Preparation method of beta-spot-free Ti185 alloy with nano lamellar structure

Abstract

The invention discloses a preparation method of a beta-spot-free Ti185 alloy with a nano lamellar structure. The method comprises the following steps: 1, selecting Ti, Al, V and Fe metals, carrying out vacuum arc melting, and cutting to obtain a Ti185 block; 2, the Ti185 block is re-smelted to obtain a Ti185 sphere; and thirdly, the Ti185 balls are put into electrostatic suspension equipment to be subjected to hot melting, then the superheat degree is adjusted for deep supercooling solidification, and the Ti185 alloy free of beta spots and provided with the nanometer lamellar structure is obtained. According to the method, the container-free, microgravity and high-vacuum characteristics of electrostatic suspension equipment are utilized, heterogeneous nucleation of Ti185 melt is inhibited, the Ti185 melt is in a deep supercooled state in the solidification process, the solidification speed is high, the solid solubility of elements is effectively increased, element segregation of the Ti185 alloy is greatly reduced, beta spots are effectively eliminated, meanwhile, the Ti185 alloy with a nano lamellar structure is obtained, and the Ti185 alloy with the nano lamellar structure is obtained. And the obdurability of the Ti185 alloy is obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of high-strength titanium alloy preparation, and in particular relates to a method for preparing a Ti185 alloy without β spots and having a nano-layer lamellar structure. Background Art

[0002] Titanium alloys are used to improve energy efficiency due to their high strength-to-weight ratio, such as in automotive, aerospace, energy and chemical applications. Titanium alloys can reduce weight, improve fuel efficiency, minimize packaging constraints, greatly improve global fuel efficiency and reduce greenhouse gas emissions. Although titanium alloys have been applied to many fields, the high price of titanium limits its large-scale application in the industry, because the price of titanium is 5 times that of steel and 10 times that of aluminum, and the complex processing steps further increase the cost of titanium. To overcome this obstacle, the most direct way to reduce costs is to use low-priced elements, such as Fe. Ti-1Al-8V-5Fe (Ti185) is a metastable β titanium alloy developed in the early 1960s. Iron is added to Ti185 as a stabilizer, which can significantly reduce the cost of this alloy compared to expensive Ti alloy stabilizers such as Mo, Cr and V. Ti185 has high tensile strength and shear strength, making it an attractive engineering material in the aerospace industry. However, despite the many application advantages of Ti185, the addition of more than 2.5wt% of iron-titanium alloy in traditional casting production leads to iron segregation, which ultimately leads to an inhomogeneous structure and the generation of β spots. β spots have been shown to be an alloy that is detrimental to fracture toughness, ductility and fatigue properties.

[0003] Electrostatic levitation technology is a container-free processing technology that uses the Coulomb force on charged objects in an electrostatic field to balance gravity to achieve material suspension. Electrostatic levitation technology has the characteristics of high suspension stability, independent material without container, no external field disturbance, and no pollution in high vacuum environment. After more than 30 years of development, electrostatic levitation technology has gradually been applied to the research of thermophysical properties of materials, deep supercooling rapid solidification mechanism and liquid metal structure. Therefore, it is hoped that the β spots in Ti185 alloy can be eliminated through electrostatic levitation technology, and the intrinsic characteristics of Ti185 can be promoted, which will help expand the development of lightweight, high-strength and low-cost new titanium alloys. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure in view of the deficiencies of the above-mentioned prior art. The method utilizes the characteristics of the electrostatic levitation equipment without a container, microgravity, and high vacuum to suppress the heterogeneous nucleation of the Ti185 melt, so that it is in a deep supercooled state during the solidification process, and the solidification speed is fast, which effectively increases the element solubility, greatly reduces the element segregation of the Ti185 alloy, effectively eliminates the β spots, and solves the problem that the iron segregation in the Ti185 alloy leads to an uneven structure and the generation of β spots, thereby damaging the mechanical properties.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a Ti185 alloy without β spots and having a nano-layer lamellar structure, characterized in that the method comprises the following steps:

