JPH03183737A - Aluminum-titanium alloy high in niobium content - Google Patents

Abstract

PURPOSE: To improve ductility and oxidation resistance of the like at room temp. by imcorporating Nb in a Ti-Al alloy at a specified atomic ratio.

CONSTITUTION: The Ti-Al alloy is manufactured by ingot metallugical method and its composition is defined as Ti_48-37Al_46-49Nb_6-14 in a rough atomic ratio. This Ti-Al alloy reformed by adding a comparably large quantity of Nb is provided with excellent ductility by adopting the usual ingot metallurgical method. This alloy has reformed properties and workability at a low temp. and medium temp.

COPYRIGHT: (C)1991,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention generally relates to alloys of titanium and aluminum. In particular, the present invention relates to an alloy of titanium and aluminum that has been modified (improved) both in terms of stoichiometry and in terms of niobium addition, with an increased concentration of the additive element niobium.

It is known that when aluminum is added to titanium metal and the proportion of aluminum is gradually increased, the crystal form of the resulting titanium-aluminum composition changes. When the proportion (%) of aluminum is small, a solid solution is formed in titanium, and the crystal form remains that of α titanium. At higher aluminum concentrations (e.g., about 25-35 at. %), intermetallic compounds T 13 Al are formed. This T 13Al has an ordered hexagonal crystal form called α-2. At still higher aluminum concentrations (e.g., in the range of 50 to 60 atomic percent aluminum), another intermetallic compound, TiAl, is formed which has an ordered square shape called γ.

Alloys of titanium and aluminum with a γ crystal form and a stoichiometric ratio of approximately 1- have high modulus, low density, high thermal conductivity, good oxidation resistance, and good creep resistance. It is an intermetallic compound. The relationship of modulus versus temperature for γTiAl compounds, other titanium alloys, and nickel-based superalloys is shown in FIG. As is clear from the figure, γTiAl has the best modulus among titanium alloys. Not only does γTiAl have a higher modulus than other titanium alloys at any temperature, but the rate of decrease in modulus with increasing temperature is smaller in γTiAl than in other titanium alloys.

Furthermore, γTiAl retains a useful modulus at temperatures above which other titanium alloys become useless. Alloys based on the γTiAl intermetallic compound are lightweight materials that are attractive for applications where high modulus at high temperatures and good environmental protection are also required.

Among the properties of γTiAl, one of the properties that actually limits its application to the above-mentioned uses is that it becomes brittle at room temperature. Furthermore, before this γTiAl intermetallic compound can be used for structural member applications, it is necessary to improve the strength of this intermetallic compound at room temperature. To enable such compositions to be used at the high temperatures for which they are suitable, it is highly desirable to modify this γTiAl intermetallic compound to increase its room temperature ductility and/or strength.

Given the potential benefits of light weight and high temperature use,
What is most desirable for the γTiAl composition to be used is a combination of strength and ductility at room temperature.

Although a minimum ductility of about 1% is acceptable for some applications of such metal compositions, higher ductilities are much more desirable. The lowest strength for the composition to be useful is about 50 ksi or about 350 MPa. However, materials with this level of strength can only be used for certain applications, and higher strength is often preferred depending on the application.

The stoichiometry of the TiAl compound can be varied over a range without changing its crystal structure. Aluminum content can vary from about 50 to about 60 atomic percent. However, the properties of TiAl compositions are such that the stoichiometric ratio of the components titanium and aluminum changes relatively small (1
% or more), it tends to vary greatly. Moreover, its properties are similarly greatly affected by the addition of a relatively small amount of a third element.

BACKGROUND OF THE INVENTION There is extensive literature on titanium-aluminum compositions, including T i 3 A I intermetallics, TiAl intermetallics, and T iA la intermetallics. r
T i Al type titanium alloy (TITANIUM A
No. 4,294,615 entitled LLOYS OF THE TiAl TYPE) J, TiAl
Titanium aluminide type alloys, including intermetallic compounds, have been investigated in detail. In column 1, line 50 and subsequent lines of this patent, the following points are made when considering the advantages and disadvantages of TiAl compared to Ti3A I.

