Magnesium alloy with low cost, ultrahigh thermal conductivity and high thermal formability and preparation method of magnesium alloy plate

Abstract

The invention discloses a low-cost ultrahigh-heat-conduction high-thermal-formability magnesium alloy and a preparation method of a plate thereof, and relates to a magnesium alloy and a preparation method of a plate thereof. The problems that an existing magnesium alloy is low in heat conductivity and difficult in formability are solved. According to the invention, favorable alloying elements with high thermal conductivity and high formability are preferably selected, and the ultra-high thermal conductivity and high formability rolled magnesium alloy of which the thermal conductivity breaks through the limit of the thermal conductivity of pure magnesium is realized through the processes of smelting, homogenizing heat treatment and rolling deformation; the alloy has good high-temperature formability, the machining forming capacity is improved, the heat conduction limit of the magnesium alloy is broken through, and the method is suitable for preparing high-heat-conduction and high-formability plates. The room-temperature thermal conductivity of the prepared rolled magnesium alloy plate reaches 173.1 W / (m.K), the limit of the thermal conductivity of pure magnesium is broken through, the rolled magnesium alloy plate has excellent thermal conductivity and good high-temperature formability, and technical guidance is provided for development of magnesium alloy plates with ultrahigh thermal conductivity and high formability.

Description

Technical Field

[0001] The present invention relates to a magnesium alloy and a preparation method thereof for sheets. Background Art

[0002] Magnesium alloy is the lightest metal structural material, with high specific strength and specific stiffness, and has good electromagnetic shielding performance, damping performance and machining performance. It is currently the most potential lightweight metal structural material in the fields of aerospace, transportation, 3C products, etc. With the continuous development of high-precision and sophisticated major equipment, the electronic component group is gradually becoming high-power and complex, and the problem of frequent failures caused by overheating of electronic devices is frequent, which puts forward higher requirements for the thermal conductivity of structural materials. Therefore, magnesium alloys with high thermal conductivity have great application potential.

[0003] In the field of high-end aerospace equipment (such as precision structural parts such as satellite radar antenna backplates), it is urgent to develop magnesium alloy sheets with both high thermal conductivity and high formability. Although pure magnesium has an excellent intrinsic thermal conductivity of 157 W / (m·K), its close-packed hexagonal (HCP) crystal structure results in insufficient activation of slip systems, significant work hardening effect and serious strong texture tendency, and its mechanical properties and formability are difficult to meet engineering requirements. Among current commercial magnesium alloys, the room-temperature thermal conductivity of AZ91 rolled sheets is 61 W / (m·K), and that of WE43 rolled sheets is only 51 W / (m·K), indicating that there are obvious limitations in the traditional alloy system for the synergistic improvement of thermal conductivity and formability.

[0004] Although alloying can improve mechanical properties through solid solution strengthening (lattice distortion caused by solute atoms) and second-phase strengthening, according to the research on the thermal conduction mechanism, the introduction of solute atoms will enhance electron / phonon scattering, reduce the mean free path of carriers, and cause the thermal conductivity to decay significantly with the increase of alloying element content (the influence differences of different elements are closely related to their atomic volume difference, valence state, electronic structure and solid solubility). The thermal conductivity of existing magnesium alloy materials is lower than the pure magnesium reference value, and breaking through the thermal conductivity limit of pure magnesium is still a technical bottleneck in the industry. Therefore, the contradiction between the strengthening mechanism and thermal conductivity attenuation of alloying elements essentially stems from the multi-scale scattering effect of defects such as solute atoms, grain boundaries and dislocations on the thermal conduction path.

[0005] Therefore, it is of great significance to select alloying elements and their contents preferably, regulate the element distribution and phase distribution through composition design and heat treatment, and regulate the microstructure, mechanical properties and thermal conductivity of the alloy through rolling deformation in order to achieve their synergistic improvement, and prepare low-cost ultra-high thermal conductivity and high formability rolled magnesium alloy sheets for aerospace, transportation and military defense. Summary of the Invention

[0006] Aiming at the problems of low thermal conductivity and difficult formability of existing magnesium alloys, the present invention proposes a preparation method for a low-cost ultra-high thermal conductivity and high formability magnesium alloy and its sheets.

