Aluminum alloys for die casting and aluminum alloy die casting materials

Abstract

This invention provides a non-heat-treatable aluminum alloy for die casting that has good castability and can impart excellent tensile properties (0.2% proof stress and elongation) and corrosion resistance to aluminum alloy die casting materials. It also provides an aluminum alloy die casting material that has excellent tensile properties (0.2% proof stress and elongation) and corrosion resistance. [Solution] The aluminum alloy for die casting is characterized by containing 3.7 to 9.0 mass% Mg, 0.8 to 1.7 mass% Mn, 0.001 to 0.1 mass% Be, and the balance being Al and unavoidable impurities. The Mn content is preferably 0.9 to 1.7 mass%, and the Mg content is preferably 4.7 to 9.0 mass%.

Description

[Technical field]

[0001] The present invention relates to a non-heat-treatable aluminum alloy for high toughness die casting. [Background technology]

[0002] In the field of automobiles and other vehicles, active efforts are being made to reduce the weight of vehicles in order to improve fuel efficiency and reduce the environmental impact, and aluminum alloys, which are lighter than steel, are attracting attention as a material for vehicle components. There are various methods for manufacturing vehicle components using aluminum alloys, but one method that is suitable for mass production of components at low cost is die casting.

[0003] When manufacturing difficult-to-shape components, compared to a method of forming components by applying plastic processing to wrought materials, the die casting method has an advantage in terms of cost because the components formed by the die casting method are close to the final shape at the time of casting, and the number of subsequent processing steps is reduced. However, in order to obtain the mechanical properties required for vehicle components from die casting materials, heat treatment is often required for the product after casting. Heat treatment includes solution treatment, which involves heating at high temperatures for a long time, and aging treatment, which involves heating and holding at a relatively low temperature. Both processes involve long hours of work, and the heating process incurs significant fuel costs. In addition, even after heat treatment, it is necessary to correct the distortion of the components caused by overheating and cooling, and there are many additional factors that increase costs. In light of these, it cannot be said that the cost reduction effect of using the die casting method in component manufacturing is fully realized. Therefore, non-heat-treatable alloys that do not require heat treatment after casting are considered important in that they can further reduce manufacturing costs.

[0004] In view of this, when selecting materials for vehicle components, there is a trade-off between the mechanical properties required for the target components and the manufacturing costs. In this situation, it has been desired to achieve high mechanical properties, particularly the strength and toughness required for vehicle components, in non-heat-treatable aluminum alloys for die casting, because this would lead to an expansion of the range of application of non-heat-treatable alloys and would have the effect of reducing vehicle manufacturing costs.

[0005] Non-heat-treatable aluminum alloys for die casting include Al-Si-Mg-Fe alloys, Al-Si-Cu-Mg alloys, and Al-Mg-Mn alloys. Among these, Al-Mg-Mn alloys in particular exhibit exceptionally high toughness.

[0006] For example, Patent Document 1 (Japanese Patent No. 1866145) discloses a corrosion-resistant aluminum alloy for die casting, which contains, by weight percent, 2.04% to 3.0% Mn, 5.0% to 8.0% Mg, and the remainder being Al and unavoidable impurities. In this invention, it is said that by adding a high concentration of Mn, about 2% by weight, the intermetallic compound Al6Mn is formed in the alloy, thereby improving the strength without impairing the corrosion resistance.

[0007] Patent Document 2 (JP Patent Publication 11-293375A) discloses an alloy composition for aluminum alloy die casting, which is characterized by the following: Mg: 2.5-7%, Mn: 0.2-1.0%, Ti: 0.05-0.2%, and the balance being Al and unavoidable impurities, with Fe and Si being less than 0.3% and Si: 0.5% or less, in terms of mass % concentrations. This invention focuses on the fact that Al-Mg compounds in the alloy improve toughness, while Mg-Si compounds and Al-Si-Fe compounds have a negative effect on toughness, and claims that a composition that brings high toughness to the alloy is obtained by adding Mg at a high concentration and restricting Fe and Si to low concentrations.

