CN112708815B

CN112708815B - Heat-conducting anti-fatigue magnesium alloy and preparation method thereof

Info

Publication number: CN112708815B
Application number: CN202011426341.7A
Authority: CN
Inventors: 朱训明; 刘旦; 孟祥鋆; 徐国松; 王建; 段军鹏
Original assignee: Weihai Wanfeng Magnesium Industry Development Co ltd
Current assignee: Weihai Wanfeng Magnesium Industry Development Co ltd
Priority date: 2020-12-09
Filing date: 2020-12-09
Publication date: 2022-05-06
Anticipated expiration: 2040-12-09
Also published as: CN112708815A

Abstract

The invention provides a heat-conducting anti-fatigue magnesium alloy and a preparation method thereof, which solve the technical problems of poor heat-conducting property and low strength of the existing magnesium alloy and are composed of the following components in percentage by weight: 2 to 7% of Zn, 0.2 to 5% of Sn, 0.2 to 1% of Mn, and the balance of Mg, wherein the thermal conductivity of the magnesium alloy is 105 to 140W (m.K)^‑1The fracture toughness is 12-20 MPa.m^1/2. The magnesium alloy can be used as a material for key bearing structural members such as power supplies in aerospace, heat dissipation systems of electronic devices, car hubs, battery trays of electric vehicles and the like, and can also be used as a heat dissipation material for casings of notebook computers, mobile phones and the like, radiators thereof and LED (light-emitting diode) lighting. The invention relates to the technical field of industrial magnesium alloy.

Description

Heat-conducting anti-fatigue magnesium alloy and preparation method thereof

Technical Field

The application belongs to the technical field of industrial magnesium alloy, and particularly relates to a heat-conducting anti-fatigue magnesium alloy and a preparation method thereof.

Background

The materials for the power supply in aerospace, the heat dissipation system structure material of electronic devices, the material for the car hub, the battery tray of electric vehicles and other key load-bearing structural members need to have low density, good fatigue resistance (namely high fracture toughness) and high heat conductivity. The higher the thermal conductivity of the material of the component is, the stronger the heat conduction capability generated by the system is, the temperature fluctuation amplitude of the system and the deformation of the component under the action of thermal load are reduced, and the heat conduction component plays an important role in improving the reliability, the service life and the effective load of a spacecraft system and a battery system of an electric vehicle and reducing the tire burst risk. In addition, the high-thermal conductivity magnesium alloy has wide application prospects in the fields of notebook computers, mobile phones and other shells, radiators thereof, LED lighting heat dissipation materials and the like. Therefore, the high-strength and high-thermal conductivity magnesium alloy has an important application background.

Pure magnesium has a thermal conductivity of 155W. (m.K)^-1Fracture toughness of about 5MPa.m^1/2The tensile strength is about 10 MPa; after alloying, the fracture toughness and strength are greatly improved, and the heat conductivity coefficient is obviously reduced. For example, according to the American Handbook of magnesium and Alloys (ASMSspecialty Handbook: Magnesnum and Magnesnum Alloys), aluminum-and zinc-containing magnesium alloy AZ81, which has a tensile strength of 375MPa and a thermal conductivity of 51W (m.K) at 20 ℃. (m.K)^-1(ii) a The rare earth magnesium alloy WE43 has tensile strength up to 270MPa and heat conductivity coefficient at 20 deg.C of 51W (m.K)^-1(ii) a Magnesium alloy ZE41 containing zinc and rare earth, its tensile strength can reach 265Mpa, and its thermal conductivity coefficient at 20 deg.C is 123W. (m.K)^-1(ii) a Magnesium alloy ZC63 containing zinc and copper and having tensile strength of 210MPa and thermal conductivity of 122W (m.K) at 20 deg.C^-1(ii) a Magnesium alloy containing silver and rare earth QE22, its tensile strength is 260Mpa, thermal conductivity at 20 deg.C is 113W. (m.K)^-1。

The existing magnesium alloy has high thermal conductivity such as ZE41 and QE22, and the fracture toughness is less than 12MPa^1/2The strength is less than 275 MPa; and higher fracture toughness and strength such as AZ81, WE43, both having thermal conductivity less than 55W. (m.K)^-1。

Disclosure of Invention

The invention aims to solve the defects of the background technology and provides a magnesium alloy with high thermal conductivity, fatigue resistance and strength and a preparation method thereof.

Therefore, the invention provides a heat-conducting anti-fatigue magnesium alloy which comprises the following components in percentage by weight: 2 to 7% of Zn, 0.2 to 5% of Sn, 0.2 to 1% of Mn, and the balance of Mg, wherein the thermal conductivity of the magnesium alloy is 105 to 140W (m.K)^-1And a fracture toughness of 12 to 20MPa.m^1/2。

Preferably, the magnesium alloy consists of the following components in percentage by weight: 3.5 to 5.5 percent of Zn, 0.5 to 3 percent of Sn, 0.5 to 0.8 percent of Mn and the balance of Mg.

Preferably, the magnesium alloy contains an MgZn phase, alpha Mg₂A Sn phase and a beta-Mn solid solution phase.

Zinc is a silver gray transition metal, has a close-packed hexagonal structure as does the base metal magnesium, and has an atomic radius of 1.534 and an atomic radius of 1.598, which are the smallest differences among all the alloying elements of the magnesium alloy, so that zinc, as an alloying element of the magnesium alloy, has the smallest degree of lattice distortion with respect to the base metal magnesium. About half of the total world zinc consumption is for galvanization, about 10% for brass and bronze, less than 10% for zinc-based alloys, about 7.5% for chemicals, and about 13% for manufacturing dry cells, appearing as zinc cakes, zinc plates. Zinc has suitable mechanical properties. The strength and hardness of zinc are not high, but after alloy elements such as aluminum, copper and the like are added, the strength and hardness of the zinc alloy are greatly improved, namely the zinc-copper-titanium alloy appears, the comprehensive mechanical property of the zinc alloy is close to or reaches the level of aluminum alloy, brass and gray cast iron, and the creep resistance of the zinc alloy is also greatly improved. Zinc alloy has been widely used in the production of automobiles, machinery, buildings, parts of electrical equipment, household appliances, toys and small hardware, mainly as die castings. Many zinc alloys have excellent processing performance, and the pass processing rate can reach 60 to 80 percent. The medium-pressure die has excellent medium-pressure performance, can be subjected to deep drawing, has self-lubricating property, prolongs the service life of a die, can be welded by brazing, resistance welding or arc welding, can be subjected to electroplating and painting treatment on the surface, and has good cutting processability. In addition, zinc has good electromagnetic field resistance. The conductivity of zinc is 29% of that of standard electrical copper, the zinc plate is a very effective shielding material, meanwhile, the zinc is non-magnetic, so that the zinc plate is suitable for being used as the material of instrument parts, instrument shells and coins, and meanwhile, the zinc per se and other metals can not generate sparks when colliding, so that the zinc plate is suitable for being used as an underground explosion-proof apparatus.

