Aging-free high-thermal-conductivity magnesium alloy plate and preparation method thereof

Abstract

The invention discloses an aging-free high-thermal-conductivity magnesium alloy plate and a preparation method thereof, and belongs to the field of magnesium alloy. The alloy comprises the following components in percentage by weight: 6wt%-12wt% of Gd, 1wt%-4wt% of Er, 2wt%-12wt% of Zn, 0wt%-2wt% of Mn and the balance of Mg and inevitable impurities. The method comprises the following steps that S1, raw materials corresponding to all components in the alloy are proportionally matched and smelted, and as-cast alloy is obtained; and S2, the as-cast alloy is subjected to homogenization treatment, and then through multi-pass hot rolling, the high-thermal-conductivity rare earth magnesium alloy plate is prepared. The Mg-Gd-Er-Zn-Mn alloy plate prepared by the invention is a metal material with excellent thermal conductivity, and the thermal conductivity of the Mg-Gd-Er-Zn-Mn alloy plate can reach 134.6 W / (m.K).

Description

Technical Field

[0001] The present invention belongs to the field of magnesium alloy materials and relates to a high-thermal-conductivity magnesium alloy plate suitable for being free of aging and a preparation method thereof. Background Art

[0002] Magnesium alloys are widely used in transportation, aerospace, and other fields due to their high specific stiffness, specific strength, low density, and high thermal conductivity. With the rapid development of aerospace and communications technology, the demand for high-thermal-conductivity magnesium alloys is becoming increasingly urgent. For example, the heat dissipation capacity of electronic components within a limited heat dissipation space directly determines their service life.

[0003] Currently developed alloys such as Mg-Gd, Mg-Y, Mg-Gd-Y, and Mg-Gd-Er all exhibit high strength. However, the addition of alloying elements often leads to an increase in solute atoms and impurities in the magnesium matrix, causing lattice distortion and hindering the movement of heat transfer carriers—electrons and phonons—significantly reducing thermal conductivity. Therefore, improving the thermal conductivity of rare earth magnesium alloys has become an urgent research issue. Numerous studies have demonstrated that the influence of solute atoms on the thermal conductivity of magnesium alloys is far greater than that of the second phase. Therefore, the addition of Zn (Zn) to Mg rare earth alloys forms a second phase with the rare earth elements, consuming the rare earth atoms in the magnesium matrix and thereby improving the thermal conductivity of magnesium alloys. Therefore, adding a certain proportion of Zn to Mg rare earth alloys is a potential method for improving the strength and thermal conductivity of magnesium alloys.

[0004] The type and content of the second phase in the Mg-RE-Zn alloy will change with the size of Zn / RE. In 2021, Jia Linyue and others obtained a magnesium alloy containing LPSO phase and with a tensile strength of up to 549MPa by extruding the Mg-12Gd-1Er-1Zn-Zr alloy. However, its thermal conductivity is lower than 80W / (m·K). This is because the Zn content is too small to consume a large amount of rare earth atoms dissolved in the matrix, resulting in a significant decrease in thermal conductivity, and aging becomes the main means to improve thermal conductivity. However, when the Zn content gradually increases, a large amount of MgZn3RE2 phase (W phase) can be formed in the matrix, and the rare earth atoms are consumed in large quantities, which effectively reduces the lattice distortion of the magnesium matrix and greatly reduces the scattering of electrons and phonons, thereby improving thermal conductivity. Therefore, the formation of W phase by regulating the content and ratio of Zn and RE in Mg-Gd-Zn alloys has become a potential method for preparing high-strength and high-thermal conductivity structural functional materials.

[0005] Traditional thermal deformation methods for magnesium alloys primarily include extrusion, rolling, and forging. However, these methods are not suitable for the cost-effective, large-scale production of large-scale magnesium alloy sheets. Currently, the development and research of technologies for producing magnesium alloy rolled sheets and sheets has garnered significant attention. Therefore, the development of a functional magnesium alloy sheet with high thermal conductivity and its preparation process is crucial for practical applications. Summary of the Invention

[0006] To address the low thermal conductivity of existing Mg-RE-Zn alloys, the present invention provides an aging-free, high-thermal-conductivity magnesium alloy sheet and its preparation method. This method alloys heavy rare earth elements (Gd, Er, etc.) with manganese, controls the Zn content, and hot-rolls the Mg-Gd-Er-Zn-Mn alloy to produce a high-thermal-conductivity rare earth magnesium alloy sheet.

