JPH0463237A - High ductility ti-al intermetallic compound - Google Patents

Abstract

PURPOSE:To improve the cold ductility of an intermetallic compound by forming a lamellar structure in which a Ti-Al phase and a Ti3Al phase are alternately precipitated and setting the volumetric fraction of the Ti-Al phase to a specified range. CONSTITUTION:The metallic structure of a Ti-Al intermetallic compound is formed of an aggregate of lamellar structural parts L in which a Ti-Al phase gammaand a Ti3Al phase alpha2 are alternately precipitated. For obtaining this metallic structure, compositionally, the Al content is set to, by atom, 35 to 52%. Or, the metallic structure is formed of a single phase part Sgamma constituted of a Ti-Al phase only and lamellar structural parts L in which a Ti-Al phase gamma and a Ti3Al phase alpha2 are alternately precipitated. For obtaining this metallic compound, compositionally, the Al content is set to, by atom, 45 to 60%. In this way, the Ti-Al intermetallic compound having excellent cold ductility, light in weight and having excellent heat resistance can be obtd.

Description

[Detailed description of the invention] (1) Industrial application fields The present invention relates to highly ductile TiAf-based intermetallic compounds.

(2) Conventional technology TiAl! , type intermetallic compounds are attracting attention as structural materials for engine parts and the like because they are lightweight and have excellent heat resistance.

(3) Problems to be Solved by the Invention However, since the TiAf-based intermetallic compound has a ductile-brittle transition temperature of about 700°C, there is a problem that the room temperature ductility is extremely low.

Therefore, attempts have been made to improve the room temperature ductility of TiAf-based intermetallic compounds by adding a third element (see, for example, Japanese Patent Publication No. 62-215).

The present invention was developed from a different perspective than the conventional ones, namely from the viewpoint of metallographic structure, and TiAf! has improved cold ductility by improving the metallographic structure. The aim is to intermetallic and other intermetallic compounds.

B6 Structure of the Invention (1) Means for Solving the Problems The high ductility TiAf-based intermetallic compound according to the present invention has a metal structure consisting of a layered structure in which a TiAf phase and a T 13 A γ phase are alternately precipitated, The first feature is that the volume fraction αZ (Vf) of the TixAl phase is set to 0.05% or more and 80% or less.

The highly ductile TiAf-based intermetallic compound according to the present invention has a metal structure of TiA/l! A single phase part consisting only of phases and a TiAl
Phase and Ti, Aj! It is composed of a layered structure in which phases are alternately precipitated, and the volume fraction L (Vf) of the layered structure is
The second feature is that the ratio is set to 15% or more.

(2) Effect In the first characteristic, the TiA1 phase is a γ phase and has low room temperature ductility, but when the second phase, the Ti3Al phase (α2 phase), is precipitated in layers alternately with the TiAl3 phase, , TiA
l! , the room temperature ductility of the intermetallic compound is improved.

The volume fraction of Ti:+Af phase α2 (Vf)
is less than 0.05% or more than 80%,
The room temperature ductility of the TiAf-based intermetallic compound decreases.

In the second feature, the second phase TiAf! phase and TfsAIl
When a layered structure portion is mixed with the phase, the room temperature ductility of the entire TiAl-based intermetallic compound is improved due to the presence of the layered structure portion.

However, if the volume fraction L (Vf) of the layered structure portion is less than 15%, the room temperature ductility of the TiAl-based intermetallic compound decreases.

(3) Example FIG. 1 shows TiAff-based intermetallic and other intermetallic compounds 1st TiAj! which is the first example. The metal structure is a layered structure (lamellar structure) in which TiAf phase γ and Ti, Afγ phase 2 are alternately precipitated, and in the illustrated example, the layered structure part It consists of a collection of ri. In order to obtain such a metal structure, Af
It is necessary to set the fi content to 35 atomic %≦ and 11 ≦52 atomic %.

Figure 2 shows the first TiA with an Al content of 47 at%.
j! These are micrographs of the compound, with (a) shown at 50x magnification and Φ) at 400x magnification. In Figure 2, the gray layer is T i A I! Ill,
Moreover, the black layer is Ti and Afγ phase 2, and both phases T and α
It can be seen that 2 is deposited alternately in a layered manner.

Also, the boundaries of each layered structure can be determined from the difference in the growth direction of each layer.

FIG. 3 shows the relationship between the volume fraction α (vB) of the Ti5Aj two-phase α2 and room-temperature elongation in the first TiAl compounds with varying Al contents.

As is clear from the figure, the volume fraction α of the T 13 A f phase α2! By setting (Vf) to 0.05% or more and 80% or less, room temperature elongation of 1% or more is ensured and the first TiA/! The room temperature ductility of the compound can be improved. In this case, Ti5Aj two-phase α.

The volume fraction α, (Vf) is preferably 5% or more, 60
% or less. In addition, the average grain size of the layered structure is lum
As mentioned above, in the range of 1000 μm or less, there is an effect of improving room temperature ductility.

Figure 4 shows the first TiA! with varying Affi content! Ti, A/! in the compound Volume fraction α (vr) of phase α2
and tensile strength.

From the same figure, it is found that in order to secure room temperature elongation and aim for a tensile strength of 300 MPa or more, it is necessary to set the volume fraction α2 (Vf) of the Ti3Al phase α2 to 30% or more and 80% or less. I understand.

