DE1258605B - Titanium-based alloy - Google Patents

Description

Alloy based on titanium The invention relates to aluminum-containing alloys based on titanium and represents an improvement of the titanium alloys described in German Auslegeschrift 1179 006, which is not part of the prior art. These alloys consist of 0.5 to 46--0 /, - aluminum and one or more fl stabilizers, including 0.5 to 5 % cobalt, with these alloys possibly also -0.25 to 5 (l / . copper. and / or nickel and optionally from 0.25 to 311 /, Siliziuni and / or / may contain beryllium 0 '1 to 10, the remainder being at least 50% titanium.

Copper, nickel, cobalt, silicon and beryllium all belong to the group of so-called active eutectoid or compound-forming P stabilizers, i.e. . h "in their presence as an alloying additives in addition to titanium bilden.diese elements upon cooling to below the critical temperatures encryption; bonds and a microstructure, there is distributed from a titanium UNAE within DER a base ground connection components.

It has now been found that the usable additional amounts in these titanium-aluminum alloys, which contain one or more active, eutectoid-acting β-stabilizers such as copper, nickel or cobalt, are up to züi. 12 01, aluminum with up to 200 /, copper or up to 120 / each , nickel and cobalt can be increased.

The useful ones. Quantity ranges for these alloys are included. 0.5 to 12 0/0 aluminum, more than 5 to, # 20.0 /, copper, more than 5 to 12 9 / o cobalt and / or more than 5 to 12 0/0 nickel, while the remainder is made of titanium and Impurities exists.- With these alloys it is not possible. themselves. instead of the total or a partial amount. of aluminum, use tin, in amounts of about 3 percent by weight tin for 10 % aluminum, and within the useful range of 0.5 to 23 % tin. All these additives stabilizing the x-phase increase the resistance of titanium to deformation. The upper limit for these additives is 120 % for aluminum and 23% for tin. . -.

It has now been found that the series mentioned above, in particular the -kupferhaltigen alloys in many ways - ways has excellent properties: Compared to the previously known alloys titanium-based with high * a-Stabilisatoxanteil is considerably better your- hot workability. If the temperature ranges of the fl and x-ß phases are deterred, their hardness and strength increase far more. You own . excellent strength at elevated temperatures up to about 650'C, a high - modulus of elasticity and, in comparison to the previously known alloys, titanium-based, a high ratio of elastic modulus to the density. They have - especially when they are heat-treated below the -lower critical temperature - an excellent heat resistance; the lower critical temperature is the one that beta-phase in the x-stage and the at below which decay by - converting the existing eutectoid active ingredients compounds formed. The copper-containing alloys are the compounds Ti, Cu, which correspond to Fe3C in the iron-carbon diagram. This heat resistance is due to the fact that the logation is completely converted into x-titanium plus this compound. These alloys also have excellent creep strengths and excellent welding properties.

The heat-resistant form of these alloys is obtained either by slow cooling within the critical temperature range or by about 1/2 to 24 continuous annealing usually at a temperature which is about 25 to 55 ° C below the critical temperature. The longer this annealing treatment lasts, the softer the metal becomes.

Up to about 50111, the specified maximum amount of copper, cobalt and / or nickel is by up to 200 /, one or more of the metals molybdenum, vanadium, niobium and tantalum, up to 5 "/, manganese, up to 3.50 / "Iron and up to 120 / () chromium and / or tungsten replaced, with the minimum amount of copper, cobalt or nickel being more than 501 . If the alloy contains z. B. 100 /, copper, up to 20 "/, molybdenum, vanadium, niobium or tantalum, up to 12 % chromium and / or tungsten, up to 5 % manganese and up to 3.5% iron can be added.

These alloys are referred to as "o # -dispersoid" alloys for the reasons mentioned above and are basically ternary alloy systems that contain an alloy component, such as aluminum or tin, which stabilizes the oc phase, and an active eutectoid P stabilizer, such as copper , Nickel or cobalt, which forms an insoluble compound within the application temperature of these alloys, generally up to 650 ° C. Even more complicated alloys of this type can be produced for these purposes by adding two or more active eutectoid β-stabilizers. The basic structure, the two-phase structure consisting of o, -phase and distributed in it = connection components, remains unchanged.

