A method for preparing ultra-high strain rate deformation of tungsten alloy with dual-phase nanotwin structure

Abstract

The application relates to the field of tungsten alloy preparation, in particular to a method for preparing a tungsten alloy with a dual-phase nanotwin structure through ultrahigh strain rate deformation. The method is characterized in that: a proper thickness of a constraint layer is applied to the front and back surfaces of a tungsten alloy sample to constrain laser shock waves, control the reflection and refraction paths and impact force of the laser shock waves; then laser impact treatment is carried out with a laser with a beam diameter of 1-5 mm, a pulse width of 1-10 ns, a wavelength of 300-800 nm, a laser energy of 100-300 J and a repetition frequency of 0.1-10 Hz; and the tungsten alloy sheet is prepared from the following components in mass percent: Ni 3-8%; Fe 1.2-3.5%; and the balance being W and inevitable impurities. In the dual-phase nanotwin structure tungsten alloy prepared by the method, the hardness of tungsten particles is increased by 60-80%, the hardness of the gamma-(Ni, Fe) binder phase is increased by 10-20%, and the ultimate tensile strength is increased by 5-10 times, and the preparation process is simple, efficient, low in cost and pollution-free.

Description

Technical Field

[0001] This invention relates to the field of tungsten alloy preparation, and specifically to a method for preparing tungsten alloys with a dual-phase nanotwin structure using ultra-high strain rate deformation. Background Technology

[0002] Tungsten alloys are two-phase alloys composed of tungsten particles and a matrix phase. The tungsten particles impart high strength to the alloy, while the matrix phase, composed of elements such as Ni, Fe, Cu, and Co, provides toughness. This gives tungsten alloys advantages such as high strength, high toughness, and high density, leading to their widespread application in advanced weaponry and defense. Examples include the manufacture of large-caliber kinetic energy penetrator cores, shaped charge shields for shaped charge projectiles, and the outer rotor bodies of gyroscopes in ships and tanks. With the increasing complexity of modern warfare environments, higher demands are placed on the strength and toughness of tungsten alloys to meet the service requirements of weapons and equipment operating in extreme environments. Traditional powder metallurgy sintered W-Ni-Fe alloys exhibit high toughness (elongation of approximately 30%), but their matrix phase strength and modulus are low, with a tensile strength of only about 900 MPa, limiting further applications of tungsten alloys. While conventional solid solution strengthening and deformation strengthening methods can improve alloy strength, they may lead to interfacial mismatch, thus reducing toughness. Therefore, to address this issue, it is necessary to restructure and reshape the alloy structure to achieve a better balance between strength and toughness.

[0003] Laser shock irradiation is an ultra-high strain rate surface plastic deformation technique capable of fabricating gradient nanostructures and generating deep residual compressive stress. This technique uses short-pulse (nanosecond, picosecond, and femtosecond) high-power lasers to irradiate metallic materials, absorbing energy into the material's surface absorption layer, triggering explosive vaporization and forming high-temperature and high-pressure plasma (temperature > 10⁷ K, pressure > GPa). The plasma continuously absorbs laser energy, expanding violently and forming a laser shock wave. When the plasma pressure exceeds the metal's elastic limit, dynamic plastic deformation occurs. Simultaneously, the grain size of the metallic material is refined to submicron or nanoscale, forming gradient nanostructures and generating deeper residual compressive stress. The interaction of the gradient nanostructures and residual compressive stress leads to the formation of numerous dislocation groups, dislocation tangles, dislocation stacks, and nanotwins within the material.

[0004] Nanotwinned structures are microstructures of materials with nanocrystal size and twinning structure, playing a significant role in enhancing material strength and toughness. Due to the numerous grain boundaries present in nanotwinned structures, dislocation and slip motion are hindered, increasing material strength and hardness, limiting crack propagation, and enhancing toughness. Simultaneously, residual stress introduced during fabrication provides additional compressive force, further enhancing material properties. Furthermore, the small grain size in nanotwinned structures leads to a greater grain boundary hindrance effect and difficult diffusion paths, limiting plastic deformation and thus improving material strength and toughness. Through the synergistic effect of grain boundary strengthening, residual stress, and grain size, nanotwinned structures can significantly improve material properties and possess broad application potential. Therefore, the fabrication of tungsten alloys with dual-phase nanotwinned structures using ultra-high strain rate deformation via laser shock can solve the interfacial mismatch problem and achieve a better balance between strength and toughness. Summary of the Invention

[0005] To address the shortcomings of existing technologies, such as the inability of traditional W-Ni-Fe alloys to meet the strength and hardness requirements of various complex service environments, and the inability of strengthening methods to resolve interfacial mismatch and achieve a better strength-toughness balance, the first objective of this invention is to provide a method for preparing tungsten alloys with a dual-phase nanotwin structure using ultra-high strain rate deformation. This method can enhance the strength and hardness of W-Ni-Fe alloy materials, resolve the interfacial mismatch problem, achieve a better strength-toughness balance, and is simple to operate, low in cost, environmentally friendly, and highly effective.

[0006] The second objective of this invention is to provide a W-Ni-Fe alloy with a dual-phase nanotwin structure prepared by the above-described preparation method.

[0007] The W-Ni-Fe alloy comprises, by mass percentage: Ni 3-8%; Fe 1.2-3.5%; the balance being W and unavoidable impurities;

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing tungsten alloys with a dual-phase nanotwin structure by ultra-high strain rate deformation is disclosed. This method utilizes laser shock calorimetry to deform the tungsten alloy material under ultra-high strain rate loading to obtain the nanotwin structure. The method specifically includes the following steps:

[0010] (1) Surface pretreatment of tungsten alloy thin plate: Before laser shock treatment, the surface of tungsten alloy thin plate sample with a thickness of 50-2000μm is pretreated to obtain a clean and dry tungsten alloy thin plate; the material of the tungsten alloy thin plate, by mass percentage, includes the following components: Ni 3-8%; Fe 1.2-3.5%; balance is W and unavoidable impurities.

