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

Abstract

The application provides a high-strength and high-thermal-conductivity magnesium alloy, a rolled plate and a preparation method thereof, and belongs to the technical field of magnesium alloys. 99‑ x Zn x Gd y Y 1‑y Wherein, x is 1.5-2, and y is not 0. The magnesium alloy provided by the application has high strength and high thermal conductivity, and overcomes the problem that the existing magnesium alloy cannot have high strength and high thermal conductivity simultaneously.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnesium alloy, in particular to a high-strength and high-thermal-conductivity magnesium alloy, a rolled plate and a preparation method thereof. BACKGROUND

[0002] With the development of the field of lightweight towards multi-function and high efficiency, high-integration electronic components and high-efficiency heat exchange devices have more extensive application requirements. The heat generated by these devices during operation needs to be promptly discharged, so as to ensure the stability of the device operation. The plate, as a commonly used frame structure and bearing part of these devices, puts forward higher requirements on its lightweight, high strength and high thermal conductivity.

[0003] Magnesium, as the lightest metal structural material, has high specific strength, high specific stiffness and good electrical conductivity and thermal conductivity, and is expected to realize the preparation of lightweight, high-strength and high-thermal-conductivity plate. However, the application of pure magnesium is limited due to its low strength, and the strength of the existing magnesium alloy is improved at the present stage. However, the existing magnesium alloy has the problem that the strength and thermal conductivity cannot be compatible, and the poor plasticity of the magnesium alloy limits the development of the rolling process. SUMMARY

[0004] In view of one or more technical problems in the prior art, the present application provides a high-strength and high-thermal-conductivity magnesium alloy, a rolled plate and a preparation method thereof. The magnesium alloy provided by the present application has high strength and high thermal conductivity, and overcomes the problem that the existing magnesium alloy cannot simultaneously have high strength and high thermal conductivity.

[0005] In a first aspect, the present application provides a high-strength and high-thermal-conductivity magnesium alloy, the chemical formula of the magnesium alloy is Mg 99- x Zn x Gd y Y 1-y wherein x is 1.5-2, and y is not 0.

[0006] Preferably, the magnesium alloy is obtained by melting the raw materials including pure magnesium, pure zinc, magnesium gadolinium intermediate alloy and magnesium yttrium intermediate alloy.

[0007] Preferably, the gadolinium accounts for 25-30wt% in the magnesium gadolinium intermediate alloy; and / or

[0008] The yttrium accounts for 25-30wt% in the magnesium yttrium intermediate alloy.

[0009] In a second aspect, the present application further provides a preparation method of a rolled plate, which uses the magnesium alloy of the first aspect as raw material, and the preparation method comprises:

[0010] solid solution treatment and rolling of the magnesium alloy to obtain a rolled plate;

[0011] The rolling comprises a first rolling, a second rolling and a third rolling with the reduction amount of each pass being increased in turn;

[0012] The reduction amount of each pass of the first rolling process is not more than 15%, and the total reduction amount is not less than 50%;

[0013] The reduction amount of each pass of the second rolling process is not more than 40%, and the total reduction amount is not less than 75%;

[0014] The reduction amount of each pass of the third rolling process is not more than 50%, and the total reduction amount is not less than 85%.

[0015] Preferably, the temperature of the solid solution treatment is 480-510 DEG C, and the time is 10-14h.

[0016] Preferably, the reduction amount of each pass of the first rolling process is 10-15%;

[0017] The reduction amount of each pass of the second rolling process is 20-40%; and / or

[0018] The reduction amount of each pass of the third rolling process is 40-50%.

[0019] Preferably, the temperature of the rolling is 430-460 DEG C;

[0020] The speed of the rolling is 15-25 m / min; and / or

[0021] The holding time between the rolling passes is 7-12 min.

[0022] Preferably, the method further comprises a step of performing aging treatment after the rolling.

[0023] Preferably, the temperature of the aging treatment is 160-250 DEG C;

[0024] The time of the aging treatment is 1-4h.

[0025] The application also provides a rolled plate in a third aspect, which is prepared by the method of the second aspect.

