CN108893631B - High-strength titanium alloy and preparation method thereof - Google Patents
High-strength titanium alloy and preparation method thereof Download PDFInfo
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Abstract
The invention provides a high-strength titanium alloy and a preparation method thereof, and the high-strength titanium alloy comprises, by mass, 2.2-3.8% of Al, 4.5-5.5% of Mo, 4.0-5.0% of V, less than or equal to 0.15% of Si, and 0, 50% of Zr]And the balance Ti. The content of each element is strictly controlled, the mechanical property of the titanium alloy is improved, wherein due to the fact that the addition of Zr causes lattice distortion, the defects can cause that nucleation points are increased and the nucleation density is increased in the nucleation process, so that the effect of grain refinement is achieved, and fine grain strengthening is achieved; v enhances the ability of the alloy to form the beta phase; v is a slight decrease in the alpha + beta transition temperature, has very low solubility in alpha-Zr and alpha-Ti, and is TiV in the mesophase with Ti and Zr respectively2And ZrV2The dispersion of the two phases in the matrix can improve the strength; and the addition of V can refine grains and improve strength.
Description
Technical Field
The invention relates to the technical field of titanium alloy, in particular to a high-strength titanium alloy and a preparation method thereof.
Background
The titanium alloy has a series of advantages of high specific strength, high specific modulus, corrosion resistance and the like, has wide application advantages, and is emphasized in various fields of ocean engineering, aerospace, biomedicine, metallurgy, chemical industry, light industry and the like.
The structural titanium alloy has excellent machinability and mechanical properties, and is used for manufacturing parts with high strength and complex shapes in the aerospace industry, such as wing joint structural members of aviation airplanes, connecting frames of airframes and undercarriages, joints of suspended engines and the like, and manufacturing important or key bearing parts with high requirements on strength and durability. However, the strength level of the conventional titanium alloy used as an aviation structure still cannot meet the increasingly strict industrial service standard.
Disclosure of Invention
In view of the above, the present invention aims to provide a high-strength titanium alloy and a preparation method thereof. The titanium alloy provided by the invention has excellent comprehensive mechanical properties of strength and toughness, and meets the requirements of titanium alloys for aviation structures.
The invention provides a high-strength titanium alloy which comprises, by mass, 2.2-3.8% of Al, 4.5-5.5% of Mo, 4.0-5.0% of V, less than or equal to 0.15% of Si, 0, 50% of Zr and the balance of Ti.
Preferably, the high-strength titanium alloy comprises 2.2-3.8% of Al, 4.5-5.5% of Mo, 4.0-5.0% of V, less than or equal to 0.15% of Si, 0, 50% of Zr and the balance of Ti.
Preferably, the structure of the high-strength titanium alloy comprises a beta phase matrix and an alpha' martensite phase; the grain size of the high-strength titanium alloy structure is 51.4-120.5 mu m.
The invention also provides a preparation method of the high-strength titanium alloy, which comprises the following steps:
(1) smelting alloy raw materials to obtain an as-cast alloy blank;
(2) carrying out heat preservation treatment on the as-cast alloy blank obtained in the step (1) and then deforming to obtain a densified alloy blank;
(3) and (3) carrying out solution treatment on the compact alloy blank obtained in the step (2) to obtain the high-strength titanium alloy.
Preferably, the smelting in the step (1) is vacuum arc smelting, and the temperature of the vacuum arc smelting is 2000-2900 ℃.
Preferably, the smelting times in the step (1) are more than 5 times, and each smelting time is more than 1 min.
Preferably, the temperature of the heat preservation treatment in the step (2) is 880-950 ℃, and the time of the heat preservation treatment is 0.5-1.0 h.
Preferably, the deformation in the step (2) is rolling deformation; the total deformation amount of the rolling deformation is 60-70%, and the temperature of the rolling deformation is 895-935 ℃.
Preferably, the rolling deformation is multi-pass rolling, and the deformation of each pass is 10-15%;
when multi-pass rolling is adopted, after each pass of rolling, the rolled alloy billet is kept at the rolling deformation temperature for 5-7 min.
Preferably, the heat preservation temperature of the solution treatment in the step (3) is 895-935 ℃, the heat preservation time of the solution treatment is 3-7 min, and the cooling mode of the solution treatment is water quenching.
