CN111593221A - Preparation method of high-performance molybdenum-scandium alloy and high-performance molybdenum-scandium alloy - Google Patents

Abstract

The invention discloses a preparation method of a high-performance molybdenum-scandium alloy and a high-performance molybdenum-scandium alloy. The method includes five steps of designing material composition, mixing, grinding, filling powder, and pressing and burning. Compared with other rare earth oxides, the second phase in the present invention has a good strengthening effect, can more effectively improve the hardness of the molybdenum alloy, and at the same time effectively reduce the friction loss of the alloy at room temperature; the present invention uses SPS sintering, which can improve sintering efficiency, reducing the sintering time and sintering temperature, reducing the time for the growth of molybdenum grains to a certain extent, and further refining the grains; the Mo-Sc ₂ O ₃ alloy prepared by the method of the present invention is at room temperature Its hardness is improved. The present invention prepares the molybdenum-scandium alloy which is superior to pure molybdenum alloy in strength and high-temperature wear-reducing property on the basis of using SPS technology.

Description

A kind of preparation method of high-performance molybdenum-scandium alloy and high-performance molybdenum-scandium alloy

technical field

The invention relates to the technical field of molybdenum alloy materials, in particular to a preparation method of a molybdenum-scandium alloy and a high-performance molybdenum-scandium alloy.

Background technique

Molybdenum is an important non-renewable strategic resource. It has the characteristics of high melting point, high high temperature strength, small thermal expansion coefficient, good thermal conductivity and thermal shock resistance, and thermal fatigue. Molybdenum products are widely used in steel, non-ferrous metals, petroleum, chemical, electronics, national defense, aerospace, nuclear industry and other fields. However, molybdenum metal has the characteristics of low temperature brittleness and ductile-brittle transition inherent in body-centered cubic metal, which limits its wider use as a structural material. Alloying can effectively improve the properties of molybdenum-based materials, but high temperature will promote the growth of molybdenum alloy grains. The traditional preparation method is difficult to obtain fine-grained molybdenum alloy due to the complicated process and long sintering time. This method The prepared molybdenum alloy has greater brittleness and lower hardness, and the doped second phase is also relatively coarse, which further reduces the performance of the alloy.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a preparation method of a molybdenum-scandium alloy with high strength and good performance and a molybdenum-scandium alloy.

For achieving the above object, the technical scheme provided by the invention is as follows:

A preparation method of a high-performance molybdenum-scandium alloy, comprising the following steps:

(1) Design material composition: in terms of mass fraction percentage, the materials used include 97%-99.5% Mo and 0.5%-3% Sc ₂ O ₃ ;

(2) Mixing: According to the material composition of step (1), the components are mixed to obtain mixed powder; the microstructure of the mixed powder is nearly spherical, the average particle size is 3-5 μm, Mo powder and Sc ₂ O ₃ The mass ratio is (97～99.5):(0.5～3.0);

(3) grinding: the mixed powder obtained in step (2) is ground, and the grinding time is 3-7 hours, and a protective atmosphere is filled simultaneously;

(4) Powder filling: The powder is formed by a set of graphite molds. The mold is composed of graphite and has no other impurities. It includes an upper indenter, a lower indenter and a hollow female mold with a temperature measuring hole. The upper indenter and The structure of the lower pressure head is the same, both of which are columnar structure, the graphite female mold is a sleeve-shaped hollow structure, and a temperature measuring hole is opened on the side wall of the graphite female mold; graphite sheet, then the mixed powder obtained in step (3) is filled on the lower indenter in the interior of the female mold, and the graphite sheet is also placed, and then the upper indenter is inserted into the inner hole from above the female mold, and the upper indenter is passed through the upper indenter. and the lower pressure head to compress the mixed metal powder;

(5) pressure sintering: the mould to be sintered obtained in step (4) is placed in the hearth of the spark plasma sintering system, and the air in the furnace is extracted to a vacuum state; then, the pressure system is adjusted so that the indenter maintains a constant pressure to the mould; Then, the metal powder is sintered by passing an electric current to obtain a Mo-Sc ₂ O ₃ alloy.

