Preparation process of high-strength heat-resistant magnesium alloy

Abstract

The invention relates to the technical field of magnesium alloy materials, in particular to a preparation process of a high-strength heat-resistant magnesium alloy, which comprises the following steps: electrolyzing to prepare a copper-cerium intermediate alloy; preparing a high-conductivity magnesium alloy casting rod; and pulse current treatment is conducted in the casting rod forging process. According to the method, pulse current treatment is conducted in the forging process, generation of a brittle phase beta-Mg17Al12 in the forging process of the alloy can be greatly inhibited, phase spheroidization of the beta-Mg17Al12 is promoted, stress concentration at the grain boundary is reduced, under the action of the pulse current, in cooperation with the forging process, temperature distribution in the alloy can be more uniform, and the alloy quality is improved. Atomic diffusion and grain migration are more active, cracks and air holes generated in the forging process are reduced, the forging quality is improved, and therefore the strength of the magnesium alloy is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium alloy materials, and in particular to a preparation process of a high-strength and heat-resistant magnesium alloy. Background Art

[0002] With the increasing advancement of green and sustainable development, magnesium alloys have become a lightweight structural material with great potential in the fields of aerospace, automobiles and electronics due to their significant advantages such as low density, high specific strength and excellent damping and shock absorption performance. However, the performance of magnesium alloys in high temperature environments is restricted. Specifically, magnesium alloys have low high temperature strength and poor high temperature creep resistance, which greatly limits their application in fields such as aerospace, automobiles and national defense that require high strength and high temperature resistance. In order to overcome the insufficient high temperature performance of magnesium alloys, magnesium rare earth alloys have become the focus of research. Studies have found that by adding rare earth elements such as cerium and neodymium to magnesium alloys, the solid solution strengthening and precipitation strengthening effects of rare earth elements can be used to improve the room temperature and high temperature mechanical properties of the alloy.

[0003] Many researchers have proposed different alloy designs and preparation processes for the technical point of adding rare earth elements. For example, adding a large amount of rare earth elements to magnesium alloys to make the content of rare earth elements ≥10% to improve the mechanical properties of magnesium alloys. However, adding a large amount of rare earth elements to magnesium alloys will cause serious high production costs and poor substitutability. In addition, as the temperature increases, the second phase in the magnesium rare earth alloy will coarsen, grow or dissolve, resulting in a significant decrease in the strength of the material, which is not suitable for large-scale industrial production and application. For another example, adding a variety of trace rare earth elements to achieve microalloying, and then regulating the type, size, distribution and quantity of the second phase in the magnesium alloy through multi-directional forging to improve the heat resistance of the magnesium alloy. The disadvantage is that due to the large number of added elements, it is difficult to accurately control and it is impossible to take into account the mechanical properties. Therefore, developing a magnesium alloy that can maintain good mechanical properties at high temperatures and has strong high-temperature durability has become a technical challenge that needs to be solved urgently. Summary of the invention

[0004] In order to solve the above technical defects, the present invention has developed a preparation process of a high-strength heat-resistant magnesium alloy. The prepared magnesium alloy not only has excellent mechanical properties but also has excellent heat resistance stability.

[0005] A preparation process of a high-strength heat-resistant magnesium alloy comprises the following steps: S1: Electrolytic preparation of copper-cerium master alloy NaCl, KCl and CeCl 3Placing it in a graphite crucible to melt into molten salt, then inserting a copper rod into the molten salt as a cathode, using the graphite crucible as an anode for electrolysis, collecting the copper-cerium alloy liquid produced by electrolysis and casting it into a copper-cerium alloy ingot, and crushing it to obtain copper-cerium intermediate alloy particles; S2: Preparation of high conductivity magnesium alloy casting rods Will After the alloy is melted, copper-cerium master alloy particles are added, and the stirring and heat preservation operation is repeated under a protective atmosphere, and then cast into The alloy ingot is subjected to high-energy ball milling to obtain nano master alloy powder, pure magnesium is melted, and then the nano master alloy powder and pure Sn are added in sequence, stirred under a protective atmosphere, and then kept warm, and then poured into a mold to obtain a high-conductivity magnesium alloy cast rod; S3: Pulse current treatment during forging of cast rods The high-conductivity magnesium alloy cast rod is preheated and then fixed between the upper and lower cast iron anvils of a forging machine. The positive pole of a pulse power supply is connected to the lower cast iron anvil of the forging machine, and the negative pole is connected to the preheated high-conductivity magnesium alloy cast rod. After power is turned on, forging is performed to obtain a magnesium alloy forging. The magnesium alloy forging is subjected to aging treatment to obtain a high-strength and heat-resistant magnesium alloy.

[0006] Furthermore, step S1 electrolytically preparing a copper-cerium master alloy comprises the following steps: S11: Place a tungsten crucible at the center of the bottom of the graphite crucible. The radius ratio of the tungsten crucible to the graphite crucible is 1:2-3 and the tungsten crucible and the graphite crucible are insulated. 3 The mixture is placed in a graphite crucible with a mass ratio of 1:0.2-0.6:0.8-1 and buried in the tungsten crucible. The graphite crucible is then placed in a resistance furnace and heated at a temperature of 1000-1050°C until NaCl, KCl and CeCl 3 Melt to obtain molten salt, including NaCl, KCl, CeCl 3 The purity is above 99.9%; S12: Insert the copper rod from the top of the tungsten crucible into the molten salt prepared in S11, use the copper rod as the cathode and the graphite crucible as the anode for electrolysis, and set the current density of electrolysis to 10-15A / cm 2 The copper rod generates copper-cerium alloy liquid and flows into the tungsten crucible until the tungsten crucible is filled with copper-cerium alloy liquid. The tungsten crucible is taken out and the copper-cerium alloy liquid in the tungsten crucible is placed in a mold and cast into a copper-cerium alloy ingot, which is broken into copper-cerium intermediate alloy particles with a particle size of 0.5-1 cm.

