JP3324766B2 - Metal matrix composite material and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber-reinforced metal matrix composite, and more particularly, to a reinforcing material having at least an impurity content of 0.3% by weight.
The present invention relates to a metal-based composite material containing the following high-grade potassium hexatitanate whiskers and using a light metal as a matrix.

2. Description of the Related Art In recent years, potassium titanate whiskers have attracted attention as a light metal reinforcing material for general-purpose industrial materials. This is because, while all other ceramic whiskers, which are light metal reinforcing materials, are expensive, potassium titanate whiskers are relatively inexpensive, and the product cost of composite materials reinforced with these whiskers is low, and wide application is expected. That is because On the other hand, the high-pressure casting method is the most excellent production method in view of the properties and cost of the obtained composite material. This is due to the fact that the compounding is completed in a short time and the problem of the reaction between the reinforcing material and the light metal is small, and the advantage that a large-scale manufacturing apparatus is not required.

Conventionally, it has been reported that potassium titanate whiskers react violently with molten aluminum (Hideharu Fukunaga, Tsubun Takeichi, Susumu Ota: Journal of the Japan Society for Composite Materials, 8 (1982), 66). As a potassium titanate whisker in which this problem is solved, a potassium hexatitanate whisker having a tunnel structure having a free potassium content of 5 ppm or less is disclosed. (Publication 1
-301516) The potassium titanate whisker has a significantly reduced content of the layered structure potassium titanate contained in the tunnel structure / potassium hexatitanate whisker. Potassium whiskers have begun to attract attention as light metal reinforcements for general-purpose industrial materials.
(K. Suganuma, T. Fujita, K. Ni
ihara, T .; Okamoto and S.M. Suz
uki: J. Mater. Sci. Letters, 8
(1989), 808) However, the metal matrix composites reinforced with potassium titanate whiskers have better strength properties than previously disclosed light metal matrix composites reinforced with potassium titanate whiskers. However, when heat treatment is performed to improve the mechanical strength and stress corrosion cracking properties of the composite material, the strength decreases,
Also, the problems of the conventional potassium titanate whisker reinforced light alloy, such as the strength not improving, have not been solved. Suganuma et al. Found that when complexing the potassium titanate whisker and the aluminum light alloy, a slight reaction phase mainly composed of magnesium with a thickness of 10 nm or less was formed on the surface of the potassium titanate whisker. It is pointed out that a decrease in the magnesium content in the alloy of the base material leads to a reduction in the strength of the base material. However, they report that this reaction phase does not change particularly in the heat treatment process after complexation, and it is not clear why the strength of the potassium titanate whisker reinforced light alloy is reduced by the heat treatment. there were.

[0004] invention is to be solved problems such as conventional potassium titanate whisker reinforced metal matrix composite material is not preferred as an industrial material has a problem in stability during heat treatment, higher by inexpensive heat treatment intensity It has been desired to develop a novel composite material having excellent heat stability, which can provide a composite material.

The present invention does not have the disadvantages of conventional composites,
An object is to provide a composite material which is inexpensive and has excellent mechanical strength.

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems, and as a result, use high-grade potassium hexatitanate fiber having an impurity content of 0.3% by weight or less as a reinforcing material. Have been found to be effective, and have completed the present invention. That is, the conventional potassium titanate fiber contains impurities such as niobium, phosphorus, aluminum, silicon, iron, and alkaline earth metals derived from the production raw materials, and therefore, the strength of the composite material decreases during heat treatment. And completed the present invention. Conventional potassium titanate whiskers
It is synthesized from anatase-type titanium oxide or metatitanic acid or naturally occurring rutile sand or anatase sand by the sulfuric acid method containing a large amount of the above impurities including niobium, and titanic acid synthesized from these raw materials. Potassium whiskers contained many impurities. That is, the present inventors have found that the decrease in strength during heat treatment of an aluminum alloy reinforced with potassium titanate whiskers is caused by the presence of the impurities, and have completed the present invention.

That is, the present invention provides a fiber-reinforced light metal material using a high-grade potassium hexatitanate whisker having an impurity content of 0.3% by weight or less as a reinforcing material.

