SiC Metal Matrix Composites Research Articles

Natural frequency method for a quantitative measurement of damage evolution in a Ti-6AI-4V/SiC composite

The purpose of this study is to demonstrate that the measurement of elastic constants, especially the longitudinal Young's modulus, by frequency measuring, can be used as a non-destructive method to evaluate the damage in a Ti-6A1-4V/SiC metal matrix composite. Therefore, the composite was thermally cycled between 200 and 700°C, which was found to induce a decrease in the longitudinal Young's modulus by 20%. By comparison with mechanically tested samples, this decrease is shown to correspond to a point where the failure stress drops dramatically. Thus, this non-destructive method has proved successful to follow and evaluate the damage evolution. It could be applied to concrete situations such as evaluating the damage in composite components.

Modelling for the compressive strength of Al-6061/SiC MMCs

Metal matrix composites (MMCs) are a new range of advanced materials. Recently the strength of particulate reinforced MMCs have been analyzed theoretically by dislocation models which were developed originally to analyze the dispersion hardening mechanism of two-phase metals [1]. This paper presents the development of a compressive strength model for aluminium matrix composite (Al-6061/SiC) manufactured by powder metallurgy route. The mathematical prediction models for compressive strength have been developed in terms of sintering temperature, sintering time and volume fraction of reinforcement. These variables were investigated using design of experiments and response surface methodology. Response surface contours were constructed giving the response in terms of sintering temperature, time and volume fraction of reinforcement.

An experimental study of residual fiber strains in Ti-15-3 continuous fiber composites

A simplified experimental technique to determine the axial fiber residual strain in continuously-reinforced metal matrix composites is described. The residual fiber strains in two Ti-15V-3Cr-3Al-3Sn/SiC metal matrix composites have been measured with this technique. Residual fiber strains on the order of 0.2% are measured in the as-processed condition, and the residual stresses approach zero after testing the composite in tension to failure at room temperature. A conceptual description of the effect of tensile testing on the residual stresses is provided. The experimental results are consistent with predictions based on a concentric cylinder iso-strain analysis of thermal strains. Measurement errors result in a residual fiber strain error that is typically less than ±0.05%. Periodic fiber bending induced by cross-weave fibers is also analyzed, and may contribute significantly to measurement errors.

Mechanical properties and microstructure of twin roll cast Al–7Si/SiCpMMCs

AbstractUnreinforced A356 alloy (AI–7Si) and A356 metal matrix composites (MMCs) reinforced with 10 and 20 vol.-%SiC particles have been manufactured by twin roll casting, and the resulting sheet tensile mechanical properties evaluated after a variety of different heat treatments. The SiC particles show a more uniform distribution in the roll cast sheet than in the MMC feedstock, and centreline macrosegregation of eutectic Si is less marked thanfor the roll cast A356 alloy. After solution heat treatment the ductility ofunreinforced A356 and MMCs are both increased, which is beneficialfor subsequent secondary fabrication. Roll cast 10 vol.-%SiC MMC reaches the peak aged condition after 5 h at 155°C, compared with 11 hfor the unreinforced A356. Compared with the as cast strip, the peak aged MMC exhibits greater proof stress and ultimate tensile strength (UTS), although its ductility is similar. Prolonged aging for 11 h slightly improves ductility, without significantly reducing proof stress or UTS.MST/3058

Effect of atomization on the distribution of SiC particulates in spray deposited Al-7Si/SiC metal matrix composites

Effect of atomization on the distribution of SiC particulates in spray deposited Al-7Si/SiC metal matrix composites

Simulation of experimental force-displacement curves by a finite element elimination technique

A recently developed Finite Element (FE) elimination technique to simulate automatic crack propagation was used to predict experimentally measured force-displacement curves for chevron-notched three-point bending specimens with side-grooves. Numerical predictions (2D, plane strain) and experimental measurements (3D) are compared for this special notch geometry by using a calculated ‘effective width’. The FE elimination algorithm is applied to ductile failure of Al(6061)–(20vol%)SiC metal matrix composites. Macroscopic crack appearance and corresponding force-displacement curves have been successfully simulated by using a combination of critical stress and strain values as failure criterion.

