Novel high-strength and high-thermal-conductivity magnesium alloy material and preparation method thereof

Abstract

The invention discloses a novel high-strength and high-thermal-conductivity magnesium alloy material which comprises the following components in percentage by mass: 0.8-4.4% of Zn, 0.1-0.3% of Cu, 0.1-0.3% of Ca, 0.3-0.5% of Zr and the balance of Mg and inevitable impurities. The invention also provides a preparation method. The preparation method comprises the following steps: S1, preparing the raw materials according to the proportion; s2, a refining agent is prepared, then the raw materials prepared in the step S1 are melted in sequence and then stand for a period of time, then the raw materials are mixed with the refining agent, Mg alloy melt is obtained, and the temperature of the Mg alloy melt is controlled within a specific range; s3, casting the Mg alloy melt in the S2 into a metal mold, taking out the Mg alloy melt after the Mg alloy melt is solidified, slowly immersing the Mg alloy melt into water, and cooling to obtain an Mg alloy cast ingot; s4, preserving the heat of the Mg alloy cast ingot prepared in S3 for a period of time at a specific temperature, and then slowly immersing the Mg alloy cast ingot in water for cooling to obtain a T4-state Mg alloy cast ingot; and S5, the T4-state Mg alloy cast ingot obtained in the step S4 is subjected to heat preservation for a period of time at the specific temperature and then is subjected to air cooling, and a T6-state Mg alloy cast ingot, namely the magnesium alloy material, is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium alloys, and in particular to a new type of high-strength and high-thermal conductivity magnesium alloy material and a preparation method thereof. Background Art

[0002] In recent years, the density of electronic components on integrated circuits has become higher and higher, resulting in more and more heat released by components per unit time and per unit area, which has greatly restricted the further development of the 3C field. Therefore, 3C heat dissipation components have gradually developed. However, thermal conductivity is not the only requirement for manufacturing 3C heat dissipation components today; the general trend of energy saving and weight reduction requires that heat dissipation components need to use materials with lower density, so that heat dissipation components can have sufficient heat dissipation capacity while having lighter weight. As the lightest metal structural material, Mg has good thermal conductivity, which makes it have great potential to become a raw material for manufacturing heat dissipation components.

[0003] A Chinese invention with authorization announcement number CN105463280B discloses a magnesium alloy with high thermal conductivity and a preparation method thereof, which, by adding rare earth elements and other alloying elements of specific content and composition, enables the magnesium alloy to have the strength of traditional magnesium alloys and also improve the thermal conductivity of the magnesium alloy; however, the above patent, like most existing research, often focuses on high thermal conductivity in the research of thermal conductive magnesium alloys, but does not balance thermal conductivity and mechanical properties, making it difficult to meet the strength requirements for manufacturing heat dissipation components; and for the research on a few magnesium alloys that can take into account both thermal conductivity and mechanical properties, the thermal conductivity and mechanical properties of the magnesium alloys finally obtained are not excellent. Summary of the invention

[0004] In view of the deficiencies in the prior art, the invention provides a new type of high-strength and high-thermal conductivity magnesium alloy material and a preparation method thereof, which solves the problem in the prior art that magnesium alloys cannot simultaneously take into account good thermal conductivity and mechanical properties.

[0005] A new type of high-strength and high-thermal conductivity magnesium alloy material comprises the following components, calculated by mass percentage: Zn0.8-4.4%, Cu0.1-0.3%, Ca0.1-0.3% and Zr0.3-0.5%, and the balance is Mg and inevitable impurities.

