METAL MATRIX COMPOSITE TAPE

Abstract: A process for preparing a continuous metal matrix composite tape. The process includes the steps of: providing a plurality of continuous metal matrix-coated fibers; providing a consolidating apparatus; providing a nonreactive environment around the consolidating means; advancing the plurality of continuous metal matrix-coated fibers into the alignment means to effect longitudinal alignment of the continuous metal matrix-coated fibers; and advancing the continuous metal matrix-coated fibers through the consolidating means to consolidate the continuous metal matrix-coated fibers into a metal matrix composite tape. The consolidating apparatus includes consolidating means for consolidating the continuous-metal coated fibers into a continuous metal matrix composite tape; means for providing a nonreactive environment around the consolidating means; and alignement means to effect longitudinal alignement of the continuous metal matrix-coated fibers.

Description: METAL MATRIX COMPOSITE TAPE Government Rights The U S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract No MDA 972-90-C- 0018 awarded by the Defense Advanced Research Project Agency (DARPA) Background of the Invention Metal matrix composite (MMC) tapes are used in the fabrication of lightweight durable structures, such as parts of airplanes, automobiles, etc Such structures include, for example, fan blades and other rotating components, casings, flat panels, disks, rings, and the like Metal matrix composite tapes are particularly desirable in the production of parts for aircraft engines because of their high specific strengths (i e , high strength to weight ratios) and stiffness at room and elevated temperatures Metal matrix composite tapes typically include fiber reinforcement, such as metal alloy fibers, ceramic fibers, silicon carbide fibers, carbon fibers, or other high strength, high temperature fibers The metal coating (i e , metal matrix) typically includes titanium, aluminum, and alloys thereof, although other matrix metals such as beryllium and copper are known The metal matrix can be applied by physical vapor deposition, solution coating, plasma spraying, and the like The coated fibers are then typically consolidated into a metal matrix composite tape The fabrication of structures from MMC tapes typically involves the lay-up and consolidation of "green preforms " Green preforms are defined as partially dense metal matrix composites with relative packing densities that can vary between 30% and 80% depending on the fabrication technique There are a number of preform fabrication methods, including, for example: the lamination of titanium foils with fiber mats (foil/fiber/foil), the lamination of plasma spray coated fibers; the lamination of titanium powder with fibers (referred to as tape casting), the stacking or winding of metal wires and fibers, and the stacking of metal coated fibers (e-beam coated fibers) In the latter two methods the fibers are held together with organic binders that are removed before consolidation. The green preforms are then cut into the desired shape, enclosed in a tool that is evacuated, and then consolidated at elevated temperature under isostatic pressure (HIP). In such consolidation procedures, the tool design must take into account the volumetric changes associated with the consolidation of the partially dense composite preform. Large volumetric changes increase the complexity of tools designed for complex parts such as disks and rings. Composite lay-up, tooling fabrication, outgassing HIPing and composite removal from the tooling is a complex and costly procedure. A more dense MMC tape (e.g., having a relative packing density of at least about 75%), particularly a continuous (i.e., at least about 6 meters in length) monotape (i.e., a tape having one. layer of longitudinally aligned fibers), would be a more desirable preform to facilitate the fabrication of many components. Such tapes could easily be laid-up and would only require a simple HIP bonding cycle. They would also require simpler tooling due to reduced shrinkage as a result of their higher densities. Such tapes would offer a significant advantage over existing green preforms. Summary of the Invention The present invention provides a process for preparing a continuous metal matrix composite tape comprising: providing a plurality of continuous metal matrix-coated fibers; providing a consolidating apparatus comprising consolidating means and alignment means; providing a nonreactive environment around the consolidating means; advancing the plurality of continuous metal matrix-coated fibers into the alignment means to effect longitudinal alignment of the continuous metal matrix-coated fibers; and advancing the continuous, longitudinally aligned, metal matrix-coated fibers through the consolidating means to consolidate the continuous metal matrix-coated fibers into a metal matrix composite tape. The consolidating apparatus includes consolidating means for consolidating the continuous-metal coated fibers into a continuous metal matrix composite tape; means for providing a nonreactive environment around the consolidating means; and alignment means to effect longitudinal alignment of the continuous metal matrix-coated fibers. A preferred embodiment of the process comprises: providing a plurality of continuous metal matrix-coated fibers; providing a consolidating apparatus comprising an enclosure, supply spools, alignment means, consolidate means, and a collecting spool; providing a nonreactive environment in the enclosure; advancing the plurality of continuous metal matrix-coated fibers from the supply spools into the alignment means to effect longitudinal alignment of the fibers; advancing the continuous, longitudinally aligned, metal matrix-coated fibers through the consolidating means to consolidate the continuous metal matrix-coated fibers into a metal matrix composite tape; and collecting the metal matrix composite tape on the collecting spool. The consolidating apparatus comprises: an enclosure; means for providing a nonreactive environment in the enclosure; supply spools having a plurality of continuous metal matrix-coated fibers thereon; a collecting spool for collecting the continuous metal matrix composite tape; consolidating means within the enclosure positioned between the supply spools and the collecting spool for consolidating the continuous-metal coated fibers into a continuous metal matrix composite tape; and alignment means positioned between the supply spools and the consolidating means to effect longitudinal alignment of the continuous metal matrix-coated fibers. Also provided is a process for preparing a continuous metal matrix composite tape is also provided comprising: providing a plurality of continuous metal matrix-coated fibers; providing a consolidating means; providing a nonreactive environment around the consolidating means; longitudinally aligning the plurality of continuous metal matrix-coated fibers; and advancing the longitudinally aligned continuous metal matrix-coated fibers through the consolidating means to consolidate the continuous metal matrix-coated fibers into a metal matrix composite tape. Also provided is a metal matrix composite tape prepared according to the processes described above. Preferably, a metal matrix composite tape according to the present invention has a length of at least about 6 meters comprising at least one layer of a plurality of continuous, longitudinally aligned, non-touching reinforcing fibers, wherein the tape has a relative packing density of at least about 75%, a longitudinal surface roughness of no greater than about 25 micrometers, and a transverse surface roughness of no greater than about 25 micrometers. The present invention also provides a fiber reinforced metal matrix composite article (preferably, a ring) having a central axis, the article comprising a consolidated metal matrix tape extending as a continuous spiral through a plane normal to the central axis of the composite article. A process for preparing such an article is also provided. The process comprises consolidating a continuous spiral wrap of a regularly spaced array of a metal matrix composite tape around a central core, wherein, prior to being consolidated, the metal matrix composite tape has a length of at least about 6 meters and comprises at least one layer of a plurality of continuous, longitudinally aligned, non-touching reinforcing fibers, and a relative packing density of at least about 75%. Brief Description of the Drawings Figure 1 is a schematic of a consolidating apparatus for