[0011] In industrial applications, polishing machines (including fully automatic, semi-automatic, and manual polishing machines) are used to grind and polish the surface of tungsten alloy materials with a thickness of 50–2000 μm to ensure that there is no residual oxide layer or other impurities.

[0012] The preferred method is to use a diamond fine pre-polishing disc instead of 80#, 200#, 320#, 600#, and 1200# SiC wet sandpaper for all pre-polishing steps, and use diamond polishing agents with particle sizes of 10μm, 3.5μm, and 0.5μm for mechanical polishing. The polishing disc rotation speed is 100–500 rpm / min, the fixed disc rotation speed is 30–150 rpm / min, and the air pressure column pressure is 10–70 N.

[0013] The inventors discovered that during the pre-polishing of tungsten alloys, due to their extremely high hardness, conventional SiC wet sandpaper cannot achieve optimal flatness. However, a diamond fine pre-polishing disc, with its exceptionally high material removal capacity, can effectively replace SiC wet sandpaper for all pre-polishing steps. Utilizing the ultra-high hardness of diamond and its honeycomb structure to further optimize the abrasive's action, optimal material flatness is maintained during pre-polishing. By controlling the diamond abrasive particle size of the diamond fine pre-polishing disc and combining it with diamond polishing agents of different particle sizes, different stages of processing effects and surface quality requirements can be achieved.

[0014] When processing a 90W-7Ni-3Fe alloy sample, the preferred configuration is: polishing disc rotation speed 150 rpm / min, fixed disc rotation speed 60 rpm / min, and air pressure column pressure 30 N.

[0015] When processing a 93W-4.9Ni-2.1Fe alloy, the preferred configuration is: polishing disc rotation speed 200 rpm / min, fixed disc rotation speed 90 rpm / min, and air pressure column pressure 40 N.

[0016] When the sample being processed is a 95W-3.5Ni-1.5Fe alloy, the preferred configuration is: polishing disc rotation speed 250 rpm / min, fixed disc rotation speed 120 rpm / min, and air pressure column pressure 50 N.

[0017] After the tungsten alloy material surface is ground and polished, it is cleaned to ensure that there are no residual diamonds or other impurities.

[0018] In a preferred embodiment, the sample is placed in anhydrous ethanol and then in an ultrasonic cleaner. The ultrasonic frequency is set to 30–80 kHz, the cleaning temperature to 20–25 °C, and the ultrasonic oscillation cleaning is performed for 3–10 minutes. After cleaning, the sample is placed in deionized water within the ultrasonic cleaner, and the ultrasonic frequency is set to 0–80 kHz, the cleaning temperature to 20–25 °C, and the ultrasonic oscillation cleaning is performed for 3–10 minutes. Finally, the sample is removed, and the surface is dried using a 0.3–1 MPa nitrogen gas gun.

[0019] The inventors discovered that anhydrous ethanol possesses excellent solvent properties, effectively removing surface grease, organic impurities, and dirt. Ultrasonic waves generate high-frequency vibrations in liquids, forming microbubbles. These bubbles, upon collapse, produce strong localized impact forces, effectively removing dirt. However, excessively high ultrasonic frequencies and temperatures can cause microparticles to peel off, leading to surface damage. Simultaneously, prolonged ultrasonic fields can cause stress and dislocation effects on material grains, exceeding the material's original lattice capabilities, potentially leading to grain growth and damaging the material structure. Conversely, excessively low ultrasonic frequencies and temperatures cannot completely remove surface organic matter and impurities. To ensure surface purity, ultrasonic cleaning with deionized water is necessary to remove residual anhydrous ethanol and other impurities. However, it is important to note that residual moisture may remain on the sample surface after ultrasonic cleaning with deionized water, which can easily lead to oxidation and corrosion.

[0020] Nitrogen, a dry, colorless, and odorless gas, contains no moisture or impurities and can effectively dry the surface of tungsten alloy materials, preventing residual moisture from causing corrosion. When using a nitrogen gas gun, it is necessary to select an appropriate pressure to ensure effective moisture removal without damaging the metal surface.

[0021] A further optimized solution is as follows: during ultrasonic oscillation cleaning with anhydrous ethanol and deionized water, the ultrasonic frequency is 50KHz, the temperature is 25℃, and the time is 5min; finally, it is dried with nitrogen gas, and the nitrogen gas gun pressure is 0.5MPa.

[0022] (2) Applying a constraint layer: A clean and dry tungsten alloy sheet is installed on the workbench, and an optically transparent glass constraint layer is applied to the front and back sides respectively to restrict the free deformation of the material and regulate the plastic deformation and residual stress distribution caused by laser shock.

[0023] In a preferred embodiment, an optically transparent glass constraint layer with a thickness of 50 to 1000 μm is applied to both the front and back sides, and the thickness of a single optically transparent glass constraint layer is 1 / 3 to 3 / 5 of the thickness of the tungsten alloy.

[0024] The inventors discovered that an appropriately thick confinement layer can improve the strength and durability of tungsten alloys and prevent cracking or excessive deformation. The front confinement layer protects and isolates the tungsten alloy surface, preventing excessive damage and deformation from laser shock waves and preventing surface cracks. It also controls the propagation range of the laser shock wave, ensuring uniform impact force on the tungsten alloy surface. The back confinement layer primarily functions as a support and reflector, slowing down or hindering the propagation of the shock wave by supporting the metal material. This helps reduce internal stress and deformation, improving fatigue life and resistance to crack propagation. Therefore, the thickness of the confinement layer is crucial for the fabrication of biphase nanotwinned tungsten alloys using ultra-high strain rate deformation. An excessively thick confinement layer may lead to stress concentration, reduced laser shock deformation effectiveness, and increased processing difficulty; an excessively thin confinement layer may result in ineffective confinement, excessive material deformation, or even cracking.

[0025] In a further preferred embodiment, the thickness of the optically transparent glass constraint layer is 1 / 3 to 1 / 2 of the thickness of the tungsten alloy material.

[0026] When processing a 90W-7Ni-3Fe alloy with dimensions of 10mm×10mm×0.1mm, the preferred solution is to use an optically transparent glass constraint layer with a thickness of 50μm.

