Laser shock processing method for gradient heterostructure of TiVAl memory alloy

Abstract

The present invention discloses a laser shock treatment method for a gradient heterogeneous structure of a TiVAl memory alloy, comprising the following steps: S1, using sponge titanium, dendrite vanadium and high-purity Al particles as raw materials, and preparing a TiVAl light memory alloy with a total mass of 80g according to a chemical composition of Ti-13V-3Al atomic ratio; S2, placing the prepared raw materials in a vacuum arc melting furnace crucible according to the principle that low-melting-point pure Al particles are placed at the bottom of the crucible and high-melting-point dendrite vanadium is placed at the top of the crucible; S3, repeatedly melting the raw materials 4 times under the action of an electric arc to prepare a TiVAl alloy ingot with uniform composition. The present invention constructs a gradient structure in a Ti-V-Al light memory alloy through a unique processing method, which effectively broadens its martensitic phase transition temperature / stress window, thereby promoting its application field.

Description

Technical Field

[0001] The invention relates to the technical field of TiVAl memory alloys, in particular to a laser shock processing method for a TiVAl memory alloy gradient heterogeneous structure. Background Art

[0002] Ti-V-Al alloy has become one of the most promising lightweight memory alloys in the aerospace field due to its low density (4.5g / cm3), relatively low price, excellent processability (up to 90% or more), and adjustable phase transition temperature over a wide range. However, similar to traditional Ti-Ni-based memory alloys, the phase transition temperature / stress window (Ms(Af)-Mf(As) / σf-σr) of Ti-V-Al lightweight memory alloy is small, which makes the controllability of the actuator prepared from it poor.

[0003] Recently, in order to broaden the phase transition temperature / stress window to achieve precise control of shape memory alloy actuators, the concept of "functionally gradient memory alloy" has been proposed. Ways to obtain functionally gradient memory alloys include designing composition gradients, geometric size gradients, or structural gradients. Composition gradients can be achieved through diffusion annealing, magnetron sputtering, or additive manufacturing. However, it is difficult to accurately control the composition gradient in three-component alloys using the above methods. The gradient achieved by the geometric size gradient is not the gradient of the material's essential functional properties, but the gradient of the material's bearing capacity caused by changes in cross-sectional dimensions. The structural gradient mainly uses gradient annealing, severe surface plastic deformation, and laser surface heating to make the organizational structure elements (grain size, phase composition, and various defects, etc.) closely related to the martensitic phase transformation behavior present a gradient distribution in the memory alloy, which makes the martensitic phase transformation in different localized regions in the gradient structure different, thereby regulating the functional properties.

[0004] To this end, the present application proposes a laser shock processing method for a TiVAl memory alloy gradient heterostructure. Summary of the invention

[0005] The purpose of the present invention is to solve the above technical problems and to propose a laser shock processing method for a TiVAl memory alloy gradient heterostructure.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The laser shock processing method of TiVAl memory alloy gradient heterostructure comprises the following steps:

[0008] S1, using titanium sponge, dendrite vanadium and high-purity Al particles as raw materials, a TiVAl lightweight memory alloy with a total mass of 80g was prepared according to a chemical composition of Ti-13V-3Al atomic ratio;

[0009] S2, placing the prepared raw materials in a vacuum arc melting furnace crucible according to the principle of placing low melting point pure Al particles at the bottom of the crucible and high melting point dendrite vanadium at the top of the crucible;

[0010] S3, repeatedly melting the raw materials under the action of electric arc for 4 times to prepare a TiVAl alloy ingot with uniform composition;

[0011] S4, taking the TiVAl alloy ingot and melting it into liquid again so that it flows into a 40 mm×10 mm×7 mm copper mold under the action of gravity, and finally obtaining a 40 mm×10 mm×7 mm lath-shaped TiVAl lightweight memory alloy;

[0012] S5, hot rolling the lamellar TiVAl alloy at 900°C, with a reduction of 0.5 mm per hot rolling, until the lamellar TiVAl alloy has a thickness of 5 mm; then cold rolling is performed, with a reduction of 0.2 mm per hot rolling, and a total cold rolling amount of 60%, and the cold-rolled lamellar TiVAl alloy is subjected to a solution treatment at 900°C / 3h, and water quenching;

[0013] S6, polishing the plate-shaped TiVAl alloy to obtain a TiVAl alloy strip with bright surfaces on both sides;

[0014] S7, laser shock processing of TiVAl lightweight memory alloy using Nd:YAG laser equipment.