[0006] The present invention also provides a method for preparing a novel high-strength and high-thermal-conductivity magnesium alloy material, comprising the following steps:

[0007] S1. Prepare raw materials according to the ratio;

[0008] S2. preparing a refining agent, and then melting the raw materials prepared in S1 in sequence, standing for a period of time, and then mixing with the refining agent to obtain a Mg alloy melt, and controlling the temperature of the Mg alloy melt within a specific range;

[0009] S3. The Mg alloy melt in S2 is cast into a metal mold, and after the Mg alloy melt solidifies, it is taken out and slowly immersed in water, and after cooling, a Mg alloy ingot is obtained;

[0010] S4. The Mg alloy ingot obtained in S3 was kept at a specific temperature for a period of time, and then slowly immersed in water and cooled to obtain a Mg alloy ingot in the T4 state;

[0011] S5. The T4 state Mg alloy ingot obtained in S4 is kept at a specific temperature for a period of time and then air-cooled to obtain a T6 state Mg alloy ingot, that is, the magnesium alloy material.

[0012] Preferably, in step S1, the raw materials are added in the form of pure Mg, pure Zn, pure Cu, Mg-30wt.% Zr and Mg-25wt.% Ca, respectively, and the above five raw materials need to be kept at 200° C. for 30 minutes.

[0013] Preferably, in step S2, the steps of melting the five raw materials and mixing them with the refining agent are specifically as follows:

[0014] S21. After the pure Mg and pure Cu are kept at 400 ° C for at least 30 min, the temperature is raised to 720 ° C-750 ° C for melting, and then kept warm for 20-40 min. In the process, a mixed gas of CO2: SF6 = 99:1 is used as a protective gas, and the gas flow rate is 2L / min;

[0015] S22. Pure Zn, Mg-30wt.% Zr and Mg-25wt.% Ca are added to the melt of step S21 and stirred for 1-3min to obtain a Mg alloy melt, and then the Mg alloy melt is kept at 720-750°C for 30min;

[0016] S23. The refining agent is added to the Mg alloy melt obtained in step S22, stirred for 1-3min and then kept warm for 30min;

[0017] S24. The Mg alloy melt mixed with the refining agent in S23 is cooled twice at 700-720°C and 685-700°C for use.

[0018] Preferably, in step S2, the refining agent is configured as MgCl2:KCl:BaCl2:CaF2:NaCl:CaCl2:MgO=85:72:14:10:8:8:3, and the amount used is 1% of the mass of the Mg alloy melt.

[0019] Preferably, in step S3, the metal mold needs to be kept at 200° C. for more than 30 minutes before casting and cooled to room temperature in air.

[0020] Preferably, in step S3, a mixed gas of CO2:SF6=99:1 is used as the protective gas during the casting process, the gas flow rate is 2 L / min, and the Mg alloy melt is continuously purged.

[0021] Preferably, in step S4, the Mg alloy ingot is kept at 450-500° C. for 5-360 min.

[0022] Preferably, in step S4, during the heat preservation process, carbon powder is used to wrap the Mg alloy ingot.

[0023] Preferably, in step S5, the T4 state Mg alloy ingot is kept at 150-250° C. for 6-8 hours.

[0024] Compared with the prior art, the invention has the following beneficial effects:

[0025] 1. The present invention adopts Cu, Ca, and Zr, which have excellent strengthening effects and do not significantly reduce thermal conductivity when added in low amounts, and adds Zn to design the Mg alloy, so that the obtained alloy has more excellent comprehensive thermal conductivity and mechanical properties: through reasonable composition regulation, the alloy elements will promote each other's precipitation, and can form a structure composed of α-Mg, Mg(Zn,Cu)2 and Ca2Mg6Zn3, so that the alloy elements in the matrix consume each other, achieving the purpose of significantly improving the mechanical properties without significantly deteriorating the thermal conductivity, overcoming the inverted relationship between strength and thermal conductivity, and far exceeding the performance of most high-strength and high-thermal-conductivity Mg alloys in the prior art.

[0026] 2. After casting, the present invention performs solid solution and aging treatment on the Mg alloy ingot again. During the solid solution process, a solid solution structure with solid solution strengthening effect can be formed in the Mg alloy, which can effectively improve the plasticity and toughness of the Mg alloy, eliminate the intergranular brittleness in the alloy, improve the creep resistance, and eliminate the microstructure and performance heterogeneity of the metal material after cold deformation; and the aging treatment after the solid solution can greatly improve the hardness of the alloy material; thereby, the Mg alloy can have both excellent mechanical properties and thermal conductivity.

