CN111515408A

CN111515408A - NiTi alloy powder and preparation method and application thereof

Info

Publication number: CN111515408A
Application number: CN202010399330.8A
Authority: CN
Inventors: 闫志巧; 陈�峰; 施麒; 徐平; 毛新华; 刘辛
Original assignee: Guangdong Institute of Materials and Processing
Current assignee: Guangdong Institute of Materials and Processing
Priority date: 2020-05-12
Filing date: 2020-05-12
Publication date: 2020-08-11
Anticipated expiration: 2040-05-12
Also published as: CN111515408B

Abstract

The invention discloses a NiTi alloy powder and a preparation method and application thereof, wherein the preparation method of the NiTi alloy powder comprises the following steps: alloying the uniformly mixed NiTi mixed powder at the temperature of 600-900 ℃, and spheroidizing the obtained alloy-crushed powder by using radio frequency plasma; wherein the heating rate of the NiTi mixed powder in the process of heating from 300 ℃ to 600-900 ℃ is not more than 1.5 ℃/min. By strictly controlling the temperature rise rate of 300-600-900 ℃, pure-phase NiTi alloy can be generated between Ni powder and Ti powder in the alloying process of NiTi mixed powder, the burning loss of Ni element and component deviation caused by the burning loss can be effectively reduced in the spheroidizing process of plasma, and the generation of impurity phases is inhibited. Therefore, the finally obtained NiTi alloy powder has the advantages of fine particle size, concentrated particle size distribution, good sphericity, less defects and high phase purity.

Description

NiTi alloy powder and preparation method and application thereof

Technical Field

The invention relates to the technical field of powder metallurgy, in particular to NiTi alloy powder and a preparation method and application thereof.

Background

The NiTi shape memory alloy has unique hyperelasticity and shape memory functions, excellent comprehensive mechanical property, biocompatibility, corrosion resistance and the like, and has wide application prospects in the fields of aerospace, medical instruments, chemical engineering and the like. However, the NiTi alloy has high melting point and poor mechanical processing performance, and the NiTi shape memory alloy part prepared by the traditional casting and forging method has higher cost and difficult complex shape acquisition, thereby greatly limiting the use of the NiTi shape memory alloy. The 3D printing technology developed in recent years is expected to provide a feasible solution for manufacturing NiTi alloy parts having complex shapes at low cost.

NiTi shape memory alloy is an intermetallic compound, and some impurity phases such as Ni are easily generated in the preparation process₃Ti、NiTi₂、Ni₄Ti₃And the like. These impurity phases not only cause a reduction in mechanical properties of the material, impairing the shape memory effect and superelasticity of the material, but also cause a reduction in biocompatibility due to the Ni-rich phase. More importantly, part of the impurity phase (e.g. NiTi)₂) Once formed, it is difficult to remove by subsequent heat treatment. Therefore, the preparation of high-purity-phase NiTi alloy powder is very important for obtaining high-quality 3D printing NiTi alloy parts.

The current raw materials for 3D printing of NiTi alloy comprise NiTi alloy powder and mixed powder of Ni powder and Ti powder. The NiTi alloy powder is mainly prepared by three methods, namely a plasma rotating electrode atomization method (PREP), an electrode induction melting atomization method (EIGA) and a plasma fuse atomization method (PA). In general, the atomization method is relatively high in preparation cost, and besides, the NiTi alloy powder prepared by the PREP method is relatively coarse in particle size, contains impurity phases, has high energy requirements for 3D printing, and is easy to generate large-size impurities in the printing process. The NiTi alloy powder prepared by the EIGA method not only has low fine powder yield, but also has the defects of satellite powder, hollow powder, special-shaped powder and the like, and influences the density of a 3D printed part. The PA method needs to use a NiTi alloy wire with a small diameter as a raw material, and further increases the price of NiTi alloy powder. In order to reduce the cost, part of 3D printing NiTi alloy parts take mixed powder of Ni powder and Ti powder as raw materials. The mixed powder inevitably causes composition segregation, eventually leading to deterioration in the performance of the printed matter.