Hereinafter, the present invention will be described in detail. The potassium titanate whisker used in the present invention is a high-grade potassium hexatitanate fiber having a tunnel structure with an impurity content of 0.3% by weight or less, and particularly a layered structure potassium titanate or titanium oxide inside or on the surface of the crystal. It is desirable that the single crystal fiber does not contain the different phase. Such a potassium titanate fiber is typically produced by the following method.

That is, the general formula K ₂ O.nTiO ₂ (where n =
A mixture of a titanium raw material compound and a potassium raw material compound blended at the ratios shown in 2-4) at 900-1200 ° C.
To produce massive potassium titanate whiskers, then immerse the massive product in water or hot water to separate the potassium titanate whiskers into single fibers, and then add acid to the slurry to adjust the pH. Is adjusted to 9.3 to 9.7, the composition of the potassium titanate whisker becomes T
iO ₂ / K ₂ O compositionally conversion processing to obtain the composition of 5.9 to 6.00 (molar ratio), 1 further 950 to 1150 ° C.
After heating for more than an hour, acid cleaning may be performed.

In producing the potassium titanate whisker, examples of the titanium raw material compound include hydrated titanium oxide and titanium dioxide having a low impurity content. Examples of the potassium raw material compound include compounds that generate K ₂ O during firing, For example, K ₂ O, KOH, K ₂ CO ₃ and KN
O _{3 and the} like can be mentioned. Among the impurities contained in the raw material compounds, elements forming a water-soluble compound with potassium, such as aluminum, silicon, zinc and phosphorus, after synthesizing bulk potassium titanate whiskers, immerse the bulk in water or hot water It is possible to dissolve some of these impurity elements in water and remove them in the step of separating into single fibers. However, in this case, it is necessary to add the acid after solid-liquid separation to remove the components dissolved in water before adding the acid to the slurry. The content of impurities contained in potassium titanate is desirably 0.3% by weight or less in terms of oxide, and in particular, the content of niobium is desirably 0.1% by weight or less in terms of Nb ₂ O _5. . That is, if the impurity content is larger than the above range, not only does the strength decrease greatly in the heat treatment step after the compounding, but also the reaction with the molten metal becomes strong during the compounding, which is not preferable. The effect is particularly large when an element other than valence four is contained in the crystal structure of the potassium titanate whisker in a solid solution state.
That is, when a valence element other than tetravalent is dissolved in the crystal structure of the potassium titanate whisker, the potassium titanate whisker is easily reduced at the time of complexing with the light metal or at the time of heat treatment after the complexing. For this reason, the strength of the whisker decreases, and the strengthening effect of the potassium titanate whisker decreases. In particular, since niobium is not only included in titanium oxide as an impurity in a large amount but also easily dissolved in the crystal lattice, the strength of the potassium titanate whisker reinforced light alloy when contained in potassium titanate whisker as an impurity is high. Has a large effect.

The light metal used in the present invention is an aluminum light alloy, for example, an Al—Mg type, an Al—Mn type,
Al-Si system, Al-Mg-Si system, Al-Cu system, A
It refers to an l-Cu-Si system, an Al-Cu-Mg-Ni system, or the like, and a commonly used aluminum light alloy is used without any problem. Further, a magnesium-based light alloy can also be used.

As a compounding method of the high-grade potassium hexatitanate whisker and the light metal, a conventionally known method such as a powder metallurgy method and a high-pressure casting method is used.

When preparing a composite material by high-pressure casting, it is necessary to prepare a whisker preform in advance. In this case, a whisker preform produced by adding an inorganic binder is used. It is preferable to use a sintered whisker preform. That is, when an inorganic binder is added to produce a whisker preform, the inorganic binder reacts with potassium titanate whisker to reduce the strength of the potassium titanate whisker. It is difficult to effectively impart the reinforcing effect of the whisker to the light metal, and since the inorganic binder easily reacts with the alloy component, the alloy component may be unevenly distributed or the alloy component may affect the strength of the base material. Problems such as interfering with the formation of intermetallic compounds occur, so that it is difficult to obtain the effect of the heat treatment.

