High-strength and high-thermal-conductivity magnesium alloy and preparation method thereof

Abstract

The invention belongs to the technical field of non-ferrous metal materials, and particularly relates to a high-strength and high-thermal-conductivity magnesium alloy and a preparation method thereof. The high-strength and high-thermal-conductivity magnesium alloy comprises Zn, mischmetal, Al, X elements and the balance Mg and inevitable impurity elements, the X elements are at least one of Sb, Sn and Y. The high-strength and high-thermal-conductivity magnesium alloy is obtained by melting Mg ingots, Al ingots, Zn ingots, mischmetal and Mg-X, refining, deslagging and casting. Alloy elements such as Zn and La / Ce mixed rare earth which have small influence on the thermal conductivity of the magnesium alloy are added into the alloy, the negative influence of the alloy elements on the thermal conductivity is reduced, the casting performance of the alloy is optimized, grains are refined, the mechanical property of the alloy is improved by adding the La / Ce mixed rare earth and the Al element, a large number of second phases are formed at the grain boundary, and the thermal conductivity of the magnesium alloy is improved. And secondly, compared with pinning of the grain boundary, the mechanical property of the alloy is further enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of nonferrous metal materials, and more specifically relates to a high-strength and high-thermal-conductivity magnesium alloy and a preparation method thereof. Background Art

[0002] Magnesium is a common light structural material in engineering applications. Its density is 1.74g / cm 3 , which is 2 / 3 of aluminum and 1 / 4 of steel, has the advantages of high specific strength, high specific stiffness, good thermal conductivity and electrical conductivity, damping and vibration reduction, electromagnetic shielding, easy processing and easy recycling, etc. In the future, it will gradually have more and more important application value and broad application prospects in the fields of automobiles, 3C products, aerospace, etc.

[0003] At present, the 3C, automobile and aerospace manufacturing fields have made higher requirements on the thermal conductivity and heat dissipation performance of heat dissipation and heat transfer structural materials. Studies have shown that the heat dissipation rate of magnesium alloys is higher than that of aluminum alloys, and the density is relatively low. It has broad application prospects in the field of lightweight heat dissipation materials in the future. Under normal temperature conditions, the thermal conductivity of pure magnesium can reach 154W / (m·K), but its mechanical properties are unsatisfactory. Among the many methods for strengthening and toughening magnesium alloys, alloying is the most convenient and direct way to improve its mechanical properties, but this method will reduce the thermal conductivity of magnesium alloys to a certain extent. The most commonly used AZ series of magnesium alloy materials have a thermal conductivity of less than 90W / (m·K), and even the thermal conductivity of AZ91D is only 51W / (m·K), which is far from meeting the needs of heat dissipation structural parts.

[0004] Therefore, how to obtain a magnesium alloy material with both high strength and high thermal conductivity and expand the application of magnesium alloys in 3C, automobiles, and aerospace has become a difficult problem that technical personnel in this field urgently need to overcome. Summary of the invention

[0005] The purpose of the present invention is to provide a high-strength and high-thermal conductivity magnesium alloy and a preparation method thereof, and more specifically to a high-strength and high-thermal conductivity rare earth magnesium alloy and a preparation method thereof. By adding high Zn and La\Ce rare earths, the mechanical properties of the magnesium alloy are improved while ensuring its high thermal conductivity. By adding a small amount of Al, the casting performance of the alloy is optimized. The X element (Sb, Sn, Y) can refine the grain size and improve the mechanical properties of the alloy, so as to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is to provide a high-strength and high-thermal-conductivity rare earth magnesium alloy, which comprises, by mass percentage:

[0008] Zn 8.0-12.0%, mixed rare earth 2.5-3.5%, Al 0.3-0.5%, X element 0-2.0%, the balance is Mg and unavoidable impurity elements;

[0009] The X element is at least one of Sb, Sn and Y.

[0010] Furthermore, the mixed rare earth includes 66.0-66.3 wt. % of Ce and 33.0-33.5 wt. % of La, and the remainder is inevitable impurity elements.

[0011] In the present invention, the content of each impurity element is less than 0.05%.