The invention provides a high-strength titanium alloy which comprises, by mass, 2.2-3.8% of Al, 4.5-5.5% of Mo4.0-5.0% of V, less than or equal to 0.15% of Si, and 0.50% of Zr]And the balance Ti. The content of each element is strictly controlled, the mechanical property of the titanium alloy is improved, wherein due to the fact that the addition of Zr causes lattice distortion, the defects can cause that nucleation points are increased and the nucleation density is increased in the nucleation process, so that the effect of grain refinement is achieved, and fine grain strengthening is achieved; mo can strengthen beta phase in a solid solution manner, reduce phase transformation point and enhance hardenability, thereby enhancing heat treatment strengthening effect; the V belongs to a beta stable element with the same crystal form, so that the capacity of forming a beta phase of the alloy is enhanced; v slightly lowers the alpha → beta phase transition temperature, has very low solubility in alpha-Zr and alpha-Ti, and is TiV with the intermediate phase of Ti and Zr2And ZrV2The dispersion of the two phases in the matrix can improve the strength; and the addition of V can refine grains and improve strength. According to the invention, the solid solution strengthening effect of the Al element is obvious, the phase composition of the alloy is adjusted together with the Mo and V elements, the phase structure of the alloy is optimized, meanwhile, the addition of a large amount of Zr element not only plays a role of solid solution strengthening, but also properly reduces the alpha → beta phase transition temperature of the alloy, so that the alloy retains more beta phases, the beta phases are in a body-centered cubic structure, have more sliding systems relative to the alpha phases in a close-packed hexagonal structure, are better in plasticity and are original in the alloyThe initial beta crystal grains are refined, the density of the initial beta crystal grain boundary is increased, so that the dislocation movement is hindered, and the strength is further improved. Experimental results show that the tensile strength of the titanium alloy obtained by the invention is improved by 41.3%.
Drawings
FIG. 1 is a metallographic optical micrograph of a titanium alloy obtained in example 1;
FIG. 2 is a metallographic optical micrograph of a titanium alloy obtained in example 2;
FIG. 3 is a metallographic optical micrograph of a titanium alloy obtained in example 3;
FIG. 4 is a metallographic optical micrograph of a titanium alloy obtained in example 4;
FIG. 5 is a metallographic optical micrograph of a titanium alloy obtained according to example 5;
FIG. 6 is a graph showing the dimensions of tensile specimens used in the tensile testing of the present invention.
Detailed Description
The invention provides a high-strength titanium alloy which comprises, by mass, 2.2-3.8% of Al, 4.5-5.5% of Mo, 4.0-5.0% of V, less than or equal to 0.15% of Si, 0.50% of Zr and the balance of Ti.
The high-strength titanium alloy provided by the invention comprises 2.2-3.8% of Al, preferably 2.4-2.8% or 3.5-3.8%, and more preferably 2.5% by mass. In the present invention, the Al is used to form a phase structure of a titanium-aluminum alloy; the element Al greatly improves the stability of alpha phase and the beta-alpha transition temperature, so that the alpha phase which is obtained after quenching in the process of solution treatment is small, the specific strength of the titanium alloy can be greatly improved, and the light weight of the alloy can be realized to a certain extent; and the corrosion resistance of the zirconium can be greatly improved by adding the aluminum.
The high-strength titanium alloy provided by the invention comprises 4.5-5.5% of Mo, preferably 5.0-5.5%, and more preferably 5.2-5.4% by mass. In the invention, Mo strengthens beta phase in a solid solution manner, lowers the phase transformation point, enhances the hardenability and further enhances the heat treatment strengthening effect; the addition of Mo also improves the corrosion resistance of the alloy. And because of the low diffusivity of Mo, the temperature sensitivity of the alloy in the two-phase region rolling process can be reduced, and the alloy processing window is enlarged; the low Mo equivalent improves the nucleation driving force of the alpha phase, changes the aging kinetics of the alloy, and enables the alpha phase to be more uniformly distributed, thereby obtaining excellent mechanical properties.
The high-strength titanium alloy provided by the invention comprises, by mass, 4.0-5.0% of V, preferably 4.5-4.8%, and more preferably 4.6-4.9%. In the invention, the V belongs to a beta stable element with the same crystal form, so that the capacity of forming a beta phase of the alloy is enhanced; v slightly lowers the alpha → beta transition temperature, has little solubility in alpha-Zr and alpha-Ti, and has a TiV as the intermediate phase with Ti and Zr2And ZrV2The dispersion of the two phases in the matrix can improve the strength and reduce the corrosion resistance of the alloy; and the addition of V can refine grains and improve strength and plasticity.
