Behavior Of Metal Matrix Composites Research Articles

Influence of thermal residual stress on behaviour of metal matrix composites reinforced with particles

The properties of a metallic matrix composites materials (MMC's) reinforced with particles can be affected by different events occurring within the material in a manufacturing process. The existence of residual stresses resulting from the manufacturing process of these materials (MMC's) can markedly differentiate the curves obtained in tensile tests obtained from compression tests. One of the themes developed in this work is the influence of residual stresses on the mechanical behaviour of these materials. The objective of this research work presented is numerically estimate the thermal residual stresses using a unit cell model for the Mg ZC71 alloy reinforced with SiC particles with volume fraction of 12% (hot-forging technology). The MMC's microstructure is represented as a three dimensional prismatic cube-shaped with a cylindrical reinforcing particle located in the centre of the prism. These cell models are widely used in predicting stress/strain behaviour of MMC's materials, in this analysis the uniaxial stress/strain response of the composite can be obtained through the calculation using the commercial finite-element code.

An investigation of mechanical properties and corrosion resistance of Al2618 alloy reinforced with Si3N4, AlN and ZrB2 composites

Aluminum 2618 matrix composites (AMCs) reinforced by AlN, Si3N4 & ZrB2 particles were fabricated from Al2618- x wt% AlN, Si3N4, ZrB2 (x = 0, 2, 4, 6, 8) by stir casting. In ZrB2 particles were fabricated by in-situ reaction from mixtures of K2ZrF6 & KBF4. The mechanical properties of the composites were increased with respect to the percentage of weight. The corrosion behavior of metal matrix composites (MMCs) is strictly linked with the presence of heterogeneities such as reinforcement phase, micro crevices, porosity, secondary phase precipitates, and interaction products. The present work is investigated relating to the corrosion resistance of Aluminum (2618) metal matrix composites (AMCs) reinforced with AlN, Si3N4 & ZrB2 was investigated by electro chemical studies such as polarization study and AC impedance spectra. The above materials are immersed in an aquaise 3.5% Sodium Chloride (Nacl) solution corrosion parameters such as corrosion potential (Ecorr), corrosion current (Icorr), Linear Polarization Resistance (LPR), charge transfer resistance (Rt), Double layer capacitance (Cdl) will be evaluated from this and the most corrosion resistance material is determined. Finally the results are obtained by the polarization studies and AC impedance spectra which leads to the conclusion that the corrosion resistance of 0% of Al2618 alloy has a low corrosion resistance and the composites have a high corrosion resistance. The corrosion resistance is gradually increased with respect to the Wt% of composites (2%, 4%, 6%, 8%).

A Study of Interface Damage on Mechanical Properties of Particle-Reinforced Composites

In this article, we discuss the influence of interface damage on the uniaxial tensile elastic–plastic behavior of metal matrix composites (MMCs) that are reinforced by spherical or cubic particles having identical distribution and volume fraction. The mechanical property of the composites was simulated by a three-dimensional periodic finite-element model where we adopted the bilinear cohesive zone model to describe the failure behavior of particle/matrix interface and considered the influence of strain gradient in the matrix. Interface morphology has a strong influence on the mechanical properties. Under perfect interface bonding, MMC reinforced by cubic particles exhibits higher tensile strength than that reinforced by spherical particles. When interface damage exists, the strength of the composites decreases and MMC reinforced by two types of particles exhibit identical performance except a higher uniform strain in the spherical-reinforced one. An examination of interface decohesion indicates that damage occurs when the applied strain is as small as 1%. Compared with the perfectly bonded interface, debonded interface in MMC with cubic particles suffers more severe damage, which causes further decrease in average stress along tensile direction.

On the Creep Fatigue Behavior of Metal Matrix Composites

The mechanical behaviour of Metal Matrix Composites (MMCs) subjected to a high temperature and cyclic load condition is difficult to understand. The significantly differing coefficients of thermal expansion between ceramic and metal give rise to micro thermal stresses. Their performance under varying load and high temperature is complex and inconsistent, where fatigue and creep damages become the main failures of MMCs. To improve current understanding of the relationship between creep fatigue interaction of MMCs, the history of thermal and mechanical loading, and the creep dwell period, a highly accurate but robust direct simulation technique on the basis of the Linear Matching Method (LMM) framework has been proposed in this paper, and been applied to model the fatigue and creep behaviour of MMCs. A homogenised FE model is considered in all analyses, which consist of continuous silicon carbide fibres embedded in a square 2024T3 aluminium alloy matrix array. Various factors that affect creep and fatigue behaviours of composites are analysed and discussed, including effects of the applied load level, dwell period and temperature on the MMC's performance. The effects of reversed plasticity on stress relaxation and creep deformation of MMC are investigated, and the behaviours of cyclically enhanced creep and elastic follow-up are presented. The applicability and accuracy of the proposed direct method has also been verified by the detailed step-by-step analysis via Abaqus.

