High thermal conductive cast aluminum alloy and preparation method thereof

Abstract

The application discloses a high-thermal-conductivity cast aluminum alloy and a preparation method, and relates to the technical field of aluminum alloys. The mass percentage of each component of the aluminum alloy is as follows: Fe: 1.6-2.5%; B: 0.005-0.02%; Sc: 0.01-0.05%; the balance is Al and inevitable impurity elements, and the total amount of the inevitable impurity elements is not more than 0.3%. The application has the following advantages: (1) the flowability and castability of the aluminum alloy are ensured by designing the content of Fe; (2) the thermal conductivity of the aluminum alloy is improved by adding Sc2O3 and mixed halide salt to improve the structure of the aluminum alloy; (3) the thermal conductivity of the aluminum alloy is improved by removing part of impurity elements and improving the morphology of the iron-rich phase through boronization treatment. In conclusion, the iron-rich phase is refined, and the number of primary iron-rich phases is reduced, so that the thermal conductivity of the aluminum alloy castings is improved.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy technology, specifically relating to a high thermal conductivity cast aluminum alloy and its preparation method. Background Technology

[0002] Aluminum alloys are widely used in heat dissipation equipment such as electronic components, computer heat sinks, and 5G base stations due to their advantages such as low density, excellent electrical and thermal conductivity, good formability, and low cost. Commonly used thermally conductive cast aluminum alloys are mainly aluminum-silicon alloys; however, coarse α-Al dendrites and a large amount of brittle Al-Si eutectic structure significantly reduce the alloy's strength and plasticity. Simultaneously, the presence of eutectic silicon intensifies electron and phonon scattering, further reducing the alloy's thermal and electrical conductivity. With the rapid development of 5G technology, the requirements for product thermal conductivity are gradually increasing. Traditional aluminum-silicon cast alloys can no longer meet application needs, necessitating the development of a cast aluminum alloy with superior thermal conductivity.

[0003] To address this, researchers both domestically and internationally have improved the mechanical and thermal conductivity properties of Al-Si alloys through microalloying and other methods. Document CN105177368A discloses a method for preparing a die-cast aluminum alloy with high thermal and electrical conductivity. The alloy composition includes: Si 0.5–2.0 wt%, Cu 0.001–0.05 wt%, Fe 0.2–0.6 wt%, Mn 0.001–0.50 wt%, Mg 0.8–3.0 wt%, Zn 0.07–0.15 wt%, B 0.001–0.05 wt%, La 0.05–0.20 wt%, Y 0.05–0.2 wt%, Ce 0.05–0.2 wt%, with the balance being Al and impurities not exceeding 0.1 wt%. This alloy exhibits good thermal conductivity and corrosion resistance. The tensile strength is 220–270 MPa, the yield strength is 140–190 MPa, the elongation is 10–18%, the thermal conductivity is 120–160 W / (m·K), and the electrical conductivity reaches 20–30 mS / m. Document CN108546855A discloses a high thermal conductivity cast aluminum alloy and its preparation method. The alloy composition includes: Si 6.50–10.50%, Mg 0.30–0.50%, Co 0.10–0.50%, B 0.02–0.04%, Ti 0.01–0.05%, Mn 0.02–0.08%, Ni 0.03–0.07%, Zr 0.10–0.30%, Sb 0.01–0.03%, rare earth elements 0.10–0.50%, and the remainder being Al and unavoidable impurities. This alloy utilizes a combination of various metallic and rare earth elements to improve the thermal conductivity of the aluminum alloy, resulting in high strength, corrosion resistance, and excellent mechanical and electrical properties. Document CN109554589A discloses a high thermal conductivity rare earth aluminum alloy containing: Si: 9.1%, Fe: 0.78%, Sr: 0.02%, and Er: 0.10%, with the balance being Al and unavoidable impurity elements. This aluminum alloy exhibits good thermal conductivity (≥160 W / (m·K), as well as good mechanical and die-casting properties, with a tensile strength ≥270 MPa and a yield strength ≥120 MPa.