[0007] The low-cost, ultra-high thermal conductivity and high hot formability magnesium alloy of the present invention is an Mg-X alloy, where the X element is lanthanum, cerium, neodymium or praseodymium. The content of the X element in the Mg-X alloy is 0.1-2.0 wt.%, and the balance is Mg. The X element has a relatively low solid solubility and there is a phenomenon of weakening the basal texture by the rare earth texture, which can reduce the influence of solute atoms on the thermal conductivity and improve the formability of the sheet. Through the combination of adding relatively trace alloying elements, heat treatment and hot rolling technology, a binary magnesium alloy with ultra-high thermal conductivity and high formability is prepared.

[0008] The preparation method of the above-mentioned low-cost, ultra-high thermal conductivity and high hot formability magnesium alloy sheet is carried out according to the following steps:

[0009] I. Weigh the raw materials according to the mass content of the elements of the Mg-X alloy and clean them;

[0010] The raw materials are industrial pure magnesium ingots and Mg-X master alloys;

[0011] II. Preheat the raw materials treated in step I, then melt them in a protective atmosphere, cool to obtain alloy ingots; remove the oxide layer on the surface of the alloy ingots, and finally carry out homogenization heat treatment;

[0012] The temperature of the homogenization heat treatment is 450-520 °C, and the holding time is 2-12 hours;

[0013] The melting process is as follows: heat the industrial pure magnesium ingots to 680-760 °C to melt, then add the Mg-X master alloy until completely melted, stir for 30 minutes after holding, cool the melt to 680-705 °C after stirring ends, stand for 10-20 minutes, and finally prepare alloy ingots by water cooling process in a protective atmosphere; the stirring time is 2-6 min;

[0014] III. Prepare the alloy ingots obtained in step II into blanks, preheat the blanks, then carry out rolling deformation on the blanks, and finally carry out air cooling treatment to complete;

[0015] The process of the rolling deformation is as follows: the hot rolling temperature is 350-450 °C, carry out multi-pass hot rolling, the deformation amount of the first pass is 20%, the deformation amount of the subsequent passes gradually increases, the increment is 10%, and the cumulative deformation amount is 60-97%; the rolling rate is 0.5-5.5 m / s; during the multi-pass hot rolling process, annealing is carried out between adjacent passes, and the annealing temperature is the same as the preheating temperature of the blank;

[0016] The annealing time between adjacent passes during the multi-pass hot rolling process is as follows: when the thickness exceeds 4 mm, anneal for 15 minutes, when the thickness is 2-4 mm, anneal for 10 minutes, and when the thickness is less than 2 mm, anneal for 5 minutes.

[0017] The principle and beneficial effects of the present invention are as follows:

[0018] The present invention preferably selects alloying elements with high thermal conductivity and high formability, and through smelting, homogenization heat treatment and rolling deformation processes, an ultra-high thermal conductivity and high formability rolled magnesium alloy is achieved, whose thermal conductivity breaks through the thermal conductivity limit of pure magnesium; among them, element X is La, Ce, Pr, and Nd. La, Ce, Pr, and Nd have similarities, which stem from the consistency of the outer electron structure (5d16s 2 ) and the gradually filled 4f orbitals. Although the number of 4f electrons is different, the 4f orbitals are shielded by inner electrons. Therefore, La, Ce, Pr, and Nd have highly similar chemical properties; La, Ce, Pr, and Nd cause slight expansion or stress of the local lattice, forming a unique lattice arrangement, which may form special channels to promote phonon propagation and thus increase the thermal conductivity. On the other hand, the formation of Mg-X intermetallic compounds is dynamically precipitated after hot rolling deformation, reducing the content of solute atoms in the magnesium lattice and increasing the thermal conductivity of the alloy. In addition, La, Ce, Pr, and Nd elements can introduce solid solution strengthening and second-phase strengthening to improve the mechanical properties of the alloy, and the unique nuclear outer electron structure can reduce the basal texture of the alloy sheet to form a "rare earth texture". The present invention provides a preparation technology for high thermal conductivity and high formability magnesium alloy sheets by designing alloying elements, preferably selecting alloying elements with high thermal conductivity, having a low lattice distortion rate, and using heat treatment to control the phase morphology and distribution before rolling, breaking the eutectic phase through multi-pass hot rolling deformation to make it disperse, promoting the dynamic precipitation of nano-precipitated phases, reducing the content of solute atoms, weakening the basal texture. Therefore, the alloy has good hot formability, improves the processing and forming ability, and breaks through the thermal conductivity limit of magnesium alloys, and is suitable for the preparation of high thermal conductivity and high formability sheets.