Poster #S175 THE ERYTHROCYTE MEMBRANE LIPID ABNORMALITIES OBSERVED IN SCHIZOPHRENIA PATIENTS SUPPORT THE OXIDATIVE STRESS HYPOTHESIS IN SCHIZOPHRENIA

Interface between ceramic particulate and matrix is known to control the response of the materials and functionality of the composite. Among numerous physical properties, grain structure of the materials has also played a significant role in defining the behaviour of metal matrix composites. Usually, silicon carbide (SiC) particles show poor interfacial wettability in aluminium melt. Herein, we were successfully synthesized magnesium oxide (MgO) and nanocrystalline magnesium aluminate (MgAl2O4) spinel coated silicon carbide (SiC) core-shell micro-composites through sol-gel technique to improve the wettability of dispersoids. Core-shell structures of submicron size were thoroughly investigated by various characterization techniques. Further, aluminium matrix composites incorporated with pristine SiC, MgO grafted SiC and MgAl2O4 grafted SiC particles were fabricated by stir casting technique, respectively. Additionally, as-cast composites were processed via friction stir processing (FSP) technique to observe the influence of grain refinement on mechanical and damping properties. Electron back scattered diffraction (EBSD), Field emission scanning electron microscopy (FE-SEM) and X-ray energy dispersion spectroscopy (EDX) analysis were conducted for investigating grain size refinement, adequate dispersion, stability and de-agglomeration of encapsulated SiC particles in aluminium matrix. The mechanical as well as thermal cyclic (from − 100 to 400 °C) damping performance of the as-cast and friction stir processed composites were studied, respectively. Finally, the enhanced properties were attributable to reduced agglomeration, stabilization and proper dispersion of the tailored SiC particles Al matrix.

Effect of heat treatment on the white layer and its effect on the damping behavior of metal matrix composites

In the present study, the effect of heat treatment on the white layer and its effect on the damping behavior of the rice husk ash (RHA) reinforced metal matrix composites have been studied. The damping measurements were performed using dynamic mechanical analyzer. The specimens for damping measurements were machined using wire cut electric discharge machining (EDM) process. The results show that the white layer has a great influence on the damping capacity of the composites.

Practical Applicability and Limitation of Representative Volume Element Approach to Model Creep Behaviors of Metal Matrix Composites

The applicability and effectiveness of the representative volume element (RVE) approach for predictions of creep properties in metal matrix composite materials were analyzed numerically in this paper. A special attention was paid to the sensitivity of numerical solutions with respect to the volume element size, in terms of short-term creep strength and secondary creep rate of the model. The numerical models were based on the microstructure of composite material which consisted of creeping matrix with randomly distributed non-creeping hard spherical particles. A modified random sequential adsorption algorithm was applied to reproduce volume elements of composite microstructures. Then, the elements were subjected to creep deformations with uniaxial stress boundary condition. Statistical analysis of numerical experiments for different volume element sizes showed that the effective creep properties can be determined for large volumes of the elements. In both cases of creep strength and secondary creep rate, the statistical fluctuations of the numerical solutions were decreased with increasing volume of element. Several test cases are also presented in order to validate the model against experimental results from literature, and the advantage and limitation of the RVE approach are discussed. [doi:10.2320/matertrans.M2014137]

Corrosion and tribocorrosion behaviour of Al–Si–Cu–Mg alloy and its composites reinforced with B4C particles in 0.05 M NaCl solution

The corrosion behaviour of metal matrix composites (MMCs) is strictly linked with the presence of heterogeneities such as reinforcement phase, microcrevices, porosity, secondary phase precipitates, and interaction products. Most of the literature related to corrosion behaviour of aluminium matrix composites (AMCs) is focused on SiC reinforced AMCs. On the other hand, there is very limited information available in the literature related to the tribocorrosion behaviour of AMCs. Therefore, the present work aims to investigate corrosion and tribocorrosion behaviour of Al–Si–Cu–Mg alloy matrix composites reinforced with B4C particulates. Corrosion behaviour of 15 and 19% (vol) B4C reinforced Al–Si–Cu–Mg matrix composites and the base alloy was investigated in 0.05M NaCl solution by performing immersion tests and potentiodynamic polarisation tests. Tribocorrosion behaviour of Al–Si–Cu–Mg alloy and its composites were also investigated in 0.05M NaCl solution. The tests were carried out against alumina ball using a reciprocating ball-on-plate tribometer. Electrochemical measurements were performed before, during, and after the sliding tests together with the recording of the tangential force. Results suggest that particle addition did not affect significantly the tendency of corrosion of Al–Si–Cu–Mg alloy without mechanical interactions. During the tribocorrosion tests, the counter material was found to slide mainly on the B4C particles, which protected the matrix alloy from severe wear damage. Furthermore, the wear debris were accumulated on the worn surfaces and entrapped between the reinforcing particles. Therefore, the tendency of corrosion and the corrosion rate decreased in Al–Si–Cu–Mg matrix B4C reinforced composites during the sliding in 0.05M NaCl solution.

