Manufacturing method of magnesium alloy with high thermal conductivity

Abstract

The invention discloses a manufacturing method of a magnesium alloy with high thermal conductivity, which is characterized in that the magnesium alloy comprises the following components in percentage by mass: 0.5-0.8% of Bi; 0.5% to 0.8% of Ca; and the balance of Mg and inevitable impurities. By regulating and controlling elements of magnesium and an alloy thereof, a water-cooling semi-continuous casting method is adopted, grains are refined, a microstructure is optimized, a second phase in the alloy is uniformly distributed, casting defects are reduced, the consistency of material performance is improved, and the tensile yield strength, toughness, corrosion resistance and heat-conducting property of the magnesium alloy are improved; the alloy elements are fully dissolved, obstruction of second-phase particles to heat conduction is reduced, the heat conductivity coefficient is improved, the operation procedure is simple, energy consumption is low, the adopted raw materials are easy to obtain and low in cost, good economical efficiency is achieved, and wide application and development of the alloy are promoted.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a high thermal conductivity magnesium alloy, belonging to the technical field of magnesium alloy processing. Background Art

[0002] Magnesium and its alloys are currently the lightest metal structural materials, with a density of about 1.8g / m3, which is only 64% of aluminum and 25% of steel. Magnesium alloys have the advantages of high specific strength and specific stiffness, good electrical and thermal conductivity, good damping performance and electromagnetic shielding performance. They have broad application prospects in 3C electronics, automobiles, aerospace, and national defense and military industries. Compared with traditional aluminum alloys, magnesium alloys have a broader application prospect in the field of heat dissipation materials due to their low density and excellent thermal conductivity. At the same time, they are recyclable, which is of great value to the timely achievement of the "dual carbon" goals. With the continuous advancement of materials science and the development of heat dissipation technology, magnesium alloys are expected to play their heat dissipation advantages in more fields. The development of high-strength and high-thermal conductivity magnesium alloys has become the focus of current research work.

[0003] The thermal conductivity of pure magnesium at room temperature is 158W / (m·K), but its mechanical properties are low, making it unsuitable for use as an engineering material. Alloying can significantly increase the strength of magnesium alloys, but this reduces their thermal conductivity to varying degrees. Therefore, improving the thermal conductivity of magnesium alloys is a challenge that currently needs to be addressed. Summary of the Invention

[0004] The present invention discloses a method for manufacturing a high thermal conductivity magnesium alloy, which is characterized in that the magnesium alloy comprises the following components in percentage by mass:

[0005] Bi: 0.5%~0.8%;

[0006] Ca: 0.5% to 0.8%;

[0007] The rest is Mg and inevitable impurities.

[0008] The processing method is as follows:

[0009] 1) Solution treatment of magnesium alloy;

[0010] 2) Extruding the magnesium alloy in the solid solution state at an extrusion temperature of 250°C to 275°C, an extrusion rate of 0.1 mm / s, and an extrusion ratio of 25:1;

[0011] 3) The extruded magnesium alloy is subjected to compression deformation, with the compression direction parallel to the extrusion direction, the compression temperature being 20℃~100℃, the compressive stress being 0.01~0.02, and the strain rate being 1×10 -4 -2×10 -4 s, compression for 5 to 10 minutes.

[0012] Preferably, the mass percentages of the magnesium alloy are Bi: 0.8%, Ca: 0.8%, and the remainder is magnesium and impurities that cannot be removed.

[0013] Preferably, the melting temperature is 720°C;

[0014] As a preference, after smelting, solid solution is performed at 420°C for 2 hours and at 500°C for 3 hours;

[0015] Preferably, water quenching is performed after solutionizing;

[0016] Preferably, the extrusion temperature is 250° C., the extrusion rate is 0.1 mm / s, and the extrusion ratio is 25:1.

[0017] In summary, the beneficial effects of the present invention are:

[0018] 1. In the invention, alloying can improve the structure of magnesium alloys, enhance the strength and thermal conductivity of the alloys, and by selecting appropriate main alloying element composition, melting temperature and processing technology, the solid solution content of the alloying elements is affected, thereby improving the thermal conductivity of the magnesium alloy.