[0008] Furthermore, Patent Document 3 (JP Patent Publication 11-80875 A) discloses an aluminum alloy containing, by weight percent, 2.5-6.5% Mg, 0.5-1.4% Mn, less than 0.5% Si, less than 0.5% Fe, less than 0.15% Ti, and the balance being aluminum and unavoidable impurities. This invention claims that by adopting this alloy composition, it is possible to provide the vehicle frame members with weldability, strength, elongation, and resistance to corrosion and stress corrosion suitable for the vehicle frame members. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 1866145 [Patent Document 2] Japanese Patent Application Publication No. 11-293375 [Patent Document 3] Japanese Patent Application Publication No. 11-80875 Summary of the Invention [Problem to be solved by the invention]

[0010] Aluminum alloys used in structural components have always been required to be high strength and high toughness materials, but in recent years, there has been a growing momentum for vehicle weight reduction, and it is becoming difficult for alloys that have traditionally been used for die casting to meet the demand for improved strength and toughness.

[0011] In the samples No. 1 to No. 7 in the examples of the above Patent Document 1, relatively high concentrations of Mg and Mn are added, and as a result, many samples show relatively high values ​​of yield strength, but the elongation remains at around 10%. In addition, in the composition disclosed as Example 2 of the above Patent Document 2, the Mn concentration is low, so although it has relatively good elongation, it does not obtain the yield strength required for vehicle members. In the other examples, there is no example that has sufficient yield strength and elongation, and there is variation in elongation due to the casting quality, which is thought to be due to the low content of Mn, which is effective in improving castability. Furthermore, in the compositions disclosed in the examples of the above Patent Document 3, there is no example that satisfies both the yield strength and elongation required for aluminum alloys for recent vehicle members.

[0012] On the other hand, as the range of application of aluminum alloys to vehicle components expands, there is an increasing tendency for aluminum alloys to be used in components exposed to the outside, or in parts that may catch the consumer's eye even if they are not directly visible to the outside, where corrosion resistance and beauty of the component surface are as important as strength, and therefore there is a demand for the development of alloys with excellent corrosion resistance and luster. However, the aluminum alloys of Patent Documents 1 to 3 do not fully take these properties into consideration.

[0013] In view of the problems in the prior art as described above, an object of the present invention is to provide a non-heat-treatable aluminum alloy for die casting that has good castability and can impart excellent tensile properties (0.2% proof stress and elongation) and corrosion resistance to aluminum alloy die casting materials. Another object of the present invention is to provide an aluminum alloy die casting material that has excellent tensile properties (0.2% proof stress and elongation) and corrosion resistance. In the following, 0.2% proof stress may be simply referred to as proof stress. [Means for solving the problem]

[0014] In order to achieve the above object, the present inventors have conducted extensive research into aluminum alloys for die casting and aluminum alloy die casting materials, and as a result have discovered that, in Al-Mg-Mn based alloys, it is extremely effective to strictly control the amounts of Mg and Mn added, and have arrived at the present invention.

[0015] That is, the present invention provides: Mg: 3.7~9.0% by mass, Mn: 0.8~1.7% by mass, Be: 0.001 to 0.1 mass%, the balance being Al and unavoidable impurities; The present invention provides an aluminum alloy for die casting, characterized by:

[0016] In the aluminum alloy for die casting of the present invention, the yield strength of the aluminum alloy is improved by adding Mg and Mn. Also, the addition of an appropriate amount of Mn suppresses the sticking of the molten metal to the die. On the other hand, the upper limit of the amount of Mg added is set to suppress the deterioration of castability (die castability) and ductility, and the upper limit of the amount of Mn added is set to suppress the generation of coarse crystals of Al-Mn compounds that cause the deterioration of ductility.

[0017] Here, the natural electrode potential of the Al-Mn compound is the same as that of Al (parent phase), and the addition of Mn does not reduce the corrosion resistance of the die-casting aluminum alloy.Al-Mg systems are known to have good corrosion resistance, and the effect of adding Mg on the corrosion resistance of the die-casting aluminum alloy is small, so good corrosion resistance can be maintained.

[0018] In terms of brilliance, pure Al is the best, but when Mn is added in an amount up to about 2.0 mass%, the area ratio of Al-Mn compounds hardly increases, and the effect on brilliance can be minimized. In addition, Al-Mg systems are known to have good brilliance, and have little adverse effect on the brilliance of aluminum alloys for die casting.

