CN112941367B - Nano oxide dispersion reinforced heat-resistant zirconium alloy and preparation method thereof - Google Patents

Abstract

The invention discloses a nanometer oxide dispersion reinforced heat-resistant zirconium alloy, which comprises a zirconium alloy matrix, and Y-Ti-O and Y-Zr-O nanometer oxide precipitated phases dispersed in the zirconium alloy matrix, wherein the granularity of the Y-Ti-O and Y-Zr-O nanometer oxide precipitated phases is 2-10nm, and the number density is 1-3 multiplied by 10 ¹⁵ Per m ² . According to the nanometer oxide dispersion reinforced heat-resistant zirconium alloy, a re-dissolution and re-precipitation mechanism of a solute is realized through a mechanical alloying and thermal densification mode, Y-Ti-O and Y-Zr-O nanometer oxide phases with high number density, low nanometer scale, high thermal stability and dispersion distribution are obtained in a zirconium alloy matrix, and the strength and heat resistance of the zirconium alloy can be greatly improved. The invention also provides a preparation method of the nanometer oxide dispersion reinforced heat-resistant zirconium alloy.

Description

A kind of nano-oxide dispersion reinforced heat-resistant zirconium alloy and preparation method thereof

technical field

The invention relates to the technical field of alloy materials, in particular to a nano-oxide dispersion-reinforced heat-resistant zirconium alloy and a preparation method thereof.

Background technique

Zirconium alloys have the advantages of low neutron absorption cross section, corrosion resistance, easy processing and forming, and good radiation stability, and are widely used in the manufacture of nuclear reactor fuel cladding tubes and other core structural components. At present, zirconium alloys for nuclear use are all prepared by melting and casting methods. After heat treatment, intermetallic compound-type precipitation phases are formed to achieve dispersion strengthening of the zirconium alloy matrix. There are serious segregation of ingots, uneven structure and composition, and coarse grains. In addition, the thermal stability of intermetallic compounds is poor. Under high temperature service conditions, the precipitates and grains are prone to rapid coarsening, which seriously limits the zirconium zirconium. Alloy service temperature and strength and other issues. Due to these limitations, although the melting point of pure zirconium is as high as 1850°C, the current working temperature of zirconium alloys for nuclear use generally cannot exceed 350°C.

With the development of advanced third- and a half-generation nuclear reactor technologies and the fourth-generation nuclear reactor technology under development, a high-strength heat-resistant zirconium alloy with a working temperature of over 500°C is urgently needed.

In view of this, the purpose of the present invention is to provide a new zirconium alloy material to solve the above technical problems.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a nano-oxide dispersion reinforced heat-resistant zirconium alloy, which realizes the re-dissolution and re-precipitation mechanism of the solute through mechanical alloying and thermal densification, and obtains high number density and low density in the zirconium alloy matrix. Nanoscale, high thermal stability, and dispersed Y-Ti-O and Y-Zr-O nano-oxide phases can greatly improve the strength and heat resistance of zirconium alloys.

In order to solve the above-mentioned problems, the technical scheme of the present invention is as follows:

A nano-oxide dispersion-enhanced heat-resistant zirconium alloy, comprising a zirconium alloy matrix, Y-Ti-O and Y-Zr-O nano-oxide precipitation phases dispersed in the zirconium alloy matrix, wherein the Y-Ti-O and The particle size of the Y-Zr-O nano-oxide precipitation phase is 2-10 nm, and the number density is 1-3×10 ¹⁵ /m ² .

Further, the structures of the nano-oxide precipitation phases are Y ₂ Ti ₂ O ₇ and Y ₂ Zr ₂ O ₇ .

Further, the zirconium alloy matrix includes the following components by weight percentage:

Sn 1.2-1.6%, Fe 0.2-0.5%, Cr 0.1-0.3%, the balance is Zr and inevitable impurities.