[0027] 3. The present invention uses common metal elements, which have the advantage of low cost and are convenient for large-scale industrial production. At the same time, the preparation method of the present invention adopts a combination of metal mold gravity casting and heat treatment, which is simple and easy to implement and suitable for industrial production.

[0028] Other advantages, objectives and features of the invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The XRD diffraction patterns of Examples 1-4 are shown in FIG.

[0030] Figure 2 The ultimate tensile strength and tensile yield strength of the alloys obtained in Examples 1-4.

[0031] Figure 3 is the elongation of the alloys obtained in Examples 1-4.

[0032] Figure 4 is the thermal conductivity of the alloys prepared in Examples 1-4. DETAILED DESCRIPTION

[0033] In order to make the technical means, creative features, objectives and functions of the invention clearer and easier to understand, the invention is further described below in conjunction with the accompanying drawings and specific implementation methods:

[0034] Example 1

[0035] Preparation of Mg-0.9Zn-0.1Cu-0.1Ca-0.3Zr alloy material (named ZXKC1000):

[0036] S1. Pure Mg, pure Zn, pure Cu, Mg-30wt.% Zr, Mg-25wt.% Ca were weighed in proportion and placed in a blast drying oven at 200 ° C for more than 30 min. At the same time, a polished and cleaned carbon steel crucible was also placed in a blast drying oven for insulation;

[0037] S2. The pure Mg and pure Cu after the insulation in S1 are added to a carbon steel crucible, and the carbon steel crucible is placed in a pit-type resistance furnace at 400 ° C for more than 30 min;

[0038] S3. The pit-type resistance furnace is heated to 720°C. After pure Mg and pure Cu are completely melted, the temperature is kept at 20 min. In this process, a mixed gas of CO2:SF6 = 99:1 is used as a protective gas, and the gas flow rate is 2 L / min.

[0039] S4. Pure Zn, Mg-30wt.% Zr and Mg-25wt.% Ca were added to the melt in S3, stirred for 1 min and then kept at 720°C for 30 min to obtain a Mg alloy melt;

[0040] S5. A refining agent is configured with MgCl2:KCl:BaCl2:CaF2:NaCl:CaCl2:MgO=85:72:14:10:8:8:3, and the amount is 1% of the mass of the Mg alloy melt, and then directly added to the Mg alloy melt prepared in S4, stirred for 1 min and kept warm for 30 min;

[0041] S6. Then, the pit-type resistance furnace is cooled to 720°C first, and then cooled to 700°C again. During this period, a handheld thermocouple is inserted into the Mg alloy melt to accurately measure the temperature. When the temperature of the Mg alloy drops to 700°C, the Mg alloy melt is cast into a metal mold that has been kept at 200°C for more than 30 minutes and cooled to room temperature. During this period, a mixed gas of CO2:SF6=99:1 is used as a protective gas, and the gas flow rate is 2L / min, and the Mg alloy melt is continuously purged;

[0042] S7. After the Mg alloy melt in S6 solidifies to form a Mg alloy ingot, the Mg alloy ingot is then removed from the mold and placed in water, and the Mg alloy ingot is completely cooled and removed to dry;

[0043] S8. The Mg alloy ingot in S7 was wrapped with carbon powder and kept in a box-type resistance furnace at 500°C for 5 min, then the Mg alloy ingot was taken out and immersed in water, and the Mg alloy ingot was taken out and dried after being completely cooled to obtain a T4 state Mg alloy ingot;

[0044] S9. The T4 state Mg alloy ingot obtained in S8 was kept in a forced air drying oven at 250°C for 6 hours, then taken out and air-cooled to obtain a T6 state Mg alloy ingot, namely ZXKC1000.