[0019] 2. The room temperature thermal conductivity of the rolled magnesium alloy sheet prepared by the present invention reaches 173.1 W / (m·K), breaking through the thermal conductivity limit of pure magnesium. It has excellent thermal conductivity and good hot formability at the same time. The properties of the obtained sheet can meet the forming and processing performance and thermal conductivity requirements of structural parts in fields such as aerospace, deep space exploration, military defense, transportation, and 3C products, and has broad application prospects. The present invention can achieve large-scale production and provides technical guidance for the development of ultra-high thermal conductivity and high formability magnesium alloy sheets.

[0020] 3. The present invention undergoes homogenization heat treatment at 450 - 520 °C and hot rolling at 350 - 450 °C. By controlling the temperature and deformation process, it affects the recrystallization behavior of the alloy, forming a grain structure with coexisting deformed grains and recrystallized grains, and there are a high density of low-angle grain boundaries inside. The low-angle grain boundaries can reduce the interfacial thermal resistance and promote the improvement of thermal conductivity. Multi-pass hot rolling is adopted to improve the formability of the sheet. The hot rolling partially breaks the magnesium-rare earth intermetallic compound phase, provides energy to promote dynamic precipitation, and constructs a multi-scale phase structure with refined and dispersed broken eutectic phases and a large number of precipitated and dispersed nano-precipitation phases, promoting the reduction of X solute atoms, improving the lattice structure and phase interface, and breaking through the thermal conductivity limit of pure magnesium. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Microstructure diagram of the as-rolled Mg-X alloy prepared in Example 1;

[0022] Figure 2 SEM diagram of the as-rolled structure of the Mg-X alloy prepared in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0023] The technical solution of the present invention is not limited to the following specific embodiments listed, but also includes any reasonable combination between the specific embodiments.

[0024] Specific Embodiment 1: The low-cost, ultra-high thermal conductivity and high formability magnesium alloy in this embodiment is the Mg-X alloy, where the X element is lanthanum, cerium, neodymium or praseodymium, and the content of the X element in the Mg-X alloy is 0.1 - 2.0 wt.%, with Mg as the balance. The X element has a low solid solubility and there is a phenomenon of weakening the basal texture by the rare earth texture, which can reduce the influence of solute atoms on the thermal conductivity and improve the formability of the sheet. Through the combination of adding relatively trace alloying elements, heat treatment and hot rolling technology, a binary magnesium alloy with ultra-high thermal conductivity and high formability is prepared.

[0025] This embodiment has the following beneficial effects:

