JPH01184242A - Titanium alloy having excellent ductility - Google Patents

Abstract

PURPOSE:To improve the ductility of the title alloy and to permit the press formability of the plate material at the ordinary temp. by specifying V, Al, Zr, Sn and Ti. CONSTITUTION:The Ti alloy is formed with the compsn. consisting of, by weight, 16-20% V and one or more kinds among <=2% Al, <=6% Zr and 6% Sn and the balance constituted of Ti. The above Ti alloy stably shows excellent ductility and the press forming of the plate material at the ordinary temp. can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a titanium alloy with excellent ductility that can be formed at room temperature.

<Background technology> The characteristics of titanium, such as its excellent specific strength, corrosion resistance, and heat resistance, have attracted attention, and many titanium alloys have been developed to date. The current situation is that it is limited to an extremely limited field.

The reason why the demand for titanium alloys has been slow to expand is that titanium alloys are generally expensive, but they also have very poor ductility and cannot be formed into sheet materials at room temperature by press forming, etc. The following points can be mentioned.

For example, Ti-6pJL, the most common titanium alloy
-4V alloy has an elongation of only about 10% at room temperature,
Therefore, it was completely impossible to form a Ti-6AR-4V alloy plate material at room temperature.

Furthermore, Ti-1, which was recently developed with the main purpose of improving ductility,
5V-3AI-3Sn-3Cr alloy (β-type titanium alloy)
Even so, the elongation at room temperature was only about 20%, and it had to be said that the ductility was insufficient to be used for molding at room temperature.

<Means for Solving the Problems> Therefore, in order to provide a titanium alloy that exhibits excellent ductility and can be formed into a sheet material at room temperature, the present inventors particularly focused on Among titanium alloys, which are classified into three types: α type, which has a body-centered cubic crystal structure, β type, which has a body-centered cubic crystal structure, and α/β type, which has a mixed two-phase crystal structure, β type has ductility at room temperature for boat fishing. Focusing on the fact that
In search of the possibility of further improving the ductility of this β-type titanium alloy, we investigated its plastic deformation behavior in detail and found that [the ductility of β-type titanium alloy is closely related to the stability of the β phase;
After making the phase metastable, appropriate amounts of Al and Z are added to it.
When one or more types of r and Sn are added, so-called "transformation-induced plasticity (TRIP)" accompanied by martensitic transformation appears when this alloy is compositionally deformed, and it appears to exhibit significantly improved ductility. We obtained the knowledge that ``it becomes ``.

This invention was made based on the above knowledge, and includes a titanium alloy containing 7216 to 20% (hereinafter, the percentage indicating the component ratio is expressed as weight%), and further AI! : 2% or less.

Zr: 6% or less.

It is characterized by having extremely excellent ductility by configuring the composition to include one or more of Sn: 6% or less, and the remainder being substantially Tj.

Next, the reason why the composition of the alloy is limited as described above in this invention will be explained.

(a+ V The ■ component has the effect of stabilizing the β phase, and its content is very important in keeping the β phase in a metastable state. In other words, if the ■ content is less than 16%, the alloy structure is β at room temperature
It does not form a single phase, and therefore, sufficient ductility cannot be imparted to the titanium alloy. On the other hand, if the content exceeds 20%, the β phase becomes too stable, deformation-induced martensitic transformation no longer occurs, and ductility deteriorates as well. Therefore, the content was limited to 16-20% = 3-.

(b) 8fl, Zr, and Sn These components have the effect of further improving the ductility of the β-type titanium alloy whose content has been adjusted even when added in small amounts, and in order to ensure sufficient ductility at room temperature. Although it is essential to add one or more types of these, the reason for limiting the content will be explained for each individual component below.

Ap has an important function of causing transformation-induced plasticity (TRIP) to appear by suppressing the precipitation of the ω phase that inhibits deformation-induced martensitic transformation. However, if the M content exceeds 2%, the shear resistance during martensitic transformation increases, and conversely, deformation-induced martensitic transformation is suppressed and ductility decreases, so the upper limit of the M content was set at 2%.

In addition, in the case of single addition, it is preferable to ensure an addition amount of 1% or more.

and Sn have the same effect as Al, but in the case of Sn, 6
If you add more than 8%! The upper limit of the Sn content was set at 6% because the same disadvantages as in the above occur and the ductility decreases. In addition, when Sn is added alone, it is preferable to ensure an addition amount of 4% or more.

Zr also has the same effect as AN, but its ω phase precipitation suppressing effect is not as great as that of Al and Sn. Therefore, it is particularly recommended to add it in combination with octaβ and Sn. When Ap and Sn are added in combination, the amount of deformation-induced martensite is adjusted appropriately and the ductility of the alloy is effectively increased. However, if the Zr content exceeds 6%, the same problems as those of 8β and Sn will occur and the ductility will decrease, so the upper limit of the Zr content was set at 6%. Note that even when Zr is added, it is desirable to ensure an addition amount of 4% or more if possible.

<Function> The titanium alloy of the present invention is constructed as described above, and the reason why this titanium alloy exhibits extremely excellent ductility is considered to be due to the following reason.

That is, as mentioned earlier, by containing an appropriate amount of
The phase is made metastable, and an appropriate amount of sn, AI! +Z
When a β-type titanium alloy made by adding one or more types of r is plastically deformed, the β phase is in a metastable state and Sn, AI! , Suppression of ω phase precipitation possessed by Zr.

Depending on the production use, it exhibits transformation-induced plasticity (TRIP) accompanied by martensitic transformation during plastic deformation. Therefore, the ductility of the alloy is improved to such an extent that the titanium alloy plate material can be press-formed at room temperature.

Next, the present invention will be specifically explained using examples and comparing with comparative examples.

<Example> Titanium alloys having various compositions as shown in Table 1 were melted by argon arc melting, and the obtained ingots were hot-rolled and cold-rolled to produce plates of IB thickness.

Next, each of these titanium plates was subjected to solution treatment, and tensile test pieces were cut out, and mechanical properties were measured by a tensile test at room temperature.

These test results are also shown in Table 1.

As is clear from the results in Table 1, the titanium alloy according to the present invention exhibits an extremely excellent elongation value and can be press-formed at room temperature.

<Summary of Effects> As described above, the present invention has extremely useful effects industrially, such as being able to provide a titanium alloy that stably exhibits excellent ductility and can be press-formed into plate materials at room temperature. is brought about.

Applicant: Nippon Stainless Co., Ltd.

Claims (1)

[Claims] Contains 16 to 2.0% V by weight, and
A titanium alloy with excellent ductility, which further contains one or more of the following: Al: 2% or less, Zr: 6% or less, and Sn: 6% or less, with the remainder substantially consisting of Ti.