The high-strength titanium alloy provided by the invention comprises, by mass, Zr (0, 50%), preferably 2.5-50%, further preferably 2.5-30%, more preferably 5-28%, and further preferably 8-15%, in the invention, due to lattice distortion caused by the addition of Zr element, the defects can cause that in the nucleation process, nucleation points are increased, the density of nucleation is increased, the effect of grain refinement is achieved, and fine grain strengthening is achieved, the element Zr is added into matrix titanium, and neutral element Zr which has little influence on phase transition temperature and Ti form an infinite solid solution, so that solid solution strengthening is achieved, the passivation potential of Zr is more negative than that of Ti, passivation can still occur even in a weak oxidation condition environment, the capability of forming a dense oxide film on the surface is improved, and the corrosion resistance of the high-strength titanium alloy is improved.
The high-strength titanium alloy provided by the invention comprises, by mass, not more than 0.15% of Si, preferably 0.001-0.1%, and more preferably 0.01-0.8%. In the present invention, the addition of a small amount of Si can improve the high-temperature strength and creep property of the titanium alloy.
The high-strength titanium alloy provided by the invention comprises the following elements in addition to the above elements in mass, and the balance of Ti.
In the present invention, the structure of the high-strength titanium alloy preferably includes a β -phase matrix and α 'martensite, and more preferably includes a β -phase matrix and a fine acicular martensite phase and a lamellar α' martensite phase. In the high-strength titanium alloy structure of the present invention, the grain size of the crystal grain is preferably 51.4 to 120.5 μm, and more preferably 60 to 90 μm.
The invention also provides a preparation method of the high-strength titanium alloy, which comprises the following steps:
(1) smelting alloy raw materials to obtain an as-cast alloy blank;
(2) carrying out heat preservation treatment on the as-cast alloy blank obtained in the step (1) and then deforming to obtain a densified alloy blank;
(3) and (3) carrying out solution treatment on the compact alloy blank obtained in the step (2) to obtain the high-strength titanium alloy.
The invention obtains as-cast alloy blank after smelting alloy raw materials. The present invention is not particularly limited in the kind of the alloy raw material, and the alloy raw material well known to those skilled in the art is used to obtain a titanium alloy having a target composition. In the present invention, the alloy raw material preferably includes titanium sponge, zirconium sponge, pure aluminum, pure chromium, high purity vanadium, and high purity tin. The invention has no special limit on the proportion of various alloy raw materials, and the final alloy components can meet the requirements.
In the invention, the smelting is preferably vacuum arc smelting, and the temperature of the vacuum arc smelting is preferably 2000-2900 ℃, more preferably 2200-2400 ℃, and most preferably 2250-2300 ℃; the smelting time is preferably 3-5 min, and more preferably 4 min. In the invention, the vacuum degree of the vacuum arc melting is preferably 0.04-0.05 MPa, and the vacuum arc melting is carried out under the condition of argon. When vacuum arc melting is adopted, the invention preferably firstly pumps the vacuum degree in the furnace chamber to 9 x 10-3Introducing argon gas below Pa; the introduction amount of the argon is enough to satisfy the amount of the ionized gas for arc melting. In the invention, the current of the vacuum arc melting is preferably 400-450A, and more preferably 420-435A. The present invention does not require special embodiments of the vacuum arc melting process, as will be appreciated by those skilled in the art. The invention adopts the mode of firstly vacuumizing and then introducing argon to firstly avoid Ti and Zr at high temperatureUnder the condition, a large amount of hydrogen is absorbed, oxygen is absorbed, nitrogen is absorbed, oxidation is carried out, and ionized gas can be provided for electric arc melting. In the invention, the number of times of smelting is preferably 5 or more, and more preferably 6 to 10 times, and an as-cast alloy billet is obtained after smelting. In the present invention, when the melting is repeatedly performed, the melting is preferably performed in a vacuum arc melting furnace; specifically, the method comprises the following steps: smelting a metal raw material in an electric arc smelting furnace to obtain a smelting liquid; and then cooling to obtain a casting blank, turning over the casting blank, smelting, obtaining a smelting solution again, cooling the smelting solution again to obtain the casting blank, repeating the process for more than 5 times to ensure that the obtained as-cast blank has uniform components.
