Method for improving comprehensive performance coefficient of magnesium alloy

Abstract

The invention discloses a method for improving the comprehensive performance coefficient of a magnesium alloy, which comprises the following steps: 1) providing raw materials according to the chemical components of the magnesium alloy, and preheating the raw materials; (2) melting the preheated magnesium ingot under the conditions of protective gas and the temperature of 680-750 DEG C to obtain magnesium liquid; (3) under the conditions of protective gas and 700-800 DEG C, the preheated magnesium-lanthanum intermediate alloy is added into the magnesium liquid, the magnesium-lanthanum intermediate alloy is melted, then the preheated manganese powder is added into the magnesium liquid, and mixed liquid is obtained; the mixed liquid is refined and subjected to slag removal, and magnesium alloy liquid is obtained; (4) the magnesium alloy liquid is poured into a mold at the temperature of 650-750 DEG C, cooling is conducted, and a primary magnesium alloy ingot is obtained; and (5) the primary magnesium alloy ingot is annealed and then extruded at the temperature of 200-500 DEG C, and the magnesium alloy is obtained. The magnesium alloy prepared by the method has relatively high heat conductivity and elongation, so that the comprehensive performance coefficient is relatively high.

Description

Technical Field

[0001] The invention relates to a method for improving the comprehensive performance coefficient of a magnesium alloy. Background Art

[0002] Currently, the main heat dissipation alloy materials include copper alloy, aluminum alloy, and magnesium alloy. Pure copper has the highest thermal conductivity of 397W / (m·K), pure aluminum has a thermal conductivity of 247W / (m·K), and pure magnesium has a thermal conductivity of 158W / (m·K). Although magnesium's thermal conductivity is lower than that of copper and aluminum, it has the characteristics of low density, high specific strength and specific stiffness, good shock absorption, and excellent electromagnetic shielding performance. As a material for electronic device housings, it can well meet the requirements of electronic devices for light weight and small size. Therefore, magnesium has unique advantages as a heat sink material for electronic devices.

[0003] According to thermal conductivity theory, adding alloying elements to a matrix, whether forming a solid solution or a second phase, significantly reduces the thermal conductivity of the material. This reduction in the thermal conductivity of magnesium alloys is due to the difference in atomic radius between the alloying elements and magnesium. The addition of alloying elements can cause periodic changes in the magnesium matrix lattice, distorting the lattice and affecting the free movement of electrons within the lattice, reducing the mean free path of electrons and, consequently, the thermal conductivity of the magnesium alloy. Therefore, those skilled in the art have been working on improvements to magnesium alloys to address this issue.

[0004] CN113322404A discloses a high-thermal-conductivity, high-strength Mg-Al-La-Mn wrought magnesium alloy comprising 2.8-3.5 wt% Al, 4.3-5.0 wt% La, and 0.28-0.3 wt% Mn, with Mg as the balance. The highly dissolved Al reacts with La to form a secondary phase, reducing the effect of La on the thermal conductivity of the magnesium alloy. The resulting magnesium alloy belongs to the magnesium-aluminum alloy system. However, the generated secondary phase affects the alloy's thermal conductivity and cannot completely eliminate the adverse effects of Al addition on thermal conductivity. Its overall performance still needs to be improved.

[0005] CN116732401A discloses a high-strength, high-thermal-conductivity deformable magnesium alloy Mg-xZn-0.5Mn-yRE with a rare earth element mixture, wherein x is 0.5 to 3 wt%, y is less than 0.5 wt%, and RE is composed of any La / Ce mixture ratio, added via a Mg-30La / Ce mixed rare earth master alloy (the La / Ce mass ratio in the master alloy is arbitrary). The rare earth elements added to this magnesium alloy are a combination of La and Ce. Excessive additions can adversely affect the alloy's thermal conductivity and lead to excessively high production costs. More importantly, the solid solubility of Zn in the magnesium matrix (2.40 at%) is much greater than that of La (0.14 at%), weakening the strengthening effect of La.

[0006] CN117026036A discloses a high-thermal-conductivity, high-strength wrought magnesium alloy Mg-Mn-X. X is a light rare earth element, with a content of 0.5-5.0 wt%, and Mn is 0.5-4.0 wt%. The remainder is Mg and unavoidable impurities. The high addition of rare earth elements in this magnesium alloy results in low elongation.

