JP2007291432A - Metal matrix composite material, and metal matrix composite structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon fiber reinforced metal matrix composite material excellent in thermal conductivity which can be tightly joined to its peripheral region and in which pitch-based carbon fibers, carbon nanotubes, etc., are used and also to provide a metal matrix composite structure constituted by tightly joining the metal matrix composite material to its peripheral region. <P>SOLUTION: In the metal matrix composite material, at least a part of surface is tightly joined to another member. The metal matrix composite material is composed of a metal as a simple substance or an alloy in which carbon fibers are contained in a uniaxially oriented state. In this metal matrix composite material, at least its contact surface to be brought into contact with another member is coated with a metal joinable to another member. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a metal matrix composite in which carbon fibers are oriented in a metal matrix, and a metal matrix composite structure in which a metal matrix composite and another member are closely bonded.

  Carbon nanotubes (CNTs), fullerenes, or carbon fibers are superior not only in mechanical properties but also in electrical properties and thermal properties compared to conventionally known reinforcing materials such as oxides and carbides. Are known.

  For the above reasons, composite materials using these as reinforcing materials are expected to be applied in a wide range of fields including automobile parts. In particular, composite materials with a metal matrix, that is, metal matrix composite materials, are superior in heat resistance, wear resistance, or thermal expansion characteristics compared to resin-based composite materials, and therefore can be expected to be used as automotive parts. . In recent years, since engine parts are used in harsh environments, not only light weight and high strength, but also heat transfer and low thermal expansion have been strictly demanded.

  By the way, when the above metal matrix composite material is applied specifically as a part, it is rather rare that the entire part is the above metal matrix composite material, and the metal matrix composite material in which the necessary properties are given only to the necessary parts. Is preferable from the viewpoint of material cost and manufacturing cost.

  In the above case, the metal matrix composite is joined to its peripheral part. However, when the material of the peripheral part is different from the composite matrix, it is not easy to perform so-called welding.

For example, when aluminum is used as the composite material matrix and iron-based metal is used as the peripheral part, a fragile intermetallic compound is generated when performing fusion welding, so it is not easy to perform sound welding. Absent.
“Light metal welding”, vol. 34 (1996), no. 2, p. 15-19 "Welding and Joining Handbook" 2nd edition, Maruzen, p. In addition, even when a copper-based metal is used as a peripheral portion instead of the iron-based metal, the fragile intermetallic compound is generated. As a technique for solving this problem, bonding by bonding, mechanical bonding such as bolt fastening, or bonding by brazing can be considered.

  However, in the case of bonding by adhesion, there is a limit to heat resistance and durability, and there is a problem that the parts to be applied are limited. Further, in the case of mechanical joining, since electrical and thermal resistance is increased at the joining interface, there is a possibility that the characteristic of high thermal conductivity of the composite material cannot be fully utilized. In addition, joining by brazing is a more realistic method, but in addition to the cost of sub-materials such as flux and brazing material, processing process for high accuracy, brazing equipment, or subsequent flux cleaning process, etc. There is a risk that the cost will increase. Moreover, when the matrix in a composite material is aluminum, there exists a possibility that carbon fiber may react and deteriorate by the heat effect at the time of brazing.

  On the other hand, even when the material of the peripheral part is the same kind of metal as the composite material matrix, it is difficult to say that fusion welding is easy. When the metal melts, the reinforcing material reacts with the carbon fiber to deteriorate, the distribution of the carbon fiber is disturbed, or defects such as blowholes are generated, so that the performance may be significantly impaired. In addition, when bonding by bonding, mechanical bonding such as bolt fastening, or bonding by brazing is used, the same problem as described above occurs. Furthermore, solid phase bonding such as friction welding, friction stir welding, or diffusion bonding is less deteriorated in the composite material than fusion bonding, but the joint shape of the joint is limited, and special equipment is required. Or there is a problem that processing time becomes long.

  An object of the present invention is a metal matrix composite that can be tightly bonded to a peripheral portion, and is a carbon fiber reinforced metal matrix composite having excellent thermal conductivity such as pitch-based carbon fiber and carbon nanotube, and the metal matrix composite An object of the present invention is to provide a metal matrix composite structure in which a material and its peripheral part are closely joined.

  As a result of intensive research to achieve the above object, the present inventor has coated the metal matrix composite material surface with at least the peripheral part with a metal that can be joined to the peripheral part. It has been found that this has been achieved, and the present invention has been completed.

  That is, the present invention is a metal matrix composite in which at least a part of the surface is intimately bonded to another member, and the metal matrix composite contains a single metal or carbon fiber uniaxially oriented. It is an alloy, and is a metal matrix composite in which at least a contact surface with the other member is coated with a metal that can be joined to the other member.

  Moreover, this invention is a metal matrix composite structure which consists of the said metal matrix composite material and the other member closely joined with the said metal matrix composite material.

  According to the metal matrix composite of the present invention, it is possible to tightly join the peripheral portion without impairing the characteristics of the metal matrix composite using carbon nanotubes, fullerenes, carbon fibers or the like as a reinforcing material.