[0019] In the aluminum alloy for die casting of the present invention, the Mn content is preferably 0.9 to 1.7 mass%, and more preferably 1.2 to 1.7 mass%. Furthermore, the upper limit of the Mn content is preferably 1.65 mass%, and more preferably 1.60 mass%. Moreover, the Mg content is preferably 4.7 to 9.0 mass%, and more preferably 5.2 to 6.5 mass%, and most preferably 5.5 to 6.0 mass%. By setting the Mn and Mg contents within these ranges, the above-mentioned effects can be obtained more reliably.

[0020] In the die-casting aluminum alloy of the present invention, it is preferable that the Si content of the inevitable impurities is restricted to 0.3% by mass or less, which can suppress the formation of brittle Mg2Si compounds that cause a decrease in toughness.

[0021] In the die-casting aluminum alloy of the present invention, it is preferable that the content of Fe among the inevitable impurities is restricted to 0.4% by mass or less, which can suppress the formation of brittle Al-Mn-Fe compounds that cause a decrease in toughness.

[0022] In addition, the aluminum alloy for die casting of the present invention preferably further contains, as optional added elements, Ti: 0.001 to 1.0 mass% and / or B: 0.0001 to 0.1 mass%. The addition of Ti and B refines the structure and can improve the toughness of the aluminum alloy. On the other hand, the upper limit of the added amount is specified to suppress the formation of coarse crystals that reduce toughness.

[0023] The present invention also provides an aluminum alloy die-cast material made of the aluminum alloy for die-casting of the present invention, characterized in that it has tensile properties of a 0.2% yield strength of 140 MPa or more and an elongation of 11% or more.

[0024] The aluminum alloy die-cast material of the present invention is a die-cast material made of the aluminum alloy for die-casting of the present invention, and therefore has both high levels of yield strength and elongation. Here, the 0.2% yield strength is preferably 150 MPa or more, and more preferably 160 MPa or more. The elongation is preferably 12% or more, more preferably 15% or more, and most preferably 20% or more.

[0025] In the aluminum alloy die-cast material of the present invention, the primary crystal Al-Mn compound preferably has a maximum longitudinal grain size of 150 μm or less. By making the primary crystal Al-Mn compound have a maximum longitudinal grain size of 150 μm or less, excellent ductility and corrosion resistance are achieved. Here, the primary crystal Al-Mn compound preferably has a maximum longitudinal grain size of 100 μm or less, and more preferably has a maximum longitudinal grain size of 50 μm or less. Effect of the Invention

[0026] According to the present invention, it is possible to provide a non-heat-treatable aluminum alloy for die casting that has good castability and can impart excellent tensile properties (0.2% proof stress and elongation) and corrosion resistance to an aluminum alloy die casting material. Also, according to the present invention, it is possible to provide an aluminum alloy die casting material that has excellent tensile properties (0.2% proof stress and elongation) and corrosion resistance. [Brief description of the drawings]

[0027] [Figure 1] 1 is an optical microscope photograph of a cross section of a test piece obtained in Example 1. [Diagram 2] 1 is an optical microscope photograph of a cross section of a test piece obtained in Example 2. [Diagram 3] 2 is an optical microscope photograph of a cross section of a test piece obtained in Comparative Example 1. [Figure 4] 1 is an optical microscope photograph of a cross section of a test piece obtained in Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Representative embodiments of the aluminum alloy for die casting and the aluminum alloy die casting material of the present invention will be described in detail below, but the present invention is not limited to these.

[0029] 1. Aluminum alloys for die casting The aluminum alloy for die casting of the present invention is characterized in that it contains 3.7 to 9.0 mass% of Mg, 0.8 to 1.7 mass% of Mn, and the balance being Al and unavoidable impurities. Each component will be described in detail below.

[0030] Mg:3.7~9.0% by mass Mg has the effect of improving the yield strength mainly by dissolving in the matrix of the alloy. However, when added at a high concentration, the viscosity of the molten metal increases, and the oxide film formed on the surface of the molten metal during casting hinders the flow of the molten metal, making it difficult to cast with good quality. In order to prevent a decrease in elongation due to this, the upper limit of the Mg content must be 9.0 mass%. On the other hand, if the Mg content is low, the yield strength targeted in the present invention cannot be satisfied, so the lower limit is set to 3.7 mass%. In order to achieve a higher level of both yield strength and elongation, the Mg content is preferably 4.7 to 9.0 mass%, more preferably 5.2 to 6.5 mass%, and most preferably 5.5 to 6.0 mass%.