[0012] The second technical solution of the present invention is to provide a method for preparing the above-mentioned high-strength and high-thermal-conductivity rare earth magnesium alloy, the steps comprising:

[0013] Melting Mg ingots, Al ingots, Zn ingots, mixed rare earth and Mg-X, refining and deslagging, and then casting to obtain the high-strength and high-thermal-conductivity rare earth magnesium alloy;

[0014] The Mg-X is at least one of Mg-Sb, Mg-Sn and Mg-Y.

[0015] Furthermore, SF6+CO2 is introduced into the Mg ingot, Al ingot, Zn ingot, mixed rare earth and Mg-X for protection when they are melted.

[0016] Furthermore, the melting temperature of the Mg ingot is 700-740°C.

[0017] Furthermore, the melting temperature of the Al ingot and the Zn ingot is 710-730°C.

[0018] Furthermore, the melting temperature of the mixed rare earth and Mg-X is 740-750°C.

[0019] Furthermore, the refining and deslagging temperature is 730-760°C.

[0020] Furthermore, the refining and slag removal is performed by adding 2% of the total mass of the raw materials into RJ-5 solvent for refining for 20-30 minutes.

[0021] In the present invention, the alloying efficiency of the Al ingot used is 100%, the alloying efficiency of the Zn ingot is 100%, and the alloying efficiency of the mixed rare earth is 80%.

[0022] The third technical solution of the present invention is to provide an application of the above-mentioned high-strength and high-thermal conductivity rare earth magnesium alloy in 3C, automobile and aerospace manufacturing.

[0023] The present invention discloses the following technical effects:

[0024] The present invention adds alloy elements such as Zn and La / Ce mixed rare earth that have little effect on the thermal conductivity of the magnesium alloy to the alloy, thereby reducing the negative impact of the alloy elements on the thermal conductivity. In addition, the addition of La / Ce mixed rare earth and Al element optimizes the casting performance of the alloy, refines the grains, improves the mechanical properties of the alloy, forms a large amount of second phases at the grain boundaries, and further strengthens the mechanical properties of the alloy.

[0025] The preparation method of the present invention is simple and low-cost, and can be widely used in the fields of 3C, automobiles, aerospace heat dissipation parts, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 The metallographic structure diagram of the high-strength and high-thermal-conductivity rare earth magnesium alloy prepared in Example 1, wherein (a) is magnified 50 times, (b) is magnified 100 times, (c) is magnified 200 times, and (d) is magnified 500 times;

[0028] Figure 2 The tensile fracture morphology of the high-strength and high-thermal-conductivity rare earth magnesium alloy prepared in Example 1 of the present invention, wherein (a) is magnified 20 times, (b) is magnified 50 times, and (c) is magnified 50 times. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0032] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] The raw materials and reagents used in the specific embodiments of the present invention are all commercially available products.

[0035] Unless otherwise specified, the "%" in the specific embodiments of the present invention refers to mass percentage.

[0036] The mixed rare earth used in the specific embodiment of the present invention is La / Ce mixed rare earth, wherein the mass ratio of La to Ce is 1:2.

[0037] Example 1

[0038] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0039] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 10.9%, mixed rare earth 3.3%, Al 0.3%, Sn 0.07%, Sb 0.01%, Y 0.01% and balance Mg;

[0040] S2. Preheat and dry the above raw materials at 120±5℃ for 3h;

[0041] S3. After preheating and drying, SF6+CO2 is introduced for protection, and a layer of RJ-2 solvent is laid at the bottom of the smelting furnace to prevent oxidation and combustion of the subsequent magnesium ingot during melting. Then the Mg ingot is put into the smelting furnace, and the temperature is raised to 687°C to melt the Mg ingot. Subsequently, the temperature is adjusted to 718°C, and Al ingots and Zn ingots are put in. After melting, the temperature is adjusted to 732°C, and La / Ce mixed rare earth and Mg-X are put in, and they are fully smelted to obtain alloy liquid;

[0042] S4, adjusting the temperature of the alloy liquid to 738°C, adding 2% of the total amount of raw materials into RJ-5 flux, stirring with argon gas, and then standing for 20 minutes to obtain a refined alloy liquid;

[0043] S5. Casting the refined alloy liquid to obtain a high-strength and high-thermal-conductivity rare earth magnesium alloy.