[0045] Example 2

[0046] Preparation of Mg-1.7Zn-0.1Cu-0.3Ca-0.4Zr alloy material (named ZXKC2000):

[0047] S1. Pure Mg, pure Zn, pure Cu, Mg-30wt.% Zr, Mg-25wt.% Ca were weighed in proportion and placed in a blast drying oven at 200 ° C for more than 30 min. At the same time, a polished and cleaned carbon steel crucible was also placed in a blast drying oven for insulation;

[0048] S2. The pure Mg and pure Cu after the insulation in S1 are added to a carbon steel crucible, and the carbon steel crucible is placed in a pit-type resistance furnace at 400 ° C for more than 30 min;

[0049] S3. The pit-type resistance furnace is heated to 730°C. After the pure Mg and pure Cu are completely melted, the temperature is kept at 20 min. In this process, a mixed gas of CO2:SF6 = 99:1 is used as a protective gas, and the gas flow rate is 2 L / min;

[0050] S4. Pure Zn, Mg-30wt.% Zr and Mg-25wt.% Ca were added to the melt in S3, stirred for 2 min and then kept at 730°C for 30 min to obtain a Mg alloy melt;

[0051] S5. A refining agent is configured with MgCl2:KCl:BaCl2:CaF2:NaCl:CaCl2:MgO=85:72:14:10:8:8:3, and the amount is 1% of the mass of the Mg alloy melt, and then directly added to the Mg alloy melt prepared in S4, stirred for 2min and then kept warm for 30min;

[0052] S6. Then, the pit-type resistance furnace is cooled to 720°C first, and then cooled to 700°C again. During this period, a handheld thermocouple is inserted into the Mg alloy melt to accurately measure the temperature. When the temperature of the Mg alloy drops to 700°C, the Mg alloy melt is cast into a metal mold that has been kept at 200°C for more than 30 minutes and cooled to room temperature. During this period, a mixed gas of CO2:SF6=99:1 is used as a protective gas with a gas flow rate of 2L / min, and the Mg alloy melt is continuously purged;

[0053] S7. After the Mg alloy melt in S6 solidifies to form a Mg alloy ingot, the Mg alloy ingot is then removed from the mold and placed in water, and the Mg alloy ingot is completely cooled and removed to dry;

[0054] S8. The Mg alloy ingot in S7 is wrapped with carbon powder, kept in a box-type resistance furnace at 470°C for 45 min, then the Mg alloy ingot is taken out and immersed in water, and after the Mg alloy ingot is completely cooled, it is taken out and dried to obtain a T4 state Mg alloy ingot;

[0055] S9. The T4 state Mg alloy ingot obtained in S8 was kept in a blast drying oven at 200° C. for 12 h, then taken out and air-cooled to obtain a T6 state Mg alloy ingot, namely ZXKC2000.

[0056] Example 3

[0057] Preparation of Mg-2.9Zn-0.2Cu-0.2Ca-0.4Zr alloy material (named ZXKC3000):

[0058] S1. Pure Mg, pure Zn, pure Cu, Mg-30wt.% Zr, Mg-25wt.% Ca were weighed in proportion and placed in a blast drying oven at 200 ° C for more than 30 min. At the same time, a polished and cleaned carbon steel crucible was also placed in a blast drying oven for insulation;

[0059] S2. The pure Mg and pure Cu after the insulation in S1 are added to a carbon steel crucible, and the carbon steel crucible is placed in a pit-type resistance furnace at 400 ° C for more than 30 min;

[0060] S3. The pit-type resistance furnace was heated to 730°C. After the pure Mg and pure Cu were completely melted, the temperature was kept at 30 min. During the process, a mixed gas of CO2:SF6 = 99:1 was used as the protective gas, and the gas flow rate was 2 L / min.

