JPH0122337B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a fiber-reinforced metal composite material (hereinafter referred to as composite material) with excellent mechanical strength, which uses inorganic fibers as a reinforcing material and metal or alloy (hereinafter referred to as metals) as a matrix. In recent years, inorganic fibers such as alumina fiber, carbon fiber,
Composite materials have been developed that use silica fibers, silicon carbide fibers, boron fibers, etc. and matrices of aluminum, magnesium, copper, nickel, titanium, etc., and are beginning to be used in many industrial fields. When inorganic fibers and metals are composited, a reaction occurs at the interface between the molten or high-temperature metals and the inorganic fibers, resulting in the formation of a brittle layer. For this reason, the strength of the composite material decreases, often giving a strength lower than the theoretical strength. For example, commercially available carbon fiber has a weight of approximately 300Kg/mm ²
It has a certain strength and the fiber content is 50% by volume.
Even if the strength of the matrix material is ignored, the theoretical strength of carbon fiber reinforced composite material is 150 kg/
Estimated to be about mm ² . In fact, carbon fiber-reinforced composite materials with an epoxy resin matrix exhibit a strength of 150 Kg/mm ² or more, but carbon fiber-reinforced metal composite materials with an aluminum matrix made using the molten metal impregnation method have a strength of at most 150 Kg/mm 2 or more. 30-40
Provides only a strength of about Kg/mm ² . This is because, as mentioned above, when the fibers come into contact with the molten metal, an interfacial reaction occurs, causing fiber deterioration. Various methods have been used to prevent such fiber deterioration, such as treating the surface of the fiber with a coating agent or the like. For example, as disclosed in JP-A-53-30407, the surface of silicon carbide fibers is protected with metals or ceramics that form compounds that are inert or stable with respect to carbon, and then composited with matrix metals. Although this method is effective for silicon carbide fibers, it is not practical for other inorganic fibers due to problems such as troublesome handling and high cost. . On the other hand, JP-A-51-70116 states that the mechanical strength of fiber-reinforced metal composite materials is improved by adding several percent of lithium to the aluminum matrix. However, this method does not allow the inorganic fibers to get wet with the matrix metals at all.
Although it is effective when there is no reaction, it is ineffective when the inorganic fiber reacts with matrix metals and deteriorates, and on the contrary tends to cause a decrease in strength. As shown above, at present, it has not been possible to improve the mechanical strength of fiber-reinforced metal composite materials by an easy and inexpensive method. The present inventors believe that in order to improve the strength of fiber-reinforced metal composite materials, it is necessary to prevent the deterioration of the inorganic fibers due to the reaction at the interface between the inorganic fibers and the matrix metals. We worked hard to find a method that could be implemented at low cost. As a result, a metal or alloy selected from aluminum and magnesium (however, the alloy does not contain bismuth, tin, cadmium, antimony, indium, barium, strontium, and radium) is used as a matrix, and bismuth, tin, By adding at least one inorganic compound or organic compound of a metal element selected from the group consisting of cadmium, antimony, indium, barium, strontium, and radium from 0.0005% by weight to 10% by weight, calculated in terms of the weight of the metal element. The present inventors have discovered that it is possible to prevent the deterioration of inorganic fibers due to the reaction between inorganic fibers and matrix metals, and that the mechanical strength of composite materials using these metals as a matrix is dramatically improved, leading to the present invention. It is believed that adding these metal elements to the matrix metal has the effect of improving the strength of the fiber-reinforced metal composite material, as estimated below. It is characterized in that even when added to metals, it has the same effect as adding the metal alone. In general, metals alone are difficult to handle because they are easily oxidized and have toxicity. However, by making it into a compound form, it becomes stable and extremely easy to handle, and there are no problems such as controlling the atmosphere when adding it to matrix metals, which has great advantages in industrial production. The present invention will be explained in detail below. The inorganic fibers used in the present invention include carbon fibers,
These include silica fibers, silicon carbide fibers containing free carbon, boron fibers, and alumina fibers. The proportion of inorganic fibers contained in the composite material of the present invention is not particularly limited, but is preferably 15
~70% by volume. If it is less than 15% by volume, the reinforcing effect will be small, and if it exceeds 70% by volume, the strength will decrease due to contact between the fibers. As for the fiber shape, either long fibers or short fibers can be used, and either one or both can be used at the same time depending on the purpose and use. Orientation methods such as unidirectional cross ply and random orientation can be selected to obtain the desired mechanical strength or elastic modulus. Among these inorganic reinforcing fibers, the fiber that can most significantly exhibit the metal reinforcing effect of the present invention is
This is an alumina fiber described in No. 13768. That is, the general formula (In the formula, Y represents one or more of organic residues, halogens, and hydroxyl groups.) Polyaluminoxane having a structural unit represented by is used as a raw material, and the silica content in the silica alumina fiber obtained from this is 28 It is an alumina fiber obtained by mixing one or more compounds containing silicon in an amount of 2% or less, and firing a precursor fiber obtained by spinning the mixture, and preferably having a silica content of 2% or less. It has a composition of at least 25% by weight and is an alumina fiber that does not substantially show α-Al ₂ O ₃ reflection in its X-ray structure. The alumina fibers may include lithium, beryllium, boron, sodium, magnesium, silicon, phosphorus, potassium, calcium, titanium, chromium, manganese, yttrium, zirconium, lanthanum, tungsten, barium, etc. within a range that does not impair the effects of the present invention. It may contain a refractory compound such as one or more oxides of. Preferred matrix metals for use in the present invention are aluminum, magnesium, or alloys thereof. When light weight and high temperature are required, systems using these metals or alloys as a matrix are suitable. These metals referred to in the present invention may contain small amounts of impurity elements as long as they do not interfere with normal use. Although the mechanism of strength improvement due to the added metal is not clear, it is thought to be as follows. When the additive elements mentioned above are added to metals, the concentration of these additive elements on the surface of the metal becomes higher than the average concentration. For example, if the metal is aluminum, bismuth, tin, cadmium, antimony, indium, strontium,
