DE1904814A1 - Machinable nickel-based superalloys - Google Patents

Description

CYÖIiOPS CORPORATION Pittsburgh, Pa. / V.St.vJU

Bearboitbare superalloys based on nickel

The invention relates to alloys, you at high
Temperatures can be used. Sis pays particular attention to a lodging on tliekolbasiö, which can be processed warm and contains an exact combination of elements, with insufficient strength, "Krisch-,
Buktility and corrosion properties up to 1038 ⁰ C

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"Oils Lw ft drive" r <rul Hamsfafaxtinätisstria unü clex'gleiehen. Many superimpositions have been developed, but the range of applications of these alloys is limited, as they do not at the same time provide the desired high-temperature strength properties in ο sufficient jluctility for the winter Aufvrieson. With ßia S ^ end sur 33nt \ riaklung of machines with higher and higher JDeisttiQgen sx-there were also increasing stresses on one of his ropes of these machines ₀

The need to increase the strength of nickel-based alloys has resulted in the addition of solid solution-forming hardness compounds such as EoB. Chromium ₉ molybdenum;, tungsten, aluminum and titanium. This development has led from ITickslbasia alloys with θ in as lower strength utfS their sufficient ductility to cast nickel-based alloys with a high strength abas? ο resulted in a · very limited ductility · alloys that are cast and not otherwise processed, but do not have the necessary high degree of security, even if the baste pre-casting process is feared, the increased G-ohait this ?. ' Sleiusnts also has ku ainsr instability fier alloy got'ülirfe, ria dia Ansi * i.illung von Piiaoen r? Owoh ' ^! - rtio F-ystigksif; as βτι? 1ι the jluktiiität d & r alloy i »i ab-

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after heat treatment and / or after a long period tion occur at elevated temperatures.

According to the invention an alloy is proposed to Uiekelbasis having up to a einperatur l'of 1038 ⁰ C FeEtigkeitseigenechaften acceptable, and which is compared to the presently used alloys considerably improved. The alloy has sufficient hot workability that it can never be extruded, forged and / or warragewaist and does not have to be cast. An improvement in the oxidation resistance was also achieved. The ductility and corrosion resistance were not adversely affected.

Although the amount of alloy seeds in this material has been increased significantly over current machinable alloys, stability has not been adversely affected. The term "workable" ^1: As used liier "states" that the 3iGgierung can be hot worked, ie, "that they extnsdiert, forged and / or viariage" MLST may have been.

JJio o'Glr.an Hesultato i-mrdei "achieved by Saß ο in α ge · P. Combination of Bleraonton used vmrdc to orsielßn a high" without losing any of the sinister properties,

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which are normally adversely affected by an increase in strength, are deteriorated. This precise balance of elements used results in a reduction of the formation of harmful phases which lead to instability of the alloy. The technique of avoiding undesired phases by calculating the electron vacancy numbers was used to find the present alloy.

The structure of the superalloys Nickelbaeis mainly consists gajmca primary phases aue carbide t Wl Xungen and from a gamma matrix. If the composition of the material is not correct, then undesired phases form from the constituents through nucleation on carbides and through influx (feeding) to the gamma matrix. These undesirable phases adversely affect the stability and strength of the material. These are intermetallic sigma, mu and Laves phases. Accordingly, the composition of the matrix is of great importance in the development of new nickel-based superalloys. The matrix of the alloy according to the invention consists of nickel, cobalt, chromium, molybdenum, tungsten and tantalum. The individual amounts of this alloy component in the matrix are determined by other elements in the alloy, such as aluminum, titanium, carbon and boron, all of which undergo a reaction with the formation of precipitates.

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experience phases of lungs habon.

The alloys of the invention have been vacuum melted although the use of other suitable Sohmela procedures is possible.

The carbon content should be between $ 0.25 and $ 0.45, preferably between $ 0.30 and $ 0.40. At least 0.25 ¹ pi, a content which is currently to be regarded as high, are necessary in the alloys according to the invention so that they can be machined. However, extremely high carbon contents e (ie above 0.45 #) are undesirable as this makes the alloy brittle. The elements responsible for solidification by the formation of solid solutions form carbides, and these carbides give rise to a morphology which is poor for the desired properties.

