JPH0441629A - Manufacture of rutile crystalline titania whisker reinforced al series composite - Google Patents

Abstract

PURPOSE:To obtain a rutile crystalline titania whisker reinforced Al series composite having high strength by baking the formed body of amorphous hydrat ed titania whiskers bonded by an organic binder into a rutile crystalline one, vanishing the organic binder, thereafter impregnating it with an inorganic binder, executing heating to harden this inorganic binder and impregnating the formed body with the molten metal of a matrix metal by pressurizing. CONSTITUTION:The formed body 16 of amorphous hydrated titania whiskers 10 bonded by polyvinyl alcohol is baked by a heater 18 and is converted into rutile crystalline titania whiskers to vanish the polyvinyl alcohol. This formed body 16' is immersed into a colloidal silica water soln. 20 and is thereafter heated to solidify the silica binder. This formed body 16'' is packed into a case 24, is preheated and is thereafter disposed in the mold 28 of a high pressure casting apparatus 26 as is in the case, to which the molten metal 30 of pure Al is poured, and it is pressurized and is perfectly solidified.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a method for producing a composite material, and more particularly, the present invention relates to a method for producing a composite material, and more specifically, the present invention relates to a method for producing a composite material, and more particularly, to
The present invention relates to a method of manufacturing a composite material using an alloy as a matrix.

[Prior Art] For example, as described in Japanese Patent Application No. 1-115762 jointly filed by the applicant of the present application and another applicant, an aluminum alloy using rutile crystalline titania whiskers as a reinforcing material is disclosed. A composite material having a matrix of A method is described in which, after crystallization and peeling off of crystalline titania whiskers, a molded body of crystalline titania whiskers is formed using an inorganic binder, and a molten matrix metal is impregnated into the molded body under pressure.

[Problems to be Solved by the Invention] However, in the method for manufacturing a composite material described in the specification of the above-mentioned patent application, the whiskers break during the process of loosening the crystallized titania whiskers, resulting in The average fiber length decreases, and therefore the strength of the composite material cannot necessarily be sufficiently improved. Furthermore, if a molded body is formed using an inorganic binder without loosening the crystallized titania whiskers, the agglomerated parts of the whiskers that occur during crystallization tend to become a starting point for failure of the composite material. strength, especially dynamic strength such as fatigue strength, cannot be sufficiently improved.

In addition, in order to solve the above-mentioned problems, for example, by applying the method described in the specification of Japanese Patent Application No. 1-18524 filed by the same applicant as the present applicant, inorganic binders are used. The idea is to form a molded body made of crystalline hydrated titania whiskers, to rutile crystallize the hydrated titania whiskers by firing the molded body, and then to impregnate the molten matrix metal into the molded body under pressure. It will be done.

However, according to the results of experimental research conducted by the inventor of the present application,
If the amount of inorganic binder is relatively large, the amount of residual inorganic binder will also be large, making it impossible to sufficiently improve the strength of the composite material.On the other hand, if the amount of inorganic binder is relatively small, the strength of the composite material cannot be sufficiently improved. It was found that when crystallizing amorphous hydrated titania whiskers, the compact shrinks, making it impossible to produce a composite material with exactly the desired shape and dimensions.

Although the mechanism of compaction shrinkage is not clearly understood,
When amorphous hydrated titania whiskers and an inorganic binder coexist and are heated to high temperatures and crystallized, some kind of interaction occurs between the whiskers and the inorganic binder, resulting in It is assumed that shrinkage of the molded product occurs.

In view of the above-mentioned problems in the conventional method for producing rutile crystalline titania whisker-reinforced Al-based composite materials, the present invention provides a high-strength rutile crystalline titania whisker-reinforced Al-based composite material without shrinkage of the molded product. The aim is to provide a method by which the material can be manufactured.