Therefore, the existing NiTi powder for 3D printing generally has the problems that the phase purity, the particle size and distribution, the fluidity and the like cannot meet the printing requirements, and the cost is generally high.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide NiTi alloy powder and a preparation method and application thereof so as to improve the problems.

The invention is realized by the following steps:

in a first aspect, an embodiment of the present invention provides a method for preparing NiTi alloy powder, including: alloying the uniformly mixed NiTi mixed powder at the temperature of 600-900 ℃, and spheroidizing the obtained alloy-crushed powder by using radio frequency plasma; wherein the heating rate of the NiTi mixed powder is not more than 1.5 ℃/min in the process of continuously heating to 600-900 ℃ after the temperature of the NiTi mixed powder is raised to 300 ℃.

In a second aspect, an embodiment of the present invention further provides a NiTi alloy powder prepared by the method for preparing a NiTi alloy powder described in the foregoing embodiment.

In a third aspect, embodiments of the present invention also provide a NiTi shape memory alloy component prepared from the NiTi alloy powders of the preceding embodiments.

In a fourth aspect, embodiments of the present invention also provide a 3D printed NiTi alloy component printed by a 3D printing technique using the NiTi alloy powder of the previous embodiments.

In a fifth aspect, an embodiment of the present invention further provides an application of the NiTi alloy powder of the foregoing embodiment in preparing a NiTi shape memory alloy, optionally, the NiTi shape memory alloy is a 3D-printed NiTi alloy.

The above embodiment of the invention has at least the following beneficial effects:

by strictly controlling the heating rate of 300-600-900 ℃, the uniformly mixed NiTi mixed powder is alloyed at the temperature of 600-900 ℃, pure-phase NiTi alloy can be generated between Ni powder and Ti powder in the alloying process, then the pure-phase NiTi alloy powder is subjected to radio frequency plasma spheroidization, the burning loss of Ni element and component deviation caused by the burning loss can be effectively reduced in the plasma spheroidization process, and Ni is inhibited₃Ti、NiTi₂、Ni₄Ti₃And the formation of impurity phases. Therefore, the finally obtained NiTi alloy powder has the advantages of fine particle size, concentrated particle size distribution, good sphericity, less defects and high phase purity.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a physical diagram of comparative example 1;

FIG. 2 is a scanning electron micrograph of the NiTi alloy powder of example 1;

FIG. 3 is a scanning electron micrograph of the NiTi alloy powder of example 2;

FIG. 4 is a scanning electron micrograph of the NiTi alloy powder of example 4;

FIG. 5 SEM photograph of the NiTi alloy powder of example 5;

FIG. 6 is a scanning electron micrograph of the NiTi alloy powder of comparative example 2;

FIG. 7 is an XRD pattern of the NiTi alloy powder of example 1;

FIG. 8 is an XRD pattern of the NiTi alloy powder of example 2;

FIG. 9 is an XRD pattern of the NiTi alloy powder of example 4;

FIG. 10 is an XRD pattern of the NiTi alloy powder of example 5;

fig. 11 is an XRD spectrum of the NiTi alloy powder of comparative example 2.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The following is a detailed description of the NiTi alloy powder provided by the invention, its preparation method and application.

In a first aspect, some embodiments of the present invention provide a method of preparing a NiTi alloy powder, including: alloying the uniformly mixed NiTi mixed powder at the temperature of 600-900 ℃, and spheroidizing the obtained alloy-crushed powder by using radio frequency plasma; wherein the heating rate of the NiTi mixed powder is not more than 1.5 ℃/min in the process of continuously heating to 600-900 ℃ after the temperature of the NiTi mixed powder is raised to 300 ℃.

The radio frequency plasma spheroidizing technology is characterized in that irregular powder particles fed into plasma are rapidly heated and melted by utilizing the high-temperature characteristic of the plasma, and the melted particles are rapidly solidified under the combined action of surface tension and extremely high temperature gradient to form spherical powder. The plasma has the advantages of high temperature, large volume of the plasma torch, high energy density, no electrode pollution, high heat transfer and cooling speed and the like, and is a good way for preparing high-quality spherical powder with uniform components, high sphericity and good fluidity. In the 3D printing process, in order to achieve good powder laying and feeding effects, the 3D printing has high requirements on the sphericity of the powder, so that in the above embodiment, the alloy powder can be regular spherical and high in sphericity after being spheroidized by the radio frequency plasma.

