ALUMINUM ALLOY FOR DIE CASTING AND DIE CAST ALUMINUM ALLOY MATERIAL

Abstract

The present invention provides a non-heat-treatable aluminum alloy for die casting, which can exhibit good castability and is able to confer excellent tensile characteristics (0.2% proof stress and elongation) and excellent corrosion resistance on die cast aluminum alloy materials. Also, the present invention provides a die cast aluminum alloy material having excellent tensile characteristics (0.2% proof stress and elongation) and excellent corrosion resistance. An aluminum alloy for die casting of the present invention comprises Mg: 3.7 to 9.0% by mass and Mn: 0.8 to 1.7% by mass, with the balance being Al and unavoidable impurities. It is preferable that the Mn content is 0.9 to 1.7% by mass and the Mg content is 4.7 to 9.0% by mass.

Claims

1. An aluminum alloy for die casting, comprising Mg: 3.7 to 9.0% by mass and Mn: 0.8 to 1.7% by mass, with the balance being Al and unavoidable impurities.

2. The aluminum alloy for die casting according to claim 1, wherein the Mg content is 4.7 to 9.0% by mass, and the Mn content is 0.9 to 1.7% by mass.

3. The aluminum alloy for die casting according to claim 1, wherein the Mg content is 5.2 to 6.5% by mass, and the Mn content is 1.2 to 1.7% by mass.

4. The aluminum alloy for die casting according to claim 1, wherein the Si content in the unavoidable impurities is regulated to 0.3% by mass or less.

5. The aluminum alloy for die casting according to claim 1, wherein the Fe content in the unavoidable impurities is regulated to 0.4% by mass or less.

6. The aluminum alloy for die casting according to claim 1, further comprising Ti: 0.001 to 1.0% by mass and/or B: 0.0001 to 0.1% by mass as the optional additive element.

7. A die cast aluminum alloy material made of aluminum alloy for die casting according to claim 1, which has a tensile property of 0.2% proof stress of 140 MPa or more and elongation of 11% or more.

8. The die cast aluminum alloy material according to claim 7, wherein the maximum particle size of the primary crystal Al—Mn-based compound in the longitudinal direction is 150 μm or less.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 shows an optical micrograph of the cross section of the test piece obtained in Example 1.

[0030] FIG. 2 shows an optical micrograph of the cross section of the test piece obtained in Example 2.

[0031] FIG. 3 shows an optical micrograph of the cross section of the test piece obtained in Comparative Example 1.

[0032] FIG. 4 shows an optical micrograph of the cross section of the test piece obtained in Comparative Example 2.

EMBODIMENTS FOR ACHIEVING THE INVENTION

[0033] In the following, typical embodiments of the aluminum alloy for die casting and the die cast aluminum alloy material according to the present invention will be described in detail, but the present invention is not limited to these.

1. Aluminum Alloy for Die Casting

[0034] The aluminum alloy for die casting of the present invention is composed of the aluminum alloy for die casting which contains Mg: 3.7 to 9.0% by mass and Mn: 0.8 to 1.7% by mass, with the balance being Al and unavoidable impurities. In the following, each component will be described in detail.

Mg: 3.7 to 9.0% by Mass

[0035] Mg has the effect of improving the proof stress by mainly solid-solved in the matrix of the alloy. However, when added in a high concentration, the viscosity of the molten metal becomes high, and the oxide film formed on the surface of the molten metal during casting inhibits the flow of the molten metal, which makes high quality casting difficult. In order to prevent the decrease in elongation due to this reason, it is necessary to set the upper limit of the Mg content to 9.0% by mass. On the other hand, when the Mg content is low, the proof stress targeted in the present invention cannot be satisfied, so the lower limit is set to 3.7% by mass. In order to achieve both strength and elongation at a higher level, the Mg content is preferably 4.7 to 9.0% by mass, more preferably 5.2 to 6.5% by mass, most preferably 5.5 to 6.0% by mass.