[0027] When processing a 10mm×10mm×0.5mm 90W-7Ni-3Fe alloy sample, the preferred solution is: the thickness of the optically transparent glass constraint layer is 250μm.

[0028] When processing a 10mm×10mm×1.5mm 90W-7Ni-3Fe alloy sample, the preferred solution is: the thickness of the optically transparent glass constraint layer is 500μm.

[0029] When processing a 90W-7Ni-3Fe alloy with dimensions of 5mm×5mm×0.5mm, the preferred solution is to use an optically transparent glass constraint layer with a thickness of 200μm.

[0030] When processing a 10mm×10mm×0.5mm 93W-4.9Ni-2.1Fe alloy sample, the preferred solution is: the thickness of the optically transparent glass constraint layer is 250μm.

[0031] When processing a 93W-4.9Ni-2.1Fe alloy with dimensions of 5mm×5mm×0.5mm, the preferred solution is to use an optically transparent glass constraint layer with a thickness of 200μm.

[0032] When processing a 10mm×10mm×0.5mm 95W-3.5Ni-1.5Fe alloy sample, the preferred solution is: the thickness of the optically transparent glass constraint layer is 250μm.

[0033] When processing a 95W-3.5Ni-1.5Fe alloy with dimensions of 5mm×5mm×0.5mm, the preferred solution is to use an optically transparent glass constraint layer with a thickness of 200μm.

[0034] (3) Laser shock treatment: The working end face of the tungsten alloy sample with the applied constraint layer is facing the laser beam, and the laser beam with a beam diameter of 1-5 mm, a pulse width of 1-10 ns, a wavelength of 300-800 nm, a laser energy of 100-300 J, and a repetition frequency of 0.1-10 Hz is used for shock treatment.

[0035] The inventors discovered that when preparing biphase nanotwinned tungsten alloys using ultra-high strain rate deformation via laser shock, laser energy, pulse width, wavelength, repetition frequency, and beam diameter all affect the preparation process and results. Higher laser energy and appropriate pulse width can achieve higher strain rates and deformation speeds, but excessively high or short pulses may lead to damage or overheating. Different laser wavelengths produce different processing methods for the materials, while appropriate repetition frequencies and beam diameters can improve processing efficiency and uniformity. Parameter control is crucial in preparing nanotwinned materials; adjustments must be made according to specific requirements and equipment conditions to achieve optimal results.

[0036] When processing a 90W-7Ni-3Fe alloy sample measuring 10mm×10mm×0.1mm, the preferred configuration is: beam diameter 2mm, pulse width 2ns, wavelength 527nm, laser energy 120J, and repetition frequency 0.5Hz.

[0037] When processing a 90W-7Ni-3Fe alloy sample of 10mm×10mm×0.5mm, the preferred configuration is: beam diameter 2mm, pulse width 5ns, wavelength 527nm, laser energy 180J, and repetition frequency 5Hz.

[0038] When processing a 10mm×10mm×1.5mm 90W-7Ni-3Fe alloy sample, the preferred configuration is: beam diameter 2mm, pulse width 8ns, wavelength 527nm, laser energy 280J, and repetition frequency 10Hz.

[0039] When processing a 90W-7Ni-3Fe alloy with dimensions of 5mm×5mm×0.5mm, the preferred configuration is: beam diameter 1mm, pulse width 3ns, wavelength 527nm, laser energy 150J, and repetition frequency 4Hz.

[0040] When processing a 10mm×10mm×0.5mm 93W-4.9Ni-2.1Fe alloy sample, the preferred configuration is: beam diameter 2mm, pulse width 5ns, wavelength 527nm, laser energy 200J, and repetition frequency 5Hz.

[0041] When processing a 5mm×5mm×0.5mm 93W-4.9Ni-2.1Fe alloy sample, the preferred scheme is: beam diameter 1mm, pulse width 3ns, wavelength 527nm, laser energy 170J, and repetition frequency 4Hz.

[0042] When processing a 95W-3.5Ni-1.5Fe alloy with dimensions of 10mm×10mm×0.5mm, the preferred configuration is: beam diameter 2mm, pulse width 4ns, wavelength 527nm, laser energy 220J, and repetition frequency 6Hz.

[0043] When processing a 95W-3.5Ni-1.5Fe alloy with dimensions of 5mm×5mm×0.5mm, the preferred configuration is: beam diameter 1mm, pulse width 3ns, wavelength 527nm, laser energy 190J, and repetition frequency 5Hz.

[0044] (4) Laser shock post-treatment: After laser shock treatment, the product is cleaned and then dried with nitrogen to obtain the product; the product has a biphase nanotwin structure.

[0045] In industrial applications, after laser shock annealing, the tungsten alloy with a dual-phase nanotwin structure prepared by ultra-high strain rate deformation must be cleaned to ensure that no residual impurities remain on the sample. The preferred method is: ultrasonic cleaning with anhydrous ethanol and deionized water at a frequency of 30–50 kHz, a temperature of 20–25 °C, and a time of 3–5 min; the nitrogen gas gun pressure is 0.1–0.5 MPa.

[0046] The inventors discovered that, due to the successful fabrication of a dual-phase nanotwinned tungsten alloy using a laser-impact ultra-high strain rate deformation method, the cleaning process differs from surface cleaning after grinding and polishing. This stage requires a lower ultrasonic frequency and shorter ultrasonic duration. This is to prevent surface damage caused by excessively high ultrasonic frequencies and temperatures, and to avoid grain growth under prolonged ultrasonic field conditions, which could destroy the nanotwinned structure.

[0047] A further preferred method is: ultrasonic oscillation cleaning with anhydrous ethanol and deionized water, with an ultrasonic frequency of 40 kHz, a temperature of 25 °C, and a time of 3 min; and a nitrogen gas gun pressure of 0.3 MPa.

[0048] This invention provides a high-strength, high-hardness, and high-toughness biphase nanotwinned tungsten alloy prepared by the above-mentioned ultra-high strain rate deformation method.