[0006] Step 1: Select Ti, Al, V, and Fe metals with a mass purity of 99.9%, use vacuum arc to melt to obtain a Ti185 ingot, and cut the Ti185 ingot into Ti185 blocks;

[0007] Step 2: Using a spherical copper crucible, the Ti185 block in step 1 is remelted by a laser heater to obtain a Ti185 sphere;

[0008] Step 3: Place the Ti185 sphere obtained in step 2 into an electrostatic suspension device, evacuate the device, heat and melt the Ti185 sphere using a CO2 laser, and then adjust the superheat according to the melting point of the Ti185 alloy to perform deep supercooling solidification to obtain a Ti185 alloy without β spots and with a nano-lamellar structure.

[0009] The present invention firstly remelts a Ti185 block to form a Ti185 sphere which is easy to suspend and has balanced force, so that the sphere is suitable for electrostatic suspension, and then puts the sphere into an electrostatic suspension device for heating and melting. Based on the characteristics of the electrostatic suspension device without container, microgravity and high vacuum, the contact or contamination of the melt by the crucible container wall is eliminated, heterogeneous nucleation is suppressed, and a Ti185 melt with deep supercooling is obtained; the Ti185 melt is in a deep supercooling state during the solidification process, which effectively increases the element solubility, is beneficial to reducing the diffusion segregation of the Fe element, and the Ti185 melt in the deep supercooling state solidifies quickly, further reducing the segregation of various elements of the Ti185 alloy, thereby eliminating β spots caused by the segregation of the Fe element, and forming a nano-layer lamellar structure, so as to obtain a high-quality, lightweight and high-strength Ti185 alloy.

[0010] The above-mentioned method for preparing a Ti185 alloy without β spots and having a nano-layered lamellar structure is characterized in that the cutting in step one is wire cutting, and the Ti185 block is coarsely ground with water sandpaper and cleaned with ethanol solution.

[0011] The above-mentioned method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure is characterized in that the length, width and height of the Ti185 block in step one are all 2.40 mm ± 0.18 mm, and the diameter of the Ti185 sphere in step two is 2.7 mm ± 0.2 mm.

[0012] The above-mentioned method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure is characterized in that in step three, the superheat is adjusted to 100K~300K according to the melting point of the Ti185 alloy 1923K, and deep supercooling solidification is carried out at a supercooling degree of 146K~250K.

[0013] The above-mentioned method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure is characterized in that in step 3, the cyclic melting and deep supercooling solidification are performed 5 to 7 times to obtain a large supercooling degree of more than 250 K. The present invention adjusts the number of cyclic melting and deep supercooling solidification to obtain a higher supercooling degree, thereby ensuring that a Ti185 alloy without β spots and having a nano-lamellar structure is obtained, thereby achieving a strengthening and toughening effect on the Ti185 alloy.

[0014] The above-mentioned method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure is characterized in that the maximum supercooling degree obtained after cyclic melting and deep supercooling solidification in step 3 is 385K, which is about 0.20T m , T m is the melting point of Ti185 alloy.

[0015] The above-mentioned method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure is characterized in that in step three, within the supercooling range of 146K to 385K, the obtained Ti185 alloy has no β spots and has a nano-lamellar structure.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The present invention utilizes the characteristics of containerless, microgravity, and high vacuum of the electrostatic levitation equipment to suppress the heterogeneous nucleation of the Ti185 melt, so that it is in a deep supercooled state during the solidification process, and the solidification speed is fast, which effectively increases the solid solubility of the elements, is beneficial to reduce the diffusion segregation of the Fe element, thereby eliminating the β spots caused by the segregation of the Fe element, and obtaining high-quality, lightweight, and high-strength Ti185 alloy.

[0018] 2. The present invention places the Ti185 sphere in an electrostatic suspension device for heating and melting and deep supercooling solidification, and uses the surface tension of the molten metal in the suspended state to automatically shrink into a sphere with high dimensional accuracy, smooth surface and no solidification defects; at the same time, the vacuum degree of the electrostatic suspension device is as high as 10 -3 Pa, effectively solved the oxidation problem of Ti185 alloy.