[0026] This embodiment preferably selects alloying elements beneficial to high thermal conductivity and high formability, and through melting, homogenization heat treatment and rolling deformation processes, an ultra-high thermal conductivity and high formability rolled magnesium alloy with a thermal conductivity breaking through the thermal conductivity limit of pure magnesium is realized; among them, the X element is La, Ce, Pr and Nd, and La, Ce, Pr and Nd have similarities, originating from the outer electron structure (5d16s 2) Consistency and gradually filled 4f orbitals. Although the number of 4f electrons is different, the 4f orbitals are shielded by inner-layer electrons, resulting in highly similar chemical properties of La, Ce, Pr, and Nd. La, Ce, Pr, and Nd cause slight expansion or stress of the local lattice, forming a unique lattice arrangement, which may form special channels to promote phonon propagation and thus increase the thermal conductivity. On the other hand, the dynamically precipitated Mg-X intermetallic compound after hot rolling deformation reduces the solute atom content in the magnesium lattice and increases the thermal conductivity of the alloy. In addition, elements such as La, Ce, Pr, and Nd can introduce solid-solution strengthening and second-phase strengthening to improve the mechanical properties of the alloy. The unique outermost electron structure can reduce the basal texture of the alloy sheet and form a "rare-earth texture". This embodiment designs alloying elements, preferably high-thermal-conductivity alloying elements with a low lattice distortion rate, and uses heat treatment to control the phase morphology and distribution before rolling. The eutectic phase is broken by multi-pass hot rolling deformation to make it disperse, promoting the dynamic precipitation of nano-precipitated phases, reducing the solute atom content, weakening the basal texture, and forming a preparation technology for high-thermal-conductivity and high-formability magnesium alloy sheets. Therefore, the alloy has good high-temperature formability, improves the processing and forming ability, and breaks through the thermal conductivity limit of magnesium alloys, being suitable for the preparation of high-thermal-conductivity and high-formability sheets.

[0027] 2. The room-temperature thermal conductivity of the rolled magnesium alloy sheet prepared by this embodiment reaches 173.1 W / (m·K), breaking through the thermal conductivity limit of pure magnesium. It has excellent thermal conductivity and good high-temperature formability at the same time. The properties of the obtained sheet can meet the forming and processing performance and thermal conductivity requirements of structural parts in fields such as aerospace, deep space exploration, military defense, transportation, and 3C products, and have broad application prospects. This embodiment can achieve large-scale production and provides technical guidance for the development of ultra-high-thermal-conductivity and high-formability magnesium alloy sheets.

[0028] 3. This embodiment affects the recrystallization behavior of the alloy through homogenization heat treatment at 450 - 520 °C and hot rolling at 350 - 450 °C by controlling the temperature and deformation process, forming a grain structure with coexisting deformed grains and recrystallized grains, and having a high density of small-angle grain boundaries inside. The small-angle grain boundaries can reduce the interface thermal resistance and promote the increase of thermal conductivity. Multi-pass hot rolling is used to improve the formability of the sheet. The hot rolling partially breaks the magnesium-rare-earth intermetallic compound phase, provides energy to promote dynamic precipitation, and constructs a multi-scale phase structure with refined and dispersed broken eutectic phases and a large number of precipitated and dispersed nano-precipitated phases, promoting the reduction of X solute atoms, improving the lattice structure and phase interface, and breaking through the thermal conductivity limit of pure magnesium.

[0029] Specific Embodiment 2: The preparation method of the low-cost ultra-high-thermal-conductivity and high-thermal-formability magnesium alloy sheet is carried out according to the following steps:

[0030] 1. Weigh the raw materials according to the mass content of the elements in the Mg-X alloy and clean them;

[0031] The raw materials are industrial pure magnesium ingots and Mg-X master alloys;

[0032] 2. Preheat the raw materials processed in step 1, then melt them in a protective atmosphere, and cool to obtain alloy ingots; remove the oxide layer on the surface of the alloy ingots, and finally perform homogenization heat treatment;

[0033] The temperature of the homogenization heat treatment is 450 - 520 °C, and the holding time is 2 - 12 hours;

[0034] The melting process is as follows: Heat the industrial pure magnesium ingots to 680 - 760 °C until molten, then add the Mg-X master alloy until completely melted, stir for 30 minutes after holding, cool the melt to 680 - 705 °C after stirring ends, stand for 10 - 20 minutes, and finally prepare alloy ingots through water cooling process in a protective atmosphere; the stirring time is 2 - 6 min;

[0035] 3. Prepare the alloy ingots obtained in step 2 into billets, preheat the billets, then perform rolling deformation on the billets, and finally perform air cooling treatment, thus completing;