[0007] Furthermore, step S2 of preparing the high-conductivity magnesium alloy cast rod comprises the following steps: S21: 20-30 parts by mass of The alloy is placed in a tungsten crucible and then sent into a resistance furnace. The temperature of the resistance furnace is adjusted to 900-950℃. When the alloy is completely melted, add 4-6 parts by mass of copper-cerium master alloy particles and continue to introduce protective gas, stir for 4-5 minutes and keep warm for 6-8 minutes, repeat this stirring and keeping warm operation 4-5 times and then place in a mold and cast into The alloy ingot is crushed and placed in a high-energy ball mill, and nitrogen is introduced. The high-energy ball mill is performed at a speed of 500-600r / min for 40-48 hours in a nitrogen atmosphere to obtain a nano master alloy powder, wherein the high-energy grinding balls and The ball-to-material ratio of the alloy ingot is 1:0.3-0.4; S22: 120-150 parts by mass of pure magnesium are placed in a tungsten crucible and then introduced into a resistance furnace, the temperature is set to 800-850°C, and a protective gas is introduced into the resistance furnace. When the pure magnesium is completely melted, the resistance furnace is powered off, and the nano intermediate alloy powder prepared in step S21 and 2-3 parts by mass of pure Sn are sequentially added to the pure magnesium melt. While continuously introducing a protective gas into the pure magnesium melt, the mixture is rapidly stirred at a stirring speed of 150-200 r / min for 5-8 minutes. The resistance furnace is opened and kept warm at a temperature of 800-850°C for 15-20 minutes to obtain a magnesium alloy melt, and the magnesium alloy melt is poured into a mold to be cooled and solidified to obtain a high-conductivity magnesium alloy cast rod.

[0008] Furthermore, the pulse current treatment during the forging process of the cast rod in step S3 includes the following steps: S31: Place the high-conductivity magnesium alloy cast rod in a resistance furnace, set the holding temperature to 450-500°C, and keep it warm for 10-12 hours to obtain a preheated magnesium alloy cast rod. Preheat the upper and lower cast iron anvils of the forging machine to 200-250°C, place the preheated magnesium alloy cast rod between the upper and lower cast iron anvils for fixing, and then connect the positive electrode of the pulse power supply to the lower cast iron anvil, and the negative electrode to the preheated magnesium alloy cast rod. Set the current density to 3×10 6 -4×10 6 A.m -2 Forging is performed; S32: During the upsetting and drawing process of forging, the direction is changed 1-3 times each time the upsetting and drawing is performed, the pressing speed of forging is set to 10-20 mm / s, the turning angle of the forging blank is 90° each time the direction is changed, the first upsetting reduction rate is 45-50%, the remaining upsetting single-pass reduction rate is 30-40%, the drawing single-pass reduction rate is 10-20%, the total forging passes are 32-40 passes, and the magnesium alloy forgings are obtained. The magnesium alloy forgings are placed in a resistance furnace for aging treatment to obtain a high-strength heat-resistant magnesium alloy.

[0009] Furthermore, in step S12, the depth of the copper rod inserted into the molten salt is 2 / 3-3 / 4 of the length of the copper rod.

[0010] Furthermore, in step S21 In alloy The mass fraction ratio of Y is 1:0.25-0.3, and the particle size of the nano master alloy powder is 200-500nm.

[0011] Furthermore, the protective gas in step S2 is CO 2 and SF 6 A mixed gas consisting of CO 2 and SF 6 The volume ratio is 1:98-99.

[0012] Furthermore, in step S32, the temperature of the aging treatment of the magnesium alloy forging is 200-250° C., and the time is 15-25 hours.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention preheats the high-conductivity magnesium alloy cast rod and places it between the upper and lower cast iron anvil plates of the forging machine and then fixes it, connects the positive electrode of the pulse power supply to the lower cast iron anvil plate of the forging machine, and connects the negative electrode to the preheated high-conductivity magnesium alloy cast rod to form a power-on circuit, and performs pulse current processing during the forging process, which can not only accelerate the diffusion process of atoms in the alloy, increase the migration rate of grain boundaries, and further refine the grain structure of the high-conductivity magnesium alloy cast rod, thereby enhancing the mechanical properties of the magnesium alloy, but also can greatly inhibit the brittle phase of the alloy during the forging process. The generation of Phase spheroidization reduces stress concentration at the grain boundaries, and under the action of pulse current, combined with the forging process of the present invention, the temperature distribution in the alloy can be more uniform, atomic diffusion and grain migration can be more active, which helps to reduce cracks and pores in the forging process and improve the forging quality, thereby greatly improving the strength and thermal stability of the magnesium alloy.

[0014] 2. The present invention is achieved by After the alloy is melted, copper-cerium master alloy particles are added, and the stirring and heat preservation operation is repeated under a protective atmosphere, and then cast into The alloy ingot is subjected to high-energy ball milling to obtain nano master alloy powder, and then pure magnesium is melted and the nano master alloy powder and pure Sn are added in sequence, and high-conductivity magnesium alloy casting rods are obtained after casting. Alloy melting can not only make the copper-cerium master alloy particles better soluble in the pure magnesium melt, but also form second phase particles in the alloy ingot, hindering The addition of copper-cerium can not only strengthen the lattice of magnesium alloy by solid solution and improve the thermal stability, but also provide good electrical conductivity for magnesium alloy casting rods, improve the subsequent pulse current forging effect, and further enhance the strength and thermal stability of magnesium alloy.

