CN104018028B - A kind of high alumina height silicon cast titanium alloy - Google Patents

Abstract

A high-alumina and high-silicon cast titanium alloy, more specifically relates to a high-temperature, high-strength cast titanium alloy containing Ti, Al, Si, B, Mo, Nb, V, Ta and Zr. The mass percentage distribution ratio of each element in the alloy of the present invention is: Al 7.2-9.5%, Si 0.8-1.8%, Zr 0.5-3.5%, V 0.5-3%, Mo 0.1-4.5%, Nb 0.1-4.5%, Ta 0.1-3.5%, the rest is Ti, incidental elements and unavoidable impurities. In order to further improve the weldability of the alloy, the alloy composition of the present invention is adjusted to only contain Ti, Al, Si, Mo, Nb, V and Zr. For parts with extremely strict working temperature requirements, the material of the present invention can also be adjusted to contain Ti, Al, Si, Mo, Nb, V and Ta. It can be widely used in parts requiring thermal strength, oxidation resistance, wear resistance and corrosion resistance in the fields of automobiles, ships, aerospace and energy.

Description

A high-aluminum high-silicon cast titanium alloy

technical field

The invention relates to a cast titanium alloy containing high aluminum and high silicon, more particularly to a high-temperature, high-strength cast titanium alloy containing Ti, Al, Si, B, Mo, Nb, V, Ta, Zr and rare earth elements.

Background technique

Titanium alloys have been widely used in the fields of aerospace, ships, automobiles, chemicals, medical equipment and sporting goods. As far as the service temperature of titanium alloy is concerned, the maximum working temperature of the current titanium alloy has been increased from the initial 350°C to 650°C. The United States, Britain, Russia and other countries have developed Ti-1100, IMI834, BT36 and other alloys with working temperatures ranging from 550°C to 600°C. The nominal composition of Ti-1100 is Ti-6Al-2.75Sn-4Zr-0.45Mo-0.5Si , is developed on the basis of Ti-6Al-2Sn-4Zr-2Mo by adding a small amount of Si. The nominal composition of the BT36 alloy developed in Russia is Ti-6.2Al-2Sn-3.6Zr-0.7Mo-5.0W-0.15Si-0.1Y. IMI834 is a high-temperature titanium alloy successfully developed by the British IMI company in 1984. Its nominal composition is Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.35Si-0.06C. The alloy is a medium-strength (σb: 1050MPa) near α-type high-temperature titanium alloy, which has the best matching of excellent creep, fatigue and tensile strength properties, and can be used under high temperature conditions of 600 ° C. It is currently the highest temperature titanium alloy in Europe and the United States. .

China has developed Ti600 and Ti60 alloys used at 600°C. The nominal composition (weight percent) of Ti60 alloy is Ti-5.6Al-4.8Sn-2.0Zr-1.0Mo-0.85Nd-0.34Si, and the nominal composition (weight percent) of Ti600 alloy is It is Ti-5.8Al-4.0Sn-4.0Zr-0.7Nb-1.5Ta-0.4Si-0.06C. A Ti65 alloy working at 650°C has also been developed with a nominal composition of Ti-6Al-4Sn-0.5Mo-0.4Nb-2.5Ta-0.4Si-0.06C. In order to further increase the operating temperature, Ti-Si-Al-Zr alloys (such as Ti-4Si-(3-5)Al-5Zr) have been developed abroad, and the operating temperature of this alloy system is expected to increase to 700-800°C. However, due to the formation of silicides, the alloy has very low plasticity, is very sensitive to stress concentration, and has low fracture toughness, which cannot meet the high fatigue performance requirements of high-temperature structural parts.

The publication number is CN1121359, the publication date is April 24, 1996, and the patent document named "titanium-based composite material" discloses a titanium-based composite material with a eutectic titanium alloy reinforcement phase, which contains silicon , aluminum, zirconium, manganese, chromium, molybdenum, carbon, iron, boron, cobalt, nickel, germanium and copper at least one element.

The publication number is CN200910114058, and the publication date is May 13, 2009. The patent document titled "In-situ Rare Earth Oxide Reinforced Titanium-Silicon Alloy Composite Material" discloses an in-situ self-generated rare earth oxide-reinforced titanium-silicon alloy composite material. Material, its raw material components are by weight percentage: Ti74.40-88.32%, Si0.614-5.406%, SiO ₂ 2.213-5.532%, La6.821-17.054%; or Ti74.40-88.32%, Si0.696 -5.406%, SiO ₂ 2.143-5.357%, Nd6.859-17.147%; or Ti79.05-90.24%, Si0.602-5.461%, SiO ₂ 2.395-5.987%, Y4.725-11.812%. The elastic modulus and compressive strength of the composite material are 5230-9280MPa and 102-467MPa respectively.

