JPS62205253A - Heat treatment for ti-8al-1mo-1v alloy - Google Patents

Abstract

PURPOSE:To improve creep-resisting characteristics by subjecting a Ti-8Al-1Mo-1 V alloy to solution heat treatment at a temp. lower than the beta-transition point by a specific temp., to cooling, and then to ageing treatment. CONSTITUTION:The Ti-8Al-1Mo-1V alloy consisting, e.g., of, by weight, 7.35-8.35% Al, 0.75-1.25% Mo, 0.75-1.25% V, and the balance Ti is subjected to solution heat treatment at a temp. lower than the beta-transformation point by 5-19 deg.C, 1,030-1,050 deg.C, and then to cooling by water cooling or oil cooling, followed by ageing treatment. In this way, the quantity of pro-eutectoid alpha is reduced and the microstructure after ageing enters into acicular region having superior creep characteristics.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to Ti-8A! The present invention relates to a heat treatment method for L-1Mo-1V gold alloy.

[Prior art] Ti-8Al-IMo-IV alloy has poor hot workability, but it has the lowest density among titanium alloys and a high elastic modulus, making it suitable for use in disks and blades of some jet engine compressors. It is used in

The disks and blades of some jet engine compressors are exposed to high temperatures for long periods of time, and therefore require excellent mechanical properties, particularly strength, creep resistance, and toughness.

Incidentally, the Ti-8ATi-8AJl-I alloy is often used as a solution aged material.

Conventionally, the heat treatment method for Ti-8ATi-8A1-I alloy is as follows: 1. After solution treatment for 1 hour at 980°C ~ (19°C lower than the β transformation point), oil cooling (OQ) or water cooling (WQ) is performed, and then Method of aging ■980℃~1010℃
Solution treatment for 1 hour at 899°C to 927°C, followed by air cooling (AC) or faster cooling, followed by aging treatment. These methods are stipulated by AMS (AMS 4972C stipulates bars, etc., and AMS 4973C stipulates forged products, etc.).

Materials heat-treated by this conventional method have the following leap characteristics.

Holding temperature 454℃ Creep load 28.1kgf/mm' Holding time
28-hour creep deformation amount: 0.085% or more [Problem to be solved by the invention] In recent years, the gas temperature of jet engines has been increased with the aim of increasing the output and thermal efficiency of jet engines. To withstand high temperatures, T 1-8AjL
-1Mo-1V gold alloys are required to have higher creep resistance.

However, attempts to improve creep resistance lead to a decrease in other mechanical properties such as tensile properties and toughness.

Therefore, there has been a desire for a heat treatment method that can improve creep resistance without deteriorating other mechanical properties such as tensile properties and toughness.

[Means for solving the problem] The above problem is as follows: T i -8AM -1Mo -I
The problem is solved by a Ti-8A-1Mo-1V gold alloy heat treatment method, which is characterized in that the V alloy is solution-treated at a temperature 5 to 19° C. lower than the β-transformation point, then cooled, and then subjected to an aging treatment.

In the present invention, Ti-8A cross-I Mo-IV
As the alloy, for example, those specified by AMS etc. are applicable.

For example, at 1% by weight, it has the following chemical components: A-monia, 35-8.35 M o = 0, 75-1.25 V: 0.75-1.25 Ti: the balance. Of course, the above components also include those containing impurities or selectively added elements.

In addition, the processing method is not limited, that is, forged products,
Cast products are also covered.

In the present invention, solution treatment is performed at a temperature 5 to 19° C. lower than the β transformation point.

Here, the β transformation point varies depending on the chemical composition, but for example, in the case of an alloy having the above composition, it is 1030 to 1050°C.

The reason why the solution treatment is performed at a temperature 5 to 19° C. lower than the β transformation point is as follows.

First, if solution treatment is performed at a temperature 5° C. lower than the β-transform point or higher, the tensile properties will deteriorate, as shown in FIG. 2 (the right side of the shaded area in FIG. 2). Especially yield strength (0.2%ys), area of area (RA), elongation (EQ
) decreases rapidly. Furthermore, if solution treatment is performed at a temperature lower than 19°C below the β-transform point, there is no decrease in tensile properties, but as shown in Figure 1 (the left side of the shaded area in Figure t51), the amount of creep deformation increases. It gets bigger.

There are no particular limitations on the retention time for solution treatment and the cooling rate after retention, but for example, AMS4972C54973
Hold for 1 hour and air cool (AMS) as specified in G.
4972G), water-cooled or oil-cooled (AMS 4973'C)
do it.

The leave characteristics are further improved.

Conditions for aging treatment may be selected as appropriate; for example, AM
54972G, 56 as specified in 4973C.
What is necessary is just to hold|maintain at 5-595 degreeC for 8 hours or more, and to air-cool.

[Function] When the solution temperature is set to a temperature 5 to 19° C. lower than the β transformation point, the amount of pro-eutectoid α decreases, and the microstructure after aging becomes an acicular desired region with good creep properties.

On the other hand, the tensile properties in the present invention are insensitive to the solution temperature below the β transformation point, and there is almost no effect even if the solution temperature is raised to a temperature 5° C. above the β transformation point.

[Example of the Invention] Rolled round bars of φ13 mm and φ22 m were manufactured using a Bθ square billet from a 1 ton ingot of φ480 mm.

The main chemical composition of this round bar is Ti-8A-1Mo-1
7.77%AfL as V alloy.

1.00%Mo, L, l 2%V, 0.0
93% Fe, 00% 0, β transformation point is 1037
The samples thus prepared were subjected to aging treatment by solution treatment at various solution treatment temperatures for 1 hour, water cooling at 0°C, then holding at 593°C for 8 hours, and air cooling.

The following characteristics of the sample thus prepared were tested.

(#Creep property) Creep was conducted under the following test conditions.

Holding temperature 454°C Creep addition ffi 28.1 kgf/mrn' Holding time 23 hours The test results are shown in Figure 1. The shaded area in Figure 1 is the range of the embodiment of the present invention, and the area to the left of the shaded area is The part is a conventional example. Note that the one-dot line indicates the β-transformation point.

While the conventional example shows a creep deformation amount of 0.085% or more, the amount of creep deformation in the example range is 0.05%.
It shows a good leap deformation amount of ~0.08%.

(Tensile properties) Tensile properties were investigated by a tensile test at room temperature. The results are shown in FIG. 2. The shaded area in FIG. 2 is within the scope of the embodiment of the present invention.

The portion to the left of the diagonal line is the conventional example. Note that the dotted line indicates the β-transformation point.

It can be seen that the tensile properties of the examples are the same as those of the conventional examples.

However, the tensile properties rapidly decrease in a temperature range higher than 5° C. below the β-transform point.

(Fracture Toughness) Fracture toughness was evaluated based on the values standardized by ASTM.

The values in the example were almost the same as those in the conventional example.

[Effects of the Invention] As explained above, since the present invention is configured as described above, the creep resistance can be significantly improved without reducing mechanical properties such as tensile properties and fracture toughness.

[Brief explanation of drawings]

FIG. 1 is a graph showing the amount of creep deformation versus solution temperature. FIG. 2 is a graph showing tensile properties versus solution temperature.゛Solution temperature (“C)

Claims (1)

[Claims] (1) Ti-8Al-1, characterized in that the Ti-8Al-1Mo-1V alloy is solution-treated at a temperature 5 to 19°C lower than the β-transformation point, cooled, and then subjected to aging treatment.
Heat treatment method for Mo-1V alloy.