A method of composite strengthening to improve strength and ductility of metal alloys

Abstract

The application belongs to the technical field of mechanical property strengthening of metal materials, and particularly relates to a composite strengthening method for improving the strength and plasticity of metal alloys. The method comprises the following steps: (1) performing surface pretreatment on a metal alloy sample; (2) performing ion implantation processing on the pretreated metal alloy sample; (3) coating a layer of nanoparticles on the surface of the metal alloy sample after ion implantation processing; (4) performing cryogenic treatment on the metal alloy sample with the surface coated with the nanoparticles; (5) performing electric pulse treatment on the metal alloy sample after the cryogenic treatment; and (6) performing cryogenic holding treatment on the metal alloy sample after the electric pulse treatment. The application can effectively improve the strength and plasticity of the metal alloy.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mechanical properties of metal materials, and particularly relates to a composite strengthening method for improving the strength and plasticity of metal alloys. BACKGROUND

[0002] High-strength, multifunctional lightweight alloys can meet the design requirements of lightweight and structure / function integration, and are irreplaceable key basic materials in the fields of high-end equipment manufacturing such as aerospace, shipbuilding and ocean engineering. However, the service environment of lightweight alloy key components is harsh, and fatigue failure is easily realized under long-term external cyclic load. How to effectively inhibit the fatigue and failure of lightweight alloy components has become a key problem to be solved in the field of high-end equipment manufacturing.

[0003] Ion implantation is a strengthening technology that ionizes one or more elements, accelerates them to form an acceleration electric field, and finally shoots them into the target material at high speed. Ion implantation can effectively improve the surface mechanical properties of materials by introducing residual compressive stress and restructuring defect structure in the surface layer of lightweight alloys, and is an effective means to improve the service life of metal materials. However, the strengthening layer induced by ion implantation strengthening technology is shallow, which limits the wide application of ion implantation technology.

[0004] Deep cryogenic temperature can induce internal stress and deformation energy in metal materials by volume shrinkage effect. Internal stress promotes the generation and proliferation of dislocations, and the aggregation and migration of dislocations help to promote grain refinement. However, the residual compressive stress induced by deep cryogenic treatment has small amplitude, and has little effect on the improvement of the mechanical properties such as strength, plasticity and fatigue resistance of metal materials.

[0005] Compared with temperature field, the transient high-energy field induced by electric pulse using thermal-electric-force coupling effect can induce microstructure different from normal state in metal materials, and has significant advantages in regulating the mechanical properties of metal materials. However, electric pulse can significantly improve the plasticity of materials by regulating the microstructure of materials, but the strength gain effect is not outstanding.

[0006] Therefore, how to develop a new type of composite strengthening method that can simultaneously improve the strength and plasticity of metal materials, and induce a residual compressive stress layer with large amplitude and strong stability, thereby improving the comprehensive mechanical properties of metal materials, is one of the technical problems to be solved in the mechanical field. SUMMARY

[0007] In view of the deficiencies in the prior art, the present application provides a composite strengthening method for improving the strength and plasticity of metal alloys.

[0008] The technical scheme of the present application is as follows:

[0009] A composite strengthening method for improving the strength and plasticity of metal alloys, comprising the following steps:

[0010] Step one: polish the surface of the metal alloy sample to remove the surface oxide layer, then polish, then place in acetone solution for ultrasonic cleaning, and finally put into a vacuum drying oven for standby;

[0011] Step two: ion implantation strengthening treatment of the metal alloy sample pretreated in step one;

[0012] Step three: coating the surface of the metal alloy sample after ion implantation strengthening treatment in step two with nano-particles by spraying method;

[0013] Step four: deep cryogenic treatment of the metal alloy sample after step three treatment;

[0014] Step five: electric pulse treatment of the metal alloy sample after deep cryogenic treatment in step four at deep cryogenic temperature;

[0015] Step six: continue to heat the metal alloy sample after step five treatment at deep cryogenic temperature for 30-60 min, then take out, rise to room temperature, and the heating rate is 20-50℃ / min.