[0049] Beneficial effects

[0050] The laser shock technology scheme designed in this invention is used as a method for preparing ultra-high strain rate deformation. By inducing elastoplastic deformation of tungsten alloy samples, residual compressive stress is generated, which first forms a large number of dislocation groups, dislocation entanglements and dislocation pile-ups inside the sample, and then further forms a nanocrystalline twin structure, finally obtaining a two-phase nanocrystalline tungsten alloy.

[0051] This invention, through the design of a reasonable material surface grinding and polishing scheme, material surface cleaning scheme, laser shock post-treatment scheme, and a constraint layer of appropriate thickness, can effectively prevent the initiation of microcracks on the sample surface and the occurrence of back-side delamination, while ensuring the effective utilization of the laser shock wave of the sample and reducing energy dissipation.

[0052] This invention, by designing appropriate laser shock parameters, including pulse width, wavelength, laser energy, repetition frequency, and beam diameter, can increase the hardness of tungsten particles in tungsten alloy materials by 60% to 80%, the hardness of the γ-(Ni,Fe) binder phase by 10% to 20%, and the ultimate tensile strength by 5 to 10 times.

[0053] The dual-phase nanotwinned tungsten alloy provided by this invention can be applied not only in the military field to manufacture large-caliber kinetic energy penetrator cores, shaped charge shields for shaped charge projectiles, and gyro outer rotor bodies for ships, tanks, and other weapons, but also in the aerospace field to manufacture key components such as turbine blades, guide vanes, and nozzles for aero-engines, as well as in the automotive industry to manufacture friction plates, clutch plates, and fuel injectors for braking systems, thus greatly expanding the application range of tungsten alloys. Attached Figure Description

[0054] Figure 1 The images show the scanning electron microscope (SEM) morphology and X-ray diffraction (XRD) patterns of the original 90W-7Ni-3Fe alloy sample used in Example 1: (a) is the SEM morphology image; (b) is the XRD pattern.

[0055] Figure 2 The images show the hardness data of the 90W-7Ni-3Fe alloy sample with a dual-phase nanotwin structure obtained in Example 1 and the original sample, as well as the free surface velocity curve. Among them, (a) is the hardness data graph of the nanotwin W particles and γ-(Ni,Fe) binder phase compared with the original sample; (b) is the free surface velocity curve.

[0056] Figure 3 The transmission electron microscope (TEM) analysis of the W particle region of the 90W-7Ni-3Fe alloy sample with a dual-phase nanotwin structure obtained in Example 1 is shown below. (a) is a bright-field TEM image; (b) is a magnified bright-field TEM image of the W particle region in (a); (c) is a high-resolution TEM image; and (d) is a selected-area electron diffraction pattern.

[0057] Figure 4 The transmission electron microscope (TEM) analysis of the γ-(Ni,Fe) binder phase region of the 90W-7Ni-3Fe alloy sample with a dual-phase nanotwin structure obtained in Example 1 is shown below. (a) is a bright-field TEM image; (b) is a magnified bright-field TEM image of the γ-(Ni,Fe) binder phase region in (a); (c) is a high-resolution TEM image; and (d) is a selected-area electron diffraction pattern.

[0058] Figure 5 Transmission electron microscopy (TEM) analysis of the 90W-7Ni-3Fe alloy sample obtained in Comparative Example 1 is shown below. (a) is a bright-field TEM image; (b) is a magnified bright-field TEM image of the W-particle region in (a); (c) is a selected-area electron diffraction (SEG) pattern of the W-particle region in (b); (d) is a magnified bright-field TEM image of the γ-(Ni,Fe) binder phase region in (a); and (e) is a selected-area electron diffraction (SEG) pattern of the γ-(Ni,Fe) binder phase in (d).

[0059] Figure 6 Transmission electron microscopy (TEM) analysis of the 90W-7Ni-3Fe alloy sample obtained in Comparative Example 2; where (a) is a bright-field TEM image; (b) is a magnified bright-field TEM image of the W-particle region in (a); (c) is a selected-area electron diffraction (SED) pattern of the W-particles in (b); (d) is a magnified bright-field TEM image of the γ-(Ni,Fe) binder phase region in (a); and (e) is a selected-area electron diffraction (SED) pattern of the γ-(Ni,Fe) binder phase in (d).

[0060] Figure 7 Transmission electron microscopy analysis of the pure W sample obtained in Comparative Example 6; where (a) is a bright-field image of the transmission electron microscope; (b) is a bright-field image of a magnified area of ​​(a) of the transmission electron microscope; (c) is a selected area electron diffraction pattern of the transmission electron microscope; and (d) is a high-resolution image of the transmission electron microscope.

[0061] from Figure 1 It was found that the 90W-7Ni-3Fe alloy used in Example 1 was composed of body-centered cubic spherical W particles with a size of 20-50 μm and face-centered cubic irregularly shaped γ-(Ni,Fe) binder phase.

[0062] from Figure 2 The study found that the γ-(Ni,Fe) binder phase of the 90W-7Ni-3Fe alloy sample with a dual-phase nanotwin structure obtained in Example 1 showed a 50% increase in hardness and a 67% increase in hardness of the W particles; the frontal compressive strain rate was 6.88 × 10⁻⁶. 8 s-1 Backside tensile strain rate: 2.07 × 10⁻⁶ 6 s -1 Loading time: 1.4 ns; ultimate tensile strength: 9.87 GPa.

[0063] from Figure 3 It was found that in Example 1, the 90W-7Ni-3Fe alloy underwent ultra-high strain rate deformation by laser shock, and obvious twins appeared in the W particles. The twins were mirror-symmetric along the (211) crystal plane, with included angles of 80° and 75° respectively.

[0064] from Figure 4 It was found that in Example 1, after the 90W-7Ni-3Fe alloy underwent ultra-high strain rate deformation by laser shock, obvious twins appeared in the γ-(Ni,Fe) binder phase. The twins were mirror-symmetric along the (220) crystal plane, with included angles of 88° and 85° respectively.

