WO2023133978A1 - 一种含有高固溶度稀土元素的高导热镁合金及其制备方法 - Google Patents

一种含有高固溶度稀土元素的高导热镁合金及其制备方法 Download PDF

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WO2023133978A1
WO2023133978A1 PCT/CN2022/078353 CN2022078353W WO2023133978A1 WO 2023133978 A1 WO2023133978 A1 WO 2023133978A1 CN 2022078353 W CN2022078353 W CN 2022078353W WO 2023133978 A1 WO2023133978 A1 WO 2023133978A1
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phase
alloy
thermal conductivity
magnesium alloy
magnesium
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PCT/CN2022/078353
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French (fr)
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李德江
李子昕
胡波
曾小勤
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上海交通大学
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/04—Influencing the temperature of the metal, e.g. by heating or cooling the mould
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/03—Making non-ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C23/00—Alloys based on magnesium
    • C22C23/02—Alloys based on magnesium with aluminium as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C23/00—Alloys based on magnesium
    • C22C23/06—Alloys based on magnesium with a rare earth metal as the next major constituent

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  • the invention relates to the technical field of metallurgy, in particular to a method for improving the thermal conductivity of magnesium alloys containing rare earth elements with high solid solubility.
  • Thermal conductivity is a measure of the ability to dissipate heat. Magnesium alloy has low density, high specific strength and specific stiffness, and can meet the requirements of structure and function at the same time, so it is a material worthy of further study.
  • reference 1 discloses a high-strength and tough Mg-10Gd-3Y-0.3Zr magnesium alloy, whose tensile strength in the as-cast state can reach 368 MPa, but its thermal conductivity at room temperature is only about 30W/(m K);
  • Reference 2 discloses a magnesium alloy Mg-5Y-4Nd-0.7Zr, whose thermal conductivity is only 52W/(m K) under T6 heat treatment, and also discloses a magnesium Alloy Mg-4Y-3Nd-0.7Zr, its thermal conductivity is only 51.3W/(m K) under T6 heat treatment;
  • Reference 3 discloses a magnesium alloy Mg-11Y-5Gd-2Zn-0.65Zr, which The thermal conductivity at room temperature is only 23W/(m ⁇ K).
  • the thermal conductivity of the above-mentioned magnesium alloys is difficult to meet the heat dissipation requirements of heat dissipation structural parts in the fields of automobiles, military industry, and mobile communications.
  • the thermal conductivity of metals is mainly composed of electronic thermal conductivity and phonon thermal conductivity. After Mg is alloyed, its thermal conductivity usually decreases rapidly. The reason is that part of the alloying elements are stored in the Mg matrix in the form of solid solution atoms, which destroy the original lattice arrangement of the Mg matrix, and are actually a scattering source for electrons and phonons, hindering the formation of electrons and phonons. The free movement in the lattice reduces the mean free path of electrons and phonons, resulting in a significant decrease in thermal conductivity.
  • rare earth elements with high solid solubility are usually not considered, but rare earth elements with low solid solubility, such as La, Ce, Pr, Nd, etc., are selected as much as possible to avoid sacrificing magnesium alloys. thermal conductivity.
  • the solid-solution atoms dissolved in the Mg matrix can be further precipitated in the form of the second phase by aging precipitation, so as to moderately increase the thermal conductivity of the Mg alloy.
  • CN105177474A discloses a method for improving the thermal conductivity of metal alloys. Aging treatment is used to improve the thermal conductivity of magnesium alloys. However, this method only improves the thermal conductivity by about 20%, and aging takes a lot of time.
  • the present invention Based on the problem of low thermal conductivity of magnesium alloys containing rare earth elements with high solid solubility existing in the prior art, the present invention provides magnesium alloys with high thermal conductivity containing rare earth elements with high solid solubility and a preparation method thereof. Magnesium alloys can still maintain high thermal conductivity when containing rare earth elements with high solid solubility, and the preparation method of the invention can significantly improve the thermal conductivity of magnesium alloys containing rare earth elements with high solid solubility.
  • the first aspect of the present invention provides a high thermal conductivity magnesium alloy containing rare earth elements with high solid solubility, comprising: RE, the mass fraction of RE in the high thermal conductivity magnesium alloy is 4% to 16%, and the mass fraction of RE in the magnesium Limit solid solubility ⁇ 0.8 at.%; Al, the atomic ratio of Al to RE is 0.3-4; the balance is Mg and unavoidable impurities; the microstructure of high thermal conductivity magnesium alloy includes the first phase and the second phase, the second phase One phase includes a Mg matrix and RE solid-dissolved in the magnesium matrix, the atomic percentage of RE solid-dissolved in the magnesium matrix is 0.05% to 0.2% in the first phase, and the second phase includes Mg-RE phase and Al- RE phase; the thermal conductivity of high thermal conductivity magnesium alloy at room temperature is ⁇ 100W/(m ⁇ K).
  • high solid solubility RE refers to the rare earth elements whose limiting solid solubility in the Mg matrix is above 0.8 at.%.
  • the "limit solid solubility" in the present invention refers to the maximum content of solute atoms that can be dissolved in the magnesium matrix.
  • the solid solution atoms have great damage to the thermal conductivity of the alloy.
  • the magnesium alloy is doped with rare earth elements with high solid solubility, its thermal conductivity can be as low as 50W/(m ⁇ K) , the specific value depends on the type of rare earth element and its content in the alloy, etc.
  • the present invention will control the mass fraction of RE in the magnesium alloy with high solid solubility in magnesium to be 4% to 16%.
  • the mass fraction of RE in the magnesium alloy is controlled at 0.3-4.
  • a sufficient amount of Al is needed to fully replace the RE atoms dissolved in the Mg matrix, but if the amount of Al added is too large, it will also exist in the magnesium matrix in the form of solid solution, which is not conducive to the thermal stability of the magnesium alloy. increase in conductivity.
  • the microstructure of the high thermal conductivity magnesium alloy of the present invention includes a first phase and a second phase, wherein the second phase refers to a phase that is dispersed in a magnesium matrix and exists in crystal form, and phases other than the second phase in the magnesium alloy are defined as
  • the first phase the first phase includes the Mg matrix and the RE solid-dissolved in the magnesium matrix. It is necessary to control the RE solid-dissolved in the magnesium matrix as little as possible, so that the atomic percentage of the solid-dissolved RE in the first phase is 0.05 ⁇ 0.2%, to ensure that the RE in the alloy exists as a second phase rather than solid-solution atoms as much as possible.
  • rare earth elements can at least form a second phase including a Mg-RE phase and an Al-RE phase.
  • RE Before the introduction of Al, RE can form Mg-RE phase with Mg, but because the rare earth elements with high solid solubility in magnesium are selected for use in the present invention, RE tends to be solid-dissolved in the Mg matrix;
  • Al After the introduction of Al, Al can replace the RE in solid solution in the Mg matrix to exist in the form of Al-RE second phase, thereby reducing the influence of the solid solution of RE on the thermal conductivity of the alloy, making the magnesium in the present invention
  • the thermal conductivity of the alloy can be greatly increased to above 100W/(m ⁇ K).
  • the crystal particle size of the second phase is controlled to be 5-10 ⁇ m.
  • the second phase should be as fine and dense as possible. If it is too thick, it will reduce the thermal conductivity of the alloy.
  • the aforementioned rare earth element RE is at least one of Sm, Y, Gd, Dy and Er.
  • the limiting solid solubility of these rare earth elements in the Mg matrix at room temperature is 0.99%, 3.6%, 4.53%, 5.2%, and 6.9% in atomic percentage, respectively.
  • Sm atoms mainly form Al 11 Sm 3 phase with Al atoms
  • Y atoms mainly form Al 2 Y phase with Al atoms
  • Gd atoms mainly form Al 2 Gd phase with Al atoms
  • Dy atoms mainly form Al 2 phase with Al atoms
  • Er atoms mainly form Al 2 Er phase with Al atoms.
  • Table 1 exemplarily shows the equiatomic liquid-phase mixing enthalpy of Sm, Y, Gd and Mg and Al in the above RE. It can be seen that the equiatomic ratio liquid phase mixing enthalpy of Al atoms and Sm, Y, Gd is much lower than the equiatomic ratio liquid phase mixing enthalpy of Mg atoms and Sm, Y, Gd, according to the principle that the lower the energy, the more stable the system, The lower the mixing enthalpy, the easier it is for the two elements to combine to form a second phase, and the more stable the formed second phase, so Al can replace the RE with high solid solubility in the Mg matrix to form Al-RE Mutually.
  • the above-mentioned high thermal conductivity magnesium alloy also includes Ni, thus, the microstructure of the magnesium alloy also includes an Al-Ni grain phase, and the Al-Ni phase belongs to the second phase.
  • Ni is a refractory metal.
  • a small amount of Ni added to a high thermal conductivity magnesium alloy containing Al can form an Al-Ni inoculant with Al as a heterogeneous nucleation substrate for the Al-RE phase, which can effectively refine the Al-RE phase.
  • the denseness of the phase prevents the second phase from being too coarse and avoids a decrease in thermal conductivity.
  • the mass fraction of Ni in the high thermal conductivity magnesium alloy is controlled at 0.05%-0.3%. Excessive Ni will preferentially react with Al in the alloy, resulting in the consumption of Al, so that the Al that can react with RE is reduced and the solid solution RE atoms cannot be fully released from the Mg matrix.