[0031] Mn:0.8~1.7% by mass Mn has the effect of improving the yield strength mainly by dissolving in the matrix. Although the effect of dissolving Mn on toughness is small, when the amount of Mn added increases and coarse crystals of Al-Mn-based compounds appear, they become the starting point of fracture, and a decrease in elongation is observed. Therefore, the upper limit of the Mn content must be 1.7 mass%. In addition, Mn has an advantageous effect on castability, such as improving the seizure of the molten metal to the mold during die casting. Therefore, if the Mn content is below 0.8 mass%, seizure cannot be prevented and it becomes difficult to release the mold after casting, so the lower limit of the content must be 0.8 mass%. The preferred Mn content for achieving both castability and elongation is 0.9 to 1.7 mass%, and more preferably 1.2 to 1.7 mass%. In addition, from the viewpoint of imparting excellent brilliance to the aluminum alloy for die casting, the added amount of Mn is 1.7 mass% or less. The upper limit of the Mn content is preferably set to 1.65 mass %, and more preferably set to 1.60 mass %.

[0032] Si: 0.3% by mass or less In the composition of the die-casting aluminum alloy of the present invention, when Si is added, a brittle Mg2Si compound is formed, and the toughness is reduced. Therefore, among the unavoidable impurities, the content of Si is preferably restricted to 0.3 mass% or less, and more preferably 0.2 mass% or less.

[0033] Fe: 0.4% by mass or less In the composition of the die-casting aluminum alloy of the present invention, when Fe is added, a brittle Al-Mn-Fe compound is formed, and the toughness is reduced. Therefore, among the inevitable impurities, the content of Fe is preferably restricted to 0.4 mass% or less, and more preferably to 0.3 mass% or less. In addition, the addition of Fe reduces the corrosion resistance of the die-casting aluminum alloy, so from this viewpoint, the added amount is restricted to 0.4 mass% or less.

[0034] Ti:0.001~1.0% by mass Ti is an optional additive element, and is preferably added in an amount of 0.001 to 1.0 mass%. Ti improves the toughness of the aluminum alloy by refining the structure, and also has the effect of preventing casting cracks due to this. If it is contained in an amount of less than 0.001 mass%, the effect is small, and if it is contained in an amount of more than 1.0 mass%, coarse crystals of Al-Ti compounds are formed, which adversely affects the toughness, so the amount of addition is limited to the above range.

[0035] B:0.0001~0.1% by mass B is an optional additive element, and is preferably added in an amount of 0.0001 to 0.1 mass%. B improves the toughness of the aluminum alloy by refining the structure, and also has the effect of preventing casting cracks due to this. If it is less than 0.0001 mass%, the effect is small, and if it is contained in an amount exceeding 0.1 mass%, the effect is not improved, so the amount added is limited to the above range.

[0036] Be:0.001~0.1% by mass Be is effective in preventing Mg depletion and can be used as an optional additive element. When Be is added, if it is less than 0.001 mass%, the effect of preventing Mg depletion is insufficient, and even if it is added in excess of 0.1 mass%, the effect of preventing Mg depletion is already sufficient, so that adding Be in excess of 0.1 mass% will increase the cost.

[0037] Other than the above elements, elements that can be added include Cr, Zn, V, Ni, Zr, Sr, Cu, Mo, Sc, Y, Ca, and Ba. These elements have little effect on toughness or corrosion resistance and can be added if the amounts are Cr: 0.5 mass% or less, Zn: 1.0 mass% or less, V: 0.5 mass% or less, Ni: 0.5 mass% or less, Zr: 0.5 mass% or less, Sr: 0.5 mass% or less, Cu: 0.5 mass% or less, Mo: 0.5 mass% or less, Sc: 0.5 mass% or less, Y: 0.5 mass% or less, Ca: 0.5 mass% or less, and Ba: 0.5 mass% or less.