The publication number is CN101497952A, the publication date is August 5, 2009, and the name is "a high-strength high-temperature oxidation-resistant titanium-silicon alloy". The raw material composition and content of the alloy are as follows: Ti78.87-88.3 %, Si7.33-8.2%, Al and/or Nb2.8-12.3%, its compressive strength can reach 1498-1828MPa, and the oxidation weight gain of the alloy is less at a high temperature of 800-1000°C, and the oxide film formed on the surface of the alloy The denseness can protect the alloy very well, and the alloy has good processing performance, does not contain rare and precious metals, and has low manufacturing cost.

The publication number is CN102321833A, and the publication date is January 18, 2012. The patent document titled "A Al-Ti-Si Alloy Target and Its Preparation Method" states that the provided Al-Ti-Si alloy target consists of (mass percentage) It is made of 5-90% aluminum, 5-90% titanium, and 1-30% silicon. The aluminum-titanium-silicon alloy target is made by hot pressing and sintering. The aluminum-titanium-silicon alloy target has uniform composition, high relative density and low production cost.

The publication number is CN201210203747, and the publication date is December 3, 2012. The patent document named "a method for manufacturing a titanium-silicon alloy target" discloses a method for manufacturing a titanium-silicon alloy target. Titanium powder and titanium powder are used as raw materials, mechanically mixed according to a certain ratio, loaded into graphite molds, and sintered by vacuum induction hot pressing to produce titanium-silicon alloy targets with different compositions and sizes. The titanium-silicon alloy target prepared by the above method has the characteristics of fine grain, uniform composition, no segregation, low cost, high density and suitable for large-scale production.

The publication number is CN103710572A, and the publication date is November 11, 2013. The patent document titled "a cast Ti-Si-Al-based high-temperature high-strength alloy" discloses a high-temperature high-strength alloy containing an intermetallic compound reinforcement phase. Cast Ti-Si-Al alloy, the alloy contains (weight percent) Si4.5-8.5%, Al2.5-9.5%, at least one element selected from Mo, Nb, Ta, V and Zr elements, the content is 0.1- 2.5%, Ti balance. The tensile strength of the Ti-Si-Al alloy designed according to the invention is greater than 800MPa and 550MPa at room temperature and 500°C respectively.

The publication number is CN103556000A, the publication date is February 5, 2014, and the name is "Ti-Si-Al-based alloy containing rare earth and intermetallic compound reinforcement phase", which discloses this kind of alloy containing rare earth and intermetallic compound reinforcement phase. Ti-Si-Al-based alloy, by adding an appropriate amount of rare earth elements RE (RE = Y, La, Ce, Sm, Gd, Dy, Ho, Er), the Ti-Si-Al alloy can obtain a tensile strength exceeding 900MPa High strength and meet the use environment above 500 ℃.

The publication number is CN103555999A, the publication date is February 5, 2014, and the name is "a high-strength cast Ti-Si-Al-B-Zr-based alloy", which discloses a cast Ti-Si-Al-B-Zr-based alloy containing an intermetallic compound reinforcement phase. Si-Al-B-Zr alloy, the alloy composition (weight percentage) is: Si3.5-7.2%, Al3-8.5%, B0.01-1.5%, Zr0.01-3%, Ti balance.

Contents of the invention

The purpose of the patent of the present invention is to provide a cast Ti-Si eutectic composite material with high strength, wear resistance and oxidation resistance above 500°C. As a new type of lightweight casting alloy, the alloy can be widely used in parts requiring thermal strength, oxidation resistance, wear resistance and corrosion resistance in the fields of automobiles, ships, aerospace and energy.

According to the above purpose, the present invention relates to a plastic titanium alloy containing high aluminum and high silicon. By adding Al, Si, B, Mo, Nb, V, Ta and Zr, the alloy can obtain good high temperature strengthening, high temperature oxidation resistance and high temperature resistance. Grinding effect. The mass percentage distribution ratio of each element in the alloy of the present invention is: Al7.2-9.5%, Si0.8-1.8%, Zr0.5-3.5%, V0.5-3%, Mo0.1-4.5%, Nb0. 1-4.5%, Ta0.1-3.5%, and the rest are Ti, incidental elements and unavoidable impurities. In order to further improve the weldability of the alloy, the alloy composition of the present invention is adjusted to only contain Ti, Al, Si, Mo, Nb, V and Zr. For parts with extremely strict working temperature requirements, the composite material of the present invention can be further adjusted to contain Ti, Al, Si, Mo, Nb, V and Ta.