  • the second aspect of the present invention provides a method for preparing a high thermal conductivity magnesium alloy, comprising: S1: adding Al to the molten Mg-RE alloy at 780-820°C in a protective atmosphere, stirring, and standing to obtain Molten high thermal conductivity magnesium alloy; S2: transfer the molten high thermal conductivity magnesium alloy to the mold, and cool it to room temperature at a cooling rate of 100-200K/s to obtain a high thermal conductivity magnesium alloy; the microstructure of the high thermal conductivity magnesium alloy includes the first phase and the second phase, the first phase includes a Mg matrix and RE solid-dissolved in the magnesium matrix, the atomic percentage of the RE solid-dissolved in the magnesium matrix is 0.05-0.2% in the first phase, and the second phase includes Mg -RE phase and Al-RE phase.
  • Al is introduced into the magnesium alloy to improve the thermal conductivity of the magnesium alloy containing rare earth elements with high solid solubility.
  • the Mg-RE alloy must be obtained first.
  • the Mg-RE alloy can be prepared according to the method of the prior art.
  • the required raw materials are weighed according to the required amount, the industrial pure magnesium ingot is put into the crucible, and a protective gas is introduced, and the pure magnesium Melting, and then adding rare earth elements, the form is not limited to Mg-RE master alloy, after introducing RE elements into the system, fully stir the molten metal liquid, let it stand, and cast the molten Mg-RE alloy into the mold while it is hot, After the molten metal is solidified, the corresponding Mg-RE alloy is obtained.
  • the selected RE is at least one of Sm, Y, Gd, Dy and Er, because their limit solid solubility in Mg is relatively large (above 0.8 at.%), so it is desired for the present invention
  • the RE element selected in the specific alloy system of the present invention under the content conditions of the present invention, RE exists in the Mg matrix in the form of solid solution in the prepared Mg-RE alloy, and rarely forms a second phase. Specifically, as the content of RE in the magnesium alloy increases, RE will preferentially dissolve in the Mg matrix, and when the content reaches a certain amount, it will precipitate in the magnesium matrix in the form of the second phase.
  • the desired magnesium alloy containing Al and RE in the present invention can be obtained after casting without aging treatment.
  • the aging treatment of magnesium alloy usually takes tens to hundreds of hours. etc.
  • the preparation method of the present invention can greatly save the preparation time of the magnesium alloy and improve the production efficiency.
  • Ni is also added to the molten Mg-RE alloy.
  • Ni is insoluble in the Mg matrix, it can play a role in refining the grains of the second phase. Therefore, in the preparation process of the high thermal conductivity magnesium alloy of the present invention, Al and Ni can be added, and the order of adding Ni is not affected. Limits can be added before or after Al.
  • addition form of Al in the present invention includes at least one of pure Al, Mg-Al alloy or Al-RE alloy, and the present invention does not limit the addition form of Al.
  • Ni in the present invention is Mg-Ni alloy.
  • the above-mentioned stirring time should be controlled to 10-15 minutes, and the above-mentioned standing time should be controlled to 15-30 minutes. If the stirring time is too short, Al cannot fully replace the rare earth elements present in the magnesium matrix in the form of solid solution atoms, and if the stirring time is too long, a large amount of rare earth elements will be burned and the cost will be increased. Controlling the standing time to be more than 15 minutes can further ensure that the RE dissolved in the magnesium matrix is fully replaced, but it should not exceed 30 minutes, otherwise the second phase will precipitate and the structure of the alloy will be uneven.
  • the alloy should be cooled to room temperature at a cooling rate of 100-200K/s. If the cooling rate is too slow, the second phase will grow, which is not conducive to improving the thermal conductivity; if the cooling rate is too fast, a large number of solid solution atoms will not be released in time, and they will still remain in the Mg matrix, and the second phase cannot be fully formed.
  • the mold is cooled by water cooling to control the cooling rate of the alloy.
  • the protective atmosphere is a mixed gas of SF 6 and CO 2 , wherein the volume ratio of SF 6 and CO 2 is preferably 60:1.
  • the added form of controlling Ni is Mg-Ni alloy.
  • Fig. 1 shows the microstructure photograph of Mg-Sm alloy in the embodiment of the present invention 1;
  • Fig. 2 shows the microstructure photograph of Mg-Sm-Al alloy in the embodiment of the present invention 1;
  • Fig. 3 shows the Sm atomic surface scan element distribution photo of Fig. 1 of the present invention
  • Fig. 4 shows the Sm atomic surface scan element distribution photo of Fig. 2 of the present invention
  • Fig. 5 shows the enlarged Al11Sm3 phase photo of Mg-Sm-Al alloy in Example 1 of the present invention
  • Fig. 6 shows the enlarged Al11Sm3 phase photo of Mg-Sm-Al-Ni alloy in Example 2 of the present invention
  • Fig. 7 shows the Sm atomic surface scan element distribution photo of Mg-Sm-Al-Ni alloy in Comparative Example 1 of the present invention
  • Fig. 8 shows the microstructure photograph of Mg-Sm-Al-Ni alloy in comparative example 2 of the present invention
  • Fig. 9 shows a photo of the microstructure of the Mg-Sm-Al-Ni alloy in Comparative Example 3 of the present invention.
  • Sm is selected as a rare earth element containing high solid solubility in the Mg matrix to prepare a high thermal conductivity magnesium alloy Mg-Sm-Al.
  • the specific preparation process is as follows:
  • Step 1 Prepare Mg-Sm alloy.
  • the mass fraction of Sm is 4%. Specifically, it is obtained through the following steps:
  • Step 1-1 First, according to the alloy composition and stoichiometric ratio, considering the burning loss of Sm during the smelting process, remove the oxide layer from the required raw materials, including industrial pure magnesium ingots and Mg-Sm master alloys, and put them into an oven at 200 °C preheating. Put the crucible brushed with release agent into the oven to dry;
  • Step 1-2 put the industrial pure magnesium ingot into the crucible, raise the temperature to 760°C in the protective atmosphere of the mixed gas of SF 6 and CO 2 (volume ratio 60:1), after the pure magnesium is melted, add Mg-Sm master alloy. Fully stir for 15 minutes, stand still for 25 minutes, remove slag, and cast into a mold. After the molten metal solidifies completely, take out the ingot to prepare the corresponding Mg-Sm alloy.
  • Step 2 Prepare Mg-Sm-Al alloy.
  • step 1 the burning loss of Sm is slightly higher than step 1, only need to ensure that the amount of Sm in the prepared Mg-Sm-Al alloy
  • the mass fraction is 4%, and the remaining steps are the same as step 1. Specifically, it is obtained through the following steps:
  • Step 2-1 After obtaining the molten Mg-Sm metal liquid through step 1, add Al into it in the form of pure Al to the Mg-RE alloy melt, stir well, let it stand for 15 minutes, and raise the temperature to 780°C;
  • Step 2-2 Fully stir for 10 minutes, let stand for 15 minutes to fully incubate the melt, cast it into a water-cooled mold within 20 minutes, and read the cooling rate as 130K/s through a thermocouple.
  • Step 2-3 open the mold, and take out the Mg-Sm-Al alloy.
  • the mass fractions of Al were 0, 0.2%, 0.5%, 1%, 1.5%, 2%, and 2.64% to prepare Mg-4Sm-xAl ingots with different Al contents.
  • Table 2 shows the thermal conductivity of the high thermal conductivity magnesium alloy Mg-Sm-Al (Mg-4Sm-xAl) in this embodiment, as well as the rate of increase in thermal conductivity and the content of Sm atoms dissolved in the Mg matrix with the addition of Al in the alloy , and the thermal conductivity of Mg-4Sm at room temperature is 84.1W/(m K), and the thermal conductivity of this value is 0, and other Mg-4Sm-xAl alloys obtained after introducing Al are calculated increase in thermal conductivity.
  • Figure 1 shows the metallographic structure of the Mg-Sm alloy
  • Figure 2 shows the Mg-Sm-1.5Al alloy
  • Metallographic structure photos
  • Figure 3 is the element distribution diagram of the Sm atomic surface scan in Figure 1
  • Figure 4 is the element distribution diagram of the Sm atomic surface scan in Figure 2.
  • Figure 1 and Figure 3 mainly distribute the Mg matrix containing solid-solution Sm atoms and the Mg 41 Sm 5 phase.
  • Sm is selected as the rare earth element containing high solid solubility in the Mg matrix to prepare a high thermal conductivity magnesium alloy Mg-Sm-Al-Ni.
  • the specific preparation process is as follows:
  • Step 1 preparing a Mg-Sm alloy, wherein the mass fraction of Sm is 4%. Specifically, it is obtained through the following steps:
  • Step 1-1 is the same as embodiment 1.
  • Step 1-2 put the industrial pure magnesium ingot into the crucible, raise the temperature to 760°C in the protective atmosphere of the mixed gas of SF 6 and CO 2 (volume ratio 60:1), after the pure magnesium is melted, add Mg-Sm master alloy. Fully stir for 12 minutes, stand still for 27 minutes, remove the slag, and cast it into a mold. After the molten metal solidifies completely, take out the ingot to prepare the corresponding Mg-Sm alloy.
  • Step 2 Prepare Mg-Sm-Al-Ni alloy. Considering that the temperature in the process of adding Al is higher, so in the preparation process of Mg-Sm molten metal liquid, the burning loss of Sm is slightly higher than step 1, only need to ensure that in the prepared Mg-Sm-Al-Ni alloy The mass fraction of Sm is 4%, and the remaining steps are the same as step 1. Specifically, it is obtained through the following steps:
  • Step 2-1 After the molten Mg-Sm metal liquid is obtained through step 1, Al is added to the Mg-Sm alloy melt in the form of an Mg-Al intermediate alloy, fully stirred, left to stand for 15 minutes, and the temperature is raised to 780°C;
  • Step 2-2 Add Ni with a mass fraction of 0.1% to the melt in the form of Mg-Ni master alloy, fully stir for 15 minutes, and perform electromagnetic shock treatment on the melt, so that a small amount of Ni and Al can quickly form Al-Ni
  • the inoculant was left to stand for 20 minutes to fully inoculate the melt, and it was cast into a water-cooled mold within 30 minutes, and the cooling rate was read as 130K/s by a thermocouple.
