Ultrafine-grained titanium alloy material and in-situ synthesis method thereof

Abstract

The application discloses a kind of ultrafine-grained titanium alloy materials and in-situ synthesis method thereof, the method comprises: one, according to the component proportion of target product, element powder is mixed;Two, green body is pressed;Three, laser vacuum smelting is obtained metal precursor;Four, metal precursor is heated to melt by electrostatic suspension equipment and is obtained after heat preservation cooling ultrafine-grained titanium alloy material.The application is by using electrostatic suspension process without using mould, so that metal melt is uniformly nucleated in the process of cooling and solidification and the nucleation rate is significantly increased, form far less than the nanometer scale metal ultrafine equiaxed crystal organization of traditional smelting method, simultaneously, the application realizes the in-situ alloying of titanium alloy material, and the degree of freedom of component design is large, without multiple smelting, production cost is reduced;Ultrafine-grained titanium alloy material of the application has high specific strength, high specific modulus, excellent corrosion resistance, good strength plastic / tenacity matching, and is widely used in aerospace, ocean engineering, weapon equipment and other high-tech fields.

Description

Technical Field

[0001] This invention belongs to the field of metal material preparation technology, specifically relating to an ultrafine-grained titanium alloy material and its in-situ synthesis method. Background Technology

[0002] Titanium is hailed as the "third metal," "space metal," and "ocean metal." Titanium and its alloys are extremely important lightweight structural materials and among the highest strength metals, possessing excellent corrosion resistance, heat resistance, and non-magnetic properties. They have found wide applications in aviation, aerospace, shipbuilding, chemical, metallurgical, biomedical, and transportation industries. Since the 1950s, titanium and its alloys have undergone over 70 years of development, expanding from the initial TC4 alloy to hundreds of varieties. The Northwest Nonferrous Metals Research Institute has independently developed nearly 50 types of titanium alloys, forming a series including high-temperature, low-temperature, high-strength, high-toughness, damage-tolerant, corrosion-resistant, marine, flame-retardant, low-cost, and medical titanium alloys. They have developed titanium alloy products such as plates, foils, tubes, bars, wires, forgings, pressure vessels, shaped parts, and fasteners.

[0003] Currently, the mainstream preparation method for titanium alloys remains the melting method. Since titanium alloy melts always contain some impurities, the solidified pellets often nucleate on these solid impurity particles. Simultaneously, the direct contact between the titanium alloy melt and the mold wall also leads to direct nucleation on the mold wall. Therefore, the crystallization process of titanium alloys mainly proceeds via heterogeneous nucleation, exhibiting a dendritic growth pattern. Furthermore, compared to homogeneous nucleation, heterogeneous nucleation requires very little nucleation work; therefore, under relatively low supercooling conditions, heterogeneous nucleation begins significantly when homogeneous nucleation is still negligible. Studies have shown that when the supercooling is approximately 0.02T... m At this point, heterogeneous nucleation has the highest nucleation rate, which is only equivalent to the supercooling required for homogeneous nucleation to reach the maximum nucleation rate (0.2T). m The oxygen content is 1 / 10 of that of titanium alloys. To improve the properties of titanium alloys, it is often desirable to obtain fine equiaxed grains. Therefore, after smelting, titanium alloys still need to undergo forging or rolling, heat treatment and other processes, which leads to increased oxygen content, low material utilization, long production cycle and high preparation cost. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide an in-situ synthesis method for ultrafine-grained titanium alloy materials, addressing the shortcomings of the prior art. This method synthesizes ultrafine-grained titanium alloy materials in situ through powder mixing, pressing, vacuum melting, and electrostatic levitation heating, eliminating the need for molds. This allows for uniform nucleation of the molten metal during solidification, resulting in a very large supercooling that significantly increases the nucleation rate and leads to the formation of ultrafine equiaxed grains. This improves the properties of the titanium alloy and solves the problems of increased oxygen content, long preparation processes, and high costs associated with obtaining fine equiaxed grains through subsequent processing steps.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an in-situ synthesis method for ultrafine-grained titanium alloy materials, characterized in that the method includes the following steps:

[0006] Step 1: Weigh the corresponding elemental powders according to the composition ratio of the target product, ultrafine crystalline titanium alloy material, and then mix them to obtain mixed metal powder.

[0007] Step 2: Press the mixed metal powder obtained in Step 1 to obtain a green blank;

[0008] Step 3: Perform laser vacuum melting on the green blank obtained in Step 2 to obtain the metal precursor;

[0009] Step 4: The metal precursor obtained in Step 3 is heated by an electrostatic levitation device. After the metal precursor melts and is kept at a certain temperature, it is cooled to obtain an ultrafine-grained titanium alloy material.