It is clear that the rT i A lγ alloy system is potentially lighter due to its higher aluminum content. Laboratory research in the 1950s demonstrated the potential for titanium aluminide alloys to be used at high temperatures up to about 1000°C.

However, what has since been experienced in the engineering studies of such alloys is that although they have the required high temperature strength, they can only be used at room and moderate temperatures, i.e. between 20 and 550°C.
This means that it exhibits little or no ductility. Materials that are too brittle cannot be manufactured easily and cannot withstand the rare but inevitable minor damage that occurs during use, causing them to crack and then fracture. These are not useful engineering materials as substitutes for other basic alloys. ” Both TiAl and T r 3A I are basically ordered titanium-aluminum intermetallic compounds, but the TiAl alloy system (not to mention a solid solution alloy of Ti) is T I 3
It is quite different from AI. U.S. Patent No. 4.2
The bottom line of column 1 of No. 94,615 points out as follows:

``The skilled person recognizes that there is a substantial difference between the two ordered phases.

Since T 1 a Al and titanium have very similar hexagonal crystal structures, their alloying behavior and transformation behavior are similar. However, the compound TiAl has a tetragonal arrangement of atoms and therefore has different alloying properties.

Such differences are often not recognized in previous literature. No. 4,294,615 describes alloying TiAl with vanadium and carbon to improve several properties of the resulting alloy.

However, it should be pointed out with respect to U.S. Pat. However, this does not indicate whether all the alloys on that list are good alloys. Most properties of the listed alloys are not shown at all. For example, in Table 1, the alloy IT2A-119 has an atomic percentage of Ti-45AI-
1, OHf. This alloy corresponds to Alloy 32 listed in section (2) below in this specification. The composition mentioned by the present applicant in the article below is T i 54 A l 4
5Hf, so the above-mentioned U.S. Pat. No. 4,294,6
The atomic percent composition is exactly the same as the alloy listed in Table 2 of No. 15. However, as is clear from the applicant's Table 3, the titanium-based alloy containing 45% aluminum and 1% hafnium is an inferior alloy with extremely poor ductility.
Therefore, it has no valuable properties and has no use as a titanium-based alloy. Similarly, alloy Ti-45
AI-5, ONb is listed in Table 2.

That is, its properties are not listed, and there is no suggestion of any use or value for this alloy.

Some of the technical literature dealing with titanium-aluminum compounds and the properties of these compounds are listed below.

1. Bumps (E, S), Kessler (H, D) and Hansen (M, I)
(ansen), “Titanium-aluminum system (Tit
anium-^luminum System)”, Metal Journal (Journal ol MNals)
, Journal of the American Society of Mining and Metallurgy (TRANSACTIONS)
AIME), Volume 194 (June 1952), No. 6
Pages 09-614.

2. Ogden () 1. R, Ogden), Meikas (
D, J, Maykulh), Finlay (W, L,
Finlay) and Jaffee (R, I, J
a ((ee), “Mechanical Properties of High Purity Ti-Al Alloy”
Formerly ghNSACTIONS^IME), Volume 197 (
1, February 1953), pp. 267-272.

Furthermore, the three papers listed below contain limited information regarding the mechanical properties of TiAl-based alloys modified with niobium.

3, McAndrew (Jc+5eph B, Mc
Andrew) and Kessler (H,D)
er), “Ti-36%A as a base material for high-temperature alloys”
I (Ti-36Pct Alas a Ba5e f
or High Temperature＾1lo7s
) J, Journal ol Me
tals), 7me') fy Journal of Mining and Metallurgy (TRA
NSACTIONS^IME), Volume 206 (195
(October 6), pp. 1348-1353.

4, rTiA by Sastry (S”, L, 5xslr7) and Lipsill (H,^, Lipsill)
Plastic deformation of l and T r 3A I (Plastic D
efor+nttion of TiAl gndTi
3^1)", Titanium 80
(Wirrendale, Pennsylvania, USA)
rendxle) American Institute of Metals (^mericx)
n 5ocie17 for MejaO), No. 2
Vol. (1980), p. 1231.

5. Written by Sastry (S, M, L, 5astr7) and Lipjit (H1^, 1ipiilt), IT
i A Fatigue deformation of base alloy (Fatigue D
elor+nxlion ol TiAl Ba5e
Aoys) J, Journal of the Metallurgical Society (Mejxllorgi)
cal T+ansicjons), Volume 8A (19
(February 1977), pp. 299-308.