Hereinafter, the metal matrix composite according to the present invention will be described in detail.

  First, a feature of the present invention is a metal matrix composite in which at least a part of the surface is tightly joined to another member, and the metal matrix composite contains a carbon fiber in a uniaxially oriented state. It is a metal or an alloy, and at least a contact surface with the other member is covered with a metal that can be joined to the other member.

  As the reinforcing material for the metal matrix composite material, it is preferable to use carbon fiber. Carbon fiber not only has high strength but also has a property of passing electricity and heat well, so it is preferable as a reinforcing material for metal matrix composites. Moreover, in order to make the most of the characteristics as a metal matrix composite, carbon fibers are contained in a metal matrix in a uniaxially oriented state.

  It is preferable that the metal matrix composite is closely joined to other members. By tightly joining the metal matrix composite to other members, for example, it is possible to continuously transmit stress, heat, or electrical resistance with a smaller resistance. In order to tightly join the metal matrix composite and the other member, a method in which the joining interface is metallicly bonded by melt bonding or solid phase bonding may be used.

  In addition, in order to tightly bond the metal matrix composite and the other member, at least the contact surface of the metal matrix composite with the other member is covered with a metal that can be bonded to the other member. preferable. Here, examples of the metal that can be joined include the same or the same type of metal as other members. However, it is not necessary to have exactly the same composition as long as the metal covered with the metal matrix composite and the other member do not form a fragile compound. For example, when the composite material matrix is an aluminum alloy and the other members are low carbon steel, it is preferable to use stainless steel as the metal matrix composite. When the composite material matrix is copper and the other member is an aluminum alloy, it is preferable to use aluminum or an aluminum alloy as the metal matrix composite material.

  The thickness of the metal coated on the metal matrix composite is not particularly limited. However, when the thickness is extremely thin, workability is poor when joining the metal matrix composite to another member. Therefore, it is preferably 0.5 mm or more, more preferably 1.0 mm or more.

  As the matrix metal in the metal matrix composite material, since it is lightweight and can be widely applied to structural members, aluminum or magnesium as a single metal, or an aluminum alloy or magnesium alloy as an alloy can be used. Of these, aluminum or an aluminum alloy is preferably used from the viewpoint of easy handling and excellent castability. However, it is not necessarily limited to these metals, and it goes without saying that a copper alloy or a zinc alloy can be used depending on the application.

  The carbon fiber contained in the metal matrix composite can be selected as appropriate considering the balance between the functions required for the metal matrix composite and the ease of production, but requires high strength and heat conductivity. In this case, it is preferable to use continuous carbon fiber. When using continuous carbon fiber, it is easy to manufacture other than the above as a merit of uniaxial orientation. In the above case, since the anisotropy of the metal matrix composite may increase, it is necessary to design the metal matrix composite in consideration of this point.

  As the continuous carbon fiber, it is preferable to use a pitch-based carbon fiber rather than a PAN-based one. This is because the pitch type is not only higher in thermal conductivity than the PAN type, but also has a wider selection of strength and elastic modulus.

On the other hand, when it is not desired to increase the anisotropy too much, or when there is a problem in the ease of manufacturing the metal matrix composite, it is preferable to use short carbon fibers rather than the continuous carbon fibers. Also in this case, it is preferable to use a pitch type for the same reason as described above. It is also preferable to use carbon nanotubes having excellent thermal conductivity.
Another advantage of using short carbon fibers is that when the metal matrix composite is produced by sintering by powder metallurgy, the matrix metal can be coated with another metal simultaneously with the sintering. The specific method is as follows. First, a metal-made powder as a matrix and short carbon fibers are filled and sealed in a container made of a metal that is coated in a mixed or composite state. Next, it is rolled or extruded at a high temperature to sinter the mixed powder or composite powder inside the container to form a composite material, and at the same time, the composite material is closely solid-phase bonded to the container to form a coating layer. To do.

  The content of continuous carbon fibers in the metal matrix composite is preferably 20 to 70% by volume. When the content is less than 20% by volume, the effect as a reinforcing fiber is small, and when the content exceeds 70% by volume, defects are likely to occur and the performance of the metal matrix composite is reduced. There is a fear.

Moreover, it is preferable that the content rate of a pitch-type short carbon fiber or a carbon nanotube in a metal matrix composite is 1-30 volume%. When the content is less than 1% by volume, the effect as a reinforcing fiber is small, and when the content exceeds 70% by volume, defects are likely to occur and the performance of the metal matrix composite is reduced. There is a fear.
Although the manufacturing cost increases, if necessary, both continuous carbon fibers and short carbon fibers may be included in the metal matrix composite.

  As a method of coating the metal matrix composite with a metal that can be bonded to another member, a low-temperature thermal spraying method can be employed because it is preferably a process that is less affected by heat and less expensive in a short time. In vapor deposition and sputtering, there is a problem that it takes too much time to cover a thickness of millimeter order. Overlaying using an arc or laser as a heat source tends to cause deformation of the base metal matrix composite due to thermal effects or defects such as blow holes.