[0016] As preferred, the metal alloy is any one of titanium alloy, aluminum alloy, nickel-based alloy or magnesium alloy; the thickness of the metal alloy sample is 0.5-20mm.

[0017] As preferred, the process parameters of ion implantation in step two are: the ion implantation element is any one of metal ion or non-metal ion, the ion implantation temperature is room temperature, the acceleration voltage is 45kV, the beam current is 0.01-0.5mA, the implantation time is 0.5-10h, and the implantation dose is 0.75×10 17 -2.5×10 18 ions / cm 2 ; wherein the metal ion is any one of Ti, Al or Ni, and the non-metal ion is any one of N, Ar or He.

[0018] As preferred, the nano-particles in step three are any one of pure aluminum, black tape or black paint nano-particles, and the size of the nano-particles is 50-200nm; the thickness of the nano-particle coating is 50-100μm.

[0019] As preferred, the deep cryogenic treatment temperature range in step four is -196--150℃, and the holding time of deep cryogenic treatment is 2-10h. The purpose of deep cryogenic treatment is to use the internal stress generated by the volume shrinkage effect at deep cryogenic temperature to cause dislocation proliferation and grain refinement defects of the whole sample, and to improve the diffusion range of implanted ions.

[0020] As preferred, the process parameters of the electric pulse treatment in step five are: voltage of 50-150V, frequency of 50-1000Hz, pulse width of 10-100us, and electric pulse treatment time of 30-180min. The electroplastic effect of the electric pulse can improve the plasticity of the metal alloy; meanwhile, the continuous effect of the electric pulse generates heat on the surface of the metal sample, the generated heat makes the liquid nitrogen rapidly gasify and expand to form bubbles, and the instantaneous high-energy and high-pressure generated by the breaking of the bubbles makes the nanoparticles coated on the surface of the sample absorb energy to form a high-temperature and high-pressure plasma shock wave, which acts on the surface layer of the sample, the constraint effect of the liquid nitrogen on the plasma shock wave improves the peak pressure of the shock wave and prolongs the action time, so that the surface layer of the material is subjected to severe plastic deformation to generate high-density defects and high-amplitude residual compressive stress. In addition, the diffusion speed of the implanted ions is accelerated by using the plasma shock wave to act on the surface of the sample, thereby further improving the penetration ability of the implanted ions. Finally, in the process of electric pulse strengthening treatment of the sample, the dynamic recovery of micro defects is inhibited by using the cryogenic temperature of liquid nitrogen, thereby improving the strengthening performance and stability of the sample.

[0021] The beneficial effects are:

[0022] The present application comprehensively utilizes the advantages of ion implantation, cryogenic treatment and point pulse treatment, and proposes a composite strengthening method for improving the strength and plasticity of metal alloys, wherein the ion implantation generates compressive stress on the surface of the metal alloy; the cryogenic treatment causes defects such as dislocation multiplication and grain refinement of the metal alloy, thereby improving the diffusion range of the implanted ions; the electric pulse treatment improves the plasticity of the metal alloy, so that the surface layer of the material is subjected to severe plastic deformation to generate high-density defects and high-amplitude residual compressive stress, and the penetration ability of the implanted ions is improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The process flow chart of the method is shown in the figure. DETAILED DESCRIPTION

[0024] Example 1

[0025] A composite strengthening method for improving the strength and plasticity of metal alloys, as shown in Figure 1 , comprising the following steps:

[0026] (1) The surface of a TC4 titanium alloy plate sample with a thickness of 3mm is polished to remove the oxide layer on the surface, then is subjected to polishing treatment, and then is placed in an acetone solution for ultrasonic cleaning for 15min, and finally is stored in a vacuum drying box for standby.

[0027] (2) The pretreated TC4 titanium alloy plate sample was subjected to ion implantation strengthening treatment. The ion implantation element was nitrogen ions, the ion implantation temperature was room temperature, the accelerating voltage was 45 kV, the beam current was 0.25 mA, the implantation time was 8 h, and the implantation dose was 1.2 × 10⁻⁶. 18 ions / cm 2 .