During smelting, beta phase preferentially nucleates and grows in the process of converting a smelting liquid into a solid state to obtain a beta phase blank, and a foundation is provided for subsequent solid solution treatment to obtain an alpha' martensite phase. And the smelting process can make the components of the as-cast blank uniform, and effectively eliminate air holes and defects.
Before smelting, the alloy raw materials are preferably subjected to ultrasonic cleaning; the present invention does not require special embodiments of the ultrasonic cleaning, and may be practiced as is known to those skilled in the art.
After the as-cast alloy blank is obtained, the as-cast alloy blank is deformed after heat preservation treatment to obtain a densified alloy blank. According to the invention, the thermal insulation treatment is carried out on the as-cast alloy blank firstly, and then the deformation treatment is carried out, so that the titanium alloy ingot can keep a higher temperature in the deformation process, and the thermal deformation is realized. The invention adopts thermal deformation to preferably eliminate casting defects, compact the structure, refine grains, improve the tensile strength and plasticity, generate a large amount of dislocation and improve the mechanical property of the alloy in the rolling direction.
In the invention, the temperature of the heat preservation treatment is preferably 895-935 ℃, more preferably 900-920 ℃, and even more preferably 910-915 ℃. In the present invention, the heat-preserving time of the heat-preserving treatment is preferably 0.5 to 1.0 hour, and more preferably 0.6 to 0.9 hour.
After the heat preservation treatment, the titanium alloy ingot after heat preservation is deformed to obtain a compact alloy blank. In the invention, the deformation is preferably rolling deformation, and the total deformation amount of the rolling deformation is preferably 60-70%, and more preferably 67-68%; the rolling deformation temperature is preferably 895-935 ℃, more preferably 900-920 ℃, and more preferably 910-915 ℃, and is consistent with the temperature in the heat preservation treatment process. In the invention, the deformation treatment refines metastable beta-phase grains and generates a large amount of dislocation, which is beneficial to improving the yield and tensile strength of the alloy.
In the invention, the rolling deformation is further preferably multi-pass rolling, and the deformation amount of each pass is preferably 10-15%, and is further preferably 12-14%; the invention has no special requirement on the rolling times of the multi-pass rolling so as to finish the target deformation. When the alloy billet is rolled for multiple times, after each rolling, the rolled alloy billet is preferably kept at the rolling deformation temperature for 5-10 min, and more preferably for 6-7 min. The present invention does not require special embodiments of the rolling deformation, and can be implemented as is well known to those skilled in the art.
After the densified alloy billet is obtained, the invention carries out solid solution treatment on the densified alloy billet to obtain the high-strength titanium alloy. In the invention, the heat preservation temperature of the solution treatment is preferably 895-935 ℃, more preferably 900-920 ℃, and more preferably 910-915 ℃; the heat preservation time of the solution treatment is preferably 3-7 min, and more preferably 4-5 min. In the present invention, the cooling method of the solution treatment is preferably water quenching, and more preferably water quenching in water at room temperature. The present invention does not require any particular embodiment of the solution treatment, and embodiments known to those skilled in the art may be used. In the present invention, the heat preservation process of the solution treatment is preferably performed under a protective atmosphere, specifically, an argon protective atmosphere. In the invention, the solid solution treatment can eliminate residual stress caused by thermal deformation as much as possible, improve plasticity, effectively control the form, size, proportion and phase interface of alpha phase and beta phase in the alloy, change the distribution of micro-area components and better regulate and control the performance of the alloy.
In the present invention, the cooling method of the solution treatment is preferably water quenching. The present invention does not require any particular embodiment of the solution treatment, and embodiments known to those skilled in the art may be used. In the present invention, the heat preservation process of the solution treatment is preferably performed under a protective atmosphere, specifically, an argon protective atmosphere. The solid solution treatment is adopted, the solid solution temperature is low, the solid solution time is long, Zr can be made to be in solid solution in the alloy matrix through the solid solution treatment, and the metastable beta phase with a cubic structure can be intercepted, so that the mechanical property of the alloy is improved, and the tensile strength of the titanium alloy is improved.
After the solution treatment, the surface oxide skin of the solid solution alloy is preferably removed, so that the high-strength corrosion-resistant titanium alloy is obtained. The invention preferably adopts a grinding mode to remove the surface scale.
In order to further illustrate the present invention, the following examples are provided to describe the high strength titanium alloy and the method for preparing the same in detail, but they should not be construed as limiting the scope of the present invention.