In the first paper mentioned above, rTi-35%Ai5%c
The specimen b has a room temperature ultimate tensile strength of 62°360psi, and the Ti-35%Ai7%cb specimen has a room temperature ultimate tensile strength of 75.800p.
si, it stretched into threads and broke." The two alloys appearing in the descriptions cited here are expressed in weight percent, and in atomic percent each T 148A l sr
, N b 2 and Ti47Al5oNb3.

It is well known that the fact that a test piece stretches like a thread and breaks, strongly suggests that the test piece is brittle. The article further states that compositions containing niobium have good oxidation and creep resistance.

The second paper concludes as follows regarding the effect of adding niobium to TiAl, but does not cite any specific data to support this conclusion. The conclusion is that the main effect of adding niobium to rTiAl is to lower the temperature at which twinning becomes the important deformation mode, thus lowering the ductile-brittle transition temperature of TiAl. be. However, this paper
There is no mention of whether the ductile-brittle transition temperature of iAl is lower than room temperature. The niobium-containing titanium-aluminum alloy exemplified is only Ti-36AI-4Nb expressed in weight percent, and there are no properties or other specific data. This alloy corresponds to T 14□, 5Al51Nb1.5 in atomic %,
The composition is quite different from the alloys taught and claimed herein, as will be explained in more detail below.

The composition described in the fifth reference above contains 36.2% by weight of aluminum in a titanium-based composition.
, contains 4.65% by weight of niobium, and when converted to an atomic composition, it is T i -51,A t -2Nb. This composition is similar to the last sentence of page 301 and the 30th sentence of this document.
The study was carried out as described in the first part of page 2. As stated in the last line of page 301 and the first line of page 302, the authors conclude as follows.

It has been found that the addition of Nb to the rTiAl base composition improves the low temperature ductility of the base composition.・・・・・・
As can be seen from FIG. 5, the addition of Nb does not significantly change the fatigue characteristics of the base composition. ” Figure 5 clearly shows that there is no major change in fatigue characteristics. However, this paper does not suggest at all that room temperature ductility is improved by the addition of Nb.

DETAILED DESCRIPTION OF THE INVENTION One object of the present invention is to provide a method for producing titanium-aluminum intermetallic compounds with improved ductility and related properties at room temperature.

Another objective is to use titanium at low and intermediate temperatures.
The objective is to improve the properties of aluminum intermetallic compounds.

Another object is to provide a titanium and aluminum alloy with improved properties and processability at low and intermediate temperatures.

Some of the other objectives will be apparent from the description below and some will be pointed out in each case.

In one broad aspect of the invention, the objects of the invention are achieved by providing a non-stoichiometric TiAl-based alloy and adding a relatively high concentration of niobium to the non-stoichiometric composition. . After addition, non-stoichiometric Ti containing niobium
The Al intermetallic compound is processed using an ingot method. It is possible to add about 6 to 14 parts of niobium to 100 parts of the base alloy, preferably about 8 to 12 parts.

DETAILED DESCRIPTION OF THE INVENTION As mentioned above, the intermetallic compound γTiAl is lightweight, has high strength at high temperatures, and is relatively inexpensive, making it a popular choice in industry without brittleness and processing difficulties. There should be some uses for it. This composition would have many industrial uses today if it were not for the fundamental property deficiencies that have prevented this material from being used in many industrial applications for many years. be.

The present inventor has demonstrated that by adding a small amount of niobium, γT
It has been discovered that iAl compounds can be made substantially ductile.

This discovery is the subject of co-pending US Patent Application No. 332.088, filed April 3, 1989.

Additionally, the inventors have discovered that the addition of niobium to a chromium-ductilized composition can significantly improve its oxidation resistance without compromising its ductility or strength. This discovery is the subject of co-pending US Patent Application No. 201,984, filed June 3, 1988.

The inventors have now discovered that ductility can be further significantly improved by adding high concentrations of niobium alone, in the range of 8 to 13 at.%, and combining this addition with the ingot process described in detail below. did.