Mn: 0.8 to 1.7% by Mass

[0036] Mn has the effect of improving proof stress by mainly being dissolved in the matrix. Although the effect of the solid solution of Mn on the toughness is small, when the addition amount increases and coarse crystals of the Al—Mn-based compound appear, the coarse crystal becomes the starting point of fracture and the decrease in elongation is observed. Therefore, it is necessary to set the upper limit of the Mn content to 1.7% by mass. Further, Mn has an advantageous effect on castability, such as improving the seizure of the molten metal into the mold during die casting. Therefore, when the Mn content is less than 0.8% by mass, seizure cannot be completely prevented and mold release after casting becomes difficult, and thus it is necessary to set the lower limit of the content to 0.8% by mass. The preferable Mn content for achieving both castability and elongation is 0.9 to 1.7% by mass, and the more preferable content is 1.2 to 1.7% by mass. In addition, the addition amount of Mn is 1.7% by mass or less from the viewpoint of imparting excellent brilliance to the die cast aluminum alloy. Further, the upper limit of the Mn content is preferably 1.65% by mass, more preferably 1.60% by mass.

Si: 0.3% by Mass or Less

[0037] In the composition of the aluminum alloy for die casting of the present invention, when Si is added, a fragile Mg.sub.2Si compound is formed and the toughness is decreased. Therefore, among the unavoidable impurities, the Si content is preferably regulated to 0.3% by mass or less, and more preferably 0.2% by mass or less.

Fe: 0.4% by Mass or Less

[0038] In the composition of the aluminum alloy for die casting of the present invention, when Fe is added, a fragile Al—Mn—Fe-based compound is formed and the toughness is decreased. Therefore, among the unavoidable impurities, the Fe content is preferably regulated to 0.4% by mass or less, and more preferably 0.3% by mass or less. In addition, since the addition of Fe decreases the corrosion resistance of the aluminum alloy for die casting, the addition amount is regulated to 0.4% by mass or less from this viewpoint as well.

Ti: 0.001 to 1.0% by Mass

[0039] Ti is preferably added as an optional additive element in an amount of 0.001 to 1.0% by mass. Ti improves the toughness of the aluminum alloy by refining the structure, and also has the effect of preventing casting cracks due to the refining. When being less than 0.001% by mass, the effect is small, and when containing in excess of 1.0% by mass, coarse crystals of Al—Ti-based compounds are formed, which adversely affects the toughness, and thus the addition amount is limited within the above range.

B: 0.0001 to 0.1% by Mass

[0040] B is preferably added as an optional additive element in an amount of 0.0001 to 0.1% by mass. B improves the toughness of the aluminum alloy by refining the structure, and also has the effect of preventing casting cracks due to the refining. When being less than 0.0001% by mass, the effect is small, and when containing in excess of 0.1% by mass, the effect is not improved, and thus the addition amount is limited within the above range.

Be: 0.001 to 0.1% by Mass

[0041] Be is effective for preventing the depletion of Mg and can be used as an optional additive element. In case of adding Be, the effect of preventing Mg depletion is not sufficient when being less than 0.001% by mass, and even if added in excess of 0.1% by mass, the effect of preventing Mg depletion has already been sufficiently obtained, and thus it becomes a factor of cost increase.

[0042] Examples of elements other than the above elements that can be additionally added include Cr, Zn, V, Ni, Zr, Sr, Cu, Mo, Sc, Y, Ca, and Ba. When these are contained in an amount of Cr: 0.5% by mass or less, Zn: 1.0% by mass or less, V: 0.5% by mass or less, Ni: 0.5% by mass or less, Zr: 0.5% by mass or less, Sr: 0.5% by mass or less, Cu: 0.5% by mass or less, Mo: 0.5% by mass or less, Sc: 0.5% by mass or less, Y: 0.5% by mass or less, Ca: 0.5% by mass, and Ba: 0.5% by mass or less, the influence on toughness or corrosion resistance is small, and therefore addition is permitted.

[0043] Cr, Zn, V, Cu, Mo, Sc and Y are expected to have the effect of improving the strength of the aluminum alloy by being mainly dissolved in the matrix of the aluminum alloy, Ni is expected to have the effect of improving castability such as the effect of preventing the molten metal from seizing into the mold, Zr and Sr are expected to have the effect of improving toughness and casting crack resistance caused by refining the structure, and Ca and Ba are expected to have the effect of preventing oxidative depletion of elements in the molten metal.

2. Method for Preparing Aluminum Alloy for Die Casting

[0044] In the following, the method for preparing the aluminum alloy for die casting of the present invention having the above composition will be described in detail.

