Method for preparing TiAl / Al2O3 composite powder with assistance of fused salt

Abstract

The invention discloses a method for preparing TiAl / Al2O3 composite powder with assistance of molten salt, which is characterized by comprising the following steps: effectively mixing reducing agent aluminum powder and titanium dioxide, uniformly mixing with prepared ternary molten salt, putting into a sealed corundum crucible, heating and reacting in a tubular furnace for a period of time, ultrasonically dispersing reactants, and drying to obtain the TiAl / Al2O3 composite powder. And washing the molten salt with deionized water, filtering, drying, collecting the final product to prepare micron-sized TiAl / Al2O3 composite powder, distilling the filtrate obtained by filtering, and recrystallizing to obtain the molten salt again.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of composite powders, and specifically relates to a method for preparing TiAl / Al composite powders with the aid of molten salt. 2 O 3 Method for compounding powders. Background Art

[0002] In the range of 300-900℃, compared with many high-temperature titanium alloys and nickel-based alloys, TiAl alloy has lower density, higher specific strength, and higher tensile properties; the most widely used titanium alloy Ti-6Al-4V has a maximum operating temperature below 350℃, while TiAl alloy can be used for a long time at a high temperature of about 800℃, making it a high-quality structural material for the titanium alloy series in the high-temperature field. However, studies have found that TiAl alloys still have defects, such as poor high-temperature strength and fracture toughness, which limit their further application. For this reason, the introduction of Al 2 O 3 The second reinforcement phase can improve its performance. 2 O 3 It is considered to be the best particle reinforcement phase of TiAl-based alloys. It has excellent properties such as high hardness, light weight, good rigidity, good chemical stability and high temperature resistance. With the continuous development of cutting-edge technology and high-tech industries, metal additive manufacturing near-net shaping technology has developed rapidly due to its advantages of manufacturing complex and precise metal components and low raw material consumption. However, the TiAl / Al required for forming 2 O 3 Composite powders require expensive production costs, which restricts their application in aerospace precision devices and other important fields, further highlighting the importance of metal powder preparation methods. Therefore, it is necessary to develop a low-cost, simple process TiAl / Al 2 O 3 The preparation process of composite powder is an important and meaningful task.

[0003] my country is the country with the largest reserves of titanium resources, with TiO 2 It exists in the form of mineral materials with TiO as the main component. 2 Directly prepare TiAl / Al 2 O 3 Composite powder can significantly reduce production costs. TiO 2 Reduction preparation of TiAl / Al 2 O 3 Composite powders are divided into molten salt electrolysis and thermal reduction. At present, molten salt electrolysis still needs to further solve the problems of electrolyte composition fluctuation, low solubility and high impurities; while the use of metal aluminum thermal reduction TiO 2 Direct preparation of TiAl / Al 2 O 3Composite powder has the characteristics of cheap raw materials, short preparation process and less impurities. Self-propagating aluminothermic reduction reaction easily leads to metal thermal sintering and agglomeration. The byproduct aluminum oxide is easily mixed with the alloy, slag-gold separation is difficult, and the reaction conditions cannot be accurately controlled. The composite material prepared by in-situ synthesis technology has good thermodynamic stability and good compatibility with the matrix. Using pressureless sintering method and adding appropriate molten salt, TiO 2 It increases the flow and contact between aluminum and metal, prevents the adhesion between metal and metal, metal and oxide, and is conducive to the elimination of impurities, so as to obtain micron-sized TiAl / Al 2 O 3 Composite powder.