[0061] S4. Pure Zn, Mg-30wt.% Zr and Mg-25wt.% Ca were added to the melt in S3, stirred for 2 min and then kept at 730°C for 30 min to obtain a Mg alloy melt;

[0062] S5. A refining agent is configured with MgCl2:KCl:BaCl2:CaF2:NaCl:CaCl2:MgO=85:72:14:10:8:8:3, and the amount is 1% of the mass of the Mg alloy melt, and then directly added to the Mg alloy melt prepared in S4, stirred for 2min and then kept warm for 30min;

[0063] S6. Then, the pit-type resistance furnace is first cooled to 710°C, and then cooled again to 690°C. During this period, a handheld thermocouple is inserted into the Mg alloy melt to accurately measure the temperature. When the temperature of the Mg alloy drops to 690°C, the Mg alloy melt is cast into a metal mold that has been kept at 200°C for more than 30 minutes and cooled to room temperature. During this period, a mixed gas of CO2:SF6=99:1 is used as a protective gas, and the gas flow rate is 2L / min, and the Mg alloy melt is continuously purged;

[0064] S7. After the Mg alloy melt in S6 solidifies to form a Mg alloy ingot, the Mg alloy ingot is then removed from the mold and placed in water, and the Mg alloy ingot is completely cooled and removed to dry;

[0065] S8. The Mg alloy ingot in S7 is wrapped with carbon powder, kept in a box-type resistance furnace at 470°C for 120 min, then the Mg alloy ingot is taken out and immersed in water, and after the Mg alloy ingot is completely cooled, it is taken out and dried to obtain a T4 state Mg alloy ingot;

[0066] S9. The T4 state Mg alloy ingot obtained in S8 was kept in a blast drying oven at 200°C for 14 hours, then taken out and air-cooled to obtain a T6 state Mg alloy ingot, namely ZXKC3000.

[0067] Example 4

[0068] Preparation of Mg-4.2Zn-0.3Cu-0.2Ca-0.5Zr alloy material (named ZXKC4000):

[0069] S1. Pure Mg, pure Zn, pure Cu, Mg-30wt.% Zr, Mg-25wt.% Ca were weighed in proportion and placed in a blast drying oven at 200 ° C for more than 30 min. At the same time, a polished and cleaned carbon steel crucible was also placed in a blast drying oven for insulation;

[0070] S2. The pure Mg and pure Cu after the insulation in S1 are added to a carbon steel crucible, and the carbon steel crucible is placed in a pit-type resistance furnace at 400 ° C for more than 30 min;

[0071] S3. The pit-type resistance furnace is heated to 750°C. After pure Mg and pure Cu are completely melted, the temperature is kept at 40 min. During the process, a mixed gas of CO2:SF6 = 99:1 is used as a protective gas, and the gas flow rate is 2 L / min;

[0072] S4. Pure Zn, Mg-30wt.% Zr and Mg-25wt.% Ca were added to the melt in S3, stirred for 3 min and then kept at 750°C for 30 min to obtain a Mg alloy melt;

[0073] S5. A refining agent is configured with MgCl2:KCl:BaCl2:CaF2:NaCl:CaCl2:MgO=85:72:14:10:8:8:3, and the amount is 1% of the mass of the Mg alloy melt, and then directly added to the Mg alloy melt prepared in S4, stirred for 3min and then kept warm for 30min;

[0074] S6. The pit-type resistance furnace is then cooled to 700°C, and then cooled to 685°C again. During this period, a handheld thermocouple is inserted into the Mg alloy melt to accurately measure the temperature. When the temperature of the Mg alloy drops to 685°C, the Mg alloy melt is cast into a metal mold that has been kept at 200°C for more than 30 minutes and cooled to room temperature. During this period, a mixed gas of CO2:SF6=99:1 is used as a protective gas with a gas flow rate of 2L / min, and the Mg alloy melt is continuously purged;

[0075] S7. After the Mg alloy melt in S6 solidifies to form a Mg alloy ingot, the Mg alloy ingot is then removed from the mold and placed in water, and the Mg alloy ingot is completely cooled and removed to dry;

[0076] S8. The Mg alloy ingot in S7 is wrapped with carbon powder and kept in a box-type resistance furnace at 450°C for 360 min, then the Mg alloy ingot is taken out and immersed in water, and the Mg alloy ingot is taken out and dried after being completely cooled to obtain a T4 state Mg alloy ingot;

[0077] S9. The T4 state Mg alloy ingot obtained in S8 was kept in a forced air drying oven at 150°C for 28 hours, then taken out and air-cooled to obtain a T6 state Mg alloy ingot, namely ZXKC4000.