(1) Melting of Molten Aluminum Alloy

[0045] In the preparation process of the aluminum alloy, the molten alloy of high temperature causes oxidative depletion of elements. The degree of oxidative progress differs depending on the contained element, and the more reactive the element, the faster the oxidative 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, a magnesium oxide is formed on the surface of the molten metal, and the Mg concentration in the molten metal decreases. It is possible to add extra Mg in anticipation of wear, but it is difficult to adjust the concentration due to the ever-decreasing Mg content, and it requires additional cost for adding extra Mg, which results in many unfavorable points in operation. It is known that this oxidative depletion of Mg is improved by adding Be of 10 ppm or more, and it is preferable to add from the view point of operation.

[0046] It is preferable that the element having the effect of preventing oxidative depletion is added to the molten metal before Mg is added when adjusting the components of the molten metal. This is because if Mg is added first, the Mg is depleted not a little in the time from the addition of Mg to the addition of the element having the effect of preventing oxidative depletion.

(2) Pre-Casting Treatment

[0047] Impurities such as hydrogen gas and oxides are mixed in the molten metal that is melted in the atmosphere, and when this molten metal is cast as it is, defects such as porosity are appeared during solidification, which results in inhibiting the toughness of the produced member. In order to prevent these defects, it is effective to perform bubbling with an inert gas such as nitrogen or argon gas after melting the molten metal and before die casting. The inert gas supplied from the lower part of the molten metal, when ascending, has the function of catching hydrogen gas and impurities in the molten metal and removing them to the surface of the molten metal.

3. Die Cast Aluminum Alloy Material

[0048] The die cast aluminum alloy material of the present invention is a die cast aluminum alloy material made of the aluminum alloy for die casting of the present invention having a tensile property of 0.2% proof stress of 140 MPa or more and elongation of 11% or more.

[0049] Both excellent 0.2% proof stress and elongation are basically realized by seriously optimizing the composition, and the desired tensile properties are obtained regardless of the shape and size of the die cast aluminum alloy material. Here, the 0.2% proof stress 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.

[0050] The die cast aluminum alloy material of the present invention preferably has the maximum particle size of the primary crystal Al—Mn-based compound in the longitudinal direction is 150 μm or less. When the maximum particle size of the primary crystal Al—Mn-based compound in the longitudinal direction is 150 μm or less, excellent ductility and corrosion resistance are realized. Here, the maximum particle size of the primary crystal Al—Mn-based compound in the longitudinal direction is preferably 100 μm or less, and more preferably 50 μm or less.

[0051] The method for determining the size of the primary crystal Al—Mn-based compound is not particularly limited, and the measurement may be performed by various conventionally known methods. For example, the size can be obtained by cutting the die cast aluminum alloy 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. At that time, 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. Depending on the observation method, the cross-sectional sample may be subjected to mechanical polishing, buffing, electrolytic polishing, etching or the like.

[0052] The shape and size of the die casting material are not particularly limited as long as the effects of the present invention are not impaired, and they can be used as various conventionally known members. Examples of the member include a vehicle body structural member such as a frame member.

4. Method for Manufacturing Die Cast Aluminum Alloy Material

[0053] The die cast aluminum alloy material of the present invention is a die casting material made of the aluminum alloy for die casting of the present invention, and has the above composition. In the following, the method for producing the aluminum alloy for die casting of the present invention will be described in detail.

[0054] Since the composition of the aluminum alloy for die casting of the present invention contains the element for the purpose of solid solution strengthening, it is necessary to pay attention to the cooling rate in the production of the die casting material. When the cooling rate at the time of casting is slow, Mg and Mn cannot be sufficiently solid-solved in the matrix, and therefore, it is preferable to secure a cooling rate of 50° C./sec or more at the time of casting. At this time, the casting pressure may be set from 50 MPa to 150 MPa.

[0055] Further, in the manufacturing of a member using the die casting method, since the molten metal is poured into the mold at high pressure and high speed, there is a case that air in the mold is involved in the molten metal, or a case that due to solidification shrinkage, defects such as bubbles, and nests are occur in the member. Since the presence of many such defects adversely affects the toughness of the member, it is preferable to take technical measures to reduce these defects during casting.