[0007] CN118773497A discloses a high-strength, high-thermal conductivity magnesium alloy containing a high abundance of rare earth elements. The alloy consists of 1.45-1.55 wt% Zn, 0.45-0.55 wt% Mn, 0.15-1.5 wt% La, and the remainder Mg and unavoidable impurities. The solid solubility of Zn in the magnesium matrix (2.40 at%) is much greater than that of La (0.14 at%), which weakens the strengthening effect of La. Summary of the Invention

[0008] In view of this, an object of the present invention is to provide a method for improving the comprehensive performance coefficient of a magnesium alloy, which can significantly improve the thermal conductivity and elongation of the magnesium alloy and achieve a higher comprehensive performance coefficient.

[0009] The present invention adopts the following technical solutions to achieve the above-mentioned purpose.

[0010] The present invention provides a method for improving the comprehensive performance coefficient of a magnesium alloy, comprising the following steps:

[0011] 1) providing raw materials according to the chemical composition of a magnesium alloy and preheating the raw materials; wherein the chemical composition of the magnesium alloy is as follows by weight percentage: La 0.8-1.2 wt%, Mn 0.2-1.0 wt%, and the balance is magnesium and unavoidable impurities; the raw materials include a magnesium ingot, a magnesium-lanthanum master alloy, and manganese powder;

[0012] 2) melting the preheated magnesium ingot under a protective gas at 680-750° C. to obtain magnesium liquid; wherein the protective gas is composed of SF6 and N2, and the volume ratio of SF6 to N2 is 1:300-800;

[0013] 3) adding the preheated magnesium-lanthanum master alloy to magnesium liquid under a protective gas at 700-800° C. to melt the magnesium-lanthanum master alloy, then adding the preheated manganese powder thereto, stirring for 60-150 minutes to obtain a mixed solution; refining and deslagging the mixed solution to obtain a magnesium alloy liquid; wherein the protective gas comprises SF6 and N2, and the volume ratio of SF6 to N2 is 1:300-800;

[0014] 4) pouring the magnesium alloy liquid into a mold at 650-750° C. and cooling it to obtain a primary magnesium alloy ingot;

[0015] 5) annealing the primary magnesium alloy ingot, and then extruding it at 200-500° C. to obtain a magnesium alloy;

[0016] Among them, the comprehensive performance coefficient ε=λ×δ; where λ is thermal conductivity, the unit is W / (m·K); δ is elongation, the unit is %.

[0017] According to the method of the present invention, preferably, in step 1), the chemical composition of the magnesium alloy is as follows by weight percentage: La 0.85-1.15wt%, Mn 0.3-0.8wt%, and the balance is magnesium and unavoidable impurities.

[0018] According to the method of the present invention, preferably, in step 1), the preheating temperature is 100-300° C., and the preheating time is 1-8 hours.

[0019] According to the method of the present invention, preferably, in step 2), the volume ratio of SF6 to N2 is 1:350-650.

[0020] According to the method of the present invention, preferably, in step 3), the volume ratio of SF6 to N2 is 1:350-650.

[0021] According to the method of the present invention, preferably, in step 3), argon is used to refine the mixed liquid, and the flow rate of argon is 80-150 cm 3 / min.

[0022] According to the method of the present invention, preferably, in step 3), after slagging, the mixed solution is allowed to stand for 45 to 90 minutes, and then allowed to stand at 680 to 780° C. for another 20 to 60 minutes to obtain a magnesium alloy liquid.

[0023] According to the method of the present invention, preferably, in step 5), the extrusion is forward extrusion, and the extrusion ratio is 12 to 20:1.

[0024] According to the method of the present invention, preferably, the comprehensive performance coefficient ε of the magnesium alloy is greater than 15 W / (m·K).

[0025] According to the method of the present invention, preferably, the magnesium alloy has an elongation δ of 12% or more and a thermal conductivity λ of 124 W / (m·K) or more;

[0026] The elongation δ is measured according to GB / T228.1-2021, and the thermal conductivity λ is measured using a NETZSCH LFA427 laser thermal conductivity meter.

[0027] The present invention improves the comprehensive performance coefficient of the magnesium alloy by controlling the contents of La and Mn in the magnesium alloy and using SF6 and N2 as protective gases. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0029] The "elongation" mentioned in the present invention refers to the percentage of the elongation of the gauge section after the object breaks during the stretching process to the original gauge length, usually expressed as "%".