These α-dispersoid alloys are particularly suitable for use at elevated temperatures. As already mentioned, they are usually two -phase compounds and consist of - a strong stable oc-phase and a compound phase distributed in it. The excellent properties at elevated temperatures can be attributed to the distribution of the hard dispersed phase.

The hot working processes used in the processing of these alloys play an important role as the properties of the alloys after heat treatment largely depend on the history of their manufacture. Let these alloys heat-deform within four temperature ranges. In the order of decreasing temperatures these are: the nurfl range, the two-phase oc-fl range, the three-phase a-p connection area and the two-phase x connection area.

For example, in the case of the Ti-Al-Cu alloys according to the present invention, the temperature of the heat treatment for the β-only range is from about 900.degree. C. to, usually at most .980.degree. C., for the two-phase oc-p area at about 845 to 900'C, for the three-phase ix-ß-connection area at about 800'C and for the two-phase o, # connection area below 800'C. The ingots from these Ti-Al-Cu alloys, -Pn are normally worked down by hammer forging at around 980 ° C and subsequent rolling or drop forging at around 925 ° C. These alloys normally experience a rather large reduction in cross-section either in the xp "temperature range (845 to 900'C) or in the% bond range (about 790'C), by about 60 " [,.

The critical temperature for these alloys will vary with the addition of the active eutectoid fl-rod. T for the copper-containing alloys it is about 800 ° C, for the nickel- containing alloys about 770 ° C and for the cobalt- containing alloys about 680 ° C. As has already been mentioned for the heat treatment of the o # siliconization phase, these alloys are all treated about 25 to 55 ° C. below the critical temperature. The β transition temperature of these alloys fluctuates somewhat depending on the composition of the alloy and is, for any given composition, the lowest temperature above which the alloy is alone in the α phase. The most favorable temperature conditions for quenching these alloys from the P phase consists in heating them to about 25 to 55 ° C. above the P transition temperature and then quenching them. For the copper-containing alloys, the most favorable quenching range for the alloys quenched from the f1 phase is around 815 to 1010 ° C and from the "# -p field in the presence of aluminum around 860 to 875 ° C, for alloys with Tin instead of aluminum, however, at around 810 to 845 ° C.

The total content of the oc stabilizers aluminum and tin present in these alloys should be kept between 0.5 and 230 /, taking into account the above-mentioned upper limits for the individual elements , and some in the vicinity of the upper limit of this amount, the others are present in correspondingly smaller amounts within the permissible range.

The ratio of the amount of the compound-forming β-stabilizer is preferably Copper, nickel or cobalt to the tx-Stabüisatoreii so that if the amount of the fl stabilizer is at the upper limit of its allowable range, the amount of the α stabilizers is at the lower limit, and vice versa.

In these alloys, the ß-phase formed above the critical temperature changes with rapid quenching, e.g. B. in water, completely in a martensite-like shape and a fine eutectoid. to, with slower cooling from above the critical temperature, z. B. by quenching in oil or cooling in oil, in a mixture of oc-titanium and compounds consisting of eutectoid decomposition products, i.e. in these alloys the β-phase is not retained when quenching from above the critical temperature, and also the ß-conversion is associated with a significant increase in hardness and tensile strength.

That which arises during the quenching of titanium alloys of this type Martensite-like structure is very similar to that in steel quenching from the austenite temperature range preserved martensite. The martensite created in this way during the quenching is achieved by subsequent tempering in the temperature range of the (y.-compound phase converted into a microstructure, which consists of a fine dispersion of the ß-EutQctoid decay components, z. B. of TiaCu, titanium ylide, etc., consists in an o # -titanium basic structure. This The process is similar to the melting of steel, in which the quenching effect Martensite in a fine dispersion of Fe, C in a ferrite matrix. transforms.

To convert these titanium alloys into a martensite-like structure, relatively high temperatures are required, which are not quite 25 to 55 ° C below the critical temperature. For the copper-like alloys, the hardening range is e.g. B. about 540 to 760'C, so compared to the hardening range of the steel, about 400 to 540'C, is quite high. As a result of this tempering of the titanium alloys, these are converted into a state of α-titanium and dispersed connection components that is suitable for subsequent use at elevated temperatures.