In producing the first TiAl-based intermetallic compound, for example, when the A2 content is 47 at%, an ingot is produced by button arc melting of a total of 50 g of raw materials in an argon gas atmosphere, and then the ingot is melted. to the ingot,
A heat treatment method is adopted in which heat treatment is performed by heating at 1100° C. for 110 hours in an argon gas atmosphere, followed by furnace cooling.

FIG. 5 schematically shows the metal structure of the TiAl1-based intermetallic compound (hereinafter referred to as the second TiAl compound) of the second example, and this metal structure is TiAj! Single phase part sr consisting of only phases, TiAf phase T and Ti5AI
! It is composed of a layered structure in which phases α2 are alternately precipitated. In order to obtain such a metal structure, A
2 content, 45 atomic%≦AI! , it is necessary to set it to ≦60 atomic %.

Figure 6 shows the second T with the A/2 content set at 50 at%.
iAi! , is a microscopic photograph of the compound, and (a) of the same figure is 2
00 times, and the figure (b) corresponds to 400 times. In FIG. 6, the gray island-shaped portion is the single-phase portion Sγ, and the gray and black layered portion filling the space between them is the layered structure portion. The boundaries of each layered structure can be determined from the difference in the growth direction of each layer in the layered structure.

FIG. 7 shows the relationship between the volume fraction L (Vf) of the layered structure portion and the elongation at room temperature in the second TiAl compound with varying AI2 content. In the figure, line XI indicates that the volume fraction α, (Vf) of the Ti and Al phases α2 in the layered structure is 0.
In the case of 05%, the line x2 is Ti in the layered structure part.
When the volume fraction αz (vr) of xAf phase α2 is 5%, *xi is Ti in the layered structure part, Af phase α2
When the volume fraction α (Vf) of

As is clear from the line xlxx, an inflection point of room temperature elongation appears at a volume fraction L (Vf) of the layered structure portion of 15%, and therefore, the volume fraction L (Vf) is set to 15% or more. By doing so, the room temperature elongation of the second T i A I compound can be ensured.

When the volume fraction L (Vf) of the layered structure is 35%, the elongation at room temperature is approximately 1.0% on line X, the elongation at room temperature is approximately 1.5% on line X2, and the elongation at room temperature is approximately 2 on line X. %, and this is the first TiAi! whose entire metal structure is composed of layered structures, as shown in FIG. , room temperature elongation, track gap, etc. when the volume fraction αt(Vf) of the T15Al phase in the compound is 0.05% and 5.40%, respectively.

Therefore, the second TiAjl! In a compound, when the volume fraction L (Vf) of the layered structure part is set to 35% or more, the corresponding first TiA/! Room temperature elongation between the compound and the track can be ensured.

In this case, the average grain size of the layered structure is 1 μm or more, 1
In the range of 000 μm or less, there is an effect of improving room temperature ductility.

FIG. 8 shows the relationship between the volume fraction L (Vf) of the layered structure portion and the tensile strength in the second TiAffi compound, in this case Tj in the layered structure portion.

The volume fraction αz (Vf) of the Af phase α2 is 40%, and the change in the volume fraction L (Vf) of the layered structure part is
This was done by varying the f content and heat treatment conditions.

From the figure, it can be seen that when aiming at a tensile strength of 300 MPa or more, it is necessary to set the volume fraction L (Vf) of the layered structure portion to 20% or more.

2nd TiAj! In producing a series intermetallic compound, for example, in the case of 150 at% 142 content, an ingot is produced by button arc melting of a total of 50 g of raw materials in an argon gas atmosphere, and then the ingot is A heat treatment method is adopted in which heat treatment is performed by heating at 1000° C. for 115 minutes in an argon gas atmosphere, followed by air cooling.

C6 Effects of the Invention According to the present invention, by specifying the metal structure as described above, it is possible to provide a T3Affi intermetallic compound metal having excellent room temperature ductility.

[Brief explanation of drawings]

1 to 4 show one embodiment of the present invention, FIG. 1 is an explanatory diagram of the metal structure, FIG. 2 is a micrograph of the metal structure, and FIG. 3 is the volume fraction α2 (vB and FIG. 4 is a graph showing the relationship between the elongation at room temperature and the volume fraction α! (Vf) of the TjsAjl! phase and tensile strength. FIGS. Fig. 5 is an explanatory diagram of the metallographic structure, Fig. 6 is a micrograph of the metallographic structure, Fig. 7 is a graph showing the relationship between the volume fraction L (Vf) of the layered structure part and room temperature elongation, and Fig. 8 is the volume fraction L (V
f): is a graph showing the relationship with tensile strength. α2...T4s A f phase, γ...TjA1 phase, L...layered structure part, sr...single phase part

Claims (2)

[Claims] (1) The metal structure consists of a layered structure in which a TiAl phase and a Ti_3Al phase are alternately precipitated, and the Ti_3Al
Phase volume fraction α_2 (Vf) is 0.05% or more, 80%
A highly ductile TiAl-based intermetallic compound characterized by the following settings. (2) a single phase part whose metal structure consists of only a TiAl phase;
It is composed of a layered structure in which TiAl phase and Ti_3Al phase are alternately precipitated, and the volume fraction L of the layered structure is
A highly ductile TiAl-based intermetallic compound characterized in that (Vf) is set to 15% or more.