Example 1
According to alloy components: ti, balance Zr: 10%, Al: 2.2%, Mo: 4.5%, V: 4.0%, Si: 0.001% (mass percent) of burdening, weighing (the total mass of the raw materials is 100g) 10g of industrial grade sponge zirconium, 2.2g of high-purity aluminum, 4.5g of high-purity molybdenum, 4.0g of high-purity vanadium and 0.001g of silicon, soaking in absolute ethyl alcohol for ultrasonic cleaning, air-drying after ultrasonic cleaning, placing in a water-cooled copper crucible of a non-consumable vacuum arc melting furnace, and pumping the vacuum degree in a furnace cavity to 8 multiplied by 10-3And (2) below Pa, introducing high-purity argon as a protective gas (the vacuum degree is 0.04-0.05 MPa) before arc melting, then performing arc temperature of about 2500 ℃ during each melting, performing melting time of about 3 minutes after each melting, cooling to obtain an ingot after each melting, performing turnover treatment on the ingot to perform melting, and repeatedly melting the cast ingot and turning the ingot 8 times to ensure that the finally obtained ingot is uniform in component.
And then heating the taken alloy ingot to a rolling temperature and preserving heat for 30 minutes, wherein the rolling temperature is 935 ℃, the rolling is multi-pass rolling deformation, the reduction of each pass is about 2mm, after each pass of rolling, putting the alloy ingot into a muffle furnace to be reheated to 935 ℃ and preserving heat for 5 minutes, and the alloy ingot is made into an alloy plate with the final deformation of 66%. After the final pass rolling, carrying out solution treatment: and re-heating to 935 ℃, preserving the temperature for 3 minutes, then rapidly quenching in room-temperature water, taking out the alloy plate after the alloy plate is completely cooled, finely polishing off an oxide layer on the surface of the alloy ingot, cleaning and air-drying the alloy ingot to obtain the high-strength titanium alloy.
Example 2
According to alloy components: balance of Ti, Zr: 20%, Al: 2.5%, Mo: 4.7%, V: 4.2%, Si: 0.01 percent (mass percentage) of material preparation, 20g of industrial grade sponge zirconium, 2.5g of high-purity aluminum, 4.7g of high-purity molybdenum, 4.2g of high-purity vanadium and 0.01g of silicon (the total mass of the raw materials is 100g) are weighed and soaked in absolute ethyl alcohol, the mixture is dried after being cleaned by ultrasonic waves and is placed into a water-cooled copper crucible of a non-consumable vacuum arc melting furnace, the vacuum degree in a furnace cavity needs to be pumped to 8 multiplied by 10-3And (2) below Pa, introducing high-purity argon as a protective gas (the vacuum degree is 0.04-0.05 MPa) before arc melting, then performing arc melting at the temperature of about 2900 ℃ for each time, performing melting for about 3 minutes, cooling to obtain an ingot after each melting, performing turnover treatment on the ingot to perform melting, and repeatedly melting the cast ingot and turning the ingot for 7 times to ensure that the finally obtained ingot is uniform in component.
And then heating the taken alloy ingot to a rolling temperature and preserving heat for 0.6h, wherein the rolling temperature is 920 ℃, the rolling is multi-pass rolling deformation, the thickness of the finally obtained plate is 5mm, the reduction of each pass is about 2mm, after each pass of rolling, the finally obtained plate is placed into a muffle furnace to be heated to 920 ℃ again and preserved heat for 6 minutes, and the alloy ingot is made into an alloy plate with the final deformation of 65 percent. After the final pass rolling, carrying out solution treatment: and re-heating to 920 ℃, preserving heat for 5 minutes, then rapidly quenching in room-temperature water, taking out the alloy plate after the alloy plate is completely cooled, finely polishing off an oxide layer on the surface of the alloy ingot, cleaning and air-drying the alloy ingot to obtain the high-strength titanium alloy.
Example 3
According to alloy components: zr: 30% of Al: 2.9%, Mo: 5.1%, V: 4.5%, Si: 0.06 percent (mass percentage) of material preparation, 30g of industrial grade sponge zirconium, 2.9g of high-purity aluminum, 5.1g of high-purity molybdenum, 4.5g of high-purity vanadium and 0.06g of silicon (the total mass of the raw materials is 100g) are weighed and soaked in absolute ethyl alcohol, the mixture is dried after being cleaned by ultrasonic waves and is placed into a water-cooled copper crucible of a non-consumable vacuum arc melting furnace, the vacuum degree in a furnace cavity needs to be pumped to 8 multiplied by 10-3And (2) below Pa, introducing high-purity argon as a protective gas (the vacuum degree is 0.04-0.05 MPa) before arc melting, then performing arc temperature of about 2500 ℃ during each melting, performing melting time of about 3 minutes after each melting, cooling to obtain an ingot after each melting, performing turnover treatment on the ingot to perform melting, and repeatedly melting the cast ingot and turning the ingot for 9 times to ensure that the finally obtained ingot is uniform in component.
