JP2749165B2 - TiA-based composite material and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention [relates] is, TiB ₂ in a matrix of TiAl-based intermetallic compound
The present invention relates to a TiAl-based composite material in which particles are dispersed and a method for producing the same.

[Conventional technology]

TiAl-based metal compounds show a positive temperature dependence, in which the strength increases as the temperature rises, and have a very low specific gravity of 3.8, making them highly heat-resistant materials with high specific strength, especially for aircraft engine blades and valves. Research and development for members that move at high speeds at extremely high temperatures is underway.

Conventionally, studies have been made to improve the workability of TiAl-based intermetallic compounds (for example, Ti-34.1% by weight Al-34% by weight V alloy [US Pat. No. 4,294,625], Ti-41.7% by weight Al).
-10 wt% Ag alloy [Japanese Patent Application Laid-Open No. 58-123847], Mn added to TiAl-based intermetallic compound [Japanese Patent Application Laid-Open No. 61-41740], etc.).

On the other hand, utilizing the high specific strength of TiAl-based intermetallic compounds,
There is a need to develop materials with higher strength,
Up to now, there has been almost no study for increasing the strength.

[Problems to be solved by the invention]

An object of the present invention is to provide a TiAl-based composite material having higher strength than a TiAl-based intermetallic compound and a method for producing the same.

[Means for solving the problem]

The object of the invention is to provide, according to the invention, a TiA containing 30 to 40% by weight of Al and 1 to 5% by weight of Cr and the balance substantially consisting of Ti.
This is achieved by a TiAl-based composite material characterized in that 20% by volume or less of TiB ₂ particles are dispersed in a matrix of an l-based intermetallic compound with respect to the volume of the composite material.

According to the present invention, a TiAl-based composite material according to the present invention includes a step of mixing a Ti powder, an Al powder, and a B powder to form a first mixture, and isotropically compressing the first mixture. Forming a compact, heating the compression-molded body in an inert gas atmosphere to dissolve Al in the compression-molded body and self-combustion sintering of Ti and B to form TiB in an Al matrix. ₂ step of forming a sintered body in which particles are dispersed, step of pulverizing the sintered body to form a powdery intermediate material, in a state where the intermediate material, metal Ti, metal Al, and metal Cr are mixed, by heating to a temperature below the melting points of more than TiB ₂ of Ti, and wherein the step of forming a melt comprising a solid TiB ₂ particles, and by casting the melt comprising the step of forming an ingot It can be manufactured by a method.

Hitherto, a TiAl-based intermetallic compound containing 30 to 40% by weight of Al and the balance substantially consisting of Ti has been known as a high-temperature heat-resistant material having high specific strength. The present inventor has used this TiAl-based intermetallic compound as a matrix, in a composite material with TiB ₂ particles of hard dispersed therein, further in the matrix
It has been found that by containing 1 to 5% by weight of Cr, TiB ₂ particles can be finely dispersed, and thereby a composite material having high strength can be obtained. The reason for limiting the Cr content of the matrix in 1 to 5% by weight, the effect to finely disperse the TiB ₂ particles in the matrix becomes significant in the Cr content 1 wt% or more, when the Cr amount exceeds 5 wt% This is because the ductility of the matrix itself is reduced, which causes embrittlement of the entire composite material. However, the amount of the TiB ₂ particles needs to be 20% by volume or less based on the total volume of the composite material. If the amount of the TiB ₂ particles is excessive, the entire composite material becomes brittle and high strength itself cannot be achieved.

In the method for producing a TiAl-based composite material of the present invention, the steps up to the formation of a sintered body use the so-called “XD process” disclosed in US Pat. No. 4,751,048. This method, Ti powder, B powder, and Al powder were mixed by a material obtained by compression molding is heated in an inert atmosphere, allowed to self-combustion sintering of Ti and B in a molten Al and TiB ₂ This is a method of obtaining particles, which is based on TiB ₂ particles formed by sintering.
This is based on the wettability of Al.

In the method of the present invention, the obtained sintered body is pulverized into a powdery intermediate material, and this intermediate material, metal Ti, metal A
l, and melting point of Ti mixed with metallic Cr (1720 ° C)
By heating to a temperature lower than the melting point of TiB ₂ (2900 ° C.), a melt containing solid TiB ₂ particles in a liquid phase is cast and cast.

The TiB ₂ particles contained in the intermediate material exist in a solid state during the melting and casting steps, but undergo a reaction to become coarse or fine as a solid. In the present invention, the presence of Cr in the liquid phase allows the TiB ₂ particles present in the ingot to be finally finely dispersed.

The melting is desirably performed by arc melting or the like in an argon atmosphere that can minimize impurity contamination during melting.

In melting and casting (solidifying) Ti and Al, special considerations are required because their melting points are significantly different from 1720 ° C and 660 ° C. That is, in order to make the matrix composition as uniform as possible, it is desirable to repeat the dissolution and solidification on a water-cooled copper hearth several times.

 Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1] Ti powder, Al powder, and B powder were mixed at a weight ratio of 49.2: 28.6:
The mixture was mixed at 22.2 in a conventional powder mixer to form a mixture.