use in the process of the present invention to prepare an MMC tape of the present invention. Figure 2 is a schematic of an alignment means (guide tubes) for use in the consolidating apparatus of Figure 1. Figure 2a is a cross-sectional view of the alignment means of Figure 2 taken along line 2a. Figure 3 is a schematic of an alternative embodiment of an alignment means (guiding rods) for use in the consolidating apparatus of Figure 1. Figure 3a is a schematic of a guiding rod of the alignment means of Figure 3. Figure 4 is a schematic of another alternative embodiment of an alignment means (interlocking rolls) for use in the consolidating apparatus of Figure 1. Figure 4a is a side view of the interlocking rolls of Figure 4. Figure 4b is a front view of the interlocking rolls of Figure 4. Figure 5a is a cross-sectional view of metal matrix-coated fibers longitudinally aligned in a plane prior to consolidation into an MMC monotape. Figure 5b is a cross-sectional view of metal matrix-coated fibers longitudinally aligned in a more closely packed configuration than that in Figure 5a prior to consolidation into an MMC monotape. Figure 5c is a cross-sectional view of an MMC monotape of the present invention. Figure 6a is a cross-sectional view of an approximate hexagonal array of three layers of an MMC monotape of the present invention. Figure 6b is a cross-sectional view of a rectangular array of three layers of an MMC monotape of the present invention. Figure 7 is a perspective view of a fiber-reinforced metal matrix composite ring. Figure 7a is a cross-sectional view of the ring of Figure 7 taken along line 7a. Detailed Description The present invention provides a process for preparing a continuous metal matrix composite (MMC) tape, and the MMC tape prepared thereby. The present invention also provides a fiber reinforced metal matrix composite article (preferably, a ring) prepared from consolidated layers of the MMC tape, and process for preparing such an article. The metal matrix composite tape is continuous and includes at least one layer of a plurality of continuous, longitudinally aligned, non-touching reinforcing fibers. Preferably, the metal matrix composite tape is a continuous monotape (i.e., it includes a monolayer of a plurality of continuous, longitudinally aligned, non-touching reinforcing fibers). As used herein, the term "continuous" refers to a tape having a length of at least about 6 meters. Typically, however, the tape can be much longer. Preferably, MMC tape according to the present invention is at least about 20 meters, and more preferably at least about 30 meters. The term "longitudinally aligned " refers to parallel alignment of the fibers along the length of the tape. The term "non-touching" refers to the fact that individual longitudinally aligned reinforcing fibers do not touch due to metal matrix between each of the reinforcing fibers. Although any one reinforcing fiber may have a secondary structure that includes a plurality of touching filaments, as in a yarn or tow, for example, the reinforcing fibers themselves are separated by metal matrix in the primary structure. Also, significantly, continuous MMC tape according to the present invention has a relatively smooth surface (i.e. , small surface roughness). The surface roughness is defined by the average amplitude (h) between surface peaks and valleys. Specifically, the surface roughness (h) is defined as the arithmetic mean of the absolute values of the profile departure from the centerline within a length of evaluation. The surface roughness can be defined in two directions, the transverse direction (i.e., the direction perpendicular to the fiber axis) and the longitudinal direction (i.e. , the direction parallel to the fiber axis). The surface roughness can be measured using a profilometer, such as that available under the trade designation "SURFEST 211 " from Mituyoto, Japan. The surface roughness of the MMC tape of the present invention, whether in the longitudinal (h,) or transverse (h,) direction, is no greater than about 25 micrometers, preferably, no greater than about 15 micrometers, more preferably, no greater than about 10 micrometers, and most preferably, no greater than about 5 micrometers. In contrast, the surface roughness of titanium plasma sprayed tape reinforced with silicon carbide fibers is typically about 45 micrometers, both in the transverse and the longitudinal directions, which can be calculated based on the mean asperity height reported in Elzey et al., Acta Metall. Mater.. 41, 2297-2316 (1993). The relatively small surface roughness of continuous MMC tape according to the present invention is significant because the surface roughness can cause bending and breaking of the reinforcing fibers during consolidation of a plurality of longitudinally aligned metal matrix-coated fibers to form a tape. Bending can occur along the fiber axis when the fiber is deflected between the two surface peaks. Therefore, the smaller the surface roughness, the less the fiber damage. Large surface roughness in the longitudinal direction is a leading cause of fiber damage during consolidation. Typically, and significantly, particularly preferred embodiments of the tape of the present invention have a surface roughness in the transverse direction of no greater than about 5 micrometers and a surface roughness in the longitudinal direction of no greater than about 3 micrometers. Significantly, MMC tape according to the present invention has a relative packing density of at least about 75%, and preferably at least about 85%. In contrast, the relative packing density of titanium plasma sprayed tape reinforced with silicon carbide fibers is typically about 60-70%, as reported (in terms of void volume) in Elzey et al., Acta Metall. Mater.. 4_i, 2297-2316 (1993). The relative packing density is defined as the relative density of several layers of the tape stacked on top of each other. These layers are merely stacked on top of each other without permanent attachment (e.g. , prior to consolidation of the layers of the tape into an article). The relative packing density is therefore a function of the surface roughness. The relative packing density can be measured directly on a single ply (i.e., single layer) of the tape using image analysis of a cross-section of the tape, which is then polished to a mirror finish. A picture of the polished cross- section can then be analyzed with image analysis software, such as NIH Image software, which is software available from the National Institutes of Health, Washington, D.C. An imaginary rectangular frame is first defined to delineate the smallest rectangular boundary enclosing the MMC tape. The total surface area occupied by the tape, and the total surface area of this rectangular enclosure are measured by the image analysis software. The ratio of these two areas defines the relative packing density (i.e., surface area of the tape ÷ surface of the rectangular enclosure). Metal matrix composite tape according to the present invention includes a matrix comprising a metal (which can include a metal alloy or metalloid) and reinforcing fibers. The reinforcing fibers can be monofilaments, yarns (twisted groups of monofilaments), or tows (nontwisted groups of monofilaments). Suitable yarns or tows typically include about 400 to about 7800 individual filaments. The yarns or tows generally have a diameter of about 0.2 millimeter to about 1.5 millimeters. Suitable monofilaments typically have a diameter of about 0.05 millimeter to about 0.25 millimeters. Preferably, the reinforcing fibers are monofilaments to avoid fiber crossover. Suitable reinforcing fibers include any of a wide variety of fibers of known composition. They preferably are relatively high in strength, generally have limited or low ductility compared to the metal matrix, and reinforce the metal matrix to enable articles prepared from MMC tape according to the present invention to withstand severe operating conditions such as high stresses (e.g., 1400 MPa) and elevated temperatures (e.g., 400 °C and above). Examples of high temperature, high strength fibers include boron, silicon carbide, refractory metal fibers, graphite, alumina, and other ceramic fibers. Such fibers can include a protective coating or layer of another material surrounding the core of the reinforcing fibers. Examples of such "coated " fibers include carbon-coated silicon carbide fibers. Preferably, the reinforcing fibers are silicon carbide fibers, boron fibers, sapphire fibers, titanium diboride fibers, alumina fibers, or mixtures thereof, which may or may not be coated with a