KR100333310B1 - High-temperature structural intermetallic alloy and its manufacturing method - Google Patents

Abstract

The present invention relates to a composite structured aluminum (Al) -titanium (Ti) -vanadium (V) intermetallic alloy having a low density as a high-temperature structural intermetallic alloy and having a low density. Silver, in atomic%, Ti: 5 to 15%, V: 30 to 40% and the rest is composed of Al, characterized in that it has a two-phase structure of Ti ₅ Al ₁₁ phase and β- (Ti, Al) phase, By dissolving the alloy of the above composition, isothermally heat-treated at a temperature of 800 to 1000 ° C., and then water-cooled to produce a low-density high-temperature structural intermetallic alloy having excellent room temperature ductility.

Description

High-temperature structural intermetallic alloy and its manufacturing method

The present invention relates to a high-temperature structural intermetallic alloy, and more particularly, to a composite structured aluminum (Al) -titanium (Ti) -vanadium (V) intermetallic alloy having low density and excellent in room temperature toughness and a method of manufacturing the same. .

Recently, the importance of the development of high-temperature structural materials has emerged in the aerospace industry. In order to improve high temperature performance, such a high temperature structural material is required to have a low density and a high strength-to-density ratio (specific strength).

Conventional high temperature structural alloys currently applied are heat-resistant alloys mainly composed of nickel (Ni) and have a density of about 8 g / cc.

On the other hand, some have a density about half that of Ni-based heat-resistant alloys, for example, binary Al-Ti intermetallic alloys of Al and Ti.

However, the Al-Ti intermetallic alloy has low density (3.36g / cc), high melting point (1660K), high hardness (about 400HDP) and excellent oxidation resistance, but the production of binary alloy (Al ₃ Ti) It is known to be difficult and extremely vulnerable at room temperature (M. Yamaguchi, Y. Umakoshi and T. Yamane; Philosophical Magazine, A, 55 (1987), 301). That is, the Al ₃ Ti has a regular tetragonal structure (DO ₂₂ ) having a low symmetry, and thus does not provide a sufficient slip system at room temperature deformation.

In order to overcome the room temperature brittleness problem of Al-Ti intermetallic alloys, transition metals such as Cr, Mn, Fe, Ni, and Cu are added to tetragonal Al ₃ Ti as a third element so that the crystal structure is highly symmetric. There have been attempts to secure a sufficient strain gauge when transforming to a cubic structure (L1 ₂ ) (US Pat. Nos. 4,891,184, 5,006,054 and KS Kumar Microstructure and Mechanical Properties of Ternary L1 ₂ Aluminum-Rich Intermetallics, Structural Intermetallics) , TMS, Warrendale, PA, 1993, p. 87).

However, even the ternary cubic alloy prepared in this way does not exhibit the minimum room temperature ductility required as a structural material. For example, according to K.S.Kumar, the toughness at room temperature is almost 0% even in Cr and Mn-added Al-Ti alloys having the best room temperature ductility among the three-base alloys.

Therefore, in the case of Al ₃ Ti alloy, it can be seen that there is a limit in improving room temperature ductility or toughness only by changing the crystal structure.

Meanwhile, the inventors have found that the Ti ₅ Al ₁₁ phase is superior in room temperature toughness to the Al ₃ Ti phase in the Al-Ti alloy system (Korean Patent Application No. 96-70075).

The present inventors are the findings that is not flexible securing at room temperature in the crystal structure, the highest symmetry cubic conditions that exist as a single phase compound between the metal to improve the toughness naejineun room temperature ductility of the weak Al ₃ Ti and Ti ₅ to Al ₁₁ different replaced by Al ₃ adjacent Ti on the basis of a result is excellent the room temperature toughness than the intermetallic compound Al ₃ Ti phase with the superior ductility and toughness Ti ₅ Al ₁₁ phase, base a Ti ₅ Al ₁₁ phase The present invention has been found by forming a composite structure with a β- (Ti, Al) phase, which is a metal phase adjacent to the phase, and producing an intermetallic alloy excellent in low-density room temperature toughness.