[0030] The "thermal conductivity" mentioned in the present invention refers to the amount of heat transferred from one plane to the other in one second if the temperature difference between the two parallel planes, which are 1 meter apart and have an area of 1 square meter, is 1 K and is perpendicular to the direction of heat conduction. The unit is W / (m·K).

[0031] <Method for Improving the Comprehensive Performance Coefficient of Magnesium Alloy>

[0032] The present invention provides a method for improving the comprehensive performance coefficient of a magnesium alloy. The comprehensive performance coefficient ε is characterized by the following formula:

[0033] ε=λ×δ

[0034] Comprehensive performance coefficient ε = λ × δ; where λ is thermal conductivity, unit is W / (m·K); δ is elongation, unit is %.

[0035] Thermal conductivity represents the thermal conductivity of a magnesium alloy, while elongation represents its plasticity. These two parameters are the most important indicators of a magnesium alloy, and their product represents its overall performance. The larger the overall performance coefficient ε, the better the overall performance of the magnesium alloy.

[0036] The method of the present invention comprises the following steps: raw material preparation, magnesium ingot melting, magnesium alloy liquid preparation, primary magnesium alloy ingot preparation and extrusion, which are described in detail below.

[0037] Raw material preparation steps

[0038] Raw materials are provided according to the chemical composition of the magnesium alloy and are preheated.

[0039] According to one embodiment of the present invention, the chemical composition of the magnesium alloy is as follows by weight percentage: La 0.8-1.2 wt %, Mn 0.2-1.0 wt %, and the balance is magnesium and unavoidable impurities.

[0040] In the magnesium alloy of the present invention, the amount of La can be 0.8 to 1.2 wt%, preferably 0.85 to 1.15 wt%, and more preferably 0.9 to 1.1 wt%. In the magnesium alloy of the present invention, the amount of Mn can be 0.2 to 1.0 wt%, preferably 0.3 to 0.8 wt%, and more preferably 0.4 to 0.6 wt%. Controlling the amounts of La and Mn within the above ranges helps balance the thermal conductivity and mechanical properties of the magnesium alloy, thereby ensuring that the magnesium alloy has both good thermal conductivity and elongation, thereby improving the overall performance of the magnesium alloy. Exceeding the above ranges will adversely affect the overall performance of the magnesium alloy.

[0041] According to a specific embodiment of the present invention, the chemical composition of the magnesium alloy is as follows by weight percentage: La 0.85-1.15 wt %, Mn 0.3-0.8 wt %, and the balance is magnesium and unavoidable impurities.

[0042] According to a preferred embodiment of the present invention, the chemical composition of the magnesium alloy is as follows by weight percentage: La 0.9-1.1 wt %, Mn 0.4-0.6 wt %, and the balance is magnesium and unavoidable impurities.

[0043] The raw materials of the present invention may include a magnesium ingot, a magnesium-lanthanum master alloy, and manganese powder. Preferably, the raw materials of the present invention are composed of the magnesium ingot, the magnesium-lanthanum master alloy, and the manganese powder. The magnesium ingot, the magnesium-lanthanum master alloy, and the manganese powder used in the present invention may be commercially available products or prepared by existing preparation methods. The raw materials of the present invention have a purity of at least 99.98 wt%.

[0044] In the magnesium-lanthanum master alloy, the mass percentage of lanthanum may be 5 to 50 wt %, preferably, the mass percentage of lanthanum is 10 to 50 wt %, and more preferably, the mass percentage of lanthanum is 10 to 30 wt %.

[0045] According to one embodiment of the present invention, the preheating temperature can be 100-300°C, preferably 120-280°C, and more preferably 150-250°C. The preheating time can be 1-8 hours, preferably 2-7 hours, and more preferably 3-6 hours. Reasonable preheating conditions are conducive to removing moisture and impurities, reducing hydrogen embrittlement and hot cracking tendencies, and preventing oxidation of the raw materials, thereby ensuring that the magnesium alloy has good overall performance.

[0046] Melting magnesium ingot steps

[0047] Under protective gas and 680-750°C conditions, the preheated magnesium ingot is melted to obtain magnesium liquid.

[0048] According to one embodiment of the present invention, the shielding gas is a mixture of SF6 (sulfur hexafluoride) and N2 (nitrogen), and the volume ratio of SF6 to N2 can be 1:300 to 800, preferably 1:350 to 650, and more preferably 1:400 to 600. Such melting conditions are conducive to the full melting of the magnesium ingot to form magnesium liquid, preventing the occurrence of particle residues in the magnesium liquid, thereby improving the comprehensive performance of the magnesium alloy. The present invention has found that the use of nitrogen instead of carbon dioxide can significantly improve the comprehensive performance coefficient of the magnesium alloy, although the principle is still unclear.