[0019] 2. The invention described above uniformly precipitates Mg3Bi2 and Mg2Ca phases with certain thermal stability and thermal conductivity in the magnesium alloy matrix under extrusion, which can directly improve the overall thermal conductivity of the alloy to a certain extent. At the same time, the precipitation of the Mg2Ca phase can refine the grains, increase the number of grain boundaries, and make the heat conduction in all directions more uniform, which is more conducive to improving the thermal conductivity from a macroscopic perspective.

[0020] 3. The invention When Bi is added in an amount of 0.8 wt.% and Ca is added in an amount of 0.8 wt.%, the alloy exhibits excellent thermal conductivity.

[0021] 4. The invention adds Ca. The appropriate addition of Ca can affect the non-basal texture of the magnesium alloy, promote non-basal slip, increase the path and method of heat transfer, and facilitate uniform heat conduction in the material, thereby improving the overall thermal conductivity.

[0022] 5. The magnesium alloy of the invention has low production cost, simple experimental steps and high efficiency, which is conducive to further improving the thermal conductivity of the magnesium alloy.

[0023] Improving the thermal conductivity of magnesium alloys is of great significance for promoting the development of magnesium alloys in the field of heat dissipation materials. The thermal conductivity of the experimental magnesium alloys and the comparison of corresponding alloys are illustrated in the following figures:

[0024] Figure 1 It is the scatter plot of thermal conductivity-tensile yield strength of BXZ011 alloy, BX10 alloy, BXM011 alloy and XZ11 alloy;

[0025] Figure 2 a is the metallographic structure of BX10 alloy, b is the metallographic structure of XZ11 alloy, c is the metallographic structure of BXM011 alloy, and d is the metallographic structure of BXZ011 alloy. Specific implementation plan

[0026] The following will provide a clear and complete description of the concept and technical effects of the present invention in conjunction with the embodiments, so that the purpose, features and effects of the present invention are fully understood. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative effort are all within the scope of invention protection.

[0027] Example 1

[0028] This embodiment 1 adopts a method for manufacturing a high thermal conductivity magnesium alloy, and the specific process is as follows:

[0029] A Mg-0.8Bi-0.5Ca alloy, designated BX10, was prepared using a water-cooled semi-continuous casting method. The alloy ingot was prepared using commercial-grade pure Mg (99.9 wt.%), Mg10Bi (wt.%), and a Mg-30Ca (wt.%) master alloy. The magnesium alloy's mass percentages were 0.8% Bi, 0.8% Ca, and the remainder magnesium and unremovable impurities.

[0030] The alloy casting in Example 1 was prepared by melting the alloy in a resistance furnace with a mixture of CO2 and SF6 (gas ratio of 1:99) at a melting temperature of 720°C and keeping it warm for 20 minutes. The solid structure was solution treated at 420°C for 2 hours and at 500°C for 3 hours.

[0031] In Example 1, the solid solution was water quenched and then extruded at 250°C, with an extrusion speed of 0.1 mm / s and an extrusion ratio of 25:1 to obtain an extruded rod with a diameter of 12 mm. The extruded rod was cut with a cutting machine to obtain a sample with a diameter of 9.51 mm and a thickness of 4.03 mm. The thermal conductivity coefficient was measured. This experiment used an LFA447 laser thermal conductivity meter: test temperature: 25°C, filter: 100%, voltage: 292V, pulse width: medium, pre-amplifier gain: 10, main amplifier gain: 5002, sampling time: 5000ms, delay: 10s. The test results are shown in Figure 2. Figure 1 As shown, in order to verify the repeatability, this test was repeated three times for each sample. The thermal conductivity coefficients measured three times were 118.007W / (m·K), 119.502W / (m·K), and 119.045W / (m·K), respectively, with an average value of 118.851W / (m·K).

[0032] Comparative Example 1

[0033] In Comparative Example 1, a Mg-0.5Bi-0.8Ca-0.8Zn alloy, designated BXZ011, was prepared by water-cooled semi-continuous casting. The alloy ingot was prepared using commercial-grade pure Mg (99.9 wt.%), Mg10Bi (wt.%), and a master alloy of Mg-30Ca (wt.%) and 2.5Zn (wt.%). The magnesium alloy's mass percentages were: Bi: 0.8%, Ca: 0.8%, and Zn: 0.4%, with the remainder being magnesium and unremovable impurities.

