Showing papers on "Metal matrix composite published in 1995"

The mechanical response of a 6061-T6 A1/A12O3 metal matrix composite at high rates of deformation

Abstract: The mechanical properties of a 6061-T6 aluminum alloy reinforced with a 20 vol.% fraction of alumina particles and of an unreinforced 6061-T6 alloy are studied over a range of strain rates (10-4to 6 x 105s-1) using quasistatic compression, compression and torsion Kolsky Bars, and high strain rate pressure-shear plate impact. At a given strain rate the composite displays increased strength but essentially the same strain hardening as the matrix. However, the composite displays a stronger rate-sensitivity than does the unreinforced alloy at high rates of deformation (>103s-1). The rate-sensitivity of the unreinforced alloy is shown to be largely the result of the imposed strain rate rather than of the rate history. For quasistatic deformations, a model proposed by Bao et al. (1991) describes the behavior of the composite fairly accurately given the behavior of the unreinforced alloy. This paper presents an extension of the model that is able to predict the dynamic behavior of the composite given the dynamic response of the monolithic alloy.

Feasibility of aluminium nitride formation in aluminum alloys

Abstract: The feasibility of forming aluminum nitride by in situ reactive nitrogen gas injection into molten aluminum alloys has been evaluated both analytically and experimentally over the temperature range from 700 to 1500°C. It is shown that aluminum nitride can be melt formed in the presence of Mg and Si, with nitrogen and/or ammonia as the reactive gases at temperature above 1100°C. In this role, magnesium serves as a catalyst. Magnesium niride is first formed in the vapor phase by the reaction of vaporized magnesium and nitrogen gas, followed by incorporation of magnesium nitride particles into the molten aluminum. Via an in situ substitution reaction, aluminum nitride forms between magnesium nitride and aluminum. Up to 17 wt.% aluminum nitride in an aluminum alloy has been formed with an average reinforcement size of 3 μm. The potential for this process permits economical liquid phase processing of aluminum nitride-aluminum metal matrix composite with nitrogen gas injection for structural, thermal and wear applications.

Weibull modelling of particle cracking in metal matrix composites

Abstract: An investigation into the occurrence of reinforcement cracking within a particulate ZrO 2 /2618 Al alloy metal matrix composite under tensile plastic straining has been carried out, special attention being paid to the dependence of fracture on particle size and shape. The probability of particle cracking has been modelled using a Weibull approach, giving good agreement with the experimental data. Values for the Weibull modulus and the stress required to crack the particles were found to be within the range expected for the cracking of ceramic particles. Additional information regarding the fracture behaviour of the particles was provided by in situ neutron diffraction monitoring of the internal strains, measurement of the variation in the composite Young's modulus with straining and by direct observation of the cracked particles. The values of the particle stress required for the initiation of particle cracking deduced from these supplementary experiments were found to be in good agreement with each other and with the results from the Weibull analysis. Further, it is shown that while both the current experiments, as well as the previous work of others, can be well described by the Weibull approach, the exact values of the Weibull parameters so deduced are very sensitive to the approximations and the assumptions made in constructing the model.

The application of polycrystalline diamond (PCD) tool materials when drilling and reaming aluminium based alloys including MMC

Abstract: Following a review of metal matrix composite (MMC) materials and production methods, the paper outlines the development and application of PCD cutting tools. Experimental data are presented for the drilling and single blade reaming of aluminium-silicon alloys containing 7% and 13% silicon and aluminium 2618 MMC alloy reinforced with 15 vol% silicon carbide (SiC) particulate. Though initially aimed only at aerospace and defence products, MMCs have progressively moved into higher volume applications and are currently under evaluation for volume automotive components. Compared with standard hypoeutectic and hypereutectic cast aluminium-silicon alloys, tool wear when machining MMC is shown to be up to seven times more severe. Tools used for drilling include HSS-M2, diamond plated HSS, WC, TiN coated WC and PCD. Other than when using PCD drills, tool life was extremely short due to the abrasive nature of the (SiC) reinforcement. Similarly, results from PCD reaming tests confirmed that diamond tooling provides the only realistic tooling option.