protective coating material prior to the application of the metal matrix coating. More preferably, the reinforcing fibers are silicon carbide fibers, which are often coated with a thin protective carbon coating. The metal matrix of continuous MMC tape according to the present invention includes a wide variety of metals or metal alloys that can withstand severe operating conditions such as high stresses (e.g. , 1400 MPa) and elevated temperatures (e.g., 400°C and above). Preferably, the metal matrix is a high strength, light weight metal or metal alloy that can sustain the operating environment and oxidation resistance. The metal matrix materials include, for example, titanium, aluminum, nickel, vanadium, molybdenum, tin, chromium, zirconium, tantalum, niobium, iron, silicon, cobalt, and alloys thereof Preferably, the metal matrix is a titanium-based alloy (i.e., an alloy in which titanium is at least half the composition in parts by weight). Examples of suitable titanium-based alloys include titanium/aluminum/vanadium alloys. A preferred alloy is the titanium aluminum/vanadium alloy Ti-6A1-4V (containing 6 wt-% aluminum and 4 wt-% vanadium). The metal matrix is provided as a coating on the fibers, although it can also be provided as wires or ribbons without core fibers, which can be used in combination with the metal matrix-coated fibers. Continuous MMC tape according to the present invention is made by consolidating metal matrix-coated fibers and optionally metal matrix wires, ribbons, or foils. For example, metal matrix-coated fibers and metal matrix wires could be supplied in a layer in alternating fashion to the consolidation apparatus described below to form an MMC tape having a larger volume of metal matrix than if metal matrix-coated fibers were used alone. For the metal matrix-coated fibers, the metal matrix coating is typically of a thickness sufficient to yield a desired level of matrix volume fraction when the metal matrix-coated fibers are consolidated. As is understood in the art, such metal matrix-coated fibers (also referred to as matrix coated fibers) are distinguished from those fibers that have thin barrier layers, for example. Preferably, the metal matrix-coated fibers have a reinforcing fiber and a metal matrix coating thereon in an amount such that the volume fraction of the metal matrix is at least about 20%, and more preferably at least about 30%, based on the total volume of the fibers. That is, although suitable metal matrix-coated fibers may or may not have a thin protective or barrier coating (e.g., carbon), they will always have a coating of metal matrix. Preferably, the reinforcing fibers are coated with a metal matrix using electron beam evaporation coating techniques similar to the techniques described in International Publication No. WO 92/14860 (published September 3, 1992). Such e-beam coated metal matrix-coated fibers have a very uniform metal matrix coating thereon, which makes them particularly suitable for use in preparing an MMC tape having a relatively large relative packing density and a relatively smooth surface. A particularly preferred metal matrix-coated fiber is a silicon carbide reinforcing fiber (preferably, a carbon-coated silicon carbide reinforcing fiber) with a titanium/aluminum/vanadium alloy matrix coating thereon, which is commercially available from the 3M Company, St. Paul, MN as 3M Brand Titanium Matrix Composite metal coated fibers. The carbon-coated silicon carbide reinforcing fibers are commercially available, for example, from Textron Specialty Materials, Lynn, MA, under the trade designation SCS-6 (140 micrometers in diameter), and Amercom, Chatworth, CA, under the trade designation TRIM ARC 1 (127 micrometers in diameter). A plurality of metal matrix-coated fibers (and optional metal matrix wires, ribbons, or foils) are consolidated into an MMC tape according to the present invention by the application of heat and pressure to effect the plastic flow of the metal matrix material such that interstitial spaces are filled with material and adjacent metal matrix-coated fibers are bonded together. International Publication No. WO 92/14860 (published September 3, 1992), discloses such processes of consolidation, none of which are continuous processes, however. For example, it is disclosed that metal matrix-coated fibers can be consolidated by canning a bundle of the fibers, evacuating and sealing the can, and then hot isostatic pressing (HIPing) the canned material under pressure of argon at 150 MPa and a temperature of 925 °C. Alternatively, shaped articles can be formed by consolidating a mass of the metal matrix-coated fibers in a shaped die or between press platens. These are not continuous processes. The present invention provides a continuous process of consolidating the metal matrix-coated fibers into a continuous MMC tape, preferably a continuous MMC monotape. The continuous tape can then be used to make a variety of articles by consolidating multiple layers (e.g., multiple winds or plies) of the tape. These processes take advantage of the plastic flow of the metal matrix material under the application of heat and pressure. They are advantageous because the resultant tapes and articles have substantially no organic binder therein. The process for preparing a continuous metal matrix composite tape according to the present invention involves longitudinally aligning and consolidating a plurality of continuous metal matrix-coated fibers (and optionally metal matrix wires, for example). The consolidation occurs in a nonreactive environment (i.e. , an environment that is not reactive with either the metal matrix material of the reinforcing fiber), under the application of heat and pressure. Referring to Figure 1 , the consolidation process can be carried out using a consolidating apparatus 10, which includes: consolidating means 12 for consolidating the continuous metal matrix-coated fibers 14 into a continuous metal matrix composite tape 16 under the application of heat and pressure; means for providing a nonreactive environment around the consolidating means, which can include, for example, an enclosure 18 that can be evacuated and/or a source of a nonreactive gas 20; and alignment means 22 to effect longitudinal alignment of the continuous metal matrix-coated fibers 14. Preferably, the consolidating means 12 is contained within the enclosure 18. The consolidating apparatus 10 typically further includes supply means 24, such as supply spools, to provide a plurality of continuous metal matrix-coated fibers 14, and collecting means 26, such as a collecting spool, to collect the continuous metal matrix composite tape. The supply means 24 and collecting means 26 may or may not be positioned within the enclosure. Preferably, however, they are within the enclosure 18. Consolidation (i.e., bonding) of the metal matrix-coated fibers is carried out in a nonreactive environment to avoid contamination of the metal matrix material, particularly at high temperatures. A nonreactive environment can include an atmosphere of a nonreactive gas (often referred to as an inert gas) such as argon. Alternatively, the metal matrix-coated fibers can be consolidated under reduced pressure (e.g., as in an evacuated enclosure such as a vacuum- box). Preferably, the nonreactive environment includes less than about 100 ppm oxygen, less than about 1000 ppm water vapor, and low nitrogen levels. More preferably, the nonreactive environment includes less than about 10 ppm oxygen and less than about 10 ppm water vapor. Most preferably, the nonreactive environment includes less than about 1 ppm oxygen, and less than about 10 ppm water vapor. Excessive nitrogen pick-up is usually detected by discoloration of the metal matrix of the tape being formed. Referring to Figure 1, preferably, the enclosure 18 is made of materials with low permeability to oxygen, water vapor, and nitrogen. A suitable enclosure 18, for example, at least for small scale production of continuous MMC tape according to the present invention, is a glove-box such as that commercially available from T-M Vacuum Products Inc., Cinnamison, NJ. Additionally, commercially available oxygen and moisture gettering unit 26, such as that available from VAC, Hawthorne, CA, for example can be used to purify a nonreactive gas such as argon. Also, one or more commercially available sensor(s) 28, such as that available from Panametrics, Waltham, MA., for example, can be used to monitor the oxygen and water vapor content within the enclosure 18. A suitable method of removing the excess nitrogen, which can cause discoloration of the metal