[0034] In Comparative Example 1, an alloy was obtained according to the steps in Example 1. The solid solution was water quenched and then extruded at a temperature of 225°C to 275°C. The extrusion speed was 0.2 mm / s and the extrusion ratio was 25:1 to obtain an extruded rod with a diameter of 12 mm. The extruded rod was cut with a cutting machine to obtain a sample with a diameter of 9.49 mm and a thickness of 3.99 mm. The thermal conductivity of the metal sample was measured using an LFA447 laser thermal conductivity meter. To verify the repeatability, the test was repeated three times for each sample, and the results were 99.352 W / (m·K), 98.717 W / (m·K), and 98.976 W / (m·K), respectively, with an average value of 99.015 W / (m·K). Table 1 compares and analyzes Example 1 and Comparative Example 1, as shown below:

[0035] Table 1 Properties of magnesium alloy castings prepared in Example 1 of the present invention and Comparative Example 1

[0036] alloy Temperature (℃) Tensile yield stress (MPa) Thermal conductivity W / (m·K) BX10 25 343.63 118.851 BXZ011 25 392.4 99.015

[0037] It can be seen from the data in Table 1 that the thermal conductivity of the sample in Example 1 is better than that of the sample in Comparative Example 1, and the preparation of the magnesium alloy casting is relatively successful.

[0038] Comparative Example 2

[0039] In Comparative Example 2, a Mg-0.5Bi-0.8Ca-0.8Mn alloy, designated BXM011, was prepared by a water-cooled semi-continuous casting method. The alloy ingot was prepared using commercial-grade pure Mg (99.9 wt.%), Mg10Bi (wt.%), Mg-30Ca (wt.%)-2.5Mn (wt.%), and a Mg-30Ca (wt.%) master alloy to obtain a cast magnesium alloy. The BXM011 magnesium alloy consisted of 0.8% Bi, 0.8% Ca, and 0.4% Mn by weight, with the remainder being magnesium and unremovable impurities.

[0040] In Comparative Example 2, after the alloy was prepared according to the steps in Example 1, the solid solution was water quenched and then extruded at a temperature of 225°C to 275°C, with an extrusion speed of 0.2 mm / s and an extrusion ratio of 25:1, to obtain an extruded rod with a diameter of 12 mm. The extruded rod was cut with a cutting machine to obtain a sample with a diameter of 9.49 mm and a thickness of 4.04 mm. The thermal conductivity of the metal sample was measured using an LFA447 laser thermal conductivity meter. To verify repeatability, the test was repeated three times for each sample, and the results were 84.181 W / (m·K), 90.846 W / (m·K), and 86.597 W / (m·K), respectively, with an average value of 87.208 W / (m·K). Table 2 compares and analyzes Example 1 and Comparative Example 2, as shown below:

[0041] Table 2 Properties of magnesium alloy castings prepared in Example 1 and Comparative Example 2

[0042] alloy Temperature (℃) Tensile yield stress (MPa) Thermal conductivity W / (m·K) BX10 25 343.63 118.851 BXM011 25 418 87.208

[0043] It can be seen from the data in Table 2 that the thermal conductivity of the sample in Example 1 is better than that of the sample in Comparative Example 2, and the preparation of the magnesium alloy casting is relatively successful.

[0044] Comparative Example 3

[0045] In Comparative Example 3, a Mg-0.8Ca-0.8Zn alloy, designated XZ11, was prepared using a water-cooled semi-continuous casting method. The alloy ingot was prepared using commercial-grade pure Mg (99.9 wt.%), Mg-30Ca (wt.%)-2.5Zn (wt.%), and a Mg-30Ca (wt.%) master alloy to obtain a cast magnesium alloy. The XZ11 magnesium alloy contained 0.8% Ca and 0.4% Zn by weight, with the remainder being magnesium and unremovable impurities.

