CN113846252A - Preparation method of high-thermal-conductivity AlSi alloy - Google Patents
Preparation method of high-thermal-conductivity AlSi alloy Download PDFInfo
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Abstract
The invention relates to a preparation method of high-thermal-conductivity AlSi alloy, which comprises the following steps: preparing raw materials according to the alloy component proportion; melting: placing a pure aluminum ingot in a smelting furnace, heating and melting to form aluminum liquid; transferring the molten aluminum in the smelting furnace into an alloy furnace, heating to 760-780 ℃, and adding Al-50Si intermediate alloy; uniformly stirring for 10-30min after complete melting, keeping the temperature unchanged during stirring, and performing modification treatment: skimming dross on the surface of the aluminum liquid, raising the temperature of the aluminum liquid to 770 ℃, and adding an Al-10Sr intermediate alloy modifier; thinning treatment: controlling the temperature of the aluminum liquid in the alloy furnace at 770 ℃, and adding Al-3Sc master alloy; and (3) heat treatment: gradually raising the temperature to 240-. The invention prepares the aluminum-silicon alloy with excellent comprehensive performance and high thermal conductivity by carrying out process integration innovation and improvement on the aspects of melt refining, modification and refinement, artificial aging heat treatment and the like, and has important popularization and application values.
Description
Technical Field
The invention relates to a preparation method of a high-thermal-conductivity AlSi alloy, and relates to the technical field of material manufacturing.
Background
The aluminum alloy has the characteristics of small density, high specific strength, good electric/thermal conductivity, good processing formability and the like, and is widely applied to the fields of automobiles, electronics, communication and the like. High thermal conductivity is a particular requirement for aluminum alloys in many heat exchange applications. Generally, the thermal conductivity of pure aluminum at room temperature is high, about 238w/(mK), and the thermal conductivity of wrought aluminum alloys such as 6063 is also as high as 209 w/(mK), but as the alloy elements increase, the thermal conductivity of the aluminum alloy gradually decreases, and the influence of different elements on the thermal conductivity of the alloy is greatly different. The physical nature of metallic materials to conduct heat and electricity is that free electron motion plays a dominant role. Theoretically, the more complete the crystal of the metal, the less the lattice distortion, grain boundary, and other defects caused by the heterogeneous atoms, and the like, the smaller the resistance to electron movement, and the better the conductivity. The thermal conductivity of aluminum alloys is related to the degree of lattice distortion, defects, impurities, phase composition and distribution in the structure. In the alloy, when the elements are added in a solid solution mode, crystal lattices can be distorted, when the alloy elements exist in a second phase mode, a new interface can be introduced, in both cases, the scattering of electrons is increased, the mean free path of the electrons is reduced, and the heat conduction and electric conduction capability of the aluminum alloy is reduced. Although the addition of alloy elements all reduces the thermal conductivity of pure Al, the influence of different elements on the thermal conductivity of the alloy is greatly different, for example, the influence of a small amount of Sb, Cd, Bi and other elements on the thermal conductivity of pure Al is not obvious, the addition of Cr, Li, Mn and other elements significantly reduces the thermal conductivity of pure Al, and the influence of common alloy elements, such as Si, Mg, Cu and the like, is in the middle.
The existing aluminum alloy heat-conducting property research mainly focuses on the aspects of wrought aluminum alloy, high-silicon aluminum, aluminum-silicon carbide, aluminum-diamond, aluminum-graphite flake/carbon nano tube and other emerging composite materials. However, for products with complex structures and uneven wall thicknesses in the fields of automobiles, electronics, communications, and the like, cast aluminum alloys are generally used. However, in the case of cast aluminum alloys, it is generally necessary to add a large amount of alloying elements in order to ensure the mold filling properties, mechanical properties, etc. of the alloys. Compared with pure Al and wrought aluminum alloy, the heat conductivity is reduced more. Therefore, there is an urgent need to develop a cast aluminum alloy material which can realize batch die-casting and molding and has excellent mechanical properties to meet the increasingly demanding requirements of industries such as automobiles, electronic communication and the like.
