JPH04235263A - Manufacture of ti-al intermetallic compound-series ti alloy excellent in strength and ductility - Google Patents

Abstract

PURPOSE:To improve the strength and ductility of a Ti-Al intermetallic compound-series Ti alloy. CONSTITUTION:This is a method for manufacturing a Ti-Al intermetallic compound-series Ti alloy excellent in strength and ductility of executing cycle heat treatment of repeatedly subjecting a Ti-Al intermetallic compound Ti alloy contg., by atom, 38 to 45% Al and the balance Ti with inevitable impurities to heat treatment of holding it under heating to a prescribed temp., subjecting it to soln. treatment, successively holding it to a prescribed temp. in an alpha single phase range and thereafter raising its temp. to a prescribed one in a beta single phase range and holding it and a method for manufacturing a Ti-Al intermetallic compound-series Ti alloy excellent in strength and ductility of, after the above cycle heat treatment, furthermore executing alpha soln. treatment of holding it to a prescribed temp. T of 1150 to 1300 deg.C for prescribed time and thereafter executing cooling and then executing aging treatment of holding it to a prescribed temp. in the range of 650 to (T-100) deg.C and thereafter rapidly cooling it.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method for improving the strength and ductility of a TiAl intermetallic compound-based Ti alloy.

0002

[Prior Art] In general, it has been proposed to use TiAl intermetallic compound-based Ti alloys in the production of parts such as turbine blades and automobile turbocharger rotors that require light weight and heat resistance. Among them, Al: 48 It is considered that a Ti alloy containing atomic percent Ti and the remainder consisting of Ti and unavoidable impurities is annealed in a vacuum at a temperature of 1300° C. for three days and then allowed to cool.

[0003] Furthermore, “Japan Institute of Metals Lecture Summary, 236
~237 pages, published September 13, 1989,” includes Al
: 40 atomic % with the remainder consisting of Ti and unavoidable impurities, and a Ti alloy sample containing 40 atomic % Al with the remainder consisting of Ti and unavoidable impurities after homogenization treatment and water cooling. By aging the solution-treated material, α phase (Ti solid solution phase and Ti3Al
It is described that a lamellar structure consisting of a solid solution phase) and a γ phase (TiAl intermetallic compound phase) can be obtained.

0004

[Problems to be Solved by the Invention] However, even if the above-mentioned known heat treatment was performed, the strength and ductility of Ti alloys based on TiAl intermetallic compounds could not be sufficiently improved. This is because the average grain size of the TiAl intermetallic compound Ti alloy subjected to the above heat treatment is as large as 260 μm or more, and the thickness of the striped γ phase in the lamellar structure consisting of α phase and γ phase is thick. It turns out that there is something.

[0005]

[Means for solving the problem] Therefore, the present inventors
From this point of view, the average grain size of the TiAl intermetallic compound Ti alloy is reduced, and the striped γ of the lamellar structure is reduced.
As a result of research to reduce the thickness of the phase, Al: 38 ~
A TiAl intermetallic compound-based Ti alloy containing 45 at. After performing heat treatment to maintain the temperature at a temperature of When the cyclic heat treatment is performed, the grain size of the structure becomes finer and the strength and ductility of the TiAl intermetallic compound Ti alloy is improved.
Predetermined temperature within ~1300℃: T is subjected to α solution treatment by cooling after being held for a predetermined time, and then heated to 650℃ ~ (T-100
) After holding at a predetermined temperature for a predetermined period of time within the range of 100 to 1000 °C, the material is rapidly cooled to reduce the thickness of the striped γ phase in the lamellar structure, further improving the strength and ductility of the TiAl intermetallic compound-based Ti alloy. We obtained the knowledge that it is possible to do so.