[0026] Compared with the prior art, the application has at least the following beneficial effects:

[0027] The application takes Mg-Zn alloy as the basis to ensure that the material has high thermal conductivity, and introduces rare earth elements to improve the mechanical properties of the alloy, thereby improving the strength of the magnesium alloy. Meanwhile, by controlling the content of alloying elements in the magnesium alloy, the Gd and Y elements exist in the form of precipitated phase, so that the strength of the magnesium alloy is improved while the high thermal conductivity is maintained. The magnesium alloy provided by the application has high strength and high thermal conductivity, and overcomes the problem that the existing magnesium alloy cannot have high strength and high thermal conductivity at the same time.

[0028] The present application optimizes the rolling process of the magnesium alloy based on the composition of the magnesium alloy, and performs stage-by-stage rolling: in the first stage, a small reduction per pass is used to ensure formability and refine the coarse grains in the solid solution state to a certain extent; in the second stage, the reduction per pass is increased to provide driving force for subsequent recrystallization and grain refinement, and sufficient dislocation pile-up is introduced; in the third stage, a large reduction is used to improve the strength of the material. The present application controls the microstructure morphology of the alloy by stage-by-stage rolling and adjusting the reduction per pass and the total reduction per stage in the rolling process, so as to match the strength, plasticity and thermal conductivity. The rolling process provided by the present application can realize good formability of the magnesium alloy sheet by using a general rolling mill (the roller does not have a heating function), and obtain a magnesium alloy sheet with high strength and high thermal conductivity, thereby overcoming the problem that the existing magnesium alloy is difficult to have high formability and high mechanical properties by using a general rolling mill due to its poor plasticity. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort based on these drawings.

[0030] Figure 1 is a preparation method flowchart of the magnesium alloy rolled sheet provided by the present application;

[0031] Figure 2 is Mg 97 Zn2Gd 0.5 Y 0.5 alloy as-cast SEM diagram provided by the present application;

[0032] Figure 3 is Mg 97 Zn2Gd 0.5 Y 0.5 alloy solid solution state SEM diagram provided by the present application;

[0033] Figure 4 is the actual picture of the Mg 97 Zn2Gd 0.5 Y 0.5 alloy rolled state in the embodiment 1 and the embodiment 2 of the present application (in the figure, ① corresponds to the embodiment 1, and ② corresponds to the embodiment 2);

[0034] Figure 5 is the Mg 97 Zn2Gd 0.5 Y 0.5Optical microscope (OM) photos of the aged alloy;

[0035] Figure 6 Mg 97 Zn2Gd 0.5 Y 0.5 Optical microscope (OM) photos of the aged alloy;

[0036] Figure 7 Mg 97 Zn2Gd 0.5 Y 0.5 Tensile test results of the aged alloy. DETAILED DESCRIPTION

[0037] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the technical solutions in the embodiments of the present application to make a clear and complete description. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0038] The present application provides, in a first aspect, a high-strength and high-thermal-conductivity magnesium alloy, the chemical formula of the magnesium alloy being Mg 99- x Zn x Gd y Y 1-y wherein x is 1.5-2, and y is not 0.

[0039] It should be noted that the subscript of an element in the chemical formula represents the atomic percentage of the element.

[0040] The present application takes Mg-Zn alloy as a base to ensure that the material has high thermal conductivity, and introduces rare earth elements to improve the mechanical properties of the alloy, thereby improving the strength of the magnesium alloy. Meanwhile, by controlling the content of alloying elements in the magnesium alloy, the Gd and Y elements exist in the form of precipitated phase, so that the strength of the magnesium alloy is improved while the high thermal conductivity is maintained. The magnesium alloy provided by the present application has high strength and high thermal conductivity, and overcomes the problem that the existing magnesium alloy cannot have high strength and high thermal conductivity at the same time.