[0036] The rolling deformation process is as follows: The hot rolling temperature is 350 - 450 °C, multi-pass hot rolling is performed, the deformation amount of the first pass is 20%, the deformation amount of the subsequent passes gradually increases, the increment is 10%, and the cumulative deformation amount is 60 - 97%; the rolling speed is 0.5 - 5.5 m / s; annealing is performed between adjacent passes during multi-pass hot rolling, and the annealing temperature is the same as the preheating temperature of the billets;

[0037] The annealing time between adjacent passes during multi-pass hot rolling is as follows: When the thickness exceeds 4 mm, anneal for 15 minutes; when the thickness is 2 - 4 mm, anneal for 10 minutes; when the thickness is less than 2 mm, anneal for 5 minutes.

[0038] This embodiment preferably selects alloying elements that are beneficial for high thermal conductivity and high formability, and realizes a super-high thermal conductivity and high formability rolled magnesium alloy with a thermal conductivity breaking through the thermal conductivity limit of pure magnesium through melting, homogenization heat treatment and rolling deformation processes; among them, the X element is La, Ce, Pr, and Nd, and La, Ce, Pr, and Nd have similarities, originating from the outer electron structure (5d16s 2) Consistency and gradually filled 4f orbitals. Although the number of 4f electrons is different, the 4f orbitals are shielded by inner-layer electrons, resulting in highly similar chemical properties of La, Ce, Pr, and Nd. La, Ce, Pr, and Nd cause slight expansion or stress of the local lattice, forming a unique lattice arrangement, which may form special channels to promote phonon propagation and thus increase the thermal conductivity. On the other hand, the dynamically precipitated Mg-X intermetallic compound after hot rolling deformation reduces the solute atom content in the magnesium lattice and increases the thermal conductivity of the alloy. In addition, elements such as La, Ce, Pr, and Nd can introduce solid-solution strengthening and second-phase strengthening to improve the mechanical properties of the alloy. The unique nuclear outer electron structure can reduce the basal texture of the alloy sheet and form a "rare-earth texture". This embodiment designs alloy elements, preferably high-thermal-conductivity alloying elements with a low lattice distortion rate, and uses heat treatment to control the phase morphology and distribution before rolling. Through multi-pass hot rolling deformation, the eutectic phase is broken and dispersed, promoting the dynamic precipitation of nano-precipitation phases, reducing the solute atom content, weakening the basal texture, and forming a preparation technology for high-thermal-conductivity and high-formability magnesium alloy sheets. Therefore, the alloy has good high-temperature formability, improves the processing and forming ability, and breaks through the thermal conductivity limit of magnesium alloys, being suitable for the preparation of high-thermal-conductivity and high-formability sheets.

[0039] 2. The room-temperature thermal conductivity of the rolled magnesium alloy sheet prepared by this embodiment reaches 173.1 W / (m·K), breaking through the thermal conductivity limit of pure magnesium. It has excellent thermal conductivity and good high-temperature formability at the same time. The properties of the obtained sheet can meet the forming and processing performance and thermal conductivity requirements of structural parts in fields such as aerospace, deep space exploration, military defense, transportation, and 3C products, and have broad application prospects. This embodiment can achieve large-scale production and provides technical guidance for the development of ultra-high-thermal-conductivity and high-formability magnesium alloy sheets.

[0040] 3. This embodiment undergoes homogenization heat treatment at 450 - 520 °C and hot rolling at 350 - 450 °C. By controlling the temperature and deformation process, it affects the recrystallization behavior of the alloy, forming a grain structure with coexisting deformed grains and recrystallized grains, and there are a high density of small-angle grain boundaries inside. The small-angle grain boundaries can reduce the interface thermal resistance and promote the increase of thermal conductivity. Multi-pass hot rolling is used to improve the formability of the sheet. The hot rolling partially breaks the magnesium-rare-earth intermetallic compound phase, provides energy to promote dynamic precipitation, and constructs a multi-scale phase structure with refined and dispersed broken eutectic phases and a large amount of precipitated and dispersed nano-precipitation phases, promoting the reduction of X solute atoms, improving the lattice structure and phase interface, and breaking through the thermal conductivity limit of pure magnesium.