Further, the upper indenter and the lower indenter are both cylindrical structures with a diameter of 30mm and a height of 35mm, the graphite female mold is a sleeve-shaped hollow structure with an outer diameter of 60mm, an inner diameter of 30mm and a height of 50mm, and the graphite female mold is in the middle. A temperature measuring hole with a diameter of 4 mm and a depth of 5 mm is opened at the height position, and the graphite sheet is a graphite circular sheet with a diameter of 30 mm.

Further, the ball-to-material ratio is 10:1 during grinding, the ball milling speed is 200-300r/min, and the forward and reverse ball milling is performed.

Furthermore, absolute ethanol is added during the grinding process.

Further, the graphite mold and the graphite disc have the same composition and do not contain other impurities.

Further, before sintering, the inside of the sintering furnace is closed and evacuated to a degree of vacuum less than 1.0×10 ^-1 Pa, the set mechanical pressure is 30MPa, the sintering temperature is 1400 ℃ ~ 1500 ℃, the preferred temperature is 1400 ℃, the temperature rises and cools down. The rate is 110-125°C/min.

Further, the sintering temperature is 1400°C.

A high-performance molybdenum-scandium alloy is a Mo-Sc ₂ O ₃ alloy obtained according to the above-mentioned preparation method.

The beneficial effects of the present invention are as follows:

(1) Compared with other rare earth oxides, the second phase in the present invention has a better strengthening effect, can more effectively improve the hardness of the molybdenum alloy, and at the same time effectively reduce the friction loss of the alloy at room temperature.

(2) SPS sintering is used in the present invention, which can improve sintering efficiency, reduce sintering time and sintering temperature, reduce the growth time of molybdenum grains to a certain extent, and further refine grains.

(3) The hardness of the Mo-Sc ₂ O ₃ alloy prepared by the method of the present invention is improved at room temperature.

Description of drawings

Fig. 1 is the sintering process flow chart of the present invention;

Fig. 2 is the sintering process curve diagram of the present invention;

3 is the scanning electron microscope images of Example 1, Example 2, Example 3, and Example 4.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings.

The preparation method of the high-performance molybdenum-scandium alloy of the present invention is shown in Figure 1, and the specific preparation steps are as follows:

(1) Design material composition: in terms of mass fraction percentage, the materials used include 97%-99.5% Mo and 0.5%-3% Sc ₂ O ₃ ;

(2) Mixing: According to the material composition of step (1), the components are mixed to obtain mixed powder; the microstructures of Mo powder and Sc ₂ O ₃ powder are all spherical, with an average size of 3-5 μm, Mo powder The mass ratio to Sc ₂ O ₃ is (97～99.5):(0.5～3.0);

(3) Grinding: the mixed powder obtained in the step (2) is mechanically ground in a mechanical grinding device, and the grinding time is 3-7 hours. At the same time, in order to prevent impurities in the air, argon is filled as a protective atmosphere during grinding, A little anhydrous ethanol is added during the grinding process to prevent the powder from sticking to the wall; the mechanical grinding process can make the two powders evenly dispersed, which is beneficial to subsequent sintering, and at the same time, argon gas is used to protect the powder from mixing other impurities during ball milling; the ball-to-material ratio during grinding is 10:1, ball milling speed is 200-300r/min, positive and negative ball milling;

(4) Filling powder: In the present invention, powder forming is fixed by a set of graphite molds, and the mold includes an upper indenter, a lower indenter and a hollow female mold with a temperature measuring hole, and the structure of the upper indenter and the lower indenter The same, they are all cylindrical structures with a diameter of 30mm and a height of 35mm. The graphite die is a sleeve-shaped hollow structure with an outer diameter of 60mm, an inner diameter of 30mm and a height of 50mm. The graphite die has a temperature measurement with a diameter of 4mm and a depth of 5mm at the middle height. hole. Insert the lower indenter into a part of the inner hole of the female mold, and put 1 to 2 graphite discs with a diameter of 30mm to prevent the indenter from being damaged during the sintering process, and then fill the mixed powder obtained in step (3) into the female mold. Also put 1-2 graphite discs with a diameter of 30mm on the lower indenter in the interior, and then insert the upper indenter into the inner hole from above the female mold, and press the mixed metal powder through the upper indenter and the lower indenter. The graphite mold is specially made for SPS sintering in the present invention, and its main component is graphite, and there are no other impurities; the graphite disc is composed of graphite and has no other impurities. The indenter is bonded;