[Means for Solving the Problems] According to the present invention, the above object is to provide a method for manufacturing a composite material using rutile crystalline titania whiskers as a reinforcing material and Al or an Al alloy as a matrix. A molded body made of bonded amorphous hydrated titania whiskers is formed, and the molded body is fired to crystallize the hydrated titania whiskers, eliminate the organic binder, and add inorganic materials to the molded body. This is achieved by a manufacturing method in which a binder is impregnated, the molded body is heated to harden the inorganic binder, and then a molten matrix metal is impregnated into the molded body under pressure.

[Operation of the invention] According to the present invention, a molded body made of amorphous hydrated titania whiskers bonded with an organic binder is formed, and the hydrated titania whiskers are crystallized into rutile by firing the molded body. At the same time, the organic binder disappears. Therefore, the amorphous hydrated titania whiskers are crystallized in the absence of an inorganic binder, and the shape of the molded body is maintained by the organic binder, so that the amorphous titania whisker is crystallized without any shrinkage of the molded body. Hydrated titania whiskers are crystallized.

Further, according to the present invention, an inorganic binder is impregnated into the molded body after the titania whiskers have been crystallized, and after the inorganic binder is hardened by heating the molded body, a molten metal of the matrix metal is added into the molded body. Pressure impregnated. Therefore, the amount of inorganic binder in the present invention is sufficient as long as it is sufficient to ensure the strength of the molded body when the molten matrix metal is impregnated into the molded body under pressure, and therefore, the amount of inorganic binder remaining in the composite material is sufficient. Since the amount of inorganic binder is also small, a decrease in the strength of the composite material due to a large amount of inorganic binder remaining in the composite material is reliably avoided.

Therefore, according to the present invention, a rutile crystalline titania whisker-reinforced Al-based composite material can be produced without shrinkage of the molded product, and the strength of the composite material can be sufficiently improved.

[Detailed characteristics of the means for solving the problem] The heating temperature and time of the molded body for crystallizing titania whiskers in the method of the present invention are such that the amorphous hydrated titania whiskers can be crystallized into rutile. The temperature and time may be arbitrary, but in order to reliably avoid shrinkage of the molded product, the temperature is preferably 980 to 1080°C and the time is preferably 1 to 5 hours.

In addition, in the method of the present invention, the amount of inorganic binder may be any amount that can ensure the strength of the molded product when crystallizing titania whiskers, but it is necessary to suppress the amount of inorganic binder remaining in the composite material. In order to sufficiently improve the strength of the composite material, the weight of the rutile crystal 'R titania whisker should be
% is preferable.

In addition, in the method of the present invention, the heating temperature and time of the molded body for curing the inorganic binder are preferably set as long as the inorganic binder can be cured, and preferably when the molded body is impregnated with the molten matrix metal under pressure. As long as the inorganic binder can be cured to the extent that the strength of the molded product can be ensured, the temperature and time may be arbitrary, such as 200 to 1080°C for 0.5 to 5 hours. In order to sufficiently harden the molded body and preheat the molded body to allow the molten matrix metal to penetrate well into the molded body,
Temperature and time are 600~1080℃ and 0.5~
It is preferable that the time is 3 hours.

Furthermore, if the volume percentage of amorphous hydrated titania whiskers is small, shrinkage of the molded product is likely to occur during crystallization, and conversely, if the volume percentage of amorphous hydrated titania whiskers is large, The absolute amount of remaining inorganic binder tends to increase. Therefore, the volume percentage of amorphous hydrated titania whiskers in a molded body formed using an organic binder is 20 to 50%.
It is preferable to do so.

Furthermore, the organic binder used in the method of the present invention has a function as a binder that binds individual amorphous hydrated titania whiskers to each other, and when crystallizing the titania whiskers, it is formed by decomposition, combustion, etc. The binder may be made of any organic substance as long as it disappears from the body. Examples of binders that satisfy this condition include polyvinyl alcohol, polyacrylic acid ester, and carboxymethyl cellulose. alcoholic or aqueous solutions are used.

