A device and method for chip-making, sintering and pressing of a heterogeneous titanium alloy in one step

Abstract

The application discloses a device and a method for integrated chip-making, sintering and pressing of heterogeneous titanium alloy. The device comprises a chip-making mechanism at the upper part and a sintering and pressing mechanism at the lower part. The chip-making mechanism comprises a columnar shell, a conical hopper arranged below the columnar shell, and a rotary milling cutter arranged in the columnar shell. The rotary milling cutter is provided with titanium alloy with at least two different phase structures on the outer periphery. The sintering and pressing mechanism comprises a pressing head, a liftable isolation plate, a stirring mechanism and a pressing cavity with a heating mechanism. The lower part of the conical hopper extends into the isolation plate, so that the chips prepared by the rotary milling cutter are transported to the stirring mechanism in the sintering and pressing mechanism. The stirring mechanism transports the chips to the pressing cavity. The pressing head presses, and the heating mechanism is started to perform sintering and pressing. The application can prepare a high-strength and high-toughness heterogeneous titanium alloy by mixing the alpha-phase Ti-Al alloy and the beta-phase Ti-V alloy, and then combining hot rolling and annealing treatment after sintering and pressing.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of material preparation, and particularly relates to a chip preparation, sintering and pressing integrated device and method for isomerous titanium alloy. BACKGROUND

[0002] Metallic titanium is abundant in the earth's crust, second only to aluminum, iron and magnesium. Titanium is an allotropes metal, which will undergo allotropes transformation at a temperature of (882±2) DEG C. At room temperature, it is a close-packed hexagonal crystal structure (hcp), which is called alpha-Ti; when the temperature exceeds 882 DEG C, it is a body-centered cubic crystal structure (bcc), which is called beta-Ti. Alpha-Ti-Al intermetallic compounds are widely used in the field of aerospace due to their light weight, high temperature strength, good creep resistance and strong oxidation resistance; but the plasticity of such intermetallic compounds is extremely poor, even after alloying and complex thermal mechanical processing (plasticizing) treatment, the elongation is also low, and it is difficult to process and shape due to its brittleness. The beta-Ti-V binary alloy has good processing and shaping ability, but its yield strength is low, which makes it difficult to be used in industry.

[0003] It is found through retrieval that L. Lilensten et al. published a paper entitled "From single phase to dual-phase TRIP-TWIP titanium alloys: Design approach and properties" in Materialia, 2020, 12, 100700, which proposed a strengthening method for dual-phase TRIP (transformation induced plasticity) / TWIP (twinning induced plasticity) titanium alloy based on Calphad thermodynamic calculation and Bo-Md alloy design tool. By introducing alpha phase into single-phase metastable beta titanium alloy, a dual-phase titanium alloy is obtained, and the TRIP and TWIP effects generated thereby improve the ductility and work hardening rate of the material. In addition, the introduced alpha phase provides additional yield strength and significant plasticity for the material, so that the titanium alloy has high strength and high toughness. The advantages of this method are: the mechanical properties of high strength and high toughness of the material can be obtained by introducing a dual-phase structure; but the disadvantages of this method are: a large amount of alloying elements need to be added, the production cost is high, and it is not conducive to industrial production.

[0004] Further search found that Karri et al. published a paper entitled "Demonstrating a duplex TRIP / TWIP titanium alloy via the introduction of metastable retained β-phase" in Materials Research Letters, 2022, 10:754-761. By heat treatment, metastable residual β phase can be obtained in duplex Ti-6Al-4V alloy. The TRIP and TWIP effects of metastable residual β phase make the duplex structure have higher work hardening rate and uniform elongation. At the same time, the solid solution strengthening caused by the enrichment of V element in metastable residual β phase also improves the yield strength of the material. The advantages of this technology are: (1) high strength and toughness of the material can be obtained by heat treatment, the process is simple and easy to operate; (2) the required alloying elements are less, and the cost is low. But also has the following shortcomings: (1) the prepared material component is simple, the microstructure regulation ability is limited, so that the mechanical property regulation is limited (2) the process operation is complex, the material is easy to oxidize and deform. SUMMARY