The silicon and manganese give the alloy resistance to oxidation. Quantities above 2.0 # manganese and 1.5 $> silicon are unfavorable for the mechanical properties. Increased silicon content can also be bad for machinability. An alloy with up to 0.50 # mixed metal has additional resistance to oxidation. Mlsch metal contains various amounts of rare earth elements, with cerium, lanthanum and yttrium in general

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mean the main ingredients are. Sine sulfide is corrosion resistance can also be done by adding the above mentioned! rare earth elements can be achieved.

Chromium "imparts in the broad range from 11.0 to ^{17.0 # (preferably 11.0 to 13.0 c} ß>) an oxidation and corrosion resistance, a strengthening by the formation of solid solutions and a strengthening of the grain boundary surfaces. A chromium content below $ 11.0 does not provide the desired resistance to oxidation and corrosion, and a chromium content of more than $ 17.0 makes it difficult to hot work the alloy, and the stability is also severely impaired *

Cobalt is in the wide range of $ 8.0 to $ 12.0 (preferably 9 »0 to 11.0? *) Used to denote an inherent strength Achieve shafts at an elevated temperature. Ba can too the ductility, machinability and creep properties to enhance. Cobalt in an amount more than 12.0 # deteriorated the oxidation and corrosion properties,

Lantalum is a critical element because of its hardening through the formation of solid solutions and because of its carbide formation. Amounts of 1.0 to 3.0 # are desirable, with a range of 1.25 to 1.75 microns being preferred. Amounts above 5.0% worsen the ductility and the working capacity and can also lead to the formation of unfavorable secondary phases.

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Molybdenum and tungsten also participate in carbid formation and hardening by solid solutions. The broad range of molybdenum is 2.0 to 6.5 fi, with the preferred range is 2.5 to 3 »# 5. Levels at the lower end of this range are desirable because the presence of high molybdenum can lead to the precipitation of harmful phases. The tungsten content is in the range from $ 4.0 to $ 8.0, with a range from 5 »5 to 6.5 5» being preferred.

Aluminum and titanium are also critical elements as they add strength to Uiekel based superalloys. The broad compositional range for aluminum is 4.0 to 5.0 ^. An improved compositional range is 4.20 to 4.80 #, and the preferred range is 4.45 to 4.70 fio. This is a critical range because below 4 _f 0 i * aluminum the alloy does not achieve the desired strength value, and so above 5.0 # the alloy shows a large loss in ductility, machinability and stability. The broad compositional range for titanium is 2.2 to 3.2 ^, with a range of 2.8 to 3 »2 f» being preferred. Titanium, which is also a carbide former, has essentially the same effect as aluminum.

Both boron and zirconium improve creep resistance at elevated temperatures. The wide range for boron

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is £ 0.0005 to $ 0.030 with a range of $ 0.008 to $ 0.018 being preferred. Zircon has a wide range of. O ₅ 001 I "and a preferred range of 0 _P 005 to 0.150 to 0.25 foe An excess of these elements has a detrimental effect on the ductility and the stability of the alloy,

The base metal for the alloy is nickel, its assets, Hardening through the precipitation of secondary phases and carbides additionally through the formation of solid solutions makes it for them Application ideal

Chemical Analysis and the Preferred Areas of Ele « Elements of the alloys according to the invention are given in Table I. held in susamines. -

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TABLE I.

element

Carbon manganese silicon chromium cobalt molybdenum tungsten ! Tantalum aluminum (Ditan

Zirconium nickel

Area j5 until * more preferred
Area % * until 0.40 0.25 to 2.00 0.45 0.30 Max" bia au 1.50 1.00 max ο until until 1.00 until 13.0 11.00 until 17.00 11.0 until 11.00 8.00 until 12.00 9.00 until 3.50 2.00 until 6.50 2.50 until 6.50 4.00 until 8.00 5.50 until 1.75 1.00 until 3.00 1.25 until 4.70 4.00 until 5.00 4.45 until 3.20 2.20 0.0005 to 3.20 2.80 until 0.018 0.001 bia 0.030 0.008 until 0.150 ; 0.250 0.005 Heat rest

* All percentages are expressed in weight, unless otherwise stated «

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Trace elements such as sulfur, phosphorus, lead, etc. as well as residual iron are as best as they are due to normal Schmelaververfahren arise, permissible. Bisen can be in quantities up to 2.00 5 », but it is preferred that the iron content is below $ 1.0.

