A method of powder metallurgical production of Ti-Zr-O alloys

Abstract

The application provides a method for preparing Ti-Zr-O alloy by powder metallurgy and belongs to the technical field of metal material processing. The method comprises the following steps: Ti powder, Zr powder and TiO2 powder are respectively weighed according to mass ratios, and the three kinds of powders are uniformly mixed to obtain mixed powder; then the mixed powder is subjected to cold isostatic pressing and vacuum sintering treatment to obtain a sintered blank; then the sintered blank is subjected to hot extrusion, hot rolling and homogenization annealing treatment in sequence to obtain an annealed blank; finally, the annealed blank is subjected to ultrasonic rolling treatment to obtain the high-strength and high-ductility Ti-Zr-O alloy prepared by powder metallurgy. The application can realize the effect of improving the strength of the Ti-Zr-O alloy prepared by powder metallurgy without sacrificing the plasticity of the material, and has the advantages of low preparation cost, simple process, convenient operation and wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal material processing, and particularly relates to a method for preparing a high-strength and high-ductility Ti-Zr-O alloy by powder metallurgy. BACKGROUND

[0002] Titanium and titanium alloy have good biocompatibility, non-toxicity, non-magneticity and other advantages, and are used as the third generation of biomedical implant materials. Compared with medical stainless steel and cobalt-chromium alloy, pure titanium has a density and elastic modulus closer to human bone, but the corrosion resistance and wear resistance of pure titanium are poor. Alloying can improve the comprehensive performance of pure titanium. At present, the main biomedical titanium alloy is Ti-6Al-4V. The addition of Al and V in Ti-6Al-4V improves the fatigue strength, wear resistance and corrosion resistance of the alloy. However, it is reported in some literatures that Al can cause bone resorption, anemia and nerve disorders, and V can affect metabolism. Therefore, Ti-Zr alloy with better biocompatibility is expected to replace pure titanium or Ti-6Al-4V to become a new implant material.

[0003] The production process of Ti-Zr alloy mainly includes traditional melting method and powder metallurgy method. The traditional melting method has complex process, high energy consumption and problems such as composition segregation and coarse grains in castings, and it is difficult to produce high-quality materials. The powder metallurgy method has the advantages of short process flow, controllable powder particle size and low cost, avoids some problems in the melting process, and reduces the cost of the production process, and is the most potential Ti-Zr alloy preparation process at present.

[0004] There are some deficiencies in the current powder metallurgy preparation of Ti-Zr alloy. First, the powder morphology determines the flowability, fillability, compressibility and formability of the powder. In the current powder metallurgy process for preparing Ti-Zr alloy, irregular powder is mostly used, and the flowability and fillability of irregular powder are poor, resulting in more holes in the formed blank, and the strength is also reduced. Secondly, in the Ti-Zr alloy matrix, too low oxygen content will result in insufficient strength and hardness of the alloy, which cannot meet the requirements of high-strength application. Too high oxygen content will reduce the plasticity and toughness of Ti-Zr alloy, and increase the risk of brittle fracture. Therefore, reasonable control of oxygen content is a key factor to improve the mechanical properties of Ti-Zr alloy. Finally, the lack of appropriate heat treatment system and surface strengthening method is also a bottleneck restricting the synergistic improvement of the strength and plasticity of the powder metallurgy prepared Ti-Zr alloy. In short, the organization and mechanical properties of the powder metallurgy prepared Ti-Zr alloy are affected by the powder morphology, oxygen content and distribution, heat treatment system and surface strengthening, and need to be optimized and controlled. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application aims to provide a method for preparing high-strength and high-ductility Ti-Zr-O alloy by powder metallurgy, which can increase the tensile strength of Ti-Zr-O alloy to more than 1200 MPa under the premise of ensuring good plasticity of the material, and has simple component ratio, fine and uniform structure and simple production process.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A method for preparing high-strength and high-ductility Ti-Zr-O alloy by powder metallurgy, comprising the following steps:

[0008] (1) Preparing powder: Ti powder, Zr powder and TiO2 powder are weighed according to the mass ratio of Ti:Zr:TiO2=84.1-84.3:15:0.7-0.9, and the three kinds of powder are mixed uniformly to obtain mixed powder;

[0009] (2) Forming and sintering: the mixed powder is cold isostatic pressed and then vacuum sintered to obtain sintered blank;

[0010] (3) Alloy strengthening: the sintered blank is sequentially subjected to hot extrusion, hot rolling, homogenization annealing and ultrasonic rolling to obtain high-strength and high-ductility Ti-Zr-O alloy prepared by powder metallurgy.