FIG. 1 is a Mg-Zn binary phase diagram, and by analyzing the Mg-Zn binary phase diagram, the maximum solid solubility of the element Zn in Mg is up to 6.2 wt% at about 340 ℃, and the maximum solid solubility is reduced remarkably along with the temperature reduction, and about 1.5 wt% at room temperature, and the MgZn phase generated by desolventizing has better strengthening effect. 2-7 wt% of Zn is added into metal magnesium to ensure that the magnesium alloy has high heat conductivity to the maximum extent, and has high room temperature strength after casting forming or deformation processing and heat treatment, so that the alloy meets the application requirements of materials for key load-bearing structural members such as power supplies in aerospace, heat dissipation systems of electronic devices, car hubs, battery trays of electric vehicles and the like, and the application requirements of the materials in the fields of casings of notebook computers, mobile phones and the like, radiators thereof, LED lighting heat dissipation materials and the like.

Tin is a low melting point metal with silvery white luster, is not easily oxidized by air, and has the element symbol Sn, carbon group elements, the atomic number of 50 and the atomic weight of 118.71. The metallic tin is soft and easy to bend, and has a melting point of 231.89 ℃ and a boiling point of 2260 ℃. There are three allotropes, respectively: white tin is a tetragonal system, the unit cell parameters a are 0.5832nm, c are 0.3181nm, the unit cell contains 4Sn atoms, the density is 7.28 g/cubic centimeter, the hardness is 2, and the ductility is good; the gray tin is a diamond-shaped cubic crystal system, the unit cell parameter a is 0.6489nm, the unit cell contains 8 Sn atoms, and the density is 5.75 g/cubic centimeter; brittle tin is an orthorhombic system and has the density of 6.54 g/cubic centimeter. Tin is chemically stable and is not easily oxidized by oxygen at normal temperature, so that it always keeps the glittering luster of silver, and a tin dioxide protective film is formed on the surface of tin in the air to stabilize, and the oxidation reaction is accelerated along with the temperature rise. The tin was soft and it could be cut with a knife. Tin is rich in ductility at normal temperature, particularly at 100 ℃, the ductility is very good, and extremely thin tin foil can be formed. In general, people pack cigarettes and candies with tinfoil to prevent moisture.

FIG. 2 is a Mg-Sn binary phase diagram, and by analyzing the Mg-Sn binary phase diagram, the maximum solid solubility of the element Sn in Mg is as high as 14.48 wt% at about 561 ℃, the maximum solid solubility is reduced rapidly along with the temperature reduction, and the maximum solid solubility is almost zero at room temperature, and the intermetallic compound alpha Mg2Sn phase generated by desolventization has high-temperature stability. The addition of 0.2-5 wt% of Sn in magnesium metal is to ensure that the alloy has higher creep resistance at the temperature of above 125 ℃, so that the alloy meets the application requirements of materials for key load-bearing structural members such as power supplies in aerospace, heat dissipation systems of electronic devices, car hubs, battery trays of electric vehicles and the like, and the application requirements in the fields of housings of notebook computers, mobile phones and the like, radiators thereof, LED lighting heat dissipation materials and the like.

Manganese metal, symbol Mn, atomic weight of element 54.94, VIIB group element. Silver white metal, hard and brittle. Belongs to a relatively active metal, can be combined with oxygen when heated, and is easy to dissolve in dilute acid to generate divalent manganese salt. Density 7.44 g/cc, melting point 1244 ℃. In the solid state, there are four allotropes, namely alpha manganese (body-centered cubic), beta manganese (cubic), gamma manganese (face-centered cubic), and delta manganese (body-centered cubic). The bulk modulus of elasticity is 120(GPa), and the heat capacity is 26.32J/(mol.K). The manganese has good deoxidizing capacity, and can reduce FeO in the steel into iron and improve the quality of the steel; MnS may also be formed with sulfur, thereby mitigating the deleterious effects of sulfur. Manganese can be mostly dissolved in ferrite to form a substitution solid solution, so that the ferrite strengthens and improves the strength and the hardness of steel, and therefore, manganese is commonly used as an additive of alloy to improve the strength, the hardness, the elastic limit, the wear resistance, the corrosion resistance and the like of the steel; in high alloy steel, it is also used as an austenitizing alloy element for refining stainless steel, special alloy steel, stainless steel electrode, etc. Manganese steel is used for manufacturing steel mills, ball bearings, frequently-ground components such as buckets of bulldozers and excavators, iron-manganese rails, bridges and the like. The high manganese steel is used for manufacturing helmets, tank steel armatures, armor piercing bullets and the like. Manganese is one of the essential trace elements of the normal body, is a component of several enzyme systems including manganese-specific glycosyltransferase and phosphoenolpyruvate carboxykinase and is essential for normal bone structure, and is taken from 3-9 mg per day in normal dietary situations.

FIG. 3 is a Mg-Mn binary phase diagram, and by analyzing the Mg-Mn binary phase diagram, it was found that an L + β (Mn) → α solid solution occurs at 650 ℃. The solubility of Mn in the α solid solution was 3.3% at the peritectic temperature. The solid solubility decreased rapidly with decreasing temperature, with w (mn) 2.06% at 620 ℃ and w (mn) 0.25% at 455 ℃. Since β -Mn is practically pure manganese, its main role in magnesium alloys is to refine grains as a core for dynamic recrystallization nucleation during deformation processing, to improve alloy strength and plasticity while maximally retaining high thermal conductivity in the pure magnesium state, and to remove its harmful effects on corrosion resistance by combining with harmful impurity elements such as Fe, Ni, so that the corrosion rate, particularly in marine climates, is significantly reduced. The addition of 0.2 to 1% Mn to magnesium metal is intended to fully exhibit the above-mentioned effects.

