Aluminum alloy and aluminum alloy casting

Abstract

To provide a relatively inexpensive aluminum alloy capable of developing high electrical conductivity and high strength, and a relatively inexpensive aluminum alloy casting comprising the aluminum alloy having both high electrical conductivity and high strength. The aluminum alloy contains Ni: 2.0% by mass to less than 4.5% by mass, Co: 0.01% by mass to less than 1.00% by mass, Fe: 0.1% by mass to less than 2.5% by mass, and the remainder is composed of Al and inevitable impurities.

Description

ALUMINUM ALLOY AND ALUMINUM ALLOY CASTING

[0001] The present invention relates to an aluminum alloy and an aluminum alloy casting which can be suitably used as materials for electrically conductive parts of electronic devices and the like.PRIOR ARTS

[0002] The conductivity (electrical conductivity) of aluminum is about 60% that of copper, but the specific gravity thereof is about one third, and it is possible to conduct twice as much current as copper of the same weight. In recent years, the application of aluminum alloys to uses that require light weight and high electrical conductivity has been considered, and there is a strong desire to improve the electrical conductivity of aluminum alloy materials.

[0003] However, in the past, improving the thermal and electrical conductivity of aluminum alloy materials has often been an issue, and it cannot be said that electrical conductivity has been sufficiently studied. On the other hand, for example, in Patent Literature 1 (Japanese Patent Unexamined Publication No. 2001-254135), in order to solve the problem “where providing an aluminum alloy increased in electric conductivity and thermal conductivity while maintaining its strength, in an Al-Fe-Ni alloy”, there is proposed “an aluminum alloy material containing 0.002 to 0.08 wt% of B, further containing 0.05 to 2.5 wt% of Fe and / or 0.05 to 2.5 wt% of Ni, the balance being composed of aluminum and unavoidable impurities”.

[0004] In the aluminum alloy material described in Patent Literature 1, in order to satisfy all of the properties among the properties required of an aluminum alloy, strength and thermal conductivity / electrical conductivity, which mutually strongly influence each other, particularly high thermal conductivity and electrical conductivity, as a result of various studies on the elements to be added to the alloy, it is said that it was found that a predetermined amount of element B is extremely effective.

[0005] Further, in Patent Literature 2 (Japanese Patent Unexamined Publication No. 2005-048206), in order to solve the problem “to provide a high strength and high electric conductivity aluminum alloy based composite material combining high strength and high electrical conductivity, and to provide its production method”, there is proposed “a high-strength, high-electrical conductivity aluminum alloy matrix composite material characterized by containing 0.1 to 10% by volume of carbon nanotubes having a diameter of 1 nm to 100 nm and an aspect ratio of 10 to 100 in a single-walled or multi-walled structure”.

[0006] In the high-strength, high-electrical conductivity aluminum alloy-based composite material described in Patent Literature 2, by containing carbon nanotubes in the aluminum alloy matrix, it is said that, due to the ultrafine reinforcement effect, an aluminum alloy matrix composite material having both high strength and high electrical conductivity can be obtained.

[0007] Patent Literature 1: Japanese Patent Unexamined Publication No. 2001-254135 Patent Literature 2: Japanese Patent Unexamined Publication No. 2005-048206

[0008] However, in the aluminum alloy material described in Patent Literature 1, since in addition to that B is an essential addition element, it is necessary to control the B content, it is difficult to obtain the aluminum alloy material easily and efficiently. Furthermore, the mechanical properties of the resulting aluminum alloy material are not disclosed, and it is not clear whether the aluminum alloy material has sufficient strength and the like or not.

[0009] Further, in aluminum alloy matrix composite material having the high strength and high electrical conductivity described in Patent Literature 2, it is necessary to disperse the carbon nanotubes in the aluminum matrix, but since the carbon nanotubes are typical materials which are difficult to be dispersed, the manufacturing process becomes extremely complicated. Further, since the carbon nanotubes themselves are expensive, an increase in the cost of the resulting composite material is inevitable. In addition, the region where carbon nanotubes aggregate becomes a starting point for fracture, making it difficult to ensure the reliability of the composite material. Furthermore, it is necessary to pay attention to the reaction between carbon nanotubes and aluminum.

[0010] In view of the problems in the prior art as described above, the purpose of the present invention is to provide a relatively inexpensive aluminum alloy capable of exhibiting high electrical conductivity and high strength, and a relatively inexpensive aluminum alloy casting having high electrical conductivity and high strength made of the aluminum alloy.