[0011] Further, the powder mixing device is a vacuum ball mill tank, the ball-to-powder ratio is 1-5:1, the planetary ball mill speed is 50-400 rpm, and the ball milling time is 1-5 h.

[0012] Further, the Ti powder is spherical with a particle size of 5-45 µm, and the composition of the Ti powder is C≤0.03%, O≤0.15%, N≤0.03%, H≤0.01%, Fe≤0.05%, and the rest is Ti and trace impurities; the Zr powder is spherical with a particle size of 5-45 µm, and the composition of the Zr powder is C≤0.03%, O≤0.03%, N≤0.04%, H≤0.01%, and the rest is Zr and trace impurities; the TiO2 powder is lamellar nanoscale powder with a particle size of 5-10 nm, and the oxygen content in the TiO2 powder is 35%-45%.

[0013] Further, the cold isostatic pressing parameters are: forming pressure 200-300 MPa, and pressure holding time 3-5 min.

[0014] Further, the vacuum sintering parameters are: vacuum degree 1×10 -3 Pa, sintering temperature 1200-1300 ℃, holding time 120-240 min, and furnace cooling to room temperature after holding.

[0015] Further, the hot extrusion parameters are: extrusion temperature 700-800 DEG C, extrusion ratio 3-10:1, extrusion speed 80-130 mm / s, extrusion pass number >=1, using glass lubricant for lubrication, and air cooling to room temperature after extrusion.

[0016] Further, the hot rolling parameters are: rolling temperature 600-650 DEG C, rolling ratio 2-4:1, rolling speed 20-30 m / min, rolling pass number >=1, and air cooling to room temperature after rolling.

[0017] Further, the homogenization annealing parameters are: annealing temperature 650-700 DEG C, holding time 60-120 min, and air cooling to room temperature after holding.

[0018] Further, the ultrasonic rolling parameters are: rolling head frequency 20-30 kHz, amplitude 10-20 mu m, static pressure 100-200 N, feed speed 4-8 mm / min, and rolling number 2-6 times.

[0019] The application adopts spherical powder as the raw material for preparing Ti-Zr-O alloy by powder metallurgy, the spherical powder has good fluidity and filling property, and can obtain high density and low porosity of the formed blank, thereby improving the strength and toughness of the metal material; in order to further improve the strength of the Ti-Zr-O alloy prepared by powder metallurgy, TiO2 powder is used to introduce oxygen element and control the adding proportion, and the heat treatment system of homogenization annealing and the surface strengthening treatment of ultrasonic rolling are used, so that the Ti-Zr-O alloy has good plasticity and high strength at the same time.

[0020] The application has the advantages that:

[0021] (1) The spherical Ti powder, the spherical Zr powder and the nano TiO2 powder are used in the preparation process, so that the mixed Ti-Zr-O powder has high fluidity, and the occlusion ability between the powders in the cold isostatic pressing process is increased, and the density of the pressed blank is improved.

[0022] (2) On one hand, the oxygen element is introduced by adding appropriate TiO2 powder, the oxygen element enters the interstitial position of the matrix to form Ti-Zr-O alloy by solid solution, and the strength of the material is improved; on the other hand, the organization is refined by deformation strengthening, the oxygen element is uniformly distributed in the matrix by heat treatment, and a work-hardening layer structure is formed on the surface of the Ti-Zr-O alloy by surface strengthening, so that the finally obtained Ti-Zr-O alloy has good comprehensive mechanical properties.

[0023] (3) The process flow is simple and time-saving, and can realize rapid preparation of high-strength and high-ductility Ti-Zr-O alloy, and meet the industrial production demand. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the present invention.