Meanwhile, the invention provides a preparation method of the heat-conducting anti-fatigue magnesium alloy, which comprises the following steps:

(1) preparing raw materials: taking a pure magnesium ingot as a raw material of a magnesium element in the magnesium alloy, taking a pure Zn ingot as a raw material of a zinc element in the magnesium alloy, taking a pure Sn ingot as a raw material of a tin element in the magnesium alloy, taking an Mg-Mn intermediate alloy as a raw material of a manganese element in the magnesium alloy, and weighing according to the weight percentage of the components of the magnesium alloy;

(2) melting a pure magnesium ingot: stacking the pure magnesium ingots weighed in the step (1) in a melting crucible of a melting furnace in a compact manner, completely melting under the protection of protective gas, No. 2 solvent or magnesium smelting covering agent, controlling the temperature to be 680-830 ℃, cleaning floating slag on the surface of the molten liquid, and uniformly spraying No. 2 flux or magnesium smelting covering agent on the surface of the molten liquid to obtain magnesium molten liquid;

(3) addition of alloying elements Zn, Sn and Mn: immersing the preheated pure Zn ingot, pure Sn ingot and Mg-Mn intermediate alloy ingot into the magnesium solution in the step (2), heating, preserving heat, casting a spectrum sample, carrying out stokehole analysis, and adding materials until the components of the magnesium alloy comprise 2-7% by weight of Zn, 0.2-5% by weight of Sn, 0.2-1% by weight of Mn and the balance of Mg, thereby obtaining the magnesium alloy solution;

(4) casting and forming: casting and molding the magnesium alloy melt obtained in the step (3) to obtain a casting or a billet, and carrying out solution heat treatment on the casting or carrying out homogenization heat treatment on the billet to obtain a part or a forging;

(5) aging heat treatment: and (4) carrying out aging heat treatment on the part or the forging prepared in the step (4) to obtain the magnesium alloy.

Preferably, the No. 2 flux in the step (2) consists of 30-65 wt% of magnesium chloride and 35-70 wt% of potassium chloride, and the magnesium-smelting covering agent consists of 30-63 wt% of magnesium chloride, 35-68 wt% of potassium chloride and 1-5 wt% of sulfur.

Preferably, in the step (2), the process of complete melting under the protection of the protective gas is as follows: before stacking the pure magnesium ingot in a melting crucible, uniformly scattering sulfur powder at the bottom of the melting crucible, stacking the pure magnesium ingot in the melting crucible, uniformly scattering sulfur powder on the surface of the pure magnesium ingot, sealing the melting crucible by using a crucible cover, and controlling the heating temperature to be 680-830 ℃ so that all the pure magnesium ingots are completely melted under the protection of sulfur dioxide and residual nitrogen after combustion.

Preferably, in the step (4), the temperature for the solid solution heat treatment of the casting is 325-500 ℃, and the heat preservation time is 5-36 hours.

Preferably, in the step (4), the temperature for homogenizing heat treatment of the ingot is 325 to 500 ℃, and the holding time is 5 to 50 hours.

Preferably, after the billet is subjected to homogenization heat treatment, the billet is directly subjected to deformation processing by adopting rolling, extruding, drawing or forging processes to form a plate, a pipe, a section, a bar, a wire or various forgings, and the plate, the pipe, the section, the bar or the wire is subjected to pre-stretching treatment at room temperature by using a stretcher, wherein the pre-stretching deformation is 0.5-5%.

Preferably, in the step (5), the temperature of the aging heat treatment is 125-200 ℃, and the heat preservation time is 5-50 hours.

The heat-conducting anti-fatigue magnesium alloy has the advantages that:

(1) the magnesium alloy contains Zn, Sn and Mn alloy elements, wherein 2-7 wt% of Zn is added into metal magnesium to ensure that the magnesium alloy has higher room temperature strength after casting forming or deformation processing and heat treatment on the basis of keeping high thermal conductivity to the maximum extent; 0.2-5 wt% of Sn is added into the metal magnesium to ensure that the metal magnesium also has higher creep resistance at the temperature of above 125 ℃; the addition of 0.2-1% of Mn to magnesium metal is to refine grains and improve alloy strength and plasticity for the purpose of dynamic recrystallization nucleation during deformation processing, and to retain the high thermal conductivity of pure magnesium to the maximum extent, and to eliminate the harmful effects on corrosion resistance by combining with harmful impurity elements such as Fe and Ni, so that the corrosion rate, particularly in marine climate, is significantly reduced.

(2) The magnesium alloy has a thermal conductivity of 105 to 140W (m.K)^-1And a fracture toughness of 12 to 20MPa.m^1/2The material can be used as a material for key load-bearing structural members such as power supplies in aerospace, heat dissipation systems of electronic devices, car hubs, battery trays of electric vehicles and the like, and can also be used as a heat dissipation material for casings of notebook computers, mobile phones and the like, radiators thereof and LED illumination.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

FIG. 1 is a Mg-Zn binary phase diagram;

FIG. 2 is a Mg-Sn binary phase diagram;

FIG. 3 is a Mg-Mn binary phase diagram.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

Example 11000 kg of Mg-2Zn-0.2Sn-0.2Mn heat-conductive fatigue-resistant magnesium alloy (i.e., the magnesium alloy comprises 2% Zn, 0.2% Sn, 0.2% Mn, and the balance Mg) and a method for preparing the same by rolling a plate thereof.

(1) Preparing raw materials: 938 kg of pure magnesium ingot, 20 kg of pure Zn ingot, 2 kg of pure Sn ingot and 40 kg of Mg-5% Mn intermediate alloy are prepared.

(2) Melting a pure magnesium ingot: 938 kilograms of pure magnesium ingots are stacked in a melting crucible in a mode of being as compact as possible, sulfur powder is uniformly scattered at the bottom of the crucible and on the surface of the pure magnesium ingots, and the amount of the sulfur powder is based on the fact that oxygen in the crucible can be completely converted into sulfur dioxide after oxidation combustion. And (2) sealing the crucible by using a crucible cover, controlling the heating temperature to be 680-830 ℃, completely melting all pure magnesium ingots under the protection of sulfur dioxide and residual nitrogen after combustion, opening the crucible cover, cleaning floating slag on the surface of the molten magnesium, uniformly spraying No. 2 flux or a covering agent for smelting magnesium on the surface of the molten magnesium, and preventing the magnesium from burning to obtain the molten magnesium.