Some of the mechanical properties of this new alloy are listed in Table II below with the current values available alloys compared.

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ΪΑΒΕΜΚΒ II

Mechanical properties

rehearse Yersuchs- 871 End train- » π ο ί £ - strain Cross No. ₀ temperature strength Puddle (£ in 1 «: ) sectional (° 0) (kg / cm ² ) tension
(kg / cm ² ) reduction 1 Room temp. 14112 14427 12.2 14.1 2 H 13846 11914 6.2 9.3 3 I! 15302 12061 12.4 13.8 4th Il 14427 10850 15.0 18.3 6th It 14525 11984 6.3 8.8 7th W. 14581 11193 13.1 14.3 1. 760 11249 IO29O 6.9. 12.1 2 760 12292 11221 4.0 8.1 4th 760 11564 9940 12.9 19.0 6th 760 12145 10927 2.7 8.1 7th 760 11599 10129 8.7 13.2 1 871 8778 7476 8.7 18.9 2 871 8582 7532 6.1 .10.8 3 871 8995 7539 3.7 6.0 4th 871 8407 7385 6.2 7.5 6th 871 8701 7329 5.9 7.8 7th 871 8295 6902 7.8 13.4 9 871 7973 6447 19.0 49.1 against- Room temp. 14280 9800 17.0 - ready -
usual ^{7t> 0} 9100 8400 33.0 - Alloy 7000 6440 33.0

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At elevated temperatures there is a need for higher strength properties and an optimal © buctility. Excessive buctility at elevated oil temperatures results in poor creep rates, and inadequate buctility results a sensitivity to brittleness fractures at notches, the Strength values determined by the ultimate tensile strength and the yield stress measured are better than the currently used alloy, while the buctility, measured by the elongation and the reduction in cross-section, is optimal, there would be excessive creep rates or excessive notch sensitivity can be prevented. The current alloy, because of its excessive ductility, tends to have excessive creep rates at elevated temperatures and gives rise to dimensional instability.

The stress-rupture properties of the alloys according to the invention are given in Table XXI.

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■ • 13 * ·

! PABELIiE JII ■ Spam tear properties

Samples test hot tear elongation transverse

H temperature voltage lifetime (# in 1 ") cut rvo./rtm ² ^ / ej + Λ \ reduction

lcg / cin; iStdj

1 815 4900 106.1 4.1 3.0 3 815 4900 63.8 3.4 7.5 4th 815 4900 177.7 7.7 14.8 1 871 3850 52.0 6.6 9.6 2 871 3850 91.9 7.5 8.5 4th 871 3850 95.7 7.0 8.4 5 871 3850 109.1 6.5 8.0 6th 871 • 3850 78.6 2.7 7.6 7th 871 3850 81.9 5.6 19.8 8th 871 3850 79.2 8.5 11.9 1 982 1400 95.0 11.1 16.7 2 982 1400 116.0 6.7 24.3 3 982 1400 91.3 9.7 10.3 4th 982 1400 174.2 9.4 16.6 5 982 1400 125.2 15.6 24.2 7th 982 1400 106.5 13.0 ■ 34.1 1 1037 1050 19.3 21.9 33.4. 4th 1037 1120 25.8 5.1 21.7 4th 1037 1050 28.9 9.1- 21.7 5 1037 1050 14.9 23.6 42.6

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To compare the stress tear properties of the invention * proper alloying with the current alloy has been the Larson-Muller parametric method, which has been used in the art is generally known, used uia the heating voltage bsi 100 hours at different test temperatures o The results are shown in Table IV.

