Method for preparing Zr3Si2 material based on electric arc melting-crushing-sintering

Abstract

The invention discloses a method for preparing a Zr3Si2 material based on electric arc melting, crushing and sintering, and relates to the technical field of zirconium alloy preparation. The preparation method comprises the following steps: firstly, synthesizing a Zr3Si2 material through an electric arc melting method liquid phase reaction, then, carrying out mechanical crushing and ball milling to obtain powder, and finally, carrying out powder densification sintering by using spark plasma sintering, thereby obtaining the Zr3Si2 / Zr3Si2 composite material. The electric arc melting technology is used for providing a high-temperature environment, reactants can be completely molten, molten silicon and zirconium are fully diffused and react, and it is ensured that the product purity is high. And rapid smelting and rapid cooling are achieved through electric arc smelting, the phenomenon of grain growth can be avoided, and a uniform microstructure is formed. Only silicon and zirconium are used as raw materials, no other substances participate in the reaction, the raw materials are pure, the reaction is carried out through a liquid phase, the raw materials are fully mixed, generation of other zirconium-silicon intermetallic compounds is reduced, Zr3Si2 obtained through the reaction is high in purity, and introduction of impurities is reduced to a great extent.

Description

Technical Field

[0001] The invention relates to the technical field of zirconium alloy preparation, and in particular to a method for preparing Zr3Si2 material based on arc melting-crushing-sintering. Background Art

[0002] Zirconium alloys have been widely used in the nuclear industry, aerospace, chemical industry, medical equipment, electronics industry and other fields due to their excellent corrosion resistance, high strength and good high temperature performance. Zr3Si2, as a zirconium-silicon intermetallic compound, is a high-temperature ceramic material with high hardness, high melting point, high electrical conductivity and high thermal conductivity. It also has excellent corrosion resistance and excellent mechanical properties. Due to these superior physical and chemical properties, this type of compound is very suitable as a structural material or new engineering material in high-temperature corrosive media. Especially in nuclear reactors, its low neutron absorption cross section and good radiation resistance make it an ideal choice for nuclear fuel cladding materials.

[0003] There are many types of zirconium-silicon intermetallic compounds. In order to obtain a single product, the stoichiometric ratio of the raw materials needs to be strictly controlled, and the different preparation processes also have an important impact on the purity of the product. x Si y The material method is mainly solid phase reaction, such as reaction sintering, self-propagating high temperature synthesis, mechanical alloying and so on.

[0004] The reaction sintering method focuses on preparing Zr by solid phase reaction. x Si y Materials, this method is suitable for applications that require high uniformity and specific microstructures. In this process, zirconium and silicon powders are mixed in a specific ratio, molded or cold pressed into a preform, and then sintered at a lower temperature that does not reach the melting point. This temperature control is to prevent the material from melting and maintain diffusion and reaction in the solid phase, in order to obtain a uniform microstructure and excellent physical properties. But in order to avoid the liquid phase, the processing temperature must be limited to below 1370°C. However, when the temperature is between 1250°C and 1300°C, diffusion occurs slowly and it is difficult to obtain a fully reacted sample. Self-propagating high-temperature synthesis is particularly suitable for the preparation of inorganic compounds that react rapidly at high temperatures because it uses local heating to trigger chemical reactions, but it is used to prepare Zr x Si y When materials are processed, a large amount of by-products are often produced. Mechanical alloying is time-consuming and only suitable for laboratory research and small-batch production.

[0005] In view of this, the present invention proposes a preparation method capable of preparing high-purity and high-yield Zr3Si2 material. Summary of the invention

[0006] In order to solve the existing methods of preparing Zr by reaction sintering, self-propagating high temperature synthesis and mechanical alloying x Si y In order to overcome the above-mentioned technical defects of the material, the present invention proposes a method for preparing Zr3Si2 material based on arc melting-crushing-sintering. First, the Zr3Si2 material is synthesized by liquid phase reaction of arc melting, then it is mechanically crushed and ball-milled into powder, and finally spark plasma sintering is used to densify the powder to prepare high-purity and high-yield Zr3Si2 material.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing Zr3Si2 material based on arc melting-crushing-sintering, the specific steps are as follows:

[0009] (1) Arc melting synthesis of Zr3Si2: zirconium particles and silicon particles of appropriate proportions are placed in a crucible and then placed in an arc melting furnace. Arc heating and melting are carried out under vacuum. After cooling, a Zr3Si2 ingot is obtained.

