Aluminum alloy cast article, heat dissipation member, and method for producing aluminum alloy cast article

Abstract

This aluminum alloy cast article contains 13.0 mass% to 22.0 mass% inclusive of silicon (Si), 0.003 mass% to 0.02 mass% inclusive of phosphorus (P), 0.3 mass% or less of iron (Fe), 0.2 mass% or less of copper (Cu), and aluminum (Al). The thermal conductivity of this aluminum alloy cast article is 165 W / (m·K) or higher.

Description

Aluminum alloy castings, heat dissipation members, and methods for manufacturing aluminum alloy castings

[0001] This disclosure relates to aluminum alloy castings, heat dissipation members, and methods for manufacturing aluminum alloy castings.

[0002] Heat dissipation components such as pin fins are attached to heat-generating components. Some heat dissipation components are made of aluminum alloy castings. Aluminum alloy castings are disclosed in Patent Documents 1 and 2.

[0003] Japanese Patent Publication No. 2014-538492 Japanese Patent Publication No. 2001-295769

[0004] It is conceivable to join a heat dissipation member, made of an aluminum alloy casting, to a heat-generating member by methods such as soldering. Examples of heat-generating members include power semiconductors. In this case, if the coefficient of thermal expansion of the joining member is small and the coefficient of thermal expansion of the aluminum alloy casting is large, the aluminum alloy casting, which is the heat dissipation member, will warp. Therefore, if the difference in the coefficients of thermal expansion between the heat dissipation member and the joining member is large, stress will be placed on the joining member, reducing its lifespan. Furthermore, it is preferable that the heat dissipation member has a high thermal conductivity.

[0005] In one aspect of this disclosure, it is preferable to provide an aluminum alloy casting, a heat dissipation member, and a method for manufacturing an aluminum alloy casting, which have a low coefficient of thermal expansion and high thermal conductivity.

[0006] (1) One aspect of the present disclosure is an aluminum alloy casting containing 13.0% by mass or more and 22.0% by mass or less of silicon (Si), 0.003% by mass or more and 0.02% by mass or less of phosphorus (P), 0.3% by mass or less of iron (Fe), 0.2% by mass or less of copper (Cu), and aluminum (Al), and having a thermal conductivity of 165 W / (m·K) or more. The aluminum alloy casting, which is one aspect of the present disclosure, has a low coefficient of linear expansion and high thermal conductivity.

[0007] (2) Another aspect of the present disclosure is a method for manufacturing an aluminum alloy casting, comprising filling a mold with molten aluminum alloy containing 13.0% to 22.0% by mass of silicon (Si), 0.003% to 0.02% by mass of phosphorus (P), 0.3% or less by mass of iron (Fe), 0.2% or less by mass of copper (Cu), and aluminum (Al), cooling and solidifying the filled molten aluminum alloy, and then heat-treating the resulting solidified aluminum alloy casting at a temperature of 300°C or higher. The method for manufacturing an aluminum alloy casting, which is another aspect of the present disclosure, can produce an aluminum alloy casting with a low coefficient of thermal expansion and high thermal conductivity.

[0008] Exemplary embodiments of the present disclosure will be described below. 1. Composition of the first aluminum alloy casting The first aluminum alloy casting comprises 13.0% by mass or more and 22.0% by mass of silicon (Si), 0.003% by mass or more and 0.02% by mass of phosphorus (P), 0.3% by mass or less of iron (Fe), 0.2% by mass or less of copper (Cu), and aluminum (Al).

[0009] Aluminum is the main component of the first aluminum alloy casting. In the composition of the first aluminum alloy casting, aluminum is the component with the largest mass ratio. In the composition of the first aluminum alloy casting, the mass ratio of aluminum is, for example, 75% by mass or more and 90% by mass or less.

[0010] The mass ratio of silicon is preferably 13% by mass or more and 22% by mass or less, and more preferably 15% by mass or more and 22% by mass or less. The mass ratio of phosphorus is preferably 0.003% by mass or more and 0.02% by mass or less, and more preferably 0.03% by mass or more and 0.015% by mass or less.

[0011] The mass ratio of iron is preferably 0.3% by mass or less, and more preferably 0.2% by mass or less. The mass ratio of copper is preferably 0.2% by mass or less, and more preferably 0.15% by mass or less. The first aluminum alloy casting further contains, for example, unavoidable impurities.

[0012] The thermal conductivity of the first aluminum alloy casting is 165 W / (m·K) or higher. The thermal conductivity can be increased by heat treatment during the manufacturing of the first aluminum alloy casting. Preferably, the thermal conductivity of the first aluminum alloy casting is 175 W / (m·K) or higher, and more preferably 185 W / (m·K) or higher. The method for measuring the thermal conductivity is the flash method (JIS R 1611).