  On the other hand, the coating method by thermal spraying can basically be processed in the air in a short time. Among the thermal spraying, for example, in the method of spraying high temperature molten particles on the base material and covering the base material like plasma spraying, the thermal influence on the base material is large. Therefore, it is preferable to employ a low temperature spraying method, specifically, a method called high-speed flame spraying or cold spraying, which is performed by spraying at a high speed in a semi-molten or unmelted state where the particle temperature is low. According to this method, the coating layer to be formed has few defects and has a high degree of adhesion to the base material, so that problems such as heat transfer performance hardly occur. Furthermore, mini-order coating can be easily performed in a short time without preparing a special apparatus such as a chamber. In addition, when covering only a part of the surface of the metal matrix composite material, it is preferable to mask the surface of the composite material in advance.

  By tightly bonding the above metal matrix composite and the metal matrix composite and other peripheral members, heat and stress can be transmitted with low resistance to the entire part to which the metal matrix composite is applied. it can. As described above, it is not preferable that excessive heat is applied when the metal matrix composite is joined to other peripheral members. Therefore, for example, it is preferable to perform high-speed welding using a heat source having a large energy density, such as laser welding or electron beam welding. Moreover, it is good to join only by heating only a joining interface in a short time like resistance welding. If you choose brazing, for example, in the case of a combination where the material to be coated is aluminum and the matrix of the metal matrix composite is an aluminum alloy, use a zinc-based brazing material with a low melting point in as short a time as possible. It is preferable to join.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example and a comparative example, this invention is not limited to these Examples.

Example 1
A metal matrix composite material containing 55% by volume of pitch-based continuous carbon fiber having a diameter of about 10 mm and using pure aluminum as a matrix metal was produced by a pressure casting method. Subsequently, the obtained metal matrix composite was coated with SUS410 to a thickness of about 2 mm by a high-speed flame spraying method, and then finished to a thickness of 1.5 mm. Obtained. Further, the metal matrix composite material of this example and the SS400 plate material were brought into contact, and the contact portion was irradiated with a YAG laser to melt weld the SUS410 layer and the SS400 plate material surface. The joint structure of the metal matrix composite material and the SS400 plate material in this example had no defects in the interface between the metal matrix composite material and the SS400 plate material and the welded portion, and was a close continuous body.

(Example 2)
A copper powder having a diameter of about 75 mm and a pitch middle short carbon fiber having a diameter of about 9 mm were blended so that the volume ratio was 95: 5, and these were mechanically mixed and integrated. Subsequently, the integrated mixture is filled and sealed in a pure aluminum container having a thickness of 3 mm, and is sintered by extruding at 500 ° C. to produce a metal matrix composite. At the same time, the metal matrix composite Was coated with pure aluminum to obtain a metal matrix composite of this example. Furthermore, using a zinc alloy brazing material having a melting point of 380 ° C., the metal matrix composite material of this example and the ADC12 plate material were ultrasonically brazed. As in Example 1, the joint structure of the metal matrix composite material and the ADC12 plate material of this example has no defects at the interface between the metal matrix composite material and the ADC12 plate material and the welded portion, and is a tight continuous body. It was.

(Comparative Example 1)
A metal matrix composite material containing 55% by volume of pitch-based continuous carbon fiber having a diameter of about 10 mm and using pure aluminum as a matrix metal was produced by a pressure casting method. The metal matrix composite was laser welded to the SS400 plate without covering the surface of the obtained metal matrix composite. In the joint structure of the metal matrix composite material of this example and the SS400 plate material, many defects such as cracks, blowholes, and irregular beats appeared in the welded portion, and a sound joint portion could not be obtained.

  From these results, the metal matrix composite of the present invention can be soundly joined to the peripheral portion thereof, and can provide a metal matrix composite structure that fully utilizes the characteristics of the metal matrix composite.

Claims (8)

A metal matrix composite in which at least a portion of the surface is intimately joined to another member,
The metal matrix composite is a single metal or alloy containing carbon fibers in a uniaxially oriented state, and at least a contact surface with the other member is coated with a metal that can be joined to the other member. A metal matrix composite characterized by the above.   The metal matrix composite according to claim 1, wherein the carbon fibers are continuous carbon fibers.   The metal matrix composite according to claim 2, wherein the continuous carbon fibers are pitch-based carbon fibers.   The metal matrix composite according to claim 2 or 3, wherein the content of the continuous carbon fiber is 20 to 70% by volume.   The metal matrix composite according to claim 1, wherein the carbon fibers are pitch-based short carbon fibers or carbon nanotubes.   The metal matrix composite according to claim 5, wherein the content of the pitch short fibers or the carbon nanotubes is 1 to 30% by volume.   The metal matrix composite according to any one of claims 1 to 6, wherein the metal coated on the metal matrix composite is coated by a low temperature spraying method.   A metal matrix composite structure comprising the metal matrix composite according to claim 1 and another member that is tightly joined to the metal matrix composite.