[0025] Figure 2 The image shown is the XRD pattern of Example 3.

[0026] Figure 3 The stress-strain curve is shown in Example 3.

[0027] Figure 4 This is a SEM fracture morphology image of Example 3.

[0028] Figure 5 SEM images of various powders: (a) spherical Ti powder; (b) spherical Zr powder; (c) nano TiO2 powder.

[0029] Figure 6 This shows the distribution of oxygen in the matrix after annealing. Detailed Implementation

[0030] To facilitate understanding of the present invention, the following description will be more comprehensive and detailed in conjunction with the accompanying drawings and preferred embodiments. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0032] Example 1:

[0033] (1) Spherical Ti powder (5-45 μm), spherical Zr powder (5-45 μm), and lamellar nano TiO2 powder (5-10 nm) were weighed in a mass ratio of 84.25:15:0.75. The weighed raw material powder was placed in a vacuum ball mill jar. The ball mill jar was a stainless steel vacuum ball mill jar with a nylon gasket. The grinding media was titanium-plated zirconia grinding balls. Before ball milling, the air in the vacuum ball mill jar was evacuated to ≤0.1 Pa by a vacuum pump. The ball-to-material ratio was 3:1. The speed of the planetary ball mill was 200 rpm. The ball milling time was 120 min. After ball milling, a mixed powder was obtained.

[0034] (2) The mixed powder obtained in step (1) is subjected to cold isostatic pressing at a pressure of 250 MPa and a holding time of 4 min to obtain a molded blank.

[0035] (3) Place the shaped blank obtained in step (2) into a vacuum sintering furnace for vacuum sintering, with a vacuum degree of 1×10⁻⁶. -3Pa, sintering temperature 1250℃, sintering time 240min, after vacuum sintering, the sintered blank is cooled to room temperature in the furnace.

[0036] (4) The sintered blank obtained in step (3) is subjected to two passes of hot extrusion: the first extrusion temperature is 800℃, the extrusion ratio is 4:1, and the extrusion speed is 100mm / s; the second extrusion temperature is 750℃, the extrusion ratio is 6:1, and the extrusion speed is 120mm / s, and after the two passes of extrusion, the extruded blank is air-cooled to room temperature.

[0037] (5) The extruded blank obtained in step (4) is subjected to four passes of hot rolling: the rolling temperature is 650℃, the rolling ratio is 3:1, and the rolling speed is 25m / min, and after the four passes of hot rolling, the rolled blank is air-cooled to room temperature.

[0038] (6) The rolled blank obtained in step (5) is subjected to homogenization annealing: the annealing temperature is 700℃, the holding time is 120min, and after the holding, the annealed blank is air-cooled to room temperature.

[0039] (7) The annealed blank obtained in step (6) is subjected to ultrasonic roll bonding strengthening: the roll head frequency is 30kHz, the amplitude is 15μm, the static pressure is 150N, the feed speed is 6mm / min, and the roll bonding number is 4, to obtain a powder metallurgy prepared high-strength and high-ductility Ti-Zr-O alloy.

[0040] (8) The powder metallurgy prepared high-strength and high-ductility Ti-Zr-O alloy is cut into samples, ground and polished to a mirror surface, and then analyzed for material phase using an X'pert3 and Empyrean type X-ray diffractometer; EDS energy spectrum analysis of the sample is performed using a Verios G4 type ultra-high resolution field emission scanning electron microscope; tensile samples are tested at room temperature using an AG-X plus electronic universal testing machine, three parallel samples are used for each experiment, and the yield strength of the Ti-Zr-O alloy is measured to be 1175.6MPa, the tensile strength is 1223.1MPa, and the elongation is 24.3%.

[0041] Example 2:

[0042] (1) Spherical Ti powder (5-45μm), spherical Zr powder (5-45μm), and lamellar nano-TiO2 powder (5-10nm) are weighed according to a mass ratio of 84.2:15:0.8; the weighed raw material powder is placed in a vacuum ball mill jar, the ball mill jar is a stainless steel vacuum ball mill jar with nylon liner, and the grinding body is a titanium-coated zirconia grinding ball; before ball milling, the air in the vacuum ball mill jar is pumped out to ≤0.1Pa by a vacuum pump, the ball-to-material ratio is 3:1, the planetary ball mill speed is 200rpm, and the ball milling time is 120min, to obtain a mixed powder.