The cast aluminum alloy is mainly aluminum-silicon alloy, wherein silicon can improve the fluidity of the alloy and is beneficial to the molding of die-cast products with complex shapes, but the mechanical property of the alloy is reduced along with the increase of the content of the silicon. This is mainly because the solid solubility of silicon in the α -Al matrix increases, and with further increase in silicon content, the amount of eutectic silicon in the structure increases and the size becomes coarse; the primary crystal Si of the alloy which is not subjected to modification exists in a plate shape, and a matrix is seriously cracked, so that the plasticity and toughness of the alloy are obviously reduced; the combination between the plate and the plate is very weak, so that the alloy has poor processing performance and loses use value. In order to maintain the inherent advantages of the Al-Si alloy and greatly improve the strength performance, the plastic toughness and the heat-conducting performance of the Al-Si alloy, the addition of alloying elements, a modification and refinement treatment process and a heat treatment process must be accurately controlled.
Currently, the difficulty in developing high thermal conductivity AlSi aluminum alloys is that the alloys must simultaneously satisfy various requirements for fluidity, machine formability, mechanical properties, and thermal conductivity. At present, the conventional production is adopted to improve the heat-conducting property of the alloy mainly by reducing the content of a small amount of silicon and sacrificing a part of fluidity property, such as typical A356 and AlSi8 aluminum alloy; the Al-10Sr intermediate alloy can also be adopted to carry out modification treatment on the eutectic silicon so as to improve the heat conduction and mechanical properties of the alloy; or Al-B alloy is added to purify impurity elements such as Ti, V and the like, thereby improving the heat-conducting property of the alloy. However, these measures can only make the thermal conductivity of the aluminum-silicon alloy reach about 175W/(m.k), and it is difficult to meet the requirement of high thermal conductivity that the thermal conductivity reaches over 195W/(m.k); in addition, because B element is easy to oxidize, oxide impurities and specific gravity segregation are generated, the heat conductivity of the product cannot be stably maintained, and the precision die-casting molding of the product is not facilitated.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a preparation method of high-thermal-conductivity AlSi alloy, and the technical scheme of the invention is as follows:
the preparation method of the high-thermal-conductivity AlSi alloy comprises the following steps
(1) Preparing materials: preparing raw materials according to the alloy component proportion, wherein the raw materials are Al99.85 pure aluminum ingot, Al-50Si, Al-10Sr and Al-3Sc intermediate alloy;
(2) melting: placing a pure aluminum ingot in a smelting furnace, heating and melting to form aluminum liquid; transferring the molten aluminum in the smelting furnace into an alloy furnace, heating to 760-780 ℃, and adding Al-50Si intermediate alloy; uniformly stirring for 10-30min after complete melting, and keeping the temperature unchanged during stirring;
(3) deslagging and degassing for the first time;
(4) modification treatment: removing dross on the surface of the aluminum liquid, raising the temperature of the aluminum liquid to 770-800 ℃, adding an Al-10Sr intermediate alloy modifier, and uniformly stirring for 20-30 min;
(5) deslagging and degassing for the second time;
(6) standing treatment: skimming dross on the surface of the aluminum liquid, closing the furnace door for standing treatment, and controlling the standing time to be 20-40 min;
(7) thinning treatment: controlling the temperature of the aluminum liquid in the alloy furnace at 770-800 ℃, adding Al-3Sc intermediate alloy, and uniformly stirring for 20-30 min;
(8) stirring: controlling the temperature of the aluminum liquid in the alloy furnace at 750-780 ℃, and fully stirring the aluminum liquid by using a mechanical circulating pump for 10-15 min;
(9) GBF online degassing treatment: refining by adopting a GBF online degassing device on line, and performing two-stage filtration on the molten aluminum through a two-stage filter box;
(10) casting: introducing the filtered aluminum liquid into a distributor, controlling the temperature of the aluminum liquid entering the distributor to be 680-710 ℃, then pouring the aluminum liquid into a crystallization mold of a casting machine, and solidifying to obtain an AlSi alloy ingot;
(11) pressure casting: remelting the AlSi alloy ingot obtained in the step (10), extracting air in a die by using single-channel vacuum-pumping equipment, and carrying out die-casting forming on a high-pressure die-casting machine with the vacuum degree numerical value controlled to be lower than 50mbar to obtain an AlSi alloy die-casting piece;
(12) and (3) heat treatment: and (4) placing the AlSi alloy die casting obtained in the step (11) into a heat treatment furnace for artificial aging heat treatment.
