JPH0565576A - High toughness ductile TiAl intermetallic compound - Google Patents

Abstract

(57) [Summary] [Object] To provide a TiAl-based intermetallic compound having excellent toughness and ductility. [Structure] Metallographic structure consists of heat treated TiAl phase γ and pro-eutectoid Ti
It is composed of Al phase γ ′. The volume fraction Vf of the pro-eutectoid TiAl phase γ ', which adversely affects the toughness and ductility of the TiAl-based intermetallic compound, is set to 40% or less.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a high toughness ductile TiAl-based intermetallic compound.

[0002]

2. Description of the Related Art TiAl-based intermetallic compounds have been attracting attention as structural materials for engine parts and the like because they are lightweight and have excellent heat resistance.

[0003]

However, the conventional TiAl intermetallic compound has poor workability due to low room temperature ductility, and has poor practicability due to low toughness even when commercialized. There is.

An object of the present invention is to provide the TiAl-based intermetallic compound having improved toughness and ductility by improving the metal structure.

[0005]

The present invention provides a metallographic structure
A TiAl-based intermetallic compound composed of a heat-treated TiAl phase γ and a pro-eutectoid TiAl phase γ ′, wherein the pro-eutectoid TiAl
It is characterized in that the volume fraction Vf of the phase γ'is set to 40% or less.

In the present invention, the metal structure is changed to the matrix phase M.
And its pro-eutectoid TiAl phase γ ′ dispersed in its matrix phase M
And the matrix phase M is heat treated TiAl.
A TiAl-based intermetallic compound having a phase γ and a Ti ₃ Al phase α _2, which is a pro-eutectoid TiA in the entire metallic structure.
It is characterized in that the volume fraction Vf of the l-phase γ'is set to 40% or less, and the volume fraction Vf of the Ti ₃ Al phase α ₂ in the matrix phase M is set to 50% or less.

[0007]

EXAMPLE FIG. 1 shows an example of the metallographic structure of a TiAl-based intermetallic compound.

The metal structure is composed of a matrix phase M and a pro-eutectoid TiAl phase γ'dispersed in the matrix phase M. The matrix phase M has a heat treated TiAl phase γ and a Ti ₃ Al phase α ₂ .

The pro-eutectoid TiAl phase γ'precipitates in the cooling process from the molten state and has a higher Al concentration than the heat-treated TiAl phase γ. Due to this high Al concentration, pro-eutectoid TiA
The l-phase γ'has brittleness and adversely affects the toughness and ductility of the TiAl-based intermetallic compound.

Therefore, the present invention sets the volume fraction Vf of the pro-eutectoid TiAl phase γ'in the entire metallic structure to 40% or less.

In addition, Ti ₃ Al in the matrix phase M
The phase α ₂ correlates with the pro-eutectoid TiAl phase γ ′ and adversely affects the toughness and ductility of the TiAl-based intermetallic compound. On the other hand, heat treatment T
The iAl phase γ has a higher Ti concentration than the pro-eutectoid TiAl phase γ ′, and therefore has tough ductility.

Therefore, the present invention sets the volume fraction Vf of the Ti ₃ Al phase α ₂ in the matrix phase M to 50% or less.

Thus, the pro-eutectoid TiAl phases γ'and T
If both volume fractions Vf of i ₃ Al phase α ₂ are set, TiA
The toughness and ductility of the l-based intermetallic compound can be improved.
However, if the volume fraction Vf of the pro-eutectoid TiAl phase γ'exceeds 40% and the volume fraction Vf of the Ti ₃ Al phase α ₂ exceeds 50%, the ductility of the TiAl-based intermetallic compound decreases.

The metal structure as described above can be obtained by appropriately adjusting the Al content, the addition amount of the third element, the heat treatment conditions and the like.

FIG. 2 shows another example of the metallographic structure of the TiAl intermetallic compound.

The metallic structure is composed of a heat-treated TiAl phase γ and a pro-eutectoid TiAl phase γ '. In this case,
The volume fraction Vf of the iAl phase γ'is set to 40% or less.

By setting the volume fraction Vf of the pro-eutectoid TiAl phase γ'in this way, the toughness and ductility of the TiAl-based intermetallic compound can be improved. However, the pro-eutectoid TiAl phase γ ′
If the volume fraction Vf of the above exceeds 40%, the toughness and ductility of the TiAl-based intermetallic compound decreases.

Next, specific examples of the TiAl-based intermetallic compound will be described.

First, various TiAs are prepared by the following method.
An l-based intermetallic compound was produced.

Ti (sponge titanium) having a purity of 99.7%
And Al with 99.99% purity (aluminum shot)
And were weighed to the target composition to obtain the material. The composition of this material is Ti ₅₃ Al ₄₇ in atomic%. Next, the material was melted in an Ar atmosphere using a non-consumable arc melting furnace to obtain an ingot. Then in the ingot, 100
Heat treatment was performed under vacuum conditions at 0 to 1400 ° C. for 10 to 72 hours to obtain a TiAl-based intermetallic compound.

FIG. 3 (a) is a photomicrograph (500 times) showing the metal structure of a TiAl-based intermetallic compound having a composition of Ti ₅₃ Al ₄₇ (numerical value is atomic%), and FIG. It is a principal part schematic diagram of a).

The volume fraction Vf of the pro-eutectoid TiAl phase γ'in the entire metal structure is 20%, and the volume fraction Vf of the Ti ₃ Al phase α ₂ in the matrix phase M is 10%.