[0005] The purpose of the present application is to provide a heterogeneous titanium alloy chip sintering and pressing integrated device and method. The device and method are mainly through the mixing of heterogeneous titanium alloy chips, combined with specific heat treatment and plastic deformation, to obtain heterogeneous titanium alloy with different phase structures. Specifically, α-type titanium alloy and β-type titanium alloy are mixed to prepare chips, then pressed and sintered, and finally plastic deformed and heat treated to obtain high-strength and high-toughness duplex heterogeneous titanium alloy. During the deformation process, the α-phase and β-phase structures deform coordinately, resulting in heterogeneous induced hardening and additional work hardening, so that the duplex heterogeneous titanium alloy has excellent mechanical properties of high strength and high toughness.

[0006] The technical solution for achieving the purpose of the present application is a heterogeneous titanium alloy chip sintering and pressing integrated device, which comprises an upper chip milling mechanism and a lower pressing and sintering mechanism.

[0007] The chip milling mechanism comprises a cylindrical shell, a conical hopper arranged below the chip milling cylindrical shell, and a rotary milling cutter arranged in the chip milling cylindrical shell. The rotary milling cutter is provided with at least two titanium alloys with different phase structures on the outer periphery.

[0008] The pressing and sintering mechanism comprises a pressing head, a liftable isolation plate, a stirring mechanism and a pressing cavity with a heating mechanism.

[0009] The lower part of the conical hopper extends into the insulation plate, so as to transport the chips prepared by the rotary milling cutter to the stirring mechanism in the pressing and sintering mechanism, the stirring mechanism transports the chips to the pressing cavity, the pressing head presses, and the heating mechanism is started to press and sinter.

[0010] Further, the rotary milling cutter is provided with a milling cutter driving device.

[0011] Further, a disc is further included, the disc is driven to rotate by the power mechanism, the stirring mechanism is in the shape of a circular truncated cone, and a plurality of regularly arranged rib plates are arranged on the outer side surface of the stirring mechanism.

[0012] Through the rotation of the stirring mechanism with the rib plates, the chips enter the pressing cavity.

[0013] Further, the heating mechanism arranged on the pressing cavity is an embedded heating resistor arranged on the wall of the pressing cavity, and the embedded heating resistor is connected with a thermocouple and a power supply.

[0014] Further, an air outlet and an air inlet are arranged on the wall of the pressing cavity.

[0015] A method for preparing a heterogeneous titanium alloy by using the above device, comprising the following steps:

[0016] Step (1): The insulation plate is lifted, the cavity of the pressing and sintering mechanism is completely exposed, the milling cutter driving device and the stirring mechanism are started, the rotary milling cutter is started, and two or more titanium alloy blocks are arranged and stacked on both sides of the rotary milling cutter, and then pushed forward, the titanium alloy blocks are close to the rotary milling cutter to start the chip preparation, the chips pass through the conical hopper and enter the pressing and sintering mechanism.

[0017] Step (2): After the chips are fully mixed in the stirring mechanism, the chips enter the peripheral pressing cavity, after the pressing cavity is filled, the insulation plate is lowered, vacuum is drawn through the air outlet, and then the vacuum degree is 1-10 Pa, and then inert gas is injected into the pressing cavity through the air inlet, and the pressure in the pressing cavity is 0.9-1 MPa.

[0018] Step (3): The pressing head is lowered to preliminarily press the material, the required pressure is maintained on the pressing head, the heating resistor is started to press and sinter the preliminarily pressed material, and a titanium alloy preform is obtained.

[0019] Step (4): After the titanium alloy preform is cut into blocks, hot rolling is performed, and then the titanium alloy preform is placed in a vacuum furnace for annealing treatment, and a heterogeneous titanium alloy is obtained.

[0020] Further, the surface of the titanium alloy block in step (1) is polished before the chip preparation, and the oil stains and oxides on the surface are removed.

[0021] The two titanium alloy blocks are respectively an α-type titanium alloy and a β-type titanium alloy.

[0022] Further, the pressing head pressure in step (3) is 43-46 MPa, and the temperature for pressing and sintering is 1027-1400 DEG C for 30 minutes, and then air cooling to obtain the titanium alloy preform.