(5) Press sintering: put the mold to be sintered obtained in step (4) into the furnace chamber of the spark plasma sintering system, and extract the air in the furnace to a vacuum state, so as to prevent the molybdenum powder from being oxidized during the sintering process during sintering on the one hand, On the other hand, it can promote the removal of the gas generated in the sintering process and promote the sintering and densification process. Next, adjust the pressure system so that the indenter maintains a constant pressure on the mold to promote powder forming, and then sinter the metal powder with an electric current. The sintering process curve is shown in Figure 2, and the Mo-Sc ₂ O ₃ alloy is obtained. Before sintering, the interior of the sintering furnace is closed and evacuated to a degree of vacuum less than 1.0×10 ^{- 1} Pa, the set mechanical pressure is 30MPa, the sintering temperature is 1400℃～1500℃, the preferred temperature is 1400℃, and the heating and cooling rate is 110- 125°C/min. In the above sintering process, a smaller vacuum degree can avoid the influence of elements in the air, especially oxygen elements, on sintering, and a larger sintering pressure and a lower sintering temperature can ensure higher sintering performance.

The invention can sinter quickly through the spark plasma sintering (SPS) method, avoids the growth of molybdenum grains during sintering, and can prepare molybdenum-scandium alloy at a lower sintering temperature. In the sintering process, the fine spherical Sc ₂ O ₃ can be _The grain boundary migration of molybdenum grains is effectively organized, the grains are refined, and the grain boundaries are purified at the same time, which hinders the movement _of dislocations, and plays a pinning role. Reduces the possibility of alloy cracking at grain boundaries.

In this explanation, the friction and wear experiment given in the following examples, the experimental process is: to the alumina ball of 6.5mm, the reciprocating friction and wear form is used to carry out the friction and wear experiment on the alloy, and its test process conditions are: The test load is 10N, the single stroke is 5mm, the friction time is 30min, and the experiment is carried out at room temperature.

Example 1

The molybdenum-scandium alloy in this embodiment has chemical components and mass percentages as follows: Mo: 99.5%, Sc ₂ O ₃ : 0.5%.

1. Pretreatment Mo powder and Sc ₂ O ₃ powder are prepared according to the mass ratio of 99.5:0.5. Mix in a planetary ball mill with a ball-to-material ratio of 10:1, grind for 5 hours, and add a little anhydrous ethanol during grinding to prevent the powder from sticking to the wall;

2. Mold making Take a graphite mold, fill 1-2 graphite discs with a diameter of 30mm, put the treated Mo-Sc ₂ O ₃ alloy powder into the graphite mold from bottom to top, and fill 1-2 pieces of graphite with a diameter of 30mm The disc is then pressed with the upper indenter and the lower indenter to prevent powder leakage;

3. Sintering Put the graphite mold to be sintered in the furnace of the spark plasma sintering system, evacuate it to no higher than 1.0×10 ^-1 Pa, and then pass in a DC pulse current to sinter the Mo-Sc ₂ O ₃ alloy powder. The bonding and sintering process is as follows: the axial pressure of the upper indenter and the lower indenter on the iron base and the metal powder is 30MPa; the heating rate is: from room temperature to 900°C, 110°C/min, and 900°C to sintering temperature of 125°C ℃/min; the holding time is 6min; the cooling rate is: the cooling rate from the sintering temperature to 600 ℃ is 115 ℃/min, and the range from 600 ℃ to room temperature is cooled with the furnace; after cooling, molybdenum was successfully obtained Scandium alloy, the hardness of the alloy is better.

Example 2

The molybdenum-scandium alloy in this embodiment has the chemical composition and its mass percentage as follows: Mo: 99%, Sc ₂ O ₃ : 1.0%.