[0004] The present invention provides a molten salt assisted preparation method of TiAl / Al 2 O 3 Composite powder method. With cheap TiO 2 As raw materials, it reduces costs and is conducive to mass production; TiAl / Al is prepared by aluminothermic method 2 O 3 The requirements and specific processes required for the composite powder reaction are simple and feasible, and can minimize the incorporation of irrelevant variables and other impurities; multiple cycles of vacuuming and introducing argon can reduce O 2 、N 2 , CO 2 Pollution to alloy powder; the ternary molten salt prepared by this method has high thermal stability and is more suitable for use at about 950°C. It effectively controls the morphology and particle size of powder particles, effectively reduces product agglomeration, and effectively reduces the adhesion of aluminum slag and alloy. The prepared product is ultrasonically treated, washed with deionized water, and dried, and no residue remains in the molten salt. After filtering and distillation, the ternary molten salt can be used again. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention aims to provide a molten salt assisted preparation method of TiAl / Al 2 O 3 The method comprises the following steps: using aluminum powder as a reducing agent, mixing aluminum powder and TiO 2 Mix evenly at a molar ratio of 1:2.072; put into a sealed corundum crucible after effective mixing, and heat to 950°C in a tube furnace at a heating rate of 5°C / min; maintain stable reaction at 1 atmosphere and keep warm for 4 hours; liquid metal aluminum converts TiO 2 The alloy powder is synthesized in situ by complex chemical reactions. The ternary molten salt is prepared by mixing chloride salts in different proportions. For example, the molar fractions are: 41.72% NaCl, 52.16% CaCl 2,6.12% KCl; the alloy powder prepared by the aluminothermic method was ultrasonically dispersed for 30 minutes; then washed with deionized water and alcohol to remove the molten salt, filtered, dried, and the final product was collected to obtain TiAl / Al 2 O 3 The composite powder has a particle size of less than 100 μm; the filtrate obtained by filtration is distilled, and the molten salt can be obtained again after crystallization, which can be put into production and recycled.

[0006] The technical solution of the present invention is as follows:

[0007] A molten salt assisted preparation of TiAl / Al 2 O 3 The method of composite powder is carried out according to the following process steps:

[0008] (1) Sodium chloride, potassium chloride and calcium chloride are mixed uniformly in proportion, heated to 700°C to melt, and kept warm for 3 hours;

[0009] (2) mixing titanium dioxide and aluminum powder in a theoretical ratio and adding them to the ternary molten salt of step (1), heating to 950° C. at a heating rate of 5° C. / min and performing a reduction reaction for 4 h;

[0010] (3) After the reactants are cooled to room temperature, the generated TiAl / Al 2 O 3 The composite powder was dispersed by ultrasound and filtered out with deionized water;

[0011] (4) recrystallizing the ternary molten salt obtained in step (3) and recycling it to be reused in the next step (1);

[0012] The present invention prepares TiAl / Al 2 O 3 The advantages of composite powder are as follows:

[0013] 1. The present invention uses low-cost titanium dioxide and metal aluminum as raw materials to directly prepare TiAl / Al 2 O 3 Composite powder does not use other reaction gases and compounds, reducing the incorporation of other elements; compared with atomization, mechanical alloying and powder metallurgy, the operation method is simple and does not require crushing; compared with self-propagating thermal reduction and molten salt electrolysis, the product only needs simple water washing and ethanol washing, reducing environmental pollution and significantly reducing costs;

[0014] 2. The present invention uses ternary molten salt as a solvent for metal thermal reduction reaction, aluminum powder as a reducing agent, and a replacement reaction and alloying are carried out at 950°C under an argon protection environment to prepare TiAl / Al 2 O 3Composite powder reduces the reaction temperature, speeds up the alloying efficiency, and most of the by-product Al 2 O 3 Filtering and removing together with molten salt can effectively reduce the incorporation of impurities;

[0015] 3. The process flow of the present invention is shortened, the preparation process is simple, the technical difficulty is small, it is suitable for mass production, and the ternary molten salt can be recycled and reused; BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 TiAl / Al 2 O 3 XRD patterns of composite powders;

[0017] Best Mode

[0018] The present invention is described in detail below with reference to the embodiments but is not intended to limit the protection scope thereof.