[0041] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that the cleaning process in Step 1 is as follows: Use sandpaper to grind and remove the pollutants on the surface of the raw material, then use sandpaper to polish and remove the impurities and scale on the surface of the raw material, and finally perform ultrasonic cleaning with anhydrous ethanol.

[0042] Specific Embodiment 4: The difference between this embodiment and any one of Specific Embodiments 1 to 3 is that the preheating temperature of the raw material in Step 2 is 290 - 470 °C.

[0043] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that the protective atmosphere in Step 2 consists of CO 2 and SF 6 The mixed gas is composed of, and the volume percentage of SF 6 in the mixed gas is 1.0 - 4.0%.

[0044] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is that the thickness of the blank in Step 3 is 10 - 30 mm.

[0045] Specific Embodiment 7: The difference between this embodiment and any one of Specific Embodiments 1 to 6 is that the rolling rate in Step 3 is 2 m / s; during multi-pass hot rolling, annealing is performed between adjacent passes, and the annealing temperature is the same as the preheating temperature of the blank.

[0046] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 7 is that the preheating temperature of the blank in Step 3 is 290 - 470 °C, and the preheating time is 10 - 35 min.

[0047] Specific Embodiment 9: The difference between this embodiment and any one of Specific Embodiments 1 to 8 is that the rolling deformation process in Step 3 is as follows: The hot rolling temperature is 400 °C, multi-pass hot rolling is performed, the deformation amount of the first pass is 20%, the deformation amount of the subsequent passes gradually increases, the increment is 10%, and the cumulative deformation amount is 80%.

[0048] Specific Embodiment 10: The difference between this embodiment and any one of Specific Embodiments 1 to 9 is that the melting process in Step 2 is as follows: Heat the industrial pure magnesium ingot to 760 °C until it melts, then add the Mg-X master alloy until it completely melts, keep it warm for 30 minutes and then stir for 5 minutes. After the stirring ends, cool the melt to 690, let it stand for 15 minutes, and finally prepare the alloy ingot through water cooling process in a protective atmosphere.

[0049] Example 1

[0050] The low-cost ultra-high thermal conductivity and high hot formability magnesium alloy in this example is a Mg-Ce alloy, the Ce element content is 0.52 wt.%, and Mg is the balance;

[0051] The preparation method of the above-mentioned low-cost magnesium alloy sheet with ultra-high thermal conductivity and high hot formability is carried out according to the following steps:

[0052] I. Weigh the raw materials according to the mass content of the elements of the Mg-Ce alloy and clean them;

[0053] The raw materials are industrial pure magnesium ingots and Mg-30wt.% Ce master alloy;

[0054] The cleaning process is as follows: Use sandpaper to grind and remove the pollutants on the surface of the raw materials, then use sandpaper to polish and remove the surface impurities and oxide scales of the raw materials, and finally use anhydrous ethanol for ultrasonic cleaning;

[0055] II. Preheat the raw materials processed in step I, then melt them in a protective atmosphere, cool to obtain alloy ingots; Remove the oxide layer on the surface of the alloy ingots, and finally carry out homogenization heat treatment;

[0056] The temperature for preheating the raw materials is 410 °C;

[0057] The temperature for the homogenization heat treatment is 500 °C, and the holding time is 6 hours;

[0058] The protective atmosphere consists of CO 2 and SF 6 The mixed gas, and the volume percentage of SF 6 in the mixed gas is 2.6%;

[0059] The melting process is as follows: Heat the industrial pure magnesium ingots to 760 °C and melt them, then add Mg-X master alloy until completely melted, stir for 5 min after holding for 30 minutes, cool the melt to 690 °C after stirring, stand for 15 minutes, and finally prepare alloy ingots through water cooling process in a protective atmosphere;

[0060] III. Prepare the alloy ingots obtained in step II into 10-mm blanks, preheat the blanks, then carry out rolling deformation on the blanks, and finally carry out air cooling treatment, then it is completed;