[0013] The coefficient of linear expansion of the first aluminum alloy casting at 30 to 300°C is 21.0 × 10⁻⁶. －６ It is preferable that it be less than or equal to / K. The coefficient of linear expansion of the first aluminum alloy casting at 30 to 300°C is 20.5 × 10 －６ It is even more preferable that it be less than or equal to / K, and 20.0 × 10 －６ It is particularly preferable that the coefficient of thermal expansion is less than or equal to / K. By setting the composition of the first aluminum alloy casting to the above composition, the coefficient of thermal expansion can be reduced. The method for measuring the coefficient of thermal expansion is the push bar type compression load method (JIS Z 2285).

[0014] 2. Composition of the second aluminum alloy casting The second aluminum alloy casting contains 13.0% by mass or more and 22.0% by mass of silicon (Si), 0.003% by mass or more and 0.02% by mass of phosphorus (P), 0.15% by mass or less of iron (Fe), and aluminum (Al).

[0015] Aluminum is the main component of the second aluminum alloy casting. In the composition of the second aluminum alloy casting, aluminum is the component with the largest mass ratio. In the composition of the second aluminum alloy casting, the mass ratio of aluminum is, for example, 76% by mass or more and 91% by mass or less.

[0016] The mass ratio of silicon is preferably 13% by mass or more and 22% by mass or less, and more preferably 15% by mass or more and 22% by mass or less. The mass ratio of phosphorus is preferably 0.003% by mass or more and 0.02% by mass or less, and more preferably 0.003% by mass or more and 0.015% by mass or less.

[0017] The iron content by mass ratio is preferably 0.15 mass% or less, more preferably 0.10 mass% or less. The second aluminum alloy cast product further includes, for example, unavoidable impurities.

[0018] The thermal conductivity of the second aluminum alloy cast product is 185 W / (m·K) or higher. When producing the second aluminum alloy cast product, the thermal conductivity can be increased by performing heat treatment. The thermal conductivity of the second aluminum alloy cast product is preferably 190 W / (m·K) or higher, and more preferably 195 W / (m·K) or higher.

[0019] The coefficient of linear expansion of the second aluminum alloy cast product at 30 to 300°C is 21.0×10 －６ / K or less, which is preferable. The coefficient of linear expansion of the second aluminum alloy cast product at 30 to 300°C is 20.5×10 －６ / K or less, which is more preferable, and 20.0×10 －６ / K or less, which is particularly preferable. By setting the composition of the second aluminum alloy cast product to the aforementioned composition, the coefficient of linear expansion can be reduced.

[0020] 3. Configuration of heat dissipation member The heat dissipation member is, for example, a pin fin or the like. The heat dissipation member includes the first aluminum alloy cast product or the second aluminum alloy cast product. For example, part or all of the heat dissipation member is the first aluminum alloy cast product or the second aluminum alloy cast product.

[0021] The coefficient of linear expansion of the heat dissipation member at 30 to 300°C is 21.0×10 －６ / K or less, which is preferable. The coefficient of linear expansion of the heat dissipation member at 30 to 300°C is 20.5×10 －６ / K or less, which is more preferable, and 20.0×10 －６ / K or less, which is particularly preferable.

[0022] 4. Method for Manufacturing the First Aluminum Alloy Casting The method for manufacturing the first aluminum alloy casting is as follows, for example: A molten aluminum alloy containing 13.0% to 22.0% by mass of silicon (Si), 0.003% to 0.02% by mass of phosphorus (P), 0.3% or less by mass of iron (Fe), 0.2% or less by mass of copper (Cu), and aluminum (Al) is filled into a mold. This molten aluminum alloy has the same composition as the first aluminum alloy casting.

[0023] Next, the filled molten aluminum alloy is cooled and solidified. This solidification produces an aluminum alloy casting. Then, the resulting solidified aluminum alloy casting is heat-treated at a temperature of 300°C or higher. The heat treatment is carried out, for example, in air and at atmospheric pressure. The heat treatment temperature is more preferably 350°C or higher. The heat treatment time is preferably 10 minutes or more, and more preferably 30 minutes or more.

[0024] Methods for filling a mold with molten aluminum alloy and then cooling and solidifying the molten aluminum alloy include, for example, low-pressure casting or gravity casting. Low-pressure casting or gravity casting reduce costs because they involve fewer steps.

[0025] Low-pressure casting can be carried out, for example, as follows: Low-pressure casting consists of a molten metal preparation step and a casting step. In the molten metal preparation step, each component element is added and heated and melted according to a conventional method to achieve a predetermined composition, and molten metal treatment such as dehydrogenation gas treatment and inclusion removal treatment is performed. Then, the molten metal temperature is adjusted so that the final molten metal temperature is 700 to 800°C.

