JPH0217617B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fiber-reinforced metal composite material (hereinafter referred to as a composite material) having excellent mechanical strength, which uses inorganic fibers as a reinforcing material and a metal or alloy (hereinafter referred to as a metal alloy) 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. Various methods have been used to prevent such fiber deterioration, such as treating the surface of the fibers with a coating agent, etc., but these pose problems such as troublesome handling and high cost, and are not practical. The present inventors have conducted intensive studies to improve the strength of composite materials using an easily implementable method. As a result, when added to metals, the surface tension of the metals is lowered, and the reactivity with alumina fibers is increased. We have discovered that by adding one or more metal elements whose reactivity with alumina fibers is lower than that of matrix metals, the mechanical strength of composite materials using these metals as a matrix can be dramatically improved. This led to the present invention. The present invention uses a metal or alloy selected from aluminum, magnesium, and copper (however, the alloy does not contain bismuth, tin, cadmium, antimony, and indium) as a matrix,
A fiber-reinforced metal composite material containing 15 to 70% by volume of alumina fibers as a reinforcing material, in which the matrix contains 0.05 to 10% by weight of at least one metal element selected from the group consisting of bismuth, cadmium, antimony, and indium. The present invention provides a fiber-reinforced metal composite material characterized by: The present invention will be explained in detail below. The proportion of alumina fibers contained in the composite material of the present invention is not particularly limited, but is preferably in the range of 15 to 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 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. The alumina fiber that can most significantly exhibit the metal reinforcing effect of the present invention is the alumina fiber described in Japanese Patent Publication No. 51-13768. That is, the alumina (Al ₂ O ₃ ) content is 72% by weight or more and 100% by weight or less, preferably 75% by weight or more and 98% by weight or less, and the silica (SiO ₂ ) content is 0% by weight or more and 28% by weight or more.
Less than 2% by weight, preferably 2% by weight or more, 25% by weight
It has the following composition, and in the X-ray structure α
-Alumina fibers that do not substantially exhibit Al ₂ O ₃ reflection. This alumina fiber contains lithium, beryllium, boron, sodium, magnesium, silicon, phosphorus, etc. within a range that does not impair the effects of the present invention.
It may contain refractory compounds such as oxides of one or more of potassium, calcium, titanium, chromium, manganese, yttrium, zirconium, lanthanum, tungsten, barium, and the like. Preferred matrix metals used in the present invention are aluminum, magnesium,
Copper or alloy (however, the alloy does not contain bismuth, tin, cadmium, antimony, or indium). When light weight and high strength are required, a matrix of aluminum or magnesium metal or alloy is suitable.
When heat resistance and high strength are required, a system using copper or an alloy as a matrix is 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. Particularly suitable metal elements to be added to the above-mentioned metals in the present invention include bismuth, cadmium, antimony, and indium. The first condition required of these additive metal elements is that when added to matrix metals, they must lower the surface tension of the metals. This is because the concentration of the added element on the surface of the metal needs to be higher than the average concentration of the added element in the alloy;
It is shown by the Gibbs adsorption isotherm. Γ ₂ = -1/RTd〓/dlnC ₂ However, Γ ₂ : Surface concentration of component (2) adsorbed at the interface (mole/cm ² ) d〓 : Change in surface tension (dyn/cm) C ₂ : Concentration of component (2) R: Gas constant T: Absolute temperature In other words, the more remarkable the decrease in surface tension with respect to changes in the added element concentration _C2 , the higher the surface concentration of the added element. There is. In the present invention, 0.1
Preferred are metal elements that, when added in mol %, lower the surface tension of the matrix metal by 5 dyn/cm or more, preferably 10 dyn/cm or more. Additive elements that exhibit only a decrease in surface tension of 5 dyn/cm or less are not preferable because the surface concentration of the additive elements does not become too high. For example, adding 0.1 mol% of bismuth, cadmium, antimony, indium, etc. to aluminum increases the surface tension of aluminum to 400, 15, 105, respectively.
20 dyn/cm ² , indicating that these additive elements exist in high concentration on the aluminum surface. That is, it is considered that a situation occurs in which large amounts of these additive elements are present at the contact interface between the alumina fiber and the matrix metal. actually,
The present inventors confirmed these facts through Auger scanning microscope and EPMA (Electron Probe Micro Analyser) analysis. The second condition required for these additive elements is that they either do not react with the alumina fibers, or even if they do, they must have a reactivity lower than the reactivity of the matrix metals with the alumina fibers. . The free energy change of compound formation can be considered as an indicator of this. When considering the case where alumina fiber is used as a reinforcing material, it can be systematically considered based on the free energy change (per 1 atomic equivalent of oxygen) of matrix metals and additive metal elements to form oxides.
(Hereinafter, the change will be written as △Go). For example, △Go of aluminum and magnesium are −
122, -136 Kcal/mole, and this value tends to increase slightly with increasing temperature. However, all metal elements show almost the same slope with respect to temperature, and the size order of △Go at room temperature is relatively the same as the size order at high temperature. The smaller the ΔGo value, the easier it is to form oxides. The values of △Go for bismuth, cadmium, antimony, and indium are −
39, -55, -50, -67 Kcal/mole, and when aluminum or magnesium is used in the matrix, the reaction between the alumina fibers and the matrix is suppressed and it has an appropriate interfacial bond strength, making it a composite material with improved strength. It gives. By the mechanism described above, the strength of the composite material can be dramatically improved by adding a metal element that satisfies these two conditions to the matrix metal. The preferred amount of these additional metal elements is 0.05% to 10% by weight, more preferably 0.1% to 5% by weight, based on the matrix metal. If the amount added is less than 0.05% by weight, the effects of the present invention will not be noticeable. Furthermore, if the amount added is more than 10% by weight, the properties of the matrix metals will be impaired, corrosion resistance will be reduced, elongation will be reduced, and the reaction between the fibers and the matrix metals will be completely suppressed, resulting in the strength of the composite material. The improvement effect will also be smaller. Various methods can be used to add these additional metal elements to the matrix metal, and no problem will occur if they are added according to a general alloy manufacturing method. For example, there is a method in which a metal serving as a matrix is melted in a crucible in air or under an inert atmosphere, one or more desired additional metal elements are added, and the matrix is sufficiently stirred and cooled. 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. Ru. The effects of the present invention are particularly noticeable when molten metal and fibers come into direct contact, such as in (1) the liquid metal impregnation method and (6) in the high-pressure solidification casting method. (Five)
The manufacturing method shown in Figure 1 is also clearly effective. The composite material produced in this way has a significant improvement in 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 with reference to Examples below, but the present invention is not limited thereto. Example 1 A graphite crucible is heated to approximately 700°C under an argon atmosphere, and a pure aluminum ingot (purity 99.9%) is placed inside it.
After adding 500 gr and melting, 2.5 gr of bismuth was added and thoroughly stirred with a carbon steel rod to prepare an aluminum-bismuth alloy. Compositional analysis confirmed that this alloy contained 0.501% by weight of bismuth. Alumina fiber with average fiber diameter 14μ, tensile strength 150Kg/mm ² , tensile modulus 23500Kg/mm ² (Al ₂ O ₃ content 85% by weight, SiO ₂ content 15
% by weight), were cut into lengths of 110 mm, bundled, and drawn in parallel into a mold tube with an inner diameter of 4 mm. Next, one end of the mold tube was immersed in the molten aluminum-bismuth alloy kept at 700°C in an argon gas atmosphere, and while the other end was being degassed under vacuum, a
A fiber-reinforced metal composite material was obtained by applying a pressure of Kg/cm ² to infiltrate the aluminum-bismuth alloy between the fibers and cooling it. The fiber volume content was adjusted to 50±1%. For comparison, a fiber-reinforced metal composite material was obtained using the same method using pure aluminum (99.9% purity) as a matrix. 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, and the strength was significantly improved compared to the comparative example.