[0015] 3. The present invention uses copper as the cathode and the graphite crucible as the anode to perform molten salt electrolysis of Ce, which has a simple process and low production cost, and the prepared copper-cerium intermediate alloy particles have few impurities, which can improve the bonding strength and uniformity of the copper-cerium intermediate alloy particles, thereby enhancing the subsequent stability and dispersibility in high-conductivity magnesium alloy cast rods, which is beneficial to improving the subsequent pulse current forging effect and further enhancing the strength and thermal stability of the magnesium alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a process flow chart for preparing the high-strength and heat-resistant magnesium alloy used in the embodiments of the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Example 1 A preparation process of a high-strength heat-resistant magnesium alloy, such as Figure 1 As shown, the following steps are included: S1: Electrolytic preparation of copper-cerium master alloy S11: Place a tungsten crucible at the center of the bottom of the graphite crucible. The radius ratio of the tungsten crucible to the graphite crucible is 1:2.5 and the tungsten crucible and the graphite crucible are insulated. 3 The mixture was placed in a graphite crucible with a mass ratio of 1:0.4:0.9 and buried in the tungsten crucible. The graphite crucible was then placed in a resistance furnace and heated at 1020°C until NaCl, KCl and CeCl 3 Melt to obtain molten salt, including NaCl, KCl, CeCl 3 The purity is above 99.9%; S12: Insert the copper rod into the molten salt prepared in S11 from just above the tungsten crucible. The depth of the copper rod inserted into the molten salt is 3 / 4 of the length of the copper rod. Use the copper rod as the cathode and the graphite crucible as the anode for electrolysis. Set the current density of the electrolysis to 12A / cm 2The copper rod generates copper-cerium alloy liquid and flows into the tungsten crucible until the tungsten crucible is filled with copper-cerium alloy liquid. The tungsten crucible is taken out and the copper-cerium alloy liquid in the tungsten crucible is placed in a mold and cast into a copper-cerium alloy ingot, which is broken into copper-cerium intermediate alloy particles with a particle size of 0.8 cm.

[0019] It should be noted that before electrolysis, the tungsten crucible will be submerged in molten salt, but after electrolysis, since the density of the copper-cerium alloy liquid is greater than the density of the molten salt, the copper-cerium alloy liquid flowing into the tungsten crucible will gradually squeeze out the molten salt, so that the tungsten crucible will eventually be filled with only copper-cerium alloy liquid but no molten salt.

[0020] S2: Preparation of high conductivity magnesium alloy casting rods S21: 25 parts by mass of The alloy is placed in a tungsten crucible. In alloy The mass fraction ratio of Y is 1:0.28, and then it is sent into the resistance furnace, and the temperature of the resistance furnace is adjusted to 925℃. When the alloy is completely melted, add 5 parts by mass of copper-cerium master alloy particles and continue to introduce protective gas. Stir for 4.5 minutes and keep warm for 7 minutes. Repeat this stirring and keeping warm operation 4 times and then place in a mold and cast into The alloy ingot was crushed and placed in a high-energy ball mill, and nitrogen was introduced. High-energy ball milling was performed at a speed of 550 r / min for 45 hours under a nitrogen atmosphere to obtain a nano master alloy powder with a particle size of 400 nm, wherein the high-energy grinding balls and The ball-to-material ratio of the alloy ingot is 1:0.3, and the protective gas is CO 2 and SF 6 The mixed gas composed of CO 2 and SF 6 The volume ratio is 1:98; S22: 135 parts by mass of pure magnesium are placed in a tungsten crucible and then sent into a resistance furnace, the temperature is set to 820°C, and a protective gas is introduced into the resistance furnace. When the pure magnesium is completely melted, the resistance furnace is powered off, and the nano master alloy powder obtained in step S21 and 2.5 parts by mass of pure Sn are added to the pure magnesium melt in sequence. While the protective gas is continuously introduced into the pure magnesium melt, the mixture is rapidly stirred at a stirring speed of 180 r / min for 6 minutes, the resistance furnace is turned on and kept warm at 825°C for 18 minutes to obtain a magnesium alloy melt, and the magnesium alloy melt is poured into a mold to be cooled and solidified to obtain a high-conductivity magnesium alloy cast rod, wherein the protective gas is CO 2 and SF 6 The mixed gas composed of CO 2 and SF 6 The volume ratio is 1:98.

[0021] It should be noted that high-energy ball mills have a variety of models, each of which is designed for a specific scale of alloy grinding tasks. However, given that the current factory is only equipped with a limited number of high-energy ball mills, the present application is for the casting in step S21. The alloy ingots are crushed to ensure that they can fit into the existing ball mill models of the enterprise. It should be emphasized that this crushing process is based on the limitations of the factory equipment. If the enterprise has a high-energy ball mill that can handle the grinding of ultra-large volume alloys, then for the cast in step S21 Alloy ingots do not need to be crushed and can be directly put into the grinding process.

[0022] In addition, since the electrolytic reaction in step S1 requires graphite to be conductive, the crucible used in step S1 includes a graphite crucible and a tungsten crucible; and since no electrolytic reaction is required in step S2, the crucible used in step S2 can be any crucible that can be used for smelting metals, such as a tungsten crucible.

[0023] S3: Pulse current treatment during forging of cast rods S31: Place the high-conductivity magnesium alloy cast rod in a resistance furnace and set the holding temperature to 480°C for 11 hours to obtain a preheated magnesium alloy cast rod. Preheat the upper and lower cast iron anvils of the forging machine to 220°C, place the preheated magnesium alloy cast rod between the upper and lower cast iron anvils for fixing, then connect the positive electrode of the pulse power supply to the lower cast iron anvil, and the negative electrode to the preheated magnesium alloy cast rod. Set the current density to 3.5×10 6 A.m -2 Forging is performed; S32: During the upsetting and drawing process of forging, the direction is changed twice each time, the pressing speed of forging is set to 15 mm / s, the turning angle of the forging blank is 90° each time the direction is changed, the first upsetting reduction rate is 48%, the remaining upsetting single-pass reduction rate is 35%, the drawing single-pass reduction rate is 15%, the total forging passes are 35 passes, and the magnesium alloy forgings are obtained. The magnesium alloy forgings are placed in a resistance furnace for aging treatment. The aging treatment temperature is 220°C and the time is 20 hours to obtain a high-strength and heat-resistant magnesium alloy.