Experimental Damage Investigation of a SiC-Ti Aluminide Metal Matrix Composite

Abstract: Experimental investigations and procedures for the determination of damage are presented for the macro- and micro-analysis of SiC-Titanium Aluminide metal matrix composite (MMC). Uniaxial tension tests are performed on laminate specimens of two different layups. The layups are balanced symmetrically and given as (0/90)s and (±45)s, each containing four plies. Dogbone shaped flat plate specimens are fabricated from each of the layups. Specimens for the different layups are loaded to various load levels ranging from rupture load down to 70% of the rupture load at room temperature. By loading specimens to various load levels damage evolution is experimentally evaluated through a quantitative micro-analysis technique. Micro-analysis is performed using scanning electron microscopy (SEM) on three mutually perpendicular representative cross sections of all specimens for the qualitative and quantitative determination of damage. Together these representative cross sections form a representative volume element (RVE...

A cost-effective P/M titanium matrix composite for automobile use

Abstract: The aim of the present study is to obtain a new high-performance titanium matrix composite appropriate for automobile parts using a new low-cost powder metallurgy process. The results can be summarized as follows: (1) A production process was developed for a sintered titanium alloy from cheap, low-purity titanium powder (sponge fines) which in its as-sintered form (without expensive hot isostatic pressing or heat treatment) achieves superior fatigue properties to hot-isostatic-pressed titanium alloy made from expensive high purity hydride-dehydride titanium powder. (2) TiB was found to be a superior reinforcing compound for blended elemental titanium matrix composites than SiC, B4C, TiAl, TiB2, TiN and TiC tested previously and it was used in the above low-cost production process to make the new disperse-particle titanium matrix composites. (3) The developed titanium matrix composite allows considerably cheaper production of parts from titanium alloy than by conventional ingot forging methods and was confirmed to be far superior to conventional titatium alloys in tensile strength, fatigue properties, rigidity, heat resistance, and wear resistance.

Dynamic recrystallization in a thermomechanically processed metal matrix composite

Abstract: Microstructural development and dynamic recrystallization behaviour of the recently developed high strength magnesium alloy ZC71 (7% Zn, 1% Cu, 0.5% Mn) and the composite ZC71-12%SiCp (where SiCp denotes particulate SiC) have been studied. The grain size and growth in the die-cast, extruded (80%), solution-heat-treated and aged conditions were examined by transmission and scanning electron microscopy and light microscopy. In the alloy, dynamic recrystallization took place during extrusion. In the composite the SiC particles provided more nucleation sites for the new recrystallized grains. After extrusion, during the solution and ageing heat treatment at 440 °C and 200 °C respectively, no apparent effect of the eutectic stringers on grain growth was observed in either the alloy or the composite. Grain growth occurred in the alloy, but in the composite this was inhibited by the SiC particles. This is mainly because several boundaries were surrounded by the particles and thus grain growth was limited. Despite the very fine grain size, the grain structure is stable in the composite during long-term treatment at 200 °C.

Continuous-fiber reinforced composites: A new generation

Abstract: The mechanical and physical properties of aluminum-matrix composites reinforced with high-performance continuous alumina fibers are reviewed and compared with those of other structural materials. Continuous-fiber reinforced aluminum-matrix compositesoffer outstanding improvements in specific strength and specific stiffness over conventional alloys and particulate composites. Thelongitudinal tensile strength of an aluminum matrix reinforced with 55–65 vol.% alumina fibers is in the range ofl.4-1.9 GPa, the longitudinal Young's modulus is 220–240 GPa, and the density is 3.2-3.4 g/cm3. The mechanisms of strengthening and fracture under longitudinal, transverse, and shear loading are reviewed. Examples of applications are presented that are representative of the range of product forms being developed.