[0041] Pure magnesium has high thermal conductivity (158 W / (m·K)), but the strength of pure magnesium needs to be improved by alloying. However, with the introduction of alloying elements, different degrees of lattice distortion occur in the pure magnesium matrix, which ultimately leads to different degrees of reduction in the thermal conductivity of the magnesium alloy. With the increase of the content of alloying elements, the thermal conductivity of the magnesium alloy is continuously reduced. The inventors found that different types of alloying elements also have different effects on the thermal conductivity of the magnesium alloy. When the same content of alloying elements is added, the reduction of the thermal conductivity of the magnesium alloy by Zn element is smaller, while the heavy rare earth elements (such as Gd, Y) can significantly reduce the thermal conductivity of the magnesium alloy. When the alloying elements exist in the form of solid solution, the reduction of the thermal conductivity of the magnesium alloy is significantly higher than that when the alloying elements exist in the form of precipitated phase. The prerequisite for maintaining the high thermal conductivity of the magnesium alloy is to maintain the content of the internal alloying elements at a low level, and to adjust the ratio of the alloying elements so that the alloying elements exist in the form of precipitated phase as much as possible, and the content of the solid solution atoms in the matrix is reduced. Therefore, the content of the alloying elements is controlled in the above range.

[0042] According to some preferred embodiments, the magnesium alloy is obtained by melting the raw materials including pure magnesium, pure zinc, magnesium gadolinium intermediate alloy and magnesium yttrium intermediate alloy.

[0043] According to some preferred embodiments, the melting process of the magnesium alloy includes: adding pure magnesium at 640-680℃ in a protective atmosphere, after complete melting, adding pure Zn, Mg-Gd intermediate alloy and Mg-Y intermediate alloy in sequence, after complete melting, heating to 770-790℃ and standing for 20-30min, removing the surface oxide layer to obtain a mixed melt. The mixed melt is poured into a preheated mold to obtain the magnesium alloy (as-cast alloy).

[0044] It should be noted that the oxide layer on the surface of the melt is removed before each raw material is added, and each raw material is completely melted after being added, and the elements are uniformly dispersed in the melt before the next raw material is added. The mold is heated to 250-300℃, and the mold release agent is uniformly sprayed on the inner side of the mold, and the mold is kept at 250-300℃ to obtain a preheated mold.

[0045] According to some specific embodiments, the melting process of the magnesium alloy comprises: adding pure magnesium at 660℃ in a protective atmosphere, after complete melting, adding pure Zn, Mg-30wt.%Gd and Mg-30wt.%Y in turn, before adding each raw material, the oxide layer on the surface of the melt is removed, after adding each raw material, it is ensured that the elements are uniformly dispersed in the melt, and then the next raw material can be added. After the last raw material is added, it is kept for 15min, the oxide layer on the surface of the melt is removed, and after stirring for 5-10min, it is heated to 780℃ and kept for 20-30min to obtain a mixed melt. The mixed melt is cooled by pouring cooling method, the mold is preheated to 250℃, the mold is uniformly sprayed with release agent on the inside, and the mold is kept at 300℃. After the mixed melt is kept, the surface oxide layer is removed, and the magnesium alloy (as-cast alloy) is poured into the preheated mold.

[0046] According to some preferred embodiments, the gadolinium in the magnesium-gadolinium intermediate alloy accounts for 25-30wt% (for example, it can be 25wt%, 26wt%, 27wt%, 28wt%, 29wt% or 30wt%).

[0047] According to some preferred embodiments, the yttrium in the magnesium-yttrium intermediate alloy accounts for 25-30wt% (for example, it can be 25wt%, 26wt%, 27wt%, 28wt%, 29wt% or 30wt%).

[0048] The present application also provides, in a second aspect, a preparation method of a rolled plate, which uses the magnesium alloy of the first aspect as raw material, and the preparation method comprises:

[0049] solid solution treatment and rolling of the magnesium alloy to obtain a rolled plate;

[0050] The rolling comprises a first rolling, a second rolling and a third rolling with the reduction amount of each pass increasing in turn;

[0051] The reduction amount of each pass in the first rolling process is not more than 15%, and the total reduction amount is not less than 50%;

[0052] The reduction amount of each pass in the second rolling process is not more than 40%, and the total reduction amount is not less than 75%;

[0053] The reduction amount of each pass in the third rolling process is not more than 50%, and the total reduction amount is not less than 85%.

