JPH01309934A - Manufacture of ceramics-alloy composite body - Google Patents

Abstract

PURPOSE:To manufacture a homogeneous ceramics-alloy composite body with good efficiency by violently stirring a mixed melt of an Al alloy, etc., and specific amt. of Ca in the presence of O2 to progress its oxidation and adding ceramics to the melt at the time when its viscosity reaches the optimum one. CONSTITUTION:A Ca mixture, i.e., an alloy of one kind among Al alloy, Mg alloy, Sn alloy, Pb alloy and Zn alloy with 0.05-5wt.% Ca is refined. The melt of the mixture is continued to stir violently in the presence of O2 to progress the oxidation and to increase the viscosity of the melt. At the time when the viscosity of the melt reaches the one suitable for the adding and mixing of ceramic grains, ceramics are added thereto to progress the dispersion. By this method, the alloy and the ceramics are uniformly mixed in a short toughening time to obtain the homogeneous composite body.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for uniformly mixing mutually immiscible molten alloys and ceramics to produce homogeneous composites.

BACKGROUND OF THE INVENTION Recently, in order to obtain materials with properties suitable for various purposes, alloys have been mixed with various ceramic particles to form composites.

For example, graphite fine particles are added to aluminum alloys and copper alloys to make anti-friction materials, ultra-light vitreous microscopic hollow spheres such as glass balloons are mixed into aluminum alloys at a high blending rate to make lightweight composite materials, and aluminum The addition of short carbon fibers and fillers such as oxides and carbides to alloys and other alloys to improve their strength, and the addition of particles containing foaming sources such as shirasu, mica and calcium carbonate to molten aluminum alloys. It is known that foaming is performed to produce an ultra-lightweight foamed aluminum alloy.

However, the ceramics used in these composites generally have poor wettability with the molten alloy, and there is a difference in specific gravity between the two, so even if ceramic particles are added to the molten alloy and thoroughly stirred, the two will not be completely dispersed. It is difficult to separate the two during cooling and solidification. Up until now, methods to solve these difficulties have included coating the surfaces of ceramic particles with metal in advance and adding this to the molten alloy, and strictly controlling the temperature of the molten alloy, alloy components, and mixing conditions of the ceramic particles. However, the process is complicated and the expected effect cannot be obtained, so it cannot be said to be a fully satisfactory industrial method.

In addition, as a method to increase the viscosity of the molten alloy and make it possible to disperse ceramics, we use an alloy component that has a wide temperature range between the solidus and liquidus lines. A method in which solid phase particles are uniformly dispersed by strong stirring; a high viscosity solid-liquid coexistence melt is formed, and ceramic particles such as silicon carbide, aluminum oxide, and silicon oxide are added to this, or a molten alloy is used. A gas such as air, oxygen, or carbon dioxide is blown into the melt and stirred, and the viscosity is thickened by fine oxide particles that are uniformly generated in the melt, and foamable ceramic is added and mixed to obtain an alloy foam. Methods are known.

However, these thickening methods have limitations on the applicable molten alloys and ceramics, and require strict condition control.
It cannot be said that it can be used universally.

Problems to be Solved by the Invention The present invention overcomes the drawbacks of the conventional composite manufacturing method and provides a uniform method of combining molten alloy and ceramic, which can be commonly applied to many alloys. The purpose of this invention is to provide a method for industrially producing a homogeneous composite by mixing.

Means for Solving the Problems The present inventors have conducted various studies in order to develop an industrial method for producing a composite material having such favorable characteristics.
When melts such as aluminum alloys, magnesium alloys, tin alloys, lead alloys, and zinc alloys containing a small amount of metallic calcium are vigorously stirred in the presence of oxygen, their viscosity increases significantly, and when ceramic particles are added The present inventors have discovered a scale that provides a sufficient dispersion state, and have completed the present invention based on this knowledge.

That is, the present invention provides an alloy of one type of alloy selected from aluminum alloys, magnesium alloys, tin alloys, lead alloys, and zinc alloys and 0.05 to 5% calcium based on the weight of the calcium alloy. After melting the mixture,
A ceramic-alloy composite characterized in that the molten mixture is continuously stirred vigorously in the presence of oxygen to promote oxidation until it reaches a viscosity suitable for addition and mixing of ceramic particles, and then ceramic-alloy composite is added and dispersed. The present invention provides a method for manufacturing.

The present invention will be explained in detail below.

It is generally observed that the addition of metallic calcium to a melt of the metal slightly increases the viscosity. This phenomenon of thickening due to alloying is well known and is an important phenomenon in casting, as seen, for example, when titanium, iron, copper, etc. are melted into molten aluminum.

However, the increase in viscosity due to the dissolution of calcium alone cannot provide sufficient viscosity to allow the arbitrary addition and mixing of various ceramic particles, and only a small possibility has been recognized in the system of aluminum-glass hollow spheres. It's just a matter of getting caught.