[0049] According to one embodiment of the present invention, the melting temperature may be 680-750°C, preferably 685-745°C, and more preferably 690-740°C.

[0050] Preparation steps of magnesium alloy liquid

[0051] Under protective gas and 700-800° C. conditions, the preheated magnesium-lanthanum master alloy is added to magnesium liquid to melt the magnesium-lanthanum master alloy, and then the preheated manganese powder is added thereto and stirred for 60-150 minutes to obtain a mixed liquid; the mixed liquid is refined and slag-removed to obtain a magnesium alloy liquid.

[0052] According to one embodiment of the present invention, the shielding gas is a mixture of SF6 (sulfur hexafluoride) and N2 (nitrogen), and the volume ratio of SF6 to N2 can be 1:300 to 800, preferably 1:350 to 650, and more preferably 1:400 to 600. The present invention has found that replacing carbon dioxide with nitrogen can significantly improve the overall performance coefficient of magnesium alloys, although the principle is still unclear.

[0053] According to one embodiment of the present invention, the temperature when adding the magnesium-lanthanum master alloy may be 700-800°C, preferably 710-790°C, and more preferably 720-780°C.

[0054] According to one embodiment of the present invention, the stirring time may be 60 to 150 min, preferably 70 to 130 min, and more preferably 80 to 120 min.

[0055] In the present invention, stirring can be achieved using any method or device known in the art, which will not be described in detail here.

[0056] According to one embodiment of the present invention, argon (Ar) is used to refine the mixed solution, and the flow rate of argon can be 80-150 cm 3 / min, preferably 85 to 135 cm 3 / min, more preferably 90 to 120 cm 3 / min.

[0057] According to one embodiment of the present invention, slagging may include the following steps:

[0058] a) drying the deslagging agent at 200-500°C for 2-6 hours, then adding the dried deslagging agent to the refined mixed solution at 700-800°C to melt the deslagging agent;

[0059] b) stirring the mixed solution at a speed of 60-120 rpm for 10-20 minutes, and then allowing the mixed solution to stand for 20-60 minutes, and then removing the slag liquid on the surface and the mixed solution with a thickness of 5-10 mm below the slag liquid to obtain a slag-removed mixed solution.

[0060] According to one embodiment of the present invention, in step a), the drying temperature may be 200-500° C., preferably 200-400° C., more preferably 250-400° C. The drying time may be 2-6 hours, preferably 2-5 hours, more preferably 3-5 hours.

[0061] According to a specific embodiment of the present invention, in step a), the temperature for adding the dried slagging agent may be 700-800°C, preferably 750-800°C, and more preferably 750-790°C.

[0062] According to a specific embodiment of the present invention, in step b), the stirring speed can be 60-120 rpm, preferably 65-115 rpm, more preferably 70-110 rpm. The stirring time can be 10-20 min, preferably 12-20 min, more preferably 12-18 min.

[0063] According to a specific embodiment of the present invention, in step b), the time for standing the mixed solution can be 20 to 60 minutes, preferably 20 to 50 minutes, and more preferably 25 to 50 minutes.

[0064] According to a specific embodiment of the present invention, in step b), the thickness of the mixed liquid below the slag liquid removed can be 5 to 10 mm, preferably 6 to 10 mm, and more preferably 6 to 9 mm.

[0065] In the present invention, the slagging agent can be a commercially available product, or can be prepared by referring to the existing slagging agent formula, which will not be described in detail here.

[0066] According to a preferred embodiment of the present invention, the slagging agent is made of the following components by weight:

[0067] MgCl2 32-38wt%, KCl 31-37wt%, BaCl2 10-16wt%, CaF2 6-12wt%, CaCl2 1-7wt%, NaCl 1-7wt% and MgO 0.5-2wt%.