[0024] Example 2 A preparation process of a high-strength heat-resistant magnesium alloy, such as Figure 1 As shown, the following steps are included: S1: Electrolytic preparation of copper-cerium master alloy S11: Place a tungsten crucible at the center of the bottom of the graphite crucible. The radius ratio of the tungsten crucible to the graphite crucible is 1:2 and the tungsten crucible and the graphite crucible are insulated. 3The mixture was placed in a graphite crucible with a mass ratio of 1:0.2:0.8 and buried in the tungsten crucible. The graphite crucible was then placed in a resistance furnace and heated at 1000°C until NaCl, KCl and CeCl 3 Melt to obtain molten salt, including NaCl, KCl, CeCl 3 The purity is above 99.9%; S12: Insert the copper rod into the molten salt prepared in S11 from just above the tungsten crucible. The depth of the copper rod inserted into the molten salt is 2 / 3 of the length of the copper rod. Use the copper rod as the cathode and the graphite crucible as the anode for electrolysis. Set the current density of the electrolysis to 10A / cm 2 The copper rod generates copper-cerium alloy liquid and flows into the tungsten crucible until the tungsten crucible is filled with copper-cerium alloy liquid. The tungsten crucible is taken out and the copper-cerium alloy liquid in the tungsten crucible is placed in a mold and cast into a copper-cerium alloy ingot, which is broken into copper-cerium intermediate alloy particles with a particle size of 0.5 cm.

[0025] It should be noted that before electrolysis, the tungsten crucible will be submerged in molten salt, but after electrolysis, since the density of the copper-cerium alloy liquid is greater than the density of the molten salt, the copper-cerium alloy liquid flowing into the tungsten crucible will gradually squeeze out the molten salt, so that the tungsten crucible will eventually be filled with only copper-cerium alloy liquid but no molten salt.

[0026] S2: Preparation of high conductivity magnesium alloy casting rods S21: 20 parts by mass of The alloy is placed in a tungsten crucible. In alloy The mass fraction ratio of 200 μg / cm2 to Y is 1:0.25, and then it is sent into the resistance furnace, and the temperature of the resistance furnace is adjusted to 900°C. When the alloy is completely melted, 4 parts by mass of copper-cerium master alloy particles are added and protective gas is continuously introduced. After stirring for 4 minutes, the mixture is kept warm for 6 minutes. This stirring and keeping warm operation is repeated 4 times and then the mixture is placed in a mold and cast into a The alloy ingot was crushed and placed in a high-energy ball mill, and nitrogen was introduced. High-energy ball milling was performed at a speed of 500 r / min for 40 hours in a nitrogen atmosphere to obtain a nano master alloy powder with a particle size of 200 nm, wherein the high-energy grinding balls and The ball-to-material ratio of the alloy ingot is 1:0.3, and the protective gas is CO 2 and SF 6 The mixed gas composed of CO 2 and SF 6 The volume ratio is 1:98; S22: 120 parts by mass of pure magnesium are placed in a tungsten crucible and then sent into a resistance furnace, the temperature is set to 800°C, and a protective gas is introduced into the resistance furnace. When the pure magnesium is completely melted, the resistance furnace is powered off, and the nano master alloy powder obtained in step S21 and 2 parts by mass of pure Sn are added to the pure magnesium melt in sequence. While the protective gas is continuously introduced into the pure magnesium melt, the mixture is rapidly stirred at a stirring speed of 150 r / min for 5 minutes, the resistance furnace is turned on and kept warm at 800°C for 15 minutes to obtain a magnesium alloy melt, and the magnesium alloy melt is poured into a mold to be cooled and solidified to obtain a high-conductivity magnesium alloy cast rod, wherein the protective gas is CO 2 and SF 6 The mixed gas composed of CO 2 and SF 6 The volume ratio is 1:98.

[0027] It should be noted that high-energy ball mills have a variety of models, each of which is designed for a specific scale of alloy grinding tasks. However, given that the current factory is only equipped with a limited number of high-energy ball mills, in this application, the CuCe- Al The Y alloy ingots were crushed to ensure that they can fit into the company's existing ball mill models. It should be emphasized that this crushing process is based on the limitations of the factory equipment. If the company has a high-energy ball mill that can handle the grinding of ultra-large alloy volumes, then for the CuCe- Al Y alloy ingots do not need to be crushed and can be directly put into the grinding process.

[0028] In addition, since the electrolytic reaction in step S1 requires graphite to be conductive, the crucible used in step S1 includes a graphite crucible and a tungsten crucible; and since no electrolytic reaction is required in step S2, the crucible used in step S2 can be any crucible that can be used for smelting metals, such as a tungsten crucible.

[0029] S3: Pulse current treatment during forging of cast rods S31: Place a high-conductivity magnesium alloy cast rod in a resistance furnace and set the holding temperature to 450°C for 10 hours to obtain a preheated magnesium alloy cast rod. Preheat the upper and lower cast iron anvils of the forging machine to 200°C, place the preheated magnesium alloy cast rod between the upper and lower cast iron anvils for fixing, and then connect the positive electrode of the pulse power supply to the lower cast iron anvil and the negative electrode to the preheated magnesium alloy cast rod. Set the current density to 3×10 6 A.m -2 Forging is performed; S32: During the upsetting and drawing process of forging, the direction is changed once for each upsetting and drawing, the pressing speed of forging is set to 10 mm / s, the turning angle of the forging blank is 90° for each direction change, the first upsetting reduction rate is 45%, the remaining upsetting single-pass reduction rate is 30%, the drawing single-pass reduction rate is 10%, the total forging passes are 32 passes, and the magnesium alloy forgings are obtained. The magnesium alloy forgings are placed in a resistance furnace for aging treatment. The aging treatment temperature is 200°C and the time is 15 hours to obtain a high-strength and heat-resistant magnesium alloy.