However, if the conventional NiTi mixed powder is used for radio frequency plasma spheroidizing, the Ni element is easy to burn and damageThe overall composition deviation of the alloy, the large fluctuation of the molar ratio of Ni/Ti among different particles, and the generation of impurities. Therefore, in the above embodiment, the uniformly mixed NiTi mixed powder is further alloyed, and then the crushed alloy powder is subjected to rf plasma spheroidizing, so that the burning loss of Ni element and the component deviation caused by the burning loss can be effectively reduced in the plasma spheroidizing process, and Ni can be suppressed₃Ti、NiTi₂、Ni₄Ti₃And the formation of impurity phases. Further, to achieve the above effects, the alloying process needs to be controlled so that the Ni powder and the Ti powder can generate a pure-phase alloy, otherwise, the high temperature of the plasma spheroidizing process still causes deviation of the components of the alloy powder obtained after spheroidizing and existence of impurity phases. Therefore, in the technical scheme, the temperature rise rate of 300-600-900 ℃ is strictly controlled not to exceed 1.5 ℃/min, so that the temperature can be slowly raised, and the pure-phase NiTi alloy can be obtained at 600-900 ℃.

Specifically, the NiTi mixed powder that is uniformly mixed may be a mixture of Ni powder and Ti powder that are uniformly mixed together by sufficient stirring or other means. In some embodiments, the molar ratio of Ni to Ti in the NiTi mixed powder may be 50-51: 50-49. For example, the molar ratio of Ni and Ti in the NiTi mixed powder may be 50: 50, or 50: 49, or 51:50, or 51: 49, or 50.5: 49.5.

in some embodiments, in order to obtain better alloying effect, the Ni powder and the Ti powder in the NiTi mixed powder also have certain requirements on the particle size, for example, the particle size of both Ni powder and Ti powder is less than 200 mesh.

Further, in some embodiments, the preparing of the NiTi mixed powder includes: mixing Ni powder and Ti powder to obtain NiTi premixed powder, and ball milling. By means of ball milling, on one hand, coarse powder can be used as a raw material, and raw material cost is reduced; on the other hand, the Ni and Ti elements can be distributed more uniformly while the powder is thinned, and the subsequent alloying and spheroidizing effects are improved.

Specifically, the process for preparing the NiTi premixed powder comprises the step of mixing Ni powder and Ti powder for 4-8 hours in proportion, wherein the particle size of the Ni powder is less than or equal to 45 microns, and the particle size of the Ti powder is less than or equal to 75 microns.

In order to avoid the problem that powder is adhered to the inner wall of a grinding ball or a ball milling tank in the ball milling process and improve the powder yield and the uniformity of the powder size, in some embodiments, a process control agent can be added in the ball milling process, and optionally, the addition amount of the process control agent is 0.4-0.8% of the mass of the NiTi premixed powder. For example, the amount of addition is 0.5%, 0.6%, 0.7% or 0.8% of the mass of the NiTi premixed powder. Further, the process control agent includes, but is not limited to, any one of paraffin, stearic acid, absolute ethanol, and petroleum ether, and preferably, the process control agent is paraffin or stearic acid.

In order to achieve a better ball milling effect, in some embodiments, the ball-to-material ratio during ball milling may be 9 to 11: 1, preferably, the ball milling ratio is 10: 1. the rotating speed during ball milling can be 300-400 rpm; the ball milling time can be 5-20 h.

Further, in some embodiments, the ball milled powder is sieved through a 200 mesh sieve.

Further, when a process control agent is added during ball milling, the process control agent may have an effect on the subsequent alloying, and thus, some embodiments summarize that the step of preparing the NiTi mixed powder further comprises removing the process control agent from the ball-milled powder.