matrix-coated tape, involves purging the enclosure 18 with nonreactive gas (e.g., argon). To consolidate the metal matrix-coated fibers to form an MMC tape, heat and pressure are applied for a time sufficient to effect the plastic flow of the metal matrix material such that interstitial spaces are filled with material and adjacent metal matrix-coated fibers are bonded together. This is accomplished through the use of consolidating means, which includes means for applying heat and pressure. This can be accomplished through the use of platens or rolls, preferably rolls, which can be made of ceramic, graphite, metal, or combinations thereof. Preferably, at least two rolls are used and positioned such that the continuous metal matrix-coated fibers are advanced between the rolls under the application of heat and pressure. Referring to Figure 1, which displays a preferred consolidating means 12, there is shown two parallel consolidating rolls (an upper roll 30 and a lower roll 32), each of which are mounted on a water-cooled shaft 34 and 36. The consolidating rolls 30 and 32 can be of a variety of sizes and made of a variety of materials. The main requirements for roll selection are good strength, high modulus, and slow kinetics of reaction with the metal matrix material. The consolidating rolls 30 and 32 should have sufficient strength to resist large indentation stresses during operation, such as that resulting from the metal matrix-coated fibers, which can be about 10-275 MPa. Preferably, a desirable roll compressive strength is at least about 100 MPa. They also should have enough stiffness to resist elastic deflection under the indentation loads needed to deform the metal matrix-coated fibers. Preferably, a desirable stiffness is at least about 10 GPa, and more preferably, at least about 30 GPa. The consolidating rolls 30 and 32 should also not bond to the metal matrix material under the conditions used in the consolidation process. Although the rolls 30 and 32 can be made of a wide variety of materials (e.g., graphite, metals, ceramics) as mentioned above, for obtaining high packing densities (e.g., greater than about 95%) graphite generally has too low a stiffness and can show excessive deflection under indentation loads. This can result in wavy tapes. Certain metals are also not desirable for certain applications. For example, molybdenum sticks to titanium within a few seconds at temperatures at least about 750°C. Silicon nitride, however, has desirable strength, stiffness, and slow kinetics of adhesion, particularly with respect to titanium-based alloys, and is therefore suitable for the roll bonding of titanium- based metal matrix-coated silicon carbide fibers. The consolidating rolls 30 and 32 are mounted on water-cooled shafts 34 and 36 driven by an electric motor 38 and, preferably, a reducer 40 to enhance torque at low rotational speeds. The rotational speed of the consolidating rolls 30 and 32 can be varied, preferably up to about 3 revolutions per minute (φm). Both rolls rotate at the same rate, however, the upper roll 30 can be held stationery with respect to vertical movement while the lower roll 32 is allowed to translate vertically. This can be accomplished by applying pressure to the lower shaft 36 using one or more pneumatic cylinder(s) 42, of the type commercially available from Brass Co, Eden Prairie, MN, for example, which are pressurized with gas (e.g., argon). Because shafts 34 and 36 are driven by motor 38, which is typically located outside enclosure 18, seals, such as ferrofluidic seals, can be used to prevent leaks. Shafts 34 and 36 are preferably water-cooled to keep their temperature lower than about 30°C during consolidation. The consolidating rolls 30 and 32 can be heated by a variety of means. A preferred means is shown in Figure 1 , which includes four banks of quartz heaters 43, 44, 45, and 46 surrounding the consolidating rolls 30 and 32. Preferably, the consolidating rolls 30 and 32 can be heated up to temperatures of about 1100°C using such heaters. Examples of suitable such heaters are conventional quartz strip-heaters such as those available from Research Inc, Minneapolis, MN. Generally, the conditions (pressure, temperature, time) used in the continuous process of the present invention for consolidating the metal matrix-coated fibers are much less severe than the conditions used in conventional consolidation techniques for titanium composites (e.g., HTPing and hot-pressing). While conventional HIPing of fiber reinforced titanium/aluminum/vanadium composites typically uses a cycle of about 900°C at about 100 MPa pressure for two hours, the time at temperature and pressure with the continuous process of the present invention is much shorter. For example, fiber reinforced titanium/aluminum/vanadium composite tapes can be made using the continuous process of the present invention by exposing the metal matrix-coated fibers to a temperature of about 650°C to about 1050°C, and applied forces varying from about 10 kg to 40 kg per fiber, for less than about 30 seconds, and often for less than about 15 seconds, and more often for less than about 5 seconds. Higher temperatures and pressures can be used, however, in the continuous process of the present invention if so desired. Higher temperatures are preferred to get a fully dense tape, to avoid shearing off of any thin protective coating (e.g., carbon coating) from the core fiber (e.g., silicon carbide fiber), and to provide a strong diffusion bond between the coated fibers. Temperatures as high as about 1050°C can be used, for example. The upper temperature limit is typically governed by adhesion of the metal matrix material to the consolidating means (e.g., rolls 30 and 32, Figure 1) at the point of contact (50, Figure 1). Generally, for titanium-based alloys in contact with graphite walls, the temperature at the contact point (50, Figure 1) is about 950-1000°C. Preferably, the load applied by the consolidating means to the continuous metal matrix-coated fibers is about 10 Kg to about 1500 Kg. More preferably, the load applied by the consolidating means to the continuous metal matrix-coated fibers is about 25 Kg per fiber. The force applied, however, depends on a variety of factors, such as the elastic, plastic, and creep indentation of the metal matrix-coated fibers and the consolidating means (e.g., consolidating rolls 30 and 32) and the number of metal matrix-coated fibers. For example, with a pair of silicon nitride consolidating rolls consolidating ten metal matrix-coated fibers, a force of about 200 Kg to about 350 Kg is necessary to get a fully dense monotape at a temperature of about 800°C at the contact point and at a linear velocity of about 5 centimeters/minute. If the temperature is increased to 840°C, the force can be dropped to about 150 Kg for the same results. In the continuous process of the present invention, the time under pressure and temperature is a function of the linear speed and the contact surface. Using the continuous process of the present invention, at a typical linear speed of 5 centimeters/ minute, the total time in the hot zone (e.g., about 8 centimeters on either side of the point of contact) is about 3 minutes. The time under pressure at the contact point (30, Figure 1) is considerably lower (generally, only 2-3 seconds). Typically, an increase in linear speed is compensated for by higher pressure and/or temperature to produce a more fully dense tape. The position of the coated fibers before consolidation is important for controlling the final geometry and the microstructure of the MMC tape of the present invention. As shown in Figure 1, the fiber transport is preferably a continuous reel to reel operation using supply spools 24 and collecting spool 26, with transport of the fibers under tension (typically about 45-140 grams on each fiber). Positioned between these spools is alignment means 22, which is used to effect longitudinal alignment (i.e. , parallel positioning in a side-by-side fashion which may or may not be aligned in one plane defined by the central axes of the fibers) of the continuous metal matrix-coated fibers. There are a number of embodiments of the alignment means 22. For example, the alignment means 22 can be in the form of a comb, grooved guiding rods, interlocking grooved rolls, a plurality of guide tubes, or various combinations thereof. One alignment means utilizes a series of flexible, small diameter tubes to guide the metal matrix-coated fibers from the supply means into the consolidation means in an aligned configuration. Referring to Figure 2, metal matrix-coated fibers 