[0011] In order to achieve the above object, the present inventors have conducted extensive research on the composition and the like of aluminum alloys, and have found that in order to impart high electrical conductivity and high strength to aluminum alloy casting, it is effective that Ni, Co, and Fe are added as the essential addition elements, and the content of these elements are strictly controlled, and have reached the present invention.

[0012] That is, the present invention provides an aluminum alloy which contains: Ni: more than 2.0% by mass and less than 4.5% by mass, Co: more than 0.01% by mass and less than 1.00% by mass, Fe: more than 0.1% by mass and less than 2.5% by mass, and the balance is composed of Al and unavoidable impurities.

[0013] Ni, Co, and Fe all form intermetallic compounds and contribute to improve the strength of the aluminum alloy casting. On the other hand, the thus formed intermetallic compounds are relatively fine, and such a tendency can be observed on especially intermetallic compounds containing Ni and Co. As a result, deterioration in mechanical properties of aluminum alloy castings due to the formation of coarse intermetallic compounds can be suppressed.

[0014] Although, when adding 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, the mechanism where the electrical conductivity of the aluminum alloy casting increases is not necessarily clear, it is believed that by discharging Ni, Co, Fe, and extremely small amounts of impurity elements in the aluminum matrix as fine intermetallic compounds, the high electrical conductivity can be realized.

[0015] In the aluminum alloy of the present invention, it is preferable that the content of Ni is more than 2.5% by mass and less than 4.0% by mass, the content of Co is more than 0.10% by mass and less than 0.60% by mass, the content of Fe is more than 0.2% by mass and less than 2.0% by mass.

[0016] Further, in the aluminum alloy of the present invention, in addition, it is 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 an optional addition element. Since B has the effect of promoting refinement of the casting structure, and Sr has the effect of suppressing the coarsening of the crystallized substances by shortening the solidification time associated with supercooling, the mechanical properties of the aluminum alloy casting can be improved.

[0017] Further, transition metals such as Ti and V are elements that greatly reduce electrical conductivity in a solid solution state, and when these elements are present as unavoidable impurities, the electrical conductivity of the aluminum alloy casting decreases. On the other hand, since B forms the intermetallic compounds with the transition metals such as Ti and V, by adding 0.001 to 0.030% by mass of B to precipitate trace amounts of the transition metals (solid solution elements) which are present as unavoidable impurities, the electrical conductivity of the aluminum alloy casting can be improved.

[0018] Further, in the aluminum alloy of the present invention, in addition, it is preferable to contain one or more of Si: 0.1 to 0.5% by mass, and 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 as an optional addition element. Since these elements contribute to improving the strength of the aluminum alloy casting, the strength of the aluminum alloy casting can be adjusted as demand. When desiring to further improve the strength of the aluminum alloy casting, it may be heat-treated under appropriate conditions.

[0019] Further, the present invention also provides an aluminum alloy casting made of the aluminum alloy of the present invention, characterized in that the conductivity is 49% IACS or more. The essential addition elements in the aluminum alloy of the present invention are only Ni, Co, and Fe, and an aluminum alloy casting having a conductivity of 49% IACS or more can be easily and efficiently obtained.

[0020] In the aluminum alloy casting of the present invention, it is preferable that a 0.2% proof stress is 70 MPa or more. In addition to that the conductivity is 49% IACS or more, when the 0.2% proof stress is 70 MPa or more, it can be suitably used for conductive members that require high reliability.

[0021] Furthermore, it is preferable that the aluminum alloy casting of the present invention is a die-cast material. By using a die-casting material, aluminum alloy castings having a complicated shape can be mass-produced. Further, although die-cast materials generally have low electrical conductivity, by using the aluminum alloy of the present invention, electrical conductivity of 49% IACS or more can be ensured.Effects of the invention

[0022] According to the present invention, there can be provided a relatively inexpensive aluminum alloy capable of exhibiting high electrical conductivity and high strength, and a relatively inexpensive aluminum alloy casting having high electrical conductivity and high strength made of the aluminum alloy.Embodiments for achieving the invention

[0023] In the following, the aluminum alloy and aluminum alloy casting of the present invention will be explained in detail, but the present invention is not limited thereto.

[0024] 1. Aluminum alloy The aluminum alloy of the present invention is characterized by an optimized composition for the purpose of imparting high electrical conductivity and high strength to the aluminum alloy casting. More specifically, Ni, Co, and Fe are the essential additive elements, and the contents of these elements are strictly controlled. Each component will be explained in detail below.