On the other hand, the mechanism of thickening of molten alloy containing calcium by stirring in the presence of oxygen is considered as follows. You can get it. In other words, since calcium is the element with the highest affinity for oxygen, after being added to the molten alloy and dissolved, the calcium component that comes into contact with air immediately oxidizes to become fine calcium oxide, which is dispersed in the molten alloy by stirring. do. With continued stirring, the amount of calcium oxide in the molten alloy gradually increases, and at the same time the apparent viscosity increases significantly. A feature of the present invention is to utilize such preferential oxidation of calcium in the molten alloy.

As described above, the method of increasing the apparent viscosity by forcefully oxidizing the molten aluminum alloy by blowing air or the like into the molten aluminum alloy has been shown to be effective. It requires long air blowing and is dangerous for magnesium alloys, while air blowing has little thickening effect on tin alloys, lead alloys, and zinc alloys. Furthermore, the thickening method using the solid-liquid coexistence region of an alloy cannot be applied to eutectic alloys. Furthermore, the method of coating ceramic fine particles with a metal film in advance is economically disadvantageous.

In contrast, the method of the present invention preferentially oxidizes added calcium rather than oxidizing the molten alloy itself, so the oxidation rate is high, the thickening time is short, and it can be applied to any alloy system. Furthermore, it has excellent features such as being able to use any material or shape of the ceramic particles to be composited.

Conventionally, there have been very few calcium additives for metals, and only a very small amount (0.01 to 0.02% or less) is known to be used as an antioxidant or deoxidizer. However, since calcium generally embrittles the alloy, it should be avoided to add a large amount.

As a result of thorough consideration of this point, the present invention found that the amount of calcium added to the melt of the alloy becomes significant from 0.05%, and exceeds 5%, based on the weight of the melt. This increases the thickening effect, but the alloy itself becomes significantly brittle and loses its properties, so the amount added is selected within the range of 0.05% to 5%. It is preferably in the range of 0.5% to 1%, but it varies depending on the type of molten alloy and the amount of ceramic particles added.

Effects of the Invention The method of the present invention can be commonly applied to many alloys, and can evenly mix molten alloy and ceramic, thereby easily obtaining a homogeneous composite. It has the remarkable effect of being able to

As already mentioned, the field of application of the present invention is the production of various ceramic-alloy composites that require the dispersion of ceramic particles in the alloy, and specifically, for example, graphite and Alloy composites, lightweight vitreous micro hollow spheres/alloy composites for the purpose of lightweight alloys, fine particles of oxides, carbides, nitrides, carbon, etc. for the purpose of strengthening, short fiber/alloy composites, ultra-lightweight It is also applicable to foamed alloys using ceramics containing foaming sources such as shirasu, mica, carbonates, and hydrides for the purpose of foaming.

Example Next, the present invention will be explained in more detail with reference to Examples.

Example 1 After adding and mixing 5 g of calcium to 1 kg of Al2-12%Si alloy, which was maintained in a molten state at 680°C in a #1O graphite crucible using an electric furnace and subjected to thickening treatment,
After adding 500 ml of shirasu balloons with an average particle size of 150 μm and retaining structured water and keeping them in the furnace for about 5 minutes,
When cooled, a homogeneous foamed aluminum alloy composite having a specific gravity of 0.52 was obtained due to the foaming phenomenon. Furthermore, when lucium was not added, many separation phenomena were observed during the mixing of the shirasu balloon.

Example 2 Calcium was added in an amount of 5% based on the weight of the A12-12%51 alloy kept in a molten state at 640°C in a #1O graphite crucible using an electric furnace, and the alloy was thickened.
Short carbon fibers with a length of about 5 mm (diameter 8 μm) were added. About 400 g of the Al-12% Si alloy was coated with the carbon short fiber 40.
9 was possible. The structure after solidification showed a state in which the carbon fibers were relatively well dispersed.

Example 3 Calcium log was added and mixed to 1 kg of Zn-4% Al2 alloy kept in a molten state at 500°C in a #IO graphite crucible in an electric furnace, and after thickening treatment, the particle size was 80
100 g of μm alumina particles were added. An alumina-Zn alloy composite was obtained by adding calcium.

Note that if calcium is not added, a separation phenomenon occurs during the mixing of alumina and a composite cannot be obtained.

Patent applicant: Yukio Iizuka, Director of the Agency of Industrial Science and Technology Designated agent: Kazuo Kobayashi, Director of the Kyushu Industrial Technology Testing Institute, Agency of Industrial Science and Technology

Claims (1)

[Claims] 1 Aluminum alloy, magnesium alloy, tin alloy,
After melting an alloy-calcium mixture of one type of alloy selected from lead alloys and zinc alloys and 0.05 to 5% calcium based on its weight, it is suitable for adding and mixing ceramic particles. A method for producing a ceramic-alloy composite, characterized in that the molten mixture is continuously stirred vigorously in the presence of oxygen to promote oxidation until it reaches viscosity, and then ceramic is added and dispersed.