[0004] The aforementioned patent documents all achieve good mechanical and thermal conductivity properties through composition optimization design and preparation methods. However, the method described in CN105177368A has low Si and Mg content, resulting in poor casting performance. Furthermore, the high content of rare earth elements and the high price of rare earth Y lead to high alloy preparation costs. The method described in CN1904100A adds mixed rare earth elements up to 0.5%, but the high price of rare earth elements significantly increases the preparation cost for mass production. Achieving high strength and conductivity through various treatment methods, coupled with complex element types and cumbersome operational steps, is not conducive to mass production, further increasing costs. The alloy described in CN109554589A has very strict limitations on the types and contents of elements, and its high Er content makes it unsuitable for industrial production.

[0005] Therefore, in order to improve the thermal conductivity of cast aluminum alloys and reduce their cost, and to meet the demand for high thermal conductivity in aluminum alloy castings, it is necessary to develop a high thermal conductivity cast aluminum alloy and its preparation method. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a high thermal conductivity cast aluminum alloy and its preparation method. By optimizing the composition and adding relatively inexpensive Sc2O3 powder, the internal microstructure of the alloy is improved, thereby enhancing its thermal conductivity.

[0007] In a first aspect, embodiments of this application provide a high thermal conductivity cast aluminum alloy, the chemical composition of which, by mass percentage, is:

[0008] Fe: 1.6–2.5%;

[0009] B: 0.005~0.02%;

[0010] Sc: 0.01~0.05%;

[0011] The balance consists of Al and unavoidable impurity elements, the total amount of which does not exceed 0.3%.

[0012] Preferably, the thermal conductivity of the high thermal conductivity cast aluminum alloy is greater than or equal to 210.55 W / (m·K).

[0013] Secondly, another embodiment of this application discloses a method for preparing a high thermal conductivity cast aluminum alloy, which uses the aluminum alloy as described in the first aspect and includes the following steps:

[0014] (1) Material preparation: Weigh and group the pure aluminum ingots, Al-Fe master alloy or Fe agent, and Al-B master alloy according to the total weight and composition of the aluminum alloy according to the preset ratio, and preheat the weighed and grouped alloys at 100-300℃.

[0015] (2) Alloy melting: The preheated first part of pure aluminum ingot, Al-Fe master alloy or Fe agent are added to the resistance furnace in sequence and heated to melt at a temperature of 800-850°C. The melting temperature is maintained for 30 minutes to form the initial aluminum melt.

[0016] (3) Alloy modification: Sampling and testing the Fe content and mass of the initial aluminum melt. Weigh Sc2O3 powder and mixed halide salt, and mix Sc2O3 powder and mixed halide salt with the initial aluminum melt in sequence to obtain intermediate aluminum melt;

[0017] (4) First refining: The second part of pure aluminum ingots is added to the intermediate aluminum melt, the temperature of the aluminum melt is reduced to below 750°C, and an inert gas carrying refining agent is introduced for the first refining.

[0018] (5) Expansion treatment: Sample the aluminum alloy melt after the first refining to determine the content of Al-B master alloy added, and add the determined content of Al-B master alloy to the aluminum alloy melt after the first refining.

[0019] (6) Second refining: The third part of pure aluminum ingots is added to the expanded aluminum alloy melt, the temperature of the aluminum alloy melt is reduced to below 750°C, and an inert gas carrying refining agent is introduced for the second refining.

[0020] (7) Casting: After keeping it warm and standing for 30-60 minutes, the aluminum alloy melt is introduced into the degassing and filtering channel and then into the preheated mold. It is then naturally cooled and cast into ingots.

[0021] Preferably, sampling and testing the Fe content and melt mass in the initial aluminum melt involves weighing Sc2O3 powder and mixed halide salts, and sequentially mixing the Sc2O3 powder and mixed halide salts with the initial aluminum melt to obtain an intermediate aluminum melt, comprising the following steps:

[0022] Weigh the Sc2O3 powder and the mixed halide salt according to the Fe content in the initial aluminum melt;

[0023] The weighed Sc2O3 powder and the mixed halide salt, which were wrapped in aluminum foil, were pressed into the initial aluminum melt using a tool and stirred thoroughly to obtain an intermediate aluminum melt.