[0065] from Figure 5 It was found that in Comparative Example 1, the 90W-7Ni-3Fe alloy, after ultra-high strain rate deformation by laser shock, had a large number of dislocation entanglements inside the W particles and γ-(Ni,Fe) binder phase, forming a complex dislocation network. No twins were found, and both the W particles and γ-(Ni,Fe) binder phase were single crystals.

[0066] from Figure 6 In Comparative Example 2, the 90W-7Ni-3Fe alloy underwent ultra-high strain rate deformation via laser shock, resulting in the formation of numerous lath-shaped subgrains within the W particles. Subgrains and recrystallized grains appeared within the γ-(Ni,Fe) binder phase, but no twins were observed.

[0067] from Figure 7 In the study, it was found that in the pure W sample of Comparative Example 6, after ultra-high strain rate deformation by laser shock, a small number of light and dark striped regions were found in the W phase. Combined with electron diffraction patterns and high-resolution images, it was confirmed that they were twins with a width of 20-100 nm but a length of several hundred micrometers. Detailed Implementation

[0068] Example 1

[0069] A method for preparing an ultra-high strain rate deformation alloy with a dual-phase nanotwin structure of 90W-7Ni-3Fe includes the following steps:

[0070] Step 1: Surface grinding and polishing

[0071] Take a 90W-7Ni-3Fe alloy with dimensions of 10mm×10mm×0.5mm, and use a diamond fine pre-polishing disc to replace 80#, 200#, 320#, 600#, and 1200# SiC wet sandpaper to polish the surface in sequence. Use diamond polishing agents with particle sizes of 10μm, 3.5μm, and 0.5μm for mechanical polishing. The polishing disc rotation speed is 150 rpm / min, the fixed disc rotation speed is 60 rpm / min, and the air pressure column pressure is 30N.

[0072] Step 2: Surface cleaning

[0073] The polished sample was cleaned sequentially with anhydrous ethanol and deionized water using ultrasonic oscillation at a frequency of 60 kHz, a temperature of 25 °C, and a time of 5 min. The surface moisture was then dried using a nitrogen gas gun with a pressure of 0.5 MPa.

[0074] Step 3: Apply constraint layers

[0075] The cleaned sample is mounted on the worktable, and a 250μm thick optically transparent glass constraint layer is applied to the front and back sides respectively.

[0076] Step 4: Laser shock treatment

[0077] The working end face of the sample with the applied constraint layer is faced with the laser beam, and impact treatment is performed with a laser beam diameter of 2 mm, pulse width of 5 ns, wavelength of 527 nm, laser energy of 180 J, and repetition frequency of 5 Hz.

[0078] Step 5: Laser Shock Post-processing

[0079] The laser-treated samples were sequentially cleaned with anhydrous ethanol and deionized water using ultrasonic oscillation at a frequency of 40 kHz, a temperature of 25 °C, and a time of 3 min. The surface moisture was then dried using a nitrogen gas gun with a pressure of 0.3 MPa.

[0080] After ultra-high strain rate deformation using laser shock, the hardness of the γ-(Ni,Fe) binder phase of the 90W-7Ni-3Fe alloy with a dual-phase nanotwin structure increased from 4.63 GPa to 6.95 GPa, the hardness of the W particles increased from 7.24 GPa to 12.09 GPa, and the ultimate tensile strength increased to 9.87 GPa. A nanotwin structure was formed in the W particles and the γ-(Ni,Fe) binder phase.

[0081] Further exploration revealed:

[0082] When processing 90W-7Ni-3Fe alloy with dimensions of 10mm × 10mm × 0.1mm, the preferred configuration is: a confinement layer thickness of 50μm, a beam diameter of 2mm, a pulse width of 2ns, a wavelength of 527nm, a laser energy of 120J, and a repetition frequency of 0.5Hz. The resulting product exhibits a hardness of 6.66GPa for the γ-(Ni,Fe) binder phase, a hardness of 11.23GPa for the W particles, and an ultimate tensile strength of 9.65GPa. A nanotwin structure is formed in the W particles and the γ-(Ni,Fe) binder phase.

[0083] When processing 90W-7Ni-3Fe alloy with dimensions of 10mm × 10mm × 1.5mm, the preferred configuration is: a confinement layer thickness of 500μm, a beam diameter of 2mm, a pulse width of 8ns, a wavelength of 527nm, a laser energy of 280J, and a repetition frequency of 10Hz. The resulting product has a hardness of 6.34GPa for the γ-(Ni,Fe) binder phase, a hardness of 10.55GPa for the W particles, and an ultimate tensile strength of 9.59GPa. A nanotwin structure is formed in the W particles and the γ-(Ni,Fe) binder phase.

[0084] When processing 90W-7Ni-3Fe alloy with dimensions of 5mm × 5mm × 0.5mm, the preferred configuration is: a confinement layer thickness of 200μm, a beam diameter of 1mm, a pulse width of 3ns, a wavelength of 527nm, a laser energy of 150J, and a repetition frequency of 4Hz. The resulting product exhibits a hardness of 6.89GPa for the γ-(Ni,Fe) binder phase, a hardness of 11.91GPa for the W particles, and an ultimate tensile strength of 9.79GPa. A nanotwin structure is formed in the W particles and the γ-(Ni,Fe) binder phase.

[0085] Example 2

[0086] A method for preparing an ultra-high strain rate deformation of a 93W-4.9Ni-2.1Fe alloy with a dual-phase nanotwinned structure includes the following steps:

[0087] Step 1: Surface grinding and polishing

[0088] Take a 93W-4.9Ni-2.1Fe alloy with dimensions of 10mm×10mm×0.5mm, and use a diamond fine pre-polishing disc to replace 80#, 200#, 320#, 600#, and 1200# SiC wet sandpaper to polish the surface in sequence. Use diamond polishing agents with particle sizes of 10μm, 3.5μm, and 0.5μm for mechanical polishing. The polishing disc speed is 200rpm / min, the fixed disc speed is 90rpm / min, and the air pressure column pressure is 40N.