[0028] (3) A layer of pure aluminum nanoparticles was coated on the surface of the TC4 titanium alloy plate sample after ion implantation strengthening treatment by spraying. The coating thickness of the nanoparticles was 50 μm and the size of the nanoparticles was 100 nm.

[0029] (4) The TC4 titanium alloy plate sample coated with pure aluminum nanoparticles was subjected to cryogenic treatment. The temperature range of the cryogenic treatment was -196℃ and the holding time of the cryogenic treatment was 5h.

[0030] (5) The TC4 titanium alloy plate sample after cryogenic treatment is subjected to electrical pulse treatment at cryogenic temperature. The process parameters of the electrical pulse treatment are: voltage of 100V, frequency of 500Hz, pulse width of 50μs, and electrical pulse treatment time of 120min.

[0031] (6) After the TC4 titanium alloy plate sample was treated with electrical pulse, it was kept at a deep cryogenic temperature for 60 min, and then the sample was taken out and allowed to rise to room temperature at a rate of 25℃ / min.

[0032] The tensile properties of TC4 titanium alloy sheet specimens were tested using an AGS precision universal testing machine at a test speed of 50 mm / min and at room temperature, as shown in Table 1. Compared with the untreated specimens, the tensile strength of the specimens treated according to this invention increased by 18.8%, and the elongation increased by 11.6%.

[0033] Table 1 Comparison of tensile properties of specimens with different treatments

[0034]

[0035] Example 2

[0036] A composite strengthening method for improving the strength and plasticity of metal alloys includes the following steps:

[0037] (1) The surface of a 2mm thick 7075 aluminum alloy plate sample was ground to remove the oxide layer, then polished, and then placed in an acetone solution for ultrasonic cleaning for 30 minutes. Finally, it was stored in a vacuum drying oven for later use.

[0038] (2) The pretreated 7075 aluminum alloy sheet sample was subjected to ion implantation strengthening treatment. The ion implantation element was Ti ions, the ion implantation temperature was room temperature, the accelerating voltage was 45 kV, the beam current was 0.5 mA, the implantation time was 5 h, and the implantation dose was 7.5 × 10⁻⁶. 17 ions / cm 2 .

[0039] (3) A layer of black paint nanoparticles was coated on the surface of the 7075 aluminum alloy plate sample after ion implantation strengthening treatment by spraying. The coating thickness of the nanoparticles was 75 μm and the size of the nanoparticles was 100 nm.

[0040] (4) The 7075 aluminum alloy plate sample coated with black paint nanoparticles was subjected to cryogenic treatment. The temperature range of the cryogenic treatment was -150℃ and the holding time of the cryogenic treatment was 5h.

[0041] (5) The 7075 aluminum alloy plate sample after cryogenic treatment is subjected to electrical pulse treatment at cryogenic temperature. The process parameters of the electrical pulse treatment are: voltage of 150V, frequency of 1000Hz, pulse width of 75μs, and electrical pulse treatment time of 120min.

[0042] (6) After the 7075 aluminum alloy plate sample was treated with electrical pulse, it was kept at a deep cryogenic temperature for 45 minutes, and then the sample was taken out and allowed to rise to room temperature at a rate of 50℃ / min.

[0043] The tensile properties of 7075 aluminum alloy sheet specimens were tested using an AGS precision universal testing machine at a test speed of 100 mm / min and at room temperature, as shown in Table 2. Compared with the untreated specimens, the tensile strength of the specimens treated according to this invention increased by 15.2%, and the elongation increased by 9.9%.

[0044] Table 2 Comparison of tensile properties of specimens with different treatments

[0045]

[0046] Example 3

[0047] A composite strengthening method for improving the strength and plasticity of metal alloys includes the following steps:

[0048] (1) The surface of the AZ31 magnesium alloy plate sample with a thickness of 2.5mm was ground to remove the oxide layer, then polished, and then placed in acetone solution for ultrasonic cleaning for 30 minutes. Finally, it was stored in a vacuum drying oven for later use.