In order that the improvements in properties of TiAl may be fully understood, several examples are provided and discussed before presenting examples of the novel compositions and process practices of the present invention.

Examples 1-3 Three melts containing titanium and aluminum at various stoichiometric ratios near TiAl were prepared. The compositions, annealing temperatures, and results of tests performed on these compositions are shown in Table 1.

For each example, an ingot was first made from the alloy by electric arc melting. This ingot was processed into ribbons by melt spinning under partial pressure of argon. In both melting stages, a copper water-cooled hearth was used as a container for the melt to avoid undesirable reactions between the melt and the container. Additionally, since titanium has a strong affinity for oxygen, care was taken to avoid exposing the high-temperature metal to oxygen.

The rapidly solidified ribbon was packed into an evacuated steel can and sealed. Next, this can was heated at 950°C (
Hot isostatic pressing (HIP) at 1740° F. for 3 hours. This HIP can was machined to extract a consolidated ribbon plug. The sample obtained with this HIP was a plug approximately 1 inch in diameter and 3 inches long.

This plug was placed axially into the central opening of the billet and sealed. The billet was heated to 975°C (1787°F) and extruded through a die at a reduction ratio of approximately 7:1.

The extruded plug was removed from the billet and heat treated.

That is, the extruded samples were annealed for 2 hours at the temperatures shown in Table ■. Annealing followed by 2 at 1-000℃
Time-aged. The specimen was machined to 1.5X3X25°4mm (0,060X
The dimensions were 0,120 x 1.0 inch). The bending tests were conducted on a 4-point bending tester with an inner span of 10 m (0.4 in.) and an outer span of 20 mm (0.8 in.). A load-crosshead displacement curve was recorded. The following characteristics are defined based on the resulting concavity line.

(1) Yield strength is the flow stress when the crosshead displacement is 1/1000 inch. This amount of crosshead displacement is considered the first sign of plastic deformation and the transition point from elastic to plastic deformation. Measurements of yield strength and/or fracture strength by conventional compression or tension methods tend to yield lower results than those obtained with the four-point bending tests performed in making the measurements described herein. be. The higher results obtained with four-point bending measurements must be kept in mind when comparing these values with those obtained with conventional compression or tension methods.

However, the comparisons of measurements made in many of the examples herein are between four-point bend tests, and for all samples measured with this technique, such comparisons cannot be made due to compositional differences or This is extremely effective in establishing differences in strength properties due to differences in processing methods.

(2) Breaking strength is the stress that leads to breakage.

(3) The external fiber strain is 9.7], the amount of hd, and “
h'' is the thickness of the specimen (in inches), and rdJ is the crosshead displacement at break (in inches). In metallurgical terms, this calculated value represents the amount of plastic deformation that the external surface of the bend specimen undergoes at failure.

The results are summarized in Table I below. Table I contains data regarding the properties of samples annealed at 1300°C, and further data specifically regarding these samples is shown in FIG.

No value was obtained.

As is clear from the data in this table, Alloy 1 of Example 2
2 showed the best combination properties.

As a result, the properties of Ti-Al1bi are changed to Ti/A
It is confirmed that it is extremely sensitive to the atomic ratio of l and the applied heat treatment. Alloy 12 was selected as the base alloy for further property improvements based on experiments conducted as described below.

It is also apparent that annealing at temperatures between 1250°C and 1350°C provides specimens with desirable degrees of yield strength, fracture strength and external fiber strain. However, when annealing at 1400℃, 135
Specimens are obtained that have significantly lower yield strength (about 20% lower), lower fracture strength (about 30% lower), and lower ductility (about 78% lower) than specimens annealed at 0°C.

The rapid decline in properties is due to dramatic changes in the microstructure,
This means that β over a wide range at temperatures significantly higher than 1350°C
It is caused by metamorphosis.

Ten additional melts were produced containing titanium and aluminum in the atomic ratios shown in the table, and further containing relatively small atomic percentages of additional elements.

Each sample was prepared as described for Examples 1-3.

The compositions, annealing temperatures, and results of the tests conducted for these compositions are shown in Table 1 in comparison to Alloy 12 as the base alloy for comparison.

+: The material broke during machining to produce the specimen.