In the step (1), the components comprise, by mass, 9.5-12.5% of Si, less than or equal to 0.03% of Cu, less than or equal to 0.02% of Mn, less than or equal to 0.1% of Mg, 0.5-0.7% of Fe, less than or equal to 0.05% of Zn, less than or equal to 20ppm of Cr, less than or equal to 20ppm of V, less than or equal to 25ppm of Ti, 0.01-0.03% of Sr, 0.1-0.3% of Sc, and the balance of Al and inevitable impurity elements.
In the step (3), the first deslagging and degassing specific steps are as follows: controlling the temperature of the aluminum liquid in the alloy furnace at 750-770 ℃, uniformly discharging a sodium-free refining agent and argon into the aluminum liquid by using an automatic refiner, wherein the purity of the argon is 99.999%, the pressure of the argon is 0.2-0.3MPa, and the duration is 15-20 min; in the step (5), the second deslagging and degassing specifically comprises the following steps: controlling the temperature of the aluminum liquid in the alloy furnace at 770-800 ℃, and uniformly discharging a sodium-free refining agent and argon into the aluminum liquid by using an automatic refiner for 15-20 min.
The specific operation process of the artificial aging heat treatment in the step (12) is as follows: gradually raising the temperature to 240-.
And (4) adding 2.5-4 kg of Al-10Sr master alloy modifier per ton of molten aluminum.
And (3) adding Al-3Sc master alloy refiner in the step (7) in an amount of 50-100 kg per ton of molten aluminum.
In the step (9), two-stage foam ceramic plates of 40ppi foam ceramic plates and 50ppi foam ceramic plates are adopted to carry out two-stage filtration on the aluminum liquid.
The invention has the advantages that:
(1) according to the preparation method of the high-thermal-conductivity die-casting aluminum-silicon alloy, the eutectic aluminum-silicon alloy is prepared by using a high-purity aluminum ingot, so that impurity components in the alloy are reduced as much as possible; in the smelting process, two refining processes of argon and solvent are adopted to fully remove gas and slag; the Sr + Sc synergistic modification refining treatment process is adopted to reduce the eutectic size and refine the aluminum matrix grain structure; performing two-stage filtration on the aluminum liquid by adopting a 40ppi/50ppi foamed ceramic plate to further remove impurities in the melt; the alloy is formed by high-pressure high-vacuum die casting, so that the structural compactness and uniformity of the alloy are effectively improved; and the aging process of 'double-stage temperature change' is adopted to inhibit the coarsening of the second phase and simultaneously ensure that the strengthening phase is fully dispersed and uniformly precipitated. Finally obtaining the aluminum-silicon alloy die-casting product with better heat-conducting property, mechanical property and die-casting property.