[0043] (2) The mixed powder obtained in step (1) was cold isostatic pressed, with a forming pressure of 250 MPa and a holding time of 4 min, to obtain a formed blank.

[0044] (3) The formed blank obtained in step (2) was vacuum sintered in a vacuum sintering furnace, with a vacuum degree of 1 x 10 -3 Pa, a sintering temperature of 1250 °C, a sintering time of 240 min, and a furnace cooling to room temperature after vacuum sintering, to obtain a sintered blank.

[0045] (4) The sintered blank obtained in step (3) was hot extruded in two passes: a first extrusion temperature of 800 °C, an extrusion ratio of 4:1, and an extrusion speed of 100 mm / s; and a second extrusion temperature of 750 °C, an extrusion ratio of 6:1, and an extrusion speed of 120 mm / s, with air cooling to room temperature after the two-pass extrusion, to obtain an extruded blank.

[0046] (5) The extruded blank obtained in step (4) was hot rolled in four passes: a rolling temperature of 650 °C, a rolling ratio of 3:1, and a rolling speed of 25 m / min, with air cooling to room temperature after the four-pass hot rolling, to obtain a rolled blank.

[0047] (6) The rolled blank obtained in step (5) was homogenized annealed: an annealing temperature of 700 °C, a holding time of 120 min, and air cooling to room temperature after the holding, to obtain an annealed blank.

[0048] (7) The annealed blank obtained in step (6) was subjected to ultrasonic roll-pressing strengthening: a roll head frequency of 30 kHz, an amplitude of 15 pm, a static pressure of 150 N, a feed speed of 6 mm / min, and 4 times of roll-pressing, to obtain a powder metallurgy prepared high-strength and high-ductility Ti-Zr-O alloy.

[0049] (8) The powder metallurgy prepared high-strength and high-ductility Ti-Zr-O alloy was cut into samples, which were ground and polished to a mirror surface, and then analyzed for material phase using an X’pert3 and Empyrean type X-ray diffractometer; EDS energy spectrum analysis of the samples was performed using a Verios G4 type ultra-high resolution field emission scanning electron microscope; and tensile samples were tested at room temperature using an AG-X plus electronic universal testing machine, with three parallel samples used in each experiment, and the yield strength of the Ti-Zr-O alloy was measured to be 1197.7 MPa, the tensile strength was measured to be 1245.8 MPa, and the elongation was measured to be 23.6%.

[0050] Example 3:

[0051] (1) Spherical Ti powder (5-45 μm), spherical Zr powder (5-45 μm), and flaky nano-TiO2 powder (5-10 nm) were weighed according to a mass ratio of 84.15:15:0.85; the weighed raw material powders were placed in a vacuum ball mill pot, the ball mill pot was a stainless steel vacuum ball mill pot with a nylon liner, the grinding body was a titanium-coated zirconia grinding ball, the air in the vacuum ball mill pot was removed by a vacuum pump before ball milling to ≤0.1 Pa, the ball-to-material ratio was 3:1, the rotation speed of the planetary ball mill was 200 rpm, the ball milling time was 120 min, and the mixed powder was obtained after the ball milling was completed.

[0052] (2) The mixed powder obtained in step (1) was cold isostatic pressed to form a blank, the forming pressure was 250 MPa, and the pressure holding time was 4 min, and the blank was obtained.

[0053] (3) The blank obtained in step (2) was placed in a vacuum sintering furnace for vacuum sintering, the vacuum degree was 1×10 -3 Pa, the sintering temperature was 1250℃, the sintering time was 240 min, the sintered blank was obtained after the vacuum sintering and furnace cooling to room temperature.

[0054] (4) The sintered blank obtained in step (3) was subjected to two passes of hot extrusion: the first extrusion temperature was 800℃, the extrusion ratio was 4:1, and the extrusion speed was 100 mm / s; the second extrusion temperature was 750℃, the extrusion ratio was 6:1, and the extrusion speed was 120 mm / s, and the extruded blank was obtained after the two passes of extrusion and air cooling to room temperature.