[0023] Further, the hot rolling in step (4) is carried out at 1027-1400 DEG C for 2-10 minutes before rolling, and the deformation is 50%-85%; and the annealing in step (4) is carried out at 500-800 DEG C for 2-5 hours.

[0024] A heterogeneous titanium alloy is prepared by the above method, and the heterogeneous titanium alloy comprises α phase Ti-Al, β phase Ti-V and α+β dual phase Ti-Al-V.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] (1) The alloy type can be selected according to the requirement, the proportion of mixed chips can be controlled, and the microstructure and mechanical properties of the prepared material have directionality and flexibility;

[0027] (2) The process flow is simple, the material is integrated into a shape by chip pressing and sintering, the interface has good combination, and there is no oxidation inclusion;

[0028] (3) The industrial chips can be selected for pressing and sintering to save resources and cost.

[0029] (4) The heterogeneous structure is wide, not only the soft α and hard β phases form a heterogeneous structure, but also Ti-6Al-4V (α+β dual phase structure) appears on the interface of the α and β phases due to the diffusion, and a multi-section heterogeneous structure is formed. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a chip preparation schematic diagram of the chip preparation, sintering and pressing integrated device of the present application.

[0031] Figure 2 It is a sintering and pressing schematic diagram of the chip preparation, sintering and pressing integrated device of the present application.

[0032] Figure 3 It is a top view of the stirring mechanism of the chip preparation, sintering and pressing integrated device of the present application.

[0033] Figure 4 It is a sintering and pressing process schematic diagram of the present application.

[0034] Figure 5 It is a hot rolling schematic diagram of the present application.

[0035] Figure 6 It is an annealing schematic diagram of the present application.

[0036] Figure 7 A metallographic diagram of the isomeric titanium alloy prepared by the present application.

[0037] BRIEF DESCRIPTION OF DRAWINGS

[0038] 1-cylindrical shell, 2-cone hopper, 3-rotary milling cutter, 4-embedded heating resistor, 5-press head, 6-insulation plate, 7-exhaust port, 8-air inlet, 9-milling cutter driving device, 10-insulation plate lifting driving device, 11-stirring mechanism, 12-pressing cavity, 13-disc, 22-table bottom, 14-roller, 15-vacuum furnace. DETAILED DESCRIPTION

[0039] The application will be further described in detail below with reference to the accompanying drawings.

[0040] As shown in the drawings, the chip-making and pressing sintering integrated device used in the present application comprises a turning and milling chip-making mechanism and a pressing sintering mechanism. Figures 1-7 The turning and milling chip-making mechanism comprises a chip-making cylindrical shell 1, a cone hopper 2, a rotary milling cutter 3 and a milling cutter driving device 9; the chip-making cylindrical shell 1 is located below the milling cutter driving device 9 and is connected with the rotary milling cutter 3 through a rotating shaft; the cone hopper 2 is in an integral structure with the chip-making cylindrical shell 1 and is located below the rotary milling cutter 3.

[0041] The pressing sintering device comprises a chip stirring mechanism 11 and a pressing sintering device; the chip stirring mechanism 11 is in a circular table shape and is externally provided with an annular press head 5; the press head 5 and the stirring mechanism 5 are provided with a liftable insulation plate 6; an insulation plate lifting driving device 10 for controlling the lifting of the insulation plate is arranged above the insulation plate; an embedded heating resistor 4 is arranged outside the pressing part; a thermocouple and a power supply are connected; an exhaust port 7 and an air inlet 8 are arranged.

[0042] The pressing sintering mechanism is located below the turning and milling chip-making mechanism and is connected with the cone hopper 2; the insulation plate 6 and the insulation plate lifting driving device 10 are arranged outside the cone hopper 2.