(2) The preparation method of the high-thermal-conductivity die-casting aluminum-silicon alloy provided by the invention does not change the conventional aluminum alloy die-casting production process flow, equipment and mould, only carries out process innovation on the aspects of melt refining, modification and product heat treatment, and the obtained aluminum-silicon alloy vacuum die-casting product has compact structure and excellent comprehensive performance, wherein the thermal conductivity reaches more than 195w/(m.K), the tensile strength reaches more than 200MPa, the yield strength reaches more than 90MPa, and the elongation after fracture exceeds 6.5%. The main components are the same as those of the die casting process, and the heat conductivity of the AlSi alloy which is not treated by the refining, modification and heat treatment processes of the invention only reaches about 160 w/(m.K). In contrast, the thermal conductivity of the die-cast AlSi alloy obtained by the present invention is improved by 21.9%.
In conclusion, the invention prepares the aluminum-silicon alloy with excellent comprehensive performance and high thermal conductivity by carrying out process integration innovation and improvement on the aspects of melt refining, modification, product heat treatment and the like, and has important popularization and application values.
Drawings
FIG. 1 is a schematic view of an aluminum-silicon alloy die casting in the as-die-cast OM state of the invention.
FIG. 2 is a schematic view of the invention in an aged OM state for an aluminum-silicon alloy die casting.
Fig. 3 is a schematic view of the aluminum-silicon alloy die casting in the as-die-cast state OM of the invention.
FIG. 4 is a schematic representation of the state OM of the aluminum-silicon alloy die casting of the present invention.
Detailed Description
The invention will be further described with reference to specific embodiments, and the advantages and features of the invention will become apparent as the description proceeds. These examples are illustrative only and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.
Example 1: a preparation method of high-thermal-conductivity AlSi alloy comprises the following steps:
(1) preparing materials: preparing raw materials according to the alloy component proportion, wherein the raw materials are Al99.85 pure aluminum ingot, Al-50Si, Al-10Sr and Al-3Sc intermediate alloy;
(2) melting: placing a pure aluminum ingot in a smelting furnace, heating and melting to form aluminum liquid; transferring the aluminum liquid in the smelting furnace into an alloy furnace, raising the temperature to 760 ℃, and adding Al-50Si intermediate alloy; uniformly stirring for 10min after complete melting, and keeping the temperature unchanged in the stirring process;
(3) deslagging and degassing for the first time;
(4) modification treatment: skimming dross on the surface of the aluminum liquid, raising the temperature of the aluminum liquid to 770 ℃, adding an Al-10Sr intermediate alloy modifier, and uniformly stirring for 20 min;
(5) deslagging and degassing for the second time;
(6) standing treatment: skimming dross on the surface of the aluminum liquid, closing a furnace door for standing treatment, and controlling the standing time to be 20 min;
(7) thinning treatment: controlling the temperature of the aluminum liquid in the alloy furnace at 770 ℃, adding Al-3Sc master alloy, and uniformly stirring for 20 min;
(8) stirring: controlling the temperature of the aluminum liquid in the alloy furnace at 750 ℃, and fully stirring the aluminum liquid by using a mechanical circulating pump for 10 min;
(9) GBF online degassing treatment: refining by adopting a GBF online degassing device on line, and performing two-stage filtration on the molten aluminum through a two-stage filter box;
(10) casting: introducing the filtered aluminum liquid into a distributor, controlling the temperature of the aluminum liquid entering the distributor to be 680 ℃, then pouring the aluminum liquid into a crystallization mold of a casting machine, and solidifying to obtain an AlSi alloy ingot;
(11) pressure casting: remelting the AlSi alloy ingot obtained in the step (10), extracting air in a die by using single-channel vacuum-pumping equipment, and carrying out die-casting forming on a high-pressure die-casting machine with the vacuum degree value of 42mbar to obtain an AlSi alloy die-casting piece;
(12) and (3) heat treatment: and (4) placing the AlSi alloy die casting obtained in the step (11) into a heat treatment furnace for artificial aging heat treatment.
In the step (1), the components comprise, by mass, 9.5% of Si, 0.03% of Cu, 0.02% of Mn, 0.1% of Mg, 0.5% of Fe, 0.05% of Zn, 20ppm of Cr, 20ppm of V, 25ppm of Ti, 0.01% of Sr, 0.1% of Sc, and the balance of Al and inevitable impurity elements.