[0056] For example, a vacuum die casting method where air is prevented from being entrained in the molten metal by drawing air in the mold cavity before casting to create a vacuum state, a pore free die casting method (PF: Pore Free method, PF die casting method) where, after replacement the air in the mold cavity with active gas, for example, oxygen gas, and then the molten metal is poured, or the like is effective. According to the vacuum die casting method, the casting defects can be alleviated because the amount of air existing in the cavity is small in the first place, and according to the pore free die casting method, since the active gas, for example, oxygen, filled in the cavity reacts with the molten aluminum to form a fine oxide film (Al.sub.2O.sub.3) and is dispersed in the member, it is possible to suppress an adverse effect on the member characteristics.

[0057] There is a case where the alloy-based alloy, that is, the Al—Mg—Mn-based alloy to which the aluminum alloy for die casting of the present invention belongs, has a problem of inferior hot water flowability, because the alloy is different from the Al—Si-based alloy that is conventionally used widely as an alloy for die casting, and Si which is effective in improving castability is not actively added (or its content is regulated).

[0058] However, in the vacuum die casting method, since the inside of the mold cavity is negative pressure at the time of pouring, the mold filling property of the molten metal is promoted, and in the case of the pore free die casting method, since the active gas filled inside reacts with the molten aluminum alloy to create a negative pressure inside the cavity as in the vacuum die casting method to improve the mold filling property of the molten metal, and as a result, the same kind of effect as the improving the flowability of the alloy can be given. Therefore, in the Al—Mg—Mn-based alloy which is conventionally considered difficult to cast with good quality according to the die casting method, and in the prior literature, improvement was attempted by adding a high concentration of Mn or the like, it is possible to cast with good quality even at the Mn concentration of the composition of the aluminum alloy for die casting according to the present invention, and further, the effect of improving the elongation by lowering the Mn concentration can be exhibited.

[0059] Further, the aluminum alloy for die casting of the present invention is a non-heat treatable type aluminum alloy, and does not require heat treatment on the product after casting in order to obtain the mechanical properties required for the vehicle members in the die casting material. As a result, it is possible to reduce the cost related to the heat treatment step and the correction of the strain generated by the heat treatment step.

[0060] Although the typical 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 of these design changes are included in the technical scope of the present invention.

EXAMPLES

Example 1

[0061] A Lansley test piece was produced by preparing the melting material so as to have the components (prepared values) described as Example 1 in TABLE 1. Here, the melting temperature and the casting temperature were set to “liquidus line temperature+100° C.”, and the Lansley mold temperature was set to “150 f 50° C.”. The composition of the obtained Lansley test piece was measured by emission spectroscopic analysis, and the obtained results (measured values) are shown in TABLE 1 together. The values in TABLE 1 are % by mass.

TABLE-US-00001 TABLE 1 Cu Si Mg Zn Fe Mn Cr Ti P Be Al Ex. 1 Prepared Value — — 5.7 — — 1.0 — — — 0.0025 Bal. Measured Value 0.00 0.07 5.7 0.00 0.12 1.0 <0.0002 0.00 0.0022 0.0027 Bal. Ex. 2 Prepared Value — — 5.7 — — 1.3 — — — 0.0025 Bal. Measured Value 0.00 0.07 5.8 0.00 0.12 1.4 <0.0002 0.00 0.0029 0.0025 Bal. Com. Prepared Value — — 5.7 — — 1.95 — — — 0.0025 Bal. Ex. 1 Measured Value 0.00 0.07 5.8 0.00 0.12 1.95 <0.0002 0.00 0.0025 0.0030 Bal. Com. Prepared Value — — 5.7 — — 2.7 — — — 0.0025 Bal. Ex. 2 Measured Value 0.00 0.07 5.9 0.01 0.11 2.6 <0.0002 0.00 0.0054 0.0026 Bal.

[0062] When the cross section of the Lansley test piece was mirror-polished and the size of the primary crystal Al—Mn-based compound was measured by observation with an optical microscope, the maximum size was 33 μm. An optical micrograph is shown in FIG. 1.

[0063] The Lansley test piece was processed into the shape of a JIS standard CT71 type tensile test piece, and a tensile test was conducted in a room temperature environment. The obtained results are shown in TABLE 2. Tensile tests have been carried out a total of three times, and one test piece has a 0.2% proof stress of 136 MPa, but the other pieces have a 0.2% proof stress of 140 MPa or more, and an elongation of 11% or more (The average value of 0.2% proof stress is 140 MPa).