(3) Addition of alloying elements Zn, Sn and Mn: 20 kg of pure Zn ingot, 2 kg of pure Sn ingot and 40 kg of Mg-5% Mn intermediate alloy are preheated to 160-220 ℃ by adopting a preheating furnace. Respectively immersing 20 kg of preheated pure Zn ingot, 2 kg of pure Sn ingot and 40 kg of Mg-5% Mn intermediate alloy into the magnesium melt in the step (2), controlling the temperature of the magnesium melt at 680-830 ℃, and preserving the temperature for 15-30 minutes at 690-830 ℃ after the pure Zn ingot, the pure Sn ingot and the Mg-5% Mn intermediate alloy are completely melted, so that all alloy elements are uniformly distributed in the magnesium melt; and then, casting a spectrum sample, carrying out stokehole analysis, and if the components and the content are unqualified, feeding and adjusting the components to reach the component content of the magnesium alloy to obtain a magnesium alloy melt.

(4) Casting a billet: and (4) conveying the magnesium alloy melt in the step (3) to a crystallizer by using a melt transfer pump, and carrying out semi-continuous casting to prepare a billet for rolling and processing the plate.

(5) Homogenizing heat treatment, plate rolling deformation processing: and (4) carrying out homogenization heat treatment on the billet prepared in the step (4), wherein the heating temperature is 325-365 ℃, the heat preservation time is 3-6 hours, and directly rolling and deforming the billet subjected to homogenization heat treatment into a plate by using a plate rolling mill after discharging.

(6) Pre-stretching the plate: and (3) pre-stretching the plate prepared in the step (5) by adopting a stretcher at room temperature with the deformation of 2-5%.

(7) Aging heat treatment: and (3) carrying out aging heat treatment on the plate prepared in the step (6) by using an aging heat treatment furnace, heating for 125-160 ℃, keeping the temperature for 5-50 hours, and then cooling to room temperature to obtain the Mg-2Zn-0.2Sn-0.2Mn magnesium alloy.

The Mg-2Zn-0.2Sn-0.2Mn magnesium alloy prepared by the embodiment has the thermal conductivity of about 140W (m.K) at the temperature of 20 DEG C^-1The fracture toughness is 15-17 MPa.m^1/2。

Example 21000 kg of a Mg-5Zn-2Sn-1Mn heat-conductive fatigue-resistant magnesium alloy (i.e., the magnesium alloy comprises 5% of Zn, 2% of Sn and 1% of Mn, and the balance of Mg) and a method for preparing a bar, a pipe or a section by extrusion.

(1) Preparing raw materials: 730 kg of pure magnesium ingot, 50 kg of pure Zn ingot, 20 kg of pure Sn ingot and 200 kg of Mg-5% Mn intermediate alloy are prepared.

(2) Melting a pure magnesium ingot: 730 kilograms of pure magnesium ingots are stacked in a melting crucible in a mode of being as compact as possible, sulfur powder is uniformly scattered on the bottom of the crucible and the surface of the pure magnesium ingots, and the amount of the sulfur powder is based on the fact that oxygen in the crucible can be completely converted into sulfur dioxide after oxidation combustion. Sealing the crucible by using a crucible cover, controlling the heating temperature to be 680-830 ℃, completely melting all pure magnesium ingots under the protection of sulfur dioxide and nitrogen gas remained after combustion, opening the crucible cover, cleaning floating slag on the surface of the molten magnesium, uniformly spraying No. 2 fusing agent or magnesium-smelting covering agent on the surface of the molten magnesium, and preventing the magnesium from being combusted to obtain the molten magnesium.

(3) Addition of alloying elements Zn, Sn and Mn: 50 kg of pure Zn ingot, 20 kg of pure Sn ingot and 200 kg of Mg-5% Mn intermediate alloy are preheated to 160-220 ℃ by adopting a preheating furnace. Respectively immersing 50 kg of preheated pure Zn ingot, 20 kg of pure Sn ingot and 200 kg of Mg-5% Mn intermediate alloy into the magnesium melt in the step (2), controlling the temperature of the magnesium melt at 680-830 ℃, and preserving the heat at 690-830 ℃ for 15-30 minutes after the pure Zn ingot, the pure Sn ingot and the Mg-5% Mn intermediate alloy are completely melted, so that all alloy elements are uniformly distributed in the magnesium melt; and then, casting a spectrum sample, carrying out stokehole analysis, and if the components and the content are unqualified, feeding and adjusting the components to reach the component content of the magnesium alloy to obtain a magnesium alloy melt.

(4) Casting a billet: and (3) conveying the magnesium alloy melt into a crystallizer by using a melt transfer pump, and carrying out semi-continuous casting to prepare a billet for extrusion deformation processing of bars, pipes or profiles.

(5) Homogenizing heat treatment, and extruding and deforming the bar, the pipe or the section: and (5) carrying out homogenization heat treatment on the billet prepared in the step (4), heating for 335-385 ℃, keeping the temperature for 20-50 hours, and processing the billet into a bar, a pipe or a section by adopting extrusion deformation after discharging.

(6) Pre-stretching a bar, a pipe or a section: and (3) performing pre-stretching treatment on the bar, the pipe or the section prepared in the step (5) at room temperature by using a stretcher, wherein the deformation of the bar, the pipe or the section is 2-5%.

(7) Aging heat treatment: and (3) carrying out aging heat treatment on the bar, the pipe or the section prepared in the step (6) by using an aging heat treatment furnace, heating for 135-180 ℃, keeping the temperature for 5-50 hours, and then cooling to room temperature to obtain the Mg-5Zn-2Sn-1Mn magnesium alloy.

The Mg-5Zn-2Sn-1Mn magnesium alloy prepared in the embodiment has the thermal conductivity of about 125W. (m.K) at the temperature of 20 DEG C^-1The fracture toughness is 17-20 MPa.m^1/2。

Example 31000 kg of a heat-conductive, fatigue-resistant Mg-4Zn-1.5Sn-0.8Mn alloy (i.e., a magnesium alloy having the composition of 4% Zn, 1.5% Sn, 0.8% Mn, and the balance Mg) and a method for forging a part thereof.

(1) Preparing raw materials: 785 jin of pure magnesium ingot, 40 kg of pure Zn ingot, 15 kg of pure Sn ingot and 160 kg of Mg-5% Mn intermediate alloy are prepared.

(2) Melting a pure magnesium ingot: 785 kg of pure magnesium ingot is stacked in a melting crucible in a mode of being as compact as possible, sulfur powder is uniformly scattered on the bottom of the crucible and the surface of the pure magnesium ingot, and the amount of the sulfur powder is based on the fact that oxygen in the crucible can be completely converted into sulfur dioxide after oxidation combustion. Sealing the crucible by using a crucible cover, controlling the heating temperature to be 680-830 ℃, completely melting all pure magnesium ingots under the protection of sulfur dioxide and nitrogen gas remained after combustion, opening the crucible cover, cleaning floating slag on the surface of the molten magnesium, uniformly spraying No. 2 fusing agent or magnesium-smelting covering agent on the surface of the molten magnesium, and preventing the magnesium from being combusted to obtain the molten magnesium.