In order to investigate the toughness and ductility of the TiAl intermetallic compound, the following room temperature bending test was conducted.

From the above-mentioned intermetallic compound, length 3 mm, width 4 mm,
A test piece having a length of 37 mm was manufactured, and a 4-point bending test (JIS R 1601) was performed on the test piece. In this test, set the crosshead speed to 0.5 mm / min,
The strain and rolling load by the strain gauge attached to the stretch side of the test piece were measured, and the bending elongation was determined from the measured values.

FIG. 4 shows the volume fraction V of the pro-eutectoid TiAl phase γ '.
The relationship between f and bending elongation is shown.

In the figure, the line a shows that the volume fraction Vf of the Ti ₃ Al phase α ₂ is zero, and therefore the metallographic structure is composed of the heat treated TiAl phase γ and the proeutectoid TiAl phase γ ', as shown in FIG. This is the case. The line b is the line d when the Vf of the Ti ₃ Al phase α ₂ is 30%, and the line c is the line d when the Vf is 50%.
Correspond to the case where the same Vf is 60%. Therefore, as shown in FIGS. 1 and 3, the metallographic structures along the lines b to d are the heat-treated TiAl phase γ, the pro-eutectoid TiAl phase γ ′, and the Ti
₃ Al phase α ₂ and.

As is clear from the line a and the lines b and c,
When the volume fraction Vf of the Ti ₃ Al phase α ₂ is constant, the pro-eutectoid T
When the volume fraction Vf of the iAl phase γ ′ increases, the toughness and ductility of the TiAl-based intermetallic compound decreases, but the Ti ₃ Al phase α ₂
When the volume fraction of Vf is 50% or less (including zero),
By setting the volume fraction Vf of the pro-eutectoid TiAl phase γ'to 40% or less, the toughness and ductility of the TiAl-based intermetallic compound can be improved.

In the case of the line d, since the volume fraction Vf of the Ti ₃ Al phase α ₂ exceeds 50%, the pro-eutectoid TiAl phase γ '
Even if the volume fraction Vf is set to 40% or less, the toughness and ductility of the TiAl-based intermetallic compound cannot be improved.

FIG. 5 shows the volume fraction Vf of the Ti ₃ Al phase α _2.
And the bending elongation.

In the figure, the line f indicates that the volume fraction Vf of the pro-eutectoid TiAl phase γ'is 10%, the line g indicates that the Vf is 40%, and the line h indicates that the Vf is 50%. Applicable to each

As is clear from the lines f and g, the pro-eutectoid TiA
When the volume fraction Vf of the l phase γ ′ is constant, the Ti ₃ Al phase α
_When the volume fraction Vf of ₂ increases, the toughness and ductility of the TiAl-based intermetallic compound decreases, but when the volume fraction Vf of the proeutectoid TiAl phase γ ′ is 40% or less, the volume fraction Vf of the Ti ₃ Al phase α ₂ is Vf. Is set to 50% or less (including zero), the toughness and ductility of the TiAl-based intermetallic compound can be improved.

As is apparent from the line h, when the volume fraction Vf of the pro-eutectoid TiAl phase γ'is 50% or more,
It can be seen that the toughness and ductility of the TiAl-based intermetallic compound does not change even if the volume fraction Vf of the Ti ₃ Al phase α ₂ is changed, and it shows a low value.

In addition to Ti and Al, a third element is used if necessary.

[0034]

According to the present invention, in the metallographic structure, the volume fraction Vf of the pro-eutectoid TiAl phase is specified as described above, or the volume fraction Vf of the pro-eutectoid TiAl phase and the Ti ₃ Al phase is defined as above. By specifying as described above, it is possible to provide a TiAl-based intermetallic compound having excellent toughness and ductility.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a metallographic structure of a TiAl-based intermetallic compound.

FIG. 2 is a schematic view showing another example of the metal structure of a TiAl-based intermetallic compound.

FIG. 3A is a micrograph showing an example of a metallographic structure of a TiAl-based intermetallic compound, and FIG. 3B is a schematic view of a main part of FIG.

FIG. 4 is a graph showing a relationship between volume fraction Vf of proeutectoid TiAl phase γ ′ and bending elongation.

FIG. 5 is a graph showing the relationship between the volume fraction Vf of Ti ₃ Al phase α ₂ and bending elongation.

[Explanation of symbols]

α ₂ Ti ₃ Al phase γ Heat treated TiAl phase γ'Eutectoid TiAl phase M Matrix phase

Claims (2)

[Claims] 1. A TiAl-based intermetallic compound having a metal structure composed of a heat-treated TiAl phase γ and a pro-eutectoid TiAl phase γ ', wherein the volume fraction Vf of the pro-eutectoid TiAl phase γ'is 4
High tough ductility TiAl characterized by being set to 0% or less
Intermetallic compounds. 2. A metallographic structure comprising a matrix phase M and a pro-eutectoid TiAl phase γ'dispersed in the matrix phase M, said matrix phase M comprising TiAl having a heat treated TiAl phase γ and a Ti ₃ Al phase α _2. Is a system-based intermetallic compound and is a pro-eutectoid TiAl phase γ ′ in the entire metallic structure.
Of the Ti ₃ Al phase α ₂ in the matrix phase M is set to 50% or less, and the high toughness ductile TiA is characterized by being set to 50% or less.
l-based intermetallic compound.