Method of producing aluminum composite material

Abstract

A manufacturing method of an aluminum composite material having excellent abrasion resistant and vibration damping properties is disclosed. The aluminum composite material is manufactured by impregnating a perform with an aluminum alloy the perform is formed by mixing an alumina fiber and graphite or activated charcoal and an inorganic binder in water and sintering the resultant mixed product at a predetermined sintering temperature under vacuum, in an inert gas, or in a reducing gas.

Description

BACKGROUND OF THE INVENTION [0001] (1) Field of the Invention [0002] The present invention relates to a method of producing aluminum composite material produced by mixing an aluminum fiber and graphite or activated charcoal to an aluminum alloy. [0003] (2) Description of the Background Art [0004] An aluminum alloy has been optimally used in devices including such as automobiles, electric appliances, electronic parts, and precious measurement equipment because of its lightness and malleability. Nevertheless the application of the aluminum alloy is limited to a sliding portion of structure because of low resistance to abrasion. Further, especially in an automobile, comfortable ride and driving performance are not well achieved due to noise and vibration because an aluminum alloy has lower vibration damping property than a cast iron. Accordingly, various composite materials such as graphite and activated charcoal with superior lubricating property and damping property have been added t...

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Benefits of technology

[0015] According to two manufacturing methods, a formed base material obtained by dehydrating and forming the aqueous mixture solution of the alumina fiber, graphite or activated charcoal, and the inorganic binder has almost an homogeneous structure of the alumina fiber and graphite or activated charcoal because graphite and activated charcoal can be coagulated to the alumina fiber by addition of the inorganic binder. Further an oxidation-loss of graphite or activated charcoal over approximately 600° C. can be prevented by heating and sintering the dehydrated-formed base material at the designated sintering temperature under vacuum, in an inert gas or in a reduced gas, and accordingly a preform appropriately having graphite or activated charcoal can be formed. Further a heat-contraction of the preform can be prevented because graphite or activated charcoal does not either coagulate or react with the alumina fiber when it is heated under vacuum, in an inert gas or in a reducing gas. Accordingly a preform having high strength and high breathability can be formed because the temperature of sintering the alumina fiber can be raised farther. Accordingly the preform formed by processing to form the preform above comprises structure dispersing graphite and activated charcoal almost in homogeneous with an excellent strength and breathability.

[0016] The hot solution of aluminum alloy is pressurized and cast to the preform above having high strength and high breathability by an impregnation process. Crush of the preform can be prevented because the preform formed in the preform forming process has high strength and the aluminum alloy, the aluminum fiber and graphite or activated charcoal can make a complex almost in homogeneous. The hot solution of aluminum is easily impregnated because the preform has high breathability and occurrence of voids of the composite material after forming can be adequately prevented. Specifically according to the preform forming process and aluminum impregnation process, the aluminum composite material having excellent abrasion resistant and vibration damping properties can be obtained with graphite or activated charcoal which are existing almost in homogenous and dispersedly.

[0017] Further the aluminum composite material manufactured according to the method of the invention has a low thermal expansion coefficient because graphite or activated charcoal has a low thermal expansion coefficient and also the thermal expansion coefficient of alumina fiber is low, and accordingly a thermal deformation occurs unlikely and excellent form stability can be achieved. Further the aluminum composite material manufactured by mixing graphite can retain the excellent thermal conductivity coefficient of aluminum alloy because graphite has relatively a high thermal conductivity coefficient.

[0018] Further such as alumina sol, silica gel and lithium silicate as an inorganic binder can be applied adequately. When such inorganic binder is used, the mixed alumina fiber and graphite or activated charcoal powder in water can coagulate with sufficient strength by hydration. Further the aluminum composite material is that alumina fiber, graphite or activated charcoal are combined with sufficient adhesion because of excellent adhesion of such inorganic binder, and accordingly father excellent abrasion resistant and vibration damping properties can be obtained.

[0021] According to another implementation of the invention, the manufacturing method is for the alumina fiber having an average diameter in the range of 1 μm to 10 μm and the average length of 10 cc / 5 gf to 100 cc / 5 gf. The average length of alumina fiber is defined as a volume per weight unit because the alumina fiber is generally complex and intertwined. The preform can be formed with adequate compact density by using such average diameter and average length, and accordingly the preform can be excellently strong and breathable. If an average diameter of the alumina fiber is larger than 10 μm, the preform is easily crushed because the volume is large and the strength of the preform is insufficient. If an average length of the alumina fiber is larger than 100 cc / 5 gf, a deformation and breaking easily take place because the compact density of the preform is lower and the strength of the preform is insufficient. Further, if the average diameter is smaller than approximately 1 μm or the average length is smaller than approximately 10 cc / 5 gf, an defect can easily take place because breathability of the perform is insufficient and the preform cannot sufficiently impregnate the aluminum alloy. Preferably the average diameter is in the range of 1 μm to 5 μm and the average length is in the range of 20 cc / 5 gf to 60 cc / 5 gf in order to form the preform which has farther excellent strength and breathability. Further, even if some alumina fiber out of the range more or less is mixed, the targeted aluminum composite material can be obtained and accordingly these are also covered by the invention.

[0023] According to an implementation of the invention, a manufacturing method that the impregnating process above forms a layering structural material of a complex material layer impregnating the aluminum alloy to the preform and the aluminum alloy layer is disclosed. In such manufacturing method, the layering structural material comprising a complex material obtained by which the aluminum alloy impregnates to the preform and an aluminum alloy layer solidified without impregnating to the prefonr is formed by using a hot solution of the aluminum alloy used in pressurized casting which is more than an impregnating volume to the preform. Accordingly, the layering structural material comprising the aluminum composite material above having excellent abrasion resistant and vibration damping properties and the aluminum alloy can be easily formed and the layering structural material has a structure in which strength between layers is excellent because the composite material layer and the aluminum alloy layer are integrally formed. EMBODIMENTS

Problems solved by technology

Nevertheless the application of the aluminum alloy is limited to a sliding portion of structure because of low resistance to abrasion.

Further, especially in an automobile, comfortable ride and driving performance are not well achieved due to noise and vibration because an aluminum alloy has lower vibration damping property than a cast iron.

Even though heating over 600° C. by hot solution or sintering of aluminum alloy are used in the methods above, no means to prevent the oxidation of activated charcoal or graphite was disclosed and accordingly the oxidation-loss of activated charcoal and graphite could not be prevented.

Thus it was difficult to obtain an aluminum alloy composite material having excellent abrasion resistant and vibration damping properties.

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