The present invention also provides a preparation method of nano-oxide dispersion reinforced heat-resistant zirconium alloy, comprising the following steps:

Step S1, the zirconium alloy block is subjected to hydrodehydrogenation treatment to obtain pre-alloyed powder;

In step S2, the powder material and pre-alloyed powder containing Y, Ti, O elements are put into a high-speed pendulum ball mill, and fully mixed under the protection of an inert gas to obtain a mixed powder;

In step S3, the mixed powder is subjected to high-energy ball milling under the protection of an inert gas, and the solute elements are dissolved back into the matrix in the form of Y, Ti, and O solid solution atoms to form a mechanically alloyed powder with a supersaturated solid solution structure;

In step S4, the mechanically alloyed powder is cold-pressed into a compact, which is put into a package and evacuated, and the compact is densified. O and Y-Zr-O nano-oxide precipitation phase, wherein the particle size of Y-Ti-O and Y-Zr-O nano-oxide precipitation phase is 2-10nm, and the number density is 1-3×10 ¹⁵ /m ² .

Further, the structures of the nano-oxide precipitation phases are Y ₂ Ti ₂ O ₇ and Y ₂ Zr ₂ O ₇ .

Further, in step S1, the zirconium alloy block includes the following components by weight percentage:

Sn 1.2-1.6%, Fe 0.2-0.5%, Cr 0.1-0.3%, the balance is Zr and inevitable impurities;

The temperature of the hydrogenation and dehydrogenation treatment processes is 300-500°C, respectively;

The particle size of the obtained pre-alloyed powder is 5-20 μm, and the hydrogen content does not exceed 100 ppm.

Further, in step S2, the powder materials containing Y, Ti and O elements are YH ₂ powder and TiO ₂ powder, Y ₂ O ₃ powder and TiH ₂ powder, Y ₂ O ₃ powder and pure Ti powder, or pure Y powder and one of the four combinations of TiO ₂ powder;

Among them, the powder material containing Y element has an average particle size of 1-20 μm, and its addition amount is 0.1-2% of the weight of the pre-alloyed powder, and the average particle size of the powder material containing Ti element is less than 1 μm, and its addition amount is the weight of the pre-alloyed powder. 0.1-1%.

Further, the powder materials containing Y, Ti and O elements are YH ₂ powder and TiO ₂ powder, or Y ₂ O ₃ powder and TiH ₂ powder.

Further, in step S3, the mechanical alloying process adopts an omnidirectional planetary ball mill, the disk surface speed is 400-600rpm, the longitudinal speed is 10-20rpm, the mass ratio of balls to material is 10-20:1, and the ball milling time is 20-40h; and Every 15-30min of ball milling, stop for 2-3min and change the direction of forward and reverse.

Further, in step S4, the mechanical alloyed powder is cold-pressed into a compact by a tablet press, the pressure is 20-40MPa, and the pressure is maintained for 1h; the envelope is evacuated, and the vacuum degree is ^10-3 Pa; hot isostatic pressing is adopted For densification, the hot isostatic pressing pressure is 150-200MPa, the pressure is maintained for 4-6h, and the temperature is 1100-1300°C.

Compared with the prior art, the nano-oxide dispersion-reinforced heat-resistant zirconium alloy and its preparation method provided by the present invention have the beneficial effects of:

The nano-oxide dispersion-enhanced heat-resistant zirconium alloy and the preparation method thereof provided by the invention are fully mixed with pre-alloyed powder, powder materials containing Y and Ti elements, and high-energy ball milling, so as to realize the mechanical alloying of the zirconium alloy powder; Static pressure achieves complete densification, making the density > 99%, no macrosegregation of components, and uniform and fine grains;

The added Y- and Ti-containing powders are easy to be broken, refined and decomposed during the mechanical alloying process, and the solute elements are dissolved back into the matrix in the form of Y, Ti, O solid solution atoms to form a supersaturated solid solution. During the hot isostatic pressing process The solute atoms in the solid solution reacted and precipitated again to form Y-Ti-O and Y-Zr-O oxide precipitates with ultra-high number density, low nanoscale, and dispersed distribution, among which Y-Ti-O and Y-Zr The particle size of the -O nano-oxide precipitation phase is 2-10 nm, and the number density is 1-3×10 ¹⁵ /m ² . The nano-oxide precipitation phase has high thermal stability and corrosion resistance, and a large amount of precipitation occurs in the grain and grain boundaries. It has strong ability to pin dislocations and grain boundaries at high temperatures, and can inhibit the recrystallization of grains, thereby greatly improving the Strength and heat resistance of zirconium alloys. The nano-oxide dispersion-reinforced heat-resistant zirconium alloy provided by the invention also has higher yield strength when the working temperature is increased to above 500 DEG C, and has excellent high-temperature mechanical properties.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