[0055] (5) The extruded blank obtained in step (4) was subjected to four passes of hot rolling: the rolling temperature was 650℃, the rolling ratio was 3:1, and the rolling speed was 25 m / min, and the rolled blank was obtained after the four passes of hot rolling and air cooling to room temperature.

[0056] (6) The rolled blank obtained in step (5) was subjected to homogenization annealing: the annealing temperature was 700℃, the holding time was 120 min, and the annealed blank was obtained after the holding and air cooling to room temperature.

[0057] (7) The annealed blank obtained in step (6) was subjected to ultrasonic roll pressure strengthening: the roll head frequency was 30 kHz, the amplitude was 15 μm, the static pressure was 150 N, the feed speed was 6 mm / min, and the roll pressure number was 4, and the powder metallurgy prepared high-strength and high-ductility Ti-Zr-O alloy was obtained.

[0058] (8) After the Ti-Zr-O alloy prepared by powder metallurgy with high strength and high ductility is cut into samples, ground and polished to mirror surface, the material phase is analyzed by using X'pert3 and Empyrean type X-ray diffractometer; the EDS energy spectrum analysis of the sample is performed by using Verios G4 type ultra-high resolution field emission scanning electron microscope; the tensile sample is tested at room temperature by using AG-X plus electronic universal testing machine, three parallel samples are used in each experiment, and the yield strength of the Ti-Zr-O alloy is 1229.4 MPa, the tensile strength is 1272.2 MPa, and the elongation is 22.1%.

[0059] Figure 2 It is the XRD pattern of Example 3. It can be known from Figure 2 that the Ti-Zr-O alloy prepared in the application is mainly composed of α phase.

[0060] Figure 3 It is the stress-strain curve of Example 3. It can be known from Figure 3 that the tensile strength of Example 3 is 1272.2 MPa, the yield strength is 1229.4 MPa, and the elongation is 22.1%, which proves that the Ti-Zr-O alloy prepared in the application has high strength and high ductility.

[0061] Figure 4 It is the SEM fracture morphology diagram of Example 3. It can be seen that the fracture micro-morphology of Example 3 is honeycomb-shaped, and the fracture surface is composed of some small pits. The pit is actually a large-sized cavity nucleus, which is usually called “toughness pit”. It is the most basic morphological feature of toughness pit fracture and the most basic basis for identifying toughness pit fracture mechanism. “Toughness pit” fracture is a high-energy absorption process fracture, which is one of the ductile fractures. Figure 4 It is indirectly proved that the Ti-Zr-O alloy prepared in the application has high ductility.

[0062] Figure 6 It is the distribution of oxygen elements in the matrix after annealing. Figure 6 It shows that after annealing treatment, the oxygen elements can be uniformly distributed in the Ti-Zr-O alloy matrix without segregation, so as to form solid solution strengthening, and further enhance the mechanical properties of the Ti-Zr-O alloy prepared in the application.

[0063] Comparative Example 1:

[0064] Liu Y, Tang H, Huang Q, et al. Strong-yet-ductile Ti-Zr alloys through high concentration of oxygen strengthening[J]. Transactions of Nonferrous Metals Society of China. 2020, 30(9): 2449-2458.

[0065] The document uses a mixture of non-spherical Ti powder and non-spherical Zr powder as raw material, adopts cold isostatic pressing and vacuum sintering technology to prepare Ti-Zr alloy, and then uses hot rolling process to strengthen the Ti-Zr alloy. The yield strength of the strengthened Ti-Zr alloy material is 891.2 MPa, the tensile strength is 914.2 MPa, and the elongation is 20.2%.

[0066] Comparative Example 2:

[0067] Liu Y, Tang H, Huang Q, et al. A method for preparing Ti-Zr alloy by powder metallurgy and extrusion [P]. Hunan Province: CN113981261B, 2022-10-28.

