DE2206164A1 - Deep hardenable titanium-based alloy - Google Patents

Description

Deep hardenable alloy based on titanium

The invention relates to titanium-based alloys that are deeply hardenable and a superior combination have other properties.

In the titanium industry, the term “hardenability” is understood to be a measure of the depth and distribution of strength that is generated in a material by precipitation hardening, in contrast to the definition of this term in the steel industry, where it is used as a measure of depth and distribution of hardness produced in a material by quenching holds. A deeply hardenable alloy on titanium alloy or titanium alloy can be defined as an alloy whose stress

Patent attorneys Dipl.-Ιης. Martin Licht, Oipl.-Wirttch.-Ing. Axel Hantmann, Phyi graduate. Stbaitian Herrmann

S MÖNCHEN 2, THEtESIENSTRASSE 33 · Telephone: 2B1202 · Telegram address: Lipatli / Munich layer. Vereinibenk Munich, Zweijir. Otkar-von-Miller-Ring, toilet no. M2495 Poiftcheck account: Munich No. 163397

Oppenauer lOro: PATENT ADVOCATE DR. REINHOLD SCHMIDT

209835/0849

ο strength through hardening to a value of 98.4 kp / mm

or higher, in the middle of a 4-inch round cut. There is a need on a deeply hardenable alloy, which has a greater fracture toughness and a higher modulus of elasticity than Commercially available alloys «The toughness and strength of an alloy are inversely related. Accordingly, efforts to improve toughness lead to deterioration in strength. A method now recognized for determining toughness is described in ASTM Standard E-399-7OT, the by the American Society for Testing and Materials, Philadelphia, Penna ". The test attempt leads to a Kj value, measured in kp / mm ^ 2.5 ^ cm '. One known commercial alloy, namely Ti-6Al-6V-2Sn

has a specified K _T value of 28.1 kp / mm 1 / 12.54 cm '

'/ in small sections with a yield point of 112 kp / mm, however, the alloy cannot achieve this strength in large cuts. However, this alloy is one the best deep hardenable alpha-beta titanium alloys available to date. Beta titanium alloys or Titanium-based beta alloys have good hardenability and toughness, but a low modulus of elasticity,

4/2, which is usually less than 1.09 x 10 kg / cm, and low deformability · With all strength values an improved toughness is needed. Titan manufacturers have now researched a deeply hardenable alloy their Kj at a yield strength of 112 kp / mm

at least 38.7 kp / mm \) 2.54 cm ⁷ , the elastic

1 4/2

modulus of at least 1.2 χ 10 kp / cm and the area reduction over 12 % .

The object of the invention is therefore to create deeply hardenable titanium-based alloys which expand the properties sought above. These alloys on titanium base are said to belong to the alpha beet type "ad al" contain alloy elements aluainiua, molybdenum, chromium and sllieiaa in proportions that have been learned.

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«· 3 ■" ■

Furthermore, such alloys are intended to increase their Tensile strength and hardenability can also contain tin and / or zirconium in narrowly limited, maximum proportions

The invention thus relates to deeply hardenable titanium-based alloys which, with high yield strengths and a high modulus of elasticity, also have superior fracture toughness. For this purpose, it is proposed according to the invention to make up such alloys in percent by weight as follows: 5 to 6 % aluminum, 2 to 4 %

Chromium, 2 to 4 % molybdenum, 0.25 to 0.50 % silicon, remainder Titanium and incidental impurities.

With these elements alone, the alloys according to the invention have the desired toughness and the desired modulus of elasticity as well as a useful hardening capacity, which can be shown by the test results given below. Your tensile strength however, in dioken sections is not sufficient for certain applications. This Naohteil can by adding eliminate tin in an amount of up to 3% by weight and / or zirconium in an amount of up to 2% by weight. Of the maximum content of tin and zirconium together is about 4 wt .- #. In any case, the alloy corresponds to that Alpha-beta type.

To achieve the stated objectives, it is important that the alloys contain the special elements aluminum, chromium, molybdenum and silicon, and that these elements are represented in the above proportions. The alloys must contain at least 5% aluminum so that the required modulus of elasticity can be set, but the maximum is about «below 8 # if embrittlement is to be avoided. The those

209835/0849

220616A

Beta-phase promoting element · Chromium and molybdenum lead to the desired hardenability, toughness and the desired modulus of elasticity, without thereby eliminating the necessary deformability. Other elements promoting the beta phase, for example beryllium and boron, impair the deformability. Still other elements, such as iron, manganese, vanadium, columbium and tantalum impair the modulus of elasticity, while molybdenum and chromium have little or even slightly beneficial effects on the modulus of elasticity if they are added in the critical amounts just mentioned.Silicon improved in the used Share in connection with molybdenum the modulus of elasticity and the strength, without leading to an undesired alloy formation and a loss of toughness »Molybdenum also has a beneficial effect on increasing the solubility of silicon in beta-phase titanium. At least 2 % molybdenum is required for hardenability and to promote the solubility of the silicon. 3 % tin or 2% zirconium must not be exceeded, so that no undesired loss of fracture toughness occurs

The alloys can be either beta phase alloys or alpha-beta phase alloys. In the first case, these belong to the final hot-working steps Reductions at temperatures substantially above the beta phase transition of the alloy · Close in the second case the final hot working steps include reductions at temperatures all below the beta transition lie.

