Aluminum alloys and aluminum alloy castings

Abstract

A relatively inexpensive aluminum alloy capable of achieving high conductivity and high strength is provided, as well as a relatively inexpensive aluminum alloy casting comprising the aluminum alloy and possessing both high conductivity and high strength. The aluminum alloy contains Ni: 2.0% to less than 4.5% by mass, Co: 0.01% to less than 1.00% by mass, Fe: 0.1% to less than 2.5% by mass, and the remainder consists of Al and unavoidable impurities.

Description

Technical Field

[0001] This invention relates to an aluminum alloy and aluminum alloy castings, which can be suitably used as materials for conductive components in electronic devices and the like. Background Technology

[0002] Aluminum has about 60% the electrical conductivity of copper, but its specific gravity is about one-third that of copper, and it can conduct twice the current of the same weight of copper. In recent years, the application of aluminum alloys in applications requiring lightweight and high conductivity has been considered, and there is a strong desire to improve the conductivity of aluminum alloy materials.

[0003] However, in the past, improving the thermal conductivity and electrical conductivity of aluminum alloy materials has often been a subject of study, and it cannot be said that electrical conductivity has been fully researched. On the other hand, for example, in Patent Document 1 (Japanese Patent Unexamined Publication No. 2001-254135), in order to solve the problem of "providing an aluminum alloy in Al-Fe-Ni alloy that increases electrical conductivity and thermal conductivity while maintaining its strength", it was proposed that "an aluminum alloy material contains 0.002 wt% to 0.08 wt% of B, and also contains 0.05 wt% to 2.5 wt% of Fe and / or 0.05 wt% to 2.5 wt% of Ni, with the balance consisting of aluminum and unavoidable impurities".

[0004] In the aluminum alloy material described in Patent Document 1, in order to satisfy all the properties of the aluminum alloy that are highly interdependent, such as strength and thermal conductivity / electrical conductivity, especially high thermal conductivity and electrical conductivity, it is claimed that, as the result of various studies on the elements added to the alloy, a predetermined amount of element B is extremely effective.

[0005] Furthermore, in Patent Document 2 (Japanese Patent Unexamined Publication No. 2005-048206), in order to solve the problem of "providing a high-strength and high-conductivity aluminum alloy matrix composite material that combines high strength and high conductivity, and providing a method for producing the same", it was proposed that "a high-strength and high-conductivity aluminum alloy matrix composite material is characterized by containing 0.1 vol% to 10 vol% carbon nanotubes, wherein the carbon nanotubes have a single-walled or multi-walled structure with a diameter of 1 nm to 100 nm and an aspect ratio of 10 to 100".

[0006] In the high-strength, high-conductivity aluminum alloy matrix composite material described in Patent Document 2, by containing carbon nanotubes in the aluminum alloy matrix, it is claimed that an aluminum alloy matrix composite material with both high strength and high conductivity can be obtained due to the ultrafine strengthening effect.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Unexamined Publication No. 2001-254135

[0010] Patent Document 2: Japanese Patent Unexamined Publication No. 2005-048206 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] However, in the aluminum alloy material described in Patent Document 1, since B is an essential additive element and its content needs to be controlled, it is difficult to obtain the aluminum alloy material simply and efficiently. Furthermore, the mechanical properties of the obtained aluminum alloy material are not disclosed, and it is unclear whether the aluminum alloy material possesses sufficient strength.

[0013] Furthermore, in the high-strength and high-conductivity aluminum alloy matrix composite material described in Patent Document 2, carbon nanotubes need to be dispersed in the aluminum matrix. However, since carbon nanotubes are typically difficult to disperse, the manufacturing process becomes extremely complex. In addition, the high cost of carbon nanotubes themselves inevitably increases the cost of the resulting composite material. Moreover, areas where carbon nanotubes aggregate can become fracture initiation points, making it difficult to ensure the reliability of the composite material. Furthermore, the reaction between carbon nanotubes and aluminum needs to be considered.

[0014] In view of the problems in the background art as described above, the object of the present invention is to provide a relatively inexpensive aluminum alloy that can exhibit high conductivity and high strength, and a relatively inexpensive aluminum alloy casting having high conductivity and high strength made from said aluminum alloy.

[0015] Technical means to solve the problem

[0016] To achieve the above objectives, the inventors conducted extensive research on the composition of aluminum alloys and discovered that, in order to impart high conductivity and high strength to aluminum alloy castings, it is effective to add Ni, Co, and Fe as essential additive elements and strictly control the content of these elements, thereby achieving the present invention.

[0017] That is, the present invention provides an aluminum alloy containing

[0018] Ni: greater than 2.0% by mass and less than 4.5% by mass

[0019] Co: greater than 0.01% by mass and less than 1.00% by mass

[0020] Fe: greater than 0.1% by mass and less than 2.5% by mass, and

[0021] The balance consists of Al and unavoidable impurities.