Specifically, removing the process control agent from the ball-milled powder may include placing the ball-milled powder in a vacuum of 1 × 10 or less^-1The mixture is placed under the conditions of MPa and the temperature of 200-300 ℃ for 1-3 h.

Further, in some embodiments, the temperature rising rate in the process of continuing to rise to 600-900 ℃ after rising to 300 ℃ is 1-1.5 ℃/min.

Optionally, the whole process of the alloying process is to ensure that the vacuum degree is less than or equal to 1 × 10^-3Pa, and the like.

In some embodiments, the NiTi mixed powder is processed under the vacuum degree of less than or equal to 1 × 10^-3Heating to 300 ℃ at a speed of 5-10 ℃/min under the condition of Pa, and then heating to 600-900 ℃ at a speed of 1-1.5 ℃/min. The alloying is not affected by the rapid heating rate below 300 ℃, but the impurity phase is caused by the excessive heating rate above 300 DEG CAnd further influences the plasma spheroidizing effect.

Specifically, the treatment time is 1-2 h at the temperature of 600-900 ℃.

Further, before spheroidizing by radio frequency plasma, it is necessary to crush the alloy obtained by alloying so that the spheroidizing process can be well performed. Specifically, the pulverization process is carried out by ball milling. In some embodiments, the ball milling speed adopted in the alloy crushing process is 80-100 rpm, and the ball milling time is 1-2 h; preferably, the crushed material is sieved through a 300-mesh sieve.

Parameters of the spheroidization process of the radio frequency plasma also have great influence on the spheroidization effect, wherein the influence factors are the plasma power and the powder feeding rate. Therefore, in some embodiments, in order to better adapt to the plasma spheroidization of the NiTi alloy powder, the plasma power of the radio frequency plasma spheroidization treatment can be 25 to 40kW, and the powder feeding rate can be 20 to 60 g/min.

In some embodiments, the method for preparing the NiTi alloy powder may specifically include the steps of:

(1) mixing powder: mixing Ni powder with the particle size of less than or equal to 45 microns and Ti powder with the particle size of less than or equal to 75 microns as raw materials for 4-8 hours according to the molar ratio of Ni to Ti of 50-51: 50-49 to obtain NiTi premixed powder;

(2) ball milling: adding paraffin or stearic acid which accounts for 0.4-0.8% of the total mass of the NiTi premixed powder as a process control agent, ball-milling for 5-20 h at a ball-material ratio of 10:1 and a rotating speed of 300-400 rpm, and sieving by a 200-mesh sieve;

(3) a control agent for the removing process, namely, the ball-milled powder is processed in a vacuum degree of less than or equal to 1 × 10^-1Degreasing at 200-300 ℃ under MPa for 1-3 h to obtain NiTi mixed powder;

(4) alloying, namely, mixing NiTi mixed powder at the vacuum degree of less than or equal to 1 × 10^-3Heating to 300 ℃ at a speed of 5-10 ℃/min under the condition of Pa, heating to 600-900 ℃ at a speed of 1-1.5 ℃/min, preserving heat for 1-2 h, cooling to room temperature, ball-milling at a rotating speed of 80-100 rpm for 1-2 h, crushing, and sieving with a 300-mesh sieve;

(5) spheroidizing by radio frequency plasma: spheroidizing the crushed and sieved alloy powder under the conditions that the plasma power is 25-40 kW and the powder feeding speed is 20-60 g/min to obtain the NiTi alloy powder.

In a second aspect, some embodiments of the present invention further provide a NiTi alloy powder prepared by the method for preparing a NiTi alloy powder according to any of the foregoing embodiments. The NiTi alloy powder has the advantages of sphericity, high phase purity, fine particle size, concentrated particle size distribution, good fluidity and the like.

In a third aspect, some embodiments of the present invention also provide a NiTi shape memory alloy component made from the NiTi alloy powder of the previous embodiments. The NiTi shape memory alloy component is prepared from the NiTi alloy powder, so that the NiTi shape memory alloy component has high quality, namely superelasticity and stable shape memory function.