14 leave supply means 24 and pass through guide tubes 60, which deliver the metal matrix-coated fibers 14 between the consolidating rolls 30 and 32 in a longitudinally aligned configuration. Close packing of the metal matrix-coated fibers 14 as they enter consolidating rolls 30 and 32 is achieved by arranging the ends 62 of the guide tubes 60 in a stacked arrangement, as illustrated in Figure 2a. By arranging the guide tubes 60 in this manner, a slight overlap of the metal matrix-coated fibers 14 can be achieved as they pass between consolidating rolls 30 and 32, thereby ensuring good interfiber bonding. This type of overlap is shown in Figure 5b. Suitable materials for the guide tubes include stainless steel, INCONEL, molybdenm etc. An alternative embodiment of the alignment means is shown in Figure 3. This embodiment includes a series of guiding rods 70 positioned between the supply spools 24 and the consolidating rolls 30 and 32 for aligning metal matrix -coated fibers 14. Optionally, one or more guiding rods 70 can also be positioned after the consolidating rolls 30 and 32 to help guide the fibers 14 before the load is applied on the rolls to form the MMC tape 16. Referring to Figure 3a, each guiding rod 70 includes grooves 72 that are used to push the metal matrix-coated fibers 14 close together and in contact with each other. Grooved rods can be made of a variety of materials, such as stainless steel, molybdenum, or silicon nitride, for example. Preferably, they are made of molybdenum or silicon nitride. Using the embodiment shown in Figure 3, the metal matrix-coated fibers are initially touching and co-planar (see Figure 5a) . Another alignment means embodiment used to provide the initial fiber overlap shown in Figure 5b is shown in Figure 4. In this embodiment there are a set of at least two interlocking grooved rolls 80 and 82 positioned between the supply spools 24 and the consolidating rolls 30 and 32 for aligning the metal matrix-coated fibers 14 with the desired overlap to form the MMC tape 16. Figure 4a is a side view of the interlocking rolls 80 and 82. Figure 4b is a front view of Figure 4b showing interlocking grooved rolls 80 and 82. The grooved interlocking rolls can be made from stainless steel, INCONEL, molybdenum, etc. Preferably, the metal matrix-coated fibers are aligned in an overlapping manner as shown in Figure 5b. This provides a more dense MMC tape than if the fibers are all in one plane as shown in Figure 5a. Whether the overlapping arrangement of fibers of Figure 5b or the planar arrangement of fibers of Figure 5a is used, they both can provide a MMC tape, the cross-section of which is shown in Figure 5c. The arrangement of Figure 5b is generally preferred because it can provide a more highly dense MMC tape. Continuous MMC tape according to the present invention can be used to prepare a variety of articles. Fiber reinforced metal matrix composite articles are typically fabricated by stacking multiple layers (i.e., wraps or plies) of an MMC tape. The individual layers can be stacked directly on top of each other resulting in a rectangular array as shown in Figure 6b. Alternatively, the individual layers can be precisely offset to produce a nearly perfect hexagonal fiber array as shown in Figure 6a. The tape is particularly suitable for the preparation of a fiber reinforced metal matrix composite article having a central axis. The article has a consolidated metal matrix tape extending as a continuous spiral through a plane normal to the central axis of the composite article. This can be in the overall shape of a circular or oval ring or cylinder, as well as a square or rectangular ring or cylinder. Preferably, the article is in the form of a circular ring or cylinder. Referring specifically to Figure 7, there is shown a fiber reinforced metal matrix composite ring prepared from a dense MMC tape of the present invention. The high packing density and low surface roughness of the MMC tape construction, which results in low shrinkage on consolidation, allows the composite fiber reinforced metal matrix composite articles, such as ring 90, to be readily prepared by spirally wrapping a length of the tape around a central core or axis and subsequently consolidating the construction by a conventional HIPing process. A cross-section of the ring 90 shown in Figure 7a illustrates the regular arrangement of reinforcing fibers achieved from this process. Further, if a plane is drawn perpendicular to the axis of the ring, one can follow a single reinforcing fiber 92 in a plane spirally outward from the inside diameter of the ring to the outside diameter. Thus, a fiber reinforced metal matrix composite article (e.g., ring 90) can be prepared by consolidating a continuous spiral wrap of a regularly spaced array of a metal matrix composite tape of the present invention around a central core. The spiral wrap is typically placed in a hot isostatic press, as is well known in the art, evacuated and encapsulated. A typical method for encapsulating the spiral wrap of MMC tape in a cavity is to electron-beam weld a cover or foil in a vacuum chamber. This cavity can then be evacuated. Subsequently, typical HIPing conditions, which are generally known to one of skill in the art, are applied to consolidate the continuous spiral wrap of MMC tape. For example, consolidation of a titanium matrix composite tape can be carried out at 900°C and 100 MPa pressure for two hours. Continuous MMC tape according to the present invention can be used with non-reinforced layers of metal or metal alloys (e.g., metal foils) to produce fiber-reinforced metal matrix composite articles. For example, one or more layers of an MMC tape can be consolidated with one or more layers of a metal foil using the consolidation apparatus of Figure 1. This would provide an MMC tape having additional matrix material and preferably multiple layers of reinforcing fibers. Also, MMC tape according to the present invention can be bonded side-by-side by advancing a plurality of MMC tapes positioned side-by-side in the consolidation apparatus of Figure 1. Alternatively, the bonding of the MMC tapes can be improved by using wires or metal ribbons between adjacent MMC tapes. This results in a wider MMC tape. The following examples are offered to further illustrate the various specific and preferred embodiments and techniques. It should be understood, however, that many variations and modifications may be made while remaining within the scope of the present invention. TEST PROCEDURES Relative Packing Density Relative packing density was determined by image analysis. The dense monotape sample was cross-sectioned, polished to a mirror finish, photographed, and image analysis performed on the photograph using NTH Image software, available from the National Institutes of Health, Washington D C. A rectangular frame delineating the smallest rectangular boundary to fully enclose the cross-section image of the monotape was established as a base for the analysis. The actual surface area occupied by the monotape cross-section was subsequently determined via the image analysis software and the relative packing density (PD re - ) of the monotape sample determined by the ratio: PD ^ A act / A fhn XlOO where PD „• is the relative packing density; A lct is the actual surface area of the monotape cross-section, and A f i m is the area enclosed by the smallest rectangular boundary f lly enclosing the cross-section image of the monotape. Surface Roughness A profilometer (available under the trade designation "SURFEST 21" from Mituyoto, Japan) was used to determine the surface roughness of a monotape sample in both the longitudinal (hi, down-web or parallel to the fiber axis) and transverse (h t , cross-web or peφendicular to the fiber axis) directions. Surface roughness, which is reported in μm, is the average amplitude between the surface peaks and valleys. More specifically, surface roughness is the arithmetic mean of the absolute values of the profile departure from the centerline within the evaluation length. EXAMPLES Consolidating Apparatus An inert consolidating environment was provided by a glove-box enclosure inerted with argon containing less than about 1 ppm oxygen, 10 ppm water vapor and low nitrogen levels. The inert environment was obtained by purging the chamber with approximately 10 times its volume of ultra high purity argon (containing less than 1 ppm oxygen and water vapor) at a rate of 0.56 cm min. The purge was shut off and the chamber environment purified further by the use of commercially available oxygen and water vapor getters (available from