And then heating the taken alloy ingot to a rolling temperature and preserving heat for 0.7h, wherein the rolling temperature is 910 ℃, the rolling is multi-pass rolling deformation, the reduction of each pass is about 2mm, after each pass of rolling, the alloy ingot is placed into a muffle furnace to be reheated to 910 ℃ and preserved heat for 7 minutes, and the alloy ingot is made into an alloy plate with the final deformation of 67 percent, so that a plate with the thickness of 5mm is obtained. After the final pass rolling, carrying out solution treatment: and reheating to 910 ℃, preserving heat for 5 minutes, then rapidly quenching in room-temperature water, taking out after the alloy plate is completely cooled, finely polishing off an oxide layer on the surface of the alloy ingot, cleaning and air-drying to obtain the high-strength titanium alloy.
Example 4
According to alloy components: ti, balance Zr: 40%, Al: 3.5%, Mo: 5.3%, V: 4.8%, Si: 0.1 percent (mass percentage) of material preparation, 40g of industrial grade sponge zirconium, 3.5g of high-purity aluminum, 5.3g of high-purity molybdenum, 4.8g of high-purity vanadium and 0.1g of silicon (the total mass of the raw materials is 100g) are weighed and soaked in absolute ethyl alcohol, the mixture is dried after being cleaned by ultrasonic waves and is placed into a water-cooled copper crucible of a non-consumable vacuum arc melting furnace, the vacuum degree in a furnace cavity needs to be pumped to 8 multiplied by 10-3Below Pa, introducing high-purity argon as a protective gas (the vacuum pressure reaches 0.04-0.05 MPa) before arc melting, then performing arc melting at the temperature of about 2500 ℃ for each time for about 3 minutes, and cooling after each time of melting to obtain an ingotAnd then turning the ingot casting for smelting, and repeatedly smelting the cast ingot by smelting-casting and turning the cast ingot for 5 times so as to ensure that the finally obtained cast ingot has uniform components.
And then heating the taken alloy ingot to a rolling temperature, keeping the temperature for 0.9h, wherein the rolling temperature is 900 ℃, the rolling is multi-pass rolling deformation, the reduction of each pass is about 2mm, after each pass of rolling, putting the alloy ingot into a muffle furnace, reheating to 900 ℃, keeping the temperature for 9 minutes, and preparing the alloy ingot into an alloy plate with the final deformation of 69%, wherein the thickness of the plate is 5 mm. After the final pass rolling, carrying out solution treatment: and re-heating to 900 ℃, preserving heat for 6 minutes, then rapidly quenching in room-temperature water, taking out the alloy plate after the alloy plate is completely cooled, finely polishing off an oxide layer on the surface of the alloy ingot, cleaning and air-drying the alloy ingot to obtain the high-strength titanium alloy.
Example 5
According to alloy components: ti, balance Zr: 50%, Al: 3.8%, Mo: 5.5%, V: 5.0%, Si: 0.15 percent (mass percentage) of material preparation, 50g of industrial grade sponge zirconium, 3.8g of high-purity aluminum, 5.5g of high-purity molybdenum, 5.0g of high-purity vanadium and 0.15g of silicon (the total mass of the raw materials is 100g) are weighed and soaked in absolute ethyl alcohol, the mixture is dried after being cleaned by ultrasonic waves and is placed into a water-cooled copper crucible of a non-consumable vacuum arc melting furnace, the vacuum degree in a furnace cavity needs to be pumped to 8 multiplied by 10-3And (2) below Pa, after introducing high-purity argon as a protective gas before arc melting, wherein the arc temperature is about 2900 ℃ during each melting, the melting time is about 3 minutes, cooling to obtain an ingot after each melting, turning over the ingot to melt, and repeatedly melting the cast ingot by the melting-casting and turning over the ingot for 7 times to ensure that the finally obtained ingot is uniform in components.