[0010] The above-mentioned in-situ synthesis method for ultrafine-grained titanium alloy material is characterized in that the mixing in step one is performed using ball milling at a speed of 200 rpm to 350 rpm. By employing ball milling and controlling the milling speed, this invention achieves uniform mixing of the powders while refining the powder particles, and avoids excessively high speeds that could lead to oxidation and explosion of the titanium powder, thus ensuring the safety of the powder mixing process.

[0011] The above-mentioned in-situ synthesis method for ultrafine-grained titanium alloy material is characterized in that the green blank in step two is cylindrical or hemispherical. This invention, by limiting the green blank to cylindrical or hemispherical shape, ensures the formation of a spherical metal precursor during subsequent laser vacuum melting, facilitating the subsequent electrostatic levitation process while shortening melting time, saving energy, and reducing preparation costs.

[0012] The above-mentioned in-situ synthesis method for an ultrafine-grained titanium alloy material is characterized in that the holding time in step four is 2 min to 5 min. This invention ensures alloy homogenization by limiting the holding time after the metal precursor melts, while avoiding excessively long holding times that waste energy and increase synthesis costs.

[0013] The above-mentioned in-situ synthesis method for an ultrafine-grained titanium alloy material is characterized in that the heating method in step four is laser heating. Laser heating is fast, and the laser is easy to adjust and operate.

[0014] The above-mentioned in-situ synthesis method for an ultrafine-grained titanium alloy material is characterized in that the superheat of the metal precursor melting in step four is 100℃~200℃. This superheat ensures that the metal precursor is completely melted and alloyed, avoiding excessive superheat that would increase laser power and waste electrical energy, while also causing an increase in the volatilization rate of alloying elements and affecting the actual composition of the titanium alloy material, which deviates from the designed composition.

[0015] The above-mentioned in-situ synthesis method for an ultrafine-grained titanium alloy material is characterized in that the cooling method in step four is furnace cooling in a suspended state. By cooling in the furnace in a suspended state, the molten metal precursor is in a deeply supercooled state, which increases the nucleation rate of the ultrafine-grained titanium alloy material, refines the grains, and thus improves the strength and toughness of the ultrafine-grained titanium alloy material.

[0016] The above-mentioned in-situ synthesis method for an ultrafine-grained titanium alloy material is characterized in that the ultrafine-grained titanium alloy material in step four is made of Ti185 alloy, TiNi alloy, TiZr alloy, TiNbZr alloy, or TiNbVZr alloy. More preferably, it is Ti185 alloy, TiNbZr alloy, or TiNbVZr alloy. Ti185 alloy is a low-cost, high-strength titanium alloy that can be used to manufacture aerospace structural components and has broad application prospects. TiNbZr alloy and TiNbVZr alloy are high-entropy alloys with advantages such as high melting point, high strength, high plasticity, high fracture toughness at low temperatures, and high thermal stability, and can be widely used in aerospace, defense, and military industries. The synthesis method of this invention has a wide range of applications and high practical value.

[0017] In addition, the present invention also discloses an ultrafine-grained titanium alloy material prepared by the method described above.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. This invention selects elemental powders according to the composition ratio of the target product, and synthesizes ultrafine-grained titanium alloy materials in situ after pressing, vacuum melting, and electrostatic levitation heating. The electrostatic levitation process eliminates the need for molds, allowing the molten metal formed from the melting of the metal precursor to not contact the mold wall during cooling and solidification. Instead, nucleation occurs directly from the preform based on the energy changes of the molten metal, which is closer to a uniform nucleation method. Furthermore, because no mold is required, the molten metal forms a very large supercooling (approaching 0.2T) during cooling. mThe nucleation work of the crystal nuclei is significantly reduced, while the nucleation rate is significantly increased, thereby enabling the metal to form an ultrafine equiaxed crystal structure and obtain ultrafine-grained titanium alloy materials.

[0020] 2. This invention selects elemental powders for subsequent synthesis processes based on the composition ratio of the target product, which is beneficial for the free design and formulation of titanium alloy components. Combined with materials genome engineering, it can realize the rapid design and preparation of new titanium alloys and shorten the research and development cycle.

[0021] 3. This invention uses a combination of powder metallurgy and electrostatic suspension to prepare titanium alloy materials, which significantly reduces the segregation and impurity content of the titanium alloy material composition, making the titanium alloy material composition more uniform and the material performance closer to the theoretical value.