(3) Addition of alloying elements Zn, Sn and Mn: and preheating 40 kg of pure Zn ingot, 15 kg of pure Sn ingot and 160 kg of Mg-5% Mn intermediate alloy to 160-220 ℃ by adopting a preheating furnace. Respectively immersing 40 kg of preheated pure Zn ingot, 15 kg of pure Sn ingot and 160 kg of Mg-5% Mn intermediate alloy into the magnesium melt in the step (2), controlling the temperature of the magnesium melt at 680-830 ℃, and preserving the heat at 690-830 ℃ for 15-30 minutes after the pure Zn ingot, the pure Sn ingot and the Mg-5% Mn intermediate alloy are completely melted, so that all alloy elements are uniformly distributed in the magnesium melt; and then, casting a spectrum sample, carrying out stokehole analysis, and if the components and the content are unqualified, feeding and adjusting the components to reach the component content of the magnesium alloy to obtain a magnesium alloy melt.

(4) Casting a billet: and (4) casting the magnesium alloy melt obtained in the step (3) into a sand casting die by using a melt transfer pump, and solidifying into a billet for subsequent forging deformation processing.

(5) Homogenizing heat treatment and forging deformation processing of parts: and (4) carrying out homogenization heat treatment on the billet prepared in the step (4), heating for 330-375 ℃, keeping the temperature for 18-24 hours, and directly forging and deforming the billet subjected to homogenization heat treatment into a part by using a forging press after discharging.

(6) Aging heat treatment: and (3) carrying out aging heat treatment on the forged part prepared in the step (5) by using an aging heat treatment furnace, heating for 135-175 ℃, keeping the temperature for 10-14 hours, and then cooling to room temperature to obtain the Mg-4Zn-1.5Sn-0.8Mn magnesium alloy.

The Mg-4Zn-1.5Sn-0.8Mn magnesium alloy prepared by the embodiment has the thermal conductivity of about 130W (m.K) at the temperature of 20 DEG C^-1The fracture toughness is 16-19 MPa.m^1/2。

Example 41000 kg of Mg-3Zn-0.5Sn-0.6Mn heat-conductive fatigue-resistant magnesium alloy (i.e., the magnesium alloy comprises 3% of Zn, 0.5% of Sn, 0.6% of Mn, and the balance of Mg) and a method for preparing a tube, a bar or a wire by extrusion and drawing.

(1) Preparing raw materials: 845 kg of pure magnesium ingot, 30 kg of pure Zn ingot, 5 kg of pure Sn ingot and 120 kg of Mg-5% Mn master alloy are prepared.

(2) Melting a pure magnesium ingot: 845 kg of pure magnesium ingot is stacked in a melting crucible in a mode of being as compact as possible, sulfur powder is uniformly scattered on the bottom of the crucible and the surface of the pure magnesium ingot, and the amount of the sulfur powder is based on the fact that oxygen in the crucible can be completely converted into sulfur dioxide after oxidation combustion. And (2) sealing the crucible by using a crucible cover, controlling the heating temperature to be 680-830 ℃, completely melting all pure magnesium ingots under the protection of sulfur dioxide and residual nitrogen after combustion, opening the crucible cover, cleaning floating slag on the surface of the molten magnesium, uniformly spraying No. 2 flux or a covering agent for smelting magnesium on the surface of the molten magnesium, and preventing the magnesium from burning to obtain the molten magnesium.

(3) Addition of alloying elements Zn, Sn and Mn: 30 kg of pure Zn ingot, 5 kg of pure Sn ingot and 120 kg of Mg-5% Mn intermediate alloy are preheated to 160-220 ℃ by adopting a preheating furnace. Respectively immersing 30 kg of preheated pure Zn ingot, 5 kg of pure Sn ingot and 120 kg of Mg-5% Mn intermediate alloy into the magnesium melt in the step (2), controlling the temperature of the magnesium melt at 680-830 ℃, and preserving the temperature for 15-30 minutes at 690-830 ℃ after the pure Zn ingot, the pure Sn ingot and the Mg-5% Mn intermediate alloy are completely melted, so that all alloy elements are uniformly distributed in the magnesium melt; and then casting a spectrum sample, performing stokehole analysis, and if the components and the content are not qualified, feeding materials to adjust the components and the content of the magnesium alloy to obtain a magnesium alloy melt.

(4) Casting a billet: and (4) casting the magnesium alloy melt obtained in the step (3) into a fully preheated metal mold casting die by using a melt transfer pump, and solidifying into a billet for subsequent extrusion deformation processing.

(5) Homogenizing heat treatment, extruding and drawing deformation processing of pipes, bars or wires: and (3) carrying out homogenization heat treatment on the billet prepared in the step (4), heating for 335-355 ℃, keeping the temperature for 18-21 hours, directly extruding and deforming the billet subjected to homogenization heat treatment by using an extruder after discharging to form a pipe, a bar or a wire, and then drawing and deforming the pipe, the bar or the wire by using a drawing machine to form a pipe, a bar or a wire with a smaller diameter.

(6) Pre-stretching the pipe, the bar or the wire: and (3) performing pre-stretching treatment on the bar, the pipe, the section or the wire rod prepared in the step (5) at room temperature by adopting a stretcher, wherein the deformation of the bar, the pipe, the section or the wire rod is 0.5-2%.

(7) Aging heat treatment: and (3) carrying out aging heat treatment on the pipe, the bar or the wire rod prepared in the step (6) by using an aging heat treatment furnace, heating for 135-160 ℃, keeping the temperature for 12-36 hours, and then cooling to room temperature to obtain the Mg-3Zn-0.5Sn-0.6Mn magnesium alloy.

The Mg-3Zn-0.5Sn-0.6Mn magnesium alloy prepared by the embodiment is at the temperature of 20 DEG CThermal conductivity of about 135W. (m.k)^-1The fracture toughness is 15-18 MPa.m^1/2。

EXAMPLE 51000 kg of a Mg-7Zn-5Sn-0.5Mn heat-conductive fatigue-resistant magnesium alloy (i.e., the magnesium alloy contains 7% of Zn, 5% of Sn, 0.5% of Mn, and the balance of Mg) and a method for producing an extrusion-cast part thereof.