VAC, Hawthorne, CA), which, after approximately 48 hours of circulation, reduced the oxygen and water vapor levels to approximately 0.6 and 10 ppm, respectively, or less. Oxygen and water vapor levels are subsequently monitored by commercially available sensors, such as those available from Panametrics, Waltham, MA. Oxygen, nitrogen, and water vapor levels were locally "gettered" by circulating a piece of titanium foil 152.4 cm x 2.5 cm x 0.013 cm through the consolidation rolls at elevated temperatures (> 600°C) until there were no signs of discoloration. Two silicon nitride rolls, each 10.2 cm in diameter and 12.7 cm in length, mounted on water cooled shafts, served as the consolidation rolls. Alternatively, graphite rolls could be substituted for the silicone nitride rolls. The rolls were mounted in a frame which maintained the upper roll in a fixed position but allowed the lower roll to vertically translate by means of two argon pressurized pneumatic cylinders. Pressurization of the cylinders allowed forces of up to approximately 10-150 kg to be applied to the fibers as they passed between the rolls. The shafts were driven by an electric motor and reducer, positioned outside of the chamber, which produced a maximum torque of 540 Nm at 2 φm. Potential leaks to the outside environment were minimized by driving the shafts through ferrofluidic seals. During the consolidation operation, the rolls were heated to temperature as high as about 1,100°C by four banks (2 on each roll) of quartz strip heaters. The shaft rolls were maintained at approximately 30°C during consolidation operations. Fiber Alignment Apparatus Guide Tubes: A series of flexible stainless steel tubes, 0.04 cm I.D., 0.051 cm O.D., (available from Microguide, Corp., Midway, MA) were used to guide the metal coated fibers from the fiber supply spools to the consolidation apparatus. The ends of the tubes adjacent to the fiber supply spools were arranged in a substantially horizontal, spaced apart arrangement to facilitate feeding the fibers from the supply spools into the guide tubes. The ends of the guide tubes adjacent the consolidating apparatus were arranged in groups of three vertically staggered tubes, the tubes in each group being positioned at 0.076 cm center to center vertically and 0.0076 cm center to center horizontally. The horizontal positioning of the lower tube of one group relative to the top tube of the adjacent group maintained a similar horizontal spacing (see Figure 2). Grooved Rod Guides: Three molybdenum rods 0.64 cm in diameter and having a 1.27 cm diameter grove, approximately 0.23 cm deep were positioned approximately 5.1 cm apart, approximately 5.1 cm in front of the rolls of the consolidation apparatus in an alternating fashion (see Fig. 3). A fourth grooved rod was positioned approximately 2.54 cm behind the rolls of the consolidating apparatus. Metal coated fibers were positioned in the groves and maintained at a tension of approximately 45-140 g/fiber to insure parallel alignment without crossover. Interlocking Rolls: Two 2.54 cm diameter stainless steel interlocking grooved rolls, prepared such that one roll had a series of 0.023 cm wide circumferencial grooves and land areas which interlocked with a second roll which had a series of 0.018 cm wide land areas and 0.023 cm wide grooves, were positioned immediately preceding the grooved rods described above. The interlocking rolls aligned the fibers and concurrently positioned them with a slight overlap (Fig. 5b). Example 1 Titanium alloy coated monofilament silicon carbide fibers available were prepared by the electron beam vapor deposition of a Ti-6A1-4V titanium/aluminum(6%)/vanadium(4%) alloy on a silicon carbide fiber (obtained from Textron Specialty Materials, Lynn, MA under the designation SCS-6) using a procedure similar to that described in World Patent WO 92/14860 (Ward-Close, Charles M.). The coated fibers contained 35 vol% fiber. Ten supply spools of these titanium alloy coated fibers were introduced into the consolidating apparatus described above, which was equipped with the interlocking grooved roll alignment apparatus. The fibers were threaded through the interlocking grooved rolls and the atmosphere in the apparatus "inerted" using the procedures described above. Subsequent to local "getting" of oxygen, nitrogen, and water vapor by passing a titanium foil through the heated consolidation rolls, the fibers were passed between the consolidating rolls at a linear velocity of 5.1 cm/min, a temperature of 875°C, and an applied force of 250 kg to produce a 0.254 cm wide smooth monotape construction with h i = h t < 3 μm and a relative packing density of 99%. Example 2 A dense monotape construction was prepared using a procedure similar to that described in Example 1 except that the consolidating rolls were made of graphite, the fibers were collimated using grooved rod guiding, the consolidation temperature was 950°C, and the applied force was 200 kg. The resulting monotape construction had a h t < 15μm, a h i < 3μm, and a packing density of 85%. Example 3 Titanium alloy coated monofilament silicon carbide fibers were prepared by the electron beam vapor deposition of a Ti-6A1-4V titanium/aluminum(6%)/vanadium(4%) alloy on silicon carbide fiber (available from Amercom Coφoration, Chatsworth, CA under the designation TRTMARC 1) using a procedure similar to that described in World Patent WO 92/14860 (Ward- Close, Charles M ). The coated fibers contained 35 vol% fiber. A dense monotape construction was prepared from the titanium alloy coated fibers using a procedure similar to that described in Example 2, except that 20 fibers were collimated using guide tubes and the applied force was 350 kg. The resulting monotape construction had a h i < 7 μm, a h i < 3 μm, and a packing density of 95%. Example 4 Titanium alloy coated monofilament silicon carbide fibers were prepared as described in Example 3 except that the fibers contained 30 vol% fiber. A dense monotape construction was prepared from these fibers as described in Example 3 to produce a monotape which had a h t < 7 μm, a h i < 3 μm, and a packing density of 95%. Example 5 An aluminum coated silicon carbide fiber tow was prepared by the electron beam vapor deposition of aluminum on a silicon carbide fiber tow (available from the 3M Company, St. Paul, MN under the trade designation "NEXTEL 610 CERAMIC FIBERS") using a procedure similar to that described in World Patent WO 92/14860 (Ward-Close, Charles M ) The thus coated fibers were approximately 0.1 mm in diameter and contained 40 vol% fiber tow. A multiplicity of the thus coated fibers were clamped in a side-by-side arrangement in a rigid metal frame, and the fibers placed between the open rolls of the consolidating apparatus, the rolls closed on the fibers, the consolidation apparatus closed and inerted. A dense monotape construction was subsequently prepared by consolidation of the metal coated fibers under the consolidation conditions similar to those described in Example 2, except that the temperature was 540°C and the applied force was 250 kg The resulting monotape construction had a h t < 10 μm, a h i < 5 μm, and a packing density of 95% Example 6 A titanium composite ring was prepared by winding approximately 6 meters of the dense monotape of Example 1 on a 12 7 cm diameter titanium alloy (Ti-6A1-4V) mandrel having a 0.25 cm wide by 0 25 cm deep peripheral groove A titanium alloy cover was placed over the mandrel and wound tape, and the cover and mandrel seam welded by electron beam welding in an vacuum environment The resulting assembly was consolidated in a hot isostatic press (available from Industrial Materials Technology, Andover, MA) at 900°C for 2 hours and 105 MPa pressure The consolidated titanium matrix composite ring was machined-out to 12 45 cm internal diameter, 13 6 cm outside diameter, and 0 0525 cm thickness All patents, patent documents, and publications cited herein are incoφorated by reference as if individually incoφorated The foregoing detailed description has been given for clarity of understanding only No unnecessary limitations are to be understood therefrom The invention is not limited to the exact details shown and described, for variations obvious to one skilled in the art will be included within the invention defined by the claims