[0019] A molten salt assisted preparation of TiAl / Al 2 O 3 The method of composite powder is carried out according to the following process steps:

[0020] (1) taking a certain amount of titanium dioxide, sodium chloride, calcium chloride, and potassium chloride and placing them in a drying oven, heating them to 200° C., keeping them warm for 24 hours, removing moisture from the raw materials, and setting them aside;

[0021] (2) After grinding the three chloride salts, use mechanical stirring to mix them evenly in a certain proportion, put them into a high-temperature box-type resistance furnace and heat them to 700℃ for 3 hours to make the molten salt completely melt to form a mixed molten salt, and prepare a ternary molten salt for use. The chloride salts are divided into: 41.72% NaCl, 52.16% CaCl 2 ,6.12% KCl;

[0022] (3) titanium dioxide and aluminum powder are effectively mixed in a certain proportion, and then the mixture is added to the mixed molten salt of step (2), placed in a sealed corundum crucible, and argon gas is continuously introduced at 300 ml / min, and the temperature is increased to 950°C at a rate of 5°C / min and kept warm for 4 hours, wherein the molar ratio of titanium dioxide to aluminum is 1:2.072, and the amount of mixed molten salt is 1.5 times the total mass of the mixture;

[0023] (4) After the reaction is completed, wait for the sample to cool to room temperature, separate the generated black mixture by ultrasonication for 30 minutes, wash it with deionized water several times and filter it, wash it with an appropriate amount of anhydrous ethanol, repeat this operation twice, and then vacuum dry it to obtain the reacted alloy particles; use rotary evaporation to distill out the molten salt from the filtered filtrate and dry it for later use;

[0024] In this embodiment, the molten salt medium obtained by distillation can be recycled and reused in the next preparation process.

Claims

1. A method for preparing TiAl / Al2O3 composite powder with the aid of molten salt, characterized in that The process is carried out in the following steps: effectively mix the reducing agent aluminum powder and titanium dioxide, then mix them evenly with the prepared ternary molten salt, put them into a sealed corundum crucible, heat and react in a tube furnace for a period of time, disperse the reactants by ultrasonic, wash the molten salt with deionized water, filter, dry, collect the final product, and obtain micron-sized TiAl / Al2O3 composite powder. Distill the filtrate obtained by filtration, and recrystallize to obtain molten salt again.

2. The method for preparing TiAl / Al2O3 composite powder with the aid of molten salt according to claim 1, characterized in that: The molar ratio of the metallic aluminum to TiO2 is 2.

072.

3. The method for preparing TiAl / Al2O3 composite powder with the aid of molten salt according to claim 1, characterized in that: The pressure in the tube furnace was maintained at 1 atmosphere, the heating rate was 5°C / min, and the reaction temperature was 950°C.

4. The method for preparing TiAl / Al2O3 composite powder with the aid of molten salt according to claim 1, characterized in that: The insulation time after reaching the reaction temperature is 4 hours.

5. The method for preparing TiAl / Al2O3 composite powder with the aid of molten salt according to claim 1, characterized in that: The ternary chloride molten salt is prepared by mixing chloride salts in different proportions, for example, in terms of molar fractions, respectively: 41.72% NaCl, 52.16% CaCl2, 6.12% KCl.

6. The method for preparing TiAl / Al2O3 composite powder with the aid of molten salt according to claim 1, characterized in that: The product prepared by the aluminothermic reduction alloying needs to be subjected to ultrasonic dispersion for 30 minutes.

7. The method for preparing TiAl / Al2O3 composite powder with the aid of molten salt according to claim 1, characterized in that: The TiAl / Al2O3 composite powder obtained by the aluminothermic reduction reaction has a particle size of about 0 to 100 μm.

8. The method for preparing TiAl / Al2O3 composite powder with the aid of molten salt according to claim 1, characterized in that: The product is dried under vacuum conditions at a temperature of 30-50°C for at least 24 hours.

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