And then heating the taken alloy ingot to a rolling temperature and preserving heat for 1h, wherein the rolling temperature is 895 ℃, the rolling is multi-pass rolling deformation, the reduction of each pass is about 2mm, after each pass of rolling, the alloy ingot is placed into a muffle furnace to be reheated to 895 ℃ and preserved heat for 10 minutes, the alloy ingot is made into an alloy plate with the final deformation of 70%, and the plate thickness is 5 mm. After the final pass rolling, carrying out solution treatment: and (3) reheating to 895 ℃, keeping the temperature for 7 minutes, then rapidly quenching in room-temperature water, taking out the alloy plate after the alloy plate is completely cooled, finely polishing off an oxide layer on the surface of the alloy ingot, cleaning and air-drying the alloy ingot to obtain the high-strength titanium alloy.
Comparative example 1
An alloy composition of Ti-3Al-5Mo-4.5V titanium alloy was prepared in the manner of example 1.
Tensile specimens (national standard: GBT228-2002) were cut out of the titanium alloy of examples 1 to 5 and comparative example 1 by wire cutting, as shown in FIG. 6. At least 5 tensile specimens were cut out of each sample to ensure reproducibility of the data, and the measurement was carried out using a room temperature uniaxial tensile test with an Instron5982 universal material tester (manufacturer: Instron, usa) whose tensile displacement was monitored all the way with a extensometer, the tensile rate being set at 5 × 10-3s-1And performing a tensile test to obtain data related to the mechanical properties, wherein the test results are shown in table 1.
TABLE 1 mechanical Properties test of titanium alloys obtained in examples 1 to 5 and comparative example 1
As is apparent from Table 1, the titanium alloys obtained in examples 1 to 5 have yield strengths as compared with the actually measured Ti-3Al-5Mo-4.5V titanium alloy in the titanium alloy obtained in the present invention: 713.5-872.9 MPa, tensile strength: 784.8-1021.6 MPa; the strength of the alloy is obviously improved, and the plasticity is only slightly reduced, so that the toughness can be improved.
The results of metallographic structure observation of the titanium alloys obtained in examples 1 to 5 are shown in fig. 1 to 5, respectively.
As can be seen from FIG. 1, the Ti-based alloy prepared in this example is composed of a beta phase as a matrix and a fine and staggered acicular alpha' phase, and the acicular alpha phase is much smaller and the grain is finer than that of the Ti-3Al-5Mo-4.5V alloy prepared by the same treatment process. In combination with the mechanical property test results in table 1, the fine needle-like alpha phase and the refined crystal grains greatly improve the strength of the alloy, and compared with the comparative alloy Ti-3Al-5Mo-4.5V titanium alloy, the tensile strength is improved by 8.5 percent.
As can be seen from FIG. 2, the titanium-based alloy obtained in this example is composed of a beta phase as a matrix and a fine acicular alpha phase, and the acicular alpha phase is much smaller than the metallographic structure of the titanium alloy of comparative example 1, and part of the acicular alpha phase is transformed into lamellar alpha' martensite and the crystal grains are refined. Combining the mechanical property test results in table 1, it can be seen that the strength of the alloy is greatly improved due to the fine acicular alpha phase, lamellar alpha' martensite and fine crystal grains, and the tensile strength is improved by 16.4% compared with that of the Ti-3Al-5Mo-4.5V titanium alloy.
As can be seen from FIG. 3, the Ti-based alloy obtained in this example was composed of a beta phase as a matrix and a fine acicular alpha phase, and the acicular alpha phase was much reduced as compared with the comparative titanium alloy Ti-3Al-5Mo-4.5V, a part of the acicular alpha phase was transformed into lamellar alpha 'martensite and the lamellar alpha' martensite was reduced in thickness with increasing Zr content, and the crystal grains were gradually reduced with increasing Zr content. The results of mechanical property tests in Table 1 show that the strength of the alloy is greatly improved due to the fine acicular alpha phase, lamellar alpha' martensite and fine crystal grains, and the tensile strength is improved by 24.2% compared with that of Ti-3Al-5Mo-4.5V titanium alloy.
As shown in FIG. 4, the titanium-based alloy obtained in this example consisted of a beta phase as a matrix and a fine acicular alpha phase, and the acicular alpha phase was much smaller than that of the titanium alloy Ti-3Al-5Mo-4.5V of comparative example 1, and a part of the acicular alpha phase was transformed into lamellar alpha 'martensite, and the lamellar alpha' martensite was reduced in thickness and gradually reduced in crystal grains as the Zr content was increased. The results of mechanical property tests in Table 1 show that the strength of the alloy is greatly improved due to the fine acicular alpha phase, lamellar alpha' martensite and fine crystal grains, and the tensile strength is improved by 33.0 percent compared with that of Ti-3Al-5Mo-4.5V titanium alloy.