[0025] (1) Essential addition elements Ni: more than 2.0% by mass and less than 4.5% by mass Ni disperses fine intermetallic compounds in the alloy and improves the strength of the aluminum alloy casting. Since the fine intermetallic compounds are uniformly dispersed, the amount of Ni in the matrix can be effectively reduced, and the strength can be improved while minimizing the adverse effect on the electrical conductivity of the aluminum alloy casting. The content of Ni is preferably set to more than 2.5% by mass and less than 4.0% by mass, and more preferably set to more than 3.0% by mass and less than 3.5% by mass.

[0026] Co: more than 0.01% by mass and less than 1.00% by mass Co disperses fine intermetallic compounds in the alloy and improves the strength of the aluminum alloy casting. Since the fine intermetallic compounds are uniformly dispersed, the amount of Co in the matrix can be effectively reduced, and the strength can be improved while minimizing the adverse effect on the electrical conductivity of the aluminum alloy casting. The Co content is preferably set to more than 0.1% by mass and less than 0.6% by mass, more preferably set to 0.15 to 0.3% by mass.

[0027] Fe: more than 0.1% by mass and less than 2.5% by mass Fe forms an intermetallic compound and improves the strength of the aluminum alloy casting, but when added in excess, the electrical conductivity of the aluminum alloy casting is reduced. When the addition amount of Fe is set to more than 0.1% by mass, the effect of improving the strength of aluminum alloy castings can be expressed, and when set to less than 2.5% by mass, the decrease in electrical conductivity can be suppressed. The amount of Fe added is preferably set to more than 0.2% by mass and less than 2.0% by mass, more preferably set to more than 0.3% by mass and less than 1.0% by mass.

[0028] (2) Optional addition elements In cases where adjustment of the strength or electrical conductivity of the aluminum alloy casting is necessary, the following elements may be added as occasion demands.

[0029] B: 0.001 to 0.030% by mass B has the effect of promoting refinement of the casting structure. It can be expected not only to improve the strength of the aluminum alloy casting due to refinement of the structure, but also to have the effect of improving the electrical conductivity of the aluminum alloy casting by promoting the precipitation of the intermetallic compounds caused by essential addition elements and emitting Ni, Co, Fe, and extremely small amounts of impurity elements in the aluminum matrix as fine intermetallic compounds. The addition amount of B is preferably set to 0.005 to 0.025% by mass, more preferably set to 0.010 to 0.020% by mass.

[0030] Sr: 0.005 to 0.030% by mass Sr has the effect of suppressing the coarsening of the crystallized substances by shortening the solidification time associated with supercooling, and the mechanical properties of the aluminum alloy casting can be improved. The addition amount of Sr is preferably set to 0.010 to 0.025% by mass, more preferably set to 0.015 to 0.020% by mass.

[0031] Si: 0.1 to 0.5% by mass By allowing Si to coexist with the essential addition elements Ni, Co, and Fe, the precipitation of the intermetallic compounds caused by Ni, Co, and Fe can be promoted. Due to this effect, it can be expected not only to improve the mechanical properties of the aluminum alloy casting, but also to improve the electrical conductivity of the aluminum alloy casting due to the reduction of Ni, Co, and Fe in the matrix. Furthermore, the addition of Si can also be expected to improve the flowability during the casting process.

[0032] Mg: 0.1 to 0.5% by mass Mg contributes to improving the strength of the aluminum alloy casting through solid solution strengthening and precipitation strengthening. When desiring to further improve the mechanical properties of the aluminum alloy casting, 0.1 to 0.5% by mass of Mg can be added.

[0033] Cu: 0.1 to 0.5% by mass Cu contributes to improving the strength of the aluminum alloy casting through solid solution strengthening and precipitation strengthening. When desiring to further improve the mechanical properties of the aluminum alloy casting, 0.1 to 0.5% by mass of Cu can be added.

[0034] Zn: 0.1 to 0.5% by mass Zn contributes to improving the strength of the aluminum alloy casting through solid solution strengthening and precipitation strengthening. When desiring to further improve the mechanical properties of the aluminum alloy casting, 0.1 to 0.5% by mass of Zn can be added.

[0035] Note that, it is allowable to contain unavoidable impurities within the range that the properties of the aluminum alloy casting of the present invention are not impaired.

[0036] 2. Aluminum alloy casting The aluminum alloy casting of the present invention is a high-electrical conductivity aluminum alloy casting made of the aluminum alloy of the present invention, and is characterized by having a conductivity of 49% IACS or more. The conductivity of the aluminum alloy casting is preferably 50% IACS or more, more preferably 51% IACS or more.