Fig. 1 is the transmission electron microscope (TEM) photograph of the nano-oxide dispersion reinforced heat-resistant zirconium alloy prepared in Example 1 of the present invention;

2 is a microstructure selected area electron diffraction (SAD) analysis diagram of the nano-oxide dispersion-enhanced heat-resistant zirconium alloy prepared in Example 1 of the present invention;

3 is a comparison diagram of the mechanical properties of the nano-oxide dispersion-reinforced heat-resistant zirconium alloy prepared in the embodiment of the present invention and the zirconium alloy prepared in the comparative example under different temperature conditions.

Detailed ways

In order for those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are further described below.

The endpoints of ranges and any values disclosed herein are not limited to the precise ranges or values, which are to be understood to encompass values proximate to those ranges or values. For ranges of values, the endpoints of each range, the endpoints of each range and the individual point values, and the individual point values can be combined with each other to yield one or more new ranges of values that Ranges should be considered as specifically disclosed herein.

A preparation method of nano-oxide dispersion reinforced heat-resistant zirconium alloy, comprising the following steps:

Step S1, the zirconium alloy block is subjected to hydrodehydrogenation treatment to obtain pre-alloyed powder;

Specifically, the zirconium alloy block includes the following components by weight percentage:

Sn 1.2-1.6%, Fe 0.2-0.5%, Cr 0.1-0.3%, the balance is Zr and inevitable impurities;

The hydrogenation adopts a gas tube furnace, and the hydrogenation temperature is 300-500 ° C. After hydrogenation, it is crushed by ball milling for 5-10 hours and the rotation speed is 300 rpm to obtain hydrogenated alloy powder; 20μm pre-alloyed powder with hydrogen content not exceeding 100ppm.

In step S2, the powder material and pre-alloyed powder containing Y, Ti, O elements are put into a high-speed pendulum ball mill, and fully mixed under the protection of an inert gas to obtain a mixed powder;

Specifically, the powder materials containing Y, Ti and O elements are YH ₂ powder and TiO ₂ powder, Y ₂ O ₃ powder and TiH ₂ powder, Y ₂ O ₃ powder and pure Ti powder, or pure Y powder and TiO ₂ powder One of these four combinations; preferably YH ₂ powder and TiO ₂ powder, or Y ₂ O ₃ powder and TiH ₂ powder, the powder materials of these two combinations can be dispersed evenly when added to the pre-alloyed powder, so that the later formation can be achieved. The oxide precipitate phase structure is more stable. Among them, the powder purity: 99.9% for _TiO2 , 99.9% for _YH2 , or 99.9% for _Y2O3 and 99.9% for TiH2 _; the amount of powder material containing Y element is _0.1-2 % by weight of the pre-alloyed powder , the addition amount of the powder material containing Ti element is 0.1-1% of the weight of the pre-alloyed powder;

It is premixed by a high-speed pendulum ball mill and fully mixed under the protection of inert gas, so that the average particle size of the powder containing Y element is 1-20 μm, and the average particle size of the powder containing Ti element is less than 1 μm. Through argon protection, adjusting the introduction method and addition amount of Y, Ti, O elements, the content of H and O elements in the alloy is effectively controlled, and the preparation of high-activity metal zirconium alloy by powder metallurgy is realized.

In step S3, the mixed powder is subjected to high-energy ball milling under the protection of an inert gas, and the solute elements are dissolved back into the matrix in the form of Y, Ti, and O solid solution atoms to form a mechanically alloyed powder with a supersaturated solid solution structure;

Specifically, the mechanical alloying process adopts an omnidirectional planetary ball mill, the disk surface speed is 400-600rpm, the longitudinal speed is 10-20rpm, the mass ratio of balls to material is 10-20:1, and the ball milling time is 20-40h; 30min, stop for 2-3min and change the direction of forward and reverse, which is beneficial to ensure the effect of mechanical alloying.