In Examples 4 and 5, which were heat treated at 200 DEG C., the yield strength was not measurable since the ductility was found to be almost zero. The specimen of Example 5 annealed at 1300°C had increased ductility but was still undesirably low.

The same was true for the test piece annealed at 1250°C in Example 6. The specimens of Example 6 annealed at 1300°C and 1350°C had higher ductility but lower yield strength.

No significant degree of ductility was observed in any of the other test specimens.

As is clear from the results listed in Table 1, the set of various parameters involved in producing the test compositions are extremely complex and interrelated.

One parameter is the atomic ratio of titanium to aluminum. As is clear from the data plotted in Figure 4, stoichiometric or non-stoichiometric ratios have a significant effect on the test properties observed for the various compositions.

Another set of parameters are the additive elements selected for inclusion in the base TiAl composition. The first of this set of parameters relates to whether a particular additive element functions in place of titanium or aluminum. Individual metals can function in place of either element, and there are no simple rules that can determine which role a given additive element plays. The significance of this parameter becomes clear when considering the addition of a certain atomic proportion of the additive element X.

If X acts in place of titanium, the composition T
The effective aluminum concentration of 148A l 48X 4 is 4
At 8 atomic %, the effective titanium concentration is 52 atomic %.

Conversely, if additive element X functions as a substitute for aluminum, the resulting composition has an effective aluminum concentration of 52
in atomic %, the effective titanium concentration is 48 atomic %.

The nature of the substitutions that occur is therefore very important, but also extremely difficult to predict.

Another such parameter is the concentration of added elements.

Another parameter that is evident from Table ■ is the annealing temperature. It can be seen that the annealing temperature that produces the best strength properties for a given additive element varies depending on the additive element. This is the result obtained in Example 6 and Example 7
This can be seen by comparing the results obtained.

Additionally, there may be a combined effect of concentration and annealing on the additive elements. That is, if any property increase is observed, the optimum property increase may occur at a certain combination of additive element concentration and annealing temperature, and higher or lower concentrations and/or annealing temperatures may result in the desired property improvement. will decrease.

What is clear from the contents of Table ■ is that the non-stoichiometric T
The results that can be obtained by adding a third element to an iAl composition are very unpredictable and most test results are poor with respect to ductility or strength or both.

Examples 14-24 Eleven other samples containing titanium aluminide each having the composition shown in Table 1 were prepared in a manner similar to that described above in connection with Examples 1-3.

Table ■ summarizes the results of bending tests performed on all alloys, both standard and modified, under various heat treatment conditions deemed relevant.

Table ■ Table (continued) No measurable values were found.

**-The material was too brittle to be machined and samples for testing could not be obtained.

As is clear from Table ■, alloy 12.78.55.92
．． 67.123 and 137 are the base compositions T!
0.2 each as an additive element to s□Al48
．． 4.6.8.12 and 16 atomic percent niobium. From the data listed in Table 1, it can also be concluded that rapid solidification of these compositions does not improve their room temperature ductility.

Comparing these results for samples subjected to the same heat treatment (1300°C), it was found that as the concentration of niobium was gradually increased, the yield strength gradually increased, but the ductility gradually decreased. is shown ■
It can be concluded from the data. This finding is consistent with the teachings of McAndrew, supra paper 3, but Sastry (!+aslry) supra paper 4.
and 5 are inconsistent with the teachings of 5.

Also, from Table 2, at the additive element level of 8 atomic % and 12 atomic % (see Alloys 67 and 123), the specimens were heated to 1350°C.
It is also clear that a better combination of strength and ductility can be obtained by heat treating at a level of 1%, but the ductility remains below 1%.

For samples with low niobium concentrations, such as Samples 78 and 55, it was found that the improvement achieved by such heat treatment was not so pronounced, and therefore the improvement effect imparted to the samples by such heat treatment was not obtained. did.

Comparing the test results for alloys 55.66.40 and 119 in the table provides one insight.

This comparison is made for samples with the same level of added element niobium, 4 atomic percent, but with different titanium and aluminum stoichiometric ratios. Studies of these compositions have discovered that the aluminum concentration can be reduced slightly to significantly increase ductility without sacrificing attractive strength. However, if the aluminum concentration is lower than 46%, ductility almost disappears, so it cannot be lowered below 46%. Further, even when the aluminum content is 46% or more, the ductility is 1% or less.

