DE1258114B - Process for the production of semi-finished products from a titanium-aluminum-vanadium alloy - Google Patents

Description

Process for the production of semi-finished products from a titanium-aluminum-vanadium alloy It is known that in titanium alloys the content of accompanying elements, in particular hydrogen, but also oxygen, nitrogen and carbon, is of exceptional importance for the mechanical and thermal properties and for the machinability of semi-finished product and material. Titanium-aluminum alloys with one or more alloying elements have already been described in German Auslegeschrift 1179 006, which does not belong to the state of the art, the aluminum content being 0.5 to 46 % and 0.5 to 40% / a of the following alloying elements: Vanadium, niobium, tantalum, zirconium and / or 0.5 to 15 % lead, 0.5 to 5% cobalt and optionally 0.25% to 5% copper and / or nickel, 0.5 to 25% tungsten, 0.25 to 3% silicon, 0.1 to 111/0 beryllium, 0.5 to 100/0 indium, 0.5 to 501, bismuth, 0.5 to 15% Silver, 0.05 to 1% boron, can be contained individually or in groups, namely in addition to the usual alloy companions carbon, oxygen; Nitrogen, chromium, iron, cerium, arsenic, sulfur, tellurium, phosphorus.

There are also not belonging to the state of the art Titanium-aluminum alloys have been proposed in the German patent 1,142,445 with from 0.25 to 7,50 / 0 aluminum and / or 0.25 to 160 /,) with tin in addition to one or several alloy elements in the form of 0.25 to 51) 10 bismuth or indium, 0.1 to 101) /, niobium, tantalum or zirconium, 0.1 to 300 /, vanadium, 0.1 to 15 % tungsten, 0.1 to less than .20 /, iron or cobalt, 0.1 to 1.5 ° / n nickel, 0.1 to 2.5 l) / 0.4 to 501, or 7.50 / 0 manganese, 0.1 to 2.50 / "more than 5 to 12.5 ° / n or optionally up to 1.8 ° / n chromium, 0.1 to 2.5l) /" 5 to 151) / "or optionally up to 200 /, molybdenum and on Alloy companions up to 0.3 % oxygen, up to 0.3 % carbon, up to 0.2 % nitrogen, the remainder at least 70/0 titanium.Parts made from these alloys still have a certain ductility after welding.

It is also a process for the production of heat-resistant materials from titanium alloys with 1 to 60/0 vanadium and / or molybdenum and an at least as high aluminum content, which is not part of the prior art, the subject of German patent 1107 947, whereby a casting of this composition is initially high is heated in the a / ß phase region. This leads to a grain growth of the continuous a-phase. The alloy is then quenched and aged. In this case, the annealing takes place for 4 to 24 hours at a temperature of 815 to 900 ° C, the aging takes place within 12 to 24 hours at 540 to 650 ° C.

These alloys leave a lot to be desired in terms of strength and extensibility or processability.

The method according to the invention is now based on very specific titanium-aluminum-vanadium alloys with a / ß-structure relatively narrow areas of the individual alloy elements with extraordinarily low proportion of alloying companions in the form of hydrogen, oxygen, nitrogen ' and carbon, which, due to their special composition, form a Heat treatment to improve their mechanical properties (strength and elongation), what is not possible with other titanium alloys. By the The method according to the invention achieves a very low ratio of yield strength to tensile strength. If the alloys treated according to the invention are tempered again, in this way a particularly high-strength, but ductile and processable semi-finished product is obtained.

The invention thus relates to the method for producing semi-finished products of high strength and ductility from a titanium-aluminum-vanadium alloy and is characterized in that an alloy of 2 to 8 % , preferably 2 to 7% aluminum, 1 to 10 ° / o, preferably 2 to 6 % vanadium and 0.001 to 0.003%, preferably to 0.021) /, hydrogen, 0.01 to 0.2l) /,) oxygen, 0.005 to 0.10 / 0 nitrogen and / or 0.01 to 0.25% carbon, the remainder titanium is used, the sum of oxygen + nitrogen -I- carbon not exceeding 0.5%, and that this alloy is heated to a temperature high in the a / ß- Phase area heated, quenched from this temperature, hot worked and aged for at least 1 h (h = hour) at 480 to 650 ° C. Alloys with 6 to 70%, aluminum and 4% vanadium are preferred. In the case of alloys with 4 to 8% aluminum and 2 to 5% vanadium, the heat treatment is always carried out at 540 to 650 ° C for 12 to 30 hours.