[0022] Ni, Co, and Fe all form intermetallic compounds and contribute to improving the strength of aluminum alloy castings. On the other hand, the resulting intermetallic compounds are relatively fine, and this tendency is particularly observed in intermetallic compounds containing Ni and Co. As a result, the deterioration of the mechanical properties of aluminum alloy castings due to the formation of coarse intermetallic compounds can be suppressed.

[0023] Although the mechanism by which the conductivity of aluminum alloy castings increases when more than 2.0% by mass and less than 4.5% by mass of Ni, more than 0.01% by mass and less than 1.00% by mass of Co, and more than 0.1% by mass and less than 2.5% by mass of Fe is not fully understood, it is believed that high conductivity can be achieved by releasing Ni, Co, Fe and trace amounts of impurity elements from the aluminum matrix as fine intermetallic compounds.

[0024] In the aluminum alloy of the present invention, the preferred Ni content is greater than 2.5% by mass and less than 4.0% by mass, the Co content is greater than 0.10% by mass and less than 0.60% by mass, and the Fe content is greater than 0.2% by mass and less than 2.0% by mass.

[0025] Furthermore, in the aluminum alloy of the present invention, it is also preferable to contain one or more of B: 0.001% to 0.030% by mass and Sr: 0.005% to 0.30% by mass as optional additive elements. Since B has the effect of promoting the refinement of the casting microstructure, and Sr has the effect of suppressing the coarsening of crystals by shortening the solidification time associated with undercooling, the mechanical properties of the aluminum alloy casting can be improved.

[0026] Furthermore, transition metals such as Ti and V significantly reduce conductivity in the solid solution state, and the conductivity of aluminum alloy castings decreases when these elements are present as unavoidable impurities. On the other hand, since boron (B) forms intermetallic compounds with transition metals such as Ti and V, the conductivity of aluminum alloy castings can be improved by adding 0.001% to 0.030% by mass of B to precipitate trace amounts of transition metals (solid solution elements) that are present as unavoidable impurities.

[0027] Furthermore, in the aluminum alloy of the present invention, it is also preferable to contain one or more of the following optional additive elements: Si: 0.1% to 0.5% by mass, Mg: 0.1% to 0.5% by mass, Cu: 0.1% to 0.5% by mass, and Zn: 0.1% to 0.5% by mass. Since these elements contribute to improving the strength of the aluminum alloy casting, the strength of the aluminum alloy casting can be adjusted as needed. When it is desired to further improve the strength of the aluminum alloy casting, it can be heat-treated under suitable conditions.

[0028] Furthermore, the present invention also provides an aluminum alloy casting made from the aluminum alloy of the present invention, characterized in that its electrical conductivity is 49% of the international annealed copper standard (IACS) or greater than 49% IACS. The only necessary additive elements in the aluminum alloy of the present invention are Ni, Co, and Fe, thereby enabling the simple and efficient acquisition of aluminum alloy castings with an electrical conductivity of 49% IACS or greater.

[0029] In the aluminum alloy castings of the present invention, the 0.2% proof stress is preferably 70 MPa or greater. In addition to a conductivity of 49% IACS or greater, when the 0.2% proof stress is also 70 MPa or greater, it can be suitably used for conductive components requiring high reliability.

[0030] Furthermore, the aluminum alloy castings of the present invention are preferably made of die-casting material. By using die-casting material, aluminum alloy castings with complex shapes can be mass-produced. In addition, although die-casting materials generally have low conductivity, by using the aluminum alloy of the present invention, a conductivity of 49% IACS or greater can be ensured.

[0031] The effects of the invention

[0032] According to the present invention, a relatively inexpensive aluminum alloy capable of exhibiting high conductivity and high strength can be provided, as well as a relatively inexpensive aluminum alloy casting having high conductivity and high strength made from said aluminum alloy. Detailed Implementation

[0033] The aluminum alloy and aluminum alloy castings of the present invention will be described in detail below, but the present invention is not limited thereto.

[0034] 1. Aluminum alloy

[0035] The aluminum alloy of this invention is characterized by an optimized composition to impart high electrical conductivity and high strength to the aluminum alloy castings. More specifically, Ni, Co, and Fe are essential additive elements, and the content of these elements is strictly controlled. The composition will be explained in detail below.

[0036] (1) Required elements

[0037] Ni: greater than 2.0% by mass and less than 4.5% by mass

[0038] Ni disperses fine intermetallic compounds in the alloy and improves the strength of aluminum alloy castings. Because the fine intermetallic compounds are uniformly dispersed, the amount of Ni in the matrix can be effectively reduced, and strength can be increased while minimizing the adverse effects on the conductivity of the aluminum alloy casting. The Ni content is preferably set to greater than 2.5% by mass and less than 4.0% by mass, and more preferably greater than 3.0% by mass and less than 3.5% by mass.

