Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-07-14
2001-12-11
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S368000, C428S378000, C428S375000, C428S379000, C428S500000, C428S514000, C428S614000, C174S1130AS, C174S11900R, C164S091000, C164S097000, C164S100000, C164S105000, C164S501000
Reexamination Certificate
active
06329056
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to composite wires reinforced with substantially continuous fibers within a metal matrix and cables incorporating such wires.
BACKGROUND OF THE INVENTION
Metal matrix composite's (MMC's) have long been recognized as promising materials due to their combination of high strength and stiffness combined with low weight. MMC's typically include a metal matrix reinforced with fibers. Examples of metal matrix composites include aluminum matrix composite wires (e.g., silicon carbide, carbon, boron, or polycrystalline alpha alumina fibers in an aluminum matrix), titanium matrix composite tapes (e.g., silicon carbide fibers in a titanium matrix), and copper matrix composite tapes (e.g., silicon carbide fibers in a copper matrix).
The use of some metal matrix composite wires as a reinforcing member in bare overhead electrical power transmission cables is of particular interest. The need for new materials in such cables is driven by the need to increase the power transfer capacity of existing transmission infrastructure due to load growth and changes in power flow due to deregulation. Basic performance requirements for such new materials include corrosion resistance, environmental endurance (e.g., UV and moisture), resistance to loss of strength at elevated temperatures, and creep resistance.
Important properties for performance are elastic modulus, density, coefficient of thermal expansion, electrical conductivity, and strength. These properties are typically governed by the choice and purity of constituents (i.e., the metal matrix material and the fiber) in combination with the fiber volume fraction. Of these properties, emphasis has been placed on the development of wires made from fibers with high tensile strength and stiffness.
The presence of imperfections in the wire such as intermetallic phases, porosity as a result, for example, of shrinkage or internal gas (e.g., hydrogen or water vapor) voids, and particularly dry (i.e., uncoated) fiber, are known to decrease properties such as strength the of the wire. These imperfections can result from impurities in constituents (i.e., material of the metal matrix and the fiber), incompatibility of constituents, as well as incomplete infiltration of the matrix material into the fibers.
There is a need for substantially continuous metal matrix composite wire with consistently good mechanical properties.
SUMMARY OF THE INVENTION
The present invention relates to substantially continuous fiber metal matrix composites. Embodiments of the present invention pertain to metal matrix composites (e.g., composite wires) having a plurality of substantially continuous, longitudinally positioned fibers contained within a metal matrix. Metal matrix composites according to the present invention are formed into wires exhibiting desirable properties with respect to elastic modulus, density, coefficient of thermal expansion, electrical conductivity, and strength.
The present invention provides a metal matrix composite wire that includes at least one tow (typically a plurality of tows) comprising a plurality of substantially continuous, longitudinally positioned fibers in a metal matrix. The fibers are selected from the group of ceramic fibers, carbon fibers, and mixtures thereof. The melting point of the metal matrix material is not greater than 1100° C. (typically, not greater than 1000° C., and may not be greater than 900° C., 800° C., or even 700° C.). Significantly, the wire has a length of at least 300 meters (preferably, in order of preference, at least about 400 meters, at least about 500 meters, at least about 600 meters, at least about 700 meters, at least about 800 meters, at least about 900 meters, and at least about 1000 meters) and a bend failure value of zero. By this it is meant that the wire exhibits zero breaks over a length of at least 300 meters (preferably, in order of preference, at least about 400 meters, at least about 500 meters, at least about 600 meters, at least about 700 meters, at least about 800 meters, at least about 900 meters, and at least about 1000 meters) when tested according to the “Wire Proof Test” described in the Examples.
In another embodiment there is provided a method of making the composite wires according to the present invention. This method includes providing a contained volume of molten metal matrix material; imparting ultrasonic energy to cause vibration of at least a portion of the contained volume of molten metal matrix material; immersing at least one tow (typically a plurality of tows) comprising a plurality of substantially continuous fibers into the contained volume of melted matrix material, wherein the fibers are selected from the group of ceramic fibers, carbon fibers, and mixtures thereof; imparting ultrasonic energy to cause vibration of at least a portion of the contained volume of molten metal matrix material to permit at least a portion of the molten metal matrix material to infiltrate into the plurality of fibers such that an infiltrated plurality of fibers is provided; and withdrawing the infiltrated plurality of fibers from the contained volume of molten metal matrix material under conditions which permit the molten metal matrix material to solidify to provide a metal matrix composite wire according to the present invention.
In yet another embodiment, there is provided a cable that includes at least one metal matrix composite wire according to the present invention.
DEFINITIONS
As used herein, the following terms are defined as:
“Substantially continuous fiber” means a fiber having a length that is relatively infinite when compared to the average fiber diameter. Typically, this means that the fiber has an aspect ratio (i.e., ratio of the length of the fiber to the average diameter of the fiber) of at least about 1×10
5
, preferably, at least about 1×10
6
, and more preferably, at least about 1×10
7
. Typically, such fibers have a length on the order of at least about 50 meters, and may even have lengths on the order of kilometers or more.
“Longitudinally positioned” means that the fibers are oriented in the same direction as the length of the wire.
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Carpenter Michael W.
Deve Herve E.
McCullough Colin
Werner Paul S.
3M Innovative Properties Company
Brady Arthur J.
Gray J. M.
Kelly Cynthia H.
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