JPS61538A - Manufacture of sic whisker reinforced al alloy material - Google Patents

Abstract

PURPOSE:To obtain a homogeneous composite structure free from segregation by preforming SiC whiskers after removing SiO2 from the surface layers and by using the resulting preform as a fibrous skeleton and an Al alloy contg. Mg as a matrix. CONSTITUTION:SiC whiskers are treated plural times with hydrofluoric acid, nitric acid or the like to remove perfectly SiO2 from the surface layers, and the treated SiC whiskers are preformed. The resulting preform is set in a casting mold, and a molten Al alloy contg. Mg is impregnated into the preform and cast under pressure to manufacture an SiC whisker reinforced Al alloy material. Segregation at the inside and outside of the composite material due to the local precipitation of an Mg-Si compound is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing an 81G Wiss force-strengthened Ad alloy material having an Al alloy having a composition containing Mf as a matrix.

[Conventional technology]

81G whiskers have outstanding physical properties in terms of specific strength, specific modulus, heat resistance, and chemical stability, so they are attracting attention as composite reinforcing materials for metals, glass, ceramics, etc. Because it has superior wettability with mulch compared to reinforcing fibers, it is useful for composites using mulch alloys as a matrix.

As a means of manufacturing such a SiC whisker-reinforced Al alloy material, a method using pre-formed BiC whiskers is considered. However, when the pressure casting method is applied using A7 alloy with a composition containing MP in the matrix, segregation of desirable physical properties occurs inside and outside of the resulting composite material, and defects that prevent the formation of a uniform composite structure occur. A phenomenon occurs. This is a unique phenomenon for Al alloy systems containing Mf, and does not occur when pure Al is used as a matrix.

The inventors carefully investigated the above tissue abnormality using X-ray analysis, and found that the cause of this was due to Mg,
We have clarified the fact that 81 compounds are locally precipitated.

When compounding 81G whiskers into a MF alloy matrix by pressure casting, MP-81 compounds tend to precipitate preferentially due to the active action of Mg.
Although it is shown in No. 17421, the phenomenon in which Mf contained in Al alloys is segregated into Mt and Si compounds is not known.

As the Al alloy matrix, an Al alloy for casting or wrought material having a composition containing MP is often used. Therefore, the above-mentioned abnormal segregation phenomenon causes a serious problem in manufacturing the SiC whisker-strengthened Al alloy.

[Problem that the invention seeks to solve]

4 The inventors conducted a multifaceted investigation into the segregation phenomenon of Mt, the 81 compound, and found that it is a SiO2 component present in the surface layer of the 81C whisker, which forms the fiber skeleton. It was found that this was due to the ingredients.

That is, some 81O components adhere to the surface layer of the SiC whisker in the form of an oxide film during heat treatment during manufacturing, and this cannot be easily removed by simple hydrofluoric acid treatment or the like. Segregation of the Mt, 81 compound occurs when the surface layer SiO2 component is present, and the SiO2 component. This does not occur when the is removed. Although the reason for this has not yet been clarified, during the composite process, the slo interposed in the surface layer of the SiC whiskers selectively reacts with the contained Mf acid component in accordance with the penetration of the matrix molten metal, and as MP, 81 It is presumed that the molten Al alloy segregates in the vicinity of the impregnated surface of the molten Al alloy.

The present invention was developed based on the above findings, and Mg
Create a composite structure using an Al alloy containing composition as a matrix! , IfJ! The present invention provides a method for manufacturing a SiC whisker-reinforced M1 alloy material having unusually homogeneous properties.

[Failure to solve the problem]

The structure of the present invention is that the fiber skeleton is made of 81C whisker G7 ohm, which is impregnated with molten metal as an A/gold alloy matrix with a composition containing KMt, and then filled and composited by a pressure casting method. The SiO2 component and components present in the surface layer were removed before renovation.
It is characterized by being composed of 81G whiskers.