Considering the data in Table ■, it is clear that if the aluminum concentration and annealing temperature are appropriately adjusted according to the teachings contained in Table ■, there is an optimum concentration of additive element niobium between 4 and 12 at.%. be.

All the above test samples were manufactured by rapid solidification method. All of the test samples listed in the table above were also tested using a 4-point bending test.

Tensile Testing and Four-Point Bending Test As mentioned above, all the samples in the above examples were manufactured using the rapid solidification method and were tested using a four-point bending test. This applies to all the data listed in the table above.

The results of fabrication and testing as described above in Examples 20-22 show that materials containing 8-12 at. Most of them had extremely limited ductility.

The present inventor has now discovered that a composition having a relatively large amount of niobium of 8 to 12 at. It has been discovered that very good ductility can be achieved if the test is carried out using conventional ingot metallurgical methods and conventional tensile testing methods.

The main difference between these processing methods is that ingot metallurgy involves melting and solidifying the components into an ingot, whereas rapid solidification processes form ribbons by melt spinning and then consolidate the ribbons. The point is to obtain a sufficiently dense and integrated metal sample.

However, care must be taken before starting the ingot processing method. It concerns different measurements commonly used when testing samples processed by the ingot method.

Samples processed by the ingot method are commonly tested by conventional tensile testing using tensile test bars specifically made for the purpose.

In order to properly compare the properties of alloys produced by rapid solidification methods with those produced by conventional ingot processing methods, a series of tests using conventional tensile bar tests were carried out on the properties of rapidly solidified alloys. I did it.

Example 25 Tensile bar test on rapidly solidified samples For this purpose, alloy samples produced by the rapid solidification method (mostly according to the table
I made a set of regular pins from the following. A γTiAl alloy containing niobium was also produced by the rapid solidification method described above. This alloy is called Alloy 132.

This contained 6 atomic percent of the additive element niobium. A series of pins was made from each of the test alloys listed in Table 1 below, as well as a series of pins from Alloy 132.

Various pins were annealed separately at different temperatures listed in the table below. 100 pins after individual annealing
Aging treatment was performed at 0°C for 2 hours. After annealing and aging, each bottle was machined into a conventional tensile test bar, and the resulting bar was subjected to a conventional tensile test. The results of the tensile test are shown in the bag (■) below.

Table ■ Table ■ (Continued) Furthermore, as is clear from the data shown in Table ■, an oxidation resistance test was also conducted.

Alloys containing the additive element niobium listed in Table ■ in various proportions and γTiAl alloys without niobium (
Comparing with alloy 12) it is clear that there is little overall improvement in terms of ductility. Although there are some alloys that have significantly improved strength, they generally have very low ductility. For example, alloy 11
9, the alloy strength is very high (124ksi and 12
0ksi) corresponds to very low ductility (i.e.
0.1).

As is clear from the data shown in Table ■, there has been an overall improvement in terms of oxidation resistance.

Example 26A Ingot Metallurgy and Tensile Bar Tests A second set of several alloy compositions listed in the table above were
They were prepared by conventional ingot metallurgy rather than the rapid solidification method used in the case of the first set prepared as described in the previous examples. If the alloy processed by the ingot method has the same alloy composition as the alloy of the above example, the same example number was used, but rAJ was added to the example number to indicate that it was processed by the ingot method. . Also,
An additional alloy, designated Alloy 26A, was also prepared by processing the ingot process.

The properties of the alloy thus prepared were tested.

the The test results are listed in the box below.

Table ■ However, Alloy 12A of Example 2A is
It was manufactured using an ingot metallurgy method instead of the rapid solidification method described in 2. Tensile and elongation properties were tested using the tensile test bar method rather than the four point bend test used for Alloy 12 in Example 2. The other alloys listed in the table were also produced using conventional ingot metallurgy methods. All tensile data in the table was obtained using the conventional tensile test bar method.

The ingot processing method (also referred to herein as casting and forging processing) is essentially the same for each of the alloy samples prepared and is as follows.