[0010] (2) Mechanical crushing and ball milling: The arc-melted ingot is mechanically crushed into fine particles and then ball milled into micron-sized powder;

[0011] (3) Powder densification sintering: The ball-milled powder is densified by plasma discharge sintering.

[0012] As a further preferred technical solution of the present invention, in the preparation method:

[0013] In the step (1), the purity of the zirconium particles is 99.9%, the purity of the silicon particles is 99.9%, the average particle size of the zirconium particles is 3 mm, the particle size of the silicon particles is 3 to 5 mm, and the molar ratio of the zirconium particles to the silicon particles is 3:2.

[0014] In the step (1), zirconium particles and silicon particles are added to a crucible in a manner that the silicon particles are at the bottom and the zirconium particles are at the top, and the crucible is placed in an arc melting furnace; before heating the arc melting furnace, a vacuum treatment is performed to evacuate the air pressure in the furnace to ≤1Pa, and then argon is filled to normal pressure, and the filling and degassing process is repeated at least three times.

[0015] In the step (1), the arc melting furnace is in a vacuum state, and an arc is drawn. The arc size is adjusted by a current control knob. The temperature rises rapidly to 2000°C due to arc heating. At this time, the material has become a liquid phase. The magnetic flow agitator is turned on to maintain uniform arc heating. The liquid phase is evenly mixed at this time, and the temperature is maintained. The mixing time in the liquid phase state is 5 minutes. After the insulation is completed, argon is filled to normal pressure, and the Zr3Si2 ingot is taken out after the temperature is lowered to room temperature in an argon atmosphere.

[0016] In the step (2), the Zr3Si2 ingot is placed in a jaw crusher and crushed repeatedly, and the gap between the jaw plates is adjusted so that the particle size is below 1000 μm.

[0017] In the step (2), the crushed particles and grinding balls are added into a cemented carbide ball mill, and the ball mill is sealed in an argon atmosphere vacuum glove box. The cemented carbide grinding balls are made of tungsten carbide, with a grinding ball diameter of 5 mm, a ball-to-material ratio of 5:1, a rotation speed of 300-600 rpm, and a high-performance ball mill is used for ball milling for 24-36 hours.

[0018] The step (3) comprises the following steps: loading the ball-milled powder into a sintering mold, isolating the mold wall and the powder with carbon paper, placing the mold in a discharge plasma sintering furnace, and evacuating the sintering furnace; setting the initial pressure to 10 MPa, the sintering temperature to 1300°C, the heating rate to 100°C / min, the insulation time to 5 to 15 min, and the sintering pressure to 50 MPa; manually pressurizing the mold to the sintering pressure during the heating process; after the insulation is completed, filling the mold with argon to normal pressure, cooling the mold with the furnace in an argon atmosphere, taking out the product, and grinding the carbon paper on the surface with a grinder to finally obtain the Zr3Si2 material.

[0019] In summary, the current preparation of Zr x Si y The main defects of the material method are:

[0020] 1. Reaction sintering and self-propagating high temperature synthesis methods are solid-phase reactions. The reactants react below the melting point. It is difficult to ensure the mixing uniformity of the reactants by pre-pressing. This may lead to incomplete reaction or uneven product composition, affecting the performance of the material.

[0021] 2. Although the self-propagating high-temperature synthesis method has a fast reaction speed and violent heat release, it is difficult to accurately control the reaction process, which may lead to unstable product quality; and the addition of necessary flux and additives further increases the impurities in the generated products, which has a great impact on maintaining the purity of the material.

[0022] 3. Mechanical alloying has a long reaction time. In order to achieve a complete reaction, it usually requires a long time of ball milling, which will reduce production efficiency; mechanical alloying In the process of mechanical alloying, the diffusion rate between elements is one of the key factors. If zirconium and silicon cannot be fully diffused and mixed during high-energy ball milling, the formation of zirconium silicide will be limited. The process parameters of mechanical alloying, such as ball milling time, rotation speed, ball-to-material ratio, etc., have an important influence on the reaction.

