JPS5912733B2 - Method of forming fiber-metal composites - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for making composite materials, particularly composite materials consisting of carbon fibers embedded in a metal matrix.

High strength, lightweight structures can be formed from composites in which filaments are embedded or consolidated in a matrix.

Carbon fibers in particular have high tensile strength and large modulus of elasticity; therefore, composites formed from a metal matrix containing such fibers oriented in the direction of maximum expected stress can withstand a wide temperature range of 15. It can easily be used for components requiring large strength-to-density ratios and large modulus-to-density ratios. Metal-graphite composites also combine the lubricity of graphite with the toughness of metal, providing a material with a low coefficient of friction and wear resistance. Composites of materials such as aluminum and copper 20 and graphite exhibit great strength and high electrical conductivity. Many metals, such as aluminum, do not readily wet graphite in their molten state.

Graphite can be wetted by molten aluminum if a layer of aluminum carbide is first formed at the metal-fiber interface 25, but such an aluminum carbide phase
It has been suggested that its thermochemical and mechanical instability makes it unacceptable. U.S. Pat. No. 3,553,820 to R.V. Sara discloses that aluminum x graphite fiber composites are prepared by first coating the fibers with a tantalum coating by electrodeposition from a molten salt bath and then subjecting them to very low pressure with a pump. It is taught that the fibers can be formed by removing gas from the fibers and dipping the degassed fibers into a pressurized molten aluminum bath filling the interstices of the fibers. U.S. Patent No. 357190 by R.V. Sara
A similar method is described in No. 1, and in this method,
Carbon fibers are first coated with silver or a silver-aluminum alloy by electrodeposition from a plating solution, then the fibers are brought into contact with aluminum foil, and the combined foil and fibers are coated under pressure with the solid phase of the foil. Heat to temperature.

In both of these methods, the metal coating is sputtered (
It has also been suggested that it could be applied by reduction of metal salts (Suptering) or metal salts. It is difficult to obtain a uniform thin coating on the fibers using silver or tantalum;
In particular, the resulting composite contains a substantial amount of expensive heavy materials such as silver and tantalum. Electrodeposition and chemical deposition methods have also been used to deposit matrix materials directly around graphite fibers, and the coated fibers are then pressed at high temperatures to form composites.

The main disadvantage of such deposition methods to form composites is that, in most cases, the matrix material is usually rather limited to pure metals, which are significantly less efficient than alloys for many purposes. It is something that has an inferior quality. The main object of the present invention is therefore to provide a simple and unique method of forming metal/graphite composites without resorting to high pressures or high temperatures.

Another object of the present invention is to provide a method of forming a unique metal/graphite composite in which the composition of the matrix material can be varied over a wide range. Still other objects of the invention will be partly obvious and partly from the following description. The invention therefore includes a method and a number of steps, the relationship between one or more of those steps, and products and compositions having interrelationships with material characteristics, properties, which are described in the following details. As illustrated in the description and in the claims.

In general, to accomplish the above and other objects, the present invention includes forming a thin, substantially uniform coating of a wetting agent, which is titanium boride, titanium carbide, or a mixture of both, on carbon fibers. .

The interstices between the coated fibers are filled with metal, which initially penetrates as a liquid under ambient pressure. Since it is not considered possible to explain the general formula of boride using ordinary concepts of valence, the term boride as used herein shall be limited to specific chemical relationships unless otherwise specified. You shouldn't think about it. For a more complete understanding of the nature and purpose of the invention, reference should be made to the following detailed description taken in conjunction with the drawings. The drawings schematically illustrate, in cross-section, a carbon fiber metal composite made in accordance with the teachings of the present invention. Although graphite fibers are preferred in the practice of this invention, the term carbon fiber is intended to include both graphitic and non-graphitic carbon fibers.