Dynamic mechanical analysis of prestrained Al2O3/Al metal-matrix composite

Abstract: The effect of prestraining on the elastic modulus,E, and damping capacity, tanφ, of 10 and 20 vol% Al2O3 particle-reinforced composites has been investigated as function of temperature using dynamic mechanical analysis. Both elastic modulus and damping capacity were found to increase with volume fraction. At 10 vol% the modulus and damping were relatively insensitive to prestrain. However, at 20 vol% it was observed that the modulus decreased with increasing prestrain while damping increased significantly. These results are discussed in terms of fraction of broken particles, particle size, and differential in thermal expansion between the matrix and Al2O3 particulate.

Method of producing structural metal matrix composite products from a blend of powders

Abstract: A method of preparing a metal alloy product from a powder blend. The method comprising: (a) cold pressing a blend to form a compact, the metal blend comprising a metal powder phase and at least one reinforcement phase having a hardness greater than the metal phase; (b) heating the compact to form a preheated compact; and (c) hot working the heated compact. In a preferred method, the powder metal blend comprises 50 to 90 vol. % of an aluminum alloy powder and 10 to 50 vol. % of silicon carbide; the heating of the compact perforated in a nitrogen atmosphere to form a preheated compact; and the extruded hot compact is hot worked. Hot working may take the form of forging, rolling, upset forging, exuding, compacting or other processes known in the art.

Counteraction of particulate segregation during transient liquid-phase bonding of aluminium-based MMC material

Abstract: Particle segregation during transient liquid-phase bonding of aluminium-based metal matrix composite material using copper filler metal was investigated Segregation was promoted by the slow movement of the solid-liquid interface during isothermal solidification and alumina particles with diameters less than 30 Μm were segregated when the copper foil thickness exceeded 5 and 15 Μm for the base metals examined When bonding at 853 K, the liquid widths produced using these copper foil thiciknesses were almost identical to the median inter-particle spacing in the base metals investigated When the amount of liquid formed at the bonding temperature decreased below a critical level, the test specimens broke apart immediately following the joining operation The minimum film thickness of copper for satisfactory joint strength increased from 06 Μm to 24 Μm, when the heating rate to the bonding temperature decreased from 1 Ks−1 to 001 Ks−1

Laser processing to createin-situ Al-SiCp surface metal matrix composites

Abstract: When SiC particulate (SiCp) is preplaced on an aluminium alloy surface, a molten zone can be formed in the aluminium specimen by laser processing, and there is a possibility of producing anin-situ Al-SiCp metal matrix composite (MMC) layer on the surface, which will modify the surface properties. Under specific laser processing conditions in the present work, a smooth and continuous Al-SiCp MMC layer was developed on the surface with well-distributed and embedded SiCp in the layer. In most cases, the SiCp partially dissolved in the liquid and reprecipitated during the solidification. The dissolution of the SiCp is discussed, and the precipitate in the present work is identified as Al4SiC4. The thickness of the Al-SiCp MMC layer was limited to 30–50 Μm when SiCp was preplaced on the specimen. The mechanism of both the formation of the Al-SiCp and the limitation of the MMC layer thickness in this process was studied.

Particulate segregation and mechanical properties in transient liquid phase bonded metal matrix composite material

Abstract: Thefactors determining particulate segregation and joint shear strength in transient liquid phase (TLP) bonded aluminium based metal matrix composite (Mj1C) material are examined in the present paper. Three situations are evaluated during TLP bonding, namely, where the liquid width is unrestrained at the bonding temperature, where the liquid width is maintained constant, and where liquid is continuously expelled from the bondline region during the joining operation. Similar experimental and numerically calculated liquid width values are found during unrestrained liquid width TLP bonding (at the start of the isothermal solidification period). However, the calculated rate constant during isothermal solidification is smaller than in experimental testing. When liquid is expelled from the joint interface during TLP bonding at 853 K, the liquid width attains a constant value of ~55 μm. Although the completion time for isothermal solidification is substantially decreased when liquid is expelled from the ...