EVALUATION OF MECHANICAL PROPERTIES OF ALUMINIUM ALLOY 2024 REINFORCED WITH SILICON CARBIDE AND FLY ASH HYBRID METAL MATRIX COMPOSITES

Materials are frequently chosen for structural applications because they have desirable combinations of mechanical characteristics. Development of hybrid metal matrix composites has become an important area of research interest in Materials Science. In view of this, the present study focuses on the formation of aluminium-Sic-fly ash hybrid metal matrix composites. The present study was aimed at evaluating the physical properties of Aluminium 2024 in the presence of silicon carbide, fly ash and its combinations. Consequently aluminium metal matrix composite combines the strength of the reinforcement with the toughness of the matrix to achieve a combination of desirable properties not available in any single conventional material. The compositions were added up to the ultimate level and stir casting method was used for the fabrication of aluminium metal matrix composites. Structural characterization was carried out on metal matrix composites by x-ray diffraction studies and optical microscopy was used for the micro structural studies. The mechanical behaviors of metal matrix composites like density, tensile strength, yield strength, elongation and hardness tests were ascertained by performing carefully designed laboratory experiments that replicate as nearly as possible the service conditions. In the presence of silicon carbide and fly ash [SiC (5%) + fly ash (10%) and fly ash (10%) + SiC (10%)] with aluminium, it was fairly observed that the density of the composites was decreased and the hardness was increased. Correspondingly, the increase in tensile strength was also observed but elongation of the hybrid metal matrix composites in comparison with unreinforced aluminium was decreased. The aluminium-SiC-fly ash hybrid metal matrix composites significantly differed in all of the properties measured. Aluminium in the presence of SiC (10%)-fly ash (10%) was the hardest instead of aluminium-SiC and cluminium-fly ash composites. The study can be further extended by evaluating the wear and corrosion of the resultant material.

Multiresolution Modeling of the Dynamic Loading of Metal Matrix Composites

The mechanical behavior of metal matrix composites (MMCs) varies significantly under rapid straining as compared to quasi-static loading and is often dominated by underlying microstructural features (grain structure, porosity, inclusions, and defects). Analysis of the behavior of MMCs under dynamic loading requires theoretical and experimental approaches that integrate the strain rate and microstructural effects. In this article, we introduce a multiresolution modeling capability for studying nonlinear planar wave propagation in heterogeneous materials with an application to MMCs. This framework is based on direct numerical simulation (DNS) and compared to an upscaled microcontinuum model. The DNS explicitly accounts for microstructural features characterizing the materials and is based on a combination of a crystal plasticity formulation for the behavior of the host matrix and the Johnson–Holmquist model for the particulate reinforcements. The nonuniformity of the wave propagating through MMCs is spatially resolved. The results from the mesoscale DNS are used to inform a microcontinuum model that introduces richer kinematics to account for microstructural features without explicitly modeling them and with far fewer total degrees of freedom. A quantitative comparison of the reduced degrees of freedom model against DNS is performed and enables us to draw conclusions on the predictive capability of the microcontinuum model to study the dynamic response of heterogeneous materials.

High temperature single impact studies on material deformation and fracture behaviour of metal matrix composites and steels

To exploit the full potential of materials used at elevated temperatures, it is crucial to understand their deformation and fracture mechanisms. High Temperature Single Impact Studies were performed to evaluate deformation mechanisms at different energy and momentum levels and their correlation to temperature. The limitations of materials regarding their impact resistance, the resulting deformation and fracture mechanisms were investigated. NiCrBSi based Metal Matrix Composites (MMC), reinforced with TiCNiMo or Cr3C2Ni particles, manufactured by Plasma Transferred Arc Cladding along with two different types of steels were tested and compared to study different types of deformation and fractures. Results indicate more ductile deformation behaviour of the investigated steels, while the MMCs show brittle behaviour at several temperatures. Critical impact loadings were determined at elevated temperatures to limit the range of use in impact dominated high temperature environment. Results show that the influence of different momenta at constant impact energy levels cannot be neglected.