[0061] The process of the rolling deformation is as follows: The hot rolling temperature is 400 °C, carry out multi-pass hot rolling, the deformation amount of the first pass is 20%, the deformation amount of the subsequent passes gradually increases, the increment is 10%, and the cumulative deformation amount is 80%; The rolling speed is 2 m / s; During the multi-pass hot rolling process, annealing is carried out between adjacent passes, and the annealing temperature is the same as the preheating temperature of the blank;

[0062] The time for annealing between adjacent passes during the multi-pass hot rolling process is as follows: When the thickness exceeds 4 mm, anneal for 15 minutes, when the thickness is 2 - 4 mm, anneal for 10 minutes, and when the thickness is less than 2 mm, anneal for 5 minutes;

[0063] The preheating temperature of the blank is 410 °C, and the preheating time is 30 min;

[0064] Figure 1 It is the metallographic structure diagram of the as-rolled alloy prepared in Example 1; It can be seen from Figure 1 that the microstructure of the as-cast Mg-0.52Ce (wt.%) alloy mainly consists of an α-Mg matrix and ellipsoidal Mg 12 Ce. Figure 2 It is the scanning electron microscope observation diagram of the as-rolled alloy prepared in Example 1; It can be seen from Figure 2 that in addition to the primary eutectic phase, a large number of nano-scale precipitated phases are also precipitated. The type and content of element X are preferably selected in the alloy to increase the free electron density in the alloy and improve the phonon transport efficiency by changing the lattice structure. And heat treatment and a specific hot rolling process are adopted to promote nano-dynamic precipitation, which fully reduces the solute atom content in the Mg matrix and improves the thermal conductivity of the alloy. In addition, the X rare earth element weakens the basal texture and improves the formability of the alloy. In summary, the synergistic improvement of the formability and thermal conductivity of the magnesium alloy is achieved.

[0065] Example 2:

[0066] The difference between this example and Example 1 is that: the preheating temperature of the blank before rolling deformation is 450 °C, the time is 30 min; the cumulative rolling deformation is 90%, and the rolling rate is 2 m / min. The rest is the same as Example 1. The thermal conductivity of the as-rolled Mg-0.52Ce (wt.%) alloy prepared in Example 2 is 169.7 W / (m·K).

[0067] Example 3:

[0068] The difference between this example and Example 2 is that the content of Ce in the Mg-X alloy is 1.02 wt.%, and the balance is Mg. The rest is the same as Example 2. The thermal conductivity of the as-rolled Mg-1.02Ce alloy prepared in Example 3 is 168.6 W / (m·K).

[0069] Example 4:

[0070] The difference between this example and Example 3 is that: the content of La in the Mg-X alloy is 0.48 wt.%, and the balance is Mg. The rest is the same as Example 3. The thermal conductivity of the as-rolled Mg-0.48La alloy prepared in Example 4 is 152.3 W / (m·K).

[0071] Example 5:

[0072] The difference between this embodiment and Embodiment 4 is that the content of Pr in the Mg-X alloy is 0.64 wt.%, and the balance is Mg. The rest is the same as Embodiment 4. The thermal conductivity of the as-rolled Mg-0.64Pr alloy prepared in Embodiment 5 is 150.9 W / (m·K).

Claims

1. A low-cost, ultra-high thermal conductivity and high hot formability magnesium alloy, characterized by: The low-cost, ultra-high thermal conductivity and high hot formability magnesium alloy is a Mg-X alloy, wherein the X element is lanthanum, cerium, neodymium or praseodymium, the X element content in the Mg-X alloy is 0.1-2.0 wt.%, and Mg is the balance.