All-round planetary high-energy ball mill, the temperature of the cooling system is set to 0 °C, and the grinding balls and ball mill jars are made of zirconia material to ensure the safe and efficient process of mechanical alloying of high-activity zirconium alloys.

In step S4, the mechanically alloyed powder is cold-pressed into a compact, which is put into a package and evacuated, and the compact is densified. O and Y-Zr-O nano-oxide precipitation phase, wherein the particle size of Y-Ti-O and Y-Zr-O nano-oxide precipitation phase is 2-10nm, and the number density is 1-3×10 ¹⁵ /m ² .

In this process, the mechanically alloyed powder with high surface activity is mechanically cold pressed into a compact in an argon gas glove box, and then vacuumized after wrapping, which can effectively prevent the oxidation and flammability of the powder in direct hot isostatic pressing.

Specifically, the mechanically alloyed powder is cold-pressed into a compact by a tablet press, the pressure is 20-40MPa, and the pressure is maintained for 1h; the envelope is evacuated, and the vacuum degree is ^10-3 Pa; The hot isostatic pressing pressure is 150-200MPa, the holding pressure is 4-6h, and the temperature is 1100-1300℃; the structures of the formed nano-oxide precipitates are Y ₂ Ti ₂ O ₇ and Y ₂ Zr ₂ O ₇ .

Among them, the cold pressing method can be replaced by a cold isostatic pressing method, and the hot isostatic pressing densification method can be replaced by a method such as hot extrusion or spark plasma sintering.

The nano-oxide dispersion-reinforced heat-resistant zirconium alloy and its preparation method provided by the present invention are described in detail below through specific examples.

Example 1

A preparation method of nano-oxide dispersion reinforced heat-resistant zirconium alloy, comprising the following steps:

Step S1, preparation of pre-alloyed powder: put the zirconium alloy ingot into a gas tube furnace, hydrogenate it at 500°C to obtain a zirconium hydride ingot, put the zirconium hydride ingot into a ball mill, the rotating speed is 300rpm, and the ball milling time is 5h to quickly break it to obtain hydrogenation Alloy powder, the hydrogenated alloy powder is dehydrogenated at 500°C to obtain pre-alloyed powder, the average particle size of the pre-alloyed powder is 5-20 μm, and the hydrogen content does not exceed 100 ppm;

The zirconium alloy block includes the following components by weight:

Sn 1.3%, Fe 0.2%, Cr 0.1%, the balance is Zr and inevitable impurities;

Step S2, powder premixing: TiO ₂ powder with a weight of 0.4 wt % of the pre-alloyed powder, 0.4 wt % of the YH ₂ powder and the pre-alloyed powder are put into a high-speed pendulum ball mill for pre-mixing, the vibration time is 1 h, and the frequency is 1400 rpm to obtain mixed powder;

Step S3, mechanical alloying: put the mixed powder into a zirconia ball milling jar, and perform ball milling under argon protection. The temperature of the system is set to 0°C, and the solute elements are dissolved back into the matrix in the form of Y, Ti, O solid solution atoms to form a mechanical alloyed powder with a supersaturated solid solution structure;

Step S4, densification molding: the mechanical alloyed powder is mechanically cold pressed at 50 MPa for 1 hour to form a compact, then packed into a package and evacuated, and the vacuum degree is 10 ^-3 Pa; The pressure was 200MPa, the pressure was maintained for 4h, and the temperature was 1200℃. The dissolved solute atoms in the zirconium alloy matrix reacted and precipitated again to obtain Y-Ti-O and Y-Zr-O nano-oxide dispersion-reinforced zirconium alloys.

The nano-oxide dispersion-enhanced heat-resistant zirconium alloy of Example 1 was subjected to precipitation phase crystal plane measurement, and the measurement results were shown in Table 1:

Table 1: The calibration results of the interplanar spacing of the precipitation phase of the nano-oxide dispersion-reinforced zirconium alloy prepared in Example 1

According to the calibration results in Table 1, it can be preliminarily concluded that the precipitated phases are Y ₂ Ti ₂ O ₇ and Y ₂ Zr ₂ O ₇ nano-oxide phases. Since the crystal structures of the two phases are exactly the same, and the lattice constants are very close (the difference is about 4%), the two phases have coexistence characteristics from the distribution divergence of the measured interplanar spacing.