The high softening temperature of these alloys makes them suitable for areas of use suitable at high temperature, e.g. B. for fan blades of jet engine compressors, Bolts for compressor housings, liners and housings for jet engine combustion chambers.

As an example of the properties obtainable by quenching and tempering in these alloys, in particular the copper-containing alloys, the values of an alloy of about 411 /, aluminum, 60/0 copper and the remainder of technically pure titanium are given, which in the case of water quenching range from 860 to 870 ' C has a Vickers hardness of 375 kg / mm2, a tensile strength of 133.6 kg / mm2, a 0.2 limit of 91.4 kg / mm2, a cross-section reduction of about 3001, an elongation of about 10 "and a minimum radius of curvature of about 4T. (The minimum radius of curvature T is the radius, expressed as a multiple of the specimen thickness, to which the specimen can be bent to an angle of 75 ' without breaking.) These properties have never been used side by side - as far as known - before achieved by titanium alloys, if this alloy is tempered for about 1 to 16 hours at about 700 ° C. , the Vickers hardness drops from about 375 to 330 to 350, but the De determined after quenching hnbarkeit of 4T increases by annealing at T 3. In this state, extremely good heat resistance and strength at elevated temperatures for working conditions of up to about 315 to 540 ° C can be determined.

The following table I shows the influence of the various heat treatments mentioned above on the mechanical properties of a typical alloy according to the present invention, which consists of 4 "/, aluminum, 6% copper, the remainder titanium, compared to the corresponding binary alloy without, x -Stabilizer, which therefore only contains 6 "/, copper and the remainder titanium and is not the subject. the invention counts, An examination of the data set out in Table I shows that the highest ductility could be achieved when the alloys were heat treated by annealing up to the oc bonding phase. By heat treatment with cooling from the ß-phase in the furnace, a firmer, less ductile structure is obtained than that produced by annealing up to the a-compound phase. In the case of the Ti-6Cu alloy, the copper acts both as a stabilizer and as a bonding agent. In the Ti-4A1-6Cu alloy, the aluminum serves as an o # stabilizer, while the copper is mainly present because of its compound-forming property. The deterrence of these alloys to produce a martensitic oc structure leads to an increase in strength and a decrease in ductility. As expected, the increase in strength in the case of the quenching from the β-only range is greater than that from the x-β range.

In the following Table II, the mechanical properties are typically titanium-aluminum-copper alloys listed according to the invention after tempering up to the x-compound phase währeud table 111, the corresponding data FILR these alloys after quenching from the beta phase shows. It can be seen from the data in Table U that the strength and elasticity properties of the Ti-Al-Cu alloys annealed to the compound phase depend mainly on the alloy composition, with an increase in the total content of Al and Cu causes strength and a decrease in ductility. The values for elongation, hardness, yield point and cross-sectional reduction justify the conclusion that by increasing the content of Al. -and Cu can increase the strength with a simultaneous decrease in ductility.

A comparison of the corresponding data for the Ti-Al-Cu alloys quenched from the β-phase in Table III with the values for these alloys after annealing up to the α-compound phase (see Table II) shows that only the most highly alloyed samples exhibited strength and elongation properties after quenching from the -fl phase. which could be compared with those of the corresponding alloys annealed to the x-bonding phase. - The difference between the two types of heat treatment is for the lower alloyed alloys, i. H. those with smaller non-titanium content, larger. From this it can be concluded that heat treatments with quenching or quenching and subsequent tempering are only advantageous for the most highly alloyed systems of this series.