[0043] The chip-making and pressing sintering integrated forming method for preparing an isomeric titanium alloy mainly comprises the following steps:

[0044] Step one: start the hydraulic rod driving device to lift the insulation plate 6, completely expose the cavity of the chip stirring mechanism 11, start the milling cutter driving device 9 and the chip stirring mechanism 11; start the rotary milling cutter 3, arrange two or more titanium alloy blocks with different phase structures on both sides of the rotary milling cutter 3, then slowly push forward, the feeding amount is 0.01-0.5 mm / r; the titanium alloy blocks close to the rotary milling cutter 3 start to make chips; the chips pass through the cone hopper 2 and enter the pressing sintering device;

[0045] Step two: after the chips are mixed sufficiently in the stirring mechanism 11, they enter the pressing part. After the chips fill the pressing cavity 12 below the pressing head, the insulation plate lifting drive 10 lowers the insulation plate 6. Vacuum is drawn through the air outlet 7 to a vacuum degree of 1-10 Pa, and then inert gas is injected through the gas inlet to a pressure of 0.9-1 MPa inside the shell. The pressing head 5 is lowered to press the material preliminarily, with a pressing pressure of 43-46 MPa. The pressing head is kept at a certain pressure, and the heating resistor 4 is started to press and sinter the preliminarily pressed material, to obtain a titanium alloy preform. The titanium alloy preform is homogenized at 1027-1400 °C (β phase interval) for 30 minutes, and then air-cooled

[0046] Step three: the sintered and pressed ring-shaped titanium alloy preform is cut into blocks, and then hot-rolled by the roller 14. The titanium alloy preform is homogenized at 1027-1400 °C (β phase interval) for 2-10 minutes, with a rolling deformation of 50%-85%, and then air-cooled. The titanium alloy preform is then placed in a vacuum furnace (15) for annealing at a temperature of 500-800 °C, to obtain a heterostructure titanium alloy material.

[0047] Example 1

[0048] Industrial pure titanium and Ti40 are selected as experimental materials

[0049] Step one: the experimental materials are cut into a certain size by electric spark cutting, with a width and thickness of 10 mm and a length of 50 mm. The surface is then pretreated by removing oil, pickling, and other methods to clean the surface impurities and oxides, and the surface is ground by a grinding wheel. Then the integrated device is started, the insulation plate 6 is lifted by the hydraulic rod drive device, the cavity of the chip stirring mechanism 11 is completely exposed, and the milling cutter drive device 9 and the chip stirring mechanism 11 are turned on. The rotating milling cutter 3 is started, and the industrial pure titanium and Ti40 are arranged and stacked on both sides of the rotating milling cutter 3, and then slowly pushed forward at a feed rate of 0.3 mm / r. The titanium alloy block starts to chip when it approaches the rotating milling cutter 3. The chips enter the pressing and sintering device through the conical hopper 2.

[0050] Step two: after the chips are mixed sufficiently in the stirring mechanism 11, they enter the pressing part. After the chips fill the pressing cavity 12 below the pressing head, the insulation plate lifting drive 10 lowers the insulation plate 6. Vacuum is drawn through the air outlet 7 to a vacuum degree of 10 Pa, and then inert gas is injected through the gas inlet to a pressure of 1 MPa inside the shell. The pressing head 5 is lowered to press the material preliminarily, with a pressing pressure of 40 MPa. The pressing head is kept at a certain pressure, and the heating resistor 4 is started to press and sinter the preliminarily pressed material, to obtain a titanium alloy preform. The titanium alloy preform is homogenized at 1027-1400 °C (β phase interval) for 30 minutes, and then air-cooled

[0051] Step three: cut the pressed sintered circular titanium alloy preform into blocks, then hot-rolled by roller 14, keep at 1400℃ (β phase interval) for 5 min, rolling deformation is 80%, then air cooling, then put into vacuum furnace 15 for annealing treatment, annealing temperature is 500℃, to obtain heterogeneous titanium alloy preform. The obtained different phase structure reinforced titanium alloy, the microstructure diagram is similar to Figure 7 As shown in the figure, due to the influence of element diffusion, not only the soft α and hard β phases form a heterogeneous structure, but also Ti-6Al-4V (α+β phase dual-phase structure) appears on the interface between α and β phases, forming a multi-section heterogeneous structure.