This mixture was pressurized isotropically with a powder press at a pressure of 29.4 kg / mm ² to obtain a compression molded body.

The compression molded body is heated to 660 ° C in an argon atmosphere,
Ignition was performed at that temperature, and a sintered body was formed by a self-combustion reaction.

The sintered body was pulverized by a ball mill to form a powdery (100 mesh or less) intermediate material.

16.47% intermediate material, 24.53% metal Al, Cr metal
3.60%, the balance of Ti was charged into the arc melting furnace. After by arc melting under an argon atmosphere at the same furnace to form a melt comprising a solid TiB ₂ particles were it allowed to cool solidify on a water-cooled copper hearth in the furnace to obtain an ingot.

Example 2 Ti powder, Al powder, and B powder were mixed at a weight ratio of 49.2: 28.6:
The mixture was mixed at 22.2 in a conventional powder mixer to form a mixture.

Mixing, pressure molding, sintering, and pulverization were performed in the same procedure as in Example 1 to obtain a powdery intermediate material.

By weight, intermediate material 32.94%, metal Al 16.50%, metal Cr
It was charged into an arc melting furnace at a ratio of 2.40% with the balance being Ti, and was melted and cast in the same procedure as in Example 1 to obtain an ingot.

[Comparative Example 1] Ti powder, Al powder, and B powder in a weight ratio of 49.2: 27.6:
The mixture was mixed at 22.2 in a conventional powder mixer to form a mixture.

Mixing, pressure molding, sintering, and pulverization were performed in the same procedure as in Example 1 to obtain a powdery intermediate material.

By weight, intermediate material 19.40%, metal Al 20.20%, balance Ti
, And melted and cast in the same procedure as in Example 1 to obtain an ingot.

Comparative Example 2 A TiAl-based intermetallic compound containing 32.1% by weight of Al and 67.9% by weight of Ti was produced.

High-purity Ti with residual oxygen content of 200ppm or less and Al with 99.99% purity
Was used as a base material to perform melting and solidification in a multipolar arc melting furnace under an argon atmosphere. After emery polishing, a pure copper water-cooled hearth cleaned with acetone was used to minimize the contamination of impurities from the furnace material, and the dissolved Ti was used as a Ti getter to remove unnecessary gas components in the argon atmosphere. . Melting and solidification were repeated several times on a copper hearth, and finally solidified on a copper hearth to obtain an ingot.

For samples collected from the ingots produced in Examples 1 and 2 and Comparative Examples 1 and 2, the matrix composition, TiB ₂ volume ratio,
Table 1 shows the measurement results of hardness and hardness. Comparative Example 2
Is not a composite material but a TiAl-based intermetallic compound simple substance. In Example 2, the hardness of the TiB ₂ particle portion (lower value) is also shown in addition to the matrix hardness (upper value) for reference.

From the results of Table 1, Comparative Example 1 in which TiB ₂ particles were dispersed in a conventional TiAl-based intermetallic compound matrix containing no Cr was used.
Has a considerably higher hardness than that of Comparative Example 2 of TiAl-based intermetallic compound alone, but the level is about HV500.

In contrast, Examples 1 and 2 containing Cr in the matrix according to the present invention have a hardness of around HV600,
The strength was significantly increased.

FIG. 1 and FIG. 2 show the cast structures of the samples of Example 1 and Comparative Example 1, respectively. The TiAl-based composite material of the present invention containing Cr in the matrix is a conventional Cr-free composite material.
TiB ₂ particles as compared with the TiAl-based composite material by (in these figures, white looks patchy surrounded by black outline) are dispersed finely, the hardness of the composite material is significantly enhanced.

〔The invention's effect〕

As described above, according to the present invention, a TiAl-based composite material having significantly higher strength than a TiAl-based intermetallic compound can be obtained.

[Brief description of the drawings]

FIG. 1 contains Cr in a matrix according to the invention
Metallic structure photograph showing the cast structure of TiAl-based composite material (magnification: 5
FIG. 2 is a microstructure photograph (magnification: 50 times) showing a cast structure of a TiAl-based composite material containing no Cr.

Claims (2)

(57) [Claims] In a matrix of a TiAl-based intermetallic compound containing 30 to 40% by weight of Al and 1 to 5% by weight of Cr and the balance substantially consisting of Ti, not more than 20% by volume based on the volume of the composite material.
A TiAl-based composite material having TiB ₂ particles dispersed therein. 2. A step of mixing a Ti powder, an Al powder, and a B powder to form a mixture, a step of isotropically pressing the mixture to form a compression molded body, by heated in an atmosphere to dissolve and Al Ti and B is self-combustion sintering at the compression molded body to form a sintered body TiB ₂ particles are dispersed in the Al matrix, the sintered A step of pulverizing the aggregate to form a powdery intermediate material, heating the intermediate material, metal Ti, metal Al, and metal Cr to a temperature equal to or higher than the melting point of Ti and lower than the melting point of TiB ₂ by forming a melt comprising a solid TiB ₂ particles, and a manufacturing method of TiAl-based composite material according to claim 1, wherein the by casting the melt comprising the step of forming an ingot.