The diagram shown in the drawing shows gradient lines from which the relationship between the toughness and tensile strength of the above-mentioned, commercially available, deeply hardenable alloy Ti-6Al-6V-2Sn (I) ₉

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the beta-phase alloys Ti-6Al-2Mo-2Cr-0.25 Si and Ti-6Al-2Zr-2Sn-2Mo-2Cr-O _s 25Si (il) and the same alloys with alpha-beta phase (III) can be seen.

Line I shows that the commercially available alloy Ti-6Al-6v-2Sn has a K _T * value of approximately 42.2 kp / mm "J / 2 ₉ 5k cm with a lower yield point of less than 98.4 kp / mm owns.

Large sections of these alloys can be treated so

/ 2 for an acceptable yield point of 112 kp / mm

When small cuts of the alloy are treated to reduce the

/ 2 Raising the yield point to 112 kp / mm falls the KL. -Value to around 28.1 kp / mm "1 / 2.54 cm '. This course of the line lets Describe yourself mathematically by the following equation: J.

0.7 Kj _c + 0.545 St-Gr * 116

Lines II and III indicate that the novel alloys have K ^ values that are suitable for any The selected yield point is far above that of the commercially available alloy · With a yield point · of

/ 2 112 kp / mm, the alloys new-strength a K value _T from about 49.2 kp / mm ^ 2.54 cm when beta phase is present, while the K. value for the alpha-beta phase is about 38.7 kp / mm 7 2.54 cm ¹ Line I.

Table I below shows the results of those actually carried out with the novel alloy Experiments «The experiments numbered with 1, 3» 4 and 5 are those which were entered in the drawing figure. The tests were carried out on one inch sheet which was treated to meet the metal near the center of a 10.2 cm round material corresponded to "

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CD TABLE I.

2. EFFECT OF TREATMENT ON THE PROPERTIES OF DEEP HARDENING ALLOYS CM

No. Composition Heat Size Treatment

Ti-6Al-2Zr-2Sn- 935 ° C-i / 2 H-AC 2.54 cm

2Mo-2Cr-0.25Si 538 ° C-4 H-AC sheet metal

- ο

Ti-6Al-2Zr-2Sn- 935 ° C-l / 2 H-AC 2.54 cm 109.5 102 *

, 2Mo-O, 7Si 538 ° C-4 H-AC sheet metal 108 95.5 c,

vo co

I 3 Ti-6Al-2Zr-2Sn- 927 ° C-i / 2 H-AC 2.54 cm 122 114 "

2Mo-2Cr-O, 4Si 538 ° C-4 H-AC sheet metal 121.5 108.5 S

Ti-6Al-3Sn-2Mo- 936 ° C-1/2 H-AC 2.54 cm

2Cr-O, 25Si 538 ° C- 4H-AC sheet

Ti-6Al-2Mo-2Cr- 935 ° C-i / 2 H-AC 2.54 cm

0.25Si 538 ° C- 4H-AC sheet

fracture
border
kp / mm Stretch
border
kp / mm 117
122.5
109.5
108 112
110.5
102
95.5 122
121.5 114
108.5 117.5
115.5 111
103 no, 5
109 104.5
97

also TABLE I EFFECTS OF TREATMENT ON THE PROPERTIES OF DEEP TREATMENTABLE ALLOYS

No.

ro σ co CD Ca>

strain
% Surfaces
reduction
1" Elasticity
module _D
χ 10 ⁶ kp / ciT 12.5
10.2 37.5
17.4 1,270
1,270 13.0
10.0 37.3
24.8 1.263
1.278 11.5
9.0 29.1
14.5 1,270
1.254 12.5
12.8 37.6
20.1 1.248
1.254 16.5
10.0 49.1
27.0 1,270
1.235

a -

because thickness 2.5 kp / am ' ^s ' ^ 2.54 ce'

treatment

41.3 51.8

28.7 30.8

30.8 47.6

33.6 54.7

' Λ

70.7

/ 3

/ β

*, + β β

Experiment no. 2 shows low K ₁ values because the silicon content is too high. Test no. 5 shows excellent K ₁ values, but relatively low yield strength values, since the alloy here does not contain the strength-increasing elements tin and zirconium. Tests nos. 1, 3 and h show good overall properties, especially when the alloy is treated so that it is in the beta phase state.