  • Step 2-3 open the mold, and take out the Mg-Sm-Al-Ni alloy.
  • Table 3 shows the thermal conductivity of the high thermal conductivity magnesium alloy Mg-Sm-Al-Ni (Mg-4Sm-xAl-0.1Ni) in this example and the variation of thermal conductivity with the amount of Al added in the alloy.
  • the thermal conductivity of Mg-4Sm-0.1Ni at room temperature is 79.2W/(m K), and the thermal conductivity increase rate of this value is 0, and other Mg-4Sm-xAl-0.1 obtained after the introduction of Al is calculated
  • the thermal conductivity of Ni alloy is improved.
  • the addition of Ni consumes a part of Al, making the thermal conductivity of the Mg-Sm-Al-Ni alloy slightly lower than that of the Mg-Sm-Al alloy in Example 1, but in In the test of this embodiment, the Mg-Sm-Al-Ni alloy can still be as high as 130.7 W/(m ⁇ K).
  • Figure 5 shows the enlarged Al 11 Sm 3 phase photo of the Mg-Sm-Al alloy in Example 1
  • Figure 6 shows the enlarged Al 11 Sm 3 phase photo of the Mg-Sm-Al-Ni alloy in this example.
  • the addition of Ni makes the Al 11 Sm 3 phase finer and the phase spacing becomes denser. When the content of the second phase is equivalent to that of Example 1, the thermal conductivity is significantly higher.
  • Sm is selected as a rare earth element with high solid solubility in the Mg matrix to prepare a high thermal conductivity magnesium alloy Mg-Sm-Al-Ni.
  • the specific preparation process is as follows:
  • Step 1 Prepare Mg-Sm alloy, the specific process is the same as that in Example 2.
  • Step 2 Prepare Mg-Sm-Al-Ni alloy. Specifically, it is obtained through the following steps:
  • Step 2-1 Same as Example 2.
  • Step 2-2 Add Ni with a mass fraction of 1.0% to the melt in the form of Mg-Ni master alloy, fully stir for 15 minutes, and perform electromagnetic shock treatment on the melt, so that trace amounts of Ni and Al can quickly form Al-Ni
  • the inoculant was left to stand for 20 minutes to fully inoculate the melt, and it was cast into a water-cooled mold within 30 minutes, and the cooling rate was read as 130K/s by a thermocouple.
  • Step 2-3 Open the mold and take out the Mg-Sm-Al-Ni alloy.
  • FIG. 7 shows the surface-scan element distribution diagram of Sm atoms in the Mg matrix of this comparative example. Compared with Example 2, the number of Sm atoms in the matrix is slightly increased, which leads to a decrease in thermal conductivity.
  • Sm is selected as a rare earth element with high solid solubility in the Mg matrix to prepare a high thermal conductivity magnesium alloy Mg-Sm-Al-Ni.
  • the specific preparation process is as follows:
  • Step 1 Prepare Mg-Sm alloy, the specific process is the same as that in Example 2.
  • Step 2 Prepare Mg-Sm-Al-Ni alloy. Specifically, it is obtained through the following steps:
  • Step 2-1 Same as Example 2.
  • Step 2-2 Add Ni with a mass fraction of 0.1% to the melt in the form of Mg-Ni master alloy, fully stir for 15 minutes, and perform electromagnetic shock treatment on the melt, so that a small amount of Ni and Al can quickly form Al-Ni
  • the inoculant was left to stand for 20 minutes to fully inoculate the melt, and it was cast into a metal mold within 30 minutes, and the cooling rate was read as 35K/s by a thermocouple.
  • Step 2-3 Open the mold and take out the Mg-Sm-Al-Ni alloy.
  • the cooling rate of the Mg-Sm-Al-Ni alloy is controlled to be 35K/s, and the mass fractions of Al are respectively 0, 0.2%, 0.5%, 1%, 1.5%, 2%, and 2.64%.
  • Mg-4Sm-xAl-0.1Ni ingot with Al content is controlled to be 35K/s, and the mass fractions of Al are respectively 0, 0.2%, 0.5%, 1%, 1.5%, 2%, and 2.64%.
  • Fig. 8 shows the microstructure photo of Mg-4Sm-1.5Al-0.1Ni alloy in this comparative example, as can be seen, the second phase of the magnesium alloy of this comparative example is compared with embodiment 1 and embodiment 2, the second The higher the phase content, the excessive second phase will reduce the mechanical properties of the magnesium alloy.
  • Sm is selected as a rare earth element with high solid solubility in the Mg matrix to prepare a high thermal conductivity magnesium alloy Mg-Sm-Al-Ni.
  • the specific preparation process is as follows:
  • Step 1 Prepare Mg-Sm alloy, the specific process is the same as that in Example 2.
  • Step 2 Prepare Mg-Sm-Al-Ni alloy. Specifically, it is obtained through the following steps:
  • Step 2-1 Same as Example 2.
  • Step 2-2 Add Ni with a mass fraction of 0.1% to the melt in the form of Mg-Ni master alloy, stir for 15 minutes, and perform electromagnetic shock treatment on the melt, so that trace amounts of Ni and Al can quickly form Al-Ni inoculation agent, let it stand for 20 minutes to fully incubate the melt, lift the stop valve handle within 30 minutes, and spray the Mg-Sm-Al-Ni metal liquid through the crucible with a belt and spray it onto the quenching roller through the nozzle to obtain Mg-Sm-Al-Ni For Al-Ni alloy, the reading cooling rate is 510K/s.
  • Step 2-3 Open the mold and take out the Mg-Sm-Al-Ni alloy.
  • the cooling rate of the Mg-Sm-Al-Ni alloy is controlled to be 510K/s, and the mass fractions of Al are respectively 0, 0.2%, 0.5%, 1%, 1.5%, 2%, and 2.64%.
  • Mg-4Sm-xAl-0.1Ni ingot with Al content is controlled to be 510K/s, and the mass fractions of Al are respectively 0, 0.2%, 0.5%, 1%, 1.5%, 2%, and 2.64%.
  • Fig. 9 shows the microstructure photo of Mg-4Sm-1.5Al-0.1Ni alloy in this comparative example, it can be seen that compared with Example 1 and Example 2, the proportion of the second phase is significantly smaller.
  • Y is selected as the rare earth element containing high solid solubility in the Mg matrix to prepare high thermal conductivity magnesium alloy Mg-Y-Al-Ni, and the specific preparation process is as follows:
  • Step 1 preparing a Mg-Y alloy, wherein the mass fraction of Y is 4%. Specifically, it is obtained through the following steps:
  • Step 1-1 First, according to the alloy composition and stoichiometric ratio, taking into account the burning loss of Y during the smelting process, remove the oxide layer from the required raw materials, including industrial pure magnesium ingots and Mg-Y master alloys, and put them into an oven at Preheat at 200°C. Put the crucible brushed with release agent into the oven to dry;
  • Step 1-2 Put the industrial pure magnesium ingot into the crucible, raise the temperature to 760°C in the protective atmosphere of the mixed gas of SF 6 and CO 2 (volume ratio 60:1), after the pure magnesium is melted, add Mg-Y master alloy. Fully stir for 15 minutes, stand still for 30 minutes, remove the slag, and cast it into a mold. After the molten metal solidifies completely, take out the ingot to prepare the corresponding Mg-Y alloy.
  • Step 2 prepare Mg-Y-Al-Ni, wherein, considering that the temperature in the process of adding Al is higher, in the preparation process of Mg-Y molten metal liquid, the burning loss of Y will be slightly higher than step 1, in The feeding step should ensure that the mass fraction of Y in the prepared Mg-Y-Al-Ni alloy is 4%, and the rest of the steps are the same as step 1. Specifically, it is obtained through the following steps:
  • Step 2-1 After obtaining the molten Mg-Y metal liquid through the above step 1, add Ni with a mass fraction of 0.03% into the melt in the form of a Mg-Ni master alloy, fully stir for 15 minutes, and raise the temperature to 800°C ;
  • Step 2-2 Add Al to the Mg-Y alloy melt in the form of an Al-RE master alloy and stir it for 13 minutes, and perform electromagnetic shock treatment on the melt, so that a small amount of Ni and Al can quickly form Al- Ni inoculant, let it stand for 20 minutes to fully inoculate the melt, cast it into a water-cooled mold within 30 minutes, and read the cooling rate as 150K/s through a thermocouple.
  • Step 2-3 Open the mold and take out the Mg-Y-Al-Ni alloy.
  • Step 2 Prepare Mg-Y-Al-Ni alloy.
  • Y atoms mainly form Al 2 Y phase with Al atoms, therefore, under the condition of equilibrium solidification, 2.42wt.% Al can completely replace 4wt.% Y.
  • the ideal equilibrium solidification cannot be achieved conditions, so when the Al content is in the range of 0 to 2.42wt.%, the thermal conductivity can reach a peak, and at this time, the Y element will be in solid solution in this high thermal conductivity magnesium alloy Mg-Y-Al-Ni Atomic state, Mg-Y phase (Mg 24 Y 5 phase), and Al-Y phase (Al 2 Y phase) exist.
  • the mass fractions of Al were 0, 0.2%, 0.5%, 1%, 1.5%, 2%, and 2.42% to prepare Mg-4Y-xAl-Ni ingots with different Al contents.
  • Table 7 shows the thermal conductivity of the high thermal conductivity magnesium alloy Mg-Y-Al-Ni (Mg-4Y-xAl-0.03Ni) in this embodiment, as well as the increase in thermal conductivity and the solid solution Y atom content with the addition of Al in the alloy Quantitative changes.