Please refer to FIG. 1 and FIG. 2 in combination, wherein FIG. 1 is a transmission electron microscope (TEM) photograph of the nano-oxide dispersion-enhanced heat-resistant zirconium alloy prepared in Example 1 of the present invention; Selected area electron diffraction (SAD) analysis of the microstructure of the oxide dispersion-enhanced heat-resistant zirconium alloy. The crystal phase structures shown in Figures 1 and 2 show that a large number of dispersed low-nano-oxide precipitates are formed in the alloy matrix. After testing, the particle size of the precipitates is 2-10nm, and the number density can reach 1-3×10 ¹⁵ /m ² .

Example 2

Step S1, preparation of pre-alloyed powder: put the zirconium alloy ingot into a gas tube furnace, hydrogenate it at 500°C to obtain a zirconium hydride ingot, put the zirconium hydride ingot into a ball mill, the rotating speed is 300rpm, and the ball milling time is 5h to quickly break it to obtain hydrogenation Alloy powder, hydrogenated alloy powder is dehydrogenated at 500°C to obtain pre-alloyed powder;

The zirconium alloy block includes the following components by weight:

Sn 1.3%, Fe 0.2%, Cr 0.1%, the balance is Zr and inevitable impurities;

Step S2, powder premixing: the pre-alloyed powder weight of 0.4wt% Y ₂ O ₃ powder, 0.4wt% TiH ₂ powder and pre-alloy powder are put into a high-speed pendulum ball mill for pre-mixing, the vibration time is 1h, and the frequency is 1400rpm , to obtain mixed powder;

Step S3, mechanical alloying: put the mixed powder into a zirconia ball milling jar, perform ball milling under the protection of argon gas, the ball milling time is 40h, the rotating speed of the disk surface is 300 rpm, the longitudinal rotating speed is 20 rpm, the mass ratio of ball to material is 10:1, and cooling is performed. The temperature of the system is set to 0°C, and the solute elements are dissolved back into the matrix in the form of Y, Ti, O solid solution atoms to form a mechanical alloyed powder with a supersaturated solid solution structure;

Step S4, densification molding: the mechanical alloyed powder is mechanically cold pressed at 50 MPa for 1 hour to form a compact, then packed into a package and evacuated, and the vacuum degree is 10 ^-3 Pa; The pressure was 200MPa, the pressure was maintained for 4h, and the temperature was 1200℃. The dissolved solute atoms in the zirconium alloy matrix reacted and precipitated again to obtain Y-Ti-O and Y-Zr-O nano-oxide dispersion-reinforced zirconium alloys.

The crystal phase structure of the zirconium alloy in Example 2 was detected, and the crystal phase structure was similar to that in Example 1. After testing, the structures of Y-Ti-O and Y-Zr-O nano-oxides are Y ₂ Ti ₂ O ₇ and Y ₂ Zr ₂ O ₇ ; and the particle size of the precipitated phase is 2-10nm, and the number density can reach 1- 3×10 ¹⁵ /m ² .

Comparative Example 1

A zirconium alloy without introducing Y, Ti and O elements was prepared, the alloy composition was the same as that of the pre-alloy in Example 1, and the preparation process was the same as that of Example 1.

Comparative Example 2

A zirconium alloy added with 0.4wt% Y ₂ O ₃ alone was prepared, the alloy composition was the same as that of the pre-alloy in Example 1, and the preparation process was the same as that of Example 1.

Comparative Example 3

A zirconium alloy added with 0.4 wt% Y ₂ O ₃ and 0.4 wt % Ti was prepared, the alloy composition was the same as that of the pre-alloy in Example 1, and the preparation process was the same as that in Example 1.

Comparative Example 4

A zirconium alloy added with 0.4wt% Y and 0.4wt% Ti was prepared, the alloy composition was the same as that of the pre-alloy in Example 1, and the preparation process was the same as that in Example 1.