[0054] Because the plasticity of magnesium alloy is poor, edge cracking is prone to occur during rolling, and severe edge cracking can deteriorate the mechanical properties of the alloy and even lead to failure of the plate. Therefore, the formability of the plate must be considered when the magnesium alloy rolling plate is actually prepared. In order to keep the rolling magnesium alloy plate in good mechanical properties, the rolling temperature cannot be too high, and the reduction per pass and the total reduction cannot be too low, but this will aggravate the cracking tendency of the magnesium alloy plate during rolling, and the rolling mill with heating function of the roller is often needed to realize the forming of the magnesium alloy plate, and the ordinary rolling mill is difficult to balance the high formability and high mechanical properties of the magnesium alloy plate, which greatly limits the development and application of magnesium alloy rolling.

[0055] The existing magnesium alloy rolling is usually multi-pass hot rolling, in which the rolling temperature, the reduction per pass, the total reduction and the rolling speed have a great influence on the properties of the material. The inventors found that at a relatively low temperature, or using a large reduction per pass (≥20%) can help the material to obtain higher strength, but it is prone to cause edge cracking of the material, and it is difficult to achieve a high cumulative reduction, and the plasticity of the material is greatly reduced. While increasing the temperature or using a smaller reduction per pass (≤10%) can improve the formability of the plate, but it is easy to make the final microstructure grain coarsening, and the work hardening ability is insufficient, resulting in poor mechanical properties. Although heating the roller to a certain temperature by using a warm rolling mill can improve the rolling formability of the magnesium alloy plate, the requirement for the equipment is higher. Based on this, the present application provides a rolling process for rolling magnesium alloy plate by using a conventional hot rolling method (the roller is not heated and lubricated) to ensure that the magnesium alloy has universal applicability on various rolling mills.

[0056] The present application optimizes the rolling process of magnesium alloy based on the composition of magnesium alloy, and carries out stage-by-stage rolling: in the first stage, a small reduction per pass is used to ensure the formability, and the coarse grains in the solid solution state are refined to a certain extent; in the second stage, the reduction per pass is increased to provide driving force for subsequent recrystallization and grain refinement, and sufficient dislocation pile-up is introduced; in the third stage, a large reduction per pass is used to improve the strength of the material. The present application adjusts the reduction per pass and the total reduction of each stage during rolling by stage-by-stage rolling, and controls the microstructure of the alloy, so as to match the strength, plasticity and thermal conductivity. The rolling process provided by the present application can realize good formability of the magnesium alloy plate by using an ordinary rolling mill (the roller does not have heating function), and obtain a magnesium alloy plate with high strength and high thermal conductivity, which overcomes the problem that the existing magnesium alloy is limited in rolling process due to its poor plasticity, and the ordinary rolling mill is difficult to balance the high formability and high mechanical properties of the magnesium alloy plate.

[0057] According to some preferred embodiments, the temperature of the solution treatment is 480-510℃ (for example, it can be 480℃, 490℃, 500℃ or 510℃), and the time is 10-14h (for example, it can be 10h, 11h, 12h, 13h or 14h).

[0058] According to some preferred embodiments, the reduction per pass of the first rolling process is 10-15% (for example, it can be 10%, 11%, 12%, 13%, 14% or 15%).

[0059] According to some preferred embodiments, the reduction per pass of the second rolling process is 20-40% (for example, it can be 20%, 25%, 30%, 35% or 40%).

[0060] According to some preferred embodiments, the reduction per pass of the third rolling process is 40-50% (for example, it can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50%).

[0061] According to some preferred embodiments, the temperature of the rolling is 430-460℃ (for example, it can be 430℃, 440℃, 450℃ or 460℃).

[0062] According to some preferred embodiments, the speed of the rolling is 15-25m / min (for example, it can be 15m / min, 16m / min, 17m / min, 18m / min, 19m / min, 20m / min, 21m / min, 22m / min, 23m / min, 24m / min or 25m / min).

[0063] According to some preferred embodiments, the holding time between the rolling passes is 7-12min (for example, it can be 7min, 8min, 9min, 10min, 11min or 12m / min).

[0064] According to some preferred embodiments, after the rolling, a step of performing aging treatment is further included. The present application further optimizes the comprehensive performance of the alloy through aging treatment after the completion of rolling.