The sintered preform can be manufactured as follows. That is, after adding and mixing an organic binder to a reinforcing material containing potassium titanate whiskers, 800 to 1
When calcined at a temperature of 100 ° C., potassium titanate whiskers are appropriately sintered, and a preform for molten metal casting having good characteristics can be obtained.

The preferred mixing ratio of the high-grade potassium hexatitanate whisker and the light metal is 5 to 40% by volume of the high-grade potassium hexatitanate whisker. That is, when the volume fraction of the high-grade potassium hexatitanate whisker is smaller than 5%, the effect of complex strengthening the matrix metal by the high-grade potassium hexatitanate whisker is very small,
Conversely, the volume ratio of high-grade potassium hexatitanate whiskers is 4
In the range exceeding 0%, not only does the degree of improvement in the strength of the composite material with an increase in the volume ratio of the high-grade potassium hexatitanate whisker decrease, but also as the usage of the high-grade potassium hexatitanate whisker increases. It is not preferable because the cost of the composite material increases. In producing the metal-based composite material according to the present invention, as reinforcing materials, alumina short fibers, crystalline alumina-silica short fibers, silicon carbide whiskers, silicon nitride whiskers, aluminum borate whiskers, alumina long fibers, carbon fibers, silicon carbide fibers And Tyranno fiber can be used in combination. By using the fibers or whiskers in combination, the strength of the high-grade potassium hexatitanate whisker-reinforced metal matrix composite material according to the present invention is further improved, the wear resistance is improved, or the coefficient of thermal expansion is further reduced. Can be done.

Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are provided for illustrative purposes only, and are not intended to limit the scope of the invention.

Example 1 1400 g of high-purity titanium oxide manufactured by Titanium Kogyo Co., Ltd. and 800 g of potassium carbonate were dry-mixed, then placed in an alumina crucible, and heated in an electric furnace at a rate of 200 ° C./hour and a holding temperature of 100 ° C.
After firing under the conditions of 0 ° C. and a holding time of 3 hours, 150 ° C. /
The temperature dropped at the speed of the time.

The fired product was put into 10 liters of warm water in a stainless steel container and immersed for 5 hours. Then, stirring was started at 600 rpm, and the bath temperature was adjusted to 60 ° C. 5N-hydrochloric acid was added dropwise to adjust the pH to 9.5. When the stirring is further continued, the pH rises because potassium ions are eluted from between the layers of potassium tetratitanate, but after the dropwise addition of hydrochloric acid, when the stirring is continued for 30 minutes after the drop of hydrochloric acid, the pH rises to 0.1 or less. Hydrochloric acid was added dropwise at 30 minute intervals to adjust the pH to 9.5.

After filtration, the mixture was calcined at 950 ° C. for 2 hours. After dispersing the fired product in 10 l of warm water, 1N-hydrochloric acid was added dropwise to adjust the pH to 4. After filtration, washing and drying, high-grade potassium hexatitanate whiskers were obtained. When this whisker was identified by X-ray diffraction, it was a single phase having a tunnel structure and potassium hexatitanate. When the whiskers were observed with a scanning electron microscope, the average length was 80 μm and the average diameter was 1 μm.

When the potassium whisker was examined by chemical analysis, it was found that 0.024% of Nb ₂ O ₅ and Fe ₂
O ₃ 0.007%, MgO 0.010%, CaO
0.085%, Al ₂ O ₃ 0.013, ZnO 0.0
_{12%, P 2 O 5 0.009} %, SiO 2 0.006
%, And the purity was 99.8%.

The potassium titanate whiskers are mixed with 150
g / l of water, and 0.1% by weight of a dispersant (manufactured by San Nopco, trade name: Nopco Santo RFA) based on potassium titanate whiskers, and then stirred with a homomixer for 30 minutes. And dispersed. Thereafter, 8.0 wt% of polyvinyl alcohol (Kuraray, trade name: Kuraray Poval 205) was added to the potassium titanate whisker, and the mixture was placed in a PVC mold and suction filtered to obtain a molded product. Was. The suction molded body was transferred from the inside of the PVC mold into the mold, and pressurized so that the whisker volume ratio became 30%. After removing the press-formed body from the mold and drying, 9
It was heated to 50 ° C. to obtain a sintered preform. After pre-heating the sintered preform to about 800 ° C., it is placed in a mold preheated to 350 ° C., and then a melt of US Standard A132 material at about 800 ° C. is poured, and a pressure of 1000 kg / cm ² is immediately applied. The mixture was rapidly cooled and solidified while being added to produce a composite material.