The semifinished product obtained according to the invention is distinguished by special features Strength, ductility and toughness, both at room temperature and in the Heat from. The alloys treated according to the invention can be regarded as pronounced refer to heat resistant. A particular advantage is the good weldability. That. welded semi-finished product has an excellent ductility when it is according to the invention has been treated. The relationship between the yield point and tensile strength lies extremely cheap.

According to the method according to the invention, the heat treatment takes place an alloy z. B. by melting a master alloy in the electrical Arc furnace was obtained. The master alloy serves as a consuming electrode; if necessary, the solidified melt can be removed from the arc furnace a second time be remelted in the same way. Any other way of manufacturing the alloys to be subjected to the process of the invention are hot rolling of optionally sintered shaped bodies made of metal powders in a protective gas atmosphere.

The strength of the alloys to be treated according to the invention is noticeably increased by a minimum content of 211 /, aluminum. The vanadium content of at least) ° / o leads to an improvement in strength and processability, a vanadium content above 1011/0 offers in terms of processability and strength no more advantages. The strength increases with increasing aluminum content and to a lesser extent with increasing vanadium content; the processability decreases with increasing aluminum content and increasing with increasing vanadium content. Particularly deformability is good with a vanadium content of at least about 3%. Preferred an alloy with 6 to 7% aluminum, 3 to 5% vanadium, the remainder titanium, Particularly preferred are those with 6% aluminum and 4% vanadium. Sheets an alloy with 2 to 5% aluminum and 3 to 1011/0 vanadium can be deform at about 260 ° C. Alloys of the preferred composition stand out characterized by a particularly good weldability.

The z. B. in the arc furnace melted alloy can at 760 to 927 ° C hot-rolled or hot-pressed at 816 to 1093 ° C. For improvement the mechanical properties of such a semi-finished product becomes high to a temperature held in the a / ß phase region for about 1 to 2 hours and then quickly cooled or quenched. The material obtained is characterized by a particularly favorable ratio of Yield point to tensile strength and therefore excellent processability in the heat, for example at about 260 ° C. The semi-finished product is then thermoformed and then aged for at least 1 hour at 480 to 650 ° C. One gets in this way again a very high ratio of yield point to tensile strength, but without observing a deterioration in elasticity.