Comparative Example 5

A zirconium alloy added with 0.4wt% Y and 0.4wt% _TiO2 was prepared, the alloy composition was the same as that of the pre-alloy in Example 1, and the preparation process was the same as that in Example 1.

Zirconium alloy performance test:

For the tensile test, the parallel section length is 30mm and the tensile test is carried out under the vacuum conditions of 25, 300, 400, 500 and 600 °C with a tensile speed of 0.15 mm/min. Please refer to FIG. 3 , which is a comparison diagram of the mechanical properties of the nano-oxide dispersion-reinforced heat-resistant zirconium alloy prepared in the embodiment of the present invention and the zirconium alloy prepared in the comparative example under different temperature conditions.

It can be seen from Figure 3 that the room temperature and high temperature yield strengths of the nano-oxide dispersion-reinforced zirconium alloys prepared in Examples 1 and 2 of the present invention are significantly better than those of the zirconium alloys without Y, Ti, O elements (Comparative Example 1), Zirconium alloy with only Y ₂ O ₃ added (Comparative example 2), Zirconium alloy with Y ₂ O ₃ and pure Ti added (Comparative example 3), Zirconium alloy with pure Y and pure Ti added (Comparative example 4) and pure Y added and TiO ₂ zirconium alloy (Comparative Example 5), indicating that the zirconium alloy provided by the present invention achieves excellent high strength and heat resistance.

In the present invention, the alloying elements Y and Ti are introduced in the form of hydride YH ₂ and oxide TiO ₂ , or in the form of hydride TiH ₂ and oxide Y ₂ O ₃ , compared to directly adding pure Y and pure Ti, and It is only added in the form of oxides, which is conducive to the crushing and refining of powder, uniform dispersion and sufficient redissolving of solutes in the subsequent high-energy ball milling process, and improves the effect of mechanical alloying; on the other hand, regulating the ratio of hydride and oxide, mechanical alloying During the chemical process, excess H and O combine to generate water, absorb part of the heat, and improve the efficiency of ball milling.

It should be noted that the zirconium alloy block in the present invention can be replaced with pure zirconium or other zirconium alloys, such as Zr-Nb, Zr-Sn-Nb and other series alloys.

The nano-oxide dispersion-enhanced heat-resistant zirconium alloy and the preparation method thereof provided by the present invention adopt pre-alloyed powder, Y-containing and Ti-containing powder fully mixed and high-energy ball milling to realize the mechanical alloying of the zirconium alloy powder; further through hot isostatic pressing To achieve complete densification, the density is greater than 99%, there is no macrosegregation of components, and the grains are uniform and fine;

The added Y- and Ti-containing powders are easy to be broken, refined and decomposed during the mechanical alloying process, and the solute elements are dissolved back into the matrix in the form of Y, Ti, O solid solution atoms to form a supersaturated solid solution. During the hot isostatic pressing process The solute atoms in the solid solution reacted and precipitated again to form Y-Ti-O and Y-Zr-O oxide precipitates with ultra-high number density, low nanoscale, and dispersed distribution, among which Y-Ti-O and Y-Zr The particle size of the -O nano-oxide precipitation phase is 2-10nm, and the number density is 1-3×10 ¹⁵ /m ² , which makes the nano-oxide precipitation phase have high thermal stability and corrosion resistance. A large number of boundary precipitations, strong ability to pin dislocations and grain boundaries at high temperatures, and can inhibit recrystallization of grains, thereby greatly improving the strength and heat resistance of zirconium alloys. The nano-oxide dispersion-reinforced heat-resistant zirconium alloy provided by the invention also has higher yield strength when the working temperature is increased to above 500 DEG C, and has excellent high-temperature mechanical properties.

The embodiments of the present invention have been described above in detail, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and alterations to these embodiments without departing from the principle and spirit of the present invention still fall within the protection scope of the present invention.