A process model for friction welding of AlMgSi alloys and AlSiC metal matrix composites—I. Haz temperature and strain rate distribution

The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of AlMgSi alloys and AlSiC metal matrix composites. In Part I the different components of the model are outlined and analytical solutions presented which provide quantitative information about the HAZ temperature distribution for a wide range of operational conditions. Moreover, a general procedure for modelling the HAZ strain rate distribution has been developed by introducing a series of kinematically admissible velocity equations which describe the material flow fields in the radial, the rotational, and the axial direction, respectively. Calculations performed for both types of materials show that the effective strain rate may exceed 1000 s −1 in positions close to the contact section due to the high rotational velocities involved. Application of the model for evaluation of the response of AlMgSi alloys and AlSiC metal matrix composites to the imposed heating and plastic deformation is described in an accompanying paper (Part II).

A process model for friction welding of AlMgSi alloys and AlSiC metal matrix composites—II. Haz microstructure and strength evolution

The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of AlMgSi alloys and AlSiC metal matrix composites. In Part II the heat and material flow models presented in the first paper (Part I) are utilized for prediction of the HAZ subgrain structure and strength evolution following welding and subsequent natural ageing. The modelling is done on the basis of well established principles from thermodynamics, kinetic theory and simple dislocation mechanics. The models are validated by comparison with experimental data, and are illustrated by means of novel mechanism maps. These show the competition between the different process variables that contribute to microstructural changes and strength losses during friction welding of AlMgSi alloys and AlSiC metal matrix composites.

Uniaxial creep of long fibre reinforced metal matrix composites

A generalisation of McLean's ( Directionally Solidified Materials for High Temperature Service, 1983, The Metals Society, London) uniaxial creep model which accounts for the effects of inherent residual stresses, matrix primary creep and the treatment of the effect of possible instantaneous matrix yield upon loading is presented. The model and numerical micromechanics approach are used to analyse the uniaxial creep of Ti-6AI-4V/SiC metal matrix composites. Excellent agreement is obtained between the analytical and numerical models and predicted results are in reasonable agreement with published experimental results.

High temperature creep behavior of metal matrix AluminumSiC composites

The tensile creep behavior of AlSiC metal matrix composites has been investigated and analyzed over the temperature range from 230 to 525°C. It is shown that plastic flow in these materials is lattice-diffusion controlled dislocation creep in the aluminum matrix. All data on AlSiC have been assessed by a creep relation developed for creep of metals at constant structure with the added contribution of a threshold stress. The threshold stress for creep in AlSiC composites is not a thermally-activated process and is shown to have a linear dependence with temperature becoming zero at 470°C. The threshold stress is higher for the whisker composites than for the particulate composites. The origin of the threshold stress is not well understood and cannot be explained by contemporary dislocation models involving dislocation bowing or unpinning around particles sites. The observed interparticle-interwhisker spacing is shown to influence the creep rate in the same way as observed for mechanical alloyed (MA) Al base materials.

AES and RBS characterization of titanium silicide bilayers on SiC

physica status solidi (a)Volume 139, Issue 1 p. K39-K44 Surfaces, Interfaces, Thin Films; Lower-Dimensional Systems AES and RBS characterization of titanium silicide bilayers on SiC K. Bilba, K. Bilba Laboratoire de Chimie du Solide, Talence Search for more papers by this authorJ. P. Manaud, J. P. Manaud Laboratoire de Chimie du Solide, Talence Search for more papers by this authorJ. M. Quenisset, J. M. Quenisset Laboratoire de Chimie du Solide, Talence Search for more papers by this authorY. Lepetitcorps, Y. Lepetitcorps Laboratoire de Chimie du Solide, Talence Search for more papers by this author K. Bilba, K. Bilba Laboratoire de Chimie du Solide, Talence Search for more papers by this authorJ. P. Manaud, J. P. Manaud Laboratoire de Chimie du Solide, Talence Search for more papers by this authorJ. M. Quenisset, J. M. Quenisset Laboratoire de Chimie du Solide, Talence Search for more papers by this authorY. Lepetitcorps, Y. Lepetitcorps Laboratoire de Chimie du Solide, Talence Search for more papers by this author First published: 16 September 1993 https://doi.org/10.1002/pssa.2211390134Citations: 2 351 cours de la Libération. F-33405 Talence Cedex, France. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume139, Issue116 September 1993Pages K39-K44 RelatedInformation