[0026] In the casting process, the molten metal, whose temperature has been adjusted to 700-800°C in the molten metal preparation process, is cast into the shape of the heat dissipation component using a pressure casting method with a mold such as a sand mold or a metal mold. The preheating temperature of the mold is adjusted to 100-700°C.

[0027] Gravity casting can be carried out, for example, as follows: The raw materials are mixed to achieve the desired composition. Next, the raw materials are placed in a graphite crucible and heated to 740°C using an electric furnace to form molten metal. Next, the molten metal is poured into a graphite mold and allowed to solidify. Next, heat treatment is performed in an electric furnace. The heat treatment is carried out in an air atmosphere and at atmospheric pressure, and the sample material is held at 300°C or higher and below 500°C for 30 minutes. After the above holding, the sample is removed from the furnace and air-cooled.

[0028] 5. Method for Manufacturing the Second Aluminum Alloy Casting The method for manufacturing the second aluminum alloy casting is, for example, as follows: A molten aluminum alloy containing 13.0% to 22.0% by mass of silicon (Si), 0.003% to 0.02% by mass of phosphorus (P), 0.15% or less of iron (Fe), and aluminum (Al) is filled into a mold. This molten aluminum alloy has the same composition as the second aluminum alloy casting.

[0029] Next, the filled molten aluminum alloy is cooled and solidified. This solidification produces an aluminum alloy casting. Then, the resulting solidified aluminum alloy casting is heat-treated at a temperature of 300°C or higher. The heat treatment is carried out, for example, in air and at atmospheric pressure. The heat treatment temperature is more preferably 350°C or higher. The heat treatment time is preferably 10 minutes or more, and more preferably 30 minutes or more.

[0030] Methods for filling a mold with molten aluminum alloy and then cooling and solidifying the molten aluminum alloy include, for example, low-pressure casting or gravity casting. Low-pressure casting or gravity casting reduce costs because they involve fewer steps.

[0031] 6. Effects of the first aluminum alloy casting, the second aluminum alloy casting, and their manufacturing methods (1A) The first aluminum alloy casting and the second aluminum alloy casting have a low coefficient of linear expansion and high thermal conductivity.

[0032] (1B) According to the method for manufacturing aluminum alloy castings of the present disclosure, an aluminum alloy casting with a low coefficient of linear expansion and high thermal conductivity can be manufactured. (1C) A heat dissipation member including the first aluminum alloy casting or the second aluminum alloy casting can be manufactured. The heat dissipation member has a low coefficient of linear expansion and high thermal conductivity.

[0033] 7. Examples (1) Production of Aluminum Alloy Castings S1 to S8 Aluminum alloy castings S1 to S8 were produced by the following method. First, a molten aluminum alloy was prepared containing silicon (Si), phosphorus (P), magnesium (Mg), and iron (Fe) in the mass ratios listed in the "Chemical Composition" column of Table 1. The remainder of the molten aluminum alloy, other than silicon (Si), phosphorus (P), magnesium (Mg), and iron (Fe), consisted of the main component, aluminum (Al), and unavoidable impurities.

[0034]

[0035] Next, molten aluminum alloy was poured into a mold, and the poured molten aluminum alloy was cooled and solidified. This method involved gravity casting in a book mold. By cooling and solidifying the molten aluminum alloy, an aluminum ingot was produced.

[0036] Next, the aluminum ingot was subjected to heat treatment according to the conditions listed in the "Heat Treatment Conditions" column of Table 1. The heat treatment was carried out in air at atmospheric pressure. For example, if "410°C - 30 min" was listed in the "Heat Treatment Conditions" column of Table 1, the heat treatment was performed at 410°C for 30 minutes. Through the above process, an aluminum alloy casting was obtained.

[0037] (2) Evaluation of aluminum alloy castings Test specimens were cut from aluminum alloy castings. Next, the physical properties of the test specimens were evaluated. The physical properties evaluated included the measurement of the coefficient of linear expansion and the measurement of thermal conductivity. For the measurement of the coefficient of linear expansion, measurements were taken at 30 to 100°C, 30 to 200°C, and 30 to 300°C, respectively.

[0038] The measurement conditions for the coefficient of linear expansion were as follows. ・Measurement method: Push-rod type linear expansion measurement ・Load: 9.8×10 －２ N ・Manufacturer of the measuring device: Rigaku Corporation ・Model (control number) of the measuring device: TMA8310 (GO-024) ・Reference standard: JIS-Z 2285 (2003) ・Measurement temperature range: 30°C to 300°C ・Heating rate: 5°C / min ・Measurement atmosphere: Nitrogen ・Control comparison material: Quartz ・Temperature measurement position: Inside the sample ・Specimen shape: φ5 mm × 20 mm. However, the coefficient of linear expansion for S8 is the value for 6063 alloy from the Aluminum Handbook.

