle-rich region near the inner periphery decreases with an increase in speed, thereby increasing the volume fraction of dispersion. The solidification time of the casting is also dependent upon the speed of rotation of the mold, and it decreases with an increase in speed. This study also indicates that the presence of particles increases the solidification time of the casting.

Hot Working Characteristics of Discontinuously Reinforced Aluminium Alloy Metal Matrix Composites

Hot Working Characteristics of Discontinuously Reinforced Aluminium Alloy Metal Matrix Composites