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CN-121976075-A - Preparation method of tungsten-rhenium alloy for controlling second phase size

CN121976075ACN 121976075 ACN121976075 ACN 121976075ACN-121976075-A

Abstract

A preparation method of tungsten-rhenium alloy for controlling the second phase size belongs to the technical field of preparation of anode targets of medical CT machines. The invention synthesizes W-10wt% Re-xAl 2 O 3 precursor powder by adopting a wet chemical method, wherein the content of Al 2 O 3 is realized by regulating and controlling the addition amount of aluminum nitrate pentahydrate in the precursor. The precursor powder is reduced by a tube furnace to obtain alloy powder. Subsequently, powder densification is achieved by SPS sintering, followed by rolling to improve bulk properties. The invention explores the influence of the content of a second phase (Al 2 O 3 ) on the alloy performance and the influence of different processes on the size of the second phase, and aims to determine the optimal content interval of the alloy to meet the severe working condition requirement of a medical CT machine target. The invention determines an effective path for preparing the high-performance W-10wt% Re alloy by combining SPS and introducing a second phase through experiments, and the path has the advantages of process simplification and microstructure regulation.

Inventors

  • LUO LAIMA
  • LIU CHANG
  • CHEN YUE
  • LI GUOFAN
  • Chen Jiuxiong
  • WU YUCHENG

Assignees

  • 合肥工业大学

Dates

Publication Date
20260505
Application Date
20260309

Claims (8)

  1. 1. A method for preparing a tungsten-rhenium alloy with controlled second phase size is characterized in that ammonium rhenate, oxalic acid and aluminum nitrate pentahydrate are firstly utilized to prepare a tungsten-rhenium precursor through a wet chemical method, then tungsten-rhenium precursor powder is prepared through spray drying, then the tungsten-rhenium precursor powder is reduced to obtain tungsten-rhenium alloy powder, and finally SPS sintering and rolling are carried out to prepare the tungsten-rhenium alloy.
  2. 2. The method of preparing a tungsten rhenium alloy for controlling the size of a second phase as claimed in claim 1, comprising the steps of: preparing tungsten-rhenium precursor by wet chemical method Firstly adding ammonium metatungstate powder into deionized water until the ammonium metatungstate powder is fully dissolved, heating the solution in a magnetic stirrer, adjusting a rotor to a proper rotating speed, heating, adding ammonium rhenate into the solution after the temperature is stabilized, sequentially adding aluminum nitrate pentahydrate and oxalic acid after the ammonium rhenate is fully stirred and dissolved, stabilizing the temperature at 100-120 ℃ after the oxalic acid is fully dissolved, allowing the solution to react for 3-5 hours, and obtaining a tungsten-rhenium precursor solution after the solute reaction is complete; step two, spray drying the tungsten-rhenium precursor solution prepared in the step one Heating the spray drying, heating the air inlet temperature to 200-230 ℃, connecting a feed inlet with a tungsten-rhenium precursor solution after the air outlet temperature is stable, starting a peristaltic pump, and collecting powder in a collecting tank after the precursor solution is spray dried to obtain tungsten-rhenium precursor powder; Step three, reduction Spreading a tungsten-rhenium precursor in a sintering boat, putting the sintering boat in a hydrogen reduction furnace, then introducing hydrogen, preserving heat for 2-4 hours at the temperature of 1000-1100 ℃, and cooling to obtain tungsten-rhenium alloy powder; SPS sintering The sintering process includes applying initial axial pressure 3KN to the sample, regulating infrared hole position to 200A, regulating current to 400A at 200A/min, maintaining 400A until the vacuum degree of SPS is reduced to 1X 10 -4 Pa, continuing to increase to 600A at 200A/min, starting secondary pressurization, uniformly pressurizing to 15KN within 1min, increasing current to 1500A at 100A/min after pressurization, maintaining 1min, sintering, and cooling to below 100 ℃ along with furnace to take out; Step five, rolling The SPS sintered body is subjected to 1250 ℃ hot rolling treatment, the process parameters are set to be the temperature rising rate of 15-20 ℃ per minute, the temperature is kept for 1h after the SPS sintered body is heated to the target temperature of 1250 ℃, and the total deformation is controlled through four-six passes of rolling.
  3. 3. The method for preparing a tungsten-rhenium alloy according to claim 2, wherein in the first step, ammonium rhenate, oxalic acid and aluminum nitrate pentahydrate are added in amounts of 11.94%, 3.8% and 0.57% -2.9% of the mass of the ammonium metatungstate, respectively.
  4. 4. The method of preparing a tungsten-rhenium alloy according to claim 2, wherein the tungsten-rhenium precursor solution prepared in step one has a solids content of 25% -32%.
  5. 5. The method for preparing a tungsten-rhenium alloy with controlled second phase size according to claim 2, wherein the spray drying parameters in the second step are set to be that the air inlet temperature is 200-230 ℃, the air outlet temperature is 100-120 ℃, the rotating speed of an atomizer is 300-350 r/min, and the feeding rate is 1-2L/h.
  6. 6. The method of manufacturing a tungsten-rhenium alloy according to claim 2, wherein in step three, the temperature is raised to 1000-1100 ℃ at 8-12 ℃ per minute, the temperature is kept for 2-4 hours, the temperature is lowered to 480-520 ℃ at 8-12 ℃ per minute, and then the temperature is cooled to room temperature along with the furnace.
  7. 7. The method for preparing the tungsten-rhenium alloy with the second phase size according to claim 2, wherein the total deformation amount is 40% through five-pass rolling in the fifth step, specifically, the first-pass deformation is 12%, the roll gap is controlled to be 3.52mm, the second-pass deformation is 10%, the roll gap is controlled to be 3.12mm, the third-pass deformation is 8%, the roll gap is controlled to be 2.8mm, the fourth-pass deformation is 6%, the roll gap is controlled to be 2.56mm, the fifth-pass deformation is 4%, and the final roll gap is 2.4mm, and the process is used for rolling step by step from the initial thickness of 4mm to the final thickness of 2.4mm in a way of reducing the roll gap in a step-by-step manner to reach the required deformation amount.
  8. 8. The tungsten-rhenium alloy prepared by the method of any of claims 1-7.