[0078] Comparative Example 1

[0079] Made of AZ91 alloy.

[0080] Comparative Example 2

[0081] Compared with Example 1, the alloy material is Mg-0.9Zn-0.1Cu, and the rest is the same (named ZC10).

[0082] Comparative Example 3

[0083] Compared with Example 3, the alloy material is Mg-2.9Zn-0.2Ca-0.4Zr, and the rest is the same (named ZXK300).

[0084] Comparative Example 4

[0085] Compared with Example 3, the alloy material is Mg-2.9Zn-0.2Cu-0.4Zr, and the rest is the same (named as ZCK300).

[0086] Comparative Example 5

[0087] Compared with Example 4, the alloy material is Mg-4.2Zn-0.2Ca-0.5Zr, and the rest is the same (named ZXK400).

[0088] Comparative Example 6

[0089] Compared with Example 3, the subsequent operations of S8 and S9 are not performed, and the rest are the same (named ZXKC3000-as-cast).

[0090] Among them, in the preparation process of Examples 1-4, it should be noted that during the mixing process of the Mg alloy melt and the refining agent, the mixed gas of CO2:SF6=99:1 will form a dense protective film on the surface of the Mg alloy melt, which can effectively hinder the evaporation of Mg. Therefore, during the stirring process, care should be taken not to damage the protective film on the surface of the melt to prevent Mg from evaporating, which will make the composition of the Mg alloy melt difficult to control, and at the same time avoid the damaged protective film from becoming inclusions, thereby reducing the performance of the final Mg alloy material.

[0091] The purpose of cooling twice is that when the temperature of the pit-type resistance furnace is lowered, the resistance wire stops working immediately, and the heat capacity of various gases inside the pit-type resistance furnace is very low, so the temperature of the carbon steel crucible drops rapidly, but the heat capacity of the Mg alloy melt is very high, so the temperature of the Mg alloy melt drops slowly, resulting in a large temperature difference between the surface and the center of the Mg alloy melt. When the internal temperature of the Mg alloy melt reaches the predetermined value, its surface temperature will be lower than the predetermined value, and even solidify to a certain extent, affecting the casting process.

[0092] The ultimate tensile strength (UTS), tensile yield strength (TYS), elongation (EL) and thermal conductivity of Examples 1-4 and Comparative Examples 1-6 are shown in Table 1:

[0093]

[0094]

[0095] Table 1

[0096] It can be seen from Table 1 that the magnesium alloy materials prepared in Examples 1-4 can better balance mechanical properties and thermal conductivity compared with the magnesium alloy materials prepared in Comparative Examples 1-6.

[0097] Among them, it can be seen from Comparative Examples 2-5 that, although only one or two components are reduced compared with the corresponding embodiments, and the thermal conductivity of the magnesium alloy material finally obtained can be guaranteed, the mechanical properties are far inferior to those of the magnesium alloy material prepared in the corresponding embodiments. Therefore, the magnesium alloy material prepared in Comparative Examples 2-5 cannot take into account both good thermal conductivity and mechanical properties.

[0098] As for Comparative Example 6, the two-step heat treatment of solid solution and aging is reduced. Although its thermal conductivity has not changed significantly, its mechanical properties are seriously reduced compared with those of Example 3. Therefore, the magnesium alloy material prepared by a single casting method cannot have both good mechanical properties and thermal conductivity.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the invention rather than to limit it. Although the invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the invention, which should be included in the scope of the claims of the invention.

Claims

1. A new type of high-strength and high-thermal-conductivity magnesium alloy material, characterized in that: Calculated by mass percentage, the steel comprises the following components: Zn 0.8-4.4%, Cu 0.1-0.3%, Ca 0.1-0.3% and Zr 0.3-0.5%, with the remainder being Mg and unavoidable impurities.