[0038] Cr, Zn, V, Cu, Mo, Sc, and Y are expected to have the effect of improving the strength of aluminum alloys by forming a solid solution mainly in the aluminum alloy matrix, Ni is expected to improve castability, including preventing the molten metal from sticking to the mold, Zr and Sr are expected to have the effect of improving toughness and casting crack resistance by refining the structure, and Ca and Ba are expected to have the effect of preventing the oxidative depletion of elements in the molten metal.

[0039] 2. Manufacturing method of aluminum alloy for die casting The method for producing the aluminum alloy for die casting of the present invention having the above composition will be described in detail below.

[0040] (1) Melting of molten aluminum alloy In the manufacturing process of aluminum alloys, oxidation depletion of elements occurs in the high-temperature alloy melt. The degree of oxidation progresses differently for each contained element, and the more reactive the element is, the more rapidly the oxidation depletion progresses. Here, Mg contained in the components of the aluminum alloy of the present invention is a highly reactive element, and when the molten metal containing Mg is overheated, magnesium oxide forms on the molten metal surface, and the Mg concentration in the molten metal decreases. It is possible to add extra Mg in anticipation of depletion, but there are many undesirable points in operation, such as the difficulty of adjusting the concentration due to the Mg content decreasing every moment, and the additional cost required to add extra Mg. It is known that this oxidation depletion of Mg can be improved by adding 10 ppm or more of Be, and it is preferable to add Be in terms of operation.

[0041] When adjusting the composition of the molten metal, it is preferable to add the element having the effect of preventing oxidation loss to the molten metal before adding Mg, because if Mg is added first, a considerable amount of Mg loss will occur during the period between the addition of Mg and the addition of the element having the effect of preventing oxidation loss.

[0042] (2) Casting pretreatment Molten metal produced in an air atmosphere contains impurities such as hydrogen gas and oxides. If this molten metal is cast as is, it will appear as defects such as porosity during solidification, impairing the toughness of the resulting parts. In order to prevent these defects, it is effective to perform bubbling with an inert gas such as nitrogen or argon gas after the molten metal is produced and before die casting. When the inert gas is supplied from the bottom of the molten metal, it has the effect of capturing the hydrogen gas and impurities in the molten metal and removing them to the surface of the molten metal as it rises.

[0043] 3.Aluminum alloy die casting material The aluminum alloy die-cast material of the present invention is a die-cast material made of the aluminum alloy for die-casting of the present invention, and is characterized by having tensile properties such as a 0.2% yield strength of 140 MPa or more and an elongation of 11% or more.

[0044] The excellent 0.2% yield strength and elongation are basically achieved by rigorously optimizing the composition, and the tensile properties are obtained regardless of the shape and size of the aluminum alloy die-cast material. Here, the 0.2% yield strength is preferably 150 MPa or more, and more preferably 160 MPa or more. The elongation is preferably 12% or more, more preferably 15% or more, and most preferably 20% or more.

[0045] In the aluminum alloy die-cast material of the present invention, the primary crystal Al-Mn compound preferably has a maximum longitudinal grain size of 150 μm or less. By making the primary crystal Al-Mn compound have a maximum longitudinal grain size of 150 μm or less, excellent ductility and corrosion resistance are realized. Here, the primary crystal Al-Mn compound preferably has a maximum longitudinal grain size of 100 μm or less, and more preferably has a maximum longitudinal grain size of 50 μm or less.

[0046] The method for determining the size of the primary crystal Al-Mn-based compound is not particularly limited, and may be measured by various conventionally known methods. For example, the size of the primary crystal Al-Mn-based compound may be calculated by cutting an aluminum alloy die-cast material, observing the obtained cross-sectional sample with an optical microscope or a scanning electron microscope, and calculating the size of the primary crystal Al-Mn-based compound. In this case, the size of the primary crystal Al-Mn-based compound is measured so as to be large, and for example, when the aspect ratio of the primary crystal Al-Mn-based compound is large, the size in the longitudinal direction is measured. Note that the cross-sectional sample may be subjected to mechanical polishing, buff polishing, electrolytic polishing, etching, etc. depending on the observation method.