[0022] 4. The titanium alloy material prepared by this invention has a very small grain size, which is at the nanoscale and much smaller than the grain size of titanium alloy materials prepared by traditional smelting methods. This significantly improves the strength and hardness of the titanium alloy material, while greatly enhancing its plasticity and toughness. It also gives the titanium alloy material high specific strength, high specific modulus, excellent corrosion resistance, and good strength-plasticity / toughness matching. This solves the constraints of strength-plasticity and strength-toughness in titanium alloy materials and is conducive to expanding the application fields of titanium alloy materials.

[0023] 5. This invention prepares ultrafine-grained titanium alloy materials through a controlled synthesis method, eliminating the need for subsequent multiple melting, forging, and heat treatment processes for grain refinement. This significantly shortens the preparation process, reduces production costs, and can be applied to the preparation of other alloy materials.

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0025] Figure 1 This is a microstructure diagram of the ultrafine-grained Ti185 alloy material prepared in Example 1 of the present invention.

[0026] Figure 2 This is a microstructure diagram of the Ti185 alloy material prepared in Comparative Example 1 of this invention. Detailed Implementation

[0027] Example 1

[0028] This embodiment includes the following steps:

[0029] Step 1: According to the composition ratio of the target product, ultrafine-grained Ti185 (Ti-1Al-8V-5Fe) alloy material, weigh the corresponding mass of Ti powder, Al powder, FeV80 powder and Fe powder, and then use a planetary ball mill to mix them. The ball milling speed is 300 rpm and the ball milling time is 3 hours to obtain mixed metal powder.

[0030] Step 2: Press the mixed metal powder obtained in Step 1 to obtain a cylindrical green blank with an outer dimension (diameter × height) of φ3.0mm × 2mm;

[0031] Step 3: The cylindrical green blank obtained in Step 2 is subjected to laser vacuum melting to obtain a spherical metal precursor;

[0032] Step 4: The spherical metal precursor obtained in Step 3 is laser-heated using an electrostatic levitation device. After the metal precursor melts, it is heated to a superheat of 100°C and held for 3 minutes. The laser is then turned off, and the precursor is cooled in a levitation state with the furnace to obtain the ultrafine-grained Ti185 alloy material.

[0033] Figure 1 This is a microstructure diagram of the ultrafine-grained Ti185 alloy material prepared in this embodiment. Figure 1 It can be seen that the grain size in this ultrafine-grained Ti185 alloy material is very small, at the nanoscale.

[0034] In this embodiment, the shape of the green blank in step two can also be hemispherical; the target product ultrafine-grained Ti185 alloy material in steps one and four can also be replaced with ultrafine-grained TiNi alloy material or ultrafine-grained TiZr alloy material.

[0035] Comparative Example 1

[0036] This comparative example uses the traditional smelting method and includes the following steps:

[0037] Step 1: According to the composition ratio of the target product, ultrafine-grained Ti185 (Ti-1Al-8V-5Fe) alloy material, weigh the corresponding mass of sponge titanium, aluminum particles, TiFe32 particles, and FeV80 particles, and then press them into electrode blocks.

[0038] Step 2: Perform vacuum induction melting on the electrode block obtained in Step 1 to obtain an alloy block;

[0039] Step 3: Perform a second vacuum induction melting on the alloy block obtained in Step 2 to obtain Ti185 alloy material.

[0040] Titanium alloy materials are prepared by melting powder raw materials. Due to the large specific surface area of ​​powder, impurities are easily introduced due to oxidation. Therefore, the traditional melting method in this comparative example uses metal or intermediate alloy particles to reduce raw material costs, and multiple melting processes are used to ensure sufficient and uniform alloying.

[0041] Figure 2 This is a microstructure diagram of the Ti185 alloy material prepared in this comparative example. Figure 2It can be seen that the grain size of this Ti185 alloy material is very coarse, ranging from several hundred micrometers, which is much larger than the grain size of the ultrafine Ti185 alloy material prepared in Example 1.

[0042] Example 2

[0043] This embodiment includes the following steps:

[0044] Step 1: According to the composition ratio of the target product, ultrafine-grained Ti185 (Ti-1Al-8V-5Fe) titanium alloy material, weigh the corresponding mass of Ti powder, Al powder, FeV80 powder and Fe powder, and then use a planetary ball mill to mix them. The ball milling speed is 200 rpm and the ball milling time is 4 hours to obtain mixed metal powder.

[0045] Step 2: Press the mixed metal powder obtained in Step 1 to obtain a cylindrical green blank with an external dimension (diameter × height) of φ4.0mm × 1.1mm;

[0046] Step 3: The cylindrical green blank obtained in Step 2 is subjected to laser vacuum melting to obtain a spherical metal precursor;

[0047] Step 4: The spherical metal precursor obtained in Step 3 is laser-heated using an electrostatic levitation device. After the metal precursor melts, it is heated to a superheat of 130°C and held for 2 minutes. The laser is then turned off, and the precursor is cooled in a levitation state with the furnace to obtain ultrafine-grained Ti185 titanium alloy material.