That is, the present invention forms a composite structure of Ti ₅ Al ₁₁ phase and β- (Ti, Al) phase having excellent toughness at high temperature by appropriately adding V to the Al-Ti alloy, thereby having low density and excellent room temperature toughness. An object of the present invention is to provide a composite structure type Al-Ti-V ternary intermetallic alloy and a method of manufacturing the same.

1 is a structure photograph of the alloy of the present invention.

In order to achieve the above object, in the present invention, Ti: 5 to 15%, V: 30 to 40%, and the remainder are composed of Al, and the Ti ₅ Al ₁₁ phase and the β- (Ti, Al) phase two-phase structure. It provides an intermetallic alloy for low-density high-temperature structure excellent in room temperature ductility characterized in that it has a.

In the present invention, the alloy is composed of atomic%, Ti: 5 to 15%, V: 30 to 40%, and the remainder of Al, and isothermally heat-treated at a temperature of 800 to 1000 ° C, followed by water cooling. It provides a low density high temperature structural intermetallic alloy excellent in room temperature ductility.

Hereinafter, the present invention will be described in detail with reference to the preferred embodiments.

According to the high temperature equilibrium diagram of the Al-Ti-X (X = transition metal) tertiary alloy reported so far, most transition metals such as Cr, Mn, Fe, Ni, and Cu are added as the third element to the Al ₃ Ti composition. In the Al-Ti-V ternary system, V is preferentially substituted at the Ti atom position, so that the Al ₃ Ti crystal structure does not change.

On the other hand, the inventors of the present invention was confirmed the existence of Ti ₅ Al ₁₁ in the ternary excellent DO ₂₃ form a room temperature toughness compared to the Al ₃ Ti of the DO ₂₂ form a DO ₂₃ crystal structure more similar to the cubic crystal structure compared to DO ₂₂ structure It was confirmed that the Ti ₅ Al ₁₁ phase having excellent room temperature toughness.

In addition, through the appropriate alloy design, it was confirmed that composite alloy alloys with β- (Ti, Al) phases, which are adjacent metal phases based on Ti ₅ Al ₁₁ composition, can be manufactured.

That is, the newly observed intermetallic compound phase Ti ₅ Al ₁₁ and the metal phase β- (Ti, Al) phase form a two-phase region at a high temperature (800 to 1000 ° C).

The present invention is characterized by having a composition corresponding to the ideal region between the Ti ₅ Al ₁₁ phase and the β- (Ti, Al) phase which is a metal phase.

Looking at the composition of the ternary heat-resistant alloy according to the present invention.

This Al-Ti-V ternary alloy is capable of complex organization with β- (Ti, Al) phase having excellent room temperature toughness based on Ti ₅ Al ₁₁ composition, but the final density of the alloy must be considered and Since the fragile intermetallic phase is present together, the components of the constituent elements should be limited to the limited scope of the present invention.

First of all, titanium (Ti) is limited to 5 to 15 atomic%. If less than about 5 atomic%, the Al ₈ V ₅ phase adjacent to Ti ₅ Al ₁₁ is formed, and the alloy becomes brittle, whereas Ti exceeds about 15 atomic%. This is because the Al ₂ Ti phase, which is denser and weaker than ₅ Al ₁₁ , is excessively mixed.

Vanadium (V) is contained in the present invention 30 to 40 atomic%, forming a two-phase structure between the Ti ₅ Al ₁₁ phase and the β- (Ti, Al) phase of the metal phase and the volume of the two constituents by controlling the content of vanadium The fraction is also adjustable. Less than about 30 atomic%, Al ₃ (Ti, V) is more fragile than Ti ₅ Al ₁₁ phase, and the alloy density is higher than 40 atomic% and Al ₂ Ti or TiAl phase is formed, which is undesirable. Limit to%

Since aluminum (Al) is an essential element of the present invention and the lowest specific gravity, it is preferable that the composition of aluminum is as high as possible in order to lower the final density of the alloy, but in this case, the volume fraction of the relatively weak Ti ₅ Al ₁₁ intermetallic compound is The fraction of the high β- (Ti, Al) metal phase, which is excellent in toughness, is relatively low, and it is difficult to expect improvement in toughness by the second phase. Therefore, the aluminum composition determines the content of titanium and vanadium, and then makes the remainder substantially composed of aluminum.