[0037] Further, it is preferable that the aluminum alloy casting of the present invention has a 0.2% proof stress of 70 MPa or more. In addition to that the conductivity is 49% IACS or more, since the 0.2% proof stress is 70 MPa or more, it can be suitably used for conductive members that require high reliability. The 0.2% proof stress of the aluminum alloy casting is preferably 75 MPa or more, more preferably 80 MPa or more.

[0038] Further, the aluminum alloy casting of the present invention preferably has an elongation at break of 10% or more in addition to the high 0.2% proof stress. When having good ductility and toughness, the aluminum alloy casting can be suitably used for conductive members that require high reliability. The elongation at break is preferably 15% or more, more preferably 20% or more.

[0039] The method for casting the aluminum alloy casting of the present invention is not particularly limited as long as the effects of the present invention are not impaired, and conventionally known die casting methods and gravity casting methods can be used, but it is preferable to use the die casting method. By using as a die-casting material, the aluminum alloy casting having a complicated shape can be mass-produced. Further, although die-cast materials generally have low electrical conductivity, when using the aluminum alloy of the present invention, the conductivity of 49% IACS or higher can be ensured.

[0040] Further, the casting conditions are not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known casting methods and casting conditions can be used. If it is desired to further improve the strength of the aluminum alloy casting, one or more of the optional addition elements Si, Mg, Cu and Zn may be added, and heat treatment may be performed under appropriate conditions.

[0041] Although representative embodiments of the present invention have been described above, the present invention is not limited to these, and various design changes are possible, and all such design changes are included in the technical scope of the present invention.EXAMPLE

[0042] ≪Example≫ Raw materials blended to have the compositions shown in Examples 1 to 3 in Table 1 were inserted into a graphite crucible, melted in the atmosphere at 750°C, and then subjected to a de-slagging treatment by using a de-slagging flux. Next, the aluminum alloys having each composition were subjected to die-casting. The injection conditions of the die-casting were a low speed of 0.2 m / s, a high speed of 2.5 m / s, and a casting pressure of 80 MPa to obtain a plate-shaped aluminum alloy casting of 110 mm x 110 mm x 3 mm.

[0043]

[0044] ≪Comparative Example≫ Die-casting was performed in the same manner as in Example except that the compositions shown in Comparative Examples 1 to 7 in Table 1 were used to obtain comparative aluminum alloy castings.Evaluation

[0045] (1) Conductivity The conductivity of the aluminum alloy castings obtained in Examples and Comparative Examples was measured by using a digital conductivity meter (Auto Sigma 3000 / DL) available from Hocking. The results obtained are shown in Table 2. With respect to the aluminum alloy castings that are 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 electrical conductivity. On the other hand, for the aluminum alloy castings as comparative examples, the electrical conductivities were less than 49% IACS in all cases.

[0046] (2) Tensile properties The tensile properties of the aluminum alloy castings obtained in Examples and Comparative Examples were evaluated. JIS Z 2241 14B tensile test pieces were cut out from each aluminum alloy casting and subjected to a tensile test at a tensile speed of 5 mm / min. As a result of the tensile test, the values of 0.2% proof stress of the aluminum alloy castings obtained in Examples were 70 MPa or more in all cases. Further, the aluminum alloy castings obtained in Examples also showed good elongation at break, which were 10% or more in all cases, and in Example 3, it was 20% or more.

[0047]

[0048] From the above results, in order to obtain relatively inexpensive aluminum alloy castings that have both high electrical conductivity and high strength, it is important to contain Ni, Co, and Fe as the essential additive elements, and to strictly control their contents.

Claims

1. An aluminum alloy which comprises: Ni: more than 2.0% by mass and less than 4.5% by mass, Co: more than 0.01% by mass and less than 1.00% by mass, Fe: more than 0.1% by mass and less than 2.5% by mass, and the balance is composed of Al and unavoidable impurities.

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

3. The aluminum alloy according to claim 1, further comprises, as an optional addition element, one or more of B: 0.001 to 0.030% by mass, and Sr: 0.005 to 0.030% by mass.

4. The aluminum alloy according to claim 1, further comprises, as an optional addition element, one or more of 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.

5. An aluminum alloy casting, which comprises the aluminum alloy according to any one of claims 1 to 4, and has a conductivity of 49% IACS or more.

6. The aluminum alloy casting according to claim 5, wherein a 0.2% proof stress is 70 MPa or more.

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

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