In a fourth aspect, some embodiments of the present invention also provide a 3D printed NiTi alloy component printed by 3D printing techniques using the NiTi alloy powder of the previous embodiments. The 3D printed NiTi alloy part is low in manufacturing cost and can be an alloy part with a complex shape.

In a fifth aspect, some embodiments of the present invention also provide a use of the NiTi alloy powder of the previous embodiments in the preparation of a NiTi shape memory alloy, optionally, the NiTi shape memory alloy is a 3D printed NiTi alloy.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

(1) Ni powder with the grain diameter less than or equal to 45 mu m and Ti powder with the grain diameter less than or equal to 75 mu m are used as raw materials, and the molar ratio of Ni: ti 50.5: 49.5, weighing the powder, and placing the powder into a conical mixer to mix for 8 hours to obtain NiTi premixed powder.

(2) Putting the obtained NiTi premixed powder into a ball milling tank, adding paraffin accounting for 0.4 percent of the total mass of the NiTi premixed powder, ball milling for 20 hours at the rotating speed of 300rpm, and sieving by a 200-mesh sieve.

(3) Putting the ball-milled powder into a ceramic boat, putting the ceramic boat into a vacuum furnace to remove paraffin, and maintaining the vacuum degree in the furnace to be less than or equal to 1 × 10 during the whole paraffin removal period^-1And (5) degreasing at the temperature of 200 ℃ for 3h under MPa to obtain NiTi mixed powder.

(4) Transferring the NiTi mixed powder into a high vacuum furnace, and maintaining the vacuum degree in the furnace to be less than or equal to 1 × 10^-3Pa, heating to 300 ℃ at the speed of 5 ℃/min, heating to 600 ℃ at the speed of 1 ℃/min, preserving heat for 2h, cooling to room temperature, taking the powder out of the furnace, placing the powder into a ball milling tank, ball milling for 2h at the rotating speed of 80rpm, crushing, and sieving with a 300-mesh sieve.

(5) And starting systems such as a system torch and a powder feeding probe cooling water for radio frequency plasma spheroidization, and purifying a reaction chamber, a powder feeder and a powder collector of the radio frequency plasma spheroidization powder preparation device in a mode of repeatedly vacuumizing and filling argon. And (3) inputting a certain amount of argon continuous flow into the plasma reactor, so that the central gas argon flow is 17L/min, and the sheath gas argon flow is 50L/min. Setting the initial pressure of the reaction chamber to be 2psia, loading a high voltage with a voltage of 7kV by a radio frequency induction coil, simultaneously carrying out arc starting discharge to ionize argon gas to generate an argon plasma torch, adding high-purity helium gas (more than or equal to 99.999 percent) into sheath gas, and controlling the flow of the helium gas to be 8L/min.

And then conveying the crushed alloy powder into a high-temperature area at the center of the plasma torch by using carrier gas for heating. The heating time was terminated as the gas/powder stream "flown off" the plasma torch for about 150 milliseconds, yielding NiTi alloy powder. Wherein the plasma power is 25kW, and the powder feeding rate is 20 g/min.

Example 2

(1) Ni powder with the grain diameter less than or equal to 45 mu m and Ti powder with the grain diameter less than or equal to 75 mu m are used as raw materials, and the molar ratio of Ni: ti 50.5: 49.5, weighing the powder, and placing the powder into a conical mixer to mix for 4 hours to obtain NiTi premixed powder.

(2) Putting the obtained NiTi premixed powder into a ball milling tank, adding stearic acid accounting for 0.8 percent of the total mass of the NiTi premixed powder, ball milling for 5 hours at the rotating speed of 400rpm, and sieving by a 200-mesh sieve.

(3) Putting the ball-milled powder into a ceramic boat, putting the ceramic boat into a vacuum furnace to remove stearic acid, and maintaining the vacuum degree in the furnace to be less than or equal to 1 × 10 during the whole period of removing stearic acid^-1And (5) degreasing at the temperature of 300 ℃ for 1h under MPa to obtain NiTi mixed powder.