On the other hand, in another method of manufacturing an intermetallic alloy of the composition as described above, the alloy of the composition is dissolved, and isothermally heat-treated after isothermal heat treatment at a temperature of 800 ~ 1000 ℃, the temperature range during isothermal heat treatment is It is limited in the same manner that the heat treatment time for obtaining the target two-phase structure takes a long time in the case of below 800 ℃, the fraction of the β- (Ti, Al) phase of the metal phase is lower than 1000 ℃ and other unwanted phases occur It is therefore limited to the above range.

Of course, before the isothermal heat treatment in the above temperature range, annealing heat treatment is performed for about 100 hours for homogenization of the melted material at about 1250 占 폚.

The intermetallic alloy of the present invention prepared in the above composition range is excellent in room temperature toughness while having a very low density of about 4.0 g / cc.

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

Example 1

A low density intermetallic alloy having a composition as shown in Table 1 below, in which A 1 is a main component, was prepared by arc melting using pure elements. The melted material was subjected to annealing for about 100 hours at about 1250 ° C. for homogenization, and then subjected to isothermal heat treatment at 800 to 1000 ° C. After the isothermal heat treatment, the structure and hardness of the alloy obtained by quenching were measured and the results are shown in Table 1 below.

As shown in Table 1, Comparative Example 1 is composed of an Al ₃ Ti single-phase structure having a weak room temperature ductility, and in Comparative Example 2, an Al ₃ (Ti, V) phase is β- (Ti, Al) as an Al-Ti-V ternary alloy. ) Form phase and two-phase tissue. On the other hand, in the present invention, the Ti ₅ Al ₁₁ phase, which has superior toughness as compared to the Al ₃ (Ti, V) phase, is used as the main phase and constitutes a β- (Ti, Al) phase and a two-phase structure.

The resistance to crack propagation around the diamond pyramid hardness indentation showed that the comparative example 1 had a significant microcracks around the indentation at a load load of 0.5 kg, and the comparative example 2 had cracks around the indentation when the 15 kg load was applied. In the case of the invention example, there was no cracking around the indentation up to 25 kg, the maximum load applied in the present invention.

On the other hand, a microstructure photograph of the alloy of the invention is shown in FIG.

As shown in FIG. 1, the dark phase is a Ti ₅ Al ₁₁ phase and the bright phase is a β- (Ti, Al) phase, and it can be seen that there are two phases to be obtained by the present invention.

Psalm Furtherance Indentation load and crack occurrence Organization Comparative Example 1 Al ₃ Ti 0.5kg crack Al ₃ Ti single phase Comparative Example 2 Al ₆₅ Ti ₁₀ V ₂₅ 15 kg crack Two-phase structure of Al ₃ (Ti, V) phase and β- (Ti, Al) phase Inventive Example Al ₅₅ Ti ₁₀ V ₃₅ 25kg No crack Two-phase structure of Ti ₅ Al ₁₁ phase and β- (Ti, Al) phase

As described above, according to the present invention, by adding V to the Al-Ti alloy properly, a composite structured Al-Ti-V ternary intermetallic alloy excellent in low density and room temperature toughness can be produced, and thus a high temperature structural material is required. The scope of application may be expanded, such as to meet the increasing demands of the aerospace industry.

Claims (2)

Room temperature ductility characterized by atomic%, Ti: 5-15%, V: 30-40% and the remainder being composed of Al and having a two-phase structure of Ti ₅ Al ₁₁ phase and β- (Ti, Al) phase Excellent low density intermetallic alloy for high temperature structure. A method for producing a high-temperature structural intermetallic alloy, in which atomic alloys, Ti: 5 to 15%, V: 30 to 40%, and the remainder of Al are dissolved, and isothermally treated at a temperature of 800 to 1000 ° C. A low density high temperature structural intermetallic alloy having excellent room temperature ductility, characterized by water cooling.