By adding 0.1 mol% of barium, the surface tension of aluminum becomes 400, 40, 15, 105, 20, 60, respectively, higher than that of pure aluminum.
Decreased by 300dyn/cm. This is because the concentration of these added elements at the surface is higher than the average concentration in the matrix, as shown by the Gibbs adsorption isotherm. In fact, we used the Auger scanning microscope and the EPMA
(Electron Probe Micro Analyser) analysis confirmed these facts. Next, when the fractured surface of an inorganic fiber-reinforced metal composite material with a matrix of metals containing these additive elements was observed with a scanning electron microscope, it was found that it contained one or more of bismuth, tin, cadmium, antimony, and indium. In fiber-reinforced metal composite materials with aluminum as a matrix, the bond at the fiber-matrix interface is weaker than in systems without additive elements. Phenomena such as the disappearance of the reactive phase with the matrix metal observed on the outer peripheral surface of the fibers are observed, and it is observed that the reaction at the fiber-matrix interface is reduced. In other words, these additive elements of the present invention exist in high concentration at the fiber-matrix interface and have the function of controlling reactions at the interface.
Therefore, it is thought that the strength of the composite material will be dramatically improved. On the other hand, barium, strontium, radium,
Fiber-reinforced metal composite materials with a matrix of metals containing one or more of Phenomena such as the reaction phase with the matrix metal that was observed in 2011 has disappeared. When we measured the strength of the fibers extracted from this composite material by dissolving and removing the matrix metal using an aqueous hydrochloric acid solution, we observed a considerable decrease in strength in the system without additive elements compared to the fiber strength before composite formation. On the other hand, in the systems in which these additive elements were present, almost no decrease in strength was observed. From the above, these additive elements exist in high concentration at the fiber-matrix interface and have the function of suppressing the reaction between the fibers and matrix metals by reacting with the fibers in a single layer. It is thought that the strength of the material will be dramatically improved. The preferred amount of the inorganic compound or organic compound of these additional metal elements is 0.0005% by weight or more and 10% by weight or less based on the matrix metal, calculated in terms of the weight of the metal element. Added amount is 0.0005% by weight
If the amount is less, the effect of the present invention will not be noticeable. If the amount added is more than 10% by weight, the properties of the matrix metals will be impaired, leading to problems such as a decrease in corrosion resistance and a decrease in elongation. Various methods can be used to add these metal elements to the matrix metals. For example, there is a method in which a metal serving as a matrix is melted in a crucible, one or more inorganic compounds or organic compounds of a desired metal element are added, and the matrix is sufficiently stirred and cooled. Further, for certain methods of manufacturing composite materials, it is also possible to use a mixture of matrix metal powder and inorganic compound or organic compound powder of these metal elements. Any other method can be used to bring out the effects of the present invention as long as the inorganic or organic compound of the metal element can be included in the metal that will eventually form the matrix. Various inorganic or organic compounds of these metal elements can be used, but the following are effective examples. Halides, hydrides, oxides, hydroxides, sulfides, nitrates, carbonates, chlorine oxides, carbides, nitrides, phosphorus oxides, sulfides, phosphides, alkylates,
These include organic oxides and alcoholates. The composite material of the present invention can be manufactured by various methods. The main methods are (1) liquid phase methods such as liquid metal impregnation, (2) solid phase methods such as diffusion bonding,
Examples include (3) powder metallurgy (sintering, welding), (4) deposition methods such as thermal spraying, electrodeposition, and vapor deposition, (5) plastic processing methods such as extrusion and rolling, and (6) high-pressure solidification casting methods. The effects of the present invention are particularly noticeable when molten metal and fibers come into direct contact, such as (1) liquid metal impregnation method and (6) high-pressure solidification casting method, but (2) The manufacturing methods shown in (5) to (5) are also clearly effective. The composite material produced in this way has significantly improved mechanical strength compared to the case where the additive metal element used in the present invention is not present. In addition, the fact that the present invention can be carried out without making any changes to existing equipment or methods is a great advantage in terms of actual production. EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto. Example 1 Aluminum was melted in a carbon crucible, and the first
The matrix metal was prepared by adding chloride of each metal shown in the table. As an inorganic fiber, (1) average fiber diameter 14μm, tensile strength 150Kg/mm ² , elastic modulus 23500
Kg/mm ² alumina fiber (Al ₂ O ₃ content 85% by weight,
(SiO ₂ content 15% by weight), (2) Carbon fiber with average fiber diameter 7.5 μm tensile strength 300 Kg/mm ² and elastic modulus 23000 Kg/mm ² (3)
Average fiber diameter 15μm, tensile strength 220Kg/mm ² , elastic modulus
Using silicon carbide fiber containing 20000Kg/ ^mm2 of free carbon, the fiber content was made into a molded tube with an inner diameter of 4mmφ.
It was drawn in parallel so that it was 50% by volume. Next, the above alloy was melted at 700°C in an argon gas atmosphere,
One end of the mold tube was immersed in this, and while the other end was vacuum degassed, a pressure of 50 kg/mm ² was applied to the molten surface to allow the matrix metal to penetrate between the fibers, which was then cooled to complete the composite. . For comparison, a fiber-reinforced metal composite material was also obtained using pure Al (purity 99.9%) as a matrix using the same method. The bending strength and bending elastic modulus at room temperature of the fiber-reinforced metal composite material thus produced were measured. The results are shown in Table 1. In both cases, a significant improvement in strength was observed compared to composites using pure Al as a matrix.