[0068] In the slagging agent raw materials of the present invention, the amount of MgCl2 can be 32-38wt%, preferably 33-37wt%, and more preferably 34-36wt%. The amount of KCl can be 31-37wt%, preferably 32-36wt%, and more preferably 33-35wt%. The amount of BaCl2 can be 10-16wt%, preferably 11-15wt%, and more preferably 12-14wt%. The amount of CaF2 can be 6-12wt%, preferably 7-11wt%, and more preferably 8-10wt%. The amount of CaCl2 can be 1-7wt%, preferably 2-6wt%, and more preferably 3-5wt%. The amount of NaCl can be 1-7wt%, preferably 2-6wt%, and more preferably 3-5wt%. The amount of MgO can be 0.5-2wt%, preferably 0.6-1.8wt%, and more preferably 0.8-1.6wt%.

[0069] The slagging agent can be added in any manner known in the art and will not be described in detail herein, for example, a rotary feeding method can be used.

[0070] According to one embodiment of the present invention, after slagging, the mixed liquid may be allowed to stand for 45 to 90 minutes, preferably 50 to 85 minutes, and more preferably 55 to 80 minutes.

[0071] According to one embodiment of the present invention, the mixed solution can be allowed to stand for an additional 20 to 60 minutes at 680 to 780°C to obtain a magnesium alloy liquid. The temperature of the mixed solution can be 680 to 780°C, preferably 690 to 770°C, and more preferably 700 to 760°C. The mixed solution can be allowed to stand for 20 to 60 minutes, preferably 25 to 55 minutes, and more preferably 30 to 50 minutes. The above process conditions are beneficial for improving the overall performance of the magnesium alloy.

[0072] Preparation steps of primary magnesium alloy ingots

[0073] The magnesium alloy liquid is poured into a mold at 650-750° C. and cooled to obtain a primary magnesium alloy ingot.

[0074] According to one embodiment of the present invention, the pouring temperature may be 650-750°C, preferably 660-740°C, and more preferably 670-720°C.

[0075] According to one embodiment of the present invention, before pouring, the mold may be preheated at 100-300° C. In the present invention, the temperature of the preheated mold may be 100-300° C., preferably 120-280° C., and more preferably 150-250° C.

[0076] In the present invention, the mold may be any magnesium alloy mold known in the art, such as a high-temperature resistant iron casting mold.

[0077] In the present invention, cooling can be achieved using any method or device known in the art, including but not limited to air cooling, wind cooling or water cooling.

[0078] Reasonable casting conditions are conducive to improving the fluidity and structural uniformity of the alloy, ensuring that the magnesium alloy has both good thermal conductivity and elongation, thereby improving the comprehensive performance coefficient of the magnesium alloy.

[0079] Extrusion steps

[0080] The primary magnesium alloy ingot is annealed and then extruded at 200-500° C. to obtain the magnesium alloy.

[0081] According to one embodiment of the present invention, the annealing is to heat treat the magnesium alloy ingot at 300-500° C. for 10-20 hours.

[0082] According to a specific embodiment of the present invention, the heat treatment temperature may be 300-500°C, preferably 320-480°C, more preferably 350-450°C. The heat treatment time may be 10-20 hours, preferably 12-18 hours, more preferably 13-17 hours.

[0083] According to a preferred embodiment of the present invention, the method may further include a step of turning the surface of the annealed primary magnesium alloy ingot.

[0084] According to one embodiment of the present invention, the annealed primary magnesium alloy ingot can be turned into a cylinder. The outer diameter of the cylinder can be 20 to 60 mm, preferably 25 to 55 mm, and more preferably 30 to 50 mm. The height of the cylinder can be 20 to 60 mm, preferably 25 to 55 mm, and more preferably 30 to 50 mm. Proper turning conditions can make the surface of the primary magnesium alloy ingot smoother, which helps improve the stability of the extrusion process.

[0085] According to a preferred embodiment of the present invention, the extrusion may be forward extrusion.

[0086] According to one embodiment of the present invention, the extrusion temperature may be 200-500°C, preferably 250-450°C, and more preferably 300-400°C.

[0087] According to one embodiment of the present invention, the extrusion ratio may be 12 to 20: 1, preferably 13 to 19: 1, and more preferably 14 to 18: 1. The above extrusion conditions are beneficial for grain refinement and improvement of microstructure uniformity, thereby improving the comprehensive performance coefficient of the magnesium alloy.

[0088] In the present invention, any equipment known in the art may be used for extrusion, such as a forward single-action extruder or a forward double-action extruder.

[0089] According to one embodiment of the present invention, the comprehensive performance coefficient ε of the magnesium alloy is at least 15 W / (m·K), preferably at least 15.2 W / (m·K), and more preferably at least 15.4 W / (m·K).