[0039] Co: greater than 0.01% by mass and less than 1.00% by mass

[0040] Co disperses fine intermetallic compounds in the alloy and improves the strength of aluminum alloy castings. Because the fine intermetallic compounds are uniformly dispersed, the amount of Co in the matrix can be effectively reduced, and strength can be increased while minimizing the adverse effects on the conductivity of the aluminum alloy casting. The Co content is preferably set to greater than 0.1% by mass and less than 0.6% by mass, more preferably to 0.15% by mass and 0.3% by mass.

[0041] Fe: greater than 0.1% by mass and less than 2.5% by mass

[0042] Fe forms intermetallic compounds and improves the strength of aluminum alloy castings, but excessive addition reduces the conductivity of the castings. When the Fe addition is set to greater than 0.1% by mass, it enhances the strength of the aluminum alloy castings, and when set to less than 2.5% by mass, it suppresses the decrease in conductivity. The Fe addition is preferably set to greater than 0.2% by mass and less than 2.0% by mass, more preferably greater than 0.3% by mass and less than 1.0% by mass.

[0043] (2) Add any element

[0044] When it is necessary to adjust the strength or conductivity of aluminum alloy castings, the following elements may be added as appropriate.

[0045] B: 0.001% by mass to 0.030% by mass

[0046] B has the effect of promoting the refinement of the microstructure of castings. Not only is an increase in the strength of aluminum alloy castings expected due to microstructure refinement, but it is also expected to improve the electrical conductivity of aluminum alloy castings by promoting the precipitation of intermetallic compounds caused by the necessary additive element and removing Ni, Co, Fe, and trace impurity elements from the aluminum matrix as fine intermetallic compounds. The amount of B added is preferably set to 0.005% to 0.025% by mass, more preferably 0.010% to 0.020% by mass.

[0047] Sr: 0.005% by mass to 0.030% by mass

[0048] Sr has the effect of suppressing crystal coarsening by shortening the solidification time associated with supercooling, and can improve the mechanical properties of aluminum alloy castings. The amount of Sr added is preferably set to 0.010% to 0.025% by mass, more preferably 0.015% to 0.020% by mass.

[0049] Si: 0.1% to 0.5% by mass

[0050] By enabling Si to coexist with the essential additive elements Ni, Co, and Fe, the precipitation of intermetallic compounds induced by Ni, Co, and Fe can be promoted. Due to this effect, not only are improved mechanical properties of aluminum alloy castings expected, but also increased electrical conductivity is anticipated due to the reduction of Ni, Co, and Fe in the matrix. Furthermore, the addition of Si is also expected to improve fluidity during the casting process.

[0051] Mg: 0.1% to 0.5% by mass

[0052] Mg contributes to improving the strength of aluminum alloy castings through solid solution strengthening and precipitation strengthening. When further improvement in the mechanical properties of aluminum alloy castings is desired, 0.1% to 0.5% by mass of Mg can be added.

[0053] Cu: 0.1% to 0.5% by mass

[0054] Cu helps improve the strength of aluminum alloy castings through solid solution strengthening and precipitation strengthening. When it is desired to further improve the mechanical properties of aluminum alloy castings, 0.1% to 0.5% by mass of Cu can be added.

[0055] Zn: 0.1% to 0.5% by mass

[0056] Zn helps improve the strength of aluminum alloy castings through solid solution strengthening and precipitation strengthening. When it is desired to further improve the mechanical properties of aluminum alloy castings, 0.1% to 0.5% by mass of Zn can be added.

[0057] It should be noted that unavoidable impurities are permissible to the extent that they do not impair the performance of the aluminum alloy castings of this invention.

[0058] 2. Aluminum alloy castings

[0059] The aluminum alloy casting of the present invention is a high-conductivity aluminum alloy casting made of the aluminum alloy of the present invention, characterized by having an electrical conductivity of 49% IACS or greater than 49% IACS. The electrical conductivity of the aluminum alloy casting is preferably 50% IACS or greater than 50% IACS, more preferably 51% IACS or greater than 51% IACS.

[0060] Furthermore, the aluminum alloy casting of the present invention preferably has a 0.2% yield strength of 70 MPa or greater. Besides having an electrical conductivity of 49% IACS or greater, the 0.2% yield strength of 70 MPa or greater makes it suitable for use in conductive components requiring high reliability. The 0.2% yield strength of the aluminum alloy casting is preferably 75 MPa or greater, more preferably 80 MPa or greater.