[0065] According to some preferred embodiments, the temperature of the aging treatment is 160-250℃ (for example, it can be 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃ or 250℃);

[0066] The time of the aging treatment is 1-4h (for example, it can be 1h, 2h, 3h or 4h).

[0067] The present application also provides a rolled plate in a third aspect, which is prepared by the method of the second aspect.

[0068] In order to more clearly illustrate the technical solutions and advantages of the present application, the present application will be further described below in conjunction with examples. The sources of the reagents used in the examples and comparative examples of the present application are not specifically limited and can be directly purchased or synthesized by the present application.

[0069] Example 1

[0070] A high-strength and high-thermal-conductivity magnesium alloy, whose chemical formula is Mg 97 Zn2Gd 0.5 Y 0.5 The preparation method of the alloy comprises the following steps: first, heating an electric resistance furnace to 760℃, then placing a crucible and introducing a protective gas, wherein the protective gas is a mixture of CO2 and SF6, and the volume fraction of SF6 is 2.4 vol.%; when the temperature of the crucible rises to 660℃, adding pure magnesium and waiting for it to completely melt; preheating pure Zn, Mg-30wt.% Gd and Mg-30wt.% Y at 250℃; after the pure magnesium completely melts, adding the pure Zn, Mg-30wt.% Gd and Mg-30wt.% Y in sequence. Before adding each raw material, the oxide layer on the surface of the melt in the crucible is scraped off, and then the raw material is slowly put into the melt by using a clamp; after each raw material is put into the crucible, it needs to be waited for about 15 min to make it completely melt and ensure that the elements are uniformly diffused in the melt; after the diffusion of the previous raw material is completed, the next raw material can be added.

[0071] After the last raw material is added, it is kept for 15 min, then the oxide layer on the surface of the melt is removed, and stirring is performed for 5-10 min; after the stirring is completed, the electric resistance furnace is heated to 780℃ and kept for 20-30 min. The melt is cooled by pouring cooling method; the mold is preheated to 250℃, then the mold is uniformly sprayed with a release agent on the inside, and then the mold is kept at 300℃. After the melt is kept, the surface oxide layer is removed, and then the melt in the crucible is immediately poured into the preheated mold to obtain the magnesium alloy (as-cast alloy). The magnesium alloy ingot prepared is processed into a 45×30×8mm cuboid thick plate by wire cutting, and a chamfer is pre-prepared on one side of the short edge of the cuboid to facilitate subsequent rolling.

[0072] A preparation method of a rolled plate, comprising:

[0073] First, the Mg 97 Zn2Gd 0.5 Y 0.5 alloy is subjected to solid solution treatment, wherein the temperature of the solid solution treatment is 500℃ and the time is 12h; then the Mg 97 Zn2Gd 0.5 Y0.5 The alloy is rolled, and the rolling process comprises: firstly, 6 passes of small reduction are carried out, and the reduction of each pass is 10%, and at this time the total reduction reaches 50%; then, 1 pass of 20% reduction is carried out; subsequently, 1 pass of 37.5% reduction is carried out, and at this time the total reduction reaches 75%. Finally, the last pass of 50% reduction is carried out, and at this time the total reduction of the plate reaches 87.5%, and the temperature of the whole rolling process is 450 ℃, the rolling speed is 20 m / min, and the temperature is kept for 10 min between passes. After the rolling is completed, the rolled plate is subjected to aging treatment, wherein the temperature of the aging treatment is 200 ℃, and the time is 2 h, and the rolled plate is obtained.

[0074] In this embodiment, Mg 97 Zn2Gd 0.5 Y 0.5 The main precipitated phase in the as-cast alloy is a network-shaped W phase (Mg3Zn3RE2), as shown in FIG. 1. Figure 2 After solid solution treatment, the network-shaped W phase is converted into a spherical W phase, as shown in FIG. 2. Figure 3 The network-shaped eutectic phase is easy to cause the initiation and propagation of cracks during the deformation of the magnesium alloy, and the solid solution treatment can homogenize the composition of the material and avoid the adverse effects of the network-shaped W phase, thereby improving the subsequent rolling formability and the final comprehensive mechanical properties of the material.