SiC whiskers 1-, which form the fiber skeleton, are produced by reacting EIiO and a carbonaceous material such as carbon black at a high temperature in the temperature range of 1400 to 1800°C in an inert atmosphere, and then separating and removing the remaining carbonaceous components. Manufactured by During these steps, SiO2 components are added to the 81C whiskers produced during the high-temperature reaction process. However, if a post-treatment process involving exposure to high-temperature air is involved, some SiO2 components may be present in the surface layer. Components may precipitate as an oxide film. In particular, when adopting a method of separating and removing residual carbonaceous components by incineration treatment, approximately 2 to 5 SiO2 components! Components precipitate out.

In the present invention, the SiO2 component present in the surface layer of these SiC whiskers. It is used after the components have been completely removed.

A method of treatment with hydrofluoric acid/nitric acid or a mixed acid solution such as hydrofluoric acid/nitric acid/sulfuric acid is effective for removing the SiO2 component and ingredients, and complete removal can be achieved by repeating this treatment multiple times.

The 81C whiskers from which the slo present in the surface layer has been removed are dispersed in water or an organic solvent containing an appropriate binder component, filtered with K under normal pressure or pressure, and the remaining wet whisker cake is compressed to a predetermined density. Preform it by a method that allows it to dry.

As the Al alloy having a composition containing Mf as a matrix, Al-based alloys for casting such as AC8A, AC4G, and MuC4D or for wrought materials such as 2618.2024 and 5052.6061 are used. M of these Al alloys
The f content is in the range of 0.2 to 3.0, which is in the Mg content region most suitable for the present invention, but when it comes to Mg alloys with an Mf content exceeding 5, it depends on the SiO2 component. The segregation phenomenon becomes negligibly small, and the adaptation effect of the present invention disappears.

Composite formation is performed using the SiO2 component that is present in the surface layer in advance. After removing the components, a preform of 90iC whiskers is placed in a mold, and A of the composition containing the above-mentioned If up to 5- is placed in the mold.
This process is carried out by pouring a l-alloy matrix, impregnating the inside of the fiber skeleton, and solidifying the matrix while maintaining it under pressure of up to 1000 Kf/.

[For production]

According to the above manufacturing method, the SiO2 component is added to the surface layer of the SiC whiskers that form the fiber skeleton. Since there is no component involved, Mf
, 81 is effectively prevented. At tK, defective phenomena that cause local tissue abnormalities through complex processes are eliminated.

[Example 1] A reaction vessel was filled with a blended raw material of silicon raw material (Sin, fine powder) and carbon material (carbon black), and heated to 1600°C for 4 hours in a heating furnace maintained in a non-oxidizing atmosphere. Hold and SiC
Whiskers were generated by reaction. Then, it was heat-treated at 600° C. in the atmosphere to burn off the remaining carbonaceous components. The 81G whisker thus obtained has a diameter of 0.5-1.5
It was a β-type single crystal with a length Io~5oopm, and a thin oxide film of S10° was closely interposed on its surface layer. On this day, we measured the amount of the 10° component attached, and found that
It was 5.1ch.

This 81C whisker was adjusted to a concentration of 20% WR, 10% nitrogen, and 10% sulfuric acid, added to a 9 mixed acid aqueous solution, and stirred.
After repeating the drying and washing operations five times, it was dried. No component of 1jEIio was detected in the 81G whiskers after treatment.

Through the above processing, S10. The 81C whiskers from which the components have been removed are dispersed in pure water and filtered under pressure to form a warm whisker cake, which is then heated and dried to form a cake with a diameter of 90wn and a thickness of 1.
20tm, vf12 CF) SiC whisker preform was created.

Next, set the preform in the mold, and then
C8A (Mf content 0.8~1.3CH) Al-gold alloy matrix molten metal was injected and heated to 1000K by Granshear.
Pressure casting was performed by applying a pressing force of f/♂.

The cast product was taken out and subjected to T6 treatment to produce a SiC whisker-reinforced M1 alloy material (an example of the present invention).