An ingot having dimensions of about 2' in diameter and about 1/2' in thickness and shaped like a hollow hockey puck is produced in an ingot melting process. After melting and solidifying this hockey puck-shaped ingot, the ingot has a wall thickness of approximately 1 mm.
/2' and the vertical thickness corresponds to the thickness of a hockey puck ingot. The hockey puck-shaped ingot was homogenized by heating to 1250-1400° C. for 2 hours before being enclosed in a retaining ring. Approximately 975 pieces of this hockey puck and retaining ring
heated to a temperature of °C. The heated sample and containment ring were forged to approximately half the original thickness.

After cooling the forged ingots, several pins were machined from ingots that underwent several different heat treatments. The various pins were each annealed separately at various temperatures as shown in Table V above. After each annealing, the pins were aged at 1000° C. for 2 hours.

After annealing and aging, each pin was machined into a conventional tensile test bar, and the resulting test bar was subjected to a conventional tensile test. The results of this tensile test are listed in Table 3 above.

As is evident from the table, the four samples of alloy 67A were tested at four different temperatures, namely 1300°C, 13
Separately annealed at 25°C, 1350°C and 1375°C. The yield strength of these samples is that of the base alloy 12.
This is a big improvement over A. For example, a sample annealed at 1300°C is an alloy 12 annealed at the same temperature.
Compared to A, the yield strength was improved by about 37%. Other improvement rates are of the same magnitude. Alloy 67 annealed at 1300°C, although the ductility decreased contrary to this improvement in strength.
The ductility of A is significantly improved over the similar sample of Example 21 listed in Table 3. Other heat treated samples showed a similar increase in strength and some decrease in ductility relative to base alloy 12A, although some samples showed some improvement in ductility. When considering this improvement in strength in combination with somewhat reduced or increased ductility, these gamma titanium aluminide compositions are extremely unique.

Here, the test results listed in Table V will be considered again.

Comparing this data with, for example, the data listed in Table ■ reveals that the yield strengths listed in Table ■ measured for rapidly solidified alloys are Somewhat higher than the yield strength as measured on metal specimens and listed in Table 3. It is also clear that the samples produced by ingot metallurgy have higher ductility (plastic elongation) than those produced by rapid solidification. However, the above results are shown in Table ■
Alloy 12A manufactured by the ingot metallurgy method listed in Table ■
This provides a good comparison standard when considering Alloy 12 produced by the rapid solidification method mentioned in .

However, a general comparison between the data in Table ■ and the data in Table ■ reveals that when the concentration of the additive element niobium is higher, the production of alloy samples using ingot metallurgical processing techniques and the conventional High niobium alloys produced by ingot metallurgy are highly desirable for applications requiring high ductility, as shown by testing samples using the tensile bar testing technique. In general, ingot metallurgical processing does not require an expensive melt-spinning step itself, but does require a consolidation step that must follow melt-spinning when rapid solidification methods are used. It is well known that processing and processing by melt spinning or rapid solidification is much less expensive as it does not require much processing.

Oxidation Resistance The alloys of the present invention also exhibit excellent oxidation resistance. The oxidation tests listed in Table ■ are static tests. This static test consists of heating the alloy sample to 982°C for 48 hours. This is carried out by cooling and weighing the heated sample. Divide the weight gain by the surface area (enf) of the sample. The result is a surface area of 1al! for each sample. Increase in weight per unit (mg
).

The data listed in Table ■ were measured using the same static standard.

Several dynamic oxidation resistance tests were conducted on some of the alloys listed in Table ■. The data from these tests were
Plotted in the figure. In FIG. 4, the weight gain (■/cIIf) resulting from oxidation of the indicated alloy samples is plotted against the time of dynamic exposure to oxidation at 850°C. Dynamic, or repeated, exposure to a hot oxidizing atmosphere means repeatedly cycling the test sample through a series of heating and cooling processes, during which time its weight is measured as the sample cools to room temperature. . Heating was carried out to 850 °C in each case, and the sample was heated to 85 °C during each cycle.
Maintain temperature at 0°C for 50 minutes. Cooling is not forced cooling, but cooling in the ambient atmosphere at room temperature. For an average sized sample, it takes approximately 109°C to cool, weigh, and return to the test furnace to heat to a temperature of 850°C. The time to heat up to the test temperature and cool down from that temperature is not part of the 50 minutes mentioned above; the 50 minutes is the time the sample is held at that temperature.