[0047] As long as the effects of the present invention are not impaired, the shape and size of the die-cast material are not particularly limited, and it can be used as various conventionally known members, such as body structural members such as frame members.

[0048] 4. Manufacturing method of aluminum alloy die casting materials The aluminum alloy die-cast material of the present invention is a die-cast material made of the aluminum alloy for die-casting of the present invention and has the above-mentioned composition. Hereinafter, a method for producing the aluminum alloy for die-casting of the present invention will be described in detail.

[0049] In the composition of the aluminum alloy for die casting of the present invention, since elements for the purpose of solid solution strengthening are included, attention must be paid to the cooling rate in the production of the die casting material. If the cooling rate during casting is slow, Mg and Mn cannot be sufficiently solid-dissolved in the matrix, so it is preferable to ensure a cooling rate of 50°C / sec or more during casting. In this case, the casting pressure is preferably set to 50 MPa to 150 MPa.

[0050] In addition, when manufacturing components using die casting, because the molten metal is poured into the mold at high pressure and high speed, air in the mold may get caught in the molten metal, or solidification shrinkage may cause casting defects such as air bubbles and cavities in the component. If many such defects exist, it will have a negative effect on the toughness of the component, so it is preferable to take measures to reduce these defects when casting.

[0051] For example, vacuum die casting, which evacuates the air from within the mold cavity before casting to create a vacuum state and prevents air from being entrained in the molten metal, and pore-free die casting (PF: Pore Free, PF die casting), which replaces the air in the mold cavity with an active gas, such as oxygen gas, before pouring the molten metal, are effective. With vacuum die casting, the amount of air present in the cavity is small to begin with, so casting defects can be mitigated, and with pore-free die casting, the active gas, such as oxygen, filled in the cavity reacts with the molten aluminum to form a fine oxide film (Al2O3) that disperses within the component, suppressing adverse effects on the component properties.

[0052] The alloy system to which the die casting aluminum alloy of the present invention belongs, i.e., Al-Mg-Mn alloys, differs from Al-Si alloys that have been widely used as conventional die casting alloys in that Si, which is effective in improving castability, is not actively added (or the content is regulated), and therefore, in some cases, the alloy system has the problem of poor fluidity.

[0053] However, in the vacuum die casting method, the inside of the die cavity is under negative pressure when pouring, which promotes the filling of the molten metal into the die, and in the case of the non-porous die casting method, the active gas filled in the die cavity reacts with the molten aluminum alloy, which creates a negative pressure in the cavity as in the vacuum die casting method, improving the filling of the molten metal into the die, resulting in the same effect as improving the flow of the alloy. Therefore, in the Al-Mg-Mn alloy, which was previously considered difficult to cast with good quality by the die casting method and which was improved in the prior art by adding high concentrations of Mn, the aluminum alloy for die casting of the present invention can be cast with good quality even with the Mn concentration in the composition, and further, the effect of improving elongation due to the low Mn concentration can be expressed.

[0054] In addition, the aluminum alloy for die casting of the present invention is a non-heat-treated aluminum alloy, and therefore does not require heat treatment of the cast product to obtain the mechanical properties required for vehicle components in the die casting material, which results in reduced costs associated with the heat treatment process and the correction of distortions caused by the heat treatment process.

[0055] Representative embodiments of the present invention have been described above, but the present invention is not limited to these, and various design modifications are possible, all of which are included in the technical scope of the present invention. EXAMPLES

[0056] Example 1 The melted material was adjusted to have the composition (charged value) shown in Table 1 as Example 1, and a Lansley test piece was manufactured. Here, the melting temperature and casting temperature were "liquidus temperature + 100°C", and the Lansley mold temperature was "150±50°C". The composition of the Lansley test piece obtained was measured by emission spectroscopy, and the obtained results (measured values) are also shown in Table 1. The values ​​in Table 1 are in mass%.

[0057] [Table 1]

[0058] The cross section of the Lansley test piece was mirror-polished and the size of the primary crystals of Al-Mn compounds was measured by optical microscope observation, the largest of which was 33 μm. The optical microscope photograph is shown in Figure 1.