[0052] Example 2

[0053] Selecting industrial pure titanium and Ti40 as experimental materials

[0054] Step one: cut the experimental materials into a certain size with a width and thickness of 10mm and a length of 50mm by using electric spark cutting, then perform surface pretreatment, clean surface impurities and oxides by oil removal, pickling and other methods, and polish the surface with a grinding wheel. Then start the integrated device, start the hydraulic rod driving device to lift the isolation plate 6, fully expose the cavity of the debris stirring mechanism 11, start the milling cutter driving device 9 and the debris stirring mechanism 11; start the rotating milling cutter 3, and then slowly push forward, the feed rate is 0.1mm / r; the titanium alloy block close to the rotating milling cutter 3 starts to cut; the debris passes through the conical hopper 2 and enters the pressing and sintering device;

[0055] Step two: after the debris is fully mixed in the stirring mechanism 11, it enters the pressing part, after the debris fills the pressing cavity 12 below the pressing head, start the isolation plate lifting driving device 10 to lower the isolation plate 6; vacuumize through the air outlet 7, vacuumize to 10Pa, then fill inert gas into the shell through the gas inlet to 1MPa, lower the pressing head 5 to preliminarily press the material, the pressing pressure is 40MPa; continue to maintain a certain pressure on the pressing head, start the heating resistance 4 to press and sinter the preliminarily pressed material, the temperature is 1400℃, obtain the titanium alloy preform, then homogenize the titanium alloy preform at 1400℃ (β phase interval) for 30 minutes, then air cool

[0056] Step three: cut the pressed sintered circular titanium alloy preform into blocks, then hot-rolled by roller 14, keep at 1400℃ (beta phase interval) for 5 minutes, rolling deformation is 80%, then air cooling, then put into vacuum furnace 15 for annealing treatment, annealing temperature is 600℃, to obtain heterogeneous titanium alloy preform. Due to the influence of element diffusion, not only the soft alpha and hard beta phase form heterogeneous structure, but also Ti-6Al-4V (alpha + beta phase dual phase structure) appears on the interface between alpha and beta phase, forming the characteristics of multi-section heterogeneous.

[0057] Example 3

[0058] TA5 (Ti-4Al-0.005B) and fire-resistant titanium alloy Alloy C (Ti-35V-15Cr) are selected as experimental materials

[0059] Step one: cut the experimental materials into a certain size with a width and thickness of 10mm and a length of 50mm by electric spark cutting, then perform surface pretreatment, clean surface impurities and oxides by oil removal, pickling and other methods, and polish the surface with a grinding wheel. Then start the integrated device, start the hydraulic rod driving device to lift the isolation plate 6, fully expose the cavity of the debris stirring mechanism 11, start the milling cutter driving device 9 and the debris stirring mechanism 11; start the rotating milling cutter 3, and then slowly push forward, the feed rate is 0.1mm / r; the titanium alloy block close to the rotating milling cutter 3 starts to cut; the debris passes through the conical hopper 2 and enters the pressing and sintering device;

[0060] Step two: after the debris is fully mixed in the stirring mechanism 11, it enters the pressing part, after the debris fills the pressing cavity 12 below the pressing head, start the isolation plate lifting driving device 10 to lower the isolation plate 6; vacuumize through the air outlet 7, vacuumize to 10Pa, then fill inert gas into the shell through the gas inlet to 1MPa, lower the pressing head 5 to preliminarily press the material, the pressing pressure is 40MPa; continue to keep a certain pressure on the pressing head, start the heating resistance 4 to press and sinter the preliminarily pressed material, the temperature is 1400℃, obtain the titanium alloy preform, the titanium alloy preform is homogenized at 1400℃ (beta phase interval) for 30 minutes, then air cooled

[0061] Step three: cut the sintered round ring titanium alloy preform into blocks, then hot rolling by roller 14, holding at 1400℃ (β phase interval) for 5 min, rolling deformation of 80%, then air cooling, and then put into vacuum furnace 15 for annealing treatment, annealing temperature is 550℃, to obtain heterogeneous titanium alloy preform. TA5 (Ti-4Al-0.005B) and fire-retardant titanium alloy Alloy C (Ti-35V-15Cr) due to the influence of element diffusion, not only the soft α and hard β phase form heterogeneous structure, but also Ti-6Al-4V (α+β phase dual-phase structure) appears on the interface of α and β phase, forming the characteristics of multi-section heterogeneous.