[0090] According to one embodiment of the present invention, the magnesium alloy may have an elongation of at least 12%, preferably at least 12.2%, and more preferably at least 12.3%. The thermal conductivity may be at least 124 W / (m·K), preferably at least 124.2 W / (m·K), and more preferably at least 124.5 W / (m·K).

[0091] <Test method>

[0092] Elongation test: Determined in accordance with GB / T228.1-2021.

[0093] Thermal conductivity test: NETZSCH LFA427 laser thermal conductivity meter was used for measurement.

[0094] <Ingredients>

[0095] Unless otherwise specified, the raw materials in the following examples are all commercially available products.

[0096] The slagging agent is made of the following components by weight:

[0097] MgCl2 35wt%, KCl 34wt%, BaCl2 13wt%, CaF2 9wt%, CaCl2 4wt%, NaCl 4wt% and MgO 1wt%.

[0098] Example 1

[0099] The chemical composition of the magnesium alloy is as follows by weight percentage: La 1.0wt%, Mn 0.5wt%, and the balance is magnesium and unavoidable impurities. The following steps are used for preparation:

[0100] 1) A magnesium ingot, a Mg-25 wt% La master alloy and a manganese powder were provided according to the chemical composition of the magnesium alloy, and the magnesium ingot, the Mg-25 wt% La master alloy and the manganese powder were preheated at 200° C. for 5 h.

[0101] 2) placing the magnesium ingot in a resistance furnace, and melting the preheated magnesium ingot under protective gas (a mixture of SF6 and N2 with a volume ratio of 1:500) at 720° C. to obtain magnesium liquid.

[0102] 3) Under protective gas (a mixture of SF6 and N2 with a volume ratio of 1:500) and a temperature of 740°C, the preheated Mg-25wt%La master alloy was added to the magnesium liquid to melt the Mg-25wt%La master alloy, and then the preheated manganese powder was added thereto and stirred for 90 minutes to obtain a mixed solution; a flow rate of 100cm 3 / min of argon gas to refine the mixed liquid; then, the slag removing agent is dried at 300°C for 3h, and then, the dried slag removing agent is added to the refined mixed liquid in a rotary cloth manner at 780°C to melt the slag removing agent, and then, the mixed liquid is stirred at a speed of 85rpm for 15min, and then, the mixed liquid is allowed to stand for 30min, and then, the slag liquid on the surface and the mixed liquid with a thickness of 8mm below the slag liquid are removed to obtain a slag-removed mixed liquid; then, the slag-removed mixed liquid is allowed to stand for 60min, and then, the slag-removed mixed liquid is allowed to stand for another 30min at 720°C to obtain a magnesium alloy liquid.

[0103] 4) Preheating the iron casting mold at 200° C., then pouring the magnesium alloy liquid into the preheated iron casting mold at 680° C., and then air-cooling to room temperature (25° C.) to obtain a primary magnesium alloy ingot.

[0104] 5) The primary magnesium alloy ingot was annealed by heat treatment at 400° C. for 15 h, and then the surface of the primary magnesium alloy ingot was turned into a cylinder with an outer diameter of 40 mm and a height of 40 mm. The turned primary magnesium alloy ingot was then forward extruded at 350° C. at an extrusion ratio of 16:1 to obtain a magnesium alloy.

[0105] Comparative Example 1

[0106] Except for the following parameters and settings, the rest are the same as Example 1:

[0107] In this comparative example, the chemical composition of the magnesium alloy is as follows by weight percentage: La 0.2 wt %, Mn 0.5 wt %, and the balance being magnesium and unavoidable impurities.

[0108] The preheating time of step 1) is 3 hours. The pouring temperature of step 4) is 700°C.

[0109] Comparative Example 2

[0110] Except for the following parameters and settings, the rest are the same as Example 1:

[0111] In this comparative example, the chemical composition of the magnesium alloy is as follows by weight percentage: La 0.6 wt %, Mn 0.5 wt %, and the balance being magnesium and unavoidable impurities.

[0112] The preheating time of step 1) is 4 hours. The pouring temperature of step 4) is 690°C.

[0113] Comparative Example 3

[0114] Except for the following parameters and settings, the rest are the same as Example 1:

[0115] In this comparative example, the chemical composition of the magnesium alloy is as follows by weight percentage: La 2.0 wt %, Mn 0.5 wt %, and the balance being magnesium and unavoidable impurities.