[0024] Preferably, the stirring is performed using an electromagnetic stirring device.

[0025] Preferably, the mixed halide salt is a mixture of any two of NaCl, KCl, and CaCl.

[0026] Preferably, the amount of Sc2O3 added is 0.01 to 0.5% of the mass of the aluminum melt.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The fluidity and castability of aluminum alloys are ensured by designing an appropriate Fe content. Al and Fe are eutectic alloys, and the Fe content at the eutectic point is 1.8%, at which point the alloy has the best fluidity and castability. Therefore, the Fe content in this application is designed to be 1.6-2.5%, which can ensure the fluidity and castability of aluminum alloys to the greatest extent.

[0029] (2) The microstructure of aluminum alloys is improved by adding Sc2O3 and mixed halide salts (chlorides), thereby enhancing the thermal conductivity of the aluminum alloys. Firstly, Al3Sc is obtained by the reduction of Al and Sc2O3 at high temperature, significantly reducing costs. The method is simple to operate and easily scalable for large-scale production. Simultaneously, the reaction rate is improved in several ways: firstly, increasing the reaction temperature enhances the relative motion between alloy atoms, thus improving reaction efficiency; secondly, adding chlorides improves the wettability of Sc2O3 and the melt, increasing the reaction time; and thirdly, electromagnetic stirring is used during alloy preparation, greatly promoting the reaction between the molten aluminum alloy and Sc2O3. Furthermore, some of the added Sc2O3 undergoes a substitution reaction to form Al3Sc. Due to the low content of added Sc2O3, the resulting Al3Sc is small in size and unstable at high temperatures, decomposing into free Sc and Al. Sc adheres to the surface of the iron-rich phase, thus refining the size of the iron-rich phase and improving its morphology. The other product, Al2O3, and the incompletely reacted Sc2O3, act as heterogeneous nucleation sites, promoting the nucleation of the iron-rich phase, further refining the iron-rich phase, reducing shrinkage porosity and reducing the formation of voids, and further improving the thermal conductivity of the alloy.

[0030] (3) Boration treatment removes some impurity elements and improves the morphology of the iron-rich phase, thereby enhancing the thermal conductivity of the alloy. On the one hand, boron reacts with V, Ti, and Cr to form compounds, which settle to the bottom of the furnace during the heat treatment process, thus removing transition elements and improving the thermal conductivity of the alloy. On the other hand, the high reactivity of boron allows it to adsorb onto the surface of the iron-rich phase nucleation substrate Al2O3, inhibiting the nucleation of the iron-rich phase and increasing the undercooling of the nucleation of the iron-rich phase, thereby refining the iron-rich phase.

[0031] In summary, this invention improves the thermal conductivity of aluminum alloy castings by refining the iron-rich phase and reducing the amount of primary iron-rich phase through the rational design of Fe content, the addition of Sc2O3, and boryling treatment. The aluminum alloy of this invention is particularly suitable for producing components such as electronic components and computer heat sinks used for heat dissipation. Attached Figure Description

[0032] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures.

[0033] Figure 1 This is a comparison chart of the thermal conductivity of the alloys in Examples 1-4 and Comparative Examples 1-4;

[0034] Figure 2 This is a schematic diagram illustrating the process of improving the thermal conductivity of aluminum alloys according to the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0036] The following is a detailed description of a method for preparing a high thermal conductivity cast aluminum alloy according to an embodiment of the present invention.

[0037] Example 1

[0038] Alloy composition: Fe content is 2.5%, B content is 0.02%, Sc content is 0.05%, and the balance is Al and unavoidable impurity elements, the total amount of which does not exceed 0.3%.

[0039] Step 1: Material preparation. First, according to the total weight and composition of the designed alloy, weigh and group the pure aluminum ingots, Al-Fe, Al-B master alloys and Sc2O3 powder (wrapped in aluminum foil to prevent oxidation) to prepare for smelting in advance. Then, preheat the above alloys to 250℃ in batches.