Investigation of Wear Properties of Al-4.5wt.%Cu Nano-Composite Reinforced with Different Weight Percent of TiC Nano Particles Produced by Mechanical Alloying

Resistance to wear is an important factor in design and selection of structural components in relative motion against a mating surface. The present work deals with studies on the wear behavior of metal matrix composites manufactured using powder metallurgy technique of ball milled mixing in a high energy attritor and using a blend-press-sinter methodology. Matrix of pre–mechanical alloyed Al-4.5 %wt Cu was used to which different weight percents of nano-sized TiC reinforcement were added. Microstructural characterization of the materials revealed reasonably uniform distribution of TiC reinforcement and presence of minimal porosity. Wear tests were performed using a pin on disk apparatus. The MMCs were rubbed against a carbon steel pin under loads of 10 and 20 N at a sliding velocity of 0.1 ms−1; the environmental humidity lower than 30% and a track length of 1500 m. The degree of improvement in dry sliding wear resistance and hardness brought about by reinforcement is strongly dependent on the weight percent of reinforcement and the wear behavior was determined through the precise measurement of weight loss of the samples. Worn surfaces were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).

Modeling stiffness of nanolayered silicate‐modified polyamide 6 via FEM micromechanical modeling and analytical composite models

AbstractIn this work, numerical and analytical models are chosen to study reinforcement effect of nanolayered silicate modified polyamide 6 (PA 6) composites at ambient temperature. A numerical self‐consistent unit cell model in conjunction with finite element method is applied to predict the stiffness of this polymer nanocomposite, which has been successfully applied for simulating mechanical behavior of metal matrix composites. In this work, a rectangular inclusion (layered silicate) is surrounded by PA 6 polymer matrix, which is again embedded in the PA 6/layered silicate nanocomposite. The stiffness of the composite is determined iteratively in a self‐consistent manner. For comparison, two analytical composite models (Halpin–Tsai model and Tangdon–Weng model) are implemented to evaluate the stiffness of this nanocomposite via calculations performed within MATLAB. In the modeling volume fraction, aspect ratio, exfoliation and orientation of the nanolayered silicate are taken into account. It is demonstrated that the numerical approach using the self‐consistent embedded cell model coincides well with experimental results of the stiffness of the composite. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Micromechanical analysis of thermoelastoplastic behavior of metal matrix composites

A micromechanics model based on the variational asymptotic method for periodic composites was developed using an incremental formulation to capture the coupled thermo-elasto-plastic behavior of metal matrix composites. Taking advantage of the small size of the microstructure, a variational statement of the unit cell through an asymptotic expansion of an functional of energy change was formulated to calculate the effective instantaneous tangential elasto-plastic matrix and thermal stress matrix of the composite materials. An iterative homogenization and localization technique was proposed to simulate the nonlinear thermo-elasto-plastic behavior of metal matrix composites. This model was implemented using the finite element method. For validation, a numerical example was examined to demonstrate the application and accuracy of this theory and companion code.

Modeling Interparticle Size Effect on Deformation Behavior of Metal Matrix Composites by a Gradient Enhanced Plasticity Model

Experimental tests show that particle (inclusion or precipitate) size and interparticle spacing, besides volume fraction, have a considerable effect on the macroscopic mechanical response of metal matrix microreinforced composites. Classical (local) plasticity models unlike nonlocal gradient enhanced plasticity models cannot capture this size dependency due to the absence of a material length scale. In this paper, one form of higher-order gradient plasticity enhanced model, which is derived based on principle of virtual power and laws of thermodynamic, is employed to investigate the size effect of elliptical inclusions with different aspect ratios based on unit cell simulations. It is shown that by decreasing the particle size or equivalently the interparticle spacing (i.e., the spacing between the centers of inclusions), while keeping the volume fraction constant, the average stress–strain response is stronger and more sensitive to the inclusion’s aspect ratio. However, unexpectedly, decreasing the free-path interparticle spacing (i.e., the spacing between the edges of inclusions perpendicular to the principal loading direction) does not necessarily lead to largest strengthening. This is completely dependent on the plastic strain gradient hardening due to distribution and evolution of geometrically necessary dislocations that depend on the particle size and shape. Gradient-hardening significantly alter the stress and plastic strain distributions near the particle-matrix interface.