TABLE-US-00002 TABLE 2 Tensile strength 0.2% Proof Stress Elongation (MPa) (MPa) (%) Ex. 1 296 136 20 301 140 24 311 143 30 Ex. 2 304 147 18 322 152 23 302 147 29 Com. Ex. 1 322 173 13 268 165 7 277 169 — Com. Ex. 2 215 168 2 188 168 2 206 172 2

Example 2

[0064] A Lansley test piece was obtained in the same manner as in Example 1 except that the melting material was adjusted so as to have the components described as Example 2 in TABLE 1. The composition of the Lansley test piece was measured in the same manner as in Example 1, and the obtained results are shown in TABLE 1.

[0065] Further, when the size of the primary crystal Al—Mn-based compound was measured in the same manner as in Example 1, the maximum size was 37 μm. An optical micrograph is shown in FIG. 2.

[0066] Furthermore, the tensile test was performed in the same manner as in Example 1, and the obtained results are shown in TABLE 2. All test pieces have a 0.2% proof stress of 140 MPa or more and an elongation of 11% or more.

Example 3

[0067] After melting the aluminum alloy having the composition shown in TABLE 3, a die cast aluminum alloy material was obtained by die casting. The values in TABLE 3 are % by mass, which are the measurement results of the emission spectroscopic analysis.

TABLE-US-00003 TABLE 3 Cu Si Mg Zn Fe Mn Cr Ti P Be Al Ex. 3 <0.01 0.04 5.83 <0.01 0.06 1.5 — — — 0.0026 Bal.

[0068] As a die casting method, a pore free die casting method was employed to produce a die casting material. The size of the mold used at this time was 110 mm×110 mm×3 mm, the casting pressure at the time of die casting was 120 MPa, the molten metal temperature was 730° C., and the mold temperature was 170° C. A water-soluble release agent was used.

[0069] When the No. 14B test piece specified in JIS-Z2241 was sampled from the obtained die cast aluminum alloy material and subjected to the tensile test at room temperature, the 0.2% proof stress was 174 MPa and the elongation was 21%. From the results, it was confirmed that the die cast aluminum alloy material obtained from the aluminum alloy for die casting of the present invention has a high strength of 170 MPa or more and an elongation of more than 20%, and can be suitably used for, for example, vehicle members.

Example 4

[0070] After melting the aluminum alloy having the composition shown in TABLE 4, a die cast aluminum alloy material was obtained by the same die casting as in Example 3. The values in TABLE 4 are % by mass, which are the measurement results of the emission spectroscopic analysis.

TABLE-US-00004 TABLE 4 Cu Si Mg Zn Fe Mn Cr Ti P Be Al Ex. 4 <0.01 0.04 4.01 <0.01 0.06 1.6 — — — 0.003 Bal.

[0071] When the No. 14B test piece specified in JIS-Z2241 was sampled from the obtained die cast aluminum alloy material and subjected to the tensile test at room temperature, the 0.2% proof stress was 140 MPa and the elongation was 14%.

Example 5

[0072] After melting the aluminum alloy having the composition shown in TABLE 5, a die cast aluminum alloy material was obtained by the same die casting as in Example 3. The values in TABLE 5 are % by mass, which are the measurement results of the emission spectroscopic analysis.

TABLE-US-00005 TABLE 5 Cu Si Mg Zn Fe Mn Cr Ti P Be Al Ex. 5 <0.01 0.05 5.00 <0.01 0.06 1.5 — — — 0.003 Bal.

[0073] When the No. 14B test piece specified in JIS-Z2241 was sampled from the obtained die cast aluminum alloy material and subjected to the tensile test at room temperature, the 0.2% proof stress was 152 MPa and the elongation was 12%.

Example 6

[0074] After melting the aluminum alloy having the composition shown in TABLE 6, a die cast aluminum alloy material was obtained by the same die casting as in Example 3. The values in TABLE 6 are % by mass, which are the measurement results of the emission spectroscopic analysis.

TABLE-US-00006 TABLE 6 Cu Si Mg Zn Fe Mn Cr Ti P Be Al Ex. 6 <0.01 0.05 5.90 <0.01 0.05 1.05 — — — 0.004 Bal.