[0046] In Comparative Example 3, after the alloy was prepared according to the steps in Example 1, the solid solution was water quenched and then extruded at 250°C, with an extrusion speed of 0.1 mm / s and an extrusion ratio of 25:1, to obtain an extruded rod with a diameter of 12 mm. The extruded rod was cut with a cutting machine to obtain a sample with a diameter of 9.51 mm and a thickness of 4.01 mm. The thermal conductivity of the metal sample was measured using an LFA447 laser thermal conductivity meter. To verify repeatability, the test was repeated three times for each sample, and the results were 98.934 W / (m·K), 100.183 W / (m·K), and 98.680 W / (m·K), respectively, with an average value of 99.266 W / (m·K). Table 3 compares and analyzes Example 1 and Comparative Example 3, as shown below:

[0047] Table 3 Properties of magnesium alloy castings prepared in Example 1 of the present invention and Comparative Example 3

[0048] alloy Temperature (℃) Tensile yield stress (MPa) Thermal conductivity W / (m·K) BX10 25 343.63 118.851 XZ11 25 367.56 99.266

[0049] It can be seen from the data in Table 3 that the thermal conductivity of the sample in Example 1 is better than that of the sample in Comparative Example 3, and the preparation of the magnesium alloy casting is relatively successful.

[0050] Depend on Figure 2 The BX10 alloy exhibits relatively uniform microstructure, which helps reduce thermal conductivity anisotropy caused by compositional segregation or local structural differences, avoiding local hot spots or concentrated heat flux, thereby improving the overall thermal conductivity and stability of the material. Smaller, evenly distributed pores have a relatively weaker effect on phonon scattering, reducing the shortening of the phonon mean free path, allowing phonons to propagate more freely and transfer heat more efficiently, thus positively impacting overall thermal conductivity. The BXZ011 alloy exhibits an inhomogeneous microstructure, exhibiting a pronounced layered structure that hinders heat flow, increases thermal resistance, and reduces overall thermal conductivity. The BXM011 alloy exhibits pronounced black pores in its microstructure, disrupting the continuity of the alloy structure, increasing thermal resistance, and hindering heat conduction. The inhomogeneous microstructure, along with the presence of impurities or second-phase particles, scatters heat, leading to energy losses during heat transfer and hindering thermal conductivity. The metallographic structure of XZ11 alloy shows obvious directional stripes. This anisotropic structure will cause differences in heat conduction in different directions, which is not conducive to uniform heat diffusion.

[0051] The above description is merely a specific embodiment of the invention, but the scope of protection of the invention is not limited thereto. Any changes or substitutions that are not conceived through creative effort should be included within the scope of protection of the invention. Therefore, the scope of protection of the invention should be based on the scope of protection defined in the claims.

Claims

1. A method for producing a high thermal conductivity magnesium alloy, characterized in that The magnesium alloy comprises the following components in percentage by mass: Bi: 0.5%~0.8%; Ca: 0.5% to 0.8%; The rest is Mg and inevitable impurities. The processing steps are as follows: 1) Solution treatment of magnesium alloy; 2) Extruding the solid solution magnesium alloy at an extrusion temperature of 250°C, an extrusion rate of 0.1 mm / s, and an extrusion ratio of 25:1; 3) The extruded magnesium alloy is subjected to compression deformation, with the compression direction parallel to the extrusion direction, the compression temperature being 20℃~100℃, the compressive stress being 0.01~0.02, and the strain rate being 1×10 -4 -2×10 -4 s, compression for 5 to 10 minutes.

2. The method for manufacturing a high thermal conductivity magnesium alloy according to claim 1, characterized in that The mass percentages of the magnesium alloy are Bi: 0.5% to 0.8%, Ca: 0.5% to 0.8%, and the rest are magnesium and impurity elements that cannot be removed.

3. The method for manufacturing a high thermal conductivity magnesium alloy according to claim 1, characterized in that: The melting temperature of the magnesium alloy is 720° C., the solid solution temperature after melting is 420° C. and 500° C., and the solid solution temperature is 420° C. for 2 hours and 500° C. for 3 hours.

4. The method for manufacturing a high thermal conductivity magnesium alloy according to claim 1, characterized in that The extrusion temperature is 250° C., the extrusion rate is 0.1 mm / s, and the extrusion ratio is 25:1.

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