The data shown in Figure 4 is a plot of weight change for the four samples tested. As is clear from the plot in Figure 4, the additive element niobium is 8 atoms, 96 atoms, and 1-2 atoms.
The alloy containing atomic% was by far the best composition in terms of cyclic oxidation resistance.

Figure 3 shows similar data but with different criteria. In FIG. 3, oxidation resistance is determined when the weight increase of the sample is 0.
It is shown based on the time required to reach 8■/d. For T f 44A 1 48Nb8, this time is 500 hours.

FIG. 3 also shows the relevant strength and ductility data for each alloy.

As is clear from the data plotted in Figures 3 and 4, the alloy TiAtN processed by the ingot method
b is an unusual new 4B-3746-496
-14 It can be seen that this is a new and unique alloy with a combination of properties.

[Brief explanation of drawings]

FIG. 1 is a graph showing modulus versus temperature for a series of alloys. Figure 2 shows different stoichiometry of Ti tested by 4-point bending method.
1 is a graph showing the relationship between load (pounds) and crosshead displacement (mils) for an Al composition (heat treated at 1300° C./2 hours). FIG. 3 is a bar graph showing a comparison of the properties of several alloys. Figure 4 shows the weight increase (mg/a) when four alloys were oxidized in air at 850°C for 1 hour.
1) is plotted against dynamic exposure time (hours).

Claims (10)

[Claims] (1) Manufactured by ingot metallurgy, essentially having the following approximate atomic ratio Ti_4_8_-_3_7Al_4_6_-_4_9N
Niobium-modified titanium-aluminum alloy consisting of titanium, aluminum and niobium of b_6_-_1_4. (2) Manufactured by ingot metallurgy, essentially Ti_4_6_-_3_8Al_4_8Nb_6_-_
A niobium-modified titanium-aluminum alloy consisting of titanium, aluminum and niobium in an approximate atomic ratio of 1_4. (3) Manufactured by ingot metallurgy, essentially having the following approximate atomic ratio Ti_4_6_-_3_9Al_4_6_-_4_9N
Niobium-modified titanium-aluminum alloy consisting of titanium, aluminum and niobium of b_8_-_1_2. (4) Manufactured by ingot metallurgy, essentially Ti_4_4_-_4_0Al_4_8Nb_8_-_
A niobium-modified titanium-aluminum alloy consisting of titanium, aluminum and niobium in an approximate atomic ratio of 1_2. (5) A niobium-modified titanium-aluminum alloy produced by ingot metallurgy and consisting essentially of titanium, aluminum and niobium with the approximate atomic ratio Ti_4_4Al_4_8Nb_8. (6) Essentially the following approximate atomic ratio Ti_4_8_-_3_7Al_4_6_-_4_9N
b_6_-_1_4 Structural components formed from niobium-modified titanium-aluminum alloys consisting of titanium, aluminum and niobium, said alloys being produced by ingot metallurgy. (7) Essentially the following approximate atomic ratio Ti_4_6_-_3_8Al_4_8Nb_6_-_
1_4 Structural element formed from a niobium-modified titanium-aluminum alloy consisting of titanium, aluminum and niobium, said alloy being produced by ingot metallurgy. (8) Essentially the following approximate atomic ratio Ti_4_6_-_3_9Al_4_6_-_4_9N
b_8_-_1_2 Structural components formed from niobium-modified titanium-aluminum alloys consisting of titanium, aluminum and niobium, said alloys being produced by ingot metallurgy. (9) Essentially the following approximate atomic ratio Ti_4_4_-_4_0Al_4_8Nb_8_-_
1_2 Structural components formed from niobium-modified titanium-aluminum alloys consisting of titanium, aluminum and niobium, said alloys being produced by ingot metallurgy. (10) A structural member formed from a niobium-modified titanium-aluminum alloy consisting essentially of titanium, aluminum and niobium with the approximate atomic ratio Ti_4_4Al_4_8Nb_8, wherein said alloy is manufactured by ingot metallurgy. .