[Table] Example 2 The case where the added metal compound was changed to barium hydroxide or cadmium acetate is shown. Aluminum is placed in a graphite crucible, heated to 700°C to melt it, and a certain amount of barium hydroxide or cadmium acetate shown in Table 2 is poured into it.
Mixed. Next, a fiber-reinforced metal composite material was obtained by the method shown in Example 1 using the same alumina fibers as used in Example 1. The fiber content of the composite material was adjusted to 50%. Table 2 shows the results of measuring the bending strength and bending modulus of this composite material. In all cases, a significant improvement in strength was observed compared to composites using pure Al as a matrix.

[Table] Example 3 The case where the matrix metal was changed to magnesium is shown. In the case of magnesium, place 1000 g of commercially available pure magnesium (99.9% purity) and 15 g of barium bromide in a graphite crucible, create an argon gas atmosphere, heat the crucible to approximately 700°C, stir thoroughly, and then cool to room temperature. did. This alloy was used as a matrix and composited at 700°C using the alumina fibers and composite method used in Example 1 to obtain a fiber-reinforced metal composite material. For comparison, a fiber-reinforced metal composite material using pure magnesium as a matrix was produced under the same conditions. Table 3 shows the results of measuring the bending strength and bending modulus of this composite material. It can be seen that the bending strength is considerably improved compared to the comparative example.

【table】

Claims (1)

[Claims] 1 Metal or alloy selected from aluminum and magnesium (however, bismuth,
Free of tin, cadmium, antimony, indium, barium, strontium and radium. ) as a matrix and 15 to 70% by volume of inorganic fibers as a reinforcing material.
At least one inorganic compound or organic compound of a metal element selected from the group consisting of tin, cadmium, antimony, indium, barium, strontium, and radium is added in an amount of 0.0005% by weight or more and 10% by weight or less in terms of the weight of the metal element. A method for producing a fiber-reinforced metal composite material.