2. The method for preparing a low-cost, ultra-high thermal conductivity, high hot formability magnesium alloy sheet according to claim 1, characterized in that: The method for preparing a low-cost, ultra-high thermal conductivity and high hot formability magnesium alloy sheet is carried out according to the following steps:

1. Weigh the raw materials according to the mass content of the elements of the Mg-X alloy and clean them; The raw materials are industrial pure magnesium ingots and Mg-X master alloy; 2. Preheating the raw material after the treatment in step 1, then melting it in a protective atmosphere, and cooling it to obtain an alloy ingot; removing the oxide layer on the surface of the alloy ingot, and finally performing a homogenization heat treatment; The temperature of the homogenization heat treatment is 450-520°C, and the holding time is 2-12 hours; The smelting process is as follows: heating an industrial pure magnesium ingot to 680-760° C. to melt, then adding a Mg-X master alloy until it is completely dissolved, keeping the temperature for 30 minutes and stirring, cooling the melt to 680-705° C. after stirring, standing for 10-20 minutes, and finally preparing an alloy ingot by a water cooling process in a protective atmosphere; the stirring time is 2-6 minutes; 3. The alloy ingot obtained in step 2 is prepared into a billet, the billet is preheated, and then the billet is rolled and deformed, and finally air-cooled to complete; The rolling deformation process is as follows: the hot rolling temperature is 350-450°C, multiple hot rolling is performed, the deformation amount of the first pass is 20%, the deformation amount of the subsequent passes gradually increases, the increment is 10%, and the cumulative deformation amount is 60-97%; the rolling rate is 0.5-5.5 m / s; annealing is performed between adjacent passes during the multiple hot rolling process, and the annealing temperature is the same as the preheating temperature of the billet; The annealing time between adjacent passes in the multi-pass hot rolling process is: 15 minutes for thickness exceeding 4 mm, 10 minutes for thickness between 2 and 4 mm, and 5 minutes for thickness less than 2 mm.

3. The method for preparing a low-cost, ultra-high thermal conductivity, high hot formability magnesium alloy sheet according to claim 2, characterized in that: The cleaning process described in step 1 is: use sandpaper to grind and remove pollutants on the surface of the raw material, then use sandpaper to polish and remove impurities and oxide scale on the surface of the raw material, and finally use anhydrous ethanol for ultrasonic cleaning.

4. The method for preparing a low-cost, ultra-high thermal conductivity, high hot formability magnesium alloy sheet according to claim 2, characterized in that: The temperature at which the raw materials are preheated in step 2 is 290-470°C.

5. The method for preparing a low-cost, ultra-high thermal conductivity, high hot formability magnesium alloy sheet according to claim 2, characterized in that: The protective atmosphere in step 2 is composed of a mixed gas of CO2 and SF6, and the volume percentage of SF6 in the mixed gas is 1.0-4.0%.

6. The method for preparing a low-cost, ultra-high thermal conductivity, high hot formability magnesium alloy sheet material according to claim 2, characterized in that: The thickness of the blank in step 3 is 10 to 30 mm.

7. The method for preparing a low-cost, ultra-high thermal conductivity, high hot formability magnesium alloy sheet material according to claim 2, characterized in that: The rolling rate in step 3 is 2 m / s; annealing is performed between adjacent passes during the multi-pass hot rolling process, and the annealing temperature is the same as the preheating temperature of the billet.

8. The method for preparing a low-cost, ultra-high thermal conductivity, high hot formability magnesium alloy sheet according to claim 2, characterized in that: In step 3, the preheating temperature of the blank is 290-470° C., and the preheating time is 10-35 minutes.

9. The method for preparing a low-cost, ultra-high thermal conductivity, high hot formability magnesium alloy sheet material according to claim 2, characterized in that: The rolling deformation process described in step three is: the hot rolling temperature is 400° C., and multiple hot rolling passes are performed. The deformation amount of the first pass is 20%, and the deformation amount of subsequent passes gradually increases by 10%, and the cumulative deformation amount is 80%.

10. The method for preparing a low-cost, ultra-high thermal conductivity, high hot formability magnesium alloy sheet material according to claim 2, characterized in that: The smelting process of step 2 is as follows: heating the industrial pure magnesium ingot to 760°C for melting, then adding the Mg-X master alloy until it is completely dissolved, keeping it warm for 30 minutes and stirring it for 5 minutes. After stirring, cooling the melt to 690°C and standing it for 15 minutes. Finally, preparing the alloy ingot by water cooling in a protective atmosphere.

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