  • the thermal conductivity of Mg-4Y-0.03Ni at room temperature is 60.8W/(m K), and the increase in thermal conductivity of this value is 0, and other Mg-4Y-xAl-0.03Ni obtained after introducing Al are calculated The thermal conductivity of the alloy is increased.
  • Adding Al to the Mg-4Y alloy can increase the thermal conductivity by 114%, and the highest thermal conductivity can reach 130.1W/(m K), which is much higher than the thermal conductivity 53W/(m) of the magnesium alloy AZ91D disclosed in CN107604228B ⁇ K) and some magnesium alloys with low solid solubility Mg-4Ce-2Al-0.5Mn have a thermal conductivity of 105W/(m ⁇ K).
  • Gd is selected as the rare earth element containing high solid solubility in the Mg matrix to prepare a high thermal conductivity magnesium alloy Mg-Gd-Al-Ni.
  • the specific preparation process is as follows:
  • Step 1 preparing a Mg-Gd alloy, wherein the mass fraction of Gd is 10%. Specifically, it is obtained through the following steps:
  • Step 1-1 First, according to the alloy composition and stoichiometric ratio, taking into account the burning loss of Gd during the smelting process, the required raw materials, including industrial pure magnesium ingots and Mg-Gd master alloys, are removed from the oxide layer and put into an oven. Preheat at 200°C. Put the crucible brushed with release agent into the oven to dry;
  • Step 1-2 Put the industrial pure magnesium ingot into the crucible, raise the temperature to 760°C in the protective atmosphere of the mixed gas of SF 6 and CO 2 (volume ratio 60:1), after the pure magnesium is melted, add Mg-Gd master alloy. Fully stir for 15 minutes, stand still for 30 minutes, remove the slag, and cast it into a mold. After the molten metal solidifies completely, take out the ingot to prepare the corresponding Mg-Gd alloy.
  • Step 2 Prepare Mg-Gd-Al-Ni alloy. Considering that the temperature in the process of adding Al is higher, in the preparation process of Mg-Gd molten metal liquid, the burning loss of Gd is slightly higher than step 1, only need to ensure that the Gd in the prepared Mg-Gd-Al-Ni alloy The mass fraction is 10%, and the rest of the steps are the same as step 1. Specifically, it is obtained through the following steps:
  • Step 2-1 After obtaining the molten Mg-Gd metal liquid through step 1, add Ni with a mass fraction of 0.5% into the melt in the form of Mg-Ni master alloy, fully stir for 12 minutes, and raise the temperature to 800°C;
  • Step 2-2 Add Al to the Mg-Gd alloy melt in the form of an Al-RE master alloy and fully stir for 15 minutes, and perform electromagnetic shock treatment on the melt, so that trace amounts of Ni and Al can quickly form Al- Ni inoculant, let it stand for 20 minutes to fully inoculate the melt, cast it into a water-cooled mold within 30 minutes, and read the cooling rate as 130K/s through a thermocouple.
  • Step 2-3 Open the mold and take out the Mg-Gd-Al-Ni alloy.
  • Gd atoms mainly form Al 2 Gd phase with Al atoms. Therefore, under equilibrium solidification conditions, 3.43wt.% Al can completely replace 10wt.% Gd. In the actual operation process, the ideal equilibrium solidification cannot be achieved conditions, so when the Al content is in the range of 0 to 3.43wt.%, the thermal conductivity can reach a peak, at this time the Gd element will be in solid solution in this high thermal conductivity magnesium alloy Mg-Gd-Al-Ni Atomic state, Mg-Gd phase (Mg 5 Gd phase), Al-Gd phase (Al 2 Gd phase) exist.
  • the mass fractions of Al were 0, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, and 3.43% to prepare Mg-10Gd-xAl-0.5Ni ingots with different Al contents.
  • Table 8 shows the thermal conductivity of the high thermal conductivity magnesium alloy Mg-Gd-Al-Ni (Mg-10Gd-xAl-0.5Ni) in this example and the variation of thermal conductivity with the amount of Al added in the alloy.
  • the thermal conductivity of Mg-10Gd-0.5Ni at room temperature is 50.1W/(m ⁇ K), and the thermal conductivity increase rate of this value is 0, and other calculations obtained after introducing Al
  • the thermal conductivity of the Mg-10Gd-xAl-0.5Ni alloy is improved.
  • Adding Al to the Mg-10Gd alloy can increase the thermal conductivity by 137%, and the highest thermal conductivity can reach 118.5W/(m K), much higher than the thermal conductivity of the magnesium alloy AZ91D disclosed in CN107604228B 53W/(m ⁇ K) and some magnesium alloys with low solid solubility Mg-4Ce-2Al-0.5Mn have a thermal conductivity of 105W/(m ⁇ K).
  • Gd and Y are selected together as rare earth elements with high solid solubility in the Mg matrix to prepare a high thermal conductivity magnesium alloy Mg-Gd-Y-Al-Ni.
  • the specific preparation process is as follows:
  • Step 1 Prepare a Mg-Gd-Y alloy, wherein the mass fraction of Gd is 10%, and the mass fraction of Y is 3%. Specifically, it is obtained through the following steps:
  • Step 1-1 First, according to the alloy composition and stoichiometric ratio, considering the burning loss of Gd and Y during the smelting process, remove the required raw materials, including industrial pure magnesium ingots, Mg-Gd master alloy, and Mg-Y master alloy Oxide layer and preheated in an oven at 200°C. Put the crucible brushed with release agent into the oven to dry;
  • Step 1-2 Put the industrial pure magnesium ingot into the crucible, raise the temperature to 760°C in the protective atmosphere of the mixed gas of SF 6 and CO 2 (volume ratio 60:1), after the pure magnesium is melted, add Mg-Gd master alloy and Mg-Y master alloy. Fully stir for 15 minutes, stand still for 30 minutes, remove slag, and cast into a mold. After the molten metal solidifies completely, take out the ingot to prepare the corresponding Mg-Gd-Y alloy.
  • Step 2 Prepare Mg-Gd-Y-Al-Ni, wherein, considering that the temperature in the process of adding Al is higher, in the preparation process of Mg-Gd-Y molten metal liquid, the burning loss of Gd and Y is compared to the step 1 is slightly higher, ensure that the mass fraction of Gd in the preparation of Mg-Gd-Y-Al-Ni is 10%, and the mass fraction of Y is 3%.
  • the rest of the steps are the same as step 1. Specifically, it is obtained through the following steps:
  • Step 2-1 After the molten Mg-Gd-Y metal liquid is obtained through steps A1 and B1, Ni with a mass fraction of 0.2 is added to the melt in the form of an Mg-Ni master alloy, fully stirred for 15 minutes, and the temperature is raised to 800°C;
  • Step 2-2 Add Al to the melt in the form of pure Al to the Mg-Gd-Y alloy melt and stir for 15 minutes, and perform electromagnetic shock treatment on the melt, so that trace amounts of Ni and Al can quickly form Al-Ni inoculation agent, let it stand for 25 minutes to fully incubate the melt, cast it into a water-cooled mold within 30 minutes, and read the cooling rate as 180K/s through a thermocouple.
  • Step 2-3 Open the mold and take out the Mg-Gd-Y-Al-Ni alloy.
  • Step 2 Prepare Mg-Gd-Y-Al-Ni alloy.
  • Table 9 shows the thermal conductivity of the high thermal conductivity magnesium alloy Mg-10Gd-3Y-xAl-0.2Ni in this example, the increase in thermal conductivity and the content of Gd and Y atoms in solid solution vary with the amount of Al added in the alloy.
  • the thermal conductivity of Mg-10Gd-3Y-0.2Ni at room temperature is 34.4W/(m ⁇ K). Taking the thermal conductivity increase rate of this value as 0, calculate other Mg-10Gd-3Y- The thermal conductivity of xAl-0.2Ni alloy is improved.
  • Adding Al to the Mg-10Gd-3Y alloy can increase the thermal conductivity by 216%, and the highest thermal conductivity can reach 108.6W/(m K), indicating that even for a magnesium alloy mixed with multiple REs, the addition of Al can greatly Significantly increased thermal conductivity.
  • the present invention does not limit the types of rare earth elements with high solid solubility added to magnesium alloys, as long as the thermal conductivity of magnesium alloys with such rare earth elements can be greatly improved and the performance expected by the present invention, such as thermal conductivity, can be achieved. rate.

