Showing papers on "Metal matrix composite published in 1987"

Method for laser beam welding metal matrix composite components

Abstract: A substantially homogeneous metal matrix composite conduction weld between first and second metal matrix composite components is formed by placing the components into abutting position, with a major portion thereof spaced from each other, and directing a laser beam through the spacing onto the intersection and oscillating the beam across the intersection to form a shallow pool of metal matrix composite while feeding a metal matrix composite filler wire into the pool. The laser beam and filler wire are moved along the intersection such that solidification of the molten pool containing the filler wire metal matrix composite is effected, to form the weld line, without separation of the metal matrix composite into separate phases. The filler wire may be preheated and pressure may be applied, either to one or both components in a direction transverse the plane of the intersection or to the weld line in the direction of the plane of the intersection.

A computer simulation of strength of metal matrix

Abstract: The deformation and fracture behavior of metal matrix composites with a reaction layer at the fiber-matrix interface was studied by means of a computer simulation experiment, using a two-dimensional model, and the results of the simulation experiment were compared with the predictions based on the single fiber model, which has been proposed to describe the reduction of strength of composites due to a reaction layer. In the simulation experiment, the composite was regarded as an assembly of single fiber elements, in which, for each element, the reaction layer introduces a notch on the fiber surface when it is broken, which reduces the strength of the fiber if the thickness of the layer is thinner than a critical value, as has been studied by using the single fiber model. The strength of composites was reduced with increasing thickness of the reaction layer and the fracture mode became catastrophic. The strength values obtained by the simulation were equal to those based on the single fiber model only when the fracture of the fiber was caused by the extension of the notch having been introduced by premature fracture of the reaction layer. In other cases, the strength values of the simulation were lower than those predicted by the single fiber model, although the single fiber model gave approximate values.

Method of producing titanium aluminide metal matrix composite articles

Abstract: A method for fabricating an improved titanium alloy composite consisting of at least one high strength/high stiffness filament or fiber embedded in a titanium-aluminum base alloy matrix which comprises the steps of providing a rapidly-solidified foil made of the titanium-aluminum base alloy, fabricating a preform consisting of alternating layers of the rapidly-solidified foil and the filamentary material, and applying heat and pressure to consolidate the preform, wherein consolidation is carried out at a temperature below the beta-transus temperature of the alloy.

Interaction of Al-Si, Al-Ge, and Zn-Al eutectic alloys with SiC/Al discontinuously reinforced metal matrix composites

Abstract: Interactions between Al-Si, Al-Ge, and Zn-Al eutectic alloys with SiC whisker-reinforced aluminium metal matrix composites were studied as a function of temperature above the eutectic melting temperature. Penetration extended several millimetres into the composite for the Al-Si and Al-Ge alloys but was restricted to a thin surface layer (50 μm) for the Zn-Al alloy. The extent of the penetration zone for the aluminium alloys containing silicon and germanium was also affected by the thermal-mechanical treatment of the composite: limited penetration was observed for hot-pressed material whereas extensive penetration was observed for mechanically worked material. Mechanisms for the observed phenomena are discussed in terms of the wettability of the SiC whiskers by the eutectic alloys, the formation of channels during mechanical working as well as the fine grain size of the composite.

Microstructural characterization of a silicon carbide whisker reinforced 2124 aluminium metal matrix composite

Abstract: The microstructure of a silicon carbide whisker (SiCw) reinforced 2124 aluminium metal matrix composite was characterized using scanning transmission electron microscopy (STEM). The SiC whiskers ranged in length from approximately 2 to 10 µm, and demonstrated good bonding to the aluminium matrix. In a few cases, the interface between SiC whiskers and the aluminium matrix exhibited wavy characteristics. The size of subgrains in the aluminium matrix was found to be dependent upon that of SiC whiskers. In addition, two types of intermetallic compounds were observed in the composite.

Metal matrix composite and structure using metal matrix composites for electronic applications

Abstract: The invention relates to a metal matrix composite used to support and/or enclose discrete electronic semiconductor devices, monolithic integrated circuits, hybrid circuits, and multi-layer printed wiring boards. The matrices herein disclosed employ aluminum as the matrix with Beta Eucryptite as the additive in a volume percent of up to 60. The preferred range of from 55 to 45 percent by volume of the additive has a coefficient of thermal expansion matching the common semiconductor materials and common ceramics used for electronic enclosures. The composite uses low cost materials, and due to the affinity of the additive to aluminum is easily prepared. The resulting structures have good thermal conductivity and low weight.