Example 2 In Example 1, the firing temperature after removing a part of potassium from between layers of potassium tetratitanate whisker was 950.
High-grade potassium hexatitanate whiskers were synthesized under the same conditions except that the temperature was changed from 850 ° C. to 850 ° C. The purity of the obtained potassium titanate whisker was the same as in Example 1.

A sintered preform having a whisker volume ratio of 30% was produced in the same manner as in Example 1. After pre-heating the sintered preform to about 800 ° C., it is placed in a mold preheated to 350 ° C., and then a melt of US Standard A132 material at about 800 ° C. is poured, and a pressure of 1000 kg / cm ² is immediately applied. The mixture was rapidly cooled and solidified while being added to produce a composite material.

Comparative Example 1 Anatase type titanium oxide (KA-10) 1 manufactured by Titanium Industry
After dry-mixing 400 g and 800 g of potassium carbonate,
Put into an alumina crucible and heat up at 250 ° C in an electric furnace
After baking at a holding temperature of 1050 ° C. and a holding time of 3 hours, the temperature was lowered at a rate of 200 ° C./hour.

The fired product was put into 10 liters of warm water in a stainless steel container and immersed for 5 hours. Then, stirring was started at 600 rpm, and the bath temperature was adjusted to 60 ° C. 5N-hydrochloric acid was added dropwise to adjust the pH to 9.5. If the stirring is further continued thereafter, potassium ions are eluted from between the layers of potassium titanate, so that the pH increases. However, after stirring for 30 minutes after the dropwise addition of hydrochloric acid, the pH rises to 0.1 or less when stirring is continued for 30 minutes. At a minute interval, hydrochloric acid was added dropwise to adjust the pH to 9.5.

After filtration, the mixture was calcined at 950 ° C. for 2 hours. After dispersing the fired product in 10 l of warm water, 1N-hydrochloric acid was added dropwise to adjust the pH to 4. After filtration, washing and drying, potassium titanate whiskers were obtained. When this whisker was identified by X-ray diffraction, it was a single phase having a tunnel structure and potassium hexatitanate. When the whiskers were observed with a scanning electron microscope, the average length was 80.
μm, and the average diameter was 1 μm.

The potassium titanate whiskers were analyzed by chemical analysis to find that 0.353% of Nb ₂ O ₅ and Fe ₂
O ₃ 0.009%, MgO 0.010%, CaO
0.106%, Al ₂ O ₃ 0.015%, ZnO 0.
012%, P ₂ O ₅ 0.009%, SiO ₂ 0.00
It contained impurities such as 6% and the purity was 99.3%.

A sintered preform having a whisker volume ratio of 30% was produced in the same manner as in Example 1. After pre-heating the sintered preform to about 800 ° C., it is placed in a mold preheated to 350 ° C., and then a melt of US Standard A132 material at about 800 ° C. is poured, and a pressure of 1000 kg / cm ² is immediately applied. The mixture was rapidly cooled and solidified while being added to produce a composite material.

Comparative Example 2 A tunnel structure / potassium hexatitanate whisker was synthesized under the same conditions as in Comparative Example 1 except that an anatase type titanium oxide (KV-200) manufactured by Titanium Industry was used as a titanium raw material. Observation of the whiskers with a scanning electron microscope revealed that the average length was 80 μm and the average diameter was 1 μm
Met. When the potassium titanate whisker was examined by chemical analysis, 0.132% of Nb ₂ O ₅ and Fe ₂ O ₃
0.008%, MgO 0.009%, CaO 0.
101%, Al ₂ O ₃ 0.014%, ZnO 0.01
_{0%, P 2 O 5 0.010} %, SiO 2 0.007%
And the purity was 99.6%. A sinter preform having a whisker volume ratio of 30% was produced in the same manner as in Example 1. After pre-heating the sintered pre-formed body to about 800 ° C., and then setting the pre-heated mold at 350 ° C.,
A molten material of American standard A132 material at about 800 ° C. was poured and immediately cooled and solidified while applying a pressure of 1000 kg / cm ² to produce a composite material.