[0040] Step 2: Alloy melting. Most of the preheated aluminum ingots and Al-Fe master alloy are added to the resistance furnace in sequence, heated to melt, and the melt temperature is raised to 800℃ and held at 800℃ for 30 minutes.

[0041] Step 3: Alloy modification. Weigh Sc2O3 at a ratio of 0.5% according to the alloy design weight; mix the mixed halide salts (a mixture of NaCl, KCl, and CaCl, i.e., chlorides) thoroughly in advance using a mixer, wrap them in aluminum foil and preheat; press the melt into the furnace with a tool, and at the same time turn on the electromagnetic stirring system at the bottom of the furnace for 3 minutes to promote the full reaction of Sc2O3.

[0042] Step 4. First refining. Add the remaining pure aluminum, lower the temperature of the melt to 750°C, and then introduce an inert gas containing refining agents to purify the melt.

[0043] Step 5: Boring treatment. Take samples to test the alloy composition, adjust the alloy composition, and then add an Al-B master alloy.

[0044] Step 6: Second refining. The process is the same as the first refining step.

[0045] Step 7: Casting. After completing the above operations, let the melt stand for 30 minutes, then pour the aluminum alloy melt into a degassed and filtered ladle and then into a preheated mold. Let it cool naturally and cast into an ingot.

[0046] Example 2

[0047] Alloy composition: Fe content is 2.5%, B content is 0.005%, Sc content is 0.01%, and the balance is Al and unavoidable impurity elements, the total amount of which does not exceed 0.3%.

[0048] Step 1: Material preparation. First, according to the total weight and composition of the designed alloy, weigh and group the pure aluminum ingots, Fe agent, Al-B master alloy and Sc2O3 powder (wrapped in aluminum foil to prevent oxidation) to prepare for smelting in advance. Then, preheat the above alloys to 250℃ in batches.

[0049] Step 2: Alloy melting. Most of the preheated alloy aluminum ingots and Fe agent are added to the resistance furnace in sequence, heated to melt, and the melt temperature is raised to 850℃ and held at 800℃ for 30 minutes.

[0050] Step 3: Alloy modification. Weigh Sc2O3 at a ratio of 0.1% according to the alloy design weight; mix the mixed halide salts (a mixture of KCl and CaCl) thoroughly in advance using a mixer, wrap them in aluminum foil and preheat; press the melt into the furnace with a tool, and at the same time turn on the electromagnetic stirring system at the bottom of the furnace for 6 minutes to promote the full reaction of Sc2O3.

[0051] Step 4. First refining. Add the remaining pure aluminum, lower the temperature of the melt to 740°C, and then introduce an inert gas containing refining agents to purify the melt.

[0052] Step 5: Boring treatment. Take samples to test the alloy composition, adjust the alloy composition, and then add an Al-B master alloy.

[0053] Step 6: Second refining. The process is the same as the first refining step.

[0054] Step 7: Casting. After completing the above operations, let the melt stand for a period of time, then pour the aluminum alloy melt into a degassed and filtered ladle and then into a preheated mold. Let it cool naturally and cast into an ingot.

[0055] Example 3

[0056] Alloy composition: Fe content is 1.8%, B content is 0.005%, Sc content is 0.01%, and the balance is Al and unavoidable impurity elements, the total amount of which does not exceed 0.3%.

[0057] Step 1: Material preparation. First, according to the total weight and composition of the designed alloy, weigh and group the pure aluminum ingots, Al-Fe, Al-B master alloys and Sc2O3 powder (wrapped in aluminum foil to prevent oxidation) to prepare for smelting in advance. Then, preheat the above alloys to 250°C in batches.

[0058] Step 2: Alloy melting. Most of the preheated aluminum ingots, Al-Fe, and Al-Si master alloys are added to the resistance furnace in sequence, heated to melt, and the melt temperature is raised to 780℃ and held at 800℃ for 30 minutes.