[0023] The present invention can make the chemical composition and physical phase of the bulk material after arc melting more uniform by ball milling after crushing, and obtain small and uniform powder, which is more conducive to improving the density and homogeneity of the sintered material. The rapid sintering method of spark plasma sintering is conducive to reducing grain coarsening and can be directly formed. Compared with the existing preparation method, the prepared Zr x Si y The material has high purity, uniform composition and better mechanical properties. Its beneficial effects are also reflected in:

[0024] 1. The present invention uses arc melting technology to provide extremely high temperatures, usually at 2000°C and above. This high temperature environment helps to completely melt the reactants, and the melted silicon and zirconium fully diffuse and react with each other to ensure high product purity. High-temperature melting helps to volatilize some impurities, especially light impurities, thereby further improving the purity of the product. Long-term high-temperature treatment often leads to grain growth, while arc melting achieves rapid melting and rapid cooling, which can avoid this phenomenon, and high-temperature melting and rapid cooling can form a uniform microstructure.

[0025] 2. The raw materials used in the present invention are only silicon and zirconium, and no other substances participate in the reaction. The raw materials are pure, and the reaction is carried out in the liquid phase. The raw materials are fully mixed to reduce the generation of other zirconium-silicon intermetallic compounds. The Zr3Si2 obtained by the reaction is of high purity, which greatly reduces the introduction of impurities.

[0026] 3. If the bulk material obtained after arc melting does not react fully, there may be uneven composition and structure inside. By crushing and then ball-milling into powder, the chemical composition and physical phase of the material can be made more uniform. Secondary reaction during the sintering process can also reduce the particle size and increase the specific surface area, which is conducive to the uniform shrinkage of particles during the sintering process, avoiding uneven stress distribution and the generation of microcracks, and ultimately obtaining a higher sintering density and improving the overall homogeneity of the material.

[0027] 4. Spark plasma sintering can quickly reach the required sintering temperature in a short time, significantly shorten the sintering time, and is more conducive to minimizing grain coarsening during the sintering process; and the final required part structure can be directly obtained by changing the shape of the sintering mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the process of the preparation method of the present invention.

[0029] Figure 2 This is the XRD pattern of the Zr3Si2 material prepared in Example 1.

[0030] Figure 3 This is the XRD pattern of the Zr3Si2 material prepared in Comparative Example 1.

[0031] Figure 4 This is the XRD pattern of the Zr3Si2 material prepared in Comparative Example 2.

[0032] Figure 5 This is the SEM image of the Zr3Si2 material prepared in Example 1.

[0033] Figure 6 This is the SEM image of the Zr3Si2 material prepared in Comparative Example 1.

[0034] Figure 7 This is the SEM image of the Zr3Si2 material prepared in Comparative Example 2. DETAILED DESCRIPTION

[0035] See also Figure 1 As shown, the present invention proposes a method for preparing Zr3Si2 material based on arc melting-crushing-sintering, firstly synthesizing Zr3Si2 material by liquid phase reaction of arc melting method, then mechanically crushing and ball milling into powder, and finally using spark plasma sintering to densify and sinter the powder to prepare high-purity and high-yield Zr3Si2 material. The present invention is further described in detail below in conjunction with the embodiments and drawings.

[0036] Example 1

[0037] The method for preparing Zr3Si2 material in this embodiment is as follows:

[0038] (1) Arc melting synthesis of Zr3Si2: Weigh zirconium particles (purity of 99.9%, average particle size of 3 mm) and silicon particles (purity of 99.9%, particle size of 3-5 mm) in a mass ratio of 3:2, add them into a crucible with silicon particles at the bottom and zirconium particles at the top, and place the crucible into an arc melting furnace. While ensuring good air tightness in the furnace, evacuate the furnace to ≤1Pa, then fill it with argon to normal pressure. Repeat the filling and degassing process at least three times to achieve near oxygen-free conditions in the furnace. When the arc melting furnace is in vacuum, start to draw an arc, adjust the arc size by the current control knob, and the arc heating causes the temperature to rise rapidly to 2000°C. At this time, the material has become a liquid phase. Turn on the magnetic flow stirrer to keep the arc evenly heated. The liquid phase is evenly mixed at this time, and the temperature is maintained. The mixing time in the liquid phase state is 5 minutes. After the insulation is completed, argon is filled to normal pressure, and the Zr3Si2 ingot is taken out after the temperature is lowered to room temperature in an argon atmosphere.

[0039] (2) Mechanical crushing and ball milling: Wipe the surface of the ingot with anhydrous ethanol and place it in a jaw crusher. The material is crushed repeatedly in the crusher, and the gap between the jaw plates is adjusted continuously to obtain a particle size of less than 1000 μm. The crushed particles are placed in a cemented carbide ball mill, and cemented carbide grinding balls are added. The cemented carbide grinding balls are made of tungsten carbide, with a grinding ball diameter of 5 mm and a ball-to-material ratio of 5:1. The ball mill is sealed in an argon atmosphere vacuum glove box and then placed in a high-energy ball mill with a rotation speed of 400 rpm and a ball milling time of 24 hours. After ball milling, micron-sized Zr3Si2 powder is obtained.