[Table] Example 2 An alloy was produced by adding cadmium, antimony, and indium in a proportion of 1% by weight to aluminum in exactly the same manner as shown in Example 1. The composition determined by the composition analysis is shown in Table 2. A fiber-reinforced metal composite material was produced using the same alumina fibers as used in Example 1 and in the same manner as in Example 1. Table 2 shows the results of measuring the bending strength and bending elastic modulus of this composite material at room temperature. All exhibited higher bending strength than Comparative Example 2 in Table 1.

[Table] Example 3 A case where the matrix metal is changed to magnesium or copper is shown. In the case of magnesium, use 250 grams of commercially available pure magnesium (99.9% purity).
6.0 grams of bismuth was placed in a graphite crucible, heated to approximately 700°C under an argon gas atmosphere, thoroughly stirred, and cooled to room temperature.
-Bi alloy was obtained. This alloy has a compositional analysis of 2.36
It contained % by weight of bismuth (hereinafter referred to as Mg-
2.36Bi). This alloy is used as a matrix,
Composite was performed 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 fabricated under the same conditions. Next, with 98.0 grams of copper powder (300 mesh passes)
2.0 grams of bismuth powder (300 meshyupas),
The same alumina fibers used in Example 1 were immersed in a suspension of polymethyl methacrylate in a chloroform solution to produce an alumina fiber sheet whose surface was coated with Cu and Bi powder. This sheet had a thickness of approximately 250μ and a fiber content of 56.7% by volume. 10 of these sheets were stacked together and placed in a carbon mold and vacuum hot pressed.
After decomposing and removing the binder polymethyl methacrylate at 10 ^-2 Torr and 600℃ for 2 hours, the pressure was gradually increased.
Heating was finally maintained at a pressure of 10 ^-3 Torr 1010°C and 250 Kg/mm ² for 2 hours to obtain a fiber-reinforced metal composite material. For comparison, a fiber-reinforced metal composite material containing only copper as a matrix was prepared using the same method and conditions. Table 3 shows the results of measuring the bending strength of these composite materials at room temperature. In either case, the addition of bismuth significantly improved the bending strength.

【table】

Claims (1)

[Claims] 1 The matrix is a metal or alloy selected from aluminum, magnesium, and copper (however, the alloy does not contain bismuth, tin, cadmium, antimony, and indium), and contains 15 to 70% by volume of alumina fiber as a reinforcing material. 1. A fiber-reinforced metal composite material, characterized in that the matrix contains 0.05 to 10% by weight of at least one metal element selected from the group consisting of bismuth, cadmium, antimony, and indium.