OJABELLB IV

100 hour tensile strength properties alloy Vörsuehs-
temperature (C) Easing tension
(kg / cm ² ) Lherbier et al. 815 4970 current alloy 815 4060 Lherbier et al " 871 3850 current alloy 871 2940 Lherbier et al " 926 2450 current alloy 926 1890 Lherbier et al. 982 1540 current alloy 982 1120 Lherbier et al. 1057 770 current alloy 1037 490

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These numbers are shown in the graph of Figure 1 of the accompanying drawings, where the logarithm of stress is plotted against tear life value, which includes both time and temperature. The tear life value is represented by the Larson-Müller parameter T (20 + log t), where T is the temperature in ⁰ P and t is the time in hours.

The results in Table IV show a considerable improvement The tensile strength at break at 100 hours for all test temperatures when using the alloy according to the invention compares to the currently used alloy. The improvement can best be seen in Figo 1, where the Relationship between the strength and the service life of the invention Alloy is compared with the currently used alloy.

The chemical analysis of the test samples and the present usual alloy used in determining the mechanical Properties used are given in Table V.

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Actual composition (wt .- $ S) and electron vacancy number

C-Cr Co Mo W Ea Ii Al Zr B Ki U _v

0.35 11.81 10.02 4.99 5.05 1.85 3.05 4.64 0.11 0.015 remainder 2.55

0.32 12.00 9.98 5.02 5.07 1.69 2.98 4.65 0.147 0.012 remainder 2.58

0.34 11.99 10.02 5.08 5.18 1.76 3.10 4.63 0.10 0.018 remainder 2.62

0.32 12.18 10.04 2.92 6.03 1.46 3.10 4.62 0.11, 0.018 remainder 2.46

0.35 12.16 10.00 2.96 5.93 1.47 2.95 4.56 0.11 0.013 remainder 2.39

0.25 12.00 9.90 4.95 5.05 1.75 3.04 4.40 0.135 0.015 remainder 2.51

0.43 12.17 10.05 4.98 5.20 1.45 2.90 4.62 0.12 0.016 remainder 2.49

0.34 11.92 9.94 3.01 6.40 1.93 3.15 4.52 0.13 0.017 remainder 2.48

nominal composition (wt .- ^)

against-

? ^e 0.06 '15, OQ 15.00 5.25 - - 3.50 4.40 - 0.03 remainder

Cb.

0.26 11.84 9.97 5.96 6.10 1.09 3.06 5.10 0.078 0.017 remainder 2.97

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The resistance to oxidation caused by the increase in weight measured at certain time intervals at elevated temperatures is used to reduce the corrosion properties caused by the The resistance to sulphidation measured are comparable to those of the currently used alloy

The hot workability of the alloy results from the The fact that the cast slabs produced were extruded, forged or hot rolled. The three just mentioned Y / arm machining methods have also been achieved with various combinations of the same. The cast slabs were too rolled directly into bars, rails and sheets.

The method of calculating the electron vacancy number (N _v ) for an alloy is known to those skilled in the art. It basically consists in calculating the average number of electron vacancies (N _y ) in an alloy by forming the atomic fractions of the elements concerned. The composition of the alloy matrix then becomes a critical part in the calculation and any precipitated phases are subtracted from the total alloy composition. The nature, amount, and compositions of the precipitated phases are first determined by various empirical methods also known in the art.

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In particular, as shown in the example, the alloying elements are converted into material in atomic percent. Following the calculation of the precipitated borides * carbides and gamma primary phases, the remaining alloying elements are taken as a matrix.The quantities of matrix elements are converted to 100 ⁰ A and the new matrix setting is then used to calculate the mean number of electron vacancies through stimulation.

An example of calculating the metal electron void number of sample No. 3 according to the present invention will be explained below.