[0059] Step 3: Alloy modification. Weigh Sc2O3 at a ratio of 0.1% according to the alloy design weight; mix the mixed halide salts (a mixture of NaCl, KCl, etc.) thoroughly in advance using a mixer, wrap them in aluminum foil and preheat; press them into the melt with a tool, and at the same time turn on the electromagnetic stirring system at the bottom of the furnace for 5 minutes to promote the full reaction of Sc2O3.

[0060] Step 4. First refining. Add the remaining pure aluminum, lower the temperature of the melt to 730°C, and then introduce an inert gas containing refining agents to purify the melt.

[0061] Step 5: Boring treatment. Take samples to test the alloy composition, adjust the alloy composition, and then add an Al-B master alloy.

[0062] Step 6: Second refining. The process is the same as the first refining step.

[0063] Step 7: Casting. After completing the above operations, let the melt stand for 45 minutes, then pour the aluminum alloy melt into a degassed and filtered ladle and then into a preheated mold. Let it cool naturally and cast into an ingot.

[0064] Example 4

[0065] Alloy composition: Fe content is 1.8%, B content is 0.02%, Sc content is 0.05%, and the balance is Al and unavoidable impurity elements, the total amount of which does not exceed 0.3%.

[0066] Step 1: Material preparation. First, according to the total weight and composition of the designed alloy, weigh and group the pure aluminum ingots, Al-Fe, Al-B master alloys and Sc2O3 powder (wrapped in aluminum foil to prevent oxidation) to prepare for smelting in advance. Then, preheat the above alloys to 100°C in batches.

[0067] Step 2: Alloy melting. Most of the preheated aluminum ingots, Al-Fe, and Al-Mg master alloys are added to the resistance furnace in sequence, heated to melt, and the melt temperature is raised to 800℃ and held at 800℃ for 30 minutes.

[0068] Step 3: Alloy modification. Weigh Sc2O3 at a ratio of 0.5% according to the alloy design weight; mix the mixed halide salts (a mixture of NaCl and CaCl) thoroughly in advance using a mixer, wrap them in aluminum foil and preheat; press the melt into the furnace with a tool, and at the same time turn on the electromagnetic stirring system at the bottom of the furnace for 10 minutes to promote the full reaction between Sc2O3 and aluminum.

[0069] Step 4. First refining. Add the remaining pure aluminum to lower the temperature of the melt, and then introduce an inert gas containing refining agents to purify the melt.

[0070] Step 5: Boring treatment. Take samples to test the alloy composition, adjust the alloy composition, and then add an Al-B master alloy.

[0071] Step 6: Second refining. The process is the same as the first refining step.

[0072] Step 7: Casting. After completing the above operations, let the melt stand for 60 minutes, then pour the aluminum alloy melt into a degassed and filtered ladle and then into a preheated mold. Let it cool naturally and cast into an ingot.

[0073] Comparative Example 1:

[0074] Compared with Example 1, Comparative Example 1 did not add Sc2O3 and B elements to improve the morphology and size of the iron-rich phase and reduce porosity of the alloy. The example improved the thermal conductivity of the alloy.

[0075] Comparative Example 2:

[0076] Compared to Example 2, the modification treatment was performed by replacing Sc2O3 and B elements with an equal amount of Al-10Ce.

[0077] Comparative Example 3:

[0078] Compared with Example 3, the modification treatment was performed by replacing Sc2O3 and B elements with an equal amount of Al-5Ti-1B.

[0079] Comparative Example 4:

[0080] Compared to Example 4, the modification treatment was performed by replacing Sc2O3 and B elements with an equal amount of Al-10Y.

[0081] Samples were taken from the ingots of Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3, 4. Two samples were taken from the front and back sides of each example to measure the electrical conductivity for comparison. The measured thermal conductivity is shown in Table 1.