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Abstract

一种含有高固溶度稀土元素的高导热镁合金及其制备方法，所述高导热镁合金包括RE，RE在高导热镁合金中的质量分数为4％～16％，且在镁中的极限固溶度≥0.8at.％；Al，Al与RE的原子比在0.3～4；余量为Mg及不可避免的杂质；所述高导热镁合金的微观组织包括第一相和第二相，第一相包括Mg基体和固溶在镁基体中的RE，固溶在镁基体中的RE在第一相中的原子数百分比为0.05～0.2％，第二相包括Mg-RE相和Al-RE相，该高导热镁合金在常温下的热导率≥100W/(m·K)，与现有的含有高固溶度稀土元素的镁合金相比，导热性能明显提升。

Description

一种含有高固溶度稀土元素的高导热镁合金及其制备方法 技术领域
本发明涉及冶金技术领域，尤其涉及一种提升含有高固溶度稀土元素的镁合金的热导率的方法。
背景技术
在航空航天，汽车产业，5G行业等的飞速发展下，要求零部件在具有卓越的力学性能的同时要兼顾散热能力，因此对产品的散热能力和力学性能有了更高的要求。热导率是衡量散热能力的指标。镁合金密度低，比强度和比刚度高，能够同时满足结构和功能等方面的需求，是值得深入研究的材料。
传统的镁合金高温力学性能差，而如Gd，Y，Sm等的稀土元素(Rare Earth Element,RE)由于具有独特的核外电子排布，在Mg基体中具有较大的极限固溶度，并且与Mg的原子半径差存在明显差异，可以起到良好的强化作用，添加高固溶度稀土元素RE进入纯镁后进行合金化，镁合金的力学性能度往往会得到大幅度提升，高温力学性能也会显著改善，但是热导率会迅速下降。
例如，参考文献1公开了一种高强韧的Mg-10Gd-3Y-0.3Zr镁合金，其在铸态下的抗拉强度能达到368MPa，但是其室温热导率在T6热处理下仅约为30W/(m·K)；参考文献2公开了一种镁合金Mg-5Y-4Nd-0.7Zr，其在T6热处理下热导率仅有52W/(m·K)，还公开了一种镁合金Mg-4Y-3Nd-0.7Zr，其在T6热处理下热导率仅有51.3W/(m·K)；参考文献3公开了一种镁合金Mg-11Y-5Gd-2Zn-0.65Zr，它的室温热导率只有23W/(m·K)。上述镁合金的热导率均难以满足汽车、军工和移动通讯等领域的散热结构件的散热需求。
金属的热导率主要由电子热导率和声子热导率组成，Mg合金化后，通常其热导率会迅速下降。原因是一部分合金元素以固溶原子的形式储存在Mg基体中，固溶原子破坏了Mg基体原有的点阵排列，对于电子和声子实际上是一种散射源，阻碍了电子和声子在晶格内的自由运动，降低了电子和声子的平均自由程，导致热导率明显降 低。另一部分合金元素以第二相的形式出现在枝晶间隙，在Mg基体和第二相的界面处会产生小部分的晶格畸变，成为电子和声子的另一种散射源，但是相比于固溶原子，第二相造成的晶格畸变要小得多。有研究指出，固溶原子与第二相相比对热导率的影响相差能够到达一个数量级，镁合金中固溶原子量对热导率的影响最明显。所以在设计开发高导热镁合金的时候，通常不考虑固溶度高的稀土元素，而是尽可能选择固溶度低的稀土元素，如La，Ce，Pr，Nd等，以避免牺牲镁合金的热导率。
实践中可以进一步通过时效析出的方式，将溶解在Mg基体中的固溶原子以第二相的形式析出，来适度提升Mg合金的热导率。例如，CN105177474A公开了一种提高金属合金导热性能的方法，对镁合金采用时效处理以提升其导热性能，但是该方法对热导率的提升大约仅有20％，且时效需耗费大量的时间。
因此，需要一种能快速释放在Mg基体中含有的高固溶度的稀土原子的方法，将合金元素由固溶原子转化为第二相的形式存在。
参考文献1：陈长江.发动机活塞用耐热稀土镁合金的开发研究[D].上海:上海交通大学，2010。
参考文献2：Materials Science and Engineering A,2002,302(1):37-45。
参考文献3：Journal of Alloys and Compounds,2009,487:560-563。
发明内容
基于现有技术中存在的含有高固溶度稀土元素的镁合金存在的热导率低的问题，本发明提供了含有高固溶度稀土元素的高导热镁合金及其制备方法，本发明的镁合金在含有高固溶度稀土元素的情况下，仍然能保持高热导率，采用本发明的制备方法，能够显著提升含有高固溶度稀土元素的镁合金的热导率。
本发明的第一方面，提供了一种含有高固溶度稀土元素的高导热镁合金，包括：RE，RE在高导热镁合金中的质量分数为4％～16％，且在镁中的极限固溶度≥0.8at.％；Al，Al与RE的原子比在0.3～4；余量为Mg及不可避免的杂质；高导热镁合金的微观组织包括第一相和第二相，第一相包括Mg基体和固溶在镁基体中的RE，固溶在镁基体中的RE在第一相中的原子数百分比为0.05％～0.2％，第二相包括Mg-RE相和Al-RE相；高导热镁合金在常温下的热导率≥100W/(m·K)。
在本发明中，高固溶度RE是指在Mg基体中的极限固溶度在0.8at.％以上的稀土元素。本发明出现的“极限固溶度”是指在镁基体中所能溶解的溶质原子的最大含量。 但是，如上，固溶原子对合金的热导率有很大伤害，通常如果镁合金中掺有具有很高固溶度的稀土元素，其热导率可以低至50W/(m·K)以下，具体值取决于稀土元素的类型及其在合金中的含量等。
本发明要控制在镁中具有高固溶度的RE在镁合金中的质量分数为4％～16％，为了确保获得的高导热镁合金具有所需的热导率，如果RE过多，那么引入Al后大量生成第二相也会对镁合金的热导率造成伤害。根据选用的稀土元素的具体类型，控制镁合金中Al与RE的原子比在0.3～4。在本发明的镁合金中需要足量的Al以充分置换固溶在Mg基体中的RE原子，但如果Al加入量过大也会以固溶的形式存在于镁基体中，不利于镁合金热导率的提升。
本发明的高导热镁合金的微观组织包括第一相和第二相，其中第二相指的是分散在镁基体中以晶体形式存在的相，镁合金中除了第二相以外的相定义为第一相，第一相包括Mg基体和固溶在镁基体中的RE，要控制固溶在镁基体中的RE尽可能少，使固溶的RE在第一相中的原子数百分比为0.05～0.2％，确保合金中的RE尽可能以第二相而不是固溶原子的形式存在。具体地，稀土元素至少能形成包括Mg-RE相和Al-RE相在内的第二相。在未引入Al之前，RE可以与Mg形成Mg-RE相，但是由于本发明中选用的是在镁中具有高固溶度的稀土元素，因而RE更倾向于在固溶在Mg基体中；在引入Al之后，Al能将固溶在Mg基体中的RE置换出来以Al-RE第二相的形式存在，从而减小由于RE固溶对合金热导率带来的影响，使本发明中镁合金的热导率能大幅提升至100W/(m·K)以上。
进一步地，控制第二相的晶体颗粒尺寸在5～10μm。第二相应当越细越密集越好，过于粗大会导致合金的热导率降低。
可选地，上述稀土元素RE为Sm，Y，Gd，Dy和Er中的至少一种。
这些稀土元素在Mg基体中室温下的极限固溶度以原子数百分比计分别为0.99％，3.6％，4.53％，5.2％，6.9％。
示例性地，Sm原子主要和Al原子形成Al 11Sm 3相，Y原子主要和Al原子形成Al 2Y相，Gd原子主要和Al原子形成Al 2Gd相，Dy原子主要和Al原子形成Al 2Dy相，Er原子主要和Al原子形成Al 2Er相。
表1示例性地给出了上述RE中Sm、Y、Gd与Mg和Al的等原子比液相混合焓。可以看出，Al原子和Sm、Y、Gd的等原子比液相混合焓远低于Mg原子和Sm、Y、Gd的等原子比液相混合焓，按照能量越低系统越稳定的原理，混合焓越低，两种元 素越容易结合形成第二相，形成的第二相也越稳定，因此Al能将固溶在Mg基体中的高固溶度稀土原子RE置换出来，形成Al-RE相。
表1.