Reference Example 1 Potassium titanate whisker HT-300 manufactured by Titanium Kogyo Co., Ltd.
(Purity: 99.3%), water was added to a concentration of 150 g / l, and 0.1% by weight of a dispersant (manufactured by San Nopco, trade name: Nopco Santo RFA) was added to the potassium titanate whisker. Thereafter, the mixture was dispersed by stirring with a homomixer for 30 minutes. Thereafter, 8.0 wt% of polyvinyl alcohol (Kuraray, trade name: Kuraray Poval 205) was added to the potassium titanate whisker, and the mixture was placed in a PVC mold and suction filtered to obtain a molded product. Was.
The suction molded body was transferred from the inside of the PVC mold into the mold, and pressurized so that the whisker volume ratio became 30%. The press-formed body was taken out of the mold, dried and heated to 950 ° C. to obtain a sintered pre-formed body.

After pre-heating the sintered pre-formed body to about 800 ° C., it is placed in a mold previously heated to 350 ° C.
Pour the melt of US standard A132 material at 100 ° C and immediately
The composite material was rapidly cooled and solidified while applying a pressure of 0 kg / cm ² to produce a composite material.

Reference Example 2 A sintered preform was obtained under the same conditions as in Reference Example 1 except that potassium titanate whisker Tismo N manufactured by Otsuka Chemical Co., Ltd. was used. The potassium titanate whiskers were analyzed by chemical analysis to find that 0.120% of Nb ₂ O ₅ and Fe ₂ O ₃
0.010%, MgO 0.027%, CaO 0.1
11%, Al ₂ O ₃ 0.062%, ZnO 0.001
%, Impurities such as P ₂ O ₅ 0.089% and SiO ₂ 0.005%, and the purity was 99.5%.

After pre-heating the sintered preform to about 800 ° C., it is placed in a mold which has been preheated to 350 ° C.
Pour the melt of US standard A132 material at 100 ° C and immediately
The composite material was rapidly cooled and solidified while applying a pressure of 0 kg / cm ² to produce a composite material.

Reference Example 3 A sintered preform was obtained under the same conditions as in Reference Example 1 except that potassium titanate whisker Tofica Y manufactured by Nihon Whisker was used. When the potassium titanate whisker was examined by chemical analysis, it was found that 0.222% of Nb ₂ O ₅ and Fe
1.487% ₂ O ₃ , 0.008% NiO, MnO
0.034%, MgO 0.073%, CaO 0.0
53%, Al ₂ O ₃ 0.276%, ZnO 0.011
%, Impurities such as P ₂ O ₅ 0.131% and SiO ₂ 0.680%, and the purity was 96.8%.

After preheating the sintered preform to about 800 ° C., it is placed in a mold previously heated to 350 ° C.
Pour the melt of US standard A132 material at 100 ° C and immediately
The composite material was rapidly cooled and solidified while applying a pressure of 0 kg / cm ² to produce a composite material.

The composite materials obtained in Examples 1 and 2, Comparative Examples 1 and 2, Reference Examples 1, 2 and 3 were machined to produce tensile test pieces. FIG. 1 shows a test piece shape for a tensile test. Before heat treatment and T71 heat treatment (525 ° C. × 16
After quenching in water after a solution treatment for a period of time, a room temperature tensile strength after tempering at 188 ° C. for 5 hours) was measured. The test results are shown in Table 1.

[0037] As is clear from Table 1, the high-grade hexatitanium according to the present invention
Potassium whisker reinforced composite material is strengthened by heat treatment
While Comparative Examples 1 and 2 and Reference Examples 1 to
The strength of the composite material of item 3 is significantly reduced by heat treatment.
You.

Example 3 Using the high-grade potassium hexatitanate whisker obtained in Example 1, a sintered preform having a whisker volume ratio of 16% was obtained in the same manner as in Example 1.