[0040] (3) Powder densification sintering: The ball-milled powder is loaded into a graphite sintering mold, and the mold wall and the powder are isolated with carbon paper. The mold is placed in a discharge plasma sintering furnace, and the sintering furnace is evacuated. The initial pressure is set to 10 MPa, the sintering temperature is set to 1300 °C, the heating rate is set to 100 °C / min, the holding time is set to 10 min, and the sintering pressure is set to 50 MPa. During the heating process, the pressure is manually increased to the sintering pressure. After the holding period is completed, argon is filled to normal pressure, and the mold is cooled in an argon atmosphere. The product is taken out and the carbon paper on the surface is polished with a grinder to finally obtain the Zr3Si2 material.

[0041] Comparative Example 1

[0042] The method for preparing Zr3Si2 material in this comparative example is as follows:

[0043] (1) Precursor powder mixing: Weigh zirconium powder and silicon powder according to the molar ratio of 3:2, place the powder in a cemented carbide ball mill, add cemented carbide grinding balls, the cemented carbide grinding balls are made of tungsten carbide, the grinding ball diameter is 5 mm, and the ball-to-material ratio is 3:1. The ball mill is sealed in an argon atmosphere vacuum glove box and then placed in a high-energy ball mill at a rotation speed of 100 rpm for 30 min to fully mix the powders.

[0044] (2) Powder densification sintering: The ball-milled powder is loaded into a graphite sintering mold, and the mold wall and the powder are isolated with carbon paper. The mold is placed in a discharge plasma sintering furnace, and the sintering furnace is evacuated. The initial pressure is set to 10 MPa, the sintering temperature is set to 1300 °C, the heating rate is set to 100 °C / min, the holding time is set to 10 min, and the sintering pressure is set to 50 MPa. During the heating process, the pressure is manually increased to the sintering pressure. After the holding period is completed, argon is filled to normal pressure, and the mold is cooled in an argon atmosphere. The product is taken out and the carbon paper on the surface is polished with a grinder to finally obtain the Zr3Si2 material.

[0045] Comparative Example 2

[0046] The method for preparing Zr3Si2 material in this comparative example is as follows:

[0047] (1) Powder ball milling alloying: Weigh zirconium powder and silicon powder according to the molar ratio of 3:2, place the powder in a cemented carbide ball mill, add cemented carbide grinding balls, the cemented carbide grinding balls are made of tungsten carbide, the grinding ball diameter is 5 mm, and the ball-to-material ratio is 5:1. The ball mill is sealed in an argon atmosphere vacuum glove box, and then placed in a high-energy ball mill at a speed of 400 rpm for 32 hours. The zirconium and silicon powders react continuously through high-energy collision and friction, and the powder particles are continuously broken and diffused during the reaction process.

[0048] (2) Powder densification sintering: The ball-milled powder is loaded into a graphite sintering mold, and the mold wall and the powder are isolated with carbon paper. The mold is placed in a discharge plasma sintering furnace, and the sintering furnace is evacuated. The initial pressure is set to 10 MPa, the sintering temperature is set to 1300 °C, the heating rate is set to 100 °C / min, the holding time is set to 10 min, and the sintering pressure is set to 50 MPa. During the heating process, the pressure is manually increased to the sintering pressure. After the holding period is completed, argon is filled to normal pressure, and the mold is cooled in an argon atmosphere. The product is taken out and the carbon paper on the surface is polished with a grinder to finally obtain the Zr3Si2 material.

[0049] pass Figure 2It can be seen that in Example 1 of the present invention, the raw materials react in the liquid phase through the arc melting method, the reaction is rapid, and the crushed materials are ball milled and spark plasma sintered, so a large amount of Zr3Si2 phase can be clearly observed in the product, the reaction is completely carried out, and no raw materials remain. The results show that Zr3Si2 materials with high purity can be prepared by synthesizing Zr3Si2 materials through arc melting and then dense sintering, which contains less other products and the reaction is fully carried out.