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Actual method used when calculating the electrons! e number of stiles (H_) for the sample ITr. 5 was used

element Ge *? .- $ 5 Gev /.-$ Atomic rose C. 0.35 Atomic weight 1.66 Cr 12.16 0.029 13.36 Go 10.00 0.2338 9.70 Mq 2.96 0.1697 1.76 W. 5.93 0.0308 1.85 Approx 1.47 0.0323 0.46 Al 4.56 0.0081 9.66 Ii 2.95 0.1690 3.52 B. 0.013 0.0615 0.07 Zr 0.11 0.0012 0.07 Ni 59.50 0.0012 57.90 1.0135

First of all, the matrix contains atoms of every element in

an amount corresponding to the atomic percent. The following reactions take place:

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a) Loss of τοπ elements due to the formation of boric! en

EggtljLcheJiSleiaente after

Ni «57.90 - (0.30 x% 2X) β 57.89 Gr «13.36 - (0.75 χ & pl)» 13.53 Ii - 3.52 - (0.45 x ™ ^) - 3.50

0 07 Mo «1.76 - (1.50: z -—-) s 1.71

b} Loss of elements through the formation of carbides, where M one or more radial elements; depicted

MC + M ₆ C [MipGoMo., 0]

Essential elements

1.66 ji of available carbon

MC - 0.83 # carbon

Ta κ 0.46 - Oy46 «0 after the

Zr * 0 _f 0? - OpO? - 0 Mö reaction

.2: 1 «3.50 - 0.30 ~ 3.20

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MgC ~ 0.85 f * carbon

Hi * 57.89 - 1.66 «56.23 Co "- 9.70 - 0.83 - 8.87 Mo * = 1.71 - 2.49 "0 W" 1.85 - 0.78 = 1.07

MCg response

c) Loss of elements for the formation of gamraa primary phases +! Egg + 0.1 Cr)

Remaining elements after the formation of gaam prJLmärphaoen

Cr »13.33-1.33», 12.00

Hi = 56.23-3 (9.66 + 3.20 + 1.33) = 13.66

Now the matrix contains those atoms of each element, who did not participate in the above reactions. This leaves:

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element remaining atoms
(*) " percentage
the rest
Substances in the
matrix C. O ₅ O Cr 12.00 33.71 Co 8.87 24.92 Mon 0.0 0.0 W. 1.07 3.01 Ta 0.0 0.0 Al 0.0 0.0 Ii 0.0 0.0 Zr 0.0 0.0 B ■ 0.0 0.0 Ii 13.66 38.37

The electron vacancy number (N ") becomes from the following Equation determines:

H ^ = 4.66 (Cr + Mo + W) "+ 1.71 (Co) + 0.66 (Hi)

where each chemical symbol represents the percentage of the remaining substances in the matrix.

4.66 (33.71 +3.01) + 1.71 (24.92) + 0.66 (38.37) 2.39

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■ Calculations in a series of alloy systems have shown that there is a susceptibility to the electron vacancy number with the experimental occurrence of νοκ sigma, mu and Lavss phases. During the course of development of erfindungsgomäßen alloy was made © ine parts between alloys unwanted s \ ^r v eite phases developed and di © were free of such phases "

In the attached photomicrographs, Pig "2 and 3", a comparison of an acceptable microstructure, Figo 2 "and an unacceptable microstructure, Fig, 3,. Fig. Shown, 2 is a photomicrograph of a test stick of sample no"> 5? which has an electron vacancy number of 2.39 on \ feist "Figo is a photomicrograph of a test piece from the sample ITr.9t which has a chemical composition outside the broad range (see" Table V) and has an electron vacancy number of 2.97. Both the photomicrographs were taken of samples which were in an identical heat-treated state. They are 4,000 times larger than that » p, er to

In Pigο 2 the large, almost spherical particles are MO carbido 3) ie the smaller somewhat spherical epidemics that occur the grain boundaries have failed are MgO carbides Inside the grains are sahi-rich sharp-edged particles

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failed from the gamma primary phase. It is from grain to grain Orientation of the gamma primary phase changed.