The carbon fibers used in the present invention can be made from any of a number of precursors such as pitch, rayon, polyaclonitrile, etc., in forms such as yarns, tows, and woven, knitted, or felted webs. I can do it. In a preferred form, the fibers are graphite derived from coaxial yarns of rayon with an average fiber diameter of a few microns, having about 11,000 fibers in the yarn. Such carbon fibers and fabrics are well known and commercially available, and methods of making them are also known in the art.
The composite produced according to the present invention as shown in the drawings is
It includes a plurality of graphite fibers 20 each having a substantially continuous surface coating 21 of a wetting agent that is titanium boride, titanium carbide, or a mixture of both.

Typically the diameter of the fallen fibers is about 7 microns and the coating thickness is 1.
It is about 00A thin. As a result, the relative thicknesses of the coatings in the figures have been exaggerated for clarity. The fibers are embedded in a solid metal matrix 22 that is various alloys of metals such as aluminum, magnesium, copper, lead, zinc, tin, aluminum/silicon, and the like. In order for the fiber bundle to be penetrated or enveloped by immersion in a liquid,
The liquid must wet the fiber surface.

As mentioned above, flexible metals such as aluminum and copper do not easily wet graphite. Therefore, the present invention forms a wetting agent coating on the graphite fiber surface. The coating is a substantially uniform layer of titanium boride, titanium carbide, or mixtures thereof, preferably having a thickness in the range of 100 to 10,000 Å. There are many ways to coat the fibers, but the preferred method of the present invention is a vapor phase deposition method in which the coating material is deposited as a result of simultaneous reduction of a mixture of gaseous titanium compounds and gaseous boron compounds. Contains. Vapor phase deposition methods for forming coatings are well known in the art and are typically carried out at temperatures between about 900 and 1400C. It is known that intermetallic compounds such as hafnium boride can be deposited as a coating from a mixture of gaseous hafnium chloride and boron trichloride by reduction with hydrogen gas. In the method of the present invention, the preferred vapor phase deposition method is to deposit with zinc metal vapor using a mixture of titanium tetrachloride and boron trichloride as the reducing agent.
It involves reduction at relatively low temperatures.

By using the zinc J metal, which acts as a slow reducing agent, a very wide variety of reactions can occur, thereby seeking better control over the process. For example, if the relative loading ratio of boron trichloride to boron tetrachloride in the mixture is low (i.e., less than about 1/3), the coating on the fiber will have an approximate composition as titanium carbide and substantially TiB. It will consist of a mixture with borides.

As the weight ratio increases, the composition of the deposited coating will approach TiB2. The foregoing can be explained based on the following set of hypothetical reactions that are believed to occur at the graphite fiber surface in the gas phase during the deposition process.

The first two equations are thought to represent the reduction process that occurs 2). (1) TiCl4+Zn-+TiCl2+Z
nCl2(2)2BC13+3Zn→2B+3ZnC1
Second, it is believed that the boron thus produced and the carbon of the fibers react with titanium dichloride in approximately the following manner: (3)
2TiC12-1XB-+Ti? +TiCl4(4)2
From the TiC12-1-C→TiC+TiCl4 formula (support), there is enough boron halide to provide a relatively excess boron, so that X in formula (3) has a value of about 2, The form of titanium boride formed is extremely TiB
It turns out that it is close to 2.

This latter consideration suggests that in order to obtain a satisfactory complex,
It is important that the coating of the fibers not only desirably promote wetting by the matrix metal, but also because it is desirable to provide a chemically stable interface between the fibers and the matrix metal.

For example, if the matrix metal is copper,
A coating that is a mixture of TiC and TiB is satisfactory. On the other hand, it has been found that if the matrix metal is aluminum or an alloy with a high percentage of aluminum, the coating composition should be substantially TiB2. The fibers with the required coating are then drawn through a bath containing a molten metal matrix.