[0044] Figure 1 The metallographic organization diagram of the high-strength and high-thermal-conductivity rare earth magnesium alloy obtained in Example 1, wherein (a) is magnified 50 times, (b) is magnified 100 times, (c) is magnified 200 times, and (d) is magnified 500 times. As can be seen from the figure, the second phase in the alloy is mostly precipitated along the grain boundary, and the morphology is mostly continuously distributed, but no ring-shaped second phase is formed along the grain boundary. For cast metals, the increase of dispersed second phases is more unfavorable to thermal conductivity, so the continuously distributed second phase has less effect on the thermal conductivity of the alloy than the dispersed second phase.

[0045] Figure 2 The tensile fracture morphology of the high-strength and high-thermal-conductivity rare earth magnesium alloy prepared in Example 1 of the present invention, wherein (a) is magnified 20 times, (b) is magnified 50 times, and (c) is magnified 50 times.

[0046] Example 2

[0047] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0048] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 10.6%, mixed rare earth 3.5%, Al 0.5%, Sn 0.07%, Sb 0.01%, Y 0.01% and balance Mg;

[0049] S2-S5, same as Example 1.

[0050] Example 3

[0051] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0052] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 8.01%, mixed rare earth 3.01%, Al 0.3%, Sn 0.07%, Sb 0.01%, Y 0.01% and balance Mg;

[0053] S2-S5, same as Example 1.

[0054] Example 4

[0055] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0056] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 8.01%, mixed rare earth 3.01%, Al 0.5%, Sn 0.07%, Sb 0.01%, Y 0.01% and balance Mg;

[0057] S2-S5, same as Example 1.

[0058] Example 5

[0059] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0060] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 11.89%, mixed rare earth 3.03%, Al 0.3%, Sn 0.068%, Sb 0.011%, Y 0.009% and balance Mg;

[0061] S2-S5, same as Example 1.

[0062] Example 6

[0063] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0064] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 11.99%, mixed rare earth 3.08%, Al 0.5%, Sn 0.065%, Sb 0.013%, Y 0.009% and balance Mg;

[0065] S2-S5, same as Example 1.

[0066] Example 7

[0067] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0068] S1. According to Zn 10.9%, mixed rare earth 3.3%, Al 0.42% and the balance Mg, prepare Mg ingot, Al ingot, Zn ingot and La / Ce mixed rare earth;

[0069] S2. Preheat and dry the above raw materials at 120±5℃ for 3h;

[0070] S3, after preheating and drying, SF6+CO2 is introduced for protection, the Mg ingot is put into the smelting furnace, the temperature is raised to 683°C, the Mg ingot is melted, and then the temperature is adjusted to 718°C, Al ingot and Zn ingot are put in, after melting, the temperature is adjusted to 732°C, La / Ce mixed rare earth is put in, and fully smelted to obtain alloy liquid;

[0071] S4, adjusting the temperature of the alloy liquid to 738°C, adding 2% RJ-5 flux by mass of the magnesium ingot, stirring with argon gas, and then standing for 20 minutes to obtain a refined alloy liquid;

[0072] S5. Casting the refined alloy liquid to obtain a high-strength and high-thermal-conductivity rare earth magnesium alloy.

[0073] Example 8

[0074] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0075] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 10.38%, mixed rare earth 3.31%, Al 0.3%, Sn 0.07%, Sb 0.01%, Y 0.01% and balance Mg;

[0076] S2-S5, same as Example 1.

[0077] Comparative Example 1

[0078] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0079] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 7.21%, mixed rare earth 3.31%, Al 0.3%, Sn 0.07%, Sb 0.01%, Y 0.01% and balance Mg;

[0080] S2-S5, same as Example 1.

[0081] Comparative Example 2

[0082] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0083] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 13.34%, mixed rare earth 3.31%, Al 0.3%, Sn 0.07%, Sb 0.01%, Y 0.01% and balance Mg;

[0084] S2-S5, same as Example 1.

[0085] Comparative Example 3

[0086] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0087] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 10.38%, mixed rare earth 1.32%, Al 0.3%, Sn 0.07%, Sb 0.01%, Y 0.01% and balance Mg;

[0088] S2-S5, same as Example 1.

[0089] Comparative Example 4

[0090] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0091] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 10.38%, mixed rare earth 4.1%, Al 0.3%, Sn 0.07%, Sb 0.01%, Y 0.01% and balance Mg;

[0092] S2-S5, same as Example 1.