[0075] Example 2

[0076] The embodiment 1 is basically the same, and the only difference is that:

[0077] A method for preparing a rolled plate comprises the following steps:

[0078] Firstly, the Mg 97 Zn2Gd 0.5 Y 0.5 The alloy is subjected to solid solution treatment, wherein the temperature of the solid solution treatment is 500 ℃, and the time is 12 h; then, the Mg 97 Zn2Gd 0.5 Y 0.5 The alloy is rolled, and the rolling process comprises: firstly, 6 passes of small reduction are carried out, and the reduction of each pass is 10%, and at this time the total reduction reaches 50%; then, 3 passes of 20% reduction are carried out, and at this time the total reduction reaches 75%; finally, the last pass of 50% reduction is carried out, and at this time the total reduction of the plate reaches 87.5%, and the temperature of the whole rolling process is 450 ℃, the rolling speed is 20 m / min, and the temperature is kept for 10 min between passes. After the rolling is completed, the rolled plate is subjected to aging treatment, wherein the temperature of the aging treatment is 200 ℃, and the time is 2 h, and the rolled plate is obtained.

[0079] The thickness changes during the rolling process in Examples 1 and 2 of this invention are shown in Table 1.

[0080] Table 1. Thickness variation during rolling process in Examples 1 and 2 of the present invention

[0081]

[0082] The rolled sheets obtained in Examples 1 and 2 exhibited excellent formability, with almost no edge cracking. Figure 4 Examples 1 and 2, after rolling, underwent aging treatment to obtain the final microstructure, as shown below. Figures 5-6 (In the figure, RD is the rolling direction, ND is the normal direction, and TD is the transverse direction.) The microstructure of the rolled plates prepared in the two embodiments is quite similar, exhibiting a typical bimodal microstructure, consisting of large deformed grains and fine recrystallized grains, and the spheroidized W phase is distributed along the RD direction (rolling direction).

[0083] Depend on Figure 7 It can be seen that the Mg prepared in Examples 1 and 2 97 Zn2Gd 0.5 Y 0.5 The tensile stress-strain curves of the alloy rolled plates at room temperature show that the materials prepared in Examples 1 and 2 both exhibit good comprehensive mechanical properties, with a yield strength >250 MPa and an elongation at break >15%. The mechanical properties of the materials are closely related to their microstructure. A bimodal microstructure provides better mechanical properties; dislocation pile-up within large deformation grains can hinder dislocation slip and improve material strength, while fine recrystallized grains can coordinate deformation and improve the material's plasticity. According to Hall-Patch law, small-sized recrystallized grains can also contribute to material strength through grain boundary strengthening. Furthermore, the spheroidized W phase can also hinder dislocation slip to a certain extent, acting as a second-phase strengthening agent. Therefore, the Mg prepared in Examples 1 and 2 of this invention... 97 Zn2Gd 0.5 Y 0.5 Alloy rolled sheets have good strength and plasticity.

[0084] Example 3

[0085] It is basically the same as Example 1, except that no aging treatment is performed after rolling.

[0086] Comparative Example 1

[0087] This is essentially the same as Example 3, except that the chemical formula of the high-strength, high-thermal-conductivity magnesium alloy is Mg. 98 Zn1Gd 0.5 Y 0.5 .

[0088] Comparative Example 2

[0089] The difference between Example 3 and Comparative Example 3 is that the high-strength and high-thermal-conductivity magnesium alloy has a chemical formula of Mg 98.33 Zn 0.67 Gd 0.5 Y 0.5 .

[0090] The actual chemical compositions of the magnesium alloys (as-cast alloys) involved in the examples and comparative examples of the present application are shown in Table 2.

[0091] Table 2. Actual chemical compositions of the magnesium alloys (as-cast alloys) involved in the examples and comparative examples of the present application

[0092]

[0093]

[0094] It should be noted that RE in the specification of the present application is a rare earth metal, and RE / Zn represents the atomic number ratio of the rare earth metal to zinc.