Since the organic binder disappears when the titania whiskers are crystallized, the amount of the organic binder may be such that the shape of the molded body can be maintained when the titania whiskers are crystallized. For example, for amorphous hydrated titania whiskers, It may be 1-20%.

Further, the inorganic binder used in the method of the present invention may be any binder made of a stable inorganic substance that does not decompose even when the molten matrix metal permeates into the compact, such as silica, alumina, etc. It may be zirconia, chromium oxide, cerium oxide, iron oxide, titanium oxide, tin oxide, antimony oxide, or mixtures thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

Example 1 First, as shown in FIG. 1, amorphous hydrated titania whisker 10 (“Tofica T
'', average fiber diameter 1 μm, average fiber length 50 μ■, potassium content 1.4 νt%) were put into a 10% aqueous solution 12 of polyvinyl alcohol (manufactured by Hanui Chemical Co., Ltd.) and mixed until the whiskers were sufficiently defibrated. By stirring the liquid with a propeller 14 and then compression-molding the mixed liquid, amorphous hydrated titania whiskers 10 bonded to each other with polyvinyl alcohol are formed as shown in FIG. The dimensions after drying are 10100X38X16
Eight molded bodies]6 were formed.

Next, as shown in FIG. 3, the molded body 16 is heated to 960 to 100"C (every 20C) for 3 hours in the atmosphere using a heater 18, thereby forming hydrated titania whiskers. was transformed into rutile crystalline titania whiskers and the polyvinyl alcohol disappeared.At this stage, the shrinkage of each molded product was investigated, and it was found that when the heating temperature of the molded product was 980 to 1080°C, the shrinkage of the molded product decreased. There was no shrinkage at all, and the heating temperature was 960℃ and 1
When the temperature was 100°C, some shrinkage occurred in the molded product, but the degree of shrinkage was extremely small. Furthermore, the volume fraction of titania whiskers at this point is about 30%, and the average fiber diameter and average fiber length of titania whiskers are each about 1 μm.
, about 40 μl.

Next, as shown in FIG. 4, each molded body 16' was immersed in an aqueous solution 20 of colloidal silica ("Snowtex SJ" manufactured by Nissan Chemical Co., Ltd.) and taken out from the aqueous solution. As shown in the figure, each molded body 16' was heated to 900° C. in the atmosphere for 2 hours by the heater 18, thereby solidifying the silica binder. The weight ratio was about 3%, and no shrinkage of the molded product was observed at this stage.

Next, as shown in Figure 6, the inner dimension is 38X.
It was formed as described above in a case 24 made of stainless steel (JIS standard 5 US304), which had an opening at one end and a weight 22 integrally provided at the other end. Each molded body 16'' was filled.

Next, after preheating the molded body together with the case to 600° C. for about 20 minutes, the molded body and the case are placed in the mold 28 of the high-pressure casting device 26, as shown in FIG.
A molten metal 30 of pure Al at 0°C is poured, and the molten metal is pressurized at a pressure of approximately 11,000) c/c- by a plunger 32 that fits into the mold, and the pressurized state is maintained until the molten metal completely solidifies. held.

After the molten metal has completely solidified, the solidified body is taken out from the mold 28 using the knockout pin 34, and the solidified body is machined to cut out a composite material made of pure Al reinforced with rutile crystalline titania whiskers. When each composite material was cut and its cross section was examined, no shrinkage of the original molded body occurred in any of the composite materials. When the cross section of each composite material was observed using an optical microscope, it was found that rutile crystalline titania whiskers were uniformly dispersed in each composite material at a volume fraction of about 30%.

Comparative Example 1 A titania whisker identical to the amorphous hydrated titania whisker used in Example 1 above was heated to 1000°C for 2 hours to crystallize rutile, and the morphology of the whisker after fibrillation was determined. Upon investigation, the average fiber diameter and average fiber length of rutile crystalline titania whiskers were approximately 1 μm each.
m, 20 μm, and it was found that the average fiber length of the whiskers was significantly reduced.