[0093] Comparative Example 5

[0094] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0095] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 10.38%, mixed rare earth 3.31%, Al 0.2%, Sn 0.07%, Sb 0.01%, Y 0.01% and balance Mg;

[0096] S2-S5, same as Example 1.

[0097] Comparative Example 6

[0098] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0099] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 10.38%, mixed rare earth 3.31%, Al 0.6%, Sn 0.07%, Sb 0.01%, Y0.01% and balance Mg;

[0100] S2-S5, same as Example 1.

[0101] Comparative Example 7

[0102] The preparation steps of high-strength and high-thermal-conductivity rare earth magnesium alloy include:

[0103] S1. Prepare Mg ingot, Al ingot, Zn ingot, La / Ce mixed rare earth, Mg-X (Mg-Sn, Mg-Sb and Mg-Y) according to Zn 10.38%, mixed rare earth 3.31%, Sn 0.07%, Sb 0.01%, Y 0.01% and balance Mg;

[0104] S2-S5, same as Example 1.

[0105] The mechanical properties and thermal conductivity of the magnesium alloys prepared in Examples 1-8 and Comparative Examples 1-7 were tested, and the results are shown in Table 1.

[0106] Table 1

[0107]

[0108]

[0109] It can be seen from the data in Table 1 that the mechanical properties and thermal conductivity of the magnesium alloys prepared in Examples 1-7 of the present invention are improved compared with AZ91D, among which the thermal conductivity is improved more significantly. When the Zn element is not within the scope of the present invention, such as the data of Comparative Examples 1 and 2, it can be seen that when the Zn content is lower than the lower limit, its electrical conductivity is slightly improved, but its mechanical properties are reduced, and when the Zn content is higher than the upper limit, the mechanical properties are improved but its thermal conductivity is significantly reduced; when the La / Ce rare earth elements are not within the scope of the present invention, such as the data of Comparative Examples 3 and 4, it can be seen that the addition of La / Ce elements can optimize the comprehensive mechanical properties of the alloy, but it will also affect the thermal conductivity of the alloy; when the Al element is not within the scope of the present invention, such as the data of Comparative Examples 5 to 7, it can be seen that the addition of Al elements can increase the mechanical properties of the alloy, but it has a greater damage to the thermal conductivity.

[0110] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0111] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-strength and high-thermal-conductivity rare earth magnesium alloy, characterized in that: In terms of mass percentage, the components include: Zn 8.0-12.0%, mixed rare earth 2.5-3.5%, Al 0.3-0.5%, X element 0-2.0%, the balance is Mg and unavoidable impurity elements; The X element is at least one of Sb, Sn and Y; The mixed rare earth comprises 66.0-66.3 wt. % of Ce and 33.0-33.5 wt. % of La, and the remainder is inevitable impurity elements.

2. The method for preparing a high-strength and high-thermal-conductivity rare earth magnesium alloy according to claim 1, characterized in that the steps include: Melting Mg ingots, Al ingots, Zn ingots, mixed rare earth and Mg-X, refining and deslagging, and then casting to obtain the high-strength and high-thermal-conductivity rare earth magnesium alloy; The Mg-X is at least one of Mg-Sb, Mg-Sn and Mg-Y.

3. The preparation method according to claim 2, characterized in that: When the Mg ingot, Al ingot, Zn ingot, mixed rare earth and Mg-X are melted, SF6+CO2 is introduced for protection.

4. The preparation method according to claim 2, characterized in that: The melting temperature of the Mg ingot is 700-740°C.

5. The preparation method according to claim 2, characterized in that: The melting temperatures of the Al ingot and the Zn ingot are 710-730°C.

6. The preparation method according to claim 2, characterized in that: The melting temperature of the mixed rare earth and Mg-X is 740-750°C.

7. The preparation method according to claim 2, characterized in that: The refining and deslagging temperature is 730-760°C.

8. The preparation method according to claim 2, characterized in that: The refining and slag removal is performed by adding 2% of the total mass of the raw materials into RJ-5 solvent for refining for 20-30 minutes.

9. Application of the high-strength and high-thermal-conductivity rare earth magnesium alloy as claimed in claim 1 in 3C, automobile and aerospace manufacturing.

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