The composition design principles of the above chemical elements are as follows:

In order to balance the thermal strength, fatigue performance, plasticity and thermal stability of superalloys, the content of Al in traditional Ti alloys is generally controlled below 6%, and about 4% of Sn and about 4% of Zr are added to supplement the strengthening effect. , the Al equivalent of the alloy is controlled at the level of 8.5-9%. In the present invention, the strengthening method of the alloy adopts the precipitation of Ti3Al phase in the α-phase matrix instead of the traditional solid solution strengthening method, so the content _of Al in the alloy is increased to 7.2-9.5%. In order to reasonably control the casting flowability and welding performance of the alloy, the content of Al in the alloy is preferably 7.5-8.5%.

Si is a very important element in high-temperature titanium alloys, and usually high-temperature Ti alloys contain 0.1-0.5% Si. In the present invention, the main purpose of adding Si is to form a titanium-silicon ceramic phase through eutectic reaction, so as to further enhance the high-temperature strength of the titanium alloy and improve the high-temperature wear resistance. Therefore, the content of Si in the composite material of the present invention is selected to be 0.8-1.8%. In order to reasonably control the casting flowability and welding performance of the alloy, the content of Si in the alloy is preferably 1.05-1.6%.

The compressive strength and plasticity of Ti-Si alloy can be greatly improved by adding a small amount of B. The study found that in the Ti-Si eutectic alloy, when 0.21at% B was added, the compressive strength and plasticity of the alloy increased by 26% and 480% compared with the Ti-Si binary eutectic. B can also significantly affect the growth of primary dendrites during cooling of the hypoeutectic Ti-5wt%Si alloy, thereby changing the dendrite morphology in the microstructure. Therefore, another object of the present invention is to refine α-Ti dendrites, Ti ₅ Si ₃ or Ti ₃ Si intermetallic compounds by adding an appropriate amount of B element to obtain excellent comprehensive mechanical properties. The preferred amount of B added in the alloy is : 0.01-0.25%.

V is one of the most important alloying elements. This alloying element can exist in the form of solid solution and can also promote the formation of new alloy phases. V is a β-phase stable element. Therefore, the purpose of adding V is to properly obtain a certain amount of β phase, so as to regulate the balance of α and β phases in the alloy matrix. According to specific application requirements, by adding different V elements, a good match between the strength and plasticity of the composite material can be achieved. It is beneficial to improve the high temperature creep and durability performance of the alloy. In the present invention, the preferred content of V is 0.5-2.5%, so as to control the two-phase balance of α and β of the alloy matrix.

The purpose of adding Mo, Nb and Ta in the present invention is to improve the high-temperature strength of the alloy. Studies have shown that Mo, Nb and Ta are the most effective elements for high-temperature strengthening of the alloy, and they are obtained by adding Nb and Ta to Ti60 and Ti65 respectively. These three elements are the same elements as the β-Ti lattice, can be infinitely miscible with β-Ti, and have limited solubility in α-Ti. Since Mo, Nb, Ta and β-Ti have the same lattice, these elements can be dissolved into β-Ti in a large amount by substitution, resulting in small lattice distortion. Therefore, these alloy elements can not only produce strengthening effect, but also High plasticity can be maintained. These elements also have an important feature, they have non-eutectoid or inclusion reaction with Ti to form brittle phases, so the structure stability of the alloy is good, which is conducive to improving the creep resistance and durability of the composite material, which is beneficial to the alloy in Critical when used at high temperatures. In order to control the segregation of the alloying content on the actual pouring and cost control, Mo0.1%-2.5%, Nb0.1%-3.5%, and Ta0.1%-1.5% are preferred.

Zr and α-Ti have the same lattice type, and are infinitely miscible with α-Ti, so Zr elements can be dissolved into α-Ti in a large amount by substitution, resulting in lattice distortion. Elements that are not affected by the transformation are not obvious. This element improves the strength of α-Ti and also improves the thermal strength of the alloy. They are also beneficial to pressure processing and welding without greatly reducing the plasticity. The preferred content of Zr in the present invention is 1.0-2.5%.

On the basis of Ti-Si-Al, rare earth elements (RE=Y, La, Ce, Sm, Gd) are added to comprehensively improve the mechanical properties of the alloy. The reason for choosing to add these two types of elements is that rare earth elements (RE=Y, La, Ce, Sm, Gd) have the characteristics of large atomic radius and high activity. Studies have shown that rare earth elements can enter Ti-Si alloys Ti ₅ Si ₃ phases, forming Ti ₅ (Si,RE) ₃ , thus greatly improving the strength of the alloy. The study also found that adding a small amount of rare earth to the Ti-based alloy can significantly refine the grains and improve the mechanical properties, processing properties, welding properties and corrosion resistance of the material.