Comparative Example 2 The same titania whiskers as the amorphous hydrated titania whiskers used in Example 1 above were put into an aqueous solution of silica sol (Snowtex SJ manufactured by Nissan Chemical Co., Ltd.), and the whiskers were completely removed. After stirring and mixing with a propeller until fibers are broken down, compression molding is performed to 100 x 38 x
Five molded bodies having dimensions of 16 mm were formed. The whisker volume ratio after drying of these molded bodies is approximately 3
0%, and the amount of silica binder was about 3% based on the weight of the whisker. Next, each molded body was heated in the atmosphere for 100 min.
When rutile crystallization was carried out by heating at 0 to 1200°C (50°C increments) for 3 hours, unacceptable shrinkage was observed in all molded bodies.

Example 2 The volume fraction of rutile crystalline titania whiskers was set to 25%, an alumina binder was used as the inorganic binder, and the binder concentration, that is, the amount of alumina relative to the weight of crystalline titania whiskers, was 0 to 10% (1 Eleven molded bodies were formed in the same manner and under the same conditions as in Example 1 above, except for the points set in %). Next, each molded body was heated to 800°C in the atmosphere for 3 hours to fully harden the alumina, and shrinkage occurred in the molded body with a vanida concentration of 0%, but in other cases, shrinkage occurred. No shrinkage occurred in the molded product.

Next, as the molten metal of the matrix metal, A with a hot water temperature of 750°C was used.
A composite material was formed in the same manner and under the same conditions as in Example 1 above, except that l-4vt%Cu-1vt%Si was used. Next, each composite material was subjected to T6 treatment, and then a bending test piece was cut out from each composite material, and a bending test was performed on each test piece. The results are shown in FIG.

From FIG. 8, it can be seen that a composite material having sufficient strength can be obtained even if the concentration of the alumina binder is about 10%, but it is particularly preferable that the concentration of the alumina binder is 1 to 4%.

Similar results were obtained when pure Al was used as the matrix metal. Similar results were also obtained when silica, zirconia, chromium oxide, cerium oxide, iron oxide, titanium oxide, tin oxide, and antimony oxide were used as the inorganic binder.

Example 3 In the same manner as in Example 1 above, nine molded bodies each having a volume fraction of rutile crystalline titania whiskers of 30% and a silica binder concentration of 3% were formed. These molded bodies were then heated in the atmosphere at 520 to 1160°C (in 80°C increments) for 2 hours to sufficiently harden the silica. As a result, some shrinkage occurred in the molded bodies heated at 520°C and 1160°C;
No shrinkage occurred in the molded product at 00 to 1080°C.

Next, as a representative example of a molded product that did not shrink at all,
A molded body heated at a heating temperature of 1050°C is used, and Al-5vt% with a hot water temperature of 750°C is used as the matrix metal molten metal.
Except that a molten metal of Cu-2W t%Mg was used.
A composite material was manufactured in the same manner and under the same conditions as in Example 1 above. Next, after T6 treatment was applied to the composite material, a bending test piece was formed from the composite material, and a bending test was performed on the test piece.
It was recognized that the material had a good strength of "kgf/+om".

Example 4 In the same manner as in Example 1 above, nine molded bodies were prepared in which the volume fraction of crystalline titania whiskers was 10 to 50% (in 5% increments) and the concentration of silica binder was 4%. was formed. Next, each molded body was heated at 850° C. for 2 hours in the atmosphere to sufficiently harden the silica. As a result, some shrinkage occurred in the molded bodies with a titania whisker volume ratio of 10% and 15%, but no shrinkage occurred in the molded bodies with a titania whisker volume ratio of 20 to 50%. It wasn't alive at all.