In the step (3), the first deslagging and degassing specific steps are as follows: controlling the temperature of the aluminum liquid in the alloy furnace at 750 ℃, uniformly discharging a sodium-free refining agent and argon into the aluminum liquid by using an automatic refiner, wherein the purity of the argon is 99.999 percent, the pressure of the argon is 0.2MPa, and the duration is 15 min; in the step (5), the second deslagging and degassing specifically comprises the following steps: controlling the temperature of the aluminum liquid in the alloy furnace at 770 ℃, and uniformly discharging a sodium-free refining agent and high-purity argon into the aluminum liquid for 15min by using an automatic refiner.
The specific operation process of the artificial aging heat treatment in the step (12) is as follows: gradually raising the temperature to 240 ℃ within 1 hour, preserving the heat for 0.5 hour, then gradually raising the temperature to 335 ℃ within 1 hour, preserving the heat for 2 hours, and then cooling to room temperature along with the furnace.
The amount of the Al-10Sr master alloy modifier added in the step (4) is 2.5 kg/ton of molten aluminum.
The amount of the Al-3Sc master alloy refiner added in the step (7) is 50 kg/ton of molten aluminum.
In the step (9), two-stage foam ceramic plates of 40ppi foam ceramic plates and 50ppi foam ceramic plates are adopted to carry out two-stage filtration on the aluminum liquid.
Example 2: a preparation method of high-thermal-conductivity AlSi alloy comprises the following steps:
(1) preparing materials: preparing raw materials according to the alloy component proportion, wherein the raw materials are Al99.85 pure aluminum ingot, Al-50Si, Al-10Sr and Al-3Sc intermediate alloy;
(2) melting: placing a pure aluminum ingot in a smelting furnace, heating and melting to form aluminum liquid; transferring the aluminum liquid in the smelting furnace into an alloy furnace, raising the temperature to 770 ℃, and adding Al-50Si intermediate alloy; uniformly stirring for 20min after complete melting, and keeping the temperature unchanged in the stirring process;
(3) deslagging and degassing for the first time;
(4) modification treatment: removing dross on the surface of the aluminum liquid, raising the temperature of the aluminum liquid to 780 ℃, adding an Al-10Sr intermediate alloy modifier, and uniformly stirring for 25 min;
(5) deslagging and degassing for the second time;
(6) standing treatment: skimming dross on the surface of the aluminum liquid, closing a furnace door for standing treatment, and controlling the standing time to be 30 min;
(7) thinning treatment: controlling the temperature of the aluminum liquid in the alloy furnace at 790 ℃, adding Al-3Sc master alloy, and uniformly stirring for 25 min;
(8) stirring: controlling the temperature of the aluminum liquid in the alloy furnace at 760 ℃, and fully stirring the aluminum liquid by using a mechanical circulating pump for 12 min;
(9) GBF online degassing treatment: refining by adopting a GBF online degassing device on line, and performing two-stage filtration on the molten aluminum through a two-stage filter box;
(10) casting: introducing the filtered aluminum liquid into a distributor, controlling the temperature of the aluminum liquid entering the distributor to be 700 ℃, then pouring the aluminum liquid into a crystallization mold of a casting machine, and solidifying to obtain an AlSi alloy ingot;
(11) pressure casting: remelting the AlSi alloy ingot obtained in the step (10), and performing die-casting forming on a high-pressure die-casting machine with a vacuum degree value of 40mbar by using single-channel vacuum-pumping equipment to extract air in a die to obtain an AlSi alloy die-casting piece;
(12) and (3) heat treatment: and (4) placing the AlSi alloy die casting obtained in the step (11) into a heat treatment furnace for artificial aging heat treatment.