[0015] Preferably, before preparing the ingredients in S1, the raw materials of sponge titanium, dendrite vanadium and high-purity Al particles are placed in anhydrous ethanol for washing to remove various impurities.

[0016] Preferably, before smelting the alloy in S2, the furnace body is vacuumed to 10 -3 Pa, and 0.5Pa of high-purity argon gas is injected into the vacuum arc melting furnace.

[0017] Preferably, the alloy ingot is turned 180° after each smelting in S3.

[0018] Preferably, the laser wavelength in the laser device in S7 is 1064nm, the pulse width is 10ns, the laser energy is 0.83J, the laser beam spot dendrite is 1.5mm, the laser frequency is 10Hz, and a heat-resistant glass with a thickness of 3mm is used as a binding constraint layer during the processing, and aluminum foil is attached to the surface of the TiVAl lightweight memory alloy alluvial layer.

[0019] Preferably, in S7, the TiVAl lightweight memory alloy bottom layer is adhered to a heating platform, the bottom surface of the alloy is heated, and the temperature of the heating platform is adjusted to 500° C. during the laser shock process.

[0020] Preferably, the Nd:YAG laser equipment comprises a housing, in which a Nd:YAG laser is installed, a support plate is fixedly installed in the housing, a guide groove is provided at the upper end of the support plate, a slider is slidably connected in the guide groove, a drive screw is rotatably connected in the guide groove, the drive screw passes through the slider and is threadedly connected thereto, a motor is installed on the rear side of the support plate, the output end of the motor is fixedly connected to the drive screw, a mounting plate is fixed to the upper end of the slider, a limit plate is fixed to the upper end of the mounting plate, a slide groove is provided at the upper end of the limit plate, two moving blocks that can move synchronously are slidably connected in the slide groove, clamping plates are fixed on the two moving blocks, and the two clamping plates are used to clamp the TiVAl lightweight memory alloy.

[0021] Preferably, a first screw is rotatably connected in the slide groove, a second screw is fixed on the first screw, the other end of the second screw is rotatably connected to the inner wall of the slide groove, the thread directions of the first screw and the second screw are opposite, a round rod is fixed on the first screw, the round rod passes through the limit plate and is rotatably connected thereto, and a handle is fixed on the round rod.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention constructs a gradient structure in the Ti-V-Al light memory alloy through a unique processing method, which effectively broadens the martensitic phase transformation temperature / stress window thereof, thereby promoting its application field. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The microstructure of the Ti-V-Al lightweight shape memory alloy after laser shock treatment;

[0025] Figure 2 The Ti-V-Al lightweight shape memory alloys both subjected to laser shock and without laser shock exhibited an elastic stage, a stress-induced martensite reorientation stage, and a final plastic deformation stage.

[0026] Figure 3 It is a structural schematic diagram of the Nd:YAG laser device in the laser shock processing method of the TiVAl memory alloy gradient heterostructure proposed in the present invention;

[0027] Figure 4 This is a schematic structural diagram of the limiting plate in the laser shock processing method for the TiVAl memory alloy gradient heterostructure proposed in the present invention.