When the manufactured SiC whisker-reinforced Al alloy material was ring-cut and polished and the center cross section was observed, no segregation phenomenon due to color change was observed.

For comparison, S10. Using SiC whiskers that have not been removed, they are similarly preformed and composited to strengthen EIiC whiskers.
A composite material was produced (comparative example). When the central section of this object was observed, a white abnormal area with a sharp border was clearly observed in the central part [see Figure 2 (1)]. Also,
X-ray analysis (30KV, 20mA FullScale IK) of the outer peripheral part (a) and central abnormality part (b)
cps, integration time 10e), clear peaks of Mg and B1 appeared in the outer peripheral part, but no diffraction lines of Mr and Si compounds other than the 81 line were detected in the central abnormal part.

Next, SiC whisker-reinforced film 1 according to the present invention example and comparative example
The hardness (HRB) of the center cross section of the alloy material was measured, and the results are shown in FIGS. 1 and 2. FIG. 1(2) corresponds to the change in hardness along the A-AZ line of the center cross section having a homogeneous structure appearance according to the example of the present invention shown in FIG. 1(1), and FIG. 2) is shown as a hardness change corresponding to the A-A/ line of the comparative example [FIG. 1(l)] having a central cross-sectional appearance of the central abnormality.

As is clear from comparing Figures 1 and 2, in the case of the example of the present invention, the change in hardness at each measurement point is small and the structure is homogeneous, but in the comparative example, the hardness is extreme at the central abnormality. It is clear that there is segregation in internal and external tissues.

[Example 2] Gold (MW) before and after the same mixed acid aqueous solution treatment as in Example 1
content of 2.2 to 2.8%) was composited as a matrix.

Various physical properties of each SiC whisker-reinforced Al alloy material obtained were measured, and the results are shown in Table I.

Table I The results in Table 1 show that the composite properties of the examples of the present invention are superior to those of the comparative examples, and a significant difference in properties is observed, particularly in yield strength.

[Example 3] S10. SiC whiskers with an intervening amount of 3.9 inches were treated as they were or by the same method as in Example 1 at S10. The removal treatment was performed to form preforms, and 81C Wiss force strengthened Al alloys were manufactured using the preforms as various Al-gold alloy matrices with different Mg contents. The pressure casting method of Example 1 was applied to the composite.

The Mf content and hardness at the center and outer periphery of each EliC whisker-reinforced Al alloy material were measured, and the
A comparison is shown in Table H.

It can be seen that the segregation of composite physical properties is significant in the comparative examples.

〔Effect of the invention〕

As is clear from the above examples, according to the present invention, a stacked structure with homogeneous properties without any segregation abnormalities can be obtained.
81C quis force-reinforced A using Gonoalloy with a versatile Mg-containing composition as a matrix! This will greatly contribute to mass production technology for alloys.

[Brief explanation of drawings]

FIG. 1 shows the outer central cross-section of the SiC whisker-reinforced M1 alloy material manufactured according to the present invention. (1) Toso0A-A
The hardness change along the l line (2nd line is shown).
The figure shows B10. as a comparative example. 111 (1) outside the central cross-section of a SiC whisker-reinforced Al alloy material produced using 81C whiskers with intervening components and hardness change (2) along the Moum' line. a...External use part, b...Central abnormal part Patent applicant: Tokai Carbon Co., Ltd. Representative Patent attorney: Masaya Takahata No. 2

Claims (1)

[Claims] 1. A preform of SiC whiskers has a fiber skeleton,
This is impregnated with a molten Al alloy having a composition containing Mg as a matrix and then filled and composited by pressure casting.The preform that becomes the fiber skeleton is made of SiC whiskers from which the SiO_2 component present in the surface layer has been removed. A method for producing a SiC whisker-reinforced Al alloy material. 2. A method for producing a SiC whisker-reinforced Al alloy material according to claim 1, wherein the matrix is an Al alloy having a composition containing up to 5% Mg.