[0030] Example 3 A preparation process of a high-strength heat-resistant magnesium alloy, such as Figure 1 As shown, the following steps are included: S1: Electrolytic preparation of copper-cerium master alloy S11: Place a tungsten crucible at the center of the bottom of the graphite crucible. The radius ratio of the tungsten crucible to the graphite crucible is 1:2 and the tungsten crucible and the graphite crucible are insulated. 3 The mixture was placed in a graphite crucible with a mass ratio of 1:0.6:1 and buried in the tungsten crucible. The graphite crucible was then heated in a resistance furnace at 1000°C until NaCl, KCl and CeCl 3 Melt to obtain molten salt, including NaCl, KCl, CeCl 3 The purity is above 99.9%; S12: Insert the copper rod into the molten salt prepared in S11 from just above the tungsten crucible. The depth of the copper rod inserted into the molten salt is 2 / 3 of the length of the copper rod. Use the copper rod as the cathode and the graphite crucible as the anode for electrolysis. Set the current density of the electrolysis to 10A / cm 2 The copper rod generates copper-cerium alloy liquid and flows into the tungsten crucible until the tungsten crucible is filled with copper-cerium alloy liquid. The tungsten crucible is taken out and the copper-cerium alloy liquid in the tungsten crucible is placed in a mold and cast into a copper-cerium alloy ingot, which is broken into copper-cerium intermediate alloy particles with a particle size of 0.5 cm.

[0031] It should be noted that before electrolysis, the tungsten crucible will be submerged in molten salt, but after electrolysis, since the density of the copper-cerium alloy liquid is greater than the density of the molten salt, the copper-cerium alloy liquid flowing into the tungsten crucible will gradually squeeze out the molten salt, so that the tungsten crucible will eventually be filled with only copper-cerium alloy liquid but no molten salt.

[0032] S2: Preparation of high conductivity magnesium alloy casting rods S21: 30 parts by mass of The alloy is placed in a tungsten crucible. In alloy The mass fraction ratio of 200 μg / cm2 to Y is 1:0.3, and then it is sent into the resistance furnace, and the temperature of the resistance furnace is adjusted to 900℃. When the alloy is completely melted, add 6 parts by mass of copper-cerium master alloy particles and continue to introduce protective gas. Stir for 4 minutes and keep warm for 6 minutes. Repeat this stirring and keeping warm operation 4 times and then place in a mold and cast into The alloy ingot was crushed and placed in a high-energy ball mill, and nitrogen was introduced. High-energy ball milling was performed at a speed of 500 r / min for 40 hours in a nitrogen atmosphere to obtain a nano master alloy powder with a particle size of 300 nm. The ball-to-material ratio of the alloy ingot is 1:0.3, and the protective gas is CO 2 and SF 6 The mixed gas composed of CO 2 and SF 6 The volume ratio is 1:98; S22: 150 parts by mass of pure magnesium are placed in a tungsten crucible and then sent into a resistance furnace, the temperature is set to 800°C, and a protective gas is introduced into the resistance furnace. When the pure magnesium is completely melted, the resistance furnace is powered off, and the nano master alloy powder prepared in step S21 and 3 parts by mass of pure Sn are added to the pure magnesium melt in sequence. While the protective gas is continuously introduced into the pure magnesium melt, the mixture is rapidly stirred at a stirring speed of 150 r / min for 5 minutes, the resistance furnace is turned on and kept warm at 800°C for 15 minutes to obtain a magnesium alloy melt, and the magnesium alloy melt is poured into a mold and cooled and solidified to obtain a high-conductivity magnesium alloy cast rod, wherein the protective gas is CO 2 and SF 6 The mixed gas composed of CO 2 and SF 6 The volume ratio is 1:98.

[0033] It should be noted that high-energy ball mills have a variety of models, each of which is designed for a specific scale of alloy grinding tasks. However, given that the current factory is only equipped with a limited number of high-energy ball mills, in this application, the CuCe- Al The Y alloy ingots were crushed to ensure that they can fit into the company's existing ball mill models. It should be emphasized that this crushing process is based on the limitations of the factory equipment. If the company has a high-energy ball mill that can handle the grinding of ultra-large alloy volumes, then for the CuCe- Al Y alloy ingots do not need to be crushed and can be directly put into the grinding process.

[0034] In addition, since the electrolytic reaction in step S1 requires graphite to be conductive, the crucible used in step S1 includes a graphite crucible and a tungsten crucible; and since no electrolytic reaction is required in step S2, the crucible used in step S2 can be any crucible that can be used for smelting metals, such as a tungsten crucible.

[0035] S3: Pulse current treatment during forging of cast rods S31: Place a high-conductivity magnesium alloy cast rod in a resistance furnace and set the holding temperature to 450°C for 10 hours to obtain a preheated magnesium alloy cast rod. Preheat the upper and lower cast iron anvils of the forging machine to 200°C, place the preheated magnesium alloy cast rod between the upper and lower cast iron anvils for fixing, and then connect the positive electrode of the pulse power supply to the lower cast iron anvil and the negative electrode to the preheated magnesium alloy cast rod. Set the current density to 3×10 6 A.m -2 Forging is performed; S32: During the upsetting and drawing process of forging, the direction is changed once for each upsetting and drawing, the pressing speed of forging is set to 10 mm / s, the turning angle of the forging blank is 90° for each direction change, the first upsetting reduction rate is 45%, the remaining upsetting single-pass reduction rate is 30%, the drawing single-pass reduction rate is 10%, the total forging passes are 32 passes, and the magnesium alloy forgings are obtained. The magnesium alloy forgings are placed in a resistance furnace for aging treatment. The aging treatment temperature is 200°C and the time is 15 hours to obtain a high-strength and heat-resistant magnesium alloy.