[0049] (2) The pretreated AZ31 magnesium alloy plate sample was subjected to ion implantation strengthening treatment. The ion implantation element was Ti ions, the ion implantation temperature was room temperature, the accelerating voltage was 45 kV, the beam current was 0.01 mA, the implantation time was 10 h, and the implantation dose was 1.5 × 10⁻⁶. 18 ions / cm 2 .

[0050] (3) A layer of black tape nanoparticles was coated on the surface of the AZ31 magnesium alloy plate sample after ion implantation strengthening treatment by spraying. The coating thickness of the nanoparticles was 50 μm and the size of the nanoparticles was 50 nm.

[0051] (4) The AZ31 magnesium alloy plate sample coated with black tape nanoparticles was subjected to cryogenic treatment. The temperature range of the cryogenic treatment was -196℃ and the holding time of the cryogenic treatment was 2h.

[0052] (5) The AZ31 magnesium alloy plate sample after cryogenic treatment is subjected to electrical pulse treatment at cryogenic temperature. The process parameters of the electrical pulse treatment are: voltage of 50V, frequency of 50Hz, pulse width of 10μs, and electrical pulse treatment time of 30min.

[0053] (6) After the AZ31 magnesium alloy plate sample was treated with electrical pulse, it was kept at a deep cryogenic temperature for 30 min, and then the sample was taken out and allowed to rise to room temperature at a rate of 30℃ / min.

[0054] The tensile properties of 7075 aluminum alloy sheet specimens were tested using an AGS precision universal testing machine at a test speed of 150 mm / min and at room temperature, as shown in Table 3. Compared with the untreated specimens, the tensile strength of the specimens treated according to this invention increased by 21.5%, and the elongation increased by 12%.

[0055] Table 3 Comparison of tensile properties of specimens with different treatments

[0056]

[0057] Comparative Example 1

[0058] Taking a 3mm thick TC4 titanium alloy plate as an example, single ion implantation, cryogenic treatment, and electrical pulse treatment were performed respectively. Among them: (1) The element for ion implantation was nitrogen ions, the ion implantation temperature was room temperature, the accelerating voltage was 45kV, the beam current was 0.25mA, the implantation time was 8h, and the implantation dose was 1.2×10 18 ions / cm 2(2) The temperature of cryogenic treatment is -196℃ and the holding time of cryogenic treatment is 5h; (3) The process parameters of electric pulse treatment are: voltage is 100V, frequency is 500Hz, pulse width is 50μs, and electric pulse treatment time is 120min.

[0059] The tensile properties of TC4 titanium alloy sheet specimens with different treatments were tested using an AGS precision universal testing machine at a test speed of 50 mm / min and at room temperature. The results are shown in Table 4. The results indicate that, compared with a single strengthening treatment, the embodiment of this invention provides a superior strength-plasticity strengthening effect to the metal alloy.

[0060] Table 4 Comparison of tensile properties of specimens with different treatments

[0061]

[0062] Comparative Example 2

[0063] (1) Taking a TC4 titanium alloy plate with a thickness of 3mm as an example, the surface of the TC4 titanium alloy plate sample is ground to remove the oxide layer, then polished, and then placed in an acetone solution for ultrasonic cleaning for 15 minutes. Finally, it is stored in a vacuum drying oven for later use.

[0064] (2) A layer of pure aluminum nanoparticles was coated on the surface of the TC4 titanium alloy plate sample after surface pretreatment by spraying. The coating thickness of the nanoparticles was 50 μm and the size of the nanoparticles was 100 nm.

[0065] (3) The TC4 titanium alloy plate sample coated with pure aluminum nanoparticles was subjected to cryogenic treatment. The temperature range of the cryogenic treatment was -196℃ and the holding time of the cryogenic treatment was 5h.