Structure and behavior of metal/ceramic interfaces in Ti alloy/SiC metal matrix composites

The structure and mechanical behavior of the fiber/matrix interface in Ti alloy/SCS-6 SiC metal matrix composites were studied. In these composites the interface region consists of a fiber-coating region and a metal reaction zone between the SiC fiber body and the metal matrix. The fiber coating consists of a number of zones or layers which are comprised of cubic SiC particles in a turbostratic carbon matrix. Some ambiguity remains, concerning the number of distinct layers and the size, shape, and density of the SiC particles. The effect of composite fabrication and heat treatment on the coating structure is relatively small. Studies of the metal reaction zone adjacent to the fiber in Ti alloy/SCS-6 SiC MMC's have shown that a number of discrete zones or layers form. Nearest the fiber, a zone of cubic TiC occurs, with increasing grain size with distance from the fiber. Nearest the metal matrix, a zone of Ti5Si3 forms. In high Al content alloys, an intermediate zone forms that consists of Ti2AlC or Ti3AlC. The fiber/matrix interface plays an important role during transverse tensile loading of these composites. The tensile behavior is controlled by debonding at the interface, followed by deformation of the matrix ligaments. Replica observations show that the debonding initiates and propagates within the coating layers, but is not confined to a single layer interface.

The turning of an Al/SiC metal-matrix composite

Metal-matrix composites are a relatively new range of materials possessing several characteristics that make them useful in situations where low weight, high strength, high stiffness, and an ability to operate at elevated temperatures are required. These materials are difficult to machine, however, consisting of a hard abrasive ceramic reinforcing medium set within a more ductile matrix material. This paper presents results from a series of turning tests in which a number of different cutting-tool materials were used to machine an Al/25 vol% SiC metal-matrix composite. The influence of the cutting speed on the tool wear, the surface finish, and the cutting forces was established for each tool material. It was found that carbide tools, both coated and uncoated, sustained significant levels of tool wear after a very short period of machining. The best overall performance was achieved using a solid cubic boron nitride, CBN, insert whilst the worst was encountered using a solid silicon nitride, Sylon, tool.

The effect of quenching on the mechanical properties of powder metallurgically produced AlSiC (particles) metal matrix composites

Several factors contribute to the strengthening in particulate metal matrix composites (MMCs); their interdependence makes the elaboration of an exhaustive explanation of the phenomenon difficult. In the present work, a comparison between different powder metallurgically produced MMCs consistency of an aluminium matrix reinforced with SiC particles, both in the as-extruded state and in the quenched state, is carried out. Data concerning two powder metallurgy processes, four average particle sizes and four volume fractions of the reinforcement are analysed and compared with the unreinforced matrix. Such analysis allows a deeper understanding both about the result of the mismatch in between the thermal expansion coefficients of the matrix and of the reinforcement on dislocation density, and about the AlSiC solid state reaction. These phenomena act on the strengthening mechanism. Their effect is very specific, because it strongly depends on the SiC particle average size and volume fraction. So, the difference between the ultimate tensile strengths of the as-extruded composites and the quenched composites can change case by case. Sometimes, the improvement in mechanical properties is excellent. This gives well-grounded encouragement in study and design of a suitable heat treatment for such MMCs.

GROWTH OF FATIGUE CRACKS EMANATING FROM NOTCHES IN SiC PARTICULATE ALUMINUM COMPOSITE

Abstract— The initiation and growth of cracks emanating from blunt notches in 6061‐Al alloy reinforced with 25% particulate Sic metal matrix composite were investigated. To elucidate the role of aging condition of the matrix on the fatigue behavior, the studies were carried out at T6 and overaged conditions. The results show that the number of cycles required for initiation of fatigue cracks are not influenced with the notch severity and the aging condition of the matrix. The overaging heat treatment resulted in slower fatigue crack growth rates. The failure of the Sic particles during the fatigue process is given as the reason for the both observed initiation and crack growth characteristics. It is also shown that the growth rate of cracks emanating from blunt notches can be accurately described by an equivalent stress intensity factor range ΔKeq. This could provide an adequate engineering method for design against fatigue failure from various stress concentrations for this composite system.