[0028] In the figure: 1 box, 2 Nd:YAG laser, 3 support plate, 4 guide groove, 5 slider, 6 motor, 7 drive screw, 8 mounting plate, 9 limit plate, 10 slide groove, 11 first screw, 12 second screw, 13 round rod, 14 handle, 15 moving block, 16 clamping plate. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0030] Reference Figure 1-Figure 4 , a laser shock processing method for a TiVAl memory alloy gradient heterostructure comprises the following steps:

[0031] S1, using titanium sponge, dendrite vanadium and high-purity Al particles as raw materials, a TiVAl lightweight memory alloy with a total mass of 80g was prepared according to a chemical composition of Ti-13V-3Al atomic ratio;

[0032] S2, placing the prepared raw materials in a vacuum arc melting furnace crucible according to the principle of placing low melting point pure Al particles at the bottom of the crucible and high melting point dendrite vanadium at the top of the crucible;

[0033] S3, repeatedly melting the raw materials under the action of electric arc for 4 times to prepare a TiVAl alloy ingot with uniform composition;

[0034] S4, taking the TiVAl alloy ingot and melting it into liquid again so that it flows into a 40 mm×10 mm×7 mm copper mold under the action of gravity, and finally obtaining a 40 mm×10 mm×7 mm lath-shaped TiVAl lightweight memory alloy;

[0035] S5, hot rolling the lamellar TiVAl alloy at 900°C, with a reduction of 0.5 mm per hot rolling, until the lamellar TiVAl alloy has a thickness of 5 mm; then cold rolling is performed, with a reduction of 0.2 mm per hot rolling, and a total cold rolling amount of 60%, and the cold-rolled lamellar TiVAl alloy is subjected to a solution treatment at 900°C / 3h, and water quenching;

[0036] S6, polishing the plate-shaped TiVAl alloy to obtain a TiVAl alloy strip with bright surfaces on both sides;

[0037] S7, laser shock processing of TiVAl lightweight memory alloy using Nd:YAG laser equipment.

[0038] In the present invention, before preparing the ingredients in S1, the raw materials of sponge titanium, dendrite vanadium and high-purity Al particles are placed in anhydrous ethanol for washing to remove various impurities.

[0039] In the present invention, before smelting the alloy in S2, the furnace body is vacuumed to 10 -3 Pa, 0.5Pa of high-purity argon gas is rushed into the vacuum arc melting furnace to play the role of arc starting.

[0040] In the present invention, in order to ensure the uniformity of chemical composition, the alloy ingot is turned 180° after each smelting in S3.

[0041] In the present invention, the laser wavelength in the laser device S7 is 1064nm, the pulse width is 10ns, the laser energy is 0.83J, the laser beam spot dendrite is 1.5mm, the laser frequency is 10Hz, and a heat-resistant glass with a thickness of 3mm is used as a binding constraint layer during the processing, and aluminum foil is attached to the surface of the TiVAl lightweight memory alloy alluvial layer.

[0042] In the present invention, the TiVAl lightweight memory alloy bottom layer in S7 is adhered to a heating platform, the bottom surface of the alloy is heated, and the temperature of the heating platform is adjusted to 500° C. during the laser impact process.

[0043] The present invention specifically polishes the plate-shaped TiVAl alloy by using a series of grinding wheel machine rough grinding → angle grinder grinding → coarse (180# sandpaper) sandpaper → 600# sandpaper → 1200# sandpaper in sequence to obtain a TiVAl alloy strip with bright surfaces on both sides.

[0044] In order to improve the laser impact effect in the present invention, the laser processing path is "S" shaped, and the spot overlap rate is 50%.

[0045] Depend on Figure 1 It can be seen that the microstructure of the Ti-V-Al lightweight memory alloy treated by laser shock treatment presents an obvious gradient heterogeneous structure. Among them, the bottom heating surface to the impact surface is successively strengthened by α precipitated phase β parent phase → single β parent phase → single α ˊˊ Martensite phase. Moreover, the thickness of the β matrix layer strengthened by the α precipitation phase is about 35μm; the single β matrix layer is about 267μm, followed by a single α with a thickness of 1698μm. ˊˊ Martensite phase layer; among them, Figure 1 Middle (a): metallographic image of bottom heating surface; (b): metallographic image of impact surface; (c): EBSD image of bottom heating surface; (d): EBSD image of impact surface;