[0066] (4) The TC4 titanium alloy plate sample after cryogenic treatment is subjected to electrical pulse treatment at cryogenic temperature. The process parameters of the electrical pulse treatment are: voltage of 100V, frequency of 500Hz, pulse width of 50μs, and electrical pulse treatment time of 120min.

[0067] (5) After the TC4 titanium alloy plate sample was treated with electrical pulse, it was kept at a deep cryogenic temperature for 60 min, and then the sample was taken out and allowed to rise to room temperature at a rate of 25℃ / min.

[0068] (6) The cryogenically treated TC4 titanium alloy plate sample was subjected to ion implantation strengthening treatment. The ion implantation element was nitrogen ions, the ion implantation temperature was room temperature, the accelerating voltage was 45 kV, the beam current was 0.25 mA, the implantation time was 8 h, and the implantation dose was 1.2 × 10⁻⁶. 18 ions / cm 2 .

[0069] The tensile properties of TC4 titanium alloy sheet specimens were tested using an AGS precision universal testing machine at a test speed of 50 mm / min and at room temperature, as shown in Table 5. Compared with specimens treated by cryogenic treatment + electrical pulse treatment + ion implantation, the tensile strength of the specimens treated by this invention increased by 2%, and the elongation increased by 3.3%.

[0070] Table 5 Comparison of tensile properties of specimens with different treatments

[0071]

[0072] The embodiments described above are preferred implementations of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A composite strengthening method for improving the strength and plasticity of metal alloys, characterized in that, Includes the following steps: Step 1: Grind and polish the surface of the metal alloy sample, then place it in an acetone solution for ultrasonic cleaning, and finally put it in a vacuum drying oven for later use. Step 2: Perform ion implantation strengthening treatment on the metal alloy sample after the pretreatment in Step 1. Step 3: Apply nanoparticles to the surface of the metal alloy sample after ion implantation strengthening treatment in Step 2 using a spraying method; Step 4: Perform deep cryogenic treatment on the metal alloy sample after Step 3. Step 5: Perform electrical pulse treatment on the metal alloy sample after the cryogenic treatment in Step 4 at a cryogenic temperature; Step 6: Continue to hold the metal alloy sample treated in Step 5 at a cryogenic temperature for 30-60 minutes, then remove it and raise it to room temperature at a rate of 20-50℃ / min.

2. The composite strengthening method for improving the strength and plasticity of metal alloys according to claim 1, characterized in that, The metal alloy sample is made of any one of titanium alloy, aluminum alloy, nickel-based alloy or magnesium alloy; the thickness of the metal alloy sample is 0.5 to 20 mm.

3. The composite strengthening method for improving the strength and plasticity of metal alloys according to claim 1, characterized in that, The process parameters for ion implantation in step two are as follows: the ion implantation element is any one of metal ions or non-metal ions; the ion implantation temperature is room temperature; the accelerating voltage is 45 kV; the beam current is 0.01–0.5 mA; the implantation time is 0.5–10 h; and the implantation dose is 0.75 × 10⁻⁶. 17 ~2.5×10 18 ions / cm 2 Wherein, the metal ion is any one of Ti, Al or Ni, and the non-metal ion is any one of N, Ar or He.

4. The composite strengthening method for improving the strength and plasticity of metal alloys according to claim 1, characterized in that, The nanoparticles in step three are pure aluminum, and the size of the nanoparticles is 50-200 nm; the thickness of the coating on the nanoparticles is 50-100 μm.

5. The composite strengthening method for improving the strength and plasticity of metal alloys according to claim 1, characterized in that, The cryogenic treatment temperature range in step four is -196 to -150°C, and the cryogenic treatment holding time is 2 to 10 hours.

6. The composite strengthening method for improving the strength and plasticity of metal alloys according to claim 1, characterized in that, The process parameters for the electrical pulse treatment in step five are: voltage of 50-150V, frequency of 50-1000Hz, pulse width of 10-100μs, and electrical pulse treatment time of 30-180min.

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