In the step (1), the components comprise, by mass, 11% of Si, 0.02% of Cu, 0.01% of Mn, 0.05% of Mg, 0.6% of Fe, 0.04% of Zn, 10ppm of Cr, 10ppm of V, 20ppm of Ti, 0.02% of Sr, 0.2% of Sc, and the balance of Al and inevitable impurity elements.
In the step (3), the first deslagging and degassing specific steps are as follows: controlling the temperature of aluminum liquid in an alloy furnace at 760 ℃, uniformly discharging a sodium-free refining agent and argon into the aluminum liquid by using an automatic refiner, wherein the purity of the argon is 99.999 percent, the pressure of the argon is 0.25MPa, and the duration is 18 min; in the step (5), the second deslagging and degassing specifically comprises the following steps: controlling the temperature of the aluminum liquid in the alloy furnace at 790 ℃, and uniformly discharging a sodium-free refining agent and high-purity argon into the aluminum liquid for 18min by using an automatic refiner.
The specific operation process of the artificial aging heat treatment in the step (12) is as follows: gradually raising the temperature to 250 ℃ within 1 hour, preserving the heat for 0.5 hour, then gradually raising the temperature to 340 ℃ within 1 hour, preserving the heat for 2 hours, and then cooling to the room temperature along with the furnace.
The amount of the Al-10Sr master alloy modifier added in the step (4) is 3.5 kg/ton of molten aluminum.
And (3) adding 80kg of Al-3Sc master alloy refiner in the step (7) per ton of molten aluminum.
In the step (9), two-stage foam ceramic plates of 40ppi foam ceramic plates and 50ppi foam ceramic plates are adopted to carry out two-stage filtration on the aluminum liquid.
Example 3: a preparation method of high-thermal-conductivity AlSi alloy comprises the following steps:
(1) preparing materials: preparing raw materials according to the alloy component proportion, wherein the raw materials are Al99.85 pure aluminum ingot, Al-50Si, Al-10Sr and Al-3Sc intermediate alloy;
(2) melting: placing a pure aluminum ingot in a smelting furnace, heating and melting to form aluminum liquid; transferring the molten aluminum in the smelting furnace into an alloy furnace, raising the temperature to 780 ℃, and adding Al-50Si intermediate alloy; uniformly stirring for 30min after complete melting, and keeping the temperature unchanged in the stirring process;
(3) deslagging and degassing for the first time;
(4) modification treatment: removing dross on the surface of the aluminum liquid, raising the temperature of the aluminum liquid to 800 ℃, adding an Al-10Sr intermediate alloy modifier, and uniformly stirring for 30 min;
(5) deslagging and degassing for the second time;
(6) standing treatment: skimming dross on the surface of the aluminum liquid, closing a furnace door for standing treatment, and controlling the standing time to be 40 min;
(7) thinning treatment: controlling the temperature of the aluminum liquid in the alloy furnace at 800 ℃, adding Al-3Sc master alloy, and uniformly stirring for 30 min;
(8) stirring: controlling the temperature of the aluminum liquid in the alloy furnace at 780 ℃, and fully stirring the aluminum liquid by using a mechanical circulating pump for 15 min;
(9) GBF online degassing treatment: refining by adopting a GBF online degassing device on line, and performing two-stage filtration on the molten aluminum through a two-stage filter box;
(10) casting: introducing the filtered aluminum liquid into a distributor, controlling the temperature of the aluminum liquid entering the distributor to be 710 ℃, then pouring the aluminum liquid into a crystallization mold of a casting machine, and solidifying to obtain an AlSi alloy ingot;
(11) pressure casting: remelting the AlSi alloy ingot obtained in the step (10), extracting air in a die by using single-channel vacuum-pumping equipment, and carrying out die-casting forming on a high-pressure die-casting machine with the vacuum degree value of 45mbar to obtain an AlSi alloy die-casting piece;
(12) and (3) heat treatment: and (4) placing the AlSi alloy die casting obtained in the step (11) into a heat treatment furnace for artificial aging heat treatment.