(1) Preparing raw materials: 780 kg of pure magnesium ingot, 70 kg of pure Zn ingot, 50 kg of pure Sn ingot and 100 kg of Mg-5% Mn intermediate alloy are prepared.

(2) Melting a pure magnesium ingot: 780 kg of pure magnesium ingot is stacked in a melting crucible in a mode of being as compact as possible, sulfur powder is uniformly scattered on the bottom of the crucible and the surface of the pure magnesium ingot, and the amount of the sulfur powder is based on the fact that oxygen in the crucible can be completely converted into sulfur dioxide after oxidation combustion. And (2) sealing the crucible by using a crucible cover, controlling the heating temperature to be 680-830 ℃, completely melting all pure magnesium ingots under the protection of sulfur dioxide and residual nitrogen after combustion, opening the crucible cover, cleaning floating slag on the surface of the molten magnesium, uniformly spraying No. 2 flux or a covering agent for smelting magnesium on the surface of the molten magnesium, and preventing the magnesium from burning to obtain the molten magnesium.

(3) Adding alloy elements Zn, Sn and Mn: 70 kg of pure Zn ingot, 50 kg of pure Sn ingot and 100 kg of Mg-5% Mn intermediate alloy are preheated to 160-220 ℃ by adopting a preheating furnace. Respectively immersing 70 kg of preheated pure Zn ingot, 50 kg of pure Sn ingot and 100 kg of Mg-5% Mn intermediate alloy into the magnesium melt in the step (3), controlling the temperature of the magnesium melt at 680-830 ℃, and preserving the temperature for 15-30 minutes at 690-830 ℃ after the pure Zn ingot, the pure Sn ingot and the Mg-5% Mn intermediate alloy are completely melted, so that all alloy elements are uniformly distributed in the magnesium melt; and then, casting a spectrum sample, carrying out stokehole analysis, and if the components and the content are unqualified, feeding and adjusting the components to reach the component content of the magnesium alloy to obtain a magnesium alloy melt.

(4) Extrusion casting forming: controlling the temperature of the magnesium alloy melt in the step (3) to be 705-755 ℃, and preserving the heat; according to the weight of the casting, the magnesium alloy melt is cast into a pressure chamber of an extrusion casting machine in batches by a melt quantitative transfer pump, and the casting is extruded and cast into the casting.

(5) Solution heat treatment: and (3) carrying out solution heat treatment on the extrusion casting part in the step (4) by using a solution heat treatment furnace, wherein the heating time is 370-450 ℃, and the heat preservation time is 17-36 hours.

(6) Aging heat treatment: and (3) carrying out aging heat treatment on the extrusion casting part subjected to the solution heat treatment in the step (5) by using an aging heat treatment furnace, heating at 140-200 ℃, keeping the temperature for 12-50 hours, and then cooling to room temperature to obtain the Mg-7Zn-5Sn-0.5Mn magnesium alloy.

The Mg-7Zn-5Sn-0.5Mn magnesium alloy prepared in the embodiment has the thermal conductivity of about 115W. (m.K) at the temperature of 20 DEG C^-1The fracture toughness is 13-16 MPa.m^1/2。

Example 61000 kg of Mg-5Zn-3Sn-0.4Mn, a heat-conductive fatigue-resistant magnesium alloy (i.e., the magnesium alloy comprises 5% Zn, 3% Sn, 0.4% Mn, and the balance Mg), and a method for producing a low-pressure cast part thereof.

(1) Preparing raw materials: 840 kg pure magnesium ingot, 50 kg pure Zn ingot, 30 kg pure Sn ingot, 80 kg Mg-5% Mn intermediate alloy.

(2) Melting a pure magnesium ingot: 840 kg of pure magnesium ingot is stacked in a melting crucible in a mode of being as compact as possible, sulfur powder is uniformly scattered on the bottom of the crucible and the surface of the pure magnesium ingot, and the amount of the sulfur powder is based on that oxygen in the crucible can be completely converted into sulfur dioxide after oxidation combustion. Sealing the crucible by using a crucible cover, controlling the heating temperature to be 680-830 ℃, completely melting all pure magnesium ingots under the protection of sulfur dioxide and nitrogen gas remained after combustion, opening the crucible cover, cleaning floating slag on the surface of the molten magnesium, uniformly spraying No. 2 fusing agent or magnesium-smelting covering agent on the surface of the molten magnesium, and preventing the magnesium from being combusted to obtain the molten magnesium.

(3) Addition of alloying elements Zn, Sn and Mn: 50 kg of pure Zn ingot, 30 kg of pure Sn ingot and 80 kg of Mg-5% Mn intermediate alloy are preheated to 160-220 ℃ by adopting a preheating furnace. Respectively immersing 50 kg of preheated pure Zn ingot, 30 kg of pure Sn ingot and 80 kg of Mg-5% Mn intermediate alloy into the magnesium melt, controlling the temperature of the magnesium melt at 680-830 ℃, and preserving the temperature at 690-830 ℃ for 15-30 minutes after the pure Zn ingot, the pure Sn ingot and the Mg-5% Mn intermediate alloy are completely melted, so that all alloy elements are uniformly distributed in the magnesium melt; and then, casting a spectrum sample, carrying out stokehole analysis, and if the components and the content are unqualified, feeding and adjusting the components to reach the component content of the magnesium alloy to obtain a magnesium alloy melt.

(4) And (3) low-pressure casting forming: and (4) transferring the magnesium alloy melt in the step (3) to a crucible of a low-pressure casting machine holding furnace by using a melt transfer pump, controlling the temperature of the magnesium alloy melt at 715-735 ℃, preserving the heat, and casting into a casting at low pressure.

(5) Solution heat treatment: and (5) carrying out solution heat treatment on the casting cast in the step (4) at low pressure by adopting a solution heat treatment furnace, wherein the heating temperature is 395-475 ℃, and the heat preservation time is 12-15 hours.

(6) Aging heat treatment: and (3) carrying out aging heat treatment on the low-pressure cast part subjected to the solution heat treatment in the step (5) by using an aging heat treatment furnace, heating at 140-180 ℃, keeping the temperature for 5-36 hours, and then cooling to room temperature to obtain the Mg-5Zn-3Sn-0.4Mn magnesium alloy.

The Mg-5Zn-3Sn-0.4Mn magnesium alloy prepared in the embodiment has the thermal conductivity of about 120W. (m.K) at the temperature of 20 DEG C^-1And the fracture toughness is 12-15 MPa.m^1/2。

Example 71000 kg of a heat-conducting fatigue-resistant Mg-4Zn-2Sn-0.6Mn magnesium alloy (i.e., the magnesium alloy comprises 4% Zn, 2% Sn, 0.6% SMn, and the balance Mg) and a method for making sand-cast parts thereof.

