JPS63125651A - Production of high-strength ti alloy member - Google Patents

Abstract

PURPOSE:To develop a high-strength Ti alloy member by subjecting the Ti alloy formed by adding a specific ratio of Mo to a Ti-Al-V alloy which is heretofore generally used to plastic working under specific conditions, and subjecting the alloy further to an aging treatment after cooling. CONSTITUTION:Mo is further added at 0.5-8wt% to the Ti alloy as a structural member for aircraft which contains 2-5wt% Al and 5-12wt% V and is heretofore used generally as the high-strength Ti alloy. The Ti alloy stock is plastically worked to the prescribed temp. in a 650-850 deg.C temp. range and is then cooled with air or forcibly cooled with gas with substantially no dimensional changes and residual strains, by which the two-phase structure of alpha+beta enriched with the beta phase is obtd. Such alloy is subjected to the aging treatment at the prescribed temp. in a 400-600 deg.C range. The high-strength Ti alloy member is produced with simple process without subjecting to a soln. heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing high-strength Ti alloy members that are widely used, for example, as structural members of aircraft.

[Prior Art] Conventionally, the above-mentioned high-strength Ti alloy members generally have a weight percentage of (
Hereinafter, % indicates weight %), M = 2 to 5%, v: 5 to 12%, and the rest is Ti and unavoidable impurities. α+ of enrichment
A member is formed by plastic working at a predetermined temperature within the range of 650 to 850°C exhibiting a β2 phase structure, and on the other hand, the member after this plastic working has an α→-β2 phase structure enriched in the α phase, Even if this material is subjected to aging treatment, no improvement in strength due to α phase precipitation can be expected, so after heating this member to a predetermined temperature within the range of 850 to 900°C, it is subjected to solution treatment by rapid cooling (water cooling). It is manufactured by creating an α + β two-phase structure with β phase enrichment, and finally subjecting this to aging treatment by heating and holding at a predetermined temperature within the range of 400 to 600°C to improve the strength due to α phase precipitation. It is a well-known place.

[Problem that the invention seeks to solve]

However, the above-mentioned conventional manufacturing method for high-strength Ti alloy members requires solution treatment that involves high-temperature heating and rapid cooling, resulting in problems such as dimensional changes in the member and internal strain easily remaining. There is a point.

[Means for solving problems]

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to produce high-strength Ti alloy members without the need for solution treatment, and as a result, they found that an alloy of When Mo is included as a component, not only the solution treatment temperature becomes the same as the plastic working temperature, but also the solution treatment can be performed at a relatively slow cooling rate, that is, with air cooling or forced gas cooling with almost no dimensional change or residual strain. It is now possible to obtain an α+β two-phase structure with the same β-phase enrichment as the microstructure, so air cooling or forced gas cooling is performed after plastic working.
It was discovered that a high-strength T1 alloy member can be obtained by performing aging treatment without subsequent solution treatment.

This invention was made based on the above knowledge, and contains M=2-5%, v: 5-12%, Mo: 0.5-8%, and the rest is Tt and inevitable impurities. A Ti alloy material having a composition of
This method is characterized by a method of manufacturing a high-strength Ti alloy member by aging treatment at a predetermined temperature within the range of 600°C.

Next, in the method for manufacturing a Ti alloy member of the present invention, the reason why the component set, the plastic working temperature, and the aging treatment temperature are limited to the above values will be explained.

A. Component composition (a) M The M component has the effect of improving the heat resistance and oxidation resistance of the member, but if its content is less than 2%, the desired effect cannot be obtained; If the content exceeds 5%, the plastic workability will not only decrease, but also the degree of plastic workability will increase.
%.

(b) v Component has the effect of promoting the formation of the β phase and activating the precipitation of the α phase from the β phase during aging treatment, thereby improving the strength of the member. If the amount is less than 2%, the desired effect cannot be obtained; on the other hand, if the amount exceeds 2%, the β phase becomes clear, and the precipitation of the α phase during aging treatment becomes insufficient, resulting in the desired effect. Since high strength cannot be obtained, its content is set at 5 to 12%.

(c) M.

As mentioned above, the Mo component has the effect of lowering the solution treatment temperature to the plastic working temperature and forming a β phase-enriched α+β two-phase structure, which is the solution treatment structure, at a relatively slow cooling rate. If the content is less than 0.2%, the desired effect cannot be obtained in the above action, while if the content exceeds 8%, the β phase is stabilized and the precipitation of the α phase during aging treatment is significantly suppressed. Since it becomes difficult to secure the desired high strength, the content should be increased from 0.5 to
It was set at 8%.

B. Plastic working temperature If the temperature is lower than 650℃, the structure becomes an α+β two-phase structure enriched with α phase.On the other hand, if the temperature exceeds 850℃, the structure becomes a β-phase structure. is bad,
In particular, since superplastic working cannot be carried out, the temperature was set at 650 to 850°C.

C0 aging treatment temperature If the temperature is lower than 400℃, the precipitation of the α phase from the β phase will be insufficient and the desired high strength cannot be obtained.On the other hand, if the temperature exceeds 600℃, the precipitated α phase will be re-precipitated. The temperature was determined to be 400 to 600°C since it crystallized and the strength could not be improved sufficiently.

〔Example〕

Next, the method for manufacturing a Ti alloy member of the present invention will be specifically explained using examples.

As Ti alloy materials, plates having the composition shown in Table 1 and a plate thickness of 12 mm were prepared, and then using a hot bulging forming device, these plates were processed as shown in Table 1. Plastic working temperature, Ar gas field crab 2.5 atm, strain rate: approx. 2.5 x I Q-2se
Stretch molding is performed under the conditions of c-1, and after this plastic working,
Immediately, the molding device was opened and air-cooled, and subsequently, these plastic processed parts were heated in a vacuum heat treatment furnace at 5 X l 0-
Methods 1 to 9 of the present invention were carried out by aging in a vacuum of 4 torr under the same conditions shown in Table 1 and cooling in a furnace.

In addition, for the purpose of comparison, conventional methods 1 to 5 were performed under the same conditions shown in Table 1 (the solution treatment was performed in a vacuum of 5 X IO""' torr, and water cooling was performed after the treatment). Ta. The 02% yield strength, tensile strength, and elongation of the various members obtained as a result were measured and shown in Table 1.

〔Effect of the invention〕

From the results shown in Table 1, it can be seen that in methods 1 to 9 of the present invention, Ti alloy members obtained by conventional methods 1 to 5, which require solution treatment, were obtained even though solution treatment was not performed. It is clear that it is possible to produce Ti alloy members having the same or greater strength and high elongation.

As described above, according to the method of the present invention, a high-strength Ti alloy member can be manufactured without solution treatment, and the manufactured Ti alloy member has high dimensional accuracy and is resistant to high temperatures. Since solution treatment involving heating and rapid cooling can be omitted, process control is simplified, and industrially useful effects such as cost reduction can be achieved.

Claims (1)

[Scope of Claims] Ti having a composition (wt %) containing Al: 2 to 5%, V: 5 to 12%, Mo: 0.5 to 8%, with the remainder being Ti and unavoidable impurities. After the alloy material is plastically worked at a predetermined temperature within the range of 650 to 850°C, it is immediately air cooled or forced gas cooled, and then aged at a predetermined temperature within the range of 400 to 600°C. A method for manufacturing a high strength Ti alloy member.