[0036] Example 4 A preparation process of a high-strength heat-resistant magnesium alloy, such as Figure 1 As shown, the following steps are included: S1: Electrolytic preparation of copper-cerium master alloy S11: Place a tungsten crucible at the center of the bottom of the graphite crucible. The radius ratio of the tungsten crucible to the graphite crucible is 1:3 and the tungsten crucible and the graphite crucible are insulated. 3 The mixture was placed in a graphite crucible with a mass ratio of 1:0.2:0.8 and buried in the tungsten crucible. The graphite crucible was then placed in a resistance furnace and heated at 1050°C until NaCl, KCl and CeCl 3 Melt to obtain molten salt, including NaCl, KCl, CeCl 3 The purity is above 99.9%; S12: Insert the copper rod into the molten salt prepared in S11 from just above the tungsten crucible. The depth of the copper rod inserted into the molten salt is 3 / 4 of the length of the copper rod. Use the copper rod as the cathode and the graphite crucible as the anode for electrolysis. Set the current density of the electrolysis to 15A / cm 2 The copper rod generates copper-cerium alloy liquid and flows into the tungsten crucible until the tungsten crucible is filled with copper-cerium alloy liquid. The tungsten crucible is taken out and the copper-cerium alloy liquid in the tungsten crucible is placed in a mold and cast into a copper-cerium alloy ingot, which is then broken into copper-cerium intermediate alloy particles with a particle size of 1 cm.

[0037] It should be noted that before electrolysis, the tungsten crucible will be submerged in molten salt, but after electrolysis, since the density of the copper-cerium alloy liquid is greater than the density of the molten salt, the copper-cerium alloy liquid flowing into the tungsten crucible will gradually squeeze out the molten salt, so that the tungsten crucible will eventually be filled with only copper-cerium alloy liquid but no molten salt.

[0038] S2: Preparation of high conductivity magnesium alloy casting rods S21: 20 parts by mass of The alloy is placed in a tungsten crucible. In alloy The mass fraction ratio of Y is 1:0.25, and then it is sent into the resistance furnace, and the temperature of the resistance furnace is adjusted to 950℃. When the alloy is completely melted, 4 parts by mass of copper-cerium master alloy particles are added and protective gas is continuously introduced. After stirring for 5 minutes, the mixture is kept warm for 8 minutes. This stirring and keeping warm operation is repeated 5 times and then the mixture is placed in a mold and cast into a The alloy ingot was crushed and placed in a high-energy ball mill, and nitrogen was introduced. The high-energy ball milling was performed at a speed of 600 r / min for 48 hours in a nitrogen atmosphere to obtain a nano master alloy powder with a particle size of 500 nm. The ball-to-material ratio of the alloy ingot is 1:0.4, and the protective gas is CO 2 and SF 6 The mixed gas composed of CO 2 and SF 6 The volume ratio is 1:99; S22: 120 parts by mass of pure magnesium are placed in a tungsten crucible and then sent into a resistance furnace, the temperature is set to 850°C, and a protective gas is introduced into the resistance furnace. When the pure magnesium is completely melted, the resistance furnace is powered off, and the nano master alloy powder prepared in step S21 and 2 parts by mass of pure Sn are added to the pure magnesium melt in sequence. While the protective gas is continuously introduced into the pure magnesium melt, the mixture is rapidly stirred at a stirring speed of 200 r / min for 8 minutes, the resistance furnace is turned on and kept warm at 850°C for 20 minutes to obtain a magnesium alloy melt, and the magnesium alloy melt is poured into a mold to be cooled and solidified to obtain a high-conductivity magnesium alloy cast rod, wherein the protective gas is CO 2 and SF 6 The mixed gas composed of CO 2 and SF 6 The volume ratio is 1:99.

[0039] It should be noted that high-energy ball mills have a variety of models, each of which is designed for a specific scale of alloy grinding tasks. However, given that the current factory is only equipped with a limited number of high-energy ball mills, in this application, the CuCe- AlThe Y alloy ingots were crushed to ensure that they can fit into the company's existing ball mill models. It should be emphasized that this crushing process is based on the limitations of the factory equipment. If the company has a high-energy ball mill that can handle the grinding of ultra-large alloy volumes, then for the CuCe- Al Y alloy ingots do not need to be crushed and can be directly put into the grinding process.

[0040] In addition, since the electrolytic reaction in step S1 requires graphite to be conductive, the crucible used in step S1 includes a graphite crucible and a tungsten crucible; and since no electrolytic reaction is required in step S2, the crucible used in step S2 can be any crucible that can be used for smelting metals, such as a tungsten crucible.

[0041] S3: Pulse current treatment during forging of cast rods S31: Place the high-conductivity magnesium alloy cast rod in a resistance furnace and set the holding temperature to 500°C for 12 hours to obtain a preheated magnesium alloy cast rod. Preheat the upper and lower cast iron anvils of the forging machine to 250°C, place the preheated magnesium alloy cast rod between the upper and lower cast iron anvils for fixing, and then connect the positive electrode of the pulse power supply to the lower cast iron anvil and the negative electrode to the preheated magnesium alloy cast rod. Set the current density to 4×10 6 A.m -2 Forging is performed; S32: During the upsetting and drawing process of forging, the direction is changed three times each time the upsetting and drawing is performed, the pressing speed of forging is set to 20 mm / s, the turning angle of the forging blank is 90° each time the direction is changed, the first upsetting reduction rate is 50%, the remaining upsetting single-pass reduction rate is 40%, the drawing single-pass reduction rate is 20%, the total forging passes are 40 passes, and the magnesium alloy forgings are obtained. The magnesium alloy forgings are placed in a resistance furnace for aging treatment. The aging treatment temperature is 250°C and the time is 25 hours to obtain a high-strength and heat-resistant magnesium alloy.