[0095] Comparative Example 3

[0096] The difference between Example 1 and Comparative Example 3 is that the rolling process includes: the reduction amount of each pass in the rolling process is 10%, and a total of 14 passes are performed to roll the initial 8 mm thick plate into a 1.6 mm thick sheet, at which time the total reduction amount is 80%. The rolling temperature of the entire rolling process is 450°C, the rolling speed is 20 m / min, and the inter-pass holding time is 10 min.

[0097] Comparative Example 4

[0098] The difference between Example 1 and Comparative Example 4 is that the rolling process includes: the reduction amount of each pass in the rolling process is 20%, and the rolling temperature of the entire rolling process is 450°C, the rolling speed is 20 m / min, and the inter-pass holding time is 10 min.

[0099] The inventors found that after 4 passes of rolling, the plate had a serious edge crack, and after 5 passes of rolling, the crack rapidly expanded to the inside, and the plate was difficult to meet the formability requirements.

[0100] Comparative Example 5

[0101] The difference between Example 1 and Comparative Example 5 is that the rolling process includes: first, 10% reduction amount of each pass is rolled, and after 3 passes of rolling, the total reduction amount of the plate reaches 30%, and then 20% reduction amount of each pass is rolled, and after 3 passes of rolling, the total reduction amount of the plate reaches 70%. The rolling temperature of the entire rolling process is 450°C, the rolling speed is 20 m / min, and the inter-pass holding time is 10 min.

[0102] The inventors found that the plate had good formability after 3 passes of 10% reduction, but serious edge cracking occurred after 3 passes of 20% reduction, and the cracks extended to the inside.

[0103] Comparative Example 6

[0104] The process was basically the same as in Example 1, except that the rolling process included first performing rolling with 10% reduction per pass, and after 6 passes, the total reduction of the plate reached 50%; then performing rolling with 50% reduction in the final pass, and at this time the total reduction of the plate reached 75%. The temperature of the rolling in the whole rolling process was 450°C, the rolling speed was 20 m / min, and the holding time between passes was 10 min.

[0105] The inventors found that the plate had good formability after 6 passes of 10% reduction, but serious fragmentation occurred after the final pass of 50% reduction.

[0106] Comparative Example 7

[0107] The process was basically the same as in Example 1, except that first performing rolling with 10% reduction per pass, and after 6 passes, the total reduction of the plate reached 50%; then performing rolling with 20% reduction in one pass, and at this time the total reduction of the plate reached 60%; finally performing rolling with 50% reduction in the final pass, and at this time the total reduction of the plate reached 80%. The temperature of the rolling in the whole rolling process was 450°C, the rolling speed was 20 m / min, and the holding time between passes was 10 min.

[0108] The inventors found that serious fragmentation occurred after the final pass of 50% reduction.

[0109] Comparative Example 8

[0110] The process was basically the same as in Example 1, except that the rolling process included first performing rolling with 10% reduction per pass, and after 10 passes, the total reduction of the plate reached 70%; then performing rolling with 50% reduction in the final pass, and at this time the total reduction of the plate reached 85%. The temperature of the rolling in the whole rolling process was 450°C, the rolling speed was 20 m / min, and the holding time between passes was 10 min.

[0111] The inventors found that the plate had good formability, but poor mechanical properties, and the elongation was extremely low.

[0112] The test results of the properties of the magnesium alloy rolled plates of the examples and comparative examples of the present application are shown in Table 3.

[0113] Table 3. Mechanical and thermal conductivity properties of the magnesium alloy rolled plates prepared in the examples and comparative examples of the present application

[0114]

[0115] It should be noted that Comparative Examples 4-7 cannot meet the use requirements due to poor formability and failure of the plate, and thus no relevant performance test is performed. In Comparative Example 8, "-" indicates that no relevant test is performed.

[0116] As can be seen from Table 3, the material prepared in Example 1-3 has good thermal conductivity while considering strength and plasticity, and meets the performance requirements of high-thermal-conductivity magnesium alloy. The thermal conductivity of Example 1 and Example 2 at room temperature is greater than 120 W / (m·K), indicating that the aging treatment can promote the generation of precipitated phase in the alloy or reduce the dislocation density to improve the thermal conductivity of the deformed magnesium alloy, and further improve the thermal conductivity of the material.

