JPH03197632A - Intermetallic compound tial-fe base alloy - Google Patents

Abstract

PURPOSE:To improve the compressive deformation properties of the alloy and to permit the regulation of its structure by specifying the ratios of Ti, Al and Fe by atomic fractions. CONSTITUTION:The compsn. of an intermetallic compound TiAl-Fe base alloy is formed of a formula TixAl1-x-y-zFey; where, by atomic fraction, 0.50<=x<=0.52, 0.005<=y<=0.04 and 0.505<=x+y<=0.55 are satisfied. Its compressive properties are improved only when Fe atoms are blended so as to be substituted with Al atoms each other. Furthermore, the solid soln. strengthening owing to the addition of Fe is also permitted. In this way, its application to the process of working such as rolling and forging in which compressive stress is influential is made advantageous.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a TiAji-based intermetallic compound that is lightweight and has excellent high-temperature strength, and in particular to a TiAji-based intermetallic compound that has been subjected to component control in order to improve the deformation characteristics of the intermetallic compound. Regarding alloy systems.

[Conventional technology]

Intermetallic compound T expected to be put into practical use as a heat-resistant material
iAj! is difficult to process due to its poor malleability. Ti
Aj! Methods for improving this low formability, which is the biggest obstacle to practical application, can be broadly divided into machining process application and alloy design. Low workability mainly refers to lack of ductility at room temperature, and conventional processing methods such as rolling and forging cannot be directly applied to Til at room temperature.

When applied to machining processes, it includes near-net shaping typified by powder machining, as well as conventional machining methods such as rolling and forging. Until now, Co-based superalloy S-816)
High temperature sheath rolling using (x00℃, rolling speed: 1
．． 5 m/m1n) (Japanese Patent Application Laid-Open No. 61-2133
61 Publication), 800°C or higher, strain rate 10-” 5e
Constant temperature forging below c-' (JP-A-63-17186
It has been reported that processing shapes can be imparted by methods such as Publication No. 2).

The feature of this processing method is that it takes advantage of the ductility of TiA that can reach temperatures above 800°C, and when used in conjunction with the strain rate dependence of TiA's mechanical properties, it enables molding. There is. However, the processing conditions for sufficient molding processing must be a high temperature of 1000°C or higher.
Furthermore, since the strain rate must be reduced as much as possible, it has the disadvantage that it is not necessarily easy to apply large-scale equipment.

On the other hand, it has been reported that Ti and L are mixed, compacted, and then formed by high-temperature and high-pressure treatment (Japanese Patent Application Laid-Open No. 63-1400
Publication No. 49). This method is different from the upper δ self-adding process, and has the advantage of being able to be shaped into various shapes at the same time as molding. However, the problem is that the use of active metals such as T1 and Al causes impurities. It is pointed out that contamination is inevitable.

On the other hand, there have been reports of improvement in room temperature ductility due to additive elements.
V addition (Japanese Unexamined Patent Publication No. 56-41344) by nited Technology Carp, Mn addition (Japanese Unexamined Patent Publication No. 61-41740) by Metal Materials Technology Research Institute.
No. 1), Ag addition (Japanese Patent Application Laid-open No. 123847/1983), and General Electric Corp.
, S1 addition (US Pat. No. 4,836,983)
, Ta addition (US Pat. No. 4,842,817), C
Examples include r addition (US Pat. No. 4F142819) and B addition (US Pat. No. 4,842,820). In addition, to improve high-temperature ductility, 0.005 to 0.2 weight 1%
B addition (Japanese Unexamined Patent Publication No. 63-x4930) or 0
．． There is a report on the combined addition of 02 to 0.3% by weight B and 0.2 to 5.0% by weight Si (Japanese Patent Application Laid-open No. 125634/1983). The effects of these additive elements include not only improvements in low performance but also improvements in oxidation resistance and creep resistance, resulting in a wide range of alloy component adjustments.

The standard for ductility performance is said to be a room temperature tensile elongation value of 3.0%, but this has not yet been achieved by any compositional design method based on the selection of additive elements, and microstructural control such as refinement by combining with processing processes is required. It is considered essential to respond through these measures.

[Problem to be solved by the invention]

An object of the present invention is to provide a highly practical alloy that has excellent compressive deformation properties and is also capable of microstructural control by designing the composition of an intermetallic compound TiA1'-based alloy.

[Means to solve the problem]

A TiAA'-based alloy that achieves the above object has titanium, aluminum, and iron as its basic composition, and is expressed by the following formula using atomic fraction components.

Here, X.y refers to the atomic fraction of titanium and iron.

Ti, ARI-M-'yFey However, 0.50≦
x≦0.520.005≦y≦0.04 0.505≦x+y≦0.55 The present invention will be described in detail below.

High-purity titanium, high-purity aluminum, and high-purity iron are used as melting raw materials, and in order to avoid contamination with gaseous impurities such as oxygen and nitrogen, it is preferable to use a multi-electrode that can control a high vacuum atmosphere by simultaneously melting a titanium getter. A TiAA-Fe-based alloy is melted using the argon arc melting method. In order to prevent heterogeneity due to segregation of component elements, it is better to perform melting multiple times, and further perform homogenization heat treatment at 1050°C for about 48 hours under high vacuum of IXl0-'Torr or higher. .

The reason why the components of the Til-based alloy of the present invention are limited as described above is as follows.