In the step (1), the components comprise, by mass, 12.5% of Si, 0.01% of Cu, 0.005% of Mn, 0.05% of Mg, 0.7% of Fe, 0.03% of Zn, 5ppm of Cr, 15ppm of V, 15ppm of Ti, 0.03% of Sr, 0.3% of Sc, and the balance of Al and inevitable impurity elements.
In the step (3), the first deslagging and degassing specific steps are as follows: controlling the temperature of the aluminum liquid in the alloy furnace at 770 ℃, uniformly discharging a sodium-free refining agent and argon into the aluminum liquid by using an automatic refiner, wherein the purity of the argon is 99.999 percent, the pressure of the argon is 0.3MPa, and the duration is 20 min; in the step (5), the second deslagging and degassing specifically comprises the following steps: controlling the temperature of the aluminum liquid in the alloy furnace at 800 ℃, and uniformly discharging a sodium-free refining agent and high-purity argon into the aluminum liquid for 20min by using an automatic refiner.
The specific operation process of the artificial aging heat treatment in the step (12) is as follows: gradually raising the temperature to 255 ℃ within 1 hour, preserving the heat for 0.5 hour, then gradually raising the temperature to 350 ℃ within 1 hour, preserving the heat for 2 hours, and then cooling to the room temperature along with the furnace.
The amount of the Al-10Sr master alloy modifier added in the step (4) is 4 kg/ton of molten aluminum.
The amount of the Al-3Sc master alloy refiner added in the step (7) is 100 kg/ton of molten aluminum.
In the step (9), two-stage foam ceramic plates of 40ppi foam ceramic plates and 50ppi foam ceramic plates are adopted to carry out two-stage filtration on the aluminum liquid.
The analysis in conjunction with the attached figures can learn that: the samples were taken for texture analysis in the as-cast and aged states, and it can be seen from FIGS. 1 and 2 that the modification of trace elements reduces the average diameter of the eutectic silicon particles, thereby reducing the scattering effect on electrons
As can be seen from fig. 3 and 4, the rational heat treatment further reduces the number of solid solution atoms in the α -Al matrix structure, reduces the degree of lattice distortion, and relieves the casting stress. Meanwhile, free electrons in metal are used as a heat conduction carrier, eutectic silicon in the alloy becomes fine and round through solid solution and aging treatment, meanwhile, due to precipitation, the solid solubility and the vacancy of solute in the matrix are reduced, the resistance of free electron movement is reduced, heat transfer taking free electron migration as a leading factor is facilitated, and the heat conduction performance of the alloy is improved at the moment.
Fig. 1 to 4 show that the aluminum-silicon alloy prepared by the invention has good structural uniformity and compact structure, and shows that the fluidity and the die-casting forming performance of the alloy meet the processing requirements.