Next, a molded body having a titania whisker volume ratio of 20 to 50% was used, and a pure Al molten metal with a hot water temperature of 750°C was used as the matrix metal molten metal. Composite materials were manufactured using the same procedure and conditions, and a bending test was conducted on each composite material, and it was found that all composite materials had a good strength of 30 to 45 kgf/mm'. .

Example 5 As an amorphous hydrated titania whisker, an average fiber diameter of 0.
Hydrated titania whisker with 3 μm opening and average fiber length of 10 μm (
Manufactured by Kubota Tekko Co., Ltd., containing potassium, Jitl, 9v,
t%) is used, and the crystallization temperature and time are each 1
A composite material was manufactured in the same manner and under the same conditions as in Example 1 above, except that the temperature was set at 000°C for 2 hours.

As a result, it was confirmed that no shrinkage of the original molded body occurred in this composite material.

Furthermore, even when polyacrylic acid ester or carboxymethyl cellulose was used as the organic binder in each of the above-mentioned Examples, similar results were obtained as in the corresponding Examples.

Although the present invention has been described above in detail with reference to several embodiments, the present invention is not limited to these embodiments, and various other embodiments are possible within the scope of the present invention. It will be clear to those skilled in the art that

[Effects of the Invention] As is clear from the above description, according to the present invention, amorphous hydrated titania whiskers are crystallized in the absence of an inorganic binder, and during crystallization, an organic binder is used to form a molded product. Since the shape is maintained, amorphous hydrated titania whiskers can be crystallized into rutile without shrinkage of the molded product.

Further, according to the present invention, the strength of the molded body after the titania whiskers have been crystallized is ensured by the inorganic binder, and in this state, the molten metal of the matrix metal is impregnated into the molded body under pressure. The amount may be sufficient to ensure the strength of the molded product during composite formation, and this can reduce the amount of inorganic binder remaining in the composite material and improve the strength of the composite material. can.

Further, according to the present invention, it is possible to defibrate the amorphous hydrated titania whiskers before crystallizing them,
Therefore, the decrease in the fiber length of the whiskers is smaller than that in the case where the whiskers after crystallization, which are easily broken, are defibrated, so that the strength of the composite material can also be improved.

Therefore, according to the present invention, it is possible to produce a rutile crystalline titania whisker-reinforced Al-based composite material in a desired shape and size without shrinkage of the molded body, thereby reducing the amount of machining performed on the composite material. It is possible to reduce the amount of heat and improve productivity, and to produce a homogeneous composite material having sufficient strength.

[Brief explanation of drawings]

Figures 1 to 7 are process diagrams showing a series of manufacturing steps in one embodiment of the method for manufacturing a composite material according to the present invention, and Figure 8 shows the relationship between the concentration of alumina binder and the bending strength of the composite material. It is a graph showing the relationship between. 10...Amorphous hydrated titania whisker, 10゛...
・Rutile crystalline titania whisker, 12... Colloidal silica aqueous solution, 14... Propeller, 16.1616
′... Molded body, 18... Heater, 20... Colloidal silica aqueous solution, 22... Weight 124... Case. 26... High pressure casting device, 28... Mold, 30...
Molten metal of pure Al, 32...Plunger, 34...Knockout bottle Patent applicant: Toyota Motor Corporation representative
Patent Attorney Masa Akashi
Tsuyoshi Figure 1 Figure 4 Figure 4 Figure Concentration of alumina binder (%)

Claims (1)

[Claims] Al or A with rutile crystalline titania whisker as reinforcement material
A method for producing a composite material having an alloy as a matrix, in which a molded body made of amorphous hydrated titania whiskers bonded with an organic binder is formed, and the hydrated titania whiskers are produced by firing the molded body. is crystallized into rutile and the organic binder disappears, the molded body is impregnated with an inorganic binder, the molded body is heated to harden the inorganic binder, and then the molten matrix metal is pressurized into the molded body. Manufacturing method of impregnating.