(1) Preparing raw materials: 820 kg of pure magnesium ingot, 40 kg of pure Zn ingot, 20 kg of pure Sn ingot and 120 kg of Mg-5% Mn intermediate alloy.

(2) Melting a pure magnesium ingot: 820 kg of pure magnesium ingot is stacked in a melting crucible in a mode of being as compact as possible, sulfur powder is uniformly scattered on the bottom of the crucible and the surface of the pure magnesium ingot, and the amount of the sulfur powder is based on the fact that oxygen in the crucible can be completely converted into sulfur dioxide after oxidation combustion. And (2) sealing the crucible by using a crucible cover, controlling the heating temperature to be 680-830 ℃, completely melting all pure magnesium ingots under the protection of sulfur dioxide and residual nitrogen after combustion, opening the crucible cover, cleaning floating slag on the surface of the molten magnesium, uniformly spraying No. 2 flux or a covering agent for smelting magnesium on the surface of the molten magnesium, and preventing the magnesium from burning to obtain the molten magnesium.

(3) Addition of alloying elements Zn, Sn and Mn: preheating 40 kg of pure Zn ingot, 20 kg of pure Sn ingot and 120 kg of Mg-5% Mn intermediate alloy to 160-220 ℃ by adopting a preheating furnace. Respectively immersing 40 kg of preheated pure Zn ingot, 20 kg of pure Sn ingot and 120 kg of Mg-5% Mn intermediate alloy into the magnesium melt in the step (2), controlling the temperature of the magnesium melt at 680-830 ℃, and preserving the heat at 690-830 ℃ for 15-30 minutes after the pure Zn ingot, the pure Sn ingot and the Mg-5% Mn intermediate alloy are completely melted, so that all alloy elements are uniformly distributed in the magnesium melt; and then, casting a spectrum sample, carrying out stokehole analysis, and if the components and the content are unqualified, feeding and adjusting the components to reach the component content of the magnesium alloy to obtain a magnesium alloy melt.

(4) Sand mold casting and forming: and (4) transferring the magnesium alloy melt in the step (3) to a crucible of a heat preservation furnace of a sand casting machine by using a melt transfer pump, controlling the temperature of the magnesium alloy melt at 705-725 ℃, preserving the heat, and sand casting to obtain a casting.

(5) Solution heat treatment: and (3) carrying out solution heat treatment on the casting cast by the sand mold in the step (4) by using a solution heat treatment furnace, wherein the heating temperature is 370-430 ℃, and the heat preservation time is 16-50 hours.

(6) Aging heat treatment: and (3) carrying out aging heat treatment on the sand mold casting part subjected to the solution heat treatment in the step (5) by using an aging heat treatment furnace, wherein the heating temperature is 125-170 ℃, the heat preservation time is 3-5 hours, and then cooling to room temperature to obtain the Mg-4Zn-2Sn-0.6Mn magnesium alloy.

The Mg-4Zn-2Sn-0.6Mn magnesium alloy prepared by the embodiment has the thermal conductivity of about 125W. (m.K) at the temperature of 20 DEG C^-1The fracture toughness is 13-16 MPa.m^1/2。

Example 81000 kg of a heat-conductive fatigue-resistant Mg-5Zn-1Sn-0.3Mn alloy (i.e., the magnesium alloy comprises 5% Zn, 1% Sn, 0.3% Mn, and the balance Mg) and a method for preparing a metal mold casting component thereof.

(1) Preparing raw materials: 880 kg of pure magnesium ingot, 50 kg of pure Zn ingot, 10 kg of pure Sn ingot and 60 kg of Mg-5% Mn master alloy.

(2) Melting a pure magnesium ingot: stacking 880 kg of pure magnesium ingots in a melting crucible in a mode as compact as possible, and uniformly scattering sulfur powder on the bottom of the crucible and the surface of the pure magnesium ingots, wherein the amount of the sulfur powder is based on the fact that oxygen in the crucible can be completely converted into sulfur dioxide after oxidation combustion. And (2) sealing the crucible by using a crucible cover, controlling the heating temperature to be 680-830 ℃, completely melting all pure magnesium ingots under the protection of sulfur dioxide and residual nitrogen after combustion, opening the crucible cover, cleaning floating slag on the surface of the molten magnesium, uniformly spraying No. 2 flux or a covering agent for smelting magnesium on the surface of the molten magnesium, and preventing the magnesium from burning to obtain the molten magnesium.

(3) Addition of alloying elements Zn, Sn and Mn: 50 kg of pure Zn ingot, 10 kg of pure Sn ingot and 60 kg of Mg-5% Mn intermediate alloy are preheated to 160-220 ℃ by adopting a preheating furnace. Respectively immersing 50 kg of preheated pure Zn ingot, 10 kg of pure Sn ingot and 60 kg of Mg-5% Mn intermediate alloy into the magnesium melt in the step (2), controlling the temperature of the magnesium melt at 680-830 ℃, and preserving the heat at 690-830 ℃ for 15-30 minutes after the pure Zn ingot, the pure Sn ingot and the Mg-5% Mn intermediate alloy are completely melted, so that all alloy elements are uniformly distributed in the magnesium melt; and then, casting a spectrum sample, carrying out stokehole analysis, and if the components and the content are unqualified, feeding and adjusting the components to reach the component content of the magnesium alloy to obtain a magnesium alloy melt.

(4) Metal mold casting and forming: and (4) transferring the magnesium alloy melt in the step (3) to a crucible of a heat preservation furnace of a metal mold casting machine by using a melt transfer pump, controlling the temperature of the magnesium alloy melt at 720-740 ℃, preserving the heat, and casting the metal mold into a casting.

(5) Solution heat treatment: and (3) carrying out solution heat treatment on the casting cast by the metal mold in the step (4) by using a solution heat treatment furnace, wherein the heating time is 350-435 ℃, and the heat preservation time is 8-32 hours.

(6) Aging heat treatment: and (3) carrying out aging heat treatment on the metal mold casting part subjected to the solution heat treatment in the step (5) by using an aging heat treatment furnace, heating for 140-170 ℃, keeping the temperature for 6-48 hours, and then cooling to room temperature to obtain the Mg-5Zn-1Sn-0.3Mn magnesium alloy.