In Fig. 3 are various large spherical MKM carbide particles to see »those through smaller, almost spherical violets consist of gamma primary phase. The grains contain many small, sharp-edged gamma primal precipitates. The unwanted ones needle-like phases that are present throughout the structure are of the Eigma-Eype. The presence this undesirable phase results in alloy instability and poor mechanical properties. the The mechanical properties become noticeable when .man sample no. 9 itt table 2 with the properties of the compares the alloy according to the invention.

When aigma-type needles form in the microstructure, then the properties are adversely affected because the alloying elements responsible for the solidification by Solid solutions are used to form needle-like phases. Thus, the strength decreases when Needles form and grow. Failure occurs due to excessive sliding and the needles act as excellent Levels on which sliding can take place. Bas means, the sooner phase the Eigma-Sype is present, the more greater is the resulting stability of the alloy «,

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Claims (5)

The differences in the microstructure become even more noticeable when the alloy has been tempered, i.e. when it has been exposed to elevated temperatures for a longer period of time. The presence of these undesirable secondary phases greatly reduces the stability of the alloy and thus limits its usefulness. In order for the alloy to maintain its stability it must have the correct JJv value. At the same time, the composition must have the necessary high mechanical strength properties and stress-cracking properties. Alloys with electron vacancy numbers below 1.9 do not have the required high temperature properties. If the electron vacancies are increased above 1.9, the required strength properties are better and the stability of the alloy remains satisfactory. The first noticeable transition from stability to the presence of harmful secondary phases occurs in the annealed state above an Nv of 2.5 .. In the pre-annealing heat-treated condition, the formation of the noxious phases usually occurs above a tinplate vacancy rate of 2.7. In addition, start at B_. of 2.5 the strength and ductility properties decrease. However, an alloy with an Nv number of 2.5 to 2.7 is still quite satisfactory for many applications found »who have a Ny in the Bore I γοη 2.3 to 2.5« 909937/0966 190A8U PAIEIIAHBPStlCHE! 1. Machinable nickel-based alloy for use up to an iDeiaprature of 1038 ° 0, characterized in that it consists of the following components: 0.25 to 0.4-5 wt .- # carbon, 0 to 2, 00 wt .- # manganese, 0 to 1.50 wt .- # silicon, 11.00 to 17.00 wt .- ^ chromium »8.00 to 12.00 wt .- # cobalt, 2.00 to 6, 50 wt. # Molybdenum, 4.00 to 8.00 wt. # Tungsten, 1.00 to 3.00 wt. # Tantalum, 4.00 to 5.00 wt up to 3.20 wt .- # titanium, 0.0005 to 0.030 wt ¹ ^ boron, 0.001 to 0.250 wt .- # zirconium, a maximum of 2.0 wt .- ^ iron, balance nickel. 2. Alloy according to claim 1, characterized in that it has an electron vacancy number of 1.9 to 2.7 «. ^: 3. An alloy according to Ansprudh 1 or 2, characterized in that oils comprises the following constituents: 0,30 to 0.40 percent - Kohlenetoff%, up to 1.00 wt .- # manganese, up to 1.00 parts by weight fS. Silicon, 11.00 to 13.00 wt .- # chromium, 9 _f 00 to 11.00 wt .- ^ cobalt, 2.50 to 3.50 wt .-? * Molybdenum, 5.50 to 6.50 wt .- # Tungsten, 1.25 to 1.75 wt. "? P 909837/0966 tantalum ,, Ms 4.45 4 ₉ * 7Q Grew »# Aluminiusi, 2.80 Ms 3.20 Titanium» 0.008 0.018 dew. bio-g _r from 0.005 to 0.150 boron zirconium, inasiffial 1 _r 0 wt _o - # Elsen, residual Mckel, 4 _"r alloy according to claim 3» characterized in that a iiie Elektrottenleerstellensah). In the range of 2.3 up to 2 ₅ 5 » 5 ο alloy according to one of the preceding claims, characterized in that 3ie to 0 ₉ 50 wt .- ^ contains mixed metal, the mixed metal axis a Geiaisch
consists of rare metal elements. 909837/0966 Blank page