Description

Preparation method of tungsten-rhenium alloy for controlling second phase size Technical Field The invention belongs to the technical field of preparation of anode targets of medical CT machines, and particularly relates to a preparation method of a tungsten-rhenium alloy with a second phase size controlled. Background CT (Computeried Tomography) -computed tomography has become an important tool for modern medical diagnostics. The quality of the performance of the CT machine depends largely on the quality of the X-ray tube. The anode target is a vital component of the X-ray tube, which directly affects the X-ray emission intensity and the lifetime of the bulb. When the X-ray tube works, the anode target is bombarded by high-energy electron beams to emit X-rays. However, the conversion rate of energy is very low, about 1% or so, about 99% or more of the energy is converted into heat energy, and the heat is mainly concentrated on the anode. The overall target temperature of the anode target in a vacuum environment can rise very high, with ambient temperatures above 1300 ℃ and local temperatures up to 2600 ℃ reported for X-ray tube operation. Therefore, the CT machine rotary anode target material is required to have the characteristics of high melting point, high heat capacity, low high-temperature vapor pressure, good thermal shock resistance and the like. Tungsten has extremely high elastic modulus (407 Gpa at room temperature), high melting point (3410 ℃) and high-temperature strength, but because the X-ray tube is operated intermittently, the target material is easy to crack when in cold and hot, and tungsten has a notch sensitive effect, so that crack expansion and deepening are easy to cause, the crack is peeled off from a substrate, and after the crack expansion deepens, the substrate material is exposed to electron beam bombardment to generate X rays with unnecessary wavelength, and the X-ray tube is damaged. In order to improve the comprehensive performance of pure tungsten, a small amount of rhenium is added into the tungsten, the atomic numbers of rhenium element and tungsten element are similar, the rhenium element has similar physical and chemical properties, infinite solid solution is easier to form, and the addition of rhenium reduces the pears stress of the plastic deformation of the tungsten so as to improve the toughness of the tungsten. The tungsten is used as a target surface material to greatly improve the electron bombardment resistance of the target surface due to a solid solution strengthening and toughening mechanism caused by adding rhenium element, so that the dose attenuation speed is effectively reduced, the sensitivity of a pure notch is reduced, and the service life of the target disc is greatly prolonged. The W-Re alloy has become a key material of a medical CT machine bulb tube target disc due to the high melting point, excellent electron bombardment resistance and good X-ray emission efficiency. However, in the actual service process, the target material needs to bear instantaneous and high-frequency thermal shock of high-energy electron beams, and the severe quenching and quenching thermal cycle generated by the instantaneous and high-frequency thermal shock induces significant thermal stress, so that the target disc is easy to generate thermal fatigue cracking. The failure mode not only directly shortens the service life of the target, but also introduces fluctuation of X-ray output and uneven spatial distribution, thereby generating CT image artifacts and finally damaging the image quality and reliability of clinical diagnosis. In order to break through the bottleneck, second phase reinforcing particles are introduced into the W-Re alloy matrix, and the thermal fatigue resistance and the high-temperature structural stability of the W-Re alloy matrix are improved through a dispersion strengthening mechanism, so that the W-Re alloy matrix is an effective way for prolonging the service life of a target. Wherein, al 2O3 is used as a classical high Wen Misan strengthening phase, and can show remarkable improvement on recrystallization temperature, high-temperature strength and creep resistance in tungsten-based alloy. The strengthening characteristic of Al 2O3 is combined with the inherent excellent performance of the W-Re alloy, so that the comprehensive performance of the target is expected to be synergistically optimized, and the imaging quality and the service life of CT equipment are improved at the source. In addition, the forming process of the W-Re alloy has a decisive influence on the microstructure and the final performance of the W-Re alloy in the aspect of material preparation. At present, two technical paths of high-temperature pressureless sintering and spark plasma sintering are mainly adopted. The former process is relatively simple, but leads to coarsening of crystal grains and uneven distribution of the second phase, while the latter can realize low-temperature