Claims: WHAT IS CLAIMED IS: 1. A process for preparing a continuous metal matrix composite tape comprising: (a) providing a plurality of continuous metal matrix-coated fibers; (b) providing a consolidating apparatus comprising: (i) consolidating means for consolidating the continuous-metal coated fibers into a continuous metal matrix composite tape; (ii) means for providing a nonreactive environment around the consolidating means; and (iii) alignment means to effect longitudinal alignment of the continuous metal matrix-coated fibers; (c) providing a nonreactive environment around the consolidating means; (d) advancing the plurality of continuous metal matrix-coated fibers into the alignment means to effect longitudinal alignment of the continuous metal matrix-coated fibers; and (e) advancing the continuous, longitudinally aligned, metal matrix- coated fibers through the consolidating means to consolidate the continuous metal matrix-coated fibers into a metal matrix composite tape. 2. The process of claim 1 wherein the metal matrix composite tape comprises a monolayer of a plurality of longitudinally aligned fibers contained within a metal matrix. 3. The process of claim 1 wherein the alignment means is selected from the group consisting of a comb, grooved guiding rods, interlocking grooved rolls, a plurality of guide tubes, and combinations thereof. 4. The process of claim 1 wherein: (a) the consolidating apparatus further comprises supply means for the continuous metal matrix-coated fibers and collecting means for the metal matrix composite tape; (b) advancing the continuous metal matrix-coated fibers from the supply means to the alignment means; and (c) collecting the metal matrix composite tape on the collecting means upon exiting the consolidating means. 5. The process of claim 1 wherein the consolidating means comprises means for applying heat and pressure. 6. The process of claim 5 wherein the consolidating means comprises rolls positioned such that the continuous metal matrix-coated fibers are advanced between the rolls under the application of heat and pressure. 7. The process of claim 6 wherein the rolls are made of ceramic, graphite, metal, or combinations thereof. 8. The process of claim 6 wherein the rolls are heated to a temperature of about 650°C to about 1050°C. 9. The process of claim 8 wherein the rolls apply about 10 Kg to about 1500 Kg pressure to the continuous metal matrix-coated fibers. 10. The process of claim 1 wherein the continuous metal matrix-coated fibers comprise reinforcing fibers having a metal matrix coating thereon, wherein the reinforcing fibers are each monofilaments. 11. The process of claim 1 wherein the metal matrix-coated fibers comprise reinforcing fibers selected from the group consisting of silicon carbide fibers, boron fibers, sapphire fibers, titanium diboride fibers, alumina fibers, and mixtures thereof. 12. The process of claim 1 wherein the metal matrix-coated fibers comprise reinforcing fibers coated with a metal selected from the group consisting of titanium, aluminum, nickel, vanadium, molybdenum, tin, chromium, zirconium, tantalum, niobium, iron, silicon, cobalt, and alloys thereof. 13. The process of claim 1 wherein the consolidating apparatus further includes an enclosure containing the consolidating means. 14. The process of claim 13 wherein the step of providing a nonreactive environment comprises evacuating the enclosure. 15. The process of claim 1 wherein the environment comprises less than about 100 ppm oxygen and less than about 1000 ppm water vapor. 16. The process of claim 1 further including a step of providing metal matrix wires, ribbons, or foils in combination with the metal matrix-coated fibers. 17. A process for preparing a continuous metal matrix composite tape comprising: (a) providing a plurality of continuous metal matrix-coated fibers; (b) providing a consolidating apparatus comprising: (i) an enclosure; (ii) means for providing a nonreactive environment in the enclosure; (iii) supply spools having a plurality of continuous metal matrix- coated fibers thereon; (iv) a collecting spool for collecting the continuous metal matrix composite tape; (v) consolidating means within the enclosure positioned between the supply spools and the collecting spool for consolidating the continuous-metal coated fibers into a continuous metal matrix composite tape; and (vi) alignment means positioned between the supply spools and the consolidating means to effect longitudinal alignment of the continuous metal matrix-coated fibers; (c) providing a nonreactive environment in the enclosure; (d) advancing the plurality of continuous metal matrix-coated fibers from the supply spools into the alignment means to effect longitudinal alignment of the fibers; (e) advancing the continuous, longitudinally aligned, metal matrix- coated fibers through the consolidating means to consolidate the continuous metal matrix-coated fibers into a metal matrix composite tape; and (f) collecting the metal matrix composite tape on the collecting spool. 18. The process of claim 17 wherein the supply spools and the collecting spool are located within the enclosure. 19. The process of claim 17 wherein the metal matrix-coated fibers comprise silicon carbide fibers coated with a metal selected from the group consisting of titanium, aluminum, nickel, vanadium, molybdenum, tin, chromium, zirconium, tantalum, niobium, iron, silicon, cobalt, and alloys thereof. 20. A metal matrix composite tape prepared according to the process of claim 1. 21. A metal matrix composite tape prepared according to the process of claim 17. 22. A metal matrix composite tape having a length of at least about 6 meters comprising at least one layer of a plurality of continuous, longitudinally aligned, non-touching reinforcing fibers, wherein the tape has a relative packing density of at least about 75%, a longitudinal surface roughness of no greater than about 25 micrometers, and a transverse surface roughness of no greater than about 25 micrometers. 23. The metal matrix composite tape of claim 22 wherein the relative packing density is at least about 85%. 24. The metal matrix composite tape of claim 22 further having a longitudinal surface roughness of no greater than about 15 micrometers and a transverse surface roughness of no greater than about 15 micrometers. 25. The metal matrix composite tape of claim 22 wherein the reinforcing fibers are each monofilaments. 26. The metal matrix composite tape of claim 22 wherein the reinforcing fibers are selected from the group consisting of silicon carbide fibers, boron fibers, titanium diboride fibers, alumina fibers, and mixtures thereof 27. The metal matrix composite tape of claim 22 wherein the metal matrix comprises titanium, aluminum, nickel, vanadium, molybdenum, tin, chromium, zirconium, tantalum, niobium, iron, silicon, cobalt, or alloys thereof. 28. The metal matrix composite tape of claim 22 wherein the fibers are silicon carbide fibers and the metal matrix comprises a titanium aluminum/vanadium alloy. 29. The metal matrix composite tape of claim 22 comprising a monolayer of a plurality of continuous, longitudinally aligned, non-touching reinforcing fibers. 30. The metal matrix composite tape of claim 22 having substantially no organic binder therein. 31. The metal matrix composite tape of claim 22 prepared from a plurality of continuous metal matrix-coated fibers. 32. The metal matrix composite tape of claim 31 prepared from a plurality of e- beam coated continuous metal matrix-coated fibers. 33. A process for preparing a fiber reinforced metal matrix composite article comprising consolidating a continuous spiral wrap of a regularly spaced array of a metal matrix composite tape around a central core, wherein, prior to being consolidated, the metal matrix composite tape has a length of at least about 6 meters and comprises at least one layer of a plurality of continuous, longitudinally aligned, non-touching reinforcing fibers and a relative packing density of at least about 75%. 34. The process of claim 33 wherein, prior to being consolidated, the tape has a relative packing density of at least about 85%. 35. The process of claim 33 wherein, prior to being consolidated, the tape has a longitudinal surface roughness of no greater than about 25 micrometers, and a transverse surface roughness of no greater than about 25 micrometers. 36. The process of claim 35 wherein the fibers are silicon carbide fibers and the metal matrix comprises a titanium/aluminum/vanadium alloy. 37. The process of claim 35 wherein the metal matrix composite tape comprises a monolayer of a plurality of continuous, longitudinally aligned, non-touching reinforcing fibers. 38. The process of claim 33 wherein the fiber reinforced metal matrix composite article is in the form of a circular ring or cylinder. 