Claims (7)

1. A preparation method of a nanometer oxide dispersion reinforced heat-resistant zirconium alloy is characterized by comprising the following steps:

step S1, carrying out hydrogenation dehydrogenation treatment on the zirconium alloy block to obtain pre-alloy powder;

the zirconium alloy block comprises the following components in percentage by weight:

1.2 to 1.6 percent of Sn, 0.2 to 0.5 percent of Fe, 0.1 to 0.3 percent of Cr, and the balance of Zr and inevitable impurities;

step S2, putting powder materials containing Y, Ti and O elements and pre-alloyed powder into a high-speed pendulum vibration ball mill, and fully mixing under the protection of inert gas to obtain mixed powder;

step S3, carrying out high-energy ball milling on the mixed powder under the protection of inert gas, and dissolving solute elements back into the matrix in the form of Y, Ti and O solid solution atoms to form mechanical alloying powder with a structure exceeding that of a saturated solid solution;

step S4, cold pressing the mechanical alloying powder into a billet, filling the billet into a sheath, vacuumizing the sheath, densifying the billet, reacting and precipitating solute atoms dissolved in the zirconium alloy matrix again to form Y-Ti-O and Y-Zr-O nano oxide precipitated phases which are distributed in a dispersed way, wherein the structure of the nano oxide precipitated phase is Y ₂ Ti ₂ O ₇ And Y ₂ Zr ₂ O ₇ With a particle size of 2-10nm and a number density of 1-3X 10 ¹⁵ Per m ² 。

2. The method for preparing the nano-oxide dispersion-strengthened heat-resistant zirconium alloy as claimed in claim 1, wherein the temperatures of the hydrogenation and dehydrogenation processes in step S1 are 300-500 ℃ respectively;

the obtained prealloyed powder has a particle size of 5-20 μm and a hydrogen content of not more than 100 ppm.

3. The method of claim 1, wherein in step S2, the powder material containing Y, Ti and O elements is YH ₂ Powder and TiO ₂ Powder, Y ₂ O ₃ Powder and TiH ₂ Powder, Y ₂ O ₃ Powder and pure Ti powder, or pure Y powder and TiO ₂ One of the four combinations of powders;

wherein the average grain diameter of the powder material containing the Y element is 1-20 μm, the addition amount is 0.1-2% of the weight of the pre-alloyed powder, the average grain diameter of the powder material containing the Ti element is less than 1 μm, and the addition amount is 0.1-1% of the weight of the pre-alloyed powder.

4. The preparation method of the nano-oxide dispersion-reinforced heat-resistant zirconium alloy as claimed in claim 1, wherein in step S3, the mechanical alloying process adopts an omnibearing planetary ball mill, the disc surface rotation speed is 400-600rpm, the longitudinal rotation speed is 10-20rpm, the ball-material mass ratio is 10-20:1, and the ball milling time is 20-40 h; and stopping the ball mill for 2-3min and changing the positive and negative rotation directions after ball milling for 15-30 min.

5. The method for preparing a nano-oxide dispersion-strengthened heat-resistant zirconium alloy according to claim 1, wherein in step S4, the mechanically alloyed powder is cold-pressed into briquettes by a tablet press, the pressure is 20 to 40MPa, and the pressure is maintained for 1 hour; the sheath is vacuumized with the vacuum degree of 10 ^-3 Pa; adopting hot isostatic pressing for densification, wherein the hot isostatic pressing pressure is 150-200MPa, the pressure is maintained for 4-6h, and the temperature is 1100-1300 ℃.

6. The method for preparing the nano-oxide dispersion-strengthened heat-resistant zirconium alloy as claimed in claim 5, wherein the cold pressing mode is replaced by a cold isostatic pressing mode, and the hot isostatic pressing densification mode is replaced by a hot extrusion or spark plasma sintering mode.

7. The nano-oxide dispersion-strengthened heat-resistant zirconium alloy prepared by the preparation method of the nano-oxide dispersion-strengthened heat-resistant zirconium alloy according to any one of claims 1 to 6, which is characterized by comprising a zirconium alloy matrix and Y-Ti-O and Y-Zr-O nano-oxide precipitated phases dispersed in the zirconium alloy matrix, wherein the Y-Ti-O and Y-Zr-O nano-oxide precipitated phases have a structure of Y ₂ Ti ₂ O ₇ And Y ₂ Zr ₂ O ₇ With a particle size of 2-10nm and a number density of 1-3X 10 ¹⁵ Per m ² 。

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