[0116] The preheating time of step 1) is 4 hours. The pouring temperature of step 4) is 690°C.

[0117] Comparative Example 4

[0118] The experiment was conducted according to Example 5 of CN117026036A. The test results are shown in Table 1.

[0119] Experimental Example 1

[0120] The magnesium alloys prepared in Example 1 and Comparative Examples 1 to 3 were tested for elongation and thermal conductivity. The test results are shown in Table 1.

[0121] Table 1 Performance test results of magnesium alloy

[0122] Group Elongation (%) Thermal conductivity (W / (m·K)) Comprehensive performance coefficient (W / (m·K)) Example 1 12.39 124.64 15.44 Comparative Example 1 8.44 128.50 10.85 Comparative Example 2 9.78 125.00 12.22 Comparative Example 3 9.83 124.00 12.19 Comparative Example 4 8.1 138.70 11.23

[0123] As can be seen from Table 1, the magnesium alloy prepared in the present invention has both higher elongation and thermal conductivity, and a higher comprehensive performance coefficient.

[0124] The present invention is not limited to the above-mentioned embodiments. Any modification, improvement, or substitution that can be conceived by those skilled in the art without departing from the essential content of the present invention shall fall within the scope of the present invention.

Claims

1. A method for improving the comprehensive performance coefficient of a magnesium alloy, characterized in that: The following steps are involved: 1) providing raw materials according to the chemical composition of a magnesium alloy and preheating the raw materials; wherein the chemical composition of the magnesium alloy is as follows by weight percentage: La 0.8-1.2 wt%, Mn 0.2-1.0 wt%, and the balance is magnesium and unavoidable impurities; the raw materials include a magnesium ingot, a magnesium-lanthanum master alloy, and manganese powder; 2) melting the preheated magnesium ingot under a protective gas at 680-750° C. to obtain magnesium liquid; wherein the protective gas is composed of SF6 and N2, and the volume ratio of SF6 to N2 is 1:300-800; 3) adding the preheated magnesium-lanthanum master alloy to magnesium liquid under a protective gas at 700-800° C. to melt the magnesium-lanthanum master alloy, then adding the preheated manganese powder thereto, stirring for 60-150 minutes to obtain a mixed solution; refining and deslagging the mixed solution to obtain a magnesium alloy liquid; wherein the protective gas is composed of SF6 and N2, and the volume ratio of SF6 to N2 is 1:300-800; 4) pouring the magnesium alloy liquid into a mold at 650-750° C. and cooling it to obtain a primary magnesium alloy ingot; 5) annealing the primary magnesium alloy ingot, and then extruding it at 200-500° C. to obtain a magnesium alloy; Among them, the comprehensive performance coefficient ε=λ×δ; where λ is thermal conductivity, the unit is W / (m·K); δ is elongation, the unit is %.

2. The method according to claim 1, characterized in that In step 1), the chemical composition of the magnesium alloy is as follows by weight percentage: La 0.85-1.15wt%, Mn 0.3-0.8wt%, and the balance is magnesium and unavoidable impurities.

3. The method according to claim 1, characterized in that In step 1), the preheating temperature is 100-300° C., and the preheating time is 1-8 hours.

4. The method according to claim 1, wherein In step 2), the volume ratio of SF6 to N2 is 1:350-650.

5. The method according to claim 1, wherein In step 3), the volume ratio of SF6 to N2 is 1:350-650.

6. The method according to claim 1, characterized in that In step 3), the mixed solution is refined with argon gas at a flow rate of 80 to 150 cm 3 / min.

7. The method according to claim 1, characterized in that In step 3), after slagging, the mixed solution is allowed to stand for 45 to 90 minutes, and then allowed to stand for another 20 to 60 minutes at 680 to 780° C. to obtain a magnesium alloy liquid.

8. The method according to claim 1, characterized in that In step 5), the extrusion is forward extrusion, and the extrusion ratio is 12 to 20:

1.

9. The method according to claim 1, characterized in that The comprehensive performance coefficient ε of magnesium alloy is above 15W / (m·K).

10. The method according to any one of claims 1 to 9, characterized in that The magnesium alloy has an elongation δ of 12% or more and a thermal conductivity λ of 124 W / (m·K) or more; Among them, the elongation is measured in accordance with GB / T228.1-2021; the thermal conductivity is measured using a NETZSCH LFA427 laser thermal conductivity meter.