Figure PCTCN2022078353-appb-000001
进一步地，上述高导热镁合金还包括Ni，如此，镁合金的微观组织还包括Al-Ni颗粒相，Al-Ni相属于第二相。
Ni是一种难熔金属，微量的Ni添加至含有Al的高导热镁合金中，能和Al形成Al-Ni孕育剂作为Al-RE相的异质形核基底，可以有效细化Al-RE相的密集程度，防止第二相过于粗大，避免热导率降低。
进一步地，Ni在高导热镁合金中的质量分数控制在0.05％～0.3％。过量的Ni会与合金中的Al优先反应，导致Al的消耗，这样能与RE反应的Al减少而无法将固溶的RE原子从Mg基体中充分释放。
本发明的第二方面，提供了一种高导热镁合金的制备方法，包括，S1：在780～820℃和保护气氛中，向熔融的Mg-RE合金中加入Al，搅拌、静置，得到熔融的高导热镁合金；S2：将熔融的高导热镁合金转移至模具中，以100～200K/s的冷却速度冷至室温，获得高导热镁合金；高导热镁合金的微观组织包括第一相和第二相，第一相包括Mg基体和固溶在镁基体中的RE，固溶在镁基体中的RE在第一相中的原子数百分比为0.05～0.2％，第二相包括Mg-RE相和Al-RE相。
本发明中要向镁合金中引入Al以提高含有高固溶度稀土元素的镁合金的导热性能，在加入Al之前，要先获得Mg-RE合金。Mg-RE合金按照现有技术的方法制备即可，具体地，按照所需的量称量所需原料，将工业纯镁锭放入坩埚中，并通入保护气体，在高温下将纯镁熔化，然后加入稀土元素，形式不限于Mg-RE中间合金，在体系中引入RE元素后对熔融的金属液进行充分地搅拌、静置，趁热将熔融的Mg-RE合金浇铸至模具中，待金属液凝固之后即得到相应的Mg-RE合金。
在本发明中，选用的RE为Sm，Y，Gd，Dy和Er中的至少一种，由于它们在Mg中的极限固溶度较大(在0.8at.％以上)，因此针对本发明期望的特定合金体系中选用的RE元素，在本发明的含量条件下，RE在制得的Mg-RE合金中几乎是以固溶形式存在于Mg基体中，极少形成第二相。具体地，随着上述RE在镁合金中的含量增加，RE会优先固溶在Mg基体中，当含量达到一定量时会以第二相的形式在镁基体 中析出。
需要控制Al的加入温度在780～820℃，控制温度高于780℃可以使Al充分与Mg-RE融合，配合搅拌和静置能使Al最大程度上置换固溶在Mg基体中的RE原子；若温度过低，由于Al和RE结合能力较强，Al和RE会过早的形核长大，防止Al-RE相在凝固过程中长的过于粗大。控制温度在820℃以内有利于节能。
采用本发明的制备方法，无需经过时效处理，在浇铸之后即可得到本发明期望的含有Al和RE的镁合金，现有技术中对镁合金的时效处理通常需要几十小时到上百小时不等，本发明的制备方法与之相比可以大幅度地节约镁合金的制备时间，提高生产效率。
本发明在上述S1中，还要向所述熔融的Mg-RE合金中加入Ni。
如上，由于Ni在Mg基体中难溶，可以起到细化第二相晶粒的作用，因此在本发明的高导热镁合金的制备过程中，可以加入Al和Ni，Ni的加入顺序不受限制，可以在Al之前或之后加入。
进一步地，在本发明中Al的加入形式包括纯Al、Mg-Al合金或Al-RE合金中的至少一种，本发明对Al的加入形式不作限制。
进一步地，本发明中Ni的加入形式为Mg-Ni合金。
进一步地，本发明中要控制上述搅拌的时间10～15min，控制上述静置的时间15～30min。搅拌时间过短，Al不能充分置换出以固溶原子形式存在于镁基体中的稀土元素，搅拌时间过长会导致大量稀土元素的烧损、增加成本。控制静置时间在15min以上可以进一步确保固溶在镁基体中的RE被充分置换出来，但不宜超过30min，否则造成第二相沉淀，使合金的组织不均匀。
将获得的熔融的Mg-RE-Al合金转移至模具中后，要控制合金以100～200K/s的冷却速度冷至室温。冷速过慢会使第二相长大，不利于提高热导率；冷速过快会导致大量的固溶原子来不及释放出来，依旧保留在Mg基体内，无法充分形成第二相。
进一步地，采用水冷对模具进行冷却，以控制合金的冷却速度。
上述反应需要在保护气氛中进行，具体地，在本发明中，保护气氛为SF 6和CO 2的混合气体，其中SF 6和CO 2的体积比优选为60：1。
进一步地，控制Ni的加入形式为Mg-Ni合金。
综上，采用本发明的制备方法制备高导热镁合金，由于在合金体系中引入了Al，并且严格控制合金化反应的温度、搅拌和静置的时间以及合金的冷却速度等，使得含 有高固溶度的稀土元素在Mg基体中的固溶量低，能够显著提升本发明中含有高固溶度稀土元素的镁合金的热导率。
附图说明
图1示出本发明实施例1中Mg-Sm合金的微观组织照片；
图2示出本发明实施例1中Mg-Sm-Al合金的微观组织照片；
图3示出本发明图1的Sm原子面扫元素分布照片；
图4示出本发明图2的Sm原子面扫元素分布照片；
图5示出本发明实施例1中Mg-Sm-Al合金放大的Al 11Sm 3相照片；
图6示出本发明实施例2中Mg-Sm-Al-Ni合金放大的Al 11Sm 3相照片；
图7示出本发明对比例1中Mg-Sm-Al-Ni合金的Sm原子面扫元素分布照片；
图8示出本发明对比例2中Mg-Sm-Al-Ni合金的微观组织照片；
图9示出本发明对比例3中Mg-Sm-Al-Ni合金的微观组织照片。
具体实施方式
以下由特定的具体实施例说明本发明的实施方式，本领域技术人员可由本说明书所揭示的内容轻易地了解本发明的其他优点及功效。虽然本发明的描述将结合较佳实施例一起介绍，但这并不代表此发明的特征仅限于该实施方式。恰恰相反，结合实施方式作发明介绍的目的是为了覆盖基于本发明的权利要求而有可能延伸出的其它选择或改造。为了提供对本发明的深度了解，以下描述中将包含许多具体的细节。本发明也可以不使用这些细节实施。此外，为了避免混乱或模糊本发明的重点，有些具体细节将在描述中被省略。需要说明的是，在不冲突的情况下，本发明中的实施例及实施例中的特征可以相互组合。
下面将结合具体的实施例对本发明的高固溶度稀土镁合金及其制备方法做进一步地解释和说明，然而该解释和说明并不对本发明的技术方案构成不当限定。
实施例1
在本实施例中选择Sm作为在Mg基体中含有高固溶度的稀土元素来制备高导热镁合金Mg-Sm-Al，具体的制备过程如下：
步骤1：制备Mg-Sm合金。
其中，Sm的质量分数为4％。具体通过以下步骤获得：
步骤1-1、首先按照合金成分及化学计量比，考虑Sm在熔炼过程中的烧损，将所需的原料，包括工业纯镁锭和Mg-Sm中间合金去除氧化层并放入烘箱于200℃预热。将刷好脱模剂的坩埚一并放入烘箱烘干；
步骤1-2、将工业纯镁锭放入坩埚中，在通有SF 6和CO 2的混合气体(体积比为60：1)的保护气氛中升温至760℃，待纯镁熔化后，加入Mg-Sm中间合金。充分搅拌15min，静置25min，扒渣，浇铸至模具中，待熔融的金属液凝固完全后，取出铸锭，制备出相应的Mg-Sm合金。
步骤2：制备Mg-Sm-Al合金。
考虑到加Al过程中的温度更高，因此在Mg-Sm熔融金属液的制备过程中，Sm的烧损相比步骤1略高，只需确保制备得到的Mg-Sm-Al合金中Sm的质量分数为4％即可，其余步骤同步骤1。具体通过以下步骤获得：
步骤2-1、通过步骤1获得熔融的Mg-Sm金属液后，向其内将Al以纯Al的方式添加至Mg-RE合金熔体中充分搅拌，静置15min，温度升温至780℃；
步骤2-2、充分搅拌10min，静置15min，使熔体充分孕育，在20min内浇铸至水冷的模具中，通过热电偶读取冷却速率为130K/s。
步骤2-3，开模，取出Mg-Sm-Al合金。
Sm原子主要和Al原子形成Al 11Sm 3相，因此，在平衡凝固条件下，2.64wt.％的Al能将4wt.％的Sm完全置换出来，在实际的操作过程中，无法达到理想的平衡凝固条件，因此当Al含量在0～2.64wt.％的范围内时，热导率能够达到一个峰值，此时Sm元素在这种高导热镁合金Mg-Sm-Al中会分别以固溶原子态、Mg-Sm相(Mg 41Sm 5相)、Al-Sm相(Al 11Sm 3相)存在。
取Al的质量分数分别为0，0.2％，0.5％，1％，1.5％，2％，2.64％制备出具有不同Al含量的Mg-4Sm-xAl铸锭。
表2示出本实施例中高导热镁合金Mg-Sm-Al(Mg-4Sm-xAl)的热导率以及热导率提升幅度和固溶在Mg基体中的Sm原子含量随合金中Al加入量的变化，以及Mg-4Sm在常温下的热导率为84.1W/(m·K)，以该数值的热导率提升幅度为0，计算得到其他引入Al后获得的Mg-4Sm-xAl合金的热导率提升幅度。
表2.
Figure PCTCN2022078353-appb-000002
Figure PCTCN2022078353-appb-000003
从表2中可以看出，Al的加入对Mg-Sm合金的热导率提升作用明显，图1示出Mg-Sm合金的金相组织照片，图2示出Mg-Sm-1.5Al合金的金相组织照片，图3为图1的Sm原子面扫元素分布图，图4为图2的Sm原子面扫元素分布图。图1和图3主要分布着含有固溶Sm原子的Mg基体和Mg 41Sm 5相，从图2和图4可以看出Al加入使得固溶在Mg基体中的Sm原子含量显著降低，同时第二相在合金中的比例明显提升，因而导致了合金热导率的提升。
实施例2
在本实施例中选择Sm作为在Mg基体中含有高固溶度的稀土元素来制备高导热镁合金Mg-Sm-Al-Ni，具体的制备过程如下：
步骤1：制备Mg-Sm合金，其中，Sm的质量分数为4％。具体通过以下步骤获得：
步骤1-1同实施例1。
步骤1-2、将工业纯镁锭放入坩埚中，在通有SF 6和CO 2的混合气体(体积比为60：1)的保护气氛中升温至760℃，待纯镁熔化后，加入Mg-Sm中间合金。充分搅拌12min，静置27min，扒渣，浇铸至模具中，待熔融的金属液凝固完全后，取出铸锭，制备出相应的Mg-Sm合金。
步骤2：制备Mg-Sm-Al-Ni合金。考虑到加Al过程中的温度更高，因此在Mg-Sm熔融金属液的制备过程中，Sm的烧损相比步骤1略高，只需确保制备得到的Mg-Sm-Al-Ni合金中Sm的质量分数为4％即可，其余步骤同步骤1。具体通过以下步骤获得：
步骤2-1：通过步骤1获得熔融的Mg-Sm金属液后，向其内将Al以Mg-Al中间合金的方式添加至Mg-Sm合金熔体中充分搅拌，静置15min，温度升温至780℃；
步骤2-2：将质量分数为0.1％的Ni以Mg-Ni中间合金的方式添加至熔体中，充分搅拌15min，对熔体进行电磁震荡处理，使微量的Ni与Al快速形成Al-Ni孕育剂，静置20min，使熔体充分孕育，30min内浇铸至水冷的模具中，通过热电偶读取冷却速率为130K/s。
步骤2-3，开模，取出Mg-Sm-Al-Ni合金。
本实施例在合金中加入了质量分数为0.1％的Ni，取Al的质量分数分别为0，0.2％，0.5％，1％，1.5％，2％，2.64％制备出拥有不同Al含量的Mg-4Sm-xAl-0.1Ni铸锭。
表3示出本实施例中高导热镁合金Mg-Sm-Al-Ni(Mg-4Sm-xAl-0.1Ni)的热导率以及热导率提升幅度随合金中Al加入量的变化。Mg-4Sm-0.1Ni在常温下的热导率为79.2W/(m·K)，以该数值的热导率提升幅度为0，计算得到其他引入Al后获得的Mg-4Sm-xAl-0.1Ni合金的热导率提升幅度。
表3.