[0042] Comparative Example 1 Compared with Example 1, the difference of Comparative Example 1 is that Comparative Example 1 eliminates the operation of using the positive pole of the pulse power supply to connect the lower cast iron anvil and the negative pole to connect the preheated magnesium alloy casting rod in step S31, and the remaining steps are the same as those in Example 1. The obtained high-strength and heat-resistant magnesium alloy is recorded as Comparative Example 1.

[0043] Comparative Example 2 Compared with Example 1, the difference of Comparative Example 2 is that, in Comparative Example 2, step S1 and step S21 are removed, and the nano master alloy powder in step S22 is replaced by an equal amount of Alloy powder, and other steps are the same as those in Example 1, and the obtained high-strength heat-resistant magnesium alloy is recorded as Comparative Example 2.

[0044] Comparative Example 3 Compared with Example 1, the difference of Comparative Example 3 is that step S1 is removed in Comparative Example 3, and the copper-cerium intermediate alloy particles in step S21 are replaced with 2 parts by mass of copper and 0.5 parts by mass of Ce. The remaining steps are the same as those in Example 1, and the obtained high-strength heat-resistant magnesium alloy is recorded as Comparative Example 3.

[0045] Experiment 1: The high-strength heat-resistant magnesium alloys prepared in Examples 1-4 and Comparative Examples 1-3 were processed into standard tensile specimens according to the requirements of the national standard GB6397-86 "Metal Tensile Test Specimens". The yield strength at room temperature was tested using a universal testing machine. Three parallel specimens were used for each yield strength test. The final result was the average of the three experiments. Then, new specimens were taken for high-temperature tensile performance tests at room temperature, 200°C and 350°C, respectively. The tensile strain rate was 10 -3 s -1 Each tensile strength test was performed with three parallel specimens. The final result was the average value of three experiments. The above test data were recorded and tabulated, as shown in Table 1.

[0046]

[0047] It can be seen from the data of Examples 1-4 and Comparative Example 1 in Table 1 that when the preheated magnesium alloy cast rods are not subjected to pulse current treatment during forging, the yield strength, room temperature tensile strength, 200°C tensile strength and 350°C tensile strength of the obtained high-strength and heat-resistant magnesium alloy are all lower than the yield strength, room temperature tensile strength, 200°C tensile strength and 350°C tensile strength of the high-strength and heat-resistant magnesium alloy obtained after pulse current treatment, which fully proves that under the action of pulse current, in combination with the forging process of the present invention, the strength and thermal stability of the magnesium alloy can be greatly improved.

[0048] It can be seen from the data of Examples 1-4 and Comparative Example 2 in Table 1 that when no copper-cerium master alloy particles are added during the preparation of the magnesium alloy, the yield strength, room temperature tensile strength, 200°C tensile strength and 350°C tensile strength of the obtained high-strength and heat-resistant magnesium alloy are lower than the yield strength, room temperature tensile strength, 200°C tensile strength and 350°C tensile strength of the high-strength and heat-resistant magnesium alloy obtained after adding the copper-cerium master alloy particles, which fully proves that the addition of the copper-cerium master alloy particles can not only perform solid solution strengthening on the lattice of the magnesium alloy and improve the thermal stability, but also provide good electrical conductivity for the magnesium alloy casting rod, improve the subsequent pulse current forging effect, and further enhance the strength of the magnesium alloy.

[0049] It can be seen from the data of Examples 1-4 and Comparative Example 3 in Table 1 that in step S21, the copper-cerium intermediate alloy particles obtained by molten salt electrolysis are replaced with 2 parts by mass of copper and 0.5 parts by mass of Ce, and the yield strength, room temperature tensile strength, 200°C tensile strength and 350°C tensile strength of the obtained high-strength and heat-resistant magnesium alloy are lower than the yield strength, room temperature tensile strength, 200°C tensile strength and 350°C tensile strength of the high-strength and heat-resistant magnesium alloy prepared from the copper-cerium intermediate alloy particles obtained by molten salt electrolysis. This fully proves that preparing the copper-cerium intermediate alloy by molten salt electrolysis of Cu and Ce is beneficial to improving the subsequent pulse current forging effect and further enhancing the strength and thermal stability of the magnesium alloy.

[0050] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A process for preparing a high-strength heat-resistant magnesium alloy, characterized in that: The following steps are involved: S1: Electrolytic preparation of copper-cerium master alloy NaCl, KCl and CeCl3 are placed in a graphite crucible to melt into molten salt, and then a copper rod is inserted into the molten salt as a cathode, and the graphite crucible is used as an anode for electrolysis, and the copper-cerium alloy liquid produced by the electrolysis is collected and cast into a copper-cerium alloy ingot, and the copper-cerium intermediate alloy particles are obtained after crushing; S2: Preparation of high conductivity magnesium alloy casting rods Will After the alloy is melted, copper-cerium master alloy particles are added, and the stirring and heat preservation operation is repeated under a protective atmosphere, and then cast into The alloy ingot is subjected to high-energy ball milling to obtain nano master alloy powder, pure magnesium is melted, and then the nano master alloy powder and pure Sn are added in sequence, stirred under a protective atmosphere, and then kept warm, and then poured into a mold to obtain a high-conductivity magnesium alloy cast rod; S3: Pulse current treatment during forging of cast rods The high-conductivity magnesium alloy cast rod is preheated and then fixed between the upper and lower cast iron anvils of a forging machine. The positive pole of a pulse power supply is connected to the lower cast iron anvil of the forging machine, and the negative pole is connected to the preheated high-conductivity magnesium alloy cast rod. After power is turned on, forging is performed to obtain a magnesium alloy forging. The magnesium alloy forging is subjected to aging treatment to obtain a high-strength and heat-resistant magnesium alloy.