Brake rotors and methods for making the same

Abstract: This invention relates to metal and ceramic matrix composite brake rotors comprising an interconnected matrix embedding at least one filler material. In the case of metal matrix composite materials, the at least one filler material comprises at least about 26% by volume of the brake rotor for most applications, and at least about 20% by volume for applications involving passenger cars and trucks. In a preferred embodiment of the present invention, the metal matrix composite brake rotor comprises an interconnected metal matrix containing at least about 28% by volume of a particulate filler material and more preferably at least about 30% by volume. Moreover, the composite rotors of the present invention exhibit a maximum operating temperature of at least about 900° F. and preferably at least about 950° F. and even more preferably at least about 975° F. and higher.

Metal matrix composites containing electrical insulators

Abstract: A method of fabricating a metal matrix composite containing electrically isolated areas and the MMC formed from the method. The method comprises: (a) providing a liquid pool of unreinforced aluminum alloy; (b) infiltrating the unreinforced aluminum alloy into a stack comprising upper and lower porous preforms and an electrical insulator material placed between the preforms; (c) solidifying the liquid-phase metal to form a metal matrix composite product that completely surrounds the stack; and (d) forming at least one groove in the solidified metal, the groove extending downward to the insulating substrate so as to electrically isolate at least one region on the surface of the metal matrix composite.

In situ x-ray CT under tensile loading using synchrotron radiation

Abstract: Internal damage in metal matrix composite (MMC) under static tensile loading was observed by in situ x-ray computed tomography based on synchrotron radiation (SR-CT). A tensile testing sample stage was developed to investigate the fracture process during the tensile test. Aluminum alloy matrix composites reinforced by long or short SiC fibers were used. The projection images obtained under tensile loading showed good performance of the sample stage, and matrix deformation and breaks of the long SiC fibers could be observed. In the CT images taken at the maximum stress just before failure, debondings of the short SiC fibers to the matrix, many pullouts of the fibers, and matrix cracking could be clearly observed. The in situ SR-CT allowed the observation of generation and growth of such defects under different tensile stress levels. The results from the nondestructive observation revealed that the MMC was broken by propagation of the matrix cracks which might be caused by stress concentration at the ends of the short fibers. A three-dimensional CT image reconstructed from many CT images provided easy understanding of the fiber arrangement, crack shape, and form of the void caused by fiber pullout. In situ SR-CT is a useful method for understanding failure mechanisms in advanced materials.

Study of the damage mechanisms in an OSPREY™ Al alloy-SiCp composite by scanning electron microscope in situ tensile tests

Abstract: Damage mechanisms in a 7049 Al alloy + 15% SiC p metal matrix composite were studied qualitatively and quantitatively by in situ tensile tests in a scanning electron microscope with gold microgrids deposited onto the surface of the specimen. The first damage mechanisms were found to be rupture of the most elongated particles and, in smaller proportion, decohesion of the particle-matrix interface. A high aspect ratio, large size and low local volume fraction of particles appeared to increase the cracking probability. An Eshelby iterative method modified to account for the elastoplastic behaviour of the matrix was used to calculate the stress field induced by the thermomechanical treatment and mechanical loading of the composite. Knowledge of the statistical characteristics of the damaged particles permitted estimation of the critical stress for the two observed damage initiation mechanisms. In the case of particle cracking this stress depends on the particle size.

Ultrasonic wave scattering from fiber-matrix interphases

Abstract: The elastic scattering from a multilayered (three‐phase) fiber embedded in a matrix is studied for longitudinal and transverse wave incidence. Different simplified approximations to the problem using an equivalent homogeneous fiber and spring boundary conditions between the matrix and the fiber are considered. Such approximations are shown to be sufficient at klr<1.5 for longitudinal and ktr<3.0 for transverse incident waves. The numerical and experimental results are given for a SiC/Ti metal matrix composite focusing on the effect of an imperfect interface between the fiber and the matrix. Numerical examples show that scattering is significantly affected by the interfacial stiffnesses and thus can be used for interface characterization. The experiments were performed on a SiC/Ti unidirectional composite with fiber fraction 23.6%. The measured frequency dependence of attenuation for a longitudinal wave is found in the low‐frequency range (klr<1) to be close to that predicted by the independent scattering ...