As shown in FIG. 5, the Ti-based alloy obtained in this example was composed of a beta phase as a matrix and a fine acicular alpha phase, and the acicular alpha phase was much reduced as compared with the Ti-3Al-5Mo-4.5V alloy obtained in comparative example 1, and a part of the acicular alpha phase was transformed into lamellar alpha 'martensite and the lamellar alpha' martensite was reduced in thickness and gradually reduced in crystal grains as the Zr content was increased. The results of mechanical property tests in Table 1 show that the strength of the alloy is greatly improved by fine acicular alpha phase, lamellar alpha' martensite and fine crystal grains, and the tensile strength is improved by 41.3% compared with that of the comparative example Ti-3Al-5Mo-4.5V titanium alloy.
As can be seen from FIGS. 1 to 6, the structure of the titanium alloy prepared in the different embodiments of the present invention is changed, and a significant beta grain boundary appears and a large number of acicular alpha 'and alpha' martensite phases are present in the beta grain; the main composition phases of the alloy are an alpha 'martensite phase and an alpha' martensite phase, and the two martensite phases are elongated needle-shaped structures in structural morphology, so that the existence of a large number of needle-shaped structures can be seen in the metallographic phase. While the acicular α phase is gradually replaced by the lamellar α 'martensite phase as the Zr content increases, and the thickness of such lamellar α' martensite phase is gradually decreased. And the grain size thereof gradually decreases as the Zr content increases.
The embodiment can show that the mechanical property of the titanium alloy is improved by controlling the content of each element, the strength of the titanium alloy is obviously improved, and the titanium alloy meets the requirements of aviation components.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be construed as the protection scope of the present invention.
Claims (8)
1. A high-strength titanium alloy comprises, by mass, 2.2-3.8% of Al, 4.5-5.5% of Mo, 4.0-5.0% of V, less than or equal to 0.15% of Si, 0, 50% of Zr and the balance of Ti;
the structure of the high-strength titanium alloy comprises a beta-phase matrix and an alpha' martensite phase; the grain size of the crystal grains in the high-strength titanium alloy structure is 51.4-120.5 mu m;
the preparation method of the high-strength titanium alloy comprises the following steps:
(1) smelting alloy raw materials to obtain an as-cast alloy blank;
(2) carrying out heat preservation treatment on the as-cast alloy blank obtained in the step (1) and then deforming to obtain a densified alloy blank;
(3) and (3) carrying out solution treatment on the compact alloy blank obtained in the step (2) to obtain the high-strength titanium alloy.
2. The method for preparing the high-strength titanium alloy according to claim 1, comprising the steps of:
(1) smelting alloy raw materials to obtain an as-cast alloy blank;
(2) carrying out heat preservation treatment on the as-cast alloy blank obtained in the step (1) and then deforming to obtain a densified alloy blank;
(3) and (3) carrying out solution treatment on the compact alloy blank obtained in the step (2) to obtain the high-strength titanium alloy.
3. The production method according to claim 2, wherein the melting in the step (1) is vacuum arc melting, and the temperature of the vacuum arc melting is 2000-2900 ℃.
4. The production method according to claim 2 or 3, wherein the number of times of melting in the step (1) is 5 or more, and each melting time is 1min or more.
5. The preparation method according to claim 2, wherein the temperature of the heat-preserving treatment in the step (2) is 880-950 ℃, and the time of the heat-preserving treatment is 0.5-1.0 h.
6. The production method according to claim 2, wherein the deformation in the step (2) is a rolling deformation; the total deformation amount of the rolling deformation is 60-70%, and the temperature of the rolling deformation is 895-935 ℃.
7. The preparation method of claim 6, wherein the rolling deformation is multi-pass rolling, and the deformation amount of each pass is 10-15%;
when multi-pass rolling is adopted, after each pass of rolling, the rolled alloy billet is kept at the rolling deformation temperature for 5-10 min.
8. The preparation method according to claim 2, wherein the heat preservation temperature of the solution treatment in the step (3) is 895-935 ℃, the heat preservation time of the solution treatment is 3-7 min, and the cooling mode of the solution treatment is water quenching.
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