[0059] The Lansley test specimen was processed into the shape of a JIS standard CT71 type tensile test specimen and subjected to a tensile test at room temperature. The results are shown in Table 2. The tensile test was performed three times in total, and although one specimen had a 0.2% yield strength of 136 MPa, the others had a 0.2% yield strength of 140 MPa or more and an elongation of 11% or more (the average 0.2% yield strength was 140 MPa).

[0060] [Table 2]

[0061] Example 2 A Ransley test piece was obtained in the same manner as in Example 1, except that the melting material was adjusted to have the composition shown in Example 2 in Table 1. The composition of the Ransley test piece was measured in the same manner as in Example 1, and the obtained results are shown in Table 1.

[0062] Furthermore, the size of the primary crystal Al-Mn compounds was measured in the same manner as in Example 1, and the largest was 37 μm. An optical microscope photograph is shown in FIG.

[0063] Further, a tensile test was carried out in the same manner as in Example 1, and the results are shown in Table 2. All the test pieces had a 0.2% yield strength of 140 MPa or more and an elongation of 11% or more.

[0064] Example 3 Aluminum alloys having the compositions shown in Table 3 were melted and then die-cast to obtain aluminum alloy die-cast materials. The values ​​in Table 3 are in mass % and are the results of emission spectroscopic analysis.

[0065] [Table 3]

[0066] The die casting method used was non-porous die casting, and the die casting material was produced. The dimensions of the die used were 110mm x 110mm x 3mm, and the casting pressure during die casting was 120MPa, the molten metal temperature was 730℃, and the die temperature was 170℃. The release agent used was water-soluble.

[0067] A JIS-Z2241 No. 14B test piece was taken from the obtained aluminum alloy die-cast material and subjected to a tensile test at room temperature, which showed that the 0.2% yield strength was 174 MPa and the elongation was 21%. From these results, it was confirmed that the aluminum alloy die-cast material obtained from the aluminum alloy for die-casting of the present invention has a high yield strength of 170 MPa or more and an elongation of more than 20%, and can be suitably used, for example, for automobile parts.

[0068] Example 4 Aluminum alloys having the compositions shown in Table 4 were melted and then die-cast in the same manner as in Example 3 to obtain aluminum alloy die-cast materials. The values ​​in Table 4 are in mass % and are the results of emission spectroscopic analysis.

[0069] [Table 4]

[0070] A No. 14B test piece as specified in JIS-Z2241 was taken from the obtained aluminum alloy die-cast material and subjected to a tensile test at room temperature, whereupon the 0.2% yield strength was 140 MPa and the elongation was 14%.

[0071] Example 5 Aluminum alloys having the compositions shown in Table 5 were melted and then die-cast aluminum alloy materials were obtained by the same die-casting as in Example 3. The values ​​in Table 5 are in mass % and are the results of emission spectroscopic analysis.

[0072] [Table 5]

[0073] A No. 14B test piece as specified in JIS-Z2241 was taken from the obtained aluminum alloy die-cast material and subjected to a tensile test at room temperature, whereupon the 0.2% yield strength was 152 MPa and the elongation was 12%.

[0074] Example 6 Aluminum alloys having the compositions shown in Table 6 were melted and then die-cast aluminum alloy materials were obtained by the same die-casting method as in Example 3. The values ​​in Table 6 are in mass % and are the results of emission spectroscopic analysis.

[0075] [Table 6]

[0076] A No. 14B test piece as specified in JIS-Z2241 was taken from the obtained aluminum alloy die-cast material and subjected to a tensile test at room temperature, whereupon the 0.2% yield strength was 155 MPa and the elongation was 13%.

[0077] Comparative Example 1 A Ransley test piece was obtained in the same manner as in Example 1, except that the melting material was adjusted to have the composition shown in Table 1 as Comparative Example 1. The composition of the Ransley test piece was measured in the same manner as in Example 1, and the obtained results are shown in Table 1.

[0078] Furthermore, the size of the primary crystal Al-Mn compounds was measured in the same manner as in Example 1, and the largest was 62 μm. An optical microscope photograph is shown in FIG.

[0079] Further, a tensile test was carried out in the same manner as in Example 1, and the results are shown in Table 2. Although the 0.2% proof stress shows a high value, there are cases where the elongation is less than 10%.