[0046] Depend on Figure 2It can be seen that both laser-shocked and non-laser-shocked Ti-V-Al lightweight shape memory alloys present an elastic stage, a stress-induced martensite reorientation stage, and a final plastic deformation stage. In comparison, the yield strength and ultimate tensile strength of the laser-shocked Ti-V-Al lightweight shape memory alloy are significantly improved compared to the non-laser-shocked Ti-V-Al lightweight shape memory alloy. After laser shock treatment, the yield strength increased from 398MPa to 584MPa, and the ultimate tensile strength increased from 643MPa to 824MPa. The elongation decreased from 39.3% to 30.3%.

[0047] In addition, the Nd:YAG laser device includes a box body 1, on which a switch door is installed; a Nd:YAG laser 2 is installed in the box body 1, a support plate 3 is fixedly installed in the box body 1, a guide groove 4 is provided at the upper end of the support plate 3, a slider 5 is slidably connected in the guide groove 4, a driving screw 7 is rotatably connected in the guide groove 4, the driving screw 7 passes through the slider 5 and is threadedly connected thereto, a motor 6 is installed on the rear side of the support plate 3, an output end of the motor 6 is fixedly connected to the driving screw 7, a mounting plate 8 is fixed at the upper end of the slider 5, a limit plate 9 is fixed at the upper end of the mounting plate 8, a slide groove 10 is provided at the upper end of the limit plate 9, two moving blocks 15 that can move synchronously are slidably connected in the slide groove 10, clamping plates 16 are fixed on the two moving blocks 15, and the two clamping plates 16 are used to clamp the TiVAl lightweight memory alloy;

[0048] A first screw rod 11 is rotatably connected in the slide groove 10, a second screw rod 12 is fixed on the first screw rod 11, the other end of the second screw rod 12 is rotatably connected to the inner wall of the slide groove 10, the thread directions of the first screw rod 11 and the second screw rod 12 are opposite, a round rod 13 is fixed on the first screw rod 11, the round rod 13 passes through the limit plate 9 and is rotatably connected thereto, and a handle 14 is fixed on the round rod 13.

[0049] When in use, the motor 6 is started, and the motor 6 drives the driving screw 7 to rotate. Since the slider 5 cannot rotate in the guide groove 4, the driving screw 7 can drive the slider 5 to move. The movement of the slider 5 drives the mounting plate 8 and the limit plate 9 to move, so that the limit plate 9 is close to the switch door position of the box body 1, and then the alloy is placed between the two clamping plates 16. The staff rotates the handle 14, and the rotation of the handle 14 drives the first screw 11 and the second screw 12 to rotate. Since the thread directions of the first screw 11 and the second screw 12 are opposite, and the moving block 15 cannot move, the two moving blocks 15 can be moved relative to each other, and the clamping plate 16 can be used to clamp and position the alloy.

[0050] Then, the motor 6 is started to reverse, and the heating table is started. When the temperature of the heating table rises to 500°C and is kept warm for 30 minutes, the clamped alloy is transported to the bottom of the Nd:YAG laser 2, and the alloy is processed by the Nd:YAG laser 2. During the processing, the heating table is kept at 500°C; wherein, the heating table is installed on the limit plate 9, which is not shown in the figure.