With the method according to the invention it is therefore possible, on the one hand, to ensure excellent workability of the alloys and, on the other hand, to obtain a material which is characterized by particular strength and ductility. The special treatment conditions and the properties of the process products are shown in the following tables. Table 1 Alloy alloy ran g elements heat treatment o / 'Al o /' V A 6 2 1025 ° C 0.5h O 600 ° C 24h L B 6 '4 1025 0 C 0.5h O 6000C 24h L C 8 I 2 1025 ° C 0.5h O 600 ° C 24h L L = cooling in air. O = cooling in the oven. Table 2 shows the mechanical properties of a semi-finished product suitable for forging or plating, in each case at room temperature after the heat treatment specified in Table 1. Table 2 Vickers hardness elongation Alloy tensile strength 0.2 0 /, - yield point constriction ° / o modulus of elasticity (20 kg) (Test rod kg / mm2 kg / mm2 ° / 0 2.54 cm) kg / mm2 kg / rnm ' A 95.5 87.4 38.9 14 13 400 323 B 89.4 80 17 14 11920 304 C 95.5 85 14 6 12 100 313 Two alloys, namely alloy D with 6% aluminum and 2% vanadium, and alloy E with 6% aluminum and 4% vanadium, the remainder being titanium, were subjected to the heat treatment according to the invention, namely 1 Heat to 800 ° C h, cool in air, age at 500 ° C for 1 h and finally quench in water. The mechanical properties of these two alloys in sheet form are summarized in Table 3. Table 3 Alloy Test temperature Tensile strength 0.2% elongation Vickers hardness Smallest bending radius (aged) limit (test rod (10 kg) (sheet thickness) kg / mm 'kg / nun2 2.54 cm) kg / mm2 lengthways across D 27 ° C 102.5 81 12 345 3.0 3.5 370 ° C * 62.5 52.5 9 E 27 ° C 104 91.5 14 360 4.0 4.0 370 ° C * 75.5 62.5 9 * Welded. The preferred alloys with 4 to 80 / () aluminum, 2 to 51) 10 vanadium, the remainder titanium have superior strength and ductility at elevated temperatures on the order of e.g. B. 200 to 540 ° C. They are therefore particularly suitable for engines and components on aircraft. A 12 to 30 hour heat treatment at around 540 to 650 ° C (aging) results in highly heat-resistant alloys that retain their good properties even when exposed to temperature changes. The alloys F, G, H and J recorded in Table 4 had an aluminum content of 8%, the alloys F and H a vanadium content of 2%, and the G and J alloys 4% Vanadium. The heat treatment was carried out at 900 ° C. for 24 hours and quenching in water, tempering at 550 ° C. for 48 hours and cooling in air. The mechanical properties of the products obtained in this way at 425 and 550 ° C. are listed in Table 4 below. Table 4 Alloy tensile strength 0.2 ″ - yield point constriction elongation modulus of elasticity kg / MM2 kg / r = 2 % % kg / mm2 at 425 ° C F 75.5 59 30 18 10 500 G 81.5 66 60 22 9150 at 550 ° C H 55 36.6 43 20 9350 J 70.3 50 60 17 Alloys K and L, each with 8% aluminum, and alloy K 2% vanadium and alloy L 4% vanadium, were subjected to the heat treatment according to the invention, namely 24 h annealing at 900 ° C., cooling at the Air and tempering for 48 hours at 550 ° C and finally cooling in air. At a test temperature of 550 ° C., the creep strength was determined after 100 or 500 h based on a minimum creep speed of 0.1 ° / 0 / h or 0.01 ° / 0 / h. It was found that alloy K endured a breaking load of 31 kg / mm 2 after 100 hours and of 27 kg / mm 2 after 500 hours. The values for alloy L are 25.3 kg / mm2 at 100 h and 18.3 kg / mm2 at 500 h.

In a similar way, the alloys M with 6% aluminum and 2 % vanadium and alloy N with 6% aluminum and 4% vanadium were aged for 24 hours at 600.degree. C. and cooled in the air. This semifinished product was subjected to conditions such as occur during forging, namely 550 ° C., load 105.5 kg / mm 2, time 1000 h with a deformation per 2.54 cm in percent. A value of 1.6% was obtained for alloy M and a value of 4.7% for alloy N. Table 5 compares the mechanical properties before and after forging. Table 5 Before, afterwards Alloy tensile strength constriction elongation tensile strength constriction elongation kg / mm2 I % I % kg / min 2 ° / o ° / o M 96 38 14 90.5 27 14 N 100 38 17 98 40 15

Claims (1)

Claim: Process for the production of semi-finished products of high strength and ductility from a titanium-aluminum-vanadium alloy, characterized in that an alloy of 2 to 8%, preferably 2 to 7%, aluminum, 1 to 10 %, Preferably 2 to 6%, vanadium and 0.001 to 0.03%, preferably to 0.02%, hydrogen, 0.01 to 0.2% oxygen, 0.005 to 0, 10 /, nitrogen and / or 0.01 to 0.25% (, carbon, remainder titanium is used, whereby the sum of oxygen -f- nitrogen + carbon does not exceed 0.5%, and that this alloy has a Temperature high in 1 rx / ß-phase region, cooled quickly from this temperature or quenched, hot-formed and aged for at least 1 hour at 480 to 650 ° C. Considered publications: German Patent No. 718 822; »Excerpts of German Patent Applications ", Vol. 19, 1948, p. 368 (file number A 100194 VIa / 40b);" Journal of Metals ", Seetion I, Transactions of ATME, 6 (1954), N r. 3 (March 1954), pp. 367 to 376. Earlier patents considered: German Patents No. 1107 947, 1 142 445.