2. The process for preparing a high-strength heat-resistant magnesium alloy according to claim 1, characterized in that: Step S1: electrolytically preparing a copper-cerium master alloy, comprising the following steps: S11: placing a tungsten crucible at the center of the bottom of the graphite crucible, the radius ratio of the tungsten crucible to the graphite crucible is 1:2-3 and the tungsten crucible and the graphite crucible are insulated, powdered NaCl, KCl and CeCl3 are mixed in a mass ratio of 1:0.2-0.6:0.8-1 and placed in the graphite crucible to bury the tungsten crucible, and then the graphite crucible is placed in a resistance furnace and heated at a temperature of 1000-1050°C until NaCl, KCl and CeCl3 are melted to obtain molten salt, wherein the purity of NaCl, KCl and CeCl3 is more than 99.9%; S12: Insert the copper rod from the top of the tungsten crucible into the molten salt prepared in S11, use the copper rod as the cathode and the graphite crucible as the anode for electrolysis, and set the current density of electrolysis to 10-15A / cm 2 The copper rod generates copper-cerium alloy liquid and flows into the tungsten crucible until the tungsten crucible is filled with copper-cerium alloy liquid. The tungsten crucible is taken out and the copper-cerium alloy liquid in the tungsten crucible is placed in a mold and cast into a copper-cerium alloy ingot, which is broken into copper-cerium intermediate alloy particles with a particle size of 0.5-1 cm.

3. The process for preparing a high-strength heat-resistant magnesium alloy according to claim 1, characterized in that: Step S2: Preparation of high-conductivity magnesium alloy cast rods, comprising the following steps: S21: 20-30 parts by mass of The alloy is placed in a tungsten crucible and then sent into a resistance furnace. The temperature of the resistance furnace is adjusted to 900-950℃. When the alloy is completely melted, add 4-6 parts by mass of copper-cerium master alloy particles and continue to introduce protective gas, stir for 4-5 minutes and keep warm for 6-8 minutes, repeat this stirring and keeping warm operation 4-5 times and then place in a mold and cast into The alloy ingot is crushed and placed in a high-energy ball mill, and nitrogen is introduced. The high-energy ball mill is performed at a speed of 500-600r / min for 40-48 hours in a nitrogen atmosphere to obtain a nano master alloy powder, wherein the high-energy grinding balls and The ball-to-material ratio of the alloy ingot is 1:0.3-0.4; S22: 120-150 parts by mass of pure magnesium are placed in a tungsten crucible and then introduced into a resistance furnace, the temperature is set to 800-850°C, and a protective gas is introduced into the resistance furnace. When the pure magnesium is completely melted, the resistance furnace is powered off, and the nano intermediate alloy powder prepared in step S21 and 2-3 parts by mass of pure Sn are sequentially added to the pure magnesium melt. While continuously introducing a protective gas into the pure magnesium melt, the mixture is rapidly stirred at a stirring speed of 150-200 r / min for 5-8 minutes. The resistance furnace is opened and kept warm at a temperature of 800-850°C for 15-20 minutes to obtain a magnesium alloy melt, and the magnesium alloy melt is poured into a mold to be cooled and solidified to obtain a high-conductivity magnesium alloy cast rod.

4. The process for preparing a high-strength heat-resistant magnesium alloy according to claim 1, characterized in that: Step S3: Pulse current treatment during the forging process of the cast rod, comprising the following steps: S31: Place the high-conductivity magnesium alloy cast rod in a resistance furnace, set the holding temperature to 450-500°C, and keep it warm for 10-12 hours to obtain a preheated magnesium alloy cast rod. Preheat the upper and lower cast iron anvils of the forging machine to 200-250°C, place the preheated magnesium alloy cast rod between the upper and lower cast iron anvils for fixing, and then connect the positive electrode of the pulse power supply to the lower cast iron anvil, and the negative electrode to the preheated magnesium alloy cast rod. Set the current density to 3×10 6 -4×10 6 A.m -2 Forging is performed; S32: During the upsetting and drawing process of forging, the direction is changed 1-3 times each time the upsetting and drawing is performed, the pressing speed of forging is set to 10-20 mm / s, the turning angle of the forging blank is 90° each time the direction is changed, the first upsetting reduction rate is 45-50%, the remaining upsetting single-pass reduction rate is 30-40%, the drawing single-pass reduction rate is 10-20%, the total forging passes are 32-40 passes, and the magnesium alloy forgings are obtained. The magnesium alloy forgings are placed in a resistance furnace for aging treatment to obtain a high-strength heat-resistant magnesium alloy.

5. The process for preparing a high-strength heat-resistant magnesium alloy according to claim 2, characterized in that: In step S12, the depth of the copper rod inserted into the molten salt is 2 / 3-3 / 4 of the length of the copper rod.

6. The process for preparing a high-strength heat-resistant magnesium alloy according to claim 3, characterized in that: In step S21 In alloy The mass fraction ratio of Y is 1:0.25-0.3, and the particle size of the nano master alloy powder is 200-500nm.

7. The process for preparing a high-strength heat-resistant magnesium alloy according to claim 3, characterized in that: The protective gas in step S2 is a mixed gas composed of CO2 and SF6, wherein the volume ratio of CO2 to SF6 is 1:98-99.

8. The process for preparing a high-strength heat-resistant magnesium alloy according to claim 4, characterized in that: In step S32, the temperature of the aging treatment of the magnesium alloy forging is 200-250° C., and the time is 15-25 hours.

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