[0051] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A laser shock treatment method for TiVAl memory alloy gradient heterostructure, characterized in that: The following steps are involved: S1, using titanium sponge, dendrite vanadium and high-purity Al particles as raw materials, a TiVAl lightweight memory alloy with a total mass of 80g was prepared according to a chemical composition of Ti-13V-3Al atomic ratio; S2, placing the prepared raw materials in a vacuum arc melting furnace crucible according to the principle of placing low melting point pure Al particles at the bottom of the crucible and high melting point dendrite vanadium at the top of the crucible; S3, repeatedly melting the raw materials under the action of electric arc for 4 times to prepare a TiVAl alloy ingot with uniform composition; S4, taking the TiVAl alloy ingot and melting it into liquid again so that it flows into a 40 mm×10 mm×7 mm copper mold under the action of gravity, and finally obtaining a 40 mm×10 mm×7 mm lath-shaped TiVAl lightweight memory alloy; S5, hot rolling the lamellar TiVAl alloy at 900°C, with a reduction amount of 0.5 mm for each hot rolling, until the lamellar TiVAl alloy has a thickness of 5 mm; then cold rolling is performed, with a reduction amount of 0.2 mm for each hot rolling, and a total cold rolling amount of 60%, and the cold-rolled lamellar TiVAl alloy is subjected to a solid solution treatment at 900°C / 3h, and water quenching is performed; S6, polishing the plate-shaped TiVAl alloy to obtain a TiVAl alloy strip with bright surfaces on both sides; S7, laser shock treatment of TiVAl lightweight memory alloy is performed using Nd: YAG laser equipment, wherein the laser wavelength is 1064nm, the pulse width is 10ns, the laser energy is 0.83J, the laser beam spot dendrite is 1.5mm, the laser frequency is 10Hz, and a heat-resistant glass with a thickness of 3mm is used as a restraining constraint layer during the treatment process, and aluminum foil is attached to the surface of the TiVAl lightweight memory alloy alluvial layer.

2. The laser shock processing method for TiVAl memory alloy gradient heterostructure according to claim 1, characterized in that: Before preparing the ingredients in S1, the raw materials of sponge titanium, dendrite vanadium and high-purity Al particles are placed in anhydrous ethanol for cleaning to remove various impurities.

3. The laser shock processing method for TiVAl memory alloy gradient heterostructure according to claim 1, characterized in that: Before melting the alloy in S2, the furnace body is vacuumed to 10 -3 Pa, and 0.5Pa of high-purity argon gas is injected into the vacuum arc melting furnace.

4. The laser shock processing method for TiVAl memory alloy gradient heterostructure according to claim 1, characterized in that: After each smelting in S3, the alloy ingot is turned 180°.

5. The laser shock processing method for TiVAl memory alloy gradient heterostructure according to claim 1, characterized in that: In the S7, the TiVAl light memory alloy bottom layer is adhered to a heating platform, and the bottom surface of the alloy is heated. During the laser shock process, the temperature of the heating platform is adjusted to 500°C.

6. The laser shock processing method for TiVAl memory alloy gradient heterostructure according to claim 1, characterized in that: The Nd:YAG laser device comprises a housing (1), in which an Nd: YAG laser (2), a support plate (3) is fixedly installed in the box (1), a guide groove (4) is provided at the upper end of the support plate (3), a slider (5) is slidably connected in the guide groove (4), a driving screw (7) is rotatably connected in the guide groove (4), the driving screw (7) passes through the slider (5) and is threadedly connected thereto, a motor (6) is installed on the rear side of the support plate (3), the output end of the motor (6) is fixedly connected to the driving screw (7), a mounting plate (8) is fixed at the upper end of the slider (5), a limit plate (9) is fixed at the upper end of the mounting plate (8), a slide groove (10) is provided at the upper end of the limit plate (9), two moving blocks (15) that can move synchronously are slidably connected in the slide groove (10), a clamping plate (16) is fixed on each of the two moving blocks (15), and the two clamping plates (16) are used to clamp the TiVAl light memory alloy.

7. The laser shock processing method for TiVAl memory alloy gradient heterostructure according to claim 6, characterized in that: A first screw rod (11) is rotatably connected in the slide groove (10), a second screw rod (12) is fixed on the first screw rod (11), the other end of the second screw rod (12) is rotatably connected to the inner wall of the slide groove (10), the thread directions of the first screw rod (11) and the second screw rod (12) are opposite, a round rod (13) is fixed on the first screw rod (11), the round rod (13) passes through the limiting plate (9) and is rotatably connected thereto, and a handle (14) is fixed on the round rod (13).

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