[0089] Step 2: Surface cleaning

[0090] The polished sample was cleaned sequentially with anhydrous ethanol and deionized water using ultrasonic oscillation at a frequency of 60 kHz, a temperature of 25 °C, and a time of 5 min. The surface moisture was then dried using a nitrogen gas gun with a pressure of 0.5 MPa.

[0091] Step 3: Apply constraint layers

[0092] The cleaned sample is mounted on the worktable, and a 250μm thick optical transparent glass constraint layer is applied to the front and back sides respectively.

[0093] Step 4: Laser shock treatment

[0094] The working end face of the sample with the applied constraint layer is faced with the laser beam, and impact treatment is performed with a laser beam diameter of 2 mm, pulse width of 5 ns, wavelength of 527 nm, laser energy of 200 J, and repetition frequency of 5 Hz.

[0095] Step 5: Laser Shock Post-processing

[0096] The laser-treated samples were sequentially cleaned with anhydrous ethanol and deionized water using ultrasonic oscillation at a frequency of 40 kHz, a temperature of 25 °C, and a time of 3 min. The surface moisture was then dried using a nitrogen gas gun with a pressure of 0.3 MPa.

[0097] By utilizing the ultra-high strain rate deformation induced by laser shock, the hardness of the γ-(Ni,Fe) binder phase of the dual-phase nanotwinned alloy was increased from 4.42 GPa to 6.16 GPa, the hardness of the W particles was increased from 7.31 GPa to 12.47 GPa, and the ultimate tensile strength was increased to 10.52 GPa. The W particles and the γ-(Ni,Fe) binder phase formed a nanotwinned structure.

[0098] Example 2-1

[0099] All other conditions are the same as in Example 2, except that:

[0100] When processing 93W-4.9Ni-2.1Fe alloy with dimensions of 5mm × 5mm × 0.5mm, the preferred configuration is: a confinement layer thickness of 200μm, a beam diameter of 1mm, a pulse width of 3ns, a wavelength of 527nm, a laser energy of 170J, and a repetition frequency of 4Hz. The resulting product exhibits a hardness of 6.08GPa for the γ-(Ni,Fe) binder phase, a hardness of 12.27GPa for the W particles, and an ultimate tensile strength of 10.31GPa. A nanotwin structure is formed in the W particles and the γ-(Ni,Fe) binder phase.

[0101] Example 3

[0102] A method for preparing an ultra-high strain rate deformation of a 95W-3.5Ni-1.5Fe alloy with a dual-phase nanotwinned structure includes the following steps:

[0103] Step 1: Surface grinding and polishing

[0104] Take a 95W-3.5Ni-1.5Fe alloy with dimensions of 10mm×10mm×0.5mm, and use a diamond fine pre-polishing disc to replace 80#, 200#, 320#, 600#, and 1200# SiC wet sandpaper to polish the surface in sequence. Use diamond polishing agents with particle sizes of 10μm, 3.5μm, and 0.5μm for mechanical polishing. The polishing disc speed is 250rpm / min, the fixed disc speed is 120rpm / min, and the air pressure column pressure is 50N.

[0105] Step 2: Surface cleaning

[0106] The polished sample was cleaned sequentially with anhydrous ethanol and deionized water using ultrasonic oscillation at a frequency of 60 kHz, a temperature of 25 °C, and a time of 5 min. The surface moisture was then dried using a nitrogen gas gun with a pressure of 0.5 MPa.

[0107] Step 3: Apply constraint layers

[0108] The cleaned sample is mounted on the worktable, and a 250μm thick optical transparent glass constraint layer is applied to the front and back sides respectively.

[0109] Step 4: Laser shock treatment

[0110] The working end face of the sample with the applied constraint layer is faced with the laser beam, and it is subjected to impact treatment with a laser beam diameter of 2 mm, pulse width of 4 ns, wavelength of 527 nm, laser energy of 220 J, and repetition frequency of 6 Hz.

[0111] Step 5: Laser Shock Post-processing

[0112] The laser-treated samples were sequentially cleaned with anhydrous ethanol and deionized water using ultrasonic oscillation at a frequency of 40 kHz, a temperature of 25 °C, and a time of 3 min. The surface moisture was then dried using a nitrogen gas gun with a pressure of 0.3 MPa.

[0113] By utilizing the ultra-high strain rate deformation induced by laser shock, the hardness of the γ-(Ni,Fe) binder phase of the dual-phase nanotwinned 95W-3.5Ni-1.5Fe alloy was increased from 4.31 GPa to 5.98 GPa, the hardness of the W particles was increased from 7.87 GPa to 13.52 GPa, and the ultimate tensile strength was 10.98 GPa. The W particles and the γ-(Ni,Fe) binder phase form a nanotwinned structure.

[0114] Example 3-1

[0115] When processing 95W-3.5Ni-1.5Fe alloy with dimensions of 5mm × 5mm × 0.5mm, the preferred configuration is: a confinement layer thickness of 200μm, a beam diameter of 1mm, a pulse width of 3ns, a wavelength of 527nm, a laser energy of 190J, and a repetition frequency of 5Hz. The resulting product exhibits a hardness of 5.91GPa for the γ-(Ni,Fe) binder phase, a hardness of 13.26GPa for the W particles, and an ultimate tensile strength of 10.82GPa. A nanotwin structure is formed in the W particles and the γ-(Ni,Fe) binder phase.

[0116] Comparative Example 1

[0117] All other conditions are the same as in Example 1, except that the pulse width set during laser shock is different: the pulse width is selected as 8ns;

[0118] The 90W-7Ni-3Fe alloy obtained using Comparative Example 1 has a hardness of 5.41 GPa for the γ-(Ni,Fe) binder phase, a hardness of 8.42 GPa for the W particles, and an ultimate tensile strength of 7.11 GPa. No nanotwin structure was formed in the W particles and the γ-(Ni,Fe) binder phase, but dislocation groups appeared, mainly a large number of edge dislocation entanglements.

[0119] The inventors noted that an excessively large pulse width disperses laser energy over a longer time region, leading to uneven heating and blurred impact areas, while also increasing energy loss. This results in the inability to achieve precise ultra-high strain rate deformation, leading to a nanotwinned structure and instead the formation of numerous dislocation tangles.