[0050] pass Figure 3 It can be seen that in Examples 1 and 2, the raw materials are difficult to react quickly at the solid phase temperature through direct solid phase reaction. Under the condition that the insulation time of Example 1 is 10 minutes, the raw materials cannot be fully diffused, so the obtained product contains almost no Zr3Si2 phase.

[0051] It is difficult to explore the appropriate process parameters for the method of preparing Zr3Si2 materials by ball milling alloying, because mechanical alloying mainly relies on mechanical energy to drive the reaction. Therefore, under some unfavorable thermodynamic conditions, the expected phase cannot be formed. Figure 4 It can be seen that the raw materials are difficult to react, and the results are similar to Figure 3 similar.

[0052] pass Figure 5-7 By comparison, it can be seen that the surface of the Zr3Si2 material prepared in Example 1 is smoother and more uniform, without obvious impurities.

[0053] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing Zr3Si2 material based on arc melting-crushing-sintering, characterized in that: First, Zr3Si2 material is synthesized by liquid phase reaction through arc melting method, then it is crushed into powder by mechanical crushing and ball milling, and finally the powder is densified and sintered by spark plasma sintering to prepare high-purity and high-yield Zr3Si2 material.

2. The method according to claim 1, characterized in that The specific steps are as follows: (1) Arc melting synthesis of Zr3Si2: zirconium particles and silicon particles of appropriate proportions are placed in a crucible and then placed in an arc melting furnace. Arc heating and melting are carried out under vacuum. After cooling, a Zr3Si2 ingot is obtained. (2) Mechanical crushing and ball milling: The arc-melted ingot is mechanically crushed into fine particles and then ball milled into micron-sized powder; (3) Powder densification sintering: The ball-milled powder is densified by plasma discharge sintering.

3. The method according to claim 2, characterized in that In the step (1), the purity of the zirconium particles is 99.9%, the purity of the silicon particles is 99.9%, the average particle size of the zirconium particles is 3 mm, the particle size of the silicon particles is 3 to 5 mm, and the molar ratio of the zirconium particles to the silicon particles is 3:

2.

4. The method according to claim 2 or 3, characterized in that In the step (1), zirconium particles and silicon particles are added to a crucible in a manner that the silicon particles are at the bottom and the zirconium particles are at the top, and the crucible is placed in an arc melting furnace; before heating the arc melting furnace, a vacuum treatment is performed to evacuate the air pressure in the furnace to ≤1Pa, and then argon is filled to normal pressure, and the filling and degassing process is repeated at least three times.

5. The method according to claim 4, characterized in that In the step (1), the arc melting furnace is in a vacuum state, and an arc is drawn. The arc size is adjusted by a current control knob. The temperature rises rapidly to 2000°C due to arc heating. At this time, the material has become a liquid phase. The magnetic flow agitator is turned on to maintain uniform arc heating. The liquid phase is evenly mixed at this time, and the temperature is maintained. The mixing time in the liquid phase state is 5 minutes. After the insulation is completed, argon is filled to normal pressure, and the Zr3Si2 ingot is taken out after the temperature is lowered to room temperature in an argon atmosphere.

6. The method according to claim 2, characterized in that In the step (2), the Zr3Si2 ingot is placed in a jaw crusher and crushed repeatedly, and the gap between the jaw plates is adjusted so that the particle size is below 1000 μm.

7. The method according to claim 2 or 6, characterized in that In the step (2), the crushed particles and grinding balls are added into a cemented carbide ball mill, and the ball mill is sealed in an argon atmosphere vacuum glove box. The cemented carbide grinding balls are made of tungsten carbide, with a grinding ball diameter of 5 mm, a ball-to-material ratio of 5:1, a rotation speed of 300-600 rpm, and a high-performance ball mill is used for ball milling for 24-36 hours.

8. The method according to claim 2, characterized in that The step (3) comprises the following steps: loading the ball-milled powder into a sintering mold, isolating the mold wall and the powder with carbon paper, placing the mold in a discharge plasma sintering furnace, and evacuating the sintering furnace; setting the initial pressure to 10 MPa, the sintering temperature to 1300°C, the heating rate to 100°C / min, the insulation time to 5 to 15 min, and the sintering pressure to 50 MPa; manually pressurizing the mold to the sintering pressure during the heating process; after the insulation is completed, filling the mold with argon to normal pressure, cooling the mold with the furnace in an argon atmosphere, taking out the product, and grinding the carbon paper on the surface with a grinder to finally obtain the Zr3Si2 material.

9. Zr3Si2 material prepared by the method according to any one of claims 1 to 8.

Images