(4) Transferring the NiTi mixed powder into a high vacuum furnace, and maintaining the vacuum degree in the furnace to be less than or equal to 1 × 10^-3Pa, then raising the temperature at 5 ℃/minAnd heating to 900 ℃ at the speed of 1.5 ℃/min at the temperature of 300 ℃, preserving heat for 1h, cooling to room temperature, taking the powder out of the furnace, putting the powder into a ball milling tank, carrying out ball milling at the rotating speed of 100rpm for 1h, crushing, and sieving with a 300-mesh sieve.

(5) In radio frequency plasma spheroidizing equipment, spheroidizing the crushed alloy powder under the conditions of plasma power of 40kW and powder feeding speed of 60g/min to obtain NiTi alloy powder, and performing other operations of radio frequency plasma spheroidizing according to example 1.

Example 3

(1) Ni powder with the grain diameter less than or equal to 45 mu m and Ti powder with the grain diameter less than or equal to 75 mu m are used as raw materials, and the molar ratio of Ni: and Ti is 50: and weighing 50 powder, and placing the powder into a conical mixer to mix for 6 hours to obtain NiTi premixed powder.

(2) Putting the obtained NiTi premixed powder into a ball milling tank, adding stearic acid accounting for 0.6 percent of the total mass of the NiTi premixed powder, ball milling for 10 hours at the rotating speed of 350rpm, and sieving by a 200-mesh sieve.

(3) Putting the ball-milled powder into a ceramic boat, putting the ceramic boat into a vacuum furnace to remove stearic acid, and maintaining the vacuum degree in the furnace to be less than or equal to 1 × 10 during the whole period of removing stearic acid^-1And (5) degreasing at 250 ℃ under MPa for 1.5h to obtain NiTi mixed powder.

(4) Transferring the NiTi mixed powder into a high vacuum furnace, and maintaining the vacuum degree in the furnace to be less than or equal to 1 × 10^-3Pa, heating to 300 ℃ at the speed of 8 ℃/min, heating to 700 ℃ at the speed of 1.2 ℃/min, preserving heat for 1.3h, cooling to room temperature, taking the powder out of the furnace, placing the powder into a ball milling tank, ball milling for 1h at the rotating speed of 100rpm, crushing, and sieving with a 300-mesh sieve.

(5) In radio frequency plasma spheroidizing equipment, spheroidizing the crushed alloy powder under the conditions of plasma power of 35kW and powder feeding rate of 40g/min to obtain NiTi alloy powder, and performing other operations of radio frequency plasma spheroidizing according to example 1.

Example 4

(5) In radio frequency plasma spheroidizing equipment, spheroidizing the crushed alloy powder under the conditions of plasma power of 15kW and powder feeding rate of 15g/min to obtain NiTi alloy powder, and performing other operations of radio frequency plasma spheroidizing according to example 1.

Example 5

The difference between the embodiment and the embodiment 3 is only that the plasma power is 45kW and the powder feeding rate is 70g/min during the spheroidizing of the radio frequency plasma.

Comparative example 1

This comparative example differs from example 1 only in that in step (4), the NiTi mixed powder was transferred into a high vacuum furnace and the degree of vacuum in the furnace was maintained at 1 × 10 or less^-3Pa, then raising the temperature to 900 ℃ at the speed of 2 ℃/min. Because the rate of temperature rise is too fast, the reaction is too violent and splashes of metal droplets are produced (as shown in FIG. 1 below).

Comparative example 2

This comparative example differs from example 1 only in that the rf plasma spheroidizing of step (5) was directly performed without performing alloying treatment after the removal of step (4), i.e., ball milling.

Test examples

The NiTi alloy powders obtained in examples 1, 2, 4 and 5 and comparative example 2 were observed by scanning electron microscopy to form images, and fig. 2, 3, 4, 5 and 6 were obtained, respectively. It can be seen from the comparative example that the NiTi alloy powder in the examples of the present invention has a more uniform size and a better morphology than the NiTi alloy powder of comparative example 2 shown in fig. 6.