[0006] The present invention was made based on this knowledge, and includes (1) a TiAl intermetallic compound-based Ti alloy containing 38 to 45 atomic % Al, with the remainder consisting of Ti and unavoidable impurities; Production of a TiAl intermetallic compound-based Ti alloy with excellent strength and ductility, by heating and holding at a predetermined temperature to perform solution treatment, followed by cycle heat treatment in which α single-phase treatment and β single-phase treatment are repeated. and (2) Al: 38 to 45 at%, the remainder being T.
A TiAl intermetallic compound-based Ti alloy consisting of i and unavoidable impurities is subjected to solution treatment by heating and holding at a predetermined temperature, followed by cyclic heat treatment in which α single-phase treatment and β single-phase treatment are repeated, Further 1150-1300
A predetermined temperature within °C: α solution treatment is performed by holding at T for a predetermined time and then cooling, and then an aging treatment is performed by holding at a predetermined temperature within the range of 650 °C to (T-100) °C for a predetermined time and rapid cooling. This method is characterized by a method for producing a TiAl intermetallic compound-based Ti alloy that has excellent strength and ductility.

In this invention, TiAl intermetallic compound system T
The i-alloy is first heated and held at a predetermined temperature to undergo sufficient solution treatment. However, it is preferable to perform the β solution treatment while maintaining the temperature at a predetermined temperature within the β-phase single-phase temperature range. More preferably, it is temperature. Even if solution treatment is performed at 1300°C or lower, the α phase remains and β solution treatment is not performed.On the other hand,
This is because a high temperature exceeding 1500° C. is undesirable because a liquid phase appears and a non-uniform structure is formed.

After the solution treatment, the temperature is lowered from this temperature to the α-phase single-phase temperature region, α-single-phase treatment is performed to form the α-phase, which is a close-packed hexagonal crystal, and then the temperature is reduced to the β-phase single-phase temperature region again. The temperature is raised, β-single phase processing is performed to obtain the β-phase which is a body-centered cubic crystal, and the α-phase single-phase temperature range → β-phase single-phase temperature range → α-phase single-phase temperature range → β
By carrying out cyclic heat treatment of heating and cooling to maintain a single-phase temperature range, the crystal structure of the TiAl intermetallic compound-based Ti alloy is divided into α phase (close-packed hexagonal crystal) and β phase (
body-centered cubic crystal), thereby making the crystal grains finer.

[0009] The TiAl intermetallic compound-based Ti alloy having a structure having grains refined in this manner is further held at a predetermined temperature: T within the range of 1150 to 1300°C for a predetermined time, and then heated at a rate of 50°C/min or more. If α solution treatment is performed by cooling at a cooling rate, then after holding at a predetermined temperature within the range of 650°C to (T-100)°C for a predetermined time, rapid cooling aging treatment is performed at a cooling rate of 50°C/min or more. , the thickness of the striped γ phase of the lamellar structure becomes even thinner, and the strength and ductility of the TiAl intermetallic compound-based Ti alloy can be further improved.

[0010] If the Al content of the Ti alloy based on TiAl intermetallic compound is less than 38 atomic %, it is not possible to secure a lamellar structure, whereas if it exceeds 45 atomic %, the β phase single phase region will not exist. Unable to carry out the method of the invention. Therefore, the TiA used in the method of this invention
The Al content of the intermetallic Ti alloy is 38 to 45
Defined as atomic percent. This cyclic heat treatment of the TiAl intermetallic compound-based Ti alloy is performed by repeating heating and cooling so as to go back and forth between the α-phase single-phase temperature region and the β-phase single-phase temperature region. The heating rate to the β-phase single-phase temperature region and the cooling rate from the β-phase single-phase temperature region to the α-phase single-phase temperature region are preferably larger, and both are 10°C.
It is more preferable that it is equal to or more than /sec.

Furthermore, the thinning of the γ phase in the lamellar structure of the TiAl intermetallic compound Ti alloy with finer grains occurs at a predetermined temperature: T within the α phase single phase temperature range of 1150 to 1300°C. After being held and subjected to α solution treatment, it was cooled at a cooling rate of 50°C/min or more to 650°C (T-
After cooling to the aging treatment temperature of 100)℃, cooling at a cooling rate of 50℃/min or more reduces the thickness of the γ phase in the lamellar structure to 1.2μm.
It can be thinned to less than

0012

EXAMPLES The present invention will be specifically explained based on examples.