[0080] Comparative Example 2 A Ransley test piece was obtained in the same manner as in Example 1, except that the melting material was adjusted to have the composition shown in Comparative Example 2 in Table 1. The composition of the Ransley test piece was measured in the same manner as in Example 1, and the obtained results are shown in Table 1.

[0081] Furthermore, the size of the primary crystal Al-Mn compounds was measured in the same manner as in Example 1, and the largest was 254 μm. An optical microscope photograph is shown in FIG.

[0082] In addition, tensile tests were performed in the same manner as in Example 1, and the results are shown in Table 2. Although the 0.2% proof stress shows a high value, the elongation is less than 10% in all the test pieces. It is considered that the elongation is significantly reduced due to the coarsening of the primary crystal Al-Mn based compounds.

[0083] Comparative Example 3 Aluminum alloys having the compositions shown in Table 7 were melted and then die-cast into aluminum alloy die-cast materials by the same method as in Example 3. The values ​​in Table 7 are in mass % and are the results of emission spectroscopic analysis.

[0084] [Table 7]

[0085] A No. 14B test piece as specified in JIS-Z2241 was taken from the obtained aluminum alloy die-cast material and subjected to a tensile test at room temperature, whereupon the 0.2% yield strength was 126 MPa and the elongation was 19%.

[0086] Comparative Example 4 Aluminum alloys having the compositions shown in Table 8 were melted and then die-cast aluminum alloy materials were obtained by the same die-casting method as in Example 3. The values ​​in Table 8 are in mass % and are the results of emission spectroscopic analysis.

[0087] [Table 8]

[0088] A No. 14B test piece as specified in JIS-Z2241 was taken from the obtained aluminum alloy die-cast material and subjected to a tensile test at room temperature, whereupon the 0.2% yield strength was 137 MPa and the elongation was 15%.

[0089] Comparative Example 5 Aluminum alloys having the compositions shown in Table 9 were melted and then die-cast in the same manner as in Example 3 to obtain aluminum alloy die-cast materials. The values ​​in Table 9 are in mass % and are the results of emission spectroscopic analysis.

[0090] [Table 9]

[0091] A No. 14B test piece as specified in JIS-Z2241 was taken from the obtained aluminum alloy die-cast material and subjected to a tensile test at room temperature, whereupon the 0.2% yield strength was 137 MPa and the elongation was 15%.

[0092] From the above results, when the Mg content is 3.7-9.0 mass% and the Mn content is 0.8-1.7 mass%, a 0.2% yield strength of 140 MPa or more and an elongation of 11% or more are obtained. When the Mg content is 4.7-9.0 mass% and the Mn content is 0.9-1.7 mass%, a 0.2% yield strength of 150 MPa or more and an elongation of 12% or more are obtained. Furthermore, when the Mg content is 5.2-6.5 mass% and the Mn content is 1.2-1.7 mass%, a 0.2% yield strength of 160 MPa or more and an elongation of 15% or more are obtained.

Claims

1. Mg: 4.7 to 9.0% by mass, Mn: 0.8 to 1.7% by mass, Be: 0.001 to 0.004 mass%, The balance is Al and inevitable impurities, Among the inevitable impurities, the content of Si is restricted to 0.3 mass% or less, Among the inevitable impurities, the content of Fe is restricted to 0.4 mass% or less; An aluminum alloy for die casting characterized by:

2. It is a non-heat-treatable alloy.

2. The aluminum alloy for die casting according to claim 1,

3. A die casting material made of the aluminum alloy for die casting according to claim 1 or 2, Having tensile properties of 0.2% yield strength of 140 MPa or more and elongation of 11% or more; Aluminum alloy die casting material characterized by:

4. The maximum grain size of the primary crystal Al-Mn compound in the longitudinal direction is 150 μm or less; The aluminum alloy die-cast material according to claim 3,

5. A method of manufacturing a die-cast aluminum alloy according to claim 1, replacing the air in a cavity of a die with an active gas, and then pouring the molten metal into the die to obtain an aluminum alloy die-cast material; A manufacturing method of an aluminum alloy die casting material, characterized by the above.

6. The aluminum alloy die-cast material is not subjected to heat treatment; 6. The method for producing an aluminum alloy die-cast material according to claim 5,

Images