The following Table II shows the results of tests on samples obtained from the middle of an OK, 75 cm thick round material for two alloys of the composition according to the invention, »The properties achieved corresponded the required requirements

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TABLE II

CTTI O

MECHANICAL PROPERTY VALUES IN THE MIDDLE OF HEAT-TREATED ROUND BARS

THICKNESS OF 10.75 cm

No.

Together
settlement rehearse Fracture-
borderline
kp / mm Stretch-elongation
limit %
kp / mm 10 Ti-6Al-2Zr-2Sn-
2Mo-2Cr-0.25Si along 126 111.5 8.5 across 126.5 113 9.0 Ti-6Al-2Mo-2Cr-
0.25 Si along 113.5 103 9.5 across 113 101

(A) Heat treatment: 935 ° C-i / 2 H-WQ;

538 ° C- h H-, X

still TABLE II

MECHANICAL PROPERTY VALUES IN THE MIDDLE OF HEAT-TREATED ROUND BARS

THICKNESS OF 10.75 cm

(A)

No.

Surfaces
reduction
% Elasticity 17.5 1.254 16.5 1.263 27.5 1.278 23.5 1,270

44.8
49.0

58.0
63.0

(A) Heat treatment 935? C - l / 2 H-WQj

538 ⁰ C - 4 H-AC 0.7K _Ic + 0.546 Str-Gr,

132 137.5

139 142

treatment

The alloys of the present invention described herein should not be confused with certain known alloys developed to improve creep resistance. For example, British Patent Specification 9 ^ 4.95 ^ discloses a creep resistant titanium-base alloy _for 2 to 4% aluminum, 3 to 7% of zirconium, 4 to 8% tin, 0.5 to 3 molybdenum, and 0.25 to 0 # , Contains 75% silicon. If desired, other elements, such as iron, cobalt, nickel, chromium, manganese, vanadium, beryllium, boron, niobium, antimony, tantalum, tungsten and wrought iron, can also be present in small amounts. The maximum aluminum content of k% is below the critical 5% minimum of the alloy according to the invention, which must be added in order to obtain the correct modulus of elasticity. The minimum tin and zirconium contents of 3 % and 4 % are above the critical maximum values of 3 % and 2 % in the alloy according to the invention and would lead to a disproportionately large loss of fracture toughness.

In U.S. Patent 2,893,864 are also described creep-resistant alloys that are similar in some respects to the UK patent Legieiraag above, but with broader ranges and have many conditions, most of which are altogether unsuitable for the purpose of the invention « In order to achieve the goal mentioned there, namely the achievement of an unusual creep resistance, however made no distinction between the effects of chromium and other elements promoting beta-phase formation or even just recognized Neither of the named two patent specifications contains any indication of the toughness or the modulus of elasticity of the alloy.

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Surprisingly, the invention suggests a superior combination of the last-mentioned to the person skilled in the art both properties offered by a special combination of elements of which previously assumed became that it is only optional, that is, optional must be ^ as well as by a critical adjustment of the content of aluminum, tin and zirconium.

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Claims (6)

- 13 PATENT CLAIMS 1. Deeply hardenable titanium-based alloy, characterized by the following composition in% by weight: 5 to 6 % aluminum, 2 to k fo chromium, 2 to 4% molybdenum, 0.25 Ms 0.50% silicon and the remainder titanium and insignificant impurities ", 2. Alloy according to claim 1, characterized in that the alloy additionally contains at least tin and zirconium contains, in the case of tin in an amount of up to 3% by weight? and for zirconium up to 2 wt .- ^, the maximum content of tin and zirconium together is 4% by weight. 3. Alloy according to claim 1, characterized in that that the alloy corresponds to the beta-phase type k. Alloy according to Claim 1, characterized in that the alloy corresponds to the alpha-beta phase type. 5 «Alloy according to claim 2, characterized by a Kj value of at least 38 _f 5 kp / mm ^ 2.54 cm with a yield point of 112 kp / mm and a modulus of elasticity 6/2 of at least 1.2 χ 10 kp / cm _o 6. Alloy according to claim 1, characterized by a modulus of elasticity of at least 1.2 χ 10 kp / cm, the relationship between the K _Ic - ¥ ert, expressed in 0.7 kp / mm γ 2.54 em 'and the yield point , expressed in 0.7 kp / mm ² is defined as follows: 0.7 K _Ic + 0.5 ^ 6 yield point X l6 _e 209835/0849 J * Blank page