39. A fiber reinforced metal matrix composite article having a central axis, the article comprising a consolidated metal matrix tape extending as a continuous spiral through a plane normal to the central axis of the composite article. 40. The fiber reinforced metal matrix composite article of claim 39 in the form of a circular ring or cylinder. 41. The fiber reinforced metal matrix composite article of claim 39 wherein prior to being consolidated into the article, the metal matrix composite tape has a length of at least about 6 meters comprising at least one layer of continuous, longitudinally aligned, non-touching fibers, and a relative packing density of at least about 75%. 42. The fiber reinforced metal matrix composite article of claim 39 wherein the reinforcing fibers are selected from the group consisting of silicon carbide fibers, boron fibers, titanium diboride fibers, alumina fibers, and mixtures thereof. 43. The fiber reinforced metal matrix composite article of claim 39 wherein the metal matrix comprises a metal selected from the group consisting of titanium, aluminum, nickel, vanadium, molybdenum, tin, chromium, zirconium, tantalum, niobium, iron, silicon, cobalt, and alloys thereof. 44. The fiber reinforced metal matrix composite article of claim 43 wherein the fibers are silicon carbide fibers and the metal matrix comprises a titanium/aluminum/vanadium alloy. 45. A process for preparing a continuous metal matrix composite tape comprising: (a) providing a plurality of continuous metal matrix-coated fibers; (b) providing a consolidating means; (c) providing a nonreactive environment around the consolidating means; (d) longitudinally aligning the plurality of continuous metal matrix- coated fibers; and (e) advancing the longitudinally aligned continuous metal matrix-coated fibers through the consolidating means to consolidate the continuous metal matrix-coated fibers into a metal matrix composite tape. 46. A metal matrix composite tape prepared according to the process of claim 45. 47. A process for preparing a continuous metal matrix composite tape comprising: (a) providing a plurality of continuous metal matrix-coated fibers; (b) providing a consolidating apparatus capable of consolidating the continuous metal-matrix coated fibers into a continuous metal matrix composite tape in a nonreactive environment, and aligning the continuous metal matrix-coated fibers to effect longitudinal alignment of the fibers; and (c) aligning the plurality of continuous metal matrix-coated fibers to effect longitudinal alignment of the fibers, and consolidating the continuous, longitudinally aligned, metal matrix-coated fibers into a metal matrix composite tape. 48. The process of claim 47 wherein fibers in the metal matrix composite tape are longitudinally arranged in a monolayer. 49. The process of claim 47 wherein the step of aligning is carried out through the use of a comb, grooved guiding rods, interlocking grooved rolls, a plurality of guide tubes, or combinations thereof. 50. The process of claim 47 wherein the consolidating apparatus further comprises supply spools for supplying the continuous metal matrix-coated fibers and collecting spools for collecting the metal matrix composite tape, and the process further comprises: (a) advancing the continuous metal matrix-coated fibers from the supply spools for alignment; and (b) collecting the metal matrix composite tape on the collecting spools upon consolidation. 51. The process of claim 47 wherein the consolidating step is carried out by applying heat and pressure. 52. The process of claim 51 wherein the consolidating step is earned out through the use of rolls positioned such that that continuous metal matrix-coated fibers are advanced between the rolls under the application of heat and pressure. 53. The process of claim 52 wherein the rolls are made of ceramic, graphite, metal, or combinations thereof. 54. The process of claim 52 wherein the rolls are heated to a temperature of about 650°C to about 1050°C. 55. The process of claim 54 wherein the rolls apply about 10 Kg to about 1500 Kg pressure to the continuous metal matrix-coated fibers. 56. The process of claim 47 wherein the continuous metal matrix-coated fibers comprise reinforcing fibers having a metal matrix coating thereon, wherein the reinforcing fibers are each monofilaments. 57. The process of claim 47 wherein the metal matrix-coated fibers comprise reinforcing fibers selected from the group consisting of silicon carbide fibers, boron fibers, titanium diboride fibers, alumina fibers, and mixtures thereof. 58. The process of claim 47 wherein the metal matrix-coated fibers comprise reinforcing fibers coated with a metal selected from the group consisting of titanium, aluminum, nickel, vanadium, molybdenum, tin, chromium, zirconium, tantalum, niobium, iron, silicon, cobalt, and alloys thereof. 59. The process of claim 47 wherein the consolidating apparatus further includes an enclosure for containing the nonreactive environment. 60. The process of claim 59 wherein the step of providing a nonreactive environment comprises evacuating the enclosure. 61. The process of claim 47 wherein the environment comprises less than about 100 ppm oxygen and less than about 1000 ppm water vapor. 62. The process of claim 47 further including a step of providing metal matrix wires, ribbons, or foils in combination with the metal matrix-coated fibers. 63. A process for preparing a continuous metal matrix composite tape comprising: (a) providing a plurality of continuous metal matrix-coated fibers; (b) providing consolidating rolls; (c) providing a nonreactive environment around the consolidating rolls; (d) longitudinally aligning the plurality of continuous metal matrix- coated fibers; and (e) advancing the longitudinally aligned continuous metal matrix-coated fibers through the consolidating rolls to consolidate the continuous metal matrix-coated fibers into a metal matrix composite tape. 64. A metal matrix composite tape prepared according to the process of claim 47. 65. A metal matrix composite tape prepared according to the process of claim 63. 66. The metal matrix composite tape of claim 31 prepared from metal matrix wires, ribbons, or foils in combination with the metal matrix-coated fibers. 67. A fiber reinforced metal matrix composite article comprising one or more layers of consolidated metal matrix tape and one or more layers of consolidated non-reinforced metal. 68. The fiber reinforced metal matrix composite article of claim 67 wherein the non-reinforced metal is the same metal as that in the metal matrix tape. 69. A fiber reinforced metal matrix composite article comprising one or more segments of consolidated metal matrix tape and one or more segments of consolidated non-reinforced metal wires or ribbons adjacent the segments of tape and in the plane defined by the tape. 70. The fiber reinforced metal matrix composite article of claim 69 wherein the non-reinforced metal in the wires or ribbons is the same metal as that in the metal matrix tape. 71. A process for preparing a continuous metal matrix composite tape comprising: (a) providing a plurality of continuous metal matrix-coated fibers; (b) providing a consolidating apparatus comprising: (i) an enclosure for containing a nonreactive environment in the enclosure; (ii) supply spools having a plurality of continuous metal matrix- coated fibers thereon; (iii) a collecting spool for collecting the continuous metal matrix composite tape; (iv) consolidating rolls within the enclosure positioned between the supply spools and the collecting spool for consolidating the continuous-metal coated fibers into a continuous metal matrix composite tape; and (v) an alignment system positioned between the supply spools and the consolidating rolls to effect longitudinal alignment of the continuous metal matrix-coated fibers; wherein the alignment system comprises a comb, grooved guiding rods, interlocking grooved rolls, a plurality of guide tubes, or combinations thereof; (c) providing a nonreactive environment in the enclosure; (d) advancing the plurality of continuous metal matrix-coated fibers from the supply spools into the alignment system to effect longitudinal alignment of the fibers; (e) advancing the continuous, longitudinally aligned, metal matrix- coated fibers through the consolidating rolls to consolidate the continuous metal matrix-coated fibers into a metal matrix composite tape; and (f) collecting the metal matrix composite tape on the collecting spool.

Inventors: DEVE HERVE E, GABEL MARK R, DEVE, HERVE, E., GABEL, MARK, R.
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1997
Main classification: C22C1
IPC codes: C22C47, C22C49, D06M11