Titanium: 50 to 52 atomic% In the single phase region of TiAl1, titanium is 45% at room temperature.
Within the range of 0 to 51.0 at%, Ti and A fl are on the titanium-excess side, and T is on the aluminum-excess side.
iAl2 crystallizes out. According to a room temperature compression test in a Ti - based system, the compression properties are superior when the titanium content is slightly more than the stoichiometric composition. For these reasons, the composition with excellent compression properties is the above composition in which the volume fraction of Ti and Al2 is 10% or less, and in order to stably obtain high compression properties, titanium is preferably 50 to 51 atomic %. .

Iron: 0.5-4 atomic% In addition to making the structure finer, the addition of iron also improves the Ll of TiAl.

Since c/a caused by the type structure (tetragonal) is brought closer to 1 by adding iron, the tetragonal lattice approaches a face-centered cubic lattice, and TiAji! It has the effect of reducing the crystal anisotropy of The amount of solid solution is small at less than 3 at%, but
Up to 4 atomic %, there is a self-effect, and beyond that, the volume fraction of the second phase increases significantly, and at the same time, the refinement effect decreases.

Another feature of component control in the present invention is that iron atoms are substituted with aluminum atoms in TiA to form a solid solution.If the atomic fractions of titanium and iron are x and y, respectively, the following equation displayed by.

Ti, Ax-x-yFey However, 0.50≦x≦0
．． 520.005 ≦y≦0.04 0.505 ≦x+y≦0.55 The key point of the present invention is that the compressive properties are improved only when iron atoms are mixed so as to mutually substitute with aluminum atoms on the crystal lattice. This is based on the discovery that the That is, the chemical formula of the alloy system of the present invention is expressed as the following formula (this is referred to as [Type I]). In other words,
This is different from cases where an iron atom is replaced with a titanium atom (the chemical formula is [Type 2]) or when both titanium and aluminum atoms are substituted (the chemical formula is [Type 3]). Shows the dissolved form.

[Type x Ti (AA, Fe) [Type 2]
(Ti,,Fe)Ai [Type 3]
(Ti, Fe) (Aj!, Fe) By specifying the composition range of the TiAl intermetallic compound within the range of the present invention, it becomes Type 1, and the grain size of the structure becomes fine and equiaxed crystals tend to develop. . Furthermore, the yield stress and fracture stress against compressive deformation are improved, the compressibility is also improved, and deformation becomes easier. In Type 2 and Type 3, no improvement in compression properties as in the present invention is observed.

〔Example〕

From high-purity titanium with a purity of 99.9% (oxygen content 400 ppm or less) 50 to 51 at%, aluminum with a purity of 99.99% from 46 to 49 at%, and high-purity iron with a purity of 99.99% from 1 to 3 at% The melted raw material was melted using a multipolar argon arc melting method that can control a high vacuum atmosphere.

During melting, melting was performed three times to avoid macro segregation of component elements, and homogenization heat treatment was performed at 1050° C. for 48 hours under high vacuum of I x 10-5 Torr or more.

The cross section from the melted ingot is 3 mmφ and the height is 4.5 mm.
A compression test piece was taken using a wire cutting device, and after precision parallel polishing of the compression surface, a room temperature compression test was conducted using an Instron type testing machine. In order to improve the reliability of the compression test, the test was conducted five times and the average value was taken, and the maximum and minimum variation accuracy of each mechanical property value was within 15% from the average value.

The compression ratio here is ((initial height of the test piece) - (height of the test piece just before it breaks in the stress/strain diagram))
/(Initial height of test piece) shall be X100. The compressive breaking strength is the value obtained by dividing the load immediately before the specimen breaks by the initial cross-sectional area on the stress-strain diagram.

The above examples of the present invention are shown in Tables 1 and 2. Table 1 shows the chemical analysis values of the test sample composition, and Table 2 shows the compression test results. In addition, the following comparative examples (1) to
(3) is also shown in each table above at the same time. The melting method and testing method for test samples in each comparative example were the same as in the above examples.

That is, Comparative Example (1) is a TiAβ binary system sample,
Comparative example (2) is TiA! They are added so that iron atoms replace titanium atoms in the binary system, forming a solid solution form of the type 2 described above, and these compositions correspond to the composition range of the following formula expressed as atomic fractions.

TI>IA j! I-X-yFe, however, 0.4
5≦x≦0.4950.005 ≦y≦0.04 0.49≦x+y≦0.51 Comparative example (3) is TiAj! In the binary system, iron atoms replace both titanium atoms and aluminum atoms,
It was added so as to take the solid solution form of Type 3 above. These compositions correspond to the composition range of the following formula expressed in atomic fraction.

TixA l 1-x-yFey However, 0.46≦
x≦0.500.01≦y≦0.05 0.51<x+y≦0.55 Comparing the above examples of the present invention and each comparative example, each comparative example is different from the example of the present invention. It was found that the breaking stress and compressive properties were inferior.

Table 1 (Atomic %) Table [Effects of the Invention] The present invention improves the compressive deformation characteristics and at the same time enables solid solution strengthening by adding iron elements, so it is possible to improve the mechanical properties as a whole. It has become advantageous for application to processing processes such as rolling and forging where compressive stress is dominant.

Furthermore, since the amount of added elements is very small, TiAf! It is thought that it will also be possible to apply it to aircraft parts because it does not impair the conventional lightweight properties.

Claims (1)

[Scope of Claims] An intermetallic compound TiAl-Fe-based alloy having excellent compressive deformation characteristics, comprising titanium, aluminum, and iron, and characterized in that the above elements are expressed as atomic fraction components according to the following formula. Ti_xAl_1_-_x_-_yFe_yHowever, 0.5
0≦x≦0.520.005≦y≦0.04 0.505≦x+y≦0.55