The Mg-5Zn-1Sn-0.3Mn magnesium alloy prepared in the embodiment has the thermal conductivity of about 125W. (m.K) at the temperature of 20 DEG C^-1The fracture toughness is 13-16 MPa.m^1/2。

Example 91000 kg of a Mg-6Zn-4Sn-0.4Mn heat-conductive fatigue-resistant magnesium alloy (i.e., the magnesium alloy contains 6% Zn, 4% Sn, and 0.4% Mn, with the balance being Mg) and a method for producing a die-cast part thereof.

(1) Preparing raw materials: 820 kg of pure magnesium ingot, 60 kg of pure Zn ingot, 40 kg of pure Sn ingot and 80 kg of Mg-5% Mn intermediate alloy.

(2) Melting a pure magnesium ingot: 820 kg of pure magnesium ingot is stacked in a melting crucible in a mode of being as compact as possible, sulfur powder is uniformly scattered on the bottom of the crucible and the surface of the pure magnesium ingot, and the amount of the sulfur powder is based on the fact that oxygen in the crucible can be completely converted into sulfur dioxide after oxidation combustion. Sealing the crucible by using a crucible cover, controlling the heating temperature to be 680-830 ℃, completely melting all pure magnesium ingots under the protection of sulfur dioxide and nitrogen gas remained after combustion, opening the crucible cover, cleaning floating slag on the surface of the molten magnesium, uniformly spraying No. 2 fusing agent or magnesium-smelting covering agent on the surface of the molten magnesium, and preventing the magnesium from being combusted to obtain the molten magnesium.

(3) Addition of alloying elements Zn, Sn and Mn: 60 kg of pure Zn ingot, 40 kg of pure Sn ingot and 80 kg of Mg-5% Mn intermediate alloy are preheated to 160-220 ℃ by adopting a preheating furnace. Respectively immersing 60 kg of preheated pure Zn ingot, 40 kg of pure Sn ingot and 80 kg of Mg-5% Mn intermediate alloy into the magnesium melt in the step (2), controlling the temperature of the magnesium melt to be 680-830 ℃, and preserving heat for 15-30 minutes at 690-830 ℃ after the pure Zn ingot, the pure Sn ingot and the Mg-5% Mn intermediate alloy are completely melted, so that all alloy elements are uniformly distributed in the magnesium melt; and then, casting a spectrum sample, carrying out stokehole analysis, and if the components and the content are unqualified, feeding and adjusting the components to reach the component content of the magnesium alloy to obtain a magnesium alloy melt.

(4) Die-casting and forming: controlling the temperature of the magnesium alloy melt in the step (3) to be 685-720 ℃, and preserving heat; according to the weight of the casting, the magnesium alloy melt is poured into a pressure chamber of a cold chamber die casting machine in batches by a melt quantitative transfer pump to be die-cast into the casting.

(5) Solution heat treatment: and (3) carrying out solution heat treatment on the casting die-cast in the step (4) by using a solution heat treatment furnace, wherein the heating time is 350-480 ℃, and the heat preservation time is 8-24 hours.

(6) Aging heat treatment: and (3) carrying out aging heat treatment on the die-cast formed part subjected to the solution heat treatment in the step (5) by using an aging heat treatment furnace, heating for 140-170 ℃, keeping the temperature for 6-48 hours, and then cooling to room temperature to obtain the Mg-6Zn-4Sn-0.4Mn magnesium alloy.

The Mg-6Zn-4Sn-0.4Mn magnesium alloy prepared by the embodiment has the thermal conductivity of about 115W. (m.K) at the temperature of 20 DEG C^-1The fracture toughness is 13-16 MPa.m^1/2。

The above description is only a preferred embodiment of the present application and should not be taken as limiting the present application, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. The magnesium alloy with heat conduction and fatigue resistance is characterized by comprising the following components in percentage by weight: 6-7% of Zn, 0.5-3% of Sn, 0.5-0.8% of Mn and the balance of Mg, wherein the thermal conductivity of the magnesium alloy is 105-140W (m.K)^-1The fracture toughness is 12-20 MPa.m^1/2The magnesium alloy contains MgZn phase and alpha Mg₂A Sn phase and a beta-Mn solid solution phase;

the preparation method of the heat-conducting anti-fatigue magnesium alloy comprises the following steps:

(2) melting a pure magnesium ingot: stacking the pure magnesium ingots weighed in the step (1) in a melting crucible of a melting furnace in a compact manner, completely melting under the protection of protective gas or No. 2 flux or magnesium smelting covering agent, controlling the temperature to be 680-830 ℃, cleaning floating slag on the surface of the molten liquid, and uniformly scattering No. 2 flux or magnesium smelting covering agent on the surface of the molten liquid to obtain magnesium molten liquid;

(3) addition of alloying elements Zn, Sn and Mn: immersing the preheated pure Zn ingot, pure Sn ingot and Mg-Mn intermediate alloy ingot into the magnesium solution in the step (2), heating, preserving heat, casting a spectrum sample, carrying out stokehole analysis, and adding materials until the weight percentage of the components of the magnesium alloy is 6-7% Zn, 0.5-3% Sn, 0.5-0.8% Mn and the balance Mg, so as to obtain the magnesium alloy solution;

(5) aging heat treatment: carrying out aging heat treatment on the part or the forging prepared in the step (4) to obtain magnesium alloy;

in the step (2), the process of complete melting under the protection of the protective gas comprises the following steps: before stacking the pure magnesium ingot in a melting crucible, uniformly scattering sulfur powder at the bottom of the melting crucible, stacking the pure magnesium ingot in the melting crucible, uniformly scattering sulfur powder on the surface of the pure magnesium ingot, sealing the melting crucible by using a crucible cover, and controlling the heating temperature to be 680-830 ℃ so that all the pure magnesium ingots are completely melted under the protection of sulfur dioxide and residual nitrogen after combustion;

in the step (4), the temperature for carrying out solution heat treatment on the casting is 325-500 ℃, and the heat preservation time is 5-36 hours;

in the step (4), the temperature for carrying out homogenization heat treatment on the billet is 325-500 ℃, and the heat preservation time is 5-50 hours;

in the step (5), the temperature of the aging heat treatment is 125-200 ℃, and the heat preservation time is 5-50 hours.

2. A heat-conducting fatigue-resisting magnesium alloy as claimed in claim 1, wherein in the step (2), the No. 2 flux is composed of 30-65% by weight of magnesium chloride and 35-70% by weight of potassium chloride, and the magnesium-smelting covering agent is composed of 30-63% by weight of magnesium chloride and 35-68% by weight of potassium chloride and 1-5% by weight of sulfur.