[0048] Example 3

[0049] This embodiment includes the following steps:

[0050] Step 1: According to the composition ratio of the target product, ultrafine-grained TiNbVZr alloy material (atomic ratio of 1:1:1:1), weigh the corresponding mass of Ti powder, Nb powder, V powder and Zr powder, and then use a planetary ball mill to mix them. The ball milling speed is 350 rpm and the ball milling time is 2 hours to obtain mixed metal powder.

[0051] Step 2: Press the mixed metal powder obtained in Step 1 to obtain a cylindrical green blank with an outer dimension (diameter × height) of φ2.5mm × 2.9mm;

[0052] Step 3: The cylindrical green blank obtained in Step 2 is subjected to laser vacuum melting to obtain a spherical metal precursor;

[0053] Step 4: The spherical metal precursor obtained in Step 3 is laser-heated using an electrostatic levitation device. After the spherical metal precursor melts, it is heated to a superheat of 200°C and held for 3 minutes. The laser is then turned off, and the precursor is cooled in a levitation state with the furnace to obtain an ultrafine-grained TiNbVZr alloy material.

[0054] Example 4

[0055] This embodiment includes the following steps:

[0056] Step 1: According to the composition ratio of the target product, ultrafine-grained TiNbVZr alloy material (atomic ratio of 2:1:1:1), weigh the corresponding mass of Ti powder, Nb powder, V powder and Zr powder, and then use a planetary ball mill to mix them. The ball milling speed is 300 rpm and the ball milling time is 3 hours to obtain mixed metal powder.

[0057] Step 2: Press the mixed metal powder obtained in Step 1 to obtain a cylindrical green blank with an outer dimension (diameter × height) of φ3.0mm × 2mm;

[0058] Step 3: The cylindrical green blank obtained in Step 2 is subjected to laser vacuum melting to obtain a spherical metal precursor;

[0059] Step 4: The spherical metal precursor obtained in Step 3 is laser-heated using an electrostatic levitation device. After the spherical metal precursor melts, it is heated to a superheat of 150°C and held for 5 minutes. The laser is then turned off, and the precursor is cooled in a levitation state with the furnace to obtain an ultrafine-grained TiNbVZr alloy material.

[0060] Example 5

[0061] This embodiment includes the following steps:

[0062] Step 1: According to the composition ratio of the target product, ultrafine-grained TiNbZr alloy material (atomic ratio of 1:1:1), weigh the corresponding mass of Ti powder, Nb powder and Zr powder, and then use a planetary ball mill to mix them. The ball milling speed is 300 rpm and the ball milling time is 3 hours to obtain mixed metal powder.

[0063] Step 2: Press the mixed metal powder obtained in Step 1 to obtain a cylindrical green blank with an outer dimension (diameter × height) of φ2.5mm × 1.5mm;

[0064] Step 3: The cylindrical green blank obtained in Step 2 is subjected to laser vacuum melting to obtain a spherical metal precursor;

[0065] Step 4: The spherical metal precursor obtained in Step 3 is laser-heated using an electrostatic levitation device. After the metal precursor melts, it is heated to a superheat of 200°C and held for 4 minutes. The laser is then turned off, and the precursor is cooled in a levitation state with the furnace to obtain an ultrafine-grained TiNbZr alloy material.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for in-situ synthesis of ultrafine-grained titanium alloy materials, characterized in that, The method includes the following steps: Step 1: Weigh the corresponding elemental powders according to the composition ratio of the target product, ultrafine crystalline titanium alloy material, and then mix them to obtain mixed metal powder. Step 2: Press the mixed metal powder obtained in Step 1 to obtain a green blank; the green blank is cylindrical or hemispherical. Step 3: Perform laser vacuum melting on the green blank obtained in Step 2 to obtain the metal precursor; Step 4: The metal precursor obtained in Step 3 is heated by an electrostatic levitation device. After the metal precursor melts and is held at a certain temperature, it is cooled to obtain an ultrafine-grained titanium alloy material. The heating method is laser heating, the superheat of the metal precursor is 100℃~200℃, and the cooling method is furnace cooling in a levitation state. The mixing in step one is performed using ball milling, with a ball milling speed of 200 rpm to 350 rpm; The heat preservation time mentioned in step four is 2 to 5 minutes; The ultrafine-grained titanium alloy material mentioned in step four is made of Ti185 alloy, TiNi alloy, TiZr alloy, TiNbZr alloy, or TiNbVZr alloy.

2. An ultrafine-grained titanium alloy material prepared by the method as described in claim 1.

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