[0068] The patent uses a mixture of non-spherical Ti powder and non-spherical Zr powder as raw material, adopts cold isostatic pressing and vacuum sintering technology to prepare Ti-Zr alloy, and then uses extrusion and hot rolling process to strengthen the Ti-Zr alloy. The yield strength of the strengthened Ti-Zr alloy material is 1022 MPa, the tensile strength is 1064.1 MPa, and the elongation is 23.2%.

[0069] Table 1 Mechanical properties of products of examples and comparative examples

[0070]

[0071]

[0072] From the data in Table 1, by adjusting the powder morphology of Ti-Zr-O alloy, introducing and controlling oxygen elements in the matrix, using appropriate heat treatment and surface strengthening process, the strength of Ti-Zr-O alloy can be significantly improved without sacrificing the plasticity of the material. Compared with Comparative Example 1, the yield strength of Ti-Zr-O alloy in the examples is at least increased by 30%, and the tensile strength is increased by nearly 40%, which provides a way for powder metallurgy to develop and prepare high-strength and high-ductility Ti-Zr-O alloy, and has significant economic value.

[0073] The above merely describes preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the present application should be included in the scope of the present application.

Claims

1. A method of powder metallurgical production of a Ti-Zr-O alloy, characterized in that: The method comprises the following steps: (1) preparing powders: Ti powder, Zr powder and TiO2 powder are weighed according to the mass ratio of Ti:Zr:TiO2=84.1-84.3:15:0.7-0.9, and mixed uniformly to obtain mixed powders; (2) forming and sintering: the mixed powders are cold isostatic pressed and then vacuum sintered to obtain sintered blanks; (3) alloy strengthening: the sintered blanks are sequentially subjected to hot extrusion, hot rolling, homogenization annealing and ultrasonic rolling to obtain a Ti-Zr-O alloy; in step (1), the Ti powder is spherical with a particle size of 5-45 μm, and has a composition of C≤0.03%, O≤0.15%, N≤0.03%, H≤0.01%, Fe≤0.05% and the rest of Ti and trace impurities; the Zr powder is spherical with a particle size of 5-45 μm, and has a composition of C≤0.03%, O≤0.03%, N≤0.04%, H≤0.01% and the rest of Zr and trace impurities; the TiO2 powder is lamellar nanoscale powder with a particle size of 5-10 nm and an oxygen content of 35-45%; in step (3), the homogenization annealing parameters are: an annealing temperature of 650-700 ℃, a holding time of 60-120 min, and air cooling to room temperature after the holding time ends; in step (3), the ultrasonic rolling parameters are: a rolling head frequency of 20-30 kHz, an amplitude of 10-20 μm, a static pressure of 100-200 N, a feeding speed of 4-8 mm / min, and a rolling number of 2-6 times.

2. The method of claim 1, wherein: In step (1), the powder mixing is performed by a vacuum ball mill tank, the ball-to-material ratio is 1-5:1, the planetary ball mill rotates at a speed of 50-400 rpm, and the ball milling time is 1-5 h.

3. The method of claim 1, wherein: In step (2), the cold isostatic pressing parameters are: a forming pressure of 200-300 MPa, and a pressure holding time of 3-5 min.

4. The method of claim 1, wherein: The vacuum sintering parameters in step (2) are: vacuum degree 1 x 10 -3 Pa, sintering temperature 1200-1300°C, holding time 120-240 min, and cooling to room temperature after holding.

5. The method of claim 1, wherein: In step (3), the hot extrusion parameters are: an extrusion temperature of 700-800 ℃, an extrusion ratio of 3-10:1, an extrusion speed of 80-130 mm / s, an extrusion pass number of ≥1, and a glass lubricant is used for lubrication, and the extrusion is air cooled to room temperature after the extrusion ends.

6. The method of claim 1, wherein: In step (3), the hot rolling parameters are: a rolling temperature of 600-650 ℃, a rolling ratio of 2-4:1, a rolling speed of 20-30 m / min, a rolling pass number of ≥1, and the rolling is air cooled to room temperature after the rolling ends.

7. A Ti-Zr-O alloy produced according to the method of any one of claims 1 to 6, characterized in that: The tensile strength is greater than 1200 MPa.

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