[0061] Furthermore, the aluminum alloy castings of the present invention preferably have a high yield strength of 0.2% and an elongation at break of 10% or greater. When possessing good ductility and toughness, the aluminum alloy castings can be appropriately used in conductive components requiring high reliability. The elongation at break is preferably 15% or greater, more preferably 20% or greater.

[0062] The method for casting the aluminum alloy castings of the present invention is not particularly limited as long as it does not impair the effects of the present invention, and conventionally known die casting and gravity casting methods can be used, but die casting is preferred. By using it as a die casting material, aluminum alloy castings with complex shapes can be mass-produced. Furthermore, although die casting materials generally have low electrical conductivity, when using the aluminum alloy of the present invention, an electrical conductivity of 49% IACS or higher can be ensured.

[0063] Furthermore, there are no particular limitations on the casting conditions as long as they do not impair the effects of the present invention, and various conventional and well-known casting methods and conditions can be used. If it is desired to further improve the strength of the aluminum alloy casting, one or more of the optional additive elements Si, Mg, Cu, and Zn can be added, and heat treatment can be performed under suitable conditions.

[0064] Although representative embodiments of the present invention have been described above, the present invention is not limited thereto, and various design changes can be made, all of which are included within the technical scope of the present invention.

[0065] Example

[0066] Examples

[0067] Raw materials prepared with the compositions shown in Examples 1 to 3 of Table 1 were inserted into a graphite crucible and melted in atmospheric conditions at 750°C, followed by slag removal using a slag-removing flux. Next, aluminum alloys with each composition were die-cast. The die-casting injection conditions were a low injection speed of 0.2 m / s, a high injection speed of 2.5 m / s, and a casting pressure of 80 MPa, resulting in plate-shaped aluminum alloy castings measuring 110 mm × 110 mm × 3 mm.

[0068] [Table 1]

[0069]

[0070] Comparative Examples

[0071] Except for using the compositions shown in Comparative Examples 1 to 7 in Table 1, die casting was performed in the same manner as in the examples, thereby obtaining comparative aluminum alloy castings.

[0072] Evaluate

[0073] (1) Conductivity

[0074] The conductivity of the aluminum alloy castings obtained in the examples and comparative examples was measured using a digital conductivity meter (Auto Sigma 3000 / DL) available from Hocking. The results are shown in Table 2. For the aluminum alloy castings that serve as examples of the present invention, high values ​​of 49% IACS or higher were obtained in all cases, even for die-cast materials that tend to have low conductivity. On the other hand, for the aluminum alloy castings that serve as comparative examples, the conductivity was less than 49% IACS in all cases.

[0075] (2) Tensile properties

[0076] The tensile properties of the aluminum alloy castings obtained in the examples and comparative examples were evaluated. Tensile specimens conforming to Japanese Industrial Standards (JIS) Z 2241 14B were cut from each aluminum alloy casting and tensile tests were conducted at a tensile speed of 5 mm / min. As a result of the tensile tests, the 0.2% yield strength of the aluminum alloy castings obtained in the examples was 70 MPa or greater in all cases. Furthermore, the aluminum alloy castings obtained in the examples also exhibited good elongation at break, with an elongation at break of 10% or greater in all cases, and 20% or greater in Example 3.

[0077] [Table 2]

[0078]

[0079] Based on the above results, in order to obtain relatively inexpensive aluminum alloy castings with both high conductivity and high strength, it is important to include Ni, Co, and Fe as essential additive elements and strictly control their content.

Claims

1. An aluminum alloy comprising Ni: greater than 2.0% by mass and less than 4.5% by mass Co: greater than 0.01% by mass and less than 1.00% by mass Fe: greater than 0.1% by mass and less than 2.5% by mass, and The balance consists of Al and unavoidable impurities.

2. The aluminum alloy according to claim 1, wherein... Ni: greater than 2.5% by mass and less than 4.0% by mass Co: greater than 0.10% by mass and less than 0.60% by mass Fe: greater than 0.2% by mass and less than 2.0% by mass.

3. The aluminum alloy according to claim 1, further comprising one or more of the following as optional additive elements, B: 0.001% by mass to 0.030% by mass, and Sr: 0.005% by mass to 0.030% by mass.

4. The aluminum alloy according to claim 1, further comprising one or more of the following as optional additive elements, Si: 0.1% to 0.5% by mass Mg: 0.1% to 0.5% by mass Cu: 0.1% to 0.5% by mass, and Zn: 0.1% by mass to 0.5% by mass.

5. An aluminum alloy casting comprising an aluminum alloy as described in any one of claims 1 to 4, and having an electrical conductivity of 49% or greater than the international annealed copper standard.

6. The aluminum alloy casting according to claim 5, wherein the 0.2% yield strength is 70 MPa or greater than 70 MPa.

7. The aluminum alloy casting according to claim 5, wherein the casting is a die-casting material.

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