In summary, the composition design principle of the present invention is to form Ti ₃ Al phase and titanium silicon compound phase by adding high content of Al and Si to improve the high temperature strength and wear resistance of the alloy, and add B to refine the titanium silicon compound phase And the α-Ti matrix is precipitated first. Solid solution strengthening is achieved by adding V and Zr, and the alloy has good high temperature oxidation resistance and high temperature stability by adding Mo, Nb and Ta.

The titanium alloy of the present invention has the following advantages:

(1) It has excellent strength and toughness at room temperature.

(2) Due to the formation of Ti ₃ Al phase and titanium silicon compound phase in the alloy, the alloy has excellent wear resistance.

(3) The alloy contains more than 7% aluminum, so the alloy has good corrosion resistance and oxidation resistance.

(4) It has excellent mechanical properties and wear resistance above 500°C, suitable for the manufacture of high-temperature components, and can meet the requirements of high-temperature, wear-resistant and corrosion-resistant parts in the fields of aerospace, automobiles and ships.

(5) The titanium alloy of the present invention has a simple processing process, does not require special techniques and equipment, and can be produced using traditional preparation equipment and techniques.

Attached to the manual:

The room temperature tensile properties of accompanying drawing 1 embodiment 2 alloy.

Figure 2 shows the tensile properties of the alloy in Example 2 at 500°C.

Figure 3 shows the tensile properties of the alloy in Example 3 at 500°C.

Figure 4 shows the room temperature tensile properties of the alloy of Example 4.

Figure 5 shows the room temperature tensile properties of the alloy of Example 5.

detailed description

Examples 1-9

Casting method 1: The metal raw materials used to prepare the master alloy are all pure metal elemental elements with a purity greater than 99.9%, and the ingredients are formulated according to the chemical composition of the alloy. The alloy melting equipment adopts a high vacuum arc melting furnace, and the vacuum is higher than 5×10 ^{- 3} Pa, arc melting is carried out under an argon protective atmosphere, and after the master alloy is melted, the melt is suction-cast from the crucible into a water-cooled copper mold to form a rod with a diameter of 10mm.

Casting method 2: The metal raw materials used in the preparation of the master alloy are all pure metal elemental elements with a purity greater than 99.9%. The ingredients are formulated according to the chemical composition of the alloy and melted in a suspension melting furnace. The crucible is a water-cooled copper crucible and the melting vacuum is 0.01- 1Pa, the frequency of the suspension furnace is 8000Hz, the melting current is 100-500A, and the voltage is 100-380V. After the strip alloy is melted, it is poured into a copper mold with a diameter of 45 mm and a length of 300 mm.

Casting method 3, prepared according to weight percentage, mixed uniformly and pressed into electrodes, and then vacuum smelted in a vacuum consumable electrode electric arc furnace. At this time, the smelting vacuum degree is 0.01-1Pa, the arc voltage is 32-36V, and the arc current is 5000- 8000A, and then the Ti-Si alloy composite material is cast in a vacuum consumable electrode shell solidification furnace with a vacuum degree of 0.1-1Pa, an arc voltage of 30-40V, and an arc current of 20000-50000A.

The chemical composition table (weight percent) of table 1 embodiment 1-9 alloy

The inventors conducted mechanical property experiments on the Ti alloys in Examples 1-9 at room temperature and at a service temperature of 500-600°C, and the experimental results are shown in Table 2:

Table 2 Tensile properties of Ti-Si alloy composites at room temperature, 500°C and 600°C

Claims (3)

1. a high alumina height silicon cast titanium alloy, it is characterized in that, described titanium alloy mass percent is: Al7.2-9.5%, Si0.8-1.8%, Zr0.5-3.5%, V0.5-3%, Mo0.1-4.5%, Nb0.1-4.5%, Ta0.1-3.5%, the rest is Ti and inevitable impurity, titanium alloy adds the subsidiary element boron (B) of crystal grain thinning, and the addition of B is: 0.01-0.25%.

2. according to a kind of high alumina height silicon cast titanium alloy of claim 1, it is characterized in that this alloying component contains: Al7.5-8.5%, Si1.05-1.6%, Zr1.0-2.5%, V0.5-2.5%, Mo0.1%-2.5%, Nb0.1%-3.5%, Ta0.1%-1.5%, the rest is Ti and inevitable impurity, titanium alloy adds the subsidiary element boron (B) of crystal grain thinning, and the addition of B is: 0.01-0.25%.

3. high alumina height silicon cast titanium alloy according to claim 1, it is characterised in that described titanium alloy is also added with purifying the subsidiary element of the yttrium of melts of titanium alloy, lanthanum, cerium, gadolinium and samarium terres rares, and the addition of subsidiary element is: 0.01-0.25%.