2. The method for preparing a novel high-strength and high-thermal-conductivity magnesium alloy material according to claim 1, characterized in that: The following steps are involved: S1. Prepare raw materials according to the ratio; S2 configures a refining agent, and then melts the raw materials prepared in S1 in sequence and stands for a period of time, and then mixes with the refining agent to obtain a Mg alloy melt, and controls the temperature of the Mg alloy melt within a specific range; S3. The Mg alloy melt in S2 is cast into a metal mold, and after the Mg alloy melt solidifies, it is removed and slowly immersed in water, and then cooled to obtain a Mg alloy ingot; S4. The Mg alloy ingot obtained in S3 was kept at a specific temperature for a period of time, and then slowly immersed in water and cooled to obtain a Mg alloy ingot in the T4 state; S5. The T4 state Mg alloy ingot obtained in S4 is kept at a specific temperature for a period of time and then air-cooled to obtain a T6 state Mg alloy ingot, that is, the magnesium alloy material.

3. The method for preparing a novel high-strength and high-thermal-conductivity magnesium alloy material according to claim 2, characterized in that: In step S1 , the raw materials are added in the form of pure Mg, pure Zn, pure Cu, Mg-30wt.% Zr and Mg-25wt.% Ca, respectively. The above five raw materials need to be kept at 200° C. for 30 minutes.

4. The method for preparing a novel high-strength and high-thermal-conductivity magnesium alloy material according to claim 2, characterized in that: In step S2, the steps of melting the five raw materials and mixing them with the refining agent are as follows: S21. Pure Mg and pure Cu were kept at 400 ° C for at least 30 min, then heated to 720 ° C-750 ° C for melting, and then kept warm for 20-40 min. During this process, a mixture of CO2: SF6 = 99:1 was used as a shielding gas at a gas flow rate of 2 L / min. S22 pure Zn, Mg-30wt.% Zr and Mg-25wt.% Ca are added to the melt of step S21 and stirred for 1-3min to obtain a Mg alloy melt, which is then heated at 720-750°C for 30min; S23. The refining agent is added to the Mg alloy melt obtained in step S22, stirred for 1-3min and then kept warm for 30min; S24. The Mg alloy melt mixed with the refining agent in S23 is cooled twice at 700-720°C and 685-700°C and then set aside.

5. The method for preparing a novel high-strength and high-thermal-conductivity magnesium alloy material according to claim 4, characterized in that: In step S2, the refining agent is configured as MgCl2:KCl:BaCl2:CaF2:NaCl:CaCl2:MgO=85:72:14:10:8:8:3, and the amount used is 1% of the mass of the Mg alloy melt.

6. The method for preparing a novel high-strength and high-thermal-conductivity magnesium alloy material according to claim 2, characterized in that: In step S3, the metal mold needs to be kept at 200°C for more than 30 minutes before casting and then cooled to room temperature in air.

7. The method for preparing a novel high-strength and high-thermal-conductivity magnesium alloy material according to claim 2, characterized in that: In step S3, a mixed gas of CO2:SF6=99:1 is used as the shielding gas during the casting process, with a gas flow rate of 2 L / min, and the Mg alloy melt is continuously purged.

8. The method for preparing a novel high-strength and high-thermal-conductivity magnesium alloy material according to claim 2, characterized in that: In step S4, the Mg alloy ingot is kept at 450-500° C. for 5-360 minutes.

9. The method for preparing a novel high-strength and high-thermal-conductivity magnesium alloy material according to claim 2, characterized in that: In step S4, during the heat preservation process, the Mg alloy ingot is wrapped with carbon powder.

10. The method for preparing a novel high-strength and high-thermal-conductivity magnesium alloy material according to claim 2, characterized in that: In step S5, the T4 state Mg alloy ingot is kept at 150-250° C. for 6-28 hours.

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