[0019] 3. The present invention adopts an electrostatic suspension method to heat and melt the Ti185 sphere and perform deep supercooling solidification to obtain a Ti185 alloy with a nano-layered lamellar structure, which significantly improves the strength and toughness of the Ti185 alloy.

[0020] 4. In the process of preparing Ti185 alloy by the electrostatic suspension method, the present invention can eliminate β spots, avoid subsequent complex heat treatment processes, effectively simplify the process, and improve the preparation efficiency.

[0021] 5. The preparation process of the present invention is pollution-free and loss-free, thus realizing green production, and has high preparation efficiency, no material loss in the preparation process, low preparation cost, and is easy for engineering application.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a low-magnification SEM image of the Ti185 alloy prepared in Example 1 of the present invention.

[0024] Figure 2 This is a high magnification SEM image of the Ti185 alloy prepared in Example 1 of the present invention.

[0025] Figure 3 This is a low-magnification SEM image of the Ti185 alloy prepared in Example 2 of the present invention.

[0026] Figure 4 This is a low-magnification SEM image of the Ti185 alloy prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0027] Example 1

[0028] This embodiment includes the following steps:

[0029] Step 1: Select Ti, Al, V, and Fe metals with a mass purity of 99.9%, and use vacuum arc to melt to obtain a Ti185 ingot. Use wire cutting to cut a Ti185 block with a length, width, and height of 2.39 mm from the Ti185 ingot, and perform rough grinding with water sandpaper and cleaning with ethanol solution on the Ti185 block.

[0030] Step 2: Using a spherical copper crucible, the Ti185 block cleaned in step 1 is remelted by a laser heater to obtain a Ti185 sphere with a diameter of 2.65 mm;

[0031] Step 3: Place the Ti185 sphere obtained in step 2 into the electrostatic suspension device and evacuate to 10 -3Pa, high voltage is applied, and the Ti185 sphere is suspended under the Coulomb force by high voltage discharge. Then the Ti185 sphere is heated and melted by CO2 laser, and the melting and solidification curve is observed, so that the Ti185 sphere is melted at 1923K, and the laser is kept on and continued to be heated to 2030K, that is, the superheat is 107K. After the laser is turned off, it is naturally cooled and deeply supercooled and solidified to obtain a supercooling degree of 146K, and the Ti185 alloy deeply supercooled and solidified at a supercooling degree of 146K is obtained.

[0032] Figure 1 This is a low-power SEM image of the Ti185 alloy prepared in this embodiment. Figure 1 It can be seen that there is no β spot in the Ti185 alloy.

[0033] Figure 2 This is a high-magnification SEM image of the Ti185 alloy prepared in this embodiment. Figure 2 It can be seen that the Ti185 alloy contains nano-sheet structures at the grain boundaries and inside the grains.

[0034] Example 2

[0035] This embodiment includes the following steps:

[0036] Step 1: Select Ti, Al, V, and Fe metals with a mass purity of 99.9%, and use vacuum arc to melt to obtain a Ti185 ingot. Use wire cutting to cut a Ti185 block with a length, width, and height of 2.44 mm from the Ti185 ingot, and perform rough grinding with water sandpaper and cleaning with ethanol solution on the Ti185 block.

[0037] Step 2: Using a spherical copper crucible, the Ti185 block cleaned in step 1 is remelted by a laser heater to obtain a Ti185 sphere with a diameter of 2.67 mm;

[0038] Step 3: Place the Ti185 sphere obtained in step 2 into the electrostatic suspension device and evacuate to 10 -3 Pa, high voltage is applied, and the Ti185 sphere is suspended under the Coulomb force by high voltage discharge. Then the Ti185 sphere is heated and melted by CO2 laser, and the melting and solidification curve is observed, so that the Ti185 sphere is melted at 1923K, and the laser is kept on and continued to be heated to 2050K, that is, the superheat is 127K. After the laser is turned off, it is naturally cooled and deeply supercooled and solidified to obtain a supercooling of 245K, and a Ti185 alloy deeply supercooled and solidified at a supercooling of 245K is obtained.