[0013] Molten metals having the compositions shown in Table 1 were prepared in an argon atmosphere using an ordinary arc furnace, and centrifugally cast using a ceramic mold.
A TiAl intermetallic compound-based Ti alloy material (hereinafter referred to as Ti alloy material) having dimensions of 12 mm, width: 12 mm, and length: 70 mm was produced.

[0014]

[Table 1]

After subjecting this Ti alloy material to solution treatment under the conditions shown in Table 1, it was maintained at a temperature within the α-phase single-phase temperature range shown in Table 1 for the time shown in Table 1 to form an α-single phase. Then, the temperature is held within the β-phase single-phase temperature range shown in Table 1 for the time shown in Table 1 to perform β-single-phase processing, and this α-single-phase processing → β-single-phase processing is Methods 1 to 4 of the present invention were repeated for the number of cycles shown in Table 1, and the structure and mechanical properties of the obtained Ti alloy material were measured, and the results are shown in Table 2.

[0016]

[Table 2]

Furthermore, T obtained by the above-mentioned methods 1 to 4 of the present invention
The Ti alloy material was further subjected to lamellar layer refinement treatment under the conditions shown in Table 3, and the methods 5 to 8 of the present invention were carried out.
The structure and mechanical properties of the alloy material were measured and the results are shown in Table 4.

On the other hand, for comparison, Al: 48 atomic %,
A Ti alloy consisting of remaining Ti and unavoidable impurities was held in a vacuum at a temperature of 1300°C for 3 days, and then subjected to air-cooling annealing treatment using the conventional method, and the structure and mechanical properties of the obtained Ti alloy material were measured. The results are shown in Table 4.

[0019]

[Table 3]

[0020]

[Table 4]

[0021]

[Effect of the invention] From the results in Tables 1 and 2, it is clear that the method 1 of the present invention
All of the Ti alloy materials obtained in Tables 3 and 4 have smaller average particle diameters and superior tensile strength and elongation than the Ti alloy materials in Table 4 obtained by conventional methods. From the results, as seen in methods 5 to 8 of the invention, method 1 of the invention
It can be seen that the tensile strength and elongation are further improved by further subjecting the Ti alloy material obtained in 4 to 4 to a lamellar layer refinement treatment.

[0022] Therefore, by using the manufacturing method of the present invention, a TiAl intermetallic compound-based Ti alloy having excellent strength and ductility can be provided, resulting in excellent industrial effects.

Claims (3)

[Claims] [Claim 1] A TiAl intermetallic compound-based Ti alloy containing 38 to 45 at. TiAl with excellent strength and ductility, which is characterized by subjecting it to cyclic heat treatment in which heat treatment is repeated to maintain the temperature at a predetermined temperature within the single-phase temperature range, and heat treatment to raise and maintain the temperature at a predetermined temperature within the β-phase single-phase temperature range. A method for producing an intermetallic Ti alloy. 2. A TiAl intermetallic compound-based Ti alloy containing 38 to 45 at. A cycle heat treatment is performed in which heat treatment is repeated to maintain the temperature at a predetermined temperature within the single-phase temperature range, and heat treatment to raise and maintain the temperature at a predetermined temperature within the β-phase single-phase temperature range, and further to a predetermined temperature within the range of 1150 to 1300°C. : T is subjected to α solution treatment by cooling after holding for a predetermined time, and then 65
A method for producing a TiAl intermetallic compound-based Ti alloy with excellent strength and ductility, which comprises holding at a predetermined temperature in the range of 0° C. to (T-100)° C. for a predetermined time and then subjecting it to an aging treatment of rapid cooling. 3. The solution treatment temperature preferably includes:
3. The method for producing a TiAl intermetallic compound-based Ti alloy with excellent strength and ductility according to claim 1 or 2, characterized in that the temperature is a predetermined temperature of over 1300°C to 1500°C.