Figure PCTCN2022078353-appb-000004
从表3中可以看出，Ni的加入对消耗了一部分Al，使Mg-Sm-Al-Ni合金的热导率于实施例1中的Mg-Sm-Al合金相比略有下降，但是在本实施例的测试中，Mg-Sm-Al-Ni合金依然能高达130.7W/(m·K)。图5示出实施例1中Mg-Sm-Al合金放大的Al 11Sm 3相照片，图6示出本实施例中Mg-Sm-Al-Ni合金放大的Al 11Sm 3相照片，对比可知Ni的加入使得Al 11Sm 3相细化，相间距变得更密集，在第二相含量与实施例1相当的情况下，热导率的提升幅度明显更高。
对比例1
选择Sm作为在Mg基体中含有高固溶度的稀土元素来制备高导热镁合金Mg-Sm-Al-Ni，具体的制备过程如下：
步骤1：制备Mg-Sm合金，具体工艺同实施例2。
步骤2：制备Mg-Sm-Al-Ni合金。具体通过以下步骤获得：
步骤2-1：同实施例2。
步骤2-2：将质量分数为1.0％的Ni以Mg-Ni中间合金的方式添加至熔体中，充分搅拌15min，对熔体进行电磁震荡处理，使微量的Ni与Al快速形成Al-Ni孕育剂，静置20min，使熔体充分孕育，30min内浇铸至水冷的模具中，通过热电偶读取冷却速率为130K/s。
步骤2-3：开模，取出Mg-Sm-Al-Ni合金。
本对比例在合金中加入了质量分数为1.0％的Ni，取Al的质量分数分别为0，0.2％，0.5％，1％，1.5％，2％，2.64％制备出拥有不同Al含量的Mg-4Sm-xAl-1Ni铸锭。
表4.
Figure PCTCN2022078353-appb-000005
从表4中可以看出，与实施例2相比，Ni的大量加入使Mg-Sm-Al合金的热导率稍有下降。过量的Ni会消耗大量的Al，使得原本要和Sm原子结合的Al原子减少，造成最终固溶在基体的Sm原子更多。图7示出本对比例的Mg基体中Sm原子面扫元素分布图，相比实施例2，基体中的Sm原子略有增多，因此导致热导率有所降低。
对比例2
选择Sm作为在Mg基体中含有高固溶度的稀土元素来制备高导热镁合金Mg-Sm-Al-Ni，具体的制备过程如下：
步骤1：制备Mg-Sm合金，具体工艺同实施例2。
步骤2：制备Mg-Sm-Al-Ni合金。具体通过以下步骤获得：
步骤2-1：同实施例2。
步骤2-2：将质量分数为0.1％的Ni以Mg-Ni中间合金的方式添加至熔体中，充分搅拌15min，对熔体进行电磁震荡处理，使微量的Ni与Al快速形成Al-Ni孕育剂，静置20min，使熔体充分孕育，30min内浇铸至金属型模具中，通过热电偶读取冷却速率为35K/s。
步骤2-3：开模，取出Mg-Sm-Al-Ni合金。
本对比例控制Mg-Sm-Al-Ni合金的冷却速度为35K/s，取Al的质量分数分别为0，0.2％，0.5％，1％，1.5％，2％，2.64％制备出拥有不同Al含量的Mg-4Sm-xAl-0.1Ni铸锭。
表5.
Figure PCTCN2022078353-appb-000006
从表5中可以看出，与实施例2相比，控制Mg-4Sm-xAl-0.1Ni合金的冷却速度为35K/s，对该合金的热导率的提升作用不明显。
图8示出本对比例中Mg-4Sm-1.5Al-0.1Ni合金的微观组织照片，可以看出，本对比例的镁合金的第二相与实施例1和实施例2相比，第二相含量更高，过多的第二相使镁合金的力学性能下降。
对比例3
选择Sm作为在Mg基体中含有高固溶度的稀土元素来制备高导热镁合金Mg-Sm-Al-Ni，具体的制备过程如下：
步骤1：制备Mg-Sm合金，具体工艺同实施例2。
步骤2：制备Mg-Sm-Al-Ni合金。具体通过以下步骤获得：
步骤2-1：同实施例2。
步骤2-2：将质量分数为0.1％的Ni以Mg-Ni中间合金的方式添加至熔体中，搅拌15min，对熔体进行电磁震荡处理，使微量的Ni与Al快速形成Al-Ni孕育剂，静置20min，使熔体充分孕育，30min内，提起止流阀柄，将Mg-Sm-Al-Ni金属液通过甩带坩埚并经过喷嘴喷出至急冷辊上，获得Mg-Sm-Al-Ni合金，读取冷却速率为510K/s。
步骤2-3：开模，取出Mg-Sm-Al-Ni合金。
本对比例控制Mg-Sm-Al-Ni合金的冷却速度为510K/s，取Al的质量分数分别为0，0.2％，0.5％，1％，1.5％，2％，2.64％制备出拥有不同Al含量的Mg-4Sm-xAl-0.1Ni铸锭。
表6.
Figure PCTCN2022078353-appb-000007
从表6中可以看出，与实施例2相比，控制Mg-4Sm-xAl-1Ni合金的冷却速度为510K/s，会导致镁合金的热导率偏低。这只由于冷却速度过快造成大量的固溶Sm原子留在Mg基体中来不及释放出来。
图9示出本对比例中Mg-4Sm-1.5Al-0.1Ni合金的微观组织照片，可以看出，与实施例1和实施例2相比，第二相的比例明显变小。
实施例3
在本实施例中选择Y作为在Mg基体中含有高固溶度的稀土元素来制备高导热镁 合金Mg-Y-Al-Ni，具体的制备过程如下：
步骤1：制备Mg-Y合金，其中，Y的质量分数为4％。具体通过以下步骤获得：
步骤1-1：首先按照合金成分及化学计量比，考虑到Y在熔炼过程中的烧损，将所需的原料，包括工业纯镁锭和Mg-Y中间合金去除氧化层并放入烘箱于200℃预热。将刷好脱模剂的坩埚一并放入烘箱烘干；
步骤1-2：将工业纯镁锭放入坩埚中，在通有SF 6和CO 2的混合气体(体积比为60：1)的保护气氛中升温至760℃，待纯镁熔化后，加入Mg-Y中间合金。充分搅拌15min，静置30min，扒渣，浇铸至模具中，待熔融的金属液凝固完全后，取出铸锭，制备出相应的Mg-Y合金。
步骤2：制备Mg-Y-Al-Ni，其中，考虑到加Al过程中的温度更高，在Mg-Y熔融金属液的制备过程中，Y的烧损相比步骤1会略高，在投料步骤要确保制备得到的Mg-Y-Al-Ni合金中Y的质量分数为4％即可，其余步骤同步骤1。具体通过以下步骤获得：
步骤2-1：通过上述步骤1获得熔融的Mg-Y金属液后，将质量分数为0.03％的Ni以Mg-Ni中间合金的方式添加至熔体中，充分搅拌15min，温度升温至800℃；
步骤2-2：向熔体内将Al以Al-RE中间合金的方式添加至Mg-Y合金熔体中充分搅拌13min，对熔体进行电磁震荡处理，使微量的Ni与Al快速形成Al-Ni孕育剂，静置20min，使熔体充分孕育，30min内浇铸至水冷的模具中，通过热电偶读取冷却速率为150K/s。
步骤2-3：开模，取出Mg-Y-Al-Ni合金。
步骤2：制备Mg-Y-Al-Ni合金。
Y原子主要和Al原子形成Al 2Y相，因此，在平衡凝固条件下，2.42wt.％的Al能将4wt.％的Y完全置换出来，在实际的操作过程中，无法达到理想的平衡凝固条件，因此当Al含量在0～2.42wt.％的范围内时，热导率能够达到一个峰值，此时Y元素在这种高导热镁合金Mg-Y-Al-Ni中会分别以固溶原子态、Mg-Y相(Mg 24Y 5相)、Al-Y相(Al 2Y相)存在。
取Al的质量分数分别为0，0.2％，0.5％，1％，1.5％，2％，2.42％制备出拥有不同Al含量的Mg-4Y-xAl-Ni铸锭。
表7示出本实施例中高导热镁合金Mg-Y-Al-Ni(Mg-4Y-xAl-0.03Ni)的热导率以及热导率提升幅度和固溶的Y原子含量随合金中Al加入量的变化。Mg-4Y-0.03Ni在 常温下的热导率为60.8W/(m·K)，以该数值的热导率提升幅度为0，计算其他引入Al后获得的Mg-4Y-xAl-0.03Ni合金的热导率提升幅度。
表7.