The thermal conductivity of the aged alloy is measured by a thermal conductivity meter and is 196 w/(m.K); the mechanical properties of the aged alloy were determined by room temperature tensile test with the results: the tensile strength is 216MPa, the yield strength reaches 110MPa, and the elongation after fracture exceeds 12 percent. The process technology of the invention shows that the AlSi alloy die casting achieves high heat conduction and simultaneously achieves good matching of comprehensive mechanical properties.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (7)
1. The preparation method of the high-thermal-conductivity AlSi alloy is characterized by comprising the following steps
(1) Preparing materials: preparing raw materials according to the alloy component proportion, wherein the raw materials are Al99.85 pure aluminum ingot, Al-50Si, Al-10Sr and Al-3Sc intermediate alloy;
(2) melting: placing a pure aluminum ingot in a smelting furnace, heating and melting to form aluminum liquid; transferring the molten aluminum in the smelting furnace into an alloy furnace, heating to 760-780 ℃, and adding Al-50Si intermediate alloy; uniformly stirring for 10-30min after complete melting, and keeping the temperature unchanged during stirring;
(3) deslagging and degassing for the first time;
(4) modification treatment: removing dross on the surface of the aluminum liquid, raising the temperature of the aluminum liquid to 770-800 ℃, adding an Al-10Sr intermediate alloy modifier, and uniformly stirring for 20-30 min;
(5) deslagging and degassing for the second time;
(6) standing treatment: skimming dross on the surface of the aluminum liquid, closing the furnace door for standing treatment, and controlling the standing time to be 20-40 min;
(7) thinning treatment: controlling the temperature of the aluminum liquid in the alloy furnace at 770-800 ℃, adding Al-3Sc intermediate alloy, and uniformly stirring for 20-30 min;
(8) stirring: controlling the temperature of the aluminum liquid in the alloy furnace at 750-780 ℃, and fully stirring the aluminum liquid by using a mechanical circulating pump for 10-15 min;
(9) GBF online degassing treatment: refining by adopting a GBF online degassing device on line, and performing two-stage filtration on the molten aluminum through a two-stage filter box;
(10) casting: introducing the filtered aluminum liquid into a distributor, controlling the temperature of the aluminum liquid entering the distributor to be 680-710 ℃, then pouring the aluminum liquid into a crystallization mold of a casting machine, and solidifying to obtain an AlSi alloy ingot;
(11) pressure casting: remelting the AlSi alloy ingot obtained in the step (10), extracting air in a die by using single-channel vacuum-pumping equipment, and carrying out die-casting forming on a high-pressure die-casting machine with the vacuum degree numerical value controlled to be lower than 50mbar to obtain an AlSi alloy die-casting piece;
(12) and (3) heat treatment: and (4) placing the AlSi alloy die casting obtained in the step (11) into a heat treatment furnace for artificial aging heat treatment.
2. The method for preparing AlSi alloy with high thermal conductivity according to claim 1, wherein in step (1), the components comprise, by mass, 9.5% -12.5% of Si, 0.03% or less of Cu, 0.02% or less of Mn, 0.1% or less of Mg, 0.5% -0.7% of Fe, 0.05% or less of Zn, 20ppm or less of Cr, 20ppm or less of V, 25ppm or less of Ti, 0.01% -0.03% of Sr, 0.1% -0.3% of Sc, and the balance of Al and inevitable impurity elements.
3. The preparation method of the AlSi alloy with high thermal conductivity according to claim 1 or 2, characterized in that in the step (3), the first deslagging and degassing steps are as follows: controlling the temperature of the aluminum liquid in the alloy furnace at 750-770 ℃, uniformly discharging a sodium-free refining agent and argon into the aluminum liquid by using an automatic refiner, wherein the purity of the argon is 99.999%, the pressure of the argon is 0.2-0.3MPa, and the duration is 15-20 min; in the step (5), the second deslagging and degassing specifically comprises the following steps: controlling the temperature of the aluminum liquid in the alloy furnace at 770-800 ℃, and uniformly discharging a sodium-free refining agent and argon into the aluminum liquid by using an automatic refiner for 15-20 min.
4. The preparation method of the AlSi alloy with high thermal conductivity according to claim 1 or 2, wherein the specific operation process of the artificial aging heat treatment in the step (12) is as follows: gradually raising the temperature to 240-.
5. The preparation method of the AlSi alloy with high thermal conductivity according to claim 1 or 2 or the claim, wherein the amount of the Al-10Sr intermediate alloy modifier added in the step (4) is 2.5-4 kg/ton of molten aluminum.
6. The preparation method of the AlSi alloy with high thermal conductivity according to claim 1 or 2, wherein the Al-3Sc master alloy refiner added in the step (7) accounts for 50-100 kg/ton of molten aluminum.
7. The preparation method of the AlSi alloy with high thermal conductivity according to claim 1 or 2, characterized in that in the step (9), two-stage filtration of aluminum liquid is performed by using two-stage foam ceramic plates of 40ppi foam ceramic plates and 50ppi foam ceramic plates.
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