The excellent properties of the Ti-Al-Cu alloys annealed to the cc compound phase at elevated temperatures, e.g. B. at 540'C, are shown by the test results listed in Table IV below. Table IV Tensile strength properties the annealed up to the oc compound phase Ti-Al-Cu alloys at increased Temperature (540'C) * Tear together cross-sectional Settlement Estimated strength- Deh- reducing- (Weight 0.2 limit ranks percent) Rest titanium kg / min2 kg / rim2 0 /, 4A1 - 6Cu 38.7 50.6 36 90 4A1-8Cu 40.1 58.4 35 74 4A1 - 10Cu 39.4 54.1 45 87 4A1 - 12Cu - 45.7 - - 6Ä1 - 6Cu 57.6 72.4 40 74 8A1-6Cu 67.5 85.8 40 66 10A1 - 6 Cu 65.4 83.0 50 75 12A1-6Cu - 68.9 28 25 12A1-8Cu 45.0 75.2 5 15 For the tests, both bars and sheet metal samples used. Most of the values given come from a single sample. From the data in Table IV above, it can be seen that the addition of other metals markedly increases the tensile strength of the titanium at elevated temperature. It turns out that the beneficial effects of copper depend entirely on the simultaneous content of the oc stabilizer, namely aluminum. If the aluminum content is low, the addition of copper results in a large increase in strength at elevated temperatures. However, if the aluminum content is increased, the addition of copper proves to be less advantageous. So z. B. improve an alloy with 2 weight percent aluminum by adding copper by up to 100 /. Since binary titanium-aluminum alloys with a moderate aluminum content are difficult to process, the favorable influence of copper additions on the strength at elevated temperatures is particularly advantageous in the case of forged alloys of this series.

The results of creep rupture tests with the Ti-Al-Cu alloys are listed in Table V below. It can be seen from these data that as the copper content increases, the elongation at break properties. these alloys get much better; for copper additions of about 8 0 / "and above are obtained even unusually good elongation at break properties. Table V Results of the creep rupture tests when annealed up to the x-connection phase Ti-Al-Cu alloys Together setting test fracture elongation (Weight temperature at the time percent) train Rest titanium c kg / nu-n2 hours 0 /, 4A1 - 6Cu 425 56.3 16.1 14.7 4A1 - 6 Cu 425 52.7 48 23.0 4A1 - 8 Cu 425 56.3 150.1 5.5 4A1 - 10Cu 425 > 56.3 362.0 *> 6.8 * * The experiment was discontinued after 362 hours. The data listed in Table VI below show the effect of replacing all or part of the aluminum with the # x stabilizer tin in copper-containing a-dispersoid alloys. The properties of these alloys containing Sn annealed to the o # compound phase are quite similar to those of the Ti-Al-Cu alloys under the same heat treatment conditions. It turns out that these x-substituted alloys, after quenching from the β phase, have approximately the same mechanical properties as the corresponding Ti-Al-Cu alloys; this equivalence is retained even at elevated temperatures. The elongation at break tests showed that even further improvements in elongation at break properties can be achieved by increasing the x stabilizer content corresponding to the amount of aluminum above 40%. The aging tests show that these oc-substituted alloys have good heat resistance after annealing up to the a-compound phase.

In Tables VII to X below, the effect of replacing the copper in the above-mentioned copper-containing x-dispersoid alloys with nickel or cobalt is shown. Table VII Average mechanical properties of those annealed to the a-compound phase Ti-Al alloys with Co, Ni additions Composition 0.2 limit tensile strength, elongation, cross-sectional Vickers hardness (Percent by weight) reduction T Rest titanium kg / mm2 kg / MM2 0/0 0/0 kg / now ' 4A1 - 6 Co 89.3 102.6 9 12 356 3.8 4A1 - 6M 75.9 85.8 4 12 331 8.7 Table IX Mechanical properties at increased Usage temperature (540'C) of up to oc compound phase annealed Ti-Al alloys with Cu, Ni or Co additions Together, tear, cross-sectional settlement 0.2- firm- deh- reducing- (Weight limit reduction Percent) Remainder titanium kg / mm 'kg / mm2 0 /, 0/0 4A1-6Co - 40.1 44 87 -4A1 - 6Ni - 3753 53 84 For comparison 4A1 - 6Cu. 39.7 50.6 36 90 Table X Influence of a 24-hour heating to 425 0 C on the Hardness and bending properties of the up to cc bonding phase annealed Ti-Al alloys with Ni or co-addition Together- enforcement before the increase (Weight heating the heating Percent) 1 Vickers- 1 Vickers- Remaining titanium hardness T hardness 4A1-6Ni 94 331 "'+0 6 -2 4A1 - 6Col 2: 8356 + 7, '2 +55 -1: Can instead of up to the oc connection phase also up to _a-ß-additional metal phase must be annealed. From the data compiled in Table VII on the mechanical properties of these alloys, u after annealing up to the formation of the oc compound phase, it can be seen that the Ti-Al-Co alloys, with the exception of Ti - Al - Ni, have the Ti -Al-Cu alloys are equivalent. The alloys with nickel or cobalt are additional through deterrence gen-Cigend well curable. The combination of high hardness and good flexural properties that occurs in the Ti-A1-Co alloys after quenching appears to be particularly favorable.