Claims

1. A chip-making, sintering, and pressing integrated device of a heterogeneous titanium alloy, characterized by, The application relates to a titanium alloy preparation device, which comprises a milling mechanism and a pressing sintering mechanism. The milling mechanism comprises a columnar shell (1), a conical hopper (2) arranged below the columnar shell (1), and a rotary milling cutter (3) arranged in the columnar shell (1), wherein the rotary milling cutter (3) is provided with titanium alloys with at least two different phase structures on the outer periphery. The pressing sintering mechanism comprises a pressing head (5), a liftable isolation plate (6), a stirring mechanism (11) and a pressing cavity (12) provided with a heating mechanism. The lower part of the conical hopper (2) extends into the isolation plate (6), so that the milling cutter (3) can deliver the milling cutter (3) to the stirring mechanism (11) in the pressing sintering mechanism, the stirring mechanism (11) can deliver the milling cutter (3) to the pressing cavity (12), the pressing head (5) can press and start the heating mechanism to perform pressing sintering. The heating mechanism arranged in the pressing cavity (12) is an embedded heating resistor (4) arranged on the wall of the pressing cavity (12), and the embedded heating resistor (4) is connected with a thermocouple and a power supply. The isolation plate (6) is lifted to expose the cavity of the pressing sintering mechanism, and the isolation plate (6) is lowered after the pressing cavity (12) is filled with the milling cutter (3).

2. The apparatus of claim 1, wherein, The rotary milling cutter (3) is provided with a milling cutter driving device (9).

3. The apparatus of claim 2, wherein, The device further comprises a disc (13) which is driven to rotate by a power mechanism, the stirring mechanism (11) is in the shape of a circular truncated cone, and a plurality of regularly arranged rib plates are arranged on the outer side of the stirring mechanism (11). The milling cutter (3) is delivered to the pressing cavity (12) through the rotation of the stirring mechanism (11) provided with the rib plates.

4. The apparatus of claim 3, wherein, An air outlet (7) and an air inlet (8) are arranged on the wall of the pressing cavity (12).

5. A method of producing an isomeric titanium alloy using the apparatus of claim 4, wherein, The device comprises the following steps: Step (1): the isolation plate (6) is lifted to expose the cavity of the pressing sintering mechanism, the milling cutter driving device (9) and the stirring mechanism (11) are started, the rotary milling cutter (3) is started, two or more titanium alloy blocks are arranged and stacked on the two sides of the rotary milling cutter (3), and then the titanium alloy blocks are pushed to be close to the rotary milling cutter (3) to start milling, the milling cutter (3) passes through the conical hopper (2) and enters the pressing sintering mechanism; Step (2): the milling cutter (3) is fully mixed in the stirring mechanism (11) and then enters the peripheral pressing cavity (12), the isolation plate (6) is lowered after the pressing cavity (12) is filled with the milling cutter (3), the vacuum degree is 1-10 Pa through the air outlet (7), and then the inert gas is injected into the pressing cavity (12) through the air inlet (8) to make the internal pressure of the pressing cavity (12) be 0.9-1 MPa; Step (3): the pressing head (5) is lowered to preliminarily press the material, the pressing head (5) continues to maintain the required pressure, the heating resistor (4) is started to perform pressing sintering on the preliminarily pressed material, and a titanium alloy preform is obtained; Step (4): the titanium alloy preform is cut into blocks, then is hot-rolled, is placed into a vacuum furnace (15) to perform annealing treatment, and a heterogeneous titanium alloy is obtained.

6. The method of claim 5, wherein, The surface of the titanium alloy block in step (1) is polished before milling to remove oil stains and oxides on the surface; The two titanium alloy blocks are alpha titanium alloy and beta titanium alloy respectively.

7. The method of claim 6, wherein, In step (3), the pressure head pressure is 43-46 MPa during pressing and sintering; the temperature for pressing and sintering is 1027-1400 ℃, and the titanium alloy preform is obtained by homogenizing for 30 min and then air cooling.

8. The method of claim 7, wherein, In step (4), the hot rolling is specifically performed at 1027-1400 ℃ for 2-10 min before rolling, and the deformation amount is 50%-85%; the annealing treatment in step (4) is specifically performed at 500-800 ℃ for 2-5 hours.

9. A heterogeneous titanium alloy, characterized in that, The isomeric titanium alloy prepared by the method of any one of claims 5-8 comprises an α phase Ti-Al, a β phase Ti-V, and an α+β dual-phase Ti-Al-V.

Images