[0120] Comparative Example 2

[0121] All other conditions are the same as in Example 1, except that the laser energy used for laser shock is different: the laser energy is 200J.

[0122] The 90W-7Ni-3Fe alloy obtained using Comparative Example 2 exhibited a hardness of 5.98 GPa for the γ-(Ni,Fe) binder phase, 9.09 GPa for the W particles, and a tensile strength of 7.74 GPa. No nanotwin structures were formed in the W particles and the γ-(Ni,Fe) binder phase; instead, numerous recrystallized grains were observed. Furthermore, the front side of the sample showed a distinct laser ablation surface and microcrack initiation, while the back side showed a tendency towards delamination.

[0123] The inventors noted that due to the strain rate sensitivity of the 90W-7Ni-3Fe alloy, excessively high laser energy during laser shock will cause excessive and severe deformation and stress concentration inside the material, leading to the initiation of surface cracks and the tendency of back-side delamination. High-energy lasers also cause changes in crystal structure and excessive deformation in local areas, making it impossible to form a stable nanotwin structure.

[0124] Comparative Example 3

[0125] All other conditions were the same as in Example 1, except that no constraint layer was applied when laser-shocked the 90W-7Ni-3Fe alloy;

[0126] The 90W-7Ni-3Fe alloy obtained in Comparative Example 3 had a hardness of 5.87 GPa for the γ-(Ni,Fe) binder phase, a hardness of 9.41 GPa for the W particles, and an ultimate tensile strength of 6.56 GPa. The front side exhibited a very obvious laser ablation surface, along with numerous microcracks and even delamination. On the back side of the sample, delamination occurred, and the laser directly penetrated the sample.

[0127] The inventors noted that, without the protection of a restraint layer and without a front-side restraint layer to limit the propagation range of the shock wave, the laser shock wave can act directly and unevenly on the surface. This uneven local stress distribution leads to surface cracks and even delamination. Without the reaction force support of a back-side restraint layer, the propagation of the laser shock wave within the material results in significant stress accumulation, leading to delamination and ultimately, sample breakdown.

[0128] Comparative Example 4

[0129] All other conditions are the same as in Example 1, except that the wavelength set during the laser shock process is different: the wavelength is 1064nm.

[0130] The 90W-7Ni-3Fe alloy obtained using Comparative Example 4 exhibits a hardness of 5.01 GPa for the γ-(Ni,Fe) binder phase, 8.35 GPa for the W particles, and a tensile strength of 6.27 GPa. A small number of nanotwins are observed in the W particles and the γ-(Ni,Fe) binder phase, but dislocation entanglement is the dominant feature.

[0131] The inventors noted that the absorption of laser by the 90W-7Ni-3Fe alloy is closely related to the laser wavelength. If the wavelength is too large, the absorption of laser by the 90W-7Ni-3Fe alloy will be reduced, making it difficult to achieve a sufficient heating effect. Consequently, the laser energy will not be able to be uniformly transferred to the deep layers, resulting in the strain rate not reaching the expected level and the inability to form a stable biphase nanotwin structure.

[0132] Comparative Example 5

[0133] All other conditions are the same as in Example 1, except that the repetition frequency set during laser shock is different: the repetition frequency is set to 0.5 Hz.

[0134] The 90W-7Ni-3Fe alloy obtained using Comparative Example 5 had a hardness of 4.95 GPa for the γ-(Ni,Fe) binder phase, a hardness of 7.79 GPa for the W particles, and an ultimate tensile strength of 3.38 GPa. No nanotwins were observed in the W particles and the γ-(Ni,Fe) binder phase; only a large number of dislocations were present, and the dislocation entanglement phenomenon was significantly reduced.

[0135] The inventors noted that during laser shock strengthening, a low laser repetition frequency leads to reduced heating efficiency and uneven heating, preventing the metal surface from reaching a sufficient temperature. At the same time, the processing time is slowed down, resulting in a shorter loading time, which fails to achieve the expected ultra-high strain rate and thus the desired deformation effect.

[0136] Comparative Example 6

[0137] All other conditions are the same as in Example 1, except that pure W is used;

[0138] The pure W sample obtained using Comparative Example 6 showed a large number of micropores and microcracks inside, with only a small number of light and dark striped twins with a width of 20-100 nm and a length of up to several hundred micrometers.

[0139] The inventors noted differences between pure W and tungsten alloys in laser-shock-induced nanotwin structures. These differences primarily stem from variations in material composition, melting point density, and crystal growth kinetics, which can lead to variations in the size, morphology, and crystal defects of the resulting nanotwin structures. Detailed differences depend on the specific material composition and preparation conditions.