[0039] Thermal conductivity λ (W / (m·K)) was measured by the flash method (JIS R 1611). However, for S5 to S7, it was calculated by the following formula (1). Formula (1) λ=308.96×ρ+89.811 The density ρ in formula (1) was measured under the following conditions.

[0040] Measurement method: Archimedes method ・Manufacturer of the measuring device: A&D Company, Limited ・Model (control number) of the measuring device: GH-202 (R2-072) ・Reference standard: JIS Z 8807 (2012) ・Immersion liquid: Deionized water ・Measurement temperature: 25°C ・Specimen shape: 10 mm × 10 mm × 10 mm. In addition, the thermal conductivity value for S8 is the value of 6063 alloy-O material extracted from "Microstructure and Properties of Aluminum" (Japan Institute of Light Metals (1991)).

[0041] The measurement results are shown in Table 1. In S1 to S4, the coefficient of linear expansion was low and the thermal conductivity was high. Compared with these, the coefficient of linear expansion was higher in S8. In addition, compared with S1 to S4, the thermal conductivity was lower in S5 to S7.

[0042] 8. Other Embodiments The embodiments of the present disclosure have been described above. However, the present disclosure is not limited to the above-described embodiments, and can be implemented with various modifications.

[0043] (1) The function of one component in each of the above embodiments may be divided among multiple components, or the function of multiple components may be performed by one component. Also, some of the configurations of each of the above embodiments may be omitted. Also, at least some of the configurations of each of the above embodiments may be added to, replaced with, etc., the configurations of other embodiments.

[0044] (2) In addition to the aluminum alloy castings described above, this disclosure can also be realized in various forms, such as a system using the aluminum alloy castings as components, a method for manufacturing heat dissipation members, and a method for heat treating aluminum alloy castings.

Claims

1. An aluminum alloy casting containing 13.0% to 22.0% by mass of silicon (Si), 0.003% to 0.02% by mass of phosphorus (P), 0.3% or less by mass of iron (Fe), 0.2% or less by mass of copper (Cu), and aluminum (Al), and having a thermal conductivity of 165 W / (m·K) or higher.

2. An aluminum alloy casting according to claim 1, wherein the iron (Fe) content is 0.15% by mass or less, and the thermal conductivity is 185 W / (m·K) or more.

3. An aluminum alloy casting according to claim 1 or 2, wherein the coefficient of linear expansion at 30 to 300°C is 21 × 10⁻⁶ －６ Aluminum alloy castings with a coefficient of 1 / K or less.

4. An aluminum alloy casting according to claim 1 or 2, wherein the mass ratio of silicon is 15% by mass or more and 22% by mass or less.

5. An aluminum alloy casting according to claim 1 or 2, wherein the mass ratio of phosphorus is 0.003% by mass or more and 0.015% by mass or less.

6. An aluminum alloy casting according to claim 1, wherein the mass ratio of aluminum is 75% by mass or more and 90% by mass or less.

7. An aluminum alloy casting according to claim 2, wherein the mass ratio of aluminum is 76% by mass or more and 91% by mass or less.

8. A heat dissipation member comprising an aluminum alloy casting according to claim 1 or 2.

9. A heat dissipation member according to claim 8, wherein the coefficient of linear expansion at 30 to 300°C is 21 × 10 －６ A heat dissipation component with a temperature of / K or less.

10. A method for manufacturing an aluminum alloy casting, comprising: filling a mold with molten aluminum alloy containing 13.0% to 22.0% by mass of silicon (Si), 0.003% to 0.02% by mass of phosphorus (P), 0.3% or less by mass of iron (Fe), 0.2% or less by mass of copper (Cu), and aluminum (Al); cooling and solidifying the filled molten aluminum alloy; and heat-treating the resulting solidified aluminum alloy casting at a temperature of 300°C or higher.

11. A method for manufacturing an aluminum alloy casting according to claim 10, wherein the iron (Fe) content in the molten aluminum alloy is 0.15% by mass or less.

12. A method for manufacturing an aluminum alloy casting according to claim 10 or claim 11, wherein the method of filling a mold with molten aluminum alloy and cooling and solidifying the filled molten aluminum alloy is a low-pressure casting method or a gravity casting method.

13. A method for manufacturing an aluminum alloy casting according to claim 10 or 11, wherein the time of the heat treatment is 10 minutes or more.

14. A method for manufacturing an aluminum alloy casting according to claim 10 or 11, wherein the heat treatment time is 30 minutes or more.

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