A viscoplastic constitutive theory for metal matrix composites at high temperature

Abstract: A viscoplastic theory is presented for representing the high-temperature deformation behavior of metal matrix composites. The point of view taken is a continuum one where the composite is considered a material in its own right, with its own properties that can be determined for the composite as a whole. It is presumed that a single preferential (fiber) direction is identifiable at each material point (continuum element) admitting the idealization of local transverse isotropy. A key ingredient in this work is the specification of an experimental program for the complete determination of the material functions and parameters for characterizing a particular metal matrix composite. The parameters relating to the strength of anisotropy can be determined through tension/torsion tests on longitudinally and circumferentially reinforced thin-walled tubes. Fundamental aspects of the theory are explored through a geometric interpretation of some basic features analogous to those of the classical theory of plasticity.

Pellet for fabricating metal matrix composite and method of preparing the pellet

Abstract: A pellet for fabricating a metal matrix composite is made of a mixture of a matrix member of a metal powder and at least one reinforcement selected from whiskers, short fibers and suitable particles, the reinforcement being uniformly distributed in a matrix of the metal powder and said mixture being kept in a shape with a binder, wherein said pellet has a surface layer of dried and rigid portion of said mixture which is rigid enough to keep its shape under an external pressure applied thereto. The pellet is formed from a flat cake of the mixture separated from a slurry consisting of a solution medium and the mixture dispersed therein uniformly. Alternatively, the pellet is formed from the mixture in a dried condition with a granulation binder diluted with a solution medium.

Corrosion Behavior of SiC Reinforced Aluminum Alloys

Abstract: : The corrosion behavior of SiC reinforced aluminum alloys exposed to chloride environments is reported herein. Electrochemical techniques were used to characterize corrosion behavior. Corrosion topography was investigated using scanning electron microscopy and energy dispersive X-ray spectroscopy. The effect of heat treatment on the corrosion behavior of SiC/AA-2124 was investigated. Resulted indicate that C u intermetallics strongly influence corrosion. Keywords: Metal matrix composite; Pitting; SiC; Aluminum; NaCl; Stress corrosion cracking; Intermetallic.

Fatigue damage accumulation in various metal matrix composites

Abstract: The purpose of this paper is to review some of the latest understanding of the fatigue behavior of continuous fiber reinforced metal matrix composites. The emphasis is on the development of an understanding of different fatigue damage mechanisms and why and how they occur. The fatigue failure modes in continuous fiber reinforced metal matrix composites are controlled by the three constituents of the system: fiber, matrix, and fiber/matrix interface. The relative strains to fatigue failure of the fiber and matrix will determine the failure mode. Several examples of matrix, fiber, and self-similar damage growth dominated fatigue damage are given for several metal matrix composite systems. Composite analysis, failure modes, and damage modeling are discussed. Boron/aluminum, silicon-carbide/aluminum, FP/aluminum, and borsic/titanium metal matrix composites are discussed.

Reduction of the Friction Coefficient of Metal Matrix Composite Under Dry Conditions

Abstract: Etude de la reduction du coefficient de frottement des composites a matrice metallique et d'une nouvelle methode de production de ces composes. Utilisation de la microscopie electronique a balayage pour caracteriser les etats de surface apres les tests d'usure

Metal matrix composites - Their time to shine?

Abstract: Basic types of metal matrix composite (MMC) systems (namely, the particulates-, the whisker/flakes-, and the continuous-fiber-reinforced) are discussed together with the advantages and the disadvantages of each system. Special consideration is given to the new MMC systems under development that meet the needs of aerospace applications and to the properties of stiffness and thermal expansion of these systems. As a family of structural materials, MMCs have great potential for missile airframe applications.

Considerations for Designing with Metal Matrix Composite Materials

Abstract: This paper presents a methodology that is based upon the concepts of structural indices for the selection of metal matrix composite (MMC) materials. General design considerations of technical criteria and operational and cost criteria are discussed briefly. Relevant MMC material properties equations are given in a table. The structural indices that are used to calculate ratios between MMC and conventional material to compare weight to strength, impact resistance, efficiency of columns and plates, flexural rigidity, and structural efficiency indices for plates and shells are then discussed.