[0007] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0008] An aging-free, wide-width, high-thermal-conductivity rare earth magnesium alloy plate, characterized in that the alloy composition comprises: 6wt% to 12wt% of Gd, 1wt% to 4wt% of Er, 2wt% to 12wt% of Zn, 0wt% to 2wt% of Mn, and the balance being Mg and unavoidable impurities; Mn is preferably not 0, and more preferably is 1-2%;

[0009] 1) preparing a Mg-Gd-Er-Zn-Mn alloy ingot; using commercially pure magnesium (99.99 wt.%), pure zinc (99.99 wt.%), Mg-Gd, Mg-Er, and Mg-Mn master alloys; polishing the metal elements and the master alloy surfaces to remove any oxide scale before smelting; smelting the alloy in a mixed SF6:N2 protective atmosphere; adding 3% to 5% refining agent; and finally casting the alloy into a square ingot at a casting temperature of 700° C. to 730° C.;

[0010] 2) Homogenization treatment: The cast ingot is placed in a heating furnace for homogenization treatment at 400°C for 12 hours, then quenched in room temperature water and cooled to room temperature before being processed into rolled square billets;

[0011] 3) Hot rolling deformation treatment: the cast ingot after homogenization treatment is placed in a heating furnace for preheating treatment, that is, the temperature of the cast ingot is raised to a predetermined rolling temperature for rolling deformation treatment, the preheating temperature is 400°C, and the preheating time is 10 to 30 minutes;

[0012] The preheated ingot is placed on a twin-roll mill for multiple hot rolling processes, with a reduction of 10-20% in each pass, a holding time of 10-20 minutes between passes, a holding temperature of 400°C, a total cumulative reduction of 90%, and finally cooled to room temperature in air to obtain a magnesium alloy rolled plate.

[0013] The essential features of the present invention are:

[0014] By adding rare earth elements Gd and Er, as well as Mn, to a magnesium matrix and controlling the Zn content, an alloy matrix containing a large amount of W phase is obtained. The alloy is subjected to a multi-pass hot rolling process with a total reduction of 90%, resulting in the precipitation of a large amount of dispersed W phase and α-Mn (a large amount of broken W phase, rod-shaped W phase, and α-Mn elemental substance are produced in the rolled alloy sheet), thereby significantly improving the alloy's thermal conductivity.

[0015] The beneficial effects of the present invention are:

[0016] 1. High thermal conductivity magnesium alloy is obtained through hot rolling process, which greatly improves production efficiency and reduces economic costs compared with conventional deformed rare earth magnesium alloy.

[0017] 2. Through multi-pass rolling with a total reduction of 90%, rare earth atoms and Mn atoms in the matrix are effectively precipitated, the alloy grain size is reduced, and the purpose of effectively improving the thermal conductivity of the alloy is achieved.

[0018] 3. The thermal conductivity of the Mg-Gd-Er-Zn-Mn alloy prepared by the method of the present invention is as high as 134.6W / (m·K).