Claims

1. A method for super-high strain rate deformation preparation of tungsten alloy with dual-phase nano-twin structure, characterized in that, Comprise the following steps: (1) tungsten alloy sheet surface pretreatment: before laser shock processing, the surface of the tungsten alloy sheet sample with a thickness of 50-2000 μm is pretreated; get the surface clean and dry tungsten alloy sheet; the material of the tungsten alloy sheet comprises the following components by mass percent: Ni 7%, Fe 3%; the balance is W and inevitable impurities, accounting for 90W-7Ni-3Fe alloy; or, Ni 4.9%, Fe 2.1%; the balance is W and inevitable impurities, accounting for 93W-4.9Ni-2.1Fe alloy; or, Ni 3.5%, Fe 1.5%; the balance is W and inevitable impurities, accounting for 95W-3.5Ni-1.5Fe alloy; (2) apply a constraint layer: install the surface clean and dry tungsten alloy sheet on the workbench, apply a layer of optical transparent glass constraint layer with a thickness of 50-1000 μm on the front and back respectively, and the thickness of single layer optical transparent glass constraint layer is 1 / 3-3 / 5 of the thickness of tungsten alloy sheet; (3) laser shock processing: the working end surface of the tungsten alloy sample with constraint layer is directed towards the laser beam, with a beam diameter of 1-5 mm, a pulse width of 1-10 ns, a wavelength of 300-800 nm, a laser energy of 100-300 J, and a repetition frequency of 0.1-10 Hz; When the sample is 10mm×10mm×0.1mm of 90W-7Ni-3Fe alloy, the beam diameter is 2mm, the pulse width is 2ns, the wavelength is 527nm, the laser energy is 120J, and the repetition frequency is 0.5Hz; When the sample is 10mm×10mm×0.5mm of 90W-7Ni-3Fe alloy, the beam diameter is 2mm, the pulse width is 5ns, the wavelength is 527nm, the laser energy is 180J, and the repetition frequency is 5Hz; When the sample is 10mm×10mm×1.5mm of 90W-7Ni-3Fe alloy, the beam diameter is 2mm, the pulse width is 8ns, the wavelength is 527nm, the laser energy is 280J, and the repetition frequency is 10Hz; When the sample is 5mm×5mm×0.5mm of 90W-7Ni-3Fe alloy, the beam diameter is 1mm, the pulse width is 3ns, the wavelength is 527nm, the laser energy is 150J, and the repetition frequency is 4Hz; When the sample is 10mm×10mm×0.5mm of 93W-4.9Ni-2.1Fe alloy, the beam diameter is 2mm, the pulse width is 5ns, the wavelength is 527nm, the laser energy is 200J, and the repetition frequency is 5Hz; When the sample is 5mm×5mm×0.5mm of 93W-4.9Ni-2.1Fe alloy, the beam diameter is 1mm, the pulse width is 3ns, the wavelength is 527nm, the laser energy is 170J, and the repetition frequency is 4Hz; When the sample is 10mm×10mm×0.5mm of 95W-3.5Ni-1.5Fe alloy, the beam diameter is 2mm, the pulse width is 4ns, the wavelength is 527nm, the laser energy is 220J, and the repetition frequency is 6Hz; When the sample is 95W-3.5Ni-1.5Fe alloy with a size of 5mm×5mm×0.5mm, the diameter of the light beam is 1mm, the pulse width is 3ns, the wavelength is 527nm, the laser energy is 190J, and the repetition frequency is 5Hz; (4) Laser shock post-processing: After laser shock processing, the sample is cleaned, dried with nitrogen, and the product is obtained. The product has a dual-phase nanotwin structure.

2. The method of claim 1, wherein the method comprises: The surface of the tungsten alloy sheet is pretreated by using a diamond fine pre-polishing disc to replace 80-1200# SiC water abrasive paper for all pre-polishing steps, and a diamond polishing agent with a particle size of 0.5-10μm is used for polishing. The polishing disc rotates at a speed of 100-500rpm / min, the fixed disc rotates at a speed of 30-150rpm / min, and the air pressure column pressure is 10-70N. After surface polishing, the sample is cleaned and dried with nitrogen.

3. The method of claim 1, wherein the method comprises: providing a tungsten alloy having a dual-phase nanotwinned structure; and subjecting the tungsten alloy to ultra-high strain rate deformation. The surface is polished by using a diamond fine pre-polishing disc to replace 80#, 120#, 240#, 600#, and 1200# SiC water abrasive paper in sequence, and a 10μm, 3.5μm, and 0.5μm particle size diamond polishing agent is used for mechanical polishing. When the sample is 90W-7Ni-3Fe alloy, the polishing disc rotates at a speed of 150pm / min, the fixed disc rotates at a speed of 60rpm / min, and the air pressure column pressure is 30N. When the sample is 93W-4.9Ni-2.1Fe alloy, the polishing disc rotates at a speed of 200rpm / min, the fixed disc rotates at a speed of 90rpm / min, and the air pressure column pressure is 40N. When the sample is 95W-3.5Ni-1.5Fe alloy, the polishing disc rotates at a speed of 250rpm / min, the fixed disc rotates at a speed of 120rpm / min, and the air pressure column pressure is 50N. After the tungsten alloy material surface is polished, it is cleaned in anhydrous ethanol and deionized water ultrasonic oscillation, the ultrasonic frequency is 30-80KHz, the temperature is 20-25℃, the time is 3-10min, and finally it is dried with nitrogen. When the nitrogen is blown dry, the nitrogen air gun pressure is 0.3-1.0MPa.

4. The method of claim 1, wherein the method comprises: providing a tungsten alloy having a dual-phase nanotwinned structure; and subjecting the tungsten alloy to ultra-high strain rate deformation. In step (3), the thickness of the optical transparent glass constraint layer is 1 / 3-1 / 2 of the thickness of the tungsten alloy sheet.

5. The method according to claim 4, wherein: When the sample is 10mm×10mm×0.1mm 90W-7Ni-3Fe alloy, the thickness of the optical transparent glass constraint layer is 50μm; When the sample is 10mm×10mm×0.5mm 90W-7Ni-3Fe alloy, the thickness of the optical transparent glass constraint layer is 250μm; When the sample is 10mm×10mm×1.5mm 90W-7Ni-3Fe alloy, the thickness of the optical transparent glass constraint layer is 500μm; When the sample is 5mm×5mm×0.5mm 90W-7Ni-3Fe alloy, the thickness of the optical transparent glass constraint layer is 200μm; When the processing sample is 93W-4.9Ni-2.1Fe alloy with a size of 10mm×10mm×0.5mm, the thickness of the optical transparent glass confinement layer is 250μm; When the processing sample is 93W-4.9Ni-2.1Fe alloy with a size of 5mm×5mm×0.5mm, the thickness of the optical transparent glass confinement layer is 200μm; When the processing sample is 95W-3.5Ni-1.5Fe alloy with a size of 10mm×10mm×0.5mm, the thickness of the optical transparent glass confinement layer is 250μm; When the processing sample is 95W-3.5Ni-1.5Fe alloy with a size of 5mm×5mm×0.5mm, the thickness of the optical transparent glass confinement layer is 200μm.

6. The method of claim 1, wherein the tungsten alloy has a dual-phase nanotwinned structure. In the step (4), the ultrasonic frequency is 30-50 KHz, the temperature is 20-25℃, the time is 3-5 min, and the nitrogen gas gun pressure is 0.1-0.5 MPa.

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