[0075] When the No. 14B test piece specified in JIS-Z2241 was sampled from the obtained die cast aluminum alloy material and subjected to the tensile test at room temperature, the 0.2% proof stress was 155 MPa and the elongation was 13%.

Comparative Example 1

[0076] A Lansley test piece was obtained in the same manner as in Example 1 except that the melting material was prepared so as to have the components described as Comparative Example 1 in TABLE 1. The composition of the Lansley test piece was measured in the same manner as in Example 1, and the obtained results are shown in TABLE 1.

[0077] Further, when the size of the primary crystal Al—Mn-based compound was measured in the same manner as in Example 1, the maximum size was 62 μm. An optical micrograph is shown in FIG. 3.

[0078] Furthermore, the tensile test was performed in the same manner as in Example 1, and the obtained 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%.

Comparative Example 2

[0079] A Lansley test piece was obtained in the same manner as in Example 1 except that the melting material was prepared so as to have the components described as Comparative Example 2 in TABLE 1. The composition of the Lansley test piece was measured in the same manner as in Example 1, and the obtained results are shown in TABLE 1.

[0080] Further, when the size of the primary crystal Al—Mn-based compound was measured in the same manner as in Example 1, the maximum size was 254 μm. An optical micrograph is shown in FIG. 4.

[0081] Furthermore, the tensile test was performed in the same manner as in Example 1, and the obtained 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 was remarkably reduced due to the coarsening of the primary crystal Al—Mn-based compound.

Comparative Example 3

[0082] After melting the aluminum alloy having the composition shown in TABLE 7, a die cast aluminum alloy material was obtained by the same die casting as in Example 3. The values in TABLE 7 are % by mass, which are the measurement results of the emission spectroscopic analysis.

TABLE-US-00007 TABLE 7 Cu Si Mg Zn Fe Mn Cr Ti P Be Al Com. Ex. 3 <0.01 0.04 3.05 <0.01 0.06 1.60 — — — 0.003 Bal.

[0083] When the No. 14B test piece specified in JIS-Z2241 was sampled from the obtained die cast aluminum alloy material and subjected to the tensile test at room temperature, the 0.2% proof stress was 126 MPa and the elongation was 19%.

Comparative Example 4

[0084] After melting the aluminum alloy having the composition shown in TABLE 8, a die cast aluminum alloy material was obtained by the same die casting as in Example 3. The values in TABLE 8 are % by mass, which are the measurement results of the emission spectroscopic analysis.

TABLE-US-00008 TABLE 8 Cu Si Mg Zn Fe Mn Cr Ti P Be Al Com. Ex. 4 <0.01 0.05 5.80 <0.01 0.05 0.54 — — — 0.004 Bal.

[0085] When the No. 14B test piece specified in JIS-Z2241 was sampled from the obtained die cast aluminum alloy material and subjected to the tensile test at room temperature, the 0.2% proof stress was 137 MPa and the elongation was 15%.

Comparative Example 5

[0086] After melting the aluminum alloy having the composition shown in TABLE 9, a die cast aluminum alloy material was obtained by the same die casting as in Example 3. The values in TABLE 9 are % by mass, which are the measurement results of the emission spectroscopic analysis.

TABLE-US-00009 TABLE 9 Cu Si Mg Zn Fe Mn Cr Ti P Be Al Com. Ex. 5 <0.01 0.05 5.70 <0.01 0.05 1.90 — — — 0.003 Bal.

[0087] When the No. 14B test piece specified in JIS-Z2241 was sampled from the obtained die cast aluminum alloy material and subjected to the tensile test at room temperature, the 0.2% proof stress was 137 MPa and the elongation was 15%.

[0088] From the above results, when the Mg content is 3.7 to 9.0% by mass and the Mn content is 0.8 to 1.7% by mass, the 0.2% proof stress of 140 MPa or more and the elongation of 11% or more can be obtained. Further, when the Mg content is 4.7 to 9.0% by mass and the Mn content is 0.9 to 1.7% by mass, the 0.2% proof stress of 150 MPa or more and the elongation of 12% or more can be obtained. Furthermore, when the Mg content is 5.2 to 6.5% by mass and the Mn content is 1.2 to 1.7% by mass, the 0.2% proof stress of 160 MPa or more and the elongation of 15% or more can be obtained.