The NiTi alloy powders of example 1, example 2, example 4 and example 5 and comparative example 2 were further analyzed by XRD to obtain XRD patterns as shown in fig. 7, fig. 8, fig. 9, fig. 10, fig. 11.

In conclusion, the NiTi alloy powder prepared by the embodiment of the invention has the advantages of fine particle size, concentrated particle size distribution, good sphericity, less defects, high phase purity and lower preparation cost.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of NiTi alloy powder is characterized by comprising the following steps: alloying the uniformly mixed NiTi mixed powder at the temperature of 600-900 ℃, and spheroidizing the obtained alloy-crushed powder by using radio frequency plasma; after the temperature of the NiTi mixed powder is raised to 300 ℃, the temperature rise rate in the process of continuously raising the temperature to 600-900 ℃ is not more than 1.5 ℃/min.

2. The method for producing a NiTi alloy powder according to claim 1, wherein the molar ratio of Ni to Ti in the NiTi mixed powder is 50 to 51:50 to 49.

3. The method for producing a NiTi alloy powder according to claim 1, characterized in that the step of producing the NiTi mixed powder includes: mixing Ni powder and Ti powder to obtain NiTi premixed powder, and performing ball milling;

preferably, the particle size of the Ni powder is less than or equal to 45 mu m, and the particle size of the Ti powder is less than or equal to 75 mu m;

preferably, a process control agent is added in the ball milling process, more preferably, the addition amount of the process control agent is 0.4-0.8% of the mass of the NiTi premixed powder, preferably, the process control agent comprises any one of paraffin, stearic acid, absolute ethyl alcohol and petroleum ether, more preferably, the process control agent is paraffin or stearic acid;

preferably, the ball-to-material ratio during ball milling is 9-11: 1, more preferably, the ball milling ratio is 10: 1;

preferably, the rotation speed during ball milling is 300-400 rpm;

preferably, the ball milling time is 5-20 h;

preferably, the ball-milled powder is sieved through a 200 mesh sieve.

4. The method for producing a NiTi alloy powder according to claim 3, characterized in that the producing step of the NiTi mixed powder further includes removing a process control agent in the powder after ball milling;

preferably, the removing of the process control agent from the ball-milled powder comprises placing the ball-milled powder in a vacuum of 1 or less 1 × 10^-1The mixture is placed under the conditions of MPa and the temperature of 200-300 ℃ for 1-3 h.

5. The method for producing a NiTi alloy powder according to any one of claims 1 to 4, wherein the rate of temperature rise in the process of continuing to raise the temperature to 600 to 900 ℃ is 1 to 1.5 ℃/min after raising the temperature to 300 ℃;

preferably, the whole process of the alloying process is under the vacuum degree of less than or equal to 1 × 10^-3Is carried out under the condition of Pa;

preferably, the NiTi mixed powder is processed under the condition that the vacuum degree is less than or equal to 1 × 10^-3Heating to 300 ℃ at a speed of 5-10 ℃/min under the condition of Pa, and then heating to 600-900 ℃ at a speed of 1-1.5 ℃/min;

preferably, the treatment time is 1-2 h at the temperature of 600-900 ℃;

preferably, the alloy obtained by alloying is crushed by ball milling, and preferably, the ball milling rotating speed adopted in the alloy crushing process is 80-100 rpm, and the ball milling time is 1-2 h; preferably, after crushing, a 300 mesh screen is passed.

6. The method for producing a NiTi alloy powder according to any one of claims 1 to 4, wherein the plasma power of the radio frequency plasma spheroidization is 25 to 40kW, and the powder feeding rate is 20 to 60 g/min.

7. A NiTi alloy powder characterized by being produced by the method for producing a NiTi alloy powder according to any one of claims 1 to 6.

8. A NiTi shape memory alloy component prepared from the NiTi alloy powder of claim 7.

9. A 3D printed NiTi alloy component characterized in that it is printed by 3D printing technique using the NiTi alloy powder of claim 7.

10. Use of the NiTi alloy powder of claim 7 in the preparation of a NiTi shape memory alloy, preferably a 3D printed NiTi alloy.