[0082] Table 1 Comparison of thermal conductivity of aluminum alloys in Examples 1-4 and Comparative Examples 1-4

[0083]

[0084]

[0085] Comparing the data in Table 1, it can be seen that the addition of Sc2O3 and B elements significantly improves thermal conductivity. Furthermore, the effect is better than that of equal amounts of Ce, Al-5Ti-1B, and Y. Combined with the optimized alloy composition design, this high thermal conductivity aluminum alloy material was prepared, which is beneficial for the fabrication of heat dissipation components such as electronic components and computer heat sinks. Figure 1 The comparison of the thermal conductivity of the alloys in Examples 1-4 and Comparative Examples 1-4 is shown; Figure 2 This demonstrates the process and reasons for improving the thermal conductivity of aluminum alloys according to the present invention.

[0086] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a high thermal conductivity cast aluminum alloy, characterized in that, Includes the following steps: (1) Material preparation: Weigh and group the pure aluminum ingots, Al-Fe master alloy or Fe agent, and Al-B master alloy according to the total weight and composition of the aluminum alloy according to the preset ratio. Preheat the weighed and grouped alloys at 100-300℃. (2) Alloy melting: The preheated first part of pure aluminum ingot, Al-Fe master alloy or Fe agent are added to the resistance furnace in sequence and heated to melt. The melting temperature is 750~800℃, and the temperature is held at 800℃ for 30 minutes to form the initial aluminum melt. (3) Alloy modification: Sampling and testing the Fe content and mass of the initial aluminum melt. Weigh Sc2O3 powder and mixed halide salt, and mix Sc2O3 powder and mixed halide salt with the initial aluminum melt in sequence to obtain intermediate aluminum melt; (4) First refining: The second part of pure aluminum ingots is added to the intermediate aluminum melt, the temperature of the aluminum melt is reduced to below 750°C, and an inert gas carrying refining agent is introduced for the first refining. (5) Boring treatment: Take samples of the aluminum alloy melt after the first refining to determine the content of Al-B master alloy added, and add the Al-B master alloy with the determined content to the aluminum alloy melt after the first refining. (6) Second refining: The third part of pure aluminum ingots is added to the boronized aluminum alloy melt, the temperature of the aluminum alloy melt is reduced to below 750°C, and an inert gas carrying refining agent is introduced for the second refining. (7) Casting: After keeping it warm and standing for 30-60 minutes, the aluminum alloy melt is introduced into the degassing and filtering channel and then into the preheated mold. It is then cooled naturally and cast into ingots. The preset proportions are as follows: the chemical composition of the high thermal conductivity cast aluminum alloy, by mass percentage, is: Fe: 1.6~2.5%; B：0.005~0.02%； Sc: 0.01~0.05%; The balance consists of Al and unavoidable impurity elements, the total amount of which does not exceed 0.3%.

2. The method for preparing high thermal conductivity cast aluminum alloy according to claim 1, characterized in that, The initial aluminum melt was sampled and tested for Fe content and melt mass. Sc2O3 powder and mixed halide salts were weighed and then sequentially mixed with the initial aluminum melt to obtain an intermediate aluminum melt, comprising the following steps: Weigh the Sc2O3 powder and the mixed halide salt according to the Fe content in the initial aluminum melt; The weighed Sc2O3 powder and the mixed halide salt, which were wrapped in aluminum foil, were pressed into the initial aluminum melt using a tool and stirred thoroughly to obtain an intermediate aluminum melt.

3. The method for preparing high thermal conductivity cast aluminum alloy according to claim 2, characterized in that, The stirring is performed using an electromagnetic stirring device.

4. The method for preparing high thermal conductivity cast aluminum alloy according to claim 3, characterized in that, Mixed halide salts are mixtures of any two of NaCl, KCl, and CaCl2.

5. The method for preparing high thermal conductivity cast aluminum alloy according to claim 4, characterized in that, The amount of Sc2O3 added is 0.01~0.5% of the mass of the aluminum melt.

6. The method for preparing high thermal conductivity cast aluminum alloy according to claim 5, characterized in that, The thermal conductivity of the high thermal conductivity cast aluminum alloy is greater than or equal to 210.55 W / (m·K).

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