As the fibers are wetted, penetration into the interstices between the fibers occurs. The total infiltration step can be carried out at ambient pressure, preferably in an inert atmosphere such as argon or the like. The metal fiber object is then cooled below the solidus temperature of the metal, thereby forming a solid composite. Composites can initially be made into wires, rods, tapes, or sheets, but they can be pressed together at temperatures above the melting point of the matrix to form bulk materials in various shapes such as rods, angle pieces, and panels. You can make ivy complexes. If desired, during pressing of such moldings, excess metal may be squeezed out of the composite to increase the volume percentage of fibers. The following implementation more clearly illustrates the method of manufacturing carbon fiber composites according to the present invention.

However, the invention should not be considered limited to the specific embodiments described in these Examples. Example 1
A graphite yarn of 50 x 106 modieras having about 11,000 single fibers was coated with 0.38% TiCl4, O. 2l%
A gas phase reaction mixture was formed from BCl3, and 0.80% Zn residual quargon (all percentages are by weight).

The gas mixture was maintained at a temperature of 650° C. for 30 minutes and approximately 200 A, which is considered to be substantially TiB2 on the yarn fibers.
A coating was formed. Does the coated fiber contain 13% silicon-aluminum alloy? It was transferred to a melt bath under argon and held at 650° C. for 2 minutes while immersed in the bath. The resulting metal-fiber composite was removed from the bath and then cooled below the solidus temperature of the alloy. A cross section taken through the composite and across the long axis of the fibers appeared substantially as shown in the drawing. A number of pieces of the composite described in this example were pressed into graphite molds under vacuum at 600° C. to form composite plates 6 inches long x 0.5 inches wide x 0.05 inches thick. .

Example 2 A graphite yarn similar to that used in Example 1 was exposed to a similar gas mixture.

However, the composition was as follows: 0.38 wt% TiCl
4, O. l4 wt% BCl2 and 0.80 wt% Zn,
remaining argon. The fibers were placed in the gas mixture at 650°C for 30
The specimen was exposed for 1 minute to form a coating consisting of a mixture of TiC and TiB and transferred under argon to a molten bath containing a bronze alloy of about 90 wt.% Cu and 10 wt.% Sn and held at about 980° C. for 1 minute. The composite was removed from the bath and cooled to form a solid article. Example 3 Coated graphite fibers were prepared as in Example 1 and coated with copper alloy (0.
The sample was transferred to a liquid crystal chamber containing 4% Ca, 99.6f6Pb) maintained at approximately 550° C. under argon.

The fibers were kept in the bath for 10 minutes, then the composite was removed and cooled below the solidus temperature of the alloy. The resulting composite could be hot pressed to form a bearing. Since certain changes may be made to the above method without departing from the scope of the invention, everything contained in the above description or shown in the drawings is intended to be illustrative only and not in a limiting sense. It shouldn't be.

Although the present invention has been described in detail above, embodiments of the present invention will be shown below.

(1) The coating step includes a reducing action of a gaseous titanium compound in the presence of the fibers, thereby producing the titanium boride or a mixture of titanium boride and titanium carbide. Method described.

(2) The coating process is applied to each of the iron fibers at approximately 100 to 10,000A.
2. The method of claim 1, wherein the method is carried out for a time sufficient to deposit a coating of thickness in the range of .

[Brief explanation of drawings]

The drawing is a schematic cross-sectional view of a carbon-fiber composite made according to the present invention.

Claims (1)

[Claims] 1. A material selected from the group consisting of titanium boride and a mixture of titanium boride and titanium carbide by a vapor phase deposition method in which a mixture of a gaseous titanium compound and a gaseous boron compound is simultaneously reduced on the surface of carbon fibers. a coating of magnesium, lead, zinc,
In a molten metal selected from the group consisting of copper, aluminum, tin, aluminum-silicon alloys and alloys of these metals,
immersing the molten metal until the interstices between the fibers are substantially filled; and the metal body with the coated fibers embedded therein;
A method of forming a fiber-metal composite comprising steps of cooling the metal to a temperature at which it solidifies.