Figure PCTCN2022078353-appb-000008
添加Al至Mg-4Y合金中，热导率可提升114％，最高热导率可达130.1W/(m·K)，远高于CN107604228B中公开的镁合金AZ91D的热导率53W/(m·K)和部分低固溶度的镁合金Mg-4Ce-2Al-0.5Mn热导率105W/(m·K)。
实施例4
在本实施例中选择Gd作为在Mg基体中含有高固溶度的稀土元素来制备高导热镁合金Mg-Gd-Al-Ni，具体的制备过程如下：
步骤1：制备Mg-Gd合金，其中，Gd的质量分数为10％。具体通过以下步骤获得：
步骤1-1、首先按照合金成分及化学计量比，考虑到Gd在熔炼过程中的烧损，将所需的原料，包括工业纯镁锭和Mg-Gd中间合金去除氧化层并放入烘箱于200℃预热。将刷好脱模剂的坩埚一并放入烘箱烘干；
步骤1-2：将工业纯镁锭放入坩埚中，在通有SF 6和CO 2的混合气体(体积比为60：1)的保护气氛中升温至760℃，待纯镁熔化后，加入Mg-Gd中间合金。充分搅拌15min，静置30min，扒渣，浇铸至模具中，待熔融的金属液凝固完全后，取出铸锭，制备出相应的Mg-Gd合金。
步骤2：制备Mg-Gd-Al-Ni合金。考虑到加Al过程中的温度更高，在Mg-Gd熔融金属液的制备过程中，Gd的烧损相比步骤1略高，只需确保制备得到的Mg-Gd-Al-Ni合金中Gd的质量分数为10％即可，其余步骤同步骤1。具体通过以下步骤获得：
步骤2-1：通过步骤1获得熔融的Mg-Gd金属液后，将质量分数为0.5％的Ni以Mg-Ni中间合金的方式添加至熔体中，充分搅拌12min，温度升温至800℃；
步骤2-2：向熔体内将Al以Al-RE中间合金的方式添加至Mg-Gd合金熔体中充分搅拌15min，对熔体进行电磁震荡处理，使微量的Ni与Al快速形成Al-Ni孕育剂，静置20min，使熔体充分孕育，30min内浇铸至水冷的模具中，通过热电偶读取冷却 速率为130K/s。
步骤2-3：开模，取出Mg-Gd-Al-Ni合金。
Gd原子主要和Al原子形成Al 2Gd相，因此，在平衡凝固条件下，3.43wt.％的Al能将10wt.％的Gd完全置换出来，在实际的操作过程中，无法达到理想的平衡凝固条件，因此当Al含量在0～3.43wt.％的范围内时，热导率能够达到一个峰值，此时Gd元素在这种高导热镁合金Mg-Gd-Al-Ni中会分别以固溶原子态、Mg-Gd相(Mg 5Gd相)、Al-Gd相(Al 2Gd相)存在。
取Al的质量分数分别为0，0.2％，0.5％，1％，1.5％，2％，2.5％，3％，3.43％制备出拥有不同Al含量的Mg-10Gd-xAl-0.5Ni铸锭。
表8示出本实施例中高导热镁合金Mg-Gd-Al-Ni(Mg-10Gd-xAl-0.5Ni)的热导率以及热导率提升幅度随合金中Al加入量的变化。Mg-10Gd-0.5Ni在常温下的热导率为50.1W/(m·K)，以该数值的热导率提升幅度为0，计算其他引入Al后获得的
Mg-10Gd-xAl-0.5Ni合金的热导率提升幅度。
表8.
Figure PCTCN2022078353-appb-000009
添加Al至Mg-10Gd合金中，热导率可提升137％，最高热导率可达118.5W/(m·K)，远高于CN107604228B中公开的镁合金AZ91D的热导率53W/(m·K)和部分低固溶度的镁合金Mg-4Ce-2Al-0.5Mn热导率105W/(m·K)。
实施例4
在本实施例中选择Gd和Y共同作为在Mg基体中含有高固溶度的稀土元素来制备高导热镁合金Mg-Gd-Y-Al-Ni，具体的制备过程如下：
步骤1：制备Mg-Gd-Y合金，其中，Gd的质量分数为10％，Y的质量分数为3％。具体通过以下步骤获得：
步骤1-1：首先按照合金成分及化学计量比，考虑Gd和Y在熔炼过程中的烧损，将所需的原料，包括工业纯镁锭和Mg-Gd中间合金，Mg-Y中间合金去除氧化层并放入烘箱于200℃预热。将刷好脱模剂的坩埚一并放入烘箱烘干；
步骤1-2：将工业纯镁锭放入坩埚中，在通有SF 6和CO 2的混合气体(体积比为 60：1)的保护气氛中升温至760℃，待纯镁熔化后，加入Mg-Gd中间合金和Mg-Y中间合金。充分搅拌15min，静置30min，扒渣，浇铸至模具中，待熔融的金属液凝固完全后，取出铸锭，制备出相应的Mg-Gd-Y合金。
步骤2：制备Mg-Gd-Y-Al-Ni，其中，考虑到加Al过程中的温度更高，在Mg-Gd-Y熔融金属液的制备过程中，Gd和Y的烧损相比步骤1略高，确保制备Mg-Gd-Y-Al-Ni的Gd的质量分数为10％，Y的质量分数为3％即可，其余步骤同步骤1。具体通过以下步骤获得：
步骤2-1：通过步骤A1和B1获得熔融的Mg-Gd-Y金属液后，将质量分数为0.2的Ni以Mg-Ni中间合金的方式添加至熔体中，充分搅拌15min，温度升温至800℃；
步骤2-2：向熔体内将Al以纯Al的方式添加至Mg-Gd-Y合金熔体中充分搅拌15min，对熔体进行电磁震荡处理，使微量的Ni与Al快速形成Al-Ni孕育剂，静置25min，使熔体充分孕育，30min内浇铸至水冷的模具中，通过热电偶读取冷却速率为180K/s。
步骤2-3：开模，取出Mg-Gd-Y-Al-Ni合金。
步骤2：制备Mg-Gd-Y-Al-Ni合金。
如上所述，在平衡凝固条件下，3.43wt.％的Al能将10wt.％的Gd完全置换出来，1.82wt.％的Al能将3wt.％的Y完全置换出来。在实际的操作过程中，无法达到理想的平衡凝固条件，因此当Al含量在0～5.25wt.％的范围内时，热导率能够达到一个峰值。
取Al的质量分数分别为0，0.2％，0.5％，1％，2％，3％，4％，4.5％，5％，5.25％制备出拥有不同Al含量的Mg-10Gd-3Y-xAl-0.2Ni铸锭。
表9示出本实施例中高导热镁合金Mg-10Gd-3Y-xAl-0.2Ni的热导率以及热导率提升幅度和固溶的Gd、Y原子含量随合金中Al加入量的变化。Mg-10Gd-3Y-0.2Ni在常温下的热导率为34.4W/(m·K)，以该数值的热导率提升幅度为0，计算其他引入Al后获得的Mg-10Gd-3Y-xAl-0.2Ni合金的热导率提升幅度。
表9.
Figure PCTCN2022078353-appb-000010
添加Al至Mg-10Gd-3Y合金中，热导率可提升216％，最高热导率可达108.6W/(m·K)，说明即使是多种RE混合的镁合金，添加Al也能大幅度提升热导率。
本发明对镁合金中添加的含有高固溶度的稀土元素的种类不作限制，只要能实现对具有这种稀土元素的镁合金的热导率的大幅提升以及满足本发明期望的性能如热导率即可。
虽然通过参照本发明的某些优选实施方式，已经对本发明进行了图示和描述，但本领域的普通技术人员应该明白，以上内容是结合具体的实施方式对本发明所作的进一步详细说明，不能认定本发明的具体实施只局限于这些说明。本领域技术人员可以在形式上和细节上对其作各种改变，包括做出若干简单推演或替换，而不偏离本发明的精神和范围。

Claims (10)

  1. 一种含有高固溶度稀土元素的高导热镁合金，其特征在于，包括：
    RE，RE在所述高导热镁合金中的质量分数为4％～16％，且在镁中的极限固溶度≥0.8at.％；
    Al，Al与RE的原子比在0.3～4；
    余量为Mg及不可避免的杂质；
    所述高导热镁合金的微观组织包括第一相和第二相，所述第一相包括Mg基体和固溶在镁基体中的RE，所述固溶在镁基体中的RE在所述第一相中的原子数百分比为0.05％～0.2％，所述第二相包括Mg-RE相和Al-RE相；
    所述高导热镁合金在常温下的热导率≥100W/(m·K)。
  2. 根据权利要求1所述的高导热镁合金，其特征在于，所述第二相的晶体颗粒尺寸为5～10μm。
  3. 根据权利要求1所述的高导热镁合金，其特征在于，所述RE包括Sm，Y，Gd，Dy和Er中的至少一种。
  4. 根据权利要求1所述的高导热镁合金，其特征在于，还包括Ni，Ni在所述高导热镁合金中的质量分数为0.05％～0.3％；所述微观组织还包括Al-Ni颗粒相。
  5. 一种高导热镁合金的制备方法，其特征在于，包括：
    S1：在780～820℃和保护气氛中，向熔融的Mg-RE合金中加入Al，搅拌、静置，得到熔融的高导热镁合金；
    S2：将所述熔融的高导热镁合金转移至模具中，以100～200K/s的冷却速度冷至室温，获得所述高导热镁合金；
    所述高导热镁合金的微观组织包括第一相和第二相，所述第一相包括Mg基体和固溶在镁基体中的RE，所述固溶在镁基体中的RE在所述第一相中的原子数百分比为0.05～0.2％，所述第二相包括Mg-RE相和Al-RE相。
  6. 根据权利要求5所述的制备方法，其特征在于，在所述S1中，还要向所述熔融的Mg-RE合金中加入Ni。
  7. 根据权利要求5或6所述的制备方法，其特征在于，Al的加入形式包括纯Al、Mg-Al合金或Al-RE合金中的至少一种。
  8. 根据权利要求6所述的制备方法，其特征在于，Ni的加入形式为Mg-Ni合金。
  9. 根据权利要求5或6所述的制备方法，其特征在于，控制所述搅拌的时间10～15min，控制所述静置的时间15～30min。
  10. 根据权利要求5或6所述的制备方法，其特征在于，所述制备方法满足下述工艺中的至少一项：
    采用水冷对所述模具进行冷却；
    所述保护气氛为SF 6和CO 2。
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