1. Pretreatment Mo powder and Sc ₂ O ₃ powder are prepared according to the mass ratio of 99:1. Mix in a planetary ball mill with a ball-to-material ratio of 10:1, grind for 5 hours, and add a little anhydrous ethanol during grinding to prevent the powder from sticking to the wall;

2. Mold making Take a graphite mold, fill 1-2 graphite discs with a diameter of 30mm, put the treated Mo-Sc ₂ O ₃ alloy powder into the graphite mold from bottom to top, and fill 1-2 pieces of graphite with a diameter of 30mm The disc is then pressed with the upper indenter and the lower indenter to prevent powder leakage;

3. Sintering Put the graphite mold to be sintered in the furnace of the spark plasma sintering system, evacuate it to no higher than 1.0×10 ^-1 Pa, and then pass in a DC pulse current to sinter the Mo-Sc ₂ O ₃ alloy powder. The bonding and sintering process is as follows: the axial pressure of the upper indenter and the lower indenter on the iron base and the metal powder is 30MPa; the heating rate is: from room temperature to 900°C, 110°C/min, and 900°C to sintering temperature of 125°C ℃/min; the holding time is 6min; the cooling rate is: the cooling rate from the sintering temperature to 600 ℃ is 115 ℃/min, and the range from 600 ℃ to room temperature is cooled with the furnace; after cooling, molybdenum was successfully obtained Scandium alloy, the hardness of the alloy is better.

Example 3

The molybdenum-scandium alloy in this embodiment has chemical components and mass percentages as follows: Mo: 98.5%, Sc ₂ O ₃ : 1.5%.

1. Pretreatment Mo powder and Sc ₂ O ₃ powder are prepared according to the mass ratio of 98.5:1.5. Mix in a planetary ball mill at a ratio of 10:1 to the balls, grind for 5 hours, and add a little anhydrous ethanol during grinding to prevent the powder from sticking to the wall;

2. Mold making Take a graphite mold, fill 1-2 graphite discs with a diameter of 30mm, put the treated Mo-Sc ₂ O ₃ alloy powder into the graphite mold from bottom to top, and fill 1-2 pieces of graphite with a diameter of 30mm The disc is then pressed with the upper indenter and the lower indenter to prevent powder leakage;

3. Sintering Put the graphite mold to be sintered in the furnace of the spark plasma sintering system, evacuate it to no higher than 1.0×10 ^-1 Pa, and then pass in a DC pulse current to sinter the Mo-Sc ₂ O ₃ alloy powder. The bonding and sintering process is as follows: the axial pressure of the upper indenter and the lower indenter on the iron base and the metal powder is 30MPa; the heating rate is: from room temperature to 900°C, 110°C/min, and 900°C to sintering temperature of 125°C ℃/min; the holding time is 6min; the cooling rate is: the cooling rate from the sintering temperature to 600 ℃ is 115 ℃/min, and the range from 600 ℃ to room temperature is cooled with the furnace; after cooling, molybdenum was successfully obtained Scandium alloy, the hardness of the alloy is better.

Example 4

The molybdenum-scandium alloy in this embodiment has the chemical composition and its mass percentage as follows: Mo: 97%, Sc ₂ O ₃ : 3.0%.

1. Pretreatment Mo powder and Sc ₂ O ₃ powder are proportioned according to the mass ratio of 97:3. Mix in a planetary ball mill at a ratio of 10:1 to the balls, grind for 5 hours, and add a little anhydrous ethanol during grinding to prevent the powder from sticking to the wall;

2. Mold making Take a graphite mold, fill 1-2 graphite discs with a diameter of 30mm, put the treated Mo-Sc ₂ O ₃ alloy powder into the graphite mold from bottom to top, and fill 1-2 pieces of graphite with a diameter of 30mm The disc is then pressed with the upper indenter and the lower indenter to prevent powder leakage;

3. Sintering Put the graphite mold to be sintered in the furnace of the spark plasma sintering system, evacuate it to no higher than 1.0×10 ^-1 Pa, and then pass in a DC pulse current to sinter the Mo-Sc ₂ O ₃ alloy powder. The bonding and sintering process is as follows: the axial pressure of the upper indenter and the lower indenter on the iron base and the metal powder is 30MPa; the heating rate is: from room temperature to 900°C, 110°C/min, and 900°C to sintering temperature of 125°C ℃/min; the holding time is 6min; the cooling rate is: the cooling rate from the sintering temperature to 600 ℃ is 115 ℃/min, and the range from 600 ℃ to room temperature is cooled with the furnace; after cooling, molybdenum was successfully obtained Scandium alloy, the hardness of the alloy is better.

The SEM images of Example 1, Example 2, Example 3, and Example 4 are shown in Figure 3, and the relevant parameters are shown in the following table.