[0019] 5. The equipment and process used in the present invention are simple, which is conducive to large-scale industrial application. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 The macromorphology of the Mg-8Gd-1Er-8Zn-1Mn alloy after 90% cumulative rolling in Example 5 (two); Figure 2 This is the SEM image of the microstructure of the Mg-8Gd-1Er-8Zn-1Mn alloy after 90% cumulative rolling in Example 5; Figure 3 The microstructure SEM image of the Mg-8Gd-1Er-8Zn-1Mn alloy after cumulative rolling of 90% in Example 5 (similar to Figure 2 scales vary); DETAILED DESCRIPTION The technical solution of the present invention is further described below with specific implementation methods. The following is implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operating processes are given, but the protection scope of the present invention is not limited to the following embodiments. Raw material preparation: Mg-8Gd-1Er-8Zn-1Mn alloy ingots were prepared; commercial pure magnesium (99.99wt.%), pure zinc (99.99wt.%), Mg-30Gd, Mg-20Er, and Mg-5Mn (wt.%) master alloys were used. Before smelting, the surfaces of the metal elements and master alloys were polished to a metallic luster. Alloy smelting process: first, put the pure magnesium ingot into a clean graphite crucible, and then put them into the furnace of a resistance furnace at 200-300℃ for preheating for about 10-20 minutes to remove moisture in the crucible; heat the preheated pure magnesium ingot and the graphite crucible together to 720-730℃, wait until the magnesium is completely melted, and use two gases for joint protection during the smelting process, nitrogen (N2) as the carrier gas and sulfur hexafluoride (SF6) as the protective gas, with a volume ratio of nitrogen to sulfur hexafluoride of 99:1; then put the prepared Mg-Gd master alloy into the molten magnesium melt, adjust the temperature to 730-750℃, and add pure Zn and Mg-Er master alloy blocks, keep them warm and let them stand for 10 to 15 minutes, then adjust the temperature to 730 to 740°C, add Mg-Mn master alloy blocks, keep them warm and let them stand for 10 to 15 minutes, remove the slag floating on the surface of the solution and stir it for 3 to 5 minutes; adjust the temperature to 720 to 730°C and let it stand for 15 minutes, take out the crucible and remove the slag, and when the melt temperature reaches 720 to 725°C, cast it into a metal mold, and obtain an ingot after the Mg alloy liquid is naturally cooled; the casting mold is a metal plate mold, which is then cut and processed into a plate-shaped casting ingot with dimensions of 60 mm in length, 30 mm in width and 20 mm in height. Homogenization treatment: Place the ingot in a box-type muffle furnace, set the holding temperature to 400°C, keep it warm for 12 hours, and then quench it in room temperature water. Example 1 Mg-8Gd-1Er-1Zn (1) The homogenized Mg-8Gd-1Er-1Zn alloy ingot was placed in a heating furnace at 400°C for 30 min. The subsequent rolling was carried out at a rolling speed of 0.17 m / s for 10 to 20 min per pass. When the total reduction reached 90%, the alloy was cooled to room temperature in air to obtain a rare earth magnesium alloy sheet with a thickness of 2 mm. (2) Take the alloy plate obtained in (1) The surface of the disc was polished smooth using #5000 sandpaper, and the thermal conductivity of the alloy was measured by using a German Netzsch laser thermal conductivity meter 457, which was 57.6 W / (m·K). Example 2 Mg-8Gd-1Er-4Zn The process was the same as in Example 1, except that Mg-8Gd-1Er-4Zn alloy with 4 wt.% Zn was used. After the total rolling reduction reached 90%, the alloy was cooled in air to room temperature, yielding a 2 mm thick rare earth magnesium alloy sheet. The measured thermal conductivity was 74.1 W / (m·K). Example 3 Mg-8Gd-1Er-6Zn The steps were the same as in Example 1, except that a Mg-8Gd-1Er-6Zn alloy with 6 wt.% Zn was used. The homogenization and rolling processes were identical, resulting in a rare earth magnesium alloy sheet with a total reduction of 60% and a thickness of 2 mm. The thermal conductivity was measured to be 91.2 W / (m·k). Example 4 Mg-8Gd-1Er-8Zn The steps were the same as in Example 1, except that an Mg-8Gd-1Er-8Zn alloy with 8 wt.% Zn was used. The homogenization and rolling processes were identical, resulting in a rare earth magnesium alloy sheet with a total reduction of 90% and a thickness of 2 mm. The thermal conductivity was measured to be 121.6 W / (m·k). Example 5 Mg-8Gd-1Er-8Zn-1Mn The steps were the same as in Example 4, except that a Mg-8Gd-1Er-8Zn-1Mn alloy with 1 wt.% Mn was used. The homogenization and rolling processes were identical, resulting in a rare earth magnesium alloy sheet with a total reduction of 90% and a thickness of 2 mm. The thermal conductivity was measured to be 134.6 W / (m·k). Example 6 Mg-8Gd-1Er-8Zn-2Mn The steps were the same as in Example 5, except that a Mg-8Gd-1Er-8Zn-2Mn alloy with 2 wt.% Mn was used. The homogenization and rolling processes were identical, resulting in a rare earth magnesium alloy sheet with a total reduction of 90% and a thickness of 2 mm. The thermal conductivity was measured to be 131.0 W / (m·k). Although preferred implementation cases have been listed and described in detail here, those skilled in the art will appreciate that various improvements, additions, substitutions, etc. may be made without departing from the spirit of the invention, and these contents are deemed to be within the scope of the invention as defined by the claims.

Claims

1. A wide, high thermal conductivity rare earth magnesium alloy sheet without aging, characterized in that: The alloy composition includes: 6wt% to 12wt% of Gd, 1wt% to 4wt% of Er, 2wt% to 12wt% of Zn, 0wt% to 2wt% of Mn, and the balance of Mg and inevitable impurities; Mn is preferably not 0.

2. The wide, high thermal conductivity rare earth magnesium alloy sheet material free of aging according to claim 1, characterized in that: More preferably, it is 1-2%.

3. The method for preparing a wide-width, high-thermal-conductivity rare earth magnesium alloy sheet material free of aging according to claim 1 or 2, characterized in that: The following steps are involved: 1) preparing a Mg-Gd-Er-Zn-Mn alloy ingot; using commercially pure magnesium (99.99 wt.%), pure zinc (99.99 wt.%), Mg-Gd, Mg-Er, and Mg-Mn master alloys; polishing the metal elements and the master alloy surfaces to remove any oxide scale before smelting; smelting the alloy in a mixed SF6:N2 protective atmosphere; adding 3% to 5% refining agent; and finally casting the alloy into a square ingot at a casting temperature of 700° C. to 730° C.; 2) Homogenization treatment: The cast ingot is placed in a heating furnace for homogenization treatment at 400°C for 12 hours, then quenched in room temperature water and cooled to room temperature before being processed into rolled square billets; 3) Hot rolling deformation treatment: the cast ingot after homogenization treatment is placed in a heating furnace for preheating treatment, that is, the temperature of the cast ingot is raised to a predetermined rolling temperature for rolling deformation treatment, the preheating temperature is 400°C, and the preheating time is 10 to 30 minutes; The preheated ingot is placed on a twin-roll mill for multiple hot rolling processes, with a reduction of 10-20% in each pass, a holding time of 10-20 minutes between passes, a holding temperature of 400°C, a total cumulative reduction of 90%, and finally cooled to room temperature in air to obtain a magnesium alloy rolled plate.

4. The method according to claim 3, characterized in that A large amount of broken W phase, rod-shaped W phase and α-Mn element are produced in the rolled alloy plate.

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