Brake rotors, clutch plates and like parts and methods for making the same

Abstract: This invention relates to metal and metal matrix composite materials that are useful as, for example, brake rotors, clutch plates and other similar uses which benefit from material properties of the invention. In the case of metal matrix composite materials, clutch plates and brake rotors made according to the invention comprise an interconnected matrix metal embedding at least one filler material. For example, the at least one filler material comprises numerous acceptable filler materials present in a sufficient quantity to provide desired performance. The brake rotors and clutch plates according to the invention further comprise a coating on the surface thereof causing the metal or metal matrix composite body to function as a substrate. The coatings may be applied by various conventional techniques. Desirable results of placing a coating on a metal or metal matrix composite substrate brake rotor or clutch plate include a significant increase in the maximum operating temperature of the brake rotor or clutch plate and/or a significant reduction in weight in comparison to conventional materials, etc.

Abrasion resistance of in situ Fe-TiC composites

Abstract: Metal matrix composites containing a high volume fraction of carbide, nitride, boride, and/or oxide particles are frequently the materials of choice for applications which require high wear resistance. It is the very hard second phase particles which imbue the metal matrix composite with its superior wear resistance. For example, additions of titanium carbide (TiC), one of the hardest of the carbides with a Vickers hardness of 19.6--31.4 GPa, can be used to improve the abrasion resistance of iron alloys. In the present study in situ metal matrix composites, containing between 23 and 31 volume percent carbides, were produced from Fe-Ti-C and Fe-Cr-Ti-C melts, and their abrasion resistance was compared with that of unreinforced Fe and a white cast iron using a high-stress pin abrasion test.

Materials Processing Defects

Abstract: Some comments on the structure of technology of plasticity in R&D and production, K. Lange James Nasmyth (1808-1890) - the steam hammer and the mechanics of vee-anvil forging, W. Johnson modelling dynamic strain localization in inelastic solids, M. Predeleanu void growth under triaxial stress state and its influence on sheet metal forming limits, R.C. Chaturvedi the prediction of necking and wrinkles in deep-drawing processes using the FEM, E. Doege et al constitutive models for microvoid nucleation, growth and coalescence in elastoplasticity, finite element reference modelling, J. Oudin et al theoretical and numerical modelling of isotropic or anisotropic ductile damage in metal forming processes, J.C. Gelin research on forging processes for production [alpha] + [beta] titanium alloy TC11 disks, S. Chen et al modelling of fracture initiation in metalforming processes, Y.Y. Zhu et al formability determination for production control, J.A. Schey design of experiments, a statistical method to analyse sheet metal forming defects effectively, D. Bauer and R. Leidolf formability, damage and corrosion resistance of coated steel sheets, J.Z. Gronostajski and Z.J. Gronostajski model of metal fracture in cold deformation and ductivity restoration by annealing, V.L. Kolmogorov prediction of necking in 3-D sheet metal forming processes with finite element simulation, M. Brunet deformability versus fracture limit diagrams, A.G. Atkins prediction of geometrical defects in sheet metal forming processes by semi-implicit FEM, A. Makinouch and M. Kawka evolution of structural anisotropy in metal forming processes, J. Tirosh computer aided design of optimised forgings, S. Tichkiewitch defects in thermal sprayed and vapour deposited thick and thin hardwearings coatings, M.S.J. Hashmi a study of workability criteria in bulk forming processes, A.S. Wifi et al degradation of metal matrix composite under plastic straining, N. Kanetake and T. Choh crack prevention and increase of workability of brittle materials by cold extrusion, H.W. Wagener and J. Haats a database for some physical defects in metal forming processes, M.M. Al-Mousawi et al split ends and central burst defects in rolling, S. Turczyn and Z. Malinowski form-filling in forging and section-rolling, P.F. Thomson et al.