Table 1 The implementation parameters of each

Average grain size/μm Relative density/% Vickers hardness/HV Room temperature friction coefficient Example 1 2.23 96.7 349.7 0.434 Example 2 1.68 97 358.9 0.327 Example 3 1.72 97.3 360.6 0.318 Example 4 2.56 97.5 374.1 0.490

To sum up, the preparation method of the high-performance molybdenum-scandium alloy of the present invention prepares the molybdenum-scandium alloy whose strength and high-temperature wear reduction are better than those of pure molybdenum alloy on the basis of using SPS technology. The description of the preferred embodiments of the invention is not intended to limit the concept and scope of the present invention. On the premise of not departing from the design concept of the present invention, various modifications and improvements made by engineers and technicians in the field to the technical solutions of the present invention should all fall within the scope of the present invention. protection scope of the present invention.

Claims (8)

1. a preparation method of a high-performance molybdenum-scandium alloy, comprising the following steps: (1) Design material composition: in terms of mass fraction percentage, the materials used include 97%-99.5% Mo and 0.5%-3% Sc ₂ O ₃ ; (2) Mixing: According to the material composition of step (1), the components are mixed to obtain mixed powder; the microstructure of the mixed powder is nearly spherical, the average particle size is 3-5 μm, and the mass ratio of Mo powder to Sc2O3 is (97～99.5):(0.5～3.0); (3) grinding: the mixed powder obtained in step (2) is ground, and the grinding time is 3-7 hours, and a protective atmosphere is filled simultaneously; (4) Powder filling: The powder is formed by a set of graphite molds. The mold is composed of graphite and has no other impurities. It includes an upper indenter, a lower indenter and a hollow female mold with a temperature measuring hole. The upper indenter and The structure of the lower pressure head is the same, both of which are columnar structure, the graphite female mold is a sleeve-shaped hollow structure, and a temperature measuring hole is opened on the side wall of the graphite female mold; graphite sheet, then the mixed powder obtained in step (3) is filled on the lower indenter in the interior of the female mold, and the graphite sheet is also placed, and then the upper indenter is inserted into the inner hole from above the female mold, and the upper indenter is passed through the upper indenter. and the lower pressure head to compress the mixed metal powder; (5) pressure sintering: the mould to be sintered obtained in step (4) is placed in the hearth of the spark plasma sintering system, and the air in the furnace is extracted to a vacuum state; then, the pressure system is adjusted so that the indenter maintains a constant pressure to the mould; Then, the metal powder is sintered by passing an electric current to obtain a Mo-Sc ₂ O ₃ alloy. 2. the preparation method of high-performance molybdenum-scandium alloy according to claim 1, is characterized in that, described upper indenter and lower indenter are the cylindrical structure of diameter 30mm, height 35mm, and graphite female mold is outer diameter 60mm , a sleeve-shaped hollow structure with an inner diameter of 30mm and a height of 50mm, the graphite female mold is provided with a temperature measuring hole with a diameter of 4mm and a depth of 5mm at the middle height position, and the graphite sheet is a graphite disc with a diameter of 30mm. 3 . The preparation method of high-performance molybdenum-scandium alloy according to claim 1 , wherein the ball-to-material ratio is 10:1 during grinding, the ball milling speed is 200-300 r/min, and the forward and reverse ball milling is performed alternately. 4 . 4. The preparation method of high-performance molybdenum-scandium alloy according to claim 1, wherein absolute ethanol is added in the grinding process. 5. The preparation method of high-performance molybdenum-scandium alloy according to claim 1, wherein the graphite mold and the graphite disc have the same composition and do not contain other impurities. 6. The preparation method of high-performance molybdenum-scandium alloy according to claim 1, characterized in that, before sintering, the interior of the sintering furnace is closed and evacuated to a degree of vacuum less than 1.0×10 ^-1 Pa, and the set mechanical pressure is 30MPa , the sintering temperature is 1400°C to 1500°C, the preferred temperature is 1400°C, and the heating and cooling rate is 110-125°C/min. 7 . The method for preparing a high-performance molybdenum-scandium alloy according to claim 1 , wherein the sintering temperature is 1400° C. 8 . 8 . A high-performance molybdenum-scandium alloy, characterized in that it is a Mo-Sc ₂ O ₃ alloy obtained by the preparation method according to any one of claims 1-7.

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