The data on the tensile properties at elevated temperature in Table IX show that on an equal weight basis both cobalt as well as nickel to the copper in terms of their effect on the properties is somewhat inferior to increased temperature. The addition of a small amount of manganese proves beneficial in this regard.

The annealing tests given in Table X show that the Ti-Al-Ni alloys are reasonably heat-resistant (thermiscii stable). The Ti-Al-Co alloys, however, show certain signs of instability. The properties of the Ti-Al-Ni alloys at ordinary temperature show that nickel is not a favorable additional element for a-dispersoid alloys. - If a small part of the copper is replaced by manganese, the properties of the alloys in the. Somewhat better compared to the corresponding Ti-Al-Cu alloys; however, the manganese-containing alloys are not heat-resistant. - The feature with which the alloys according to the invention differ from those of the references consists primarily in the claimed quantity ranges of the metals copper, cobalt and nickel as alloy constituents. The lower limits of the invention, the added amounts of these metals are all above the f or the same metals in the cited documents specified amounts.

French Patent 1070 589 as well as the USA. Patent 2,669,513 describes an alloy having a high content of lob of 501, the maximum level of copper mentioned in the USA. Patent 2,622,023 alloy is 2 0 / "while in the British Patent 677,413 does not contain any copper, cobalt or nickel at all.

How out on top, the hot ductility of the alloys of the invention compared to the known is - alloys titanium-based stabilizer with high proportion significantly better. If the temperature ranges of the ß and oc-ß phases are deterred, their hardness and strength increase far more. They have excellent strength at elevated temperatures of up to about 650 ° C., a high modulus of elasticity and, compared to the previously known alloys based on titanium, a high ratio of modulus of elasticity to density. They have - especially if they are heat-treated below the lower critical temperature - an excellent heat resistance.

Claims (2)

Claims: 1. Alloy based on titanium, consisting of 0.5 to 120 /, aluminum and more than 5 to 200 /, copper, more than 5 to 120 /, cobalt and / or more than 5 to 12 0 /, nickel, the rest Titanium and inevitable impurities. 2. Alloy according to claim 1, characterized in that some or all of the aluminum is replaced by tin, in a proportion of about 3 percent by weight of tin for 1 percent by weight of aluminum, within the limits of 0.5 to 23 0 / , Tin. 3. Alloy according to claim 1 or 2, characterized in that up to about half of the specified maximum amount of copper, cobalt and / or nickel by up to 20 0 /, one or more of the metals molybdenum, vanadium, niobium and tantalum, up to to 5 manganese, up to 3.5 iron, and are to be replaced to 12 chromium and / or tungsten "/, wherein the minimum amount of copper, cobalt or nickel / alloy 4 is more than 5 0th according to claim 3, characterized characterized in that they are used as a further compound-forming ß-stabilizer 0.25 to 3 0/0 silicon or 0.1 to 2 "/, beryllium. contains. 5 .. Alloy according to one of claims 1 to 4, characterized in that the metals of the oc stabilizers aluminum or tin are present in the greater amount of their permissible range, if the ß stabilizers nickel, cobalt or copper, optionally and silicon. or beryllium. are present in the smaller amount of their allowable range, and vice versa. Documents considered: French Patent No. 1070 589; British Patent No. 677,413. USA. Patents No. 2622023, 2 661 286, 2,669,513th Contemplated prior patents. German Patent No. 1082 418, 1120153, 1142445, 1163 556th.