Asymptotical Approach to Initial Yielding Surface and Elastoplasticity of Heterogeneous Materials

This paper presents an asymptotical approach for the prediction of the initial yielding surface, overall instantaneous moduli, and elastoplastic behavior of metal matrix composites. Considering the size of the microstructure as a small parameter, we can formulate a variational statement of the unit cell through an asymptotic expansion of an energy functional. To handle realistic microstructures, we implement this new model using the finite element method. For model validation, we used a few examples to demonstrate the application and accuracy of this theory and companion code.

High Temperature Tribological Behaviour of Metal Matrix Composites Produced by SPS

Materials used as friction components in transportation field are subjected to extreme working conditions: they rapidly reach their structural limits and critical parts require to be regularly replaced. Alternative solutions withstanding higher operating conditions imply to find innovative materials. Steel matrix composites including various solid lubricants, WS2 and h-BN, able to support high temperatures were developed using a Spark Plasma Sintering technique, which makes possible the formation of new microstructures out of reach by conventional means. Sliding tests were conducted using a pin-on-disc tribometer in air at 450°C, with a normal load of 15 N and various velocities ranged from 0.1 to 1.5 m/s. Influence of solid lubricant content and sensitivity to test parameters were studied in terms of friction and wear responses of the contacting materials. Test results reveal an improvement of friction properties for composites containing highest WS2contents. A reduction of wear is quantified for all composites, and the best behaviour is observed for those that contain WS2. In agreement with the third body approach, interpretations are proposed to describe the interphase dynamics within the contact.

Investigation of the Machining Behavior of Metal Matrix Composites (MMC) Using Chip Formation Simulation

The machining of metal matrix composites (MMC) induces cyclic loadings on tools, which creates new challenges for machining. In particular the distributed reinforcement, consisting of silicon carbide (SiC) or aluminum oxide (Al2O3), evokes especially high mechanical loads. The development of metal matrix composites is pointing towards higher fractions of reinforcements, which affects the resulting forces and temperatures. In this regard the influence of varying particle filling degrees, particle diameters, cutting velocities and tool geometries in terms of rake angle and cutting edge radius have been investigated by means of cutting simulation. For the process a self-designed continuous remeshing routine was used for which a dual phase material behavior has been implemented. The developed simulation model enables investigations of the machining behavior of metal matrix composites to the extent that ideal process strategies and tool geometries can be identified by multiple simulations.

Micromechanical modelling of the elastoplastic behaviour of nanodispersed elastomer particle-modified PA 6

In this study the elastoplastic behaviour of nanodispersed elastomeric copolymer particle-modified PA6 is investigated. Micromechanical modelling is proposed to predict the elastoplastic response of the PA6/elastomer composite under uniaxial tensile loading.A 3D self-consistent embedded unit cell model is chosen in this work which has been successfully applied for simulating the mechanical behaviour of metal matrix composites (MMCs). This model is applied for the first time to evaluate the elastoplastic behaviour of PA6 matrix composites with varying volume fractions of elastomer. The elastomer particles are idealistically assumed to be spherical. In the model a circular inclusion is surrounded by the PA6 polymer matrix, which is again embedded in the PA6/elastomer composite. This cell was subjected to uniaxial loading. The mechanical behaviour is determined iteratively in a self-consistent manner using updated elastic–plastic data as new input.A detailed experimental procedure (uniaxial tensile tests in combination with the ARAMIS high speed camera systems) for determining the true stress–strain curves of the matrix and the elastomer as input data for the simulation is reported. In addition, a numerical surface model based on the real structure of the elastomer particles is studied numerically for comparison. Two analytical micromechanical composite models are chosen for evaluating the elastic performance of the composite. The predictions from the 3D self-consistent embedded unit cell model are in good agreement with the experimental results.

Statistical analysis of the fracture strengths of aluminum alloy–alumina (Al2O3) particulate composites

The mechanics of composite materials and their “fracture behaviors” are relatively complex phenomena to analyze and establish due to their inconsistent process stability and reliability, combined with production and related processing problems. In this work, an attempt has been made to statistically analyze the tensile behavior of metal matrix composites. Composites of aluminum alloy containing 5–20% volume fraction of Al2O3 particles of 15 µm size were prepared by adding alumina particles to a vigorously agitated semi-solid aluminum alloy. Prior to this, alumina particles were subjected to preheating at 800 °C for 5 h. Particles were then added to the aluminum alloy and further heated to 850 °C by using a mixer in a nitrogen medium. A total of 20 tension tests were performed for each volume fraction according to ASTM Standards B557 and using these test data, the initial estimators for an empirical model were obtained. Using this empirical model, the reliability of the composite characteristics in terms of its tensile strength was assessed. Another significant implication of the present study is proving the ability and utility of the Weibull statistical distribution for describing the experimentally measured data on the tensile strength of metal matrix composites, in a more appropriate manner.