[0039] Figure 3 This is a low-power SEM image of the Ti185 alloy prepared in this embodiment. Figure 3 It can be seen that there is no β spot in the Ti185 alloy, and there are nano-platelet structures at the grain boundaries and inside the grains.

[0040] Example 3

[0041] This embodiment includes the following steps:

[0042] Step 1: Select Ti, Al, V, and Fe metals with a mass purity of 99.9%, and use vacuum arc to melt to obtain a Ti185 ingot. Use wire cutting to cut a Ti185 block with a length, width, and height of 2.32 mm from the Ti185 ingot, and perform rough grinding with water sandpaper and cleaning with ethanol solution on the Ti185 block.

[0043] Step 2: Using a spherical copper crucible, the Ti185 block cleaned in step 1 is remelted by a laser heater to obtain a Ti185 sphere with a diameter of 2.62 mm;

[0044] Step 3: Place the Ti185 sphere obtained in step 2 into the electrostatic suspension device and evacuate to 10 -3 Pa, high voltage is applied, and high voltage discharge is used to make the Ti185 sphere suspended under the action of Coulomb force. Then a CO2 laser is used to heat and melt the Ti185 sphere, and the melting and solidification curve is observed, so that the Ti185 sphere is melted at 1923K, and the laser is kept on and continued to be heated to 2150K, that is, the superheat is 227K. After the laser is turned off, it is naturally cooled, and the supercooling of the sample after solidification is read. If the supercooling is small, that is, lower than 250K, the laser is turned on again, and the melting and solidification are cyclically repeated for 7 times to obtain a large supercooling of 385K, and a Ti185 alloy that is deeply supercooled and solidified at a supercooling of 385K is obtained.

[0045] Figure 4 This is a low-power SEM image of the Ti185 alloy prepared in this embodiment. Figure 4 It can be seen that there is no β spot in the Ti185 alloy, and there are nano-platelet structures at the grain boundaries and inside the grains.

[0046] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure, characterized in that: The method comprises the following steps: Step 1: Select Ti, Al, V, and Fe metals with a mass purity of 99.9%, use vacuum arc to melt to obtain a Ti185 ingot, and cut the Ti185 ingot into Ti185 blocks; Step 2: Using a spherical copper crucible, the Ti185 block in step 1 is remelted by a laser heater to obtain a Ti185 sphere; Step 3: Place the Ti185 sphere obtained in step 2 into an electrostatic suspension device, evacuate the device, heat and melt the Ti185 sphere using a CO2 laser, and then adjust the superheat according to the melting point of the Ti185 alloy to perform deep supercooling solidification to obtain a Ti185 alloy without β spots and with a nano-lamellar structure.

2. The method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure according to claim 1, characterized in that: The cutting described in step 1 is wire cutting, and the Ti185 block is coarsely ground with water sandpaper and cleaned with ethanol solution.

3. The method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure according to claim 1, characterized in that: The length, width and height of the Ti185 block in step 1 are all 2.40 mm ± 0.18 mm, and the diameter of the Ti185 sphere in step 2 is 2.7 mm ± 0.2 mm.

4. The method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure according to claim 1, characterized in that: In step 3, the superheat is adjusted to 100K-300K according to the melting point of Ti185 alloy 1923K, and deep supercooling solidification is carried out at a supercooling degree of 146K-250K.

5. The method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure according to claim 1, characterized in that: In step 3, melting and deep supercooling solidification are cyclically performed 5 to 7 times to obtain a large supercooling degree of more than 250K.

6. The method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure according to claim 5, characterized in that: The maximum supercooling degree obtained after cyclic melting and deep supercooling solidification in step 3 is 385K, which is about 0.20T. m , T m is the melting point of Ti185 alloy.

7. The method for preparing a Ti185 alloy without β spots and having a nano-lamellar structure according to claim 1, characterized in that: In step 3, within the supercooling range of 146K to 385K, the obtained Ti185 alloy has no β spots and has a nano-lamellar structure.

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