[0117] As can be seen from the thermal conductivity of the magnesium alloy plate prepared in Example 1, Comparative Example 1 and Comparative Example 2, with the increase of the RE / Zn ratio, the main alloying element in the magnesium changes from Zn element to RE element, and the thermal conductivity of the alloy shows a significant downward trend. The reason is that the reduction of the thermal conductivity of Zn with the same content is significantly lower than that of RE element with the same content, and on the other hand, the reduction of Zn content significantly reduces the content of precipitated phase that can be formed in the alloy, and the content of RE element in the form of solid solution atoms is increased. The Mg 97 Zn2Gd 0.5 Y 0.5 The atomic ratio of RE / Zn in the alloy is 2.0, which can form a large amount of W phase (Mg3Zn3RE2) in the alloy. The precipitated phase can reduce the content of Zn and RE dissolved in the matrix, which is beneficial to the thermal conductivity of the alloy, and can also provide strengthening effect in the mechanical properties.

[0118] In summary, the present application is based on Mg-Zn alloy to ensure that the material has high thermal conductivity, and by introducing rare earth elements to improve the mechanical properties of the alloy, and then improve the strength of the magnesium alloy. At the same time, by controlling the content of alloying elements in the magnesium alloy, the Gd and Y elements exist in the form of precipitated phase, ensuring that the strength of the magnesium alloy is improved while maintaining high thermal conductivity. The present application optimizes the rolling process of the magnesium alloy based on the composition of the magnesium alloy, controls the microstructure of the alloy by adjusting the down pressure and total down pressure of each stage and each pass in the rolling process in stages, and realizes the matching of strength, plasticity and thermal conductivity. The rolling process provided by the present application can realize good formability of magnesium alloy plate by using ordinary rolling mill (the roller does not have heating function), and obtain high-strength and high-thermal-conductivity magnesium alloy plate, which overcomes the problem that the existing magnesium alloy is difficult to consider high formability and high mechanical properties of magnesium alloy plate by using ordinary rolling mill due to its poor plasticity.

[0119] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for producing a rolled plate, characterized by, The high-strength high-thermal-conductivity magnesium alloy has a chemical formula of Mg 99-x Zn x Gd y Y 1-y wherein x is 1.5-2, and y is not 0. The preparation method comprises: The high-strength and high-thermal-conductivity magnesium alloy is subjected to solid solution treatment and rolling to obtain a rolled plate; The rolling comprises first rolling, second rolling and third rolling with the reduction amount of each pass increasing in turn; The reduction amount of each pass in the first rolling process is not greater than 15%, and the total reduction amount is not less than 50%; The reduction amount of each pass in the second rolling process is not greater than 40%, and the total reduction amount is not less than 75%; The reduction amount of each pass in the third rolling process is not greater than 50%, and the total reduction amount is not less than 85%.

2. The production method according to claim 1, characterized by, The high-strength and high-thermal-conductivity magnesium alloy is obtained by melting raw materials comprising pure magnesium, pure zinc, magnesium gadolinium intermediate alloy and magnesium yttrium intermediate alloy.

3. The method of claim 2, wherein, The gadolinium accounts for 25-30wt% in the magnesium gadolinium intermediate alloy; and / or The yttrium accounts for 25-30wt% in the magnesium yttrium intermediate alloy.

4. The method of claim 1, wherein, The temperature of the solid solution treatment is 480-510℃, and the time is 10-14h.

5. The preparation method according to claim 1, characterized in that, The reduction amount of each pass in the first rolling process is 10-15%; The reduction amount of each pass in the second rolling process is 20-40%; and / or The reduction amount of each pass in the third rolling process is 40-50%.

6. The method of claim 1, wherein, The temperature of the rolling is 430-460℃; The speed of the rolling is 15-25m / min; and / or The holding time between passes of the rolling is 7-12min.

7. The preparation method according to claim 1, characterized in that, The method further comprises a step of performing aging treatment after the rolling.

8. The production method according to claim 7, characterized by, The temperature of the aging treatment is 160-250℃; and / or The time of the aging treatment is 1-4h.

9. A rolled plate characterized by, The high-strength and high-thermal-conductivity magnesium alloy is prepared by the preparation method of any one of claims 1-8.

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