After pre-heating the sintered preform to about 800 ° C., it is placed in a mold which has been pre-heated to 350 ° C.
Pour molten metal of JIS standard AC8A
The composite material was rapidly cooled and solidified while applying a pressure of 0 kg / cm ² to produce a composite material.

Comparative Example 3 Using the potassium titanate whisker obtained in Comparative Example 1, a sintered preform having a whisker volume ratio of 16% was obtained in the same manner as in Example 1.

After pre-heating the sintered pre-formed body to about 800 ° C., the pre-sintered body was placed in a mold previously heated to 350 ° C., and then heated to about 800 ° C.
Pour molten metal of JIS standard AC8A
It rapidly cools and solidifies while applying a pressure of kg / cm ² ,
A composite material was manufactured.

The composite material obtained in Example 3 and Comparative Example 3 was machined to produce a tensile test piece similar to that shown in FIG.

Before heat treatment and T6 heat treatment (510 ° C.)
After quenching in water after solution treatment for 4 hours, 170 ° C × 1
The room-temperature tensile strength after 0-hour tempering treatment) was measured. The test results are shown in Table 2.

[0044] Example 4 Using the high-grade potassium hexatitanate whiskers obtained in Example 1, a sintered preform having a whisker volume ratio of 25% was obtained in the same manner as in Example 1.

After pre-heating the sintered preformed body to about 800 ° C., it was placed in a mold previously heated to 400 ° C., and then heated to about 770
Pour molten metal of JIS standard AC4C
The composite material was rapidly cooled and solidified while applying a pressure of 0 kg / cm ² to produce a composite material.

Comparative Example 4 Using the potassium titanate whiskers obtained in Comparative Example 2, a sintered preform having a whisker volume ratio of 25% was obtained in the same manner as in Example 1.

After pre-heating the sintered pre-formed body to about 800 ° C., it is placed in a mold which has been pre-heated to 400 ° C., and then heated to about 770
Pour molten metal of JIS standard AC4C
The composite material was rapidly cooled and solidified while applying a pressure of 0 kg / cm ² to produce a composite material.

The composite material obtained in Example 4 and Comparative Example 4 was machined to produce a tensile test piece similar to that shown in FIG.
Before heat treatment and after T61 heat treatment (525 ° C. × 8 hours solution heat treatment followed by rapid cooling in water 17
Room temperature tensile strength after tempering treatment at 0 ° C. × 7 hours) was measured. Table 3 shows the test results.

[0049]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a shape of a tensile test piece.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C22C 49/12 C22C 49/12 C30B 29/62 C30B 29 / 62F // C22C 101: 02 C22C 101: 02 (56) References JP-A-62-240727 (JP, A) JP-A-3-82725 (JP, A) JP-A-64-73031 (JP, A) JP-A-5-899 (JP, A) JP-A-5-898 (JP, A) JP-B 3-38239 (JP, B2) JP-B 1-59214 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 47/00-49 / 14 C30B 1/00-35/00 C08K 3/22 C08K 7/04

Claims (4)

(57) [Claims] 1. A metal-based composite material comprising a high-grade potassium hexatitanate whisker having a tunnel structure with an impurity content of 0.3% by weight or less in terms of oxide and a light metal. 2. The composition according to claim 1, wherein the content of impurities is 0.3% by weight or less in terms of oxides , and the content of niobium as impurities is Nb.
And high-grade potassium hexatitanate whiskers having ₂ O ₅ converted at 0.1 wt% or less tunnel structure, or a light metal
Ranaru metal matrix composite material. 3. A high-quality potassium hexatitanate whisker having a tunnel structure and having a content of impurities of 0.3% by weight or less in terms of oxide when producing a composite material by a high-pressure casting method. The method for producing a metal-based composite material according to claim 1, wherein 4. When producing a composite material by a high-pressure casting method, the content of impurities is 0.3% by weight or less in terms of oxides , and the content of niobium as impurities is 0.1% in terms of Nb ₂ O ₅ . The method for producing a metal-based composite material according to claim 2, wherein a high-grade potassium hexatitanate whisker having a tunnel structure, which is 1% by weight or less, is used.