JP7126915B2 - Aluminum alloy extruded material and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an aluminum alloy with excellent heat resistance and a method for producing the same.

In recent years, there has been an increasing demand for weight reduction and cost reduction of various structural members in automobiles, motorcycles, and other transportation equipment from the viewpoint of energy conservation and consideration for the global environment by reducing _CO2 emissions. A switch is under development. Among them, aluminum alloys used for internal combustion engine parts mounted in engines and the like are required to have high strength not only in room temperature environment but also in high temperature environment.

AA standard AA2618 and AA2219 alloys are applied to aluminum alloys for engine parts. Until now, in order to ensure high-temperature strength up to around 200 ° C., attempts have been made to increase the strength by adding Ag to aluminum alloys containing Cu, Mg and Ni as main components (Patent Document 1). . In order to increase the strength of the aluminum alloy, by setting the solution treatment temperature based on the melting start temperature of the aluminum alloy, the amount of supersaturated solid solution is increased, and the amount of fine precipitates during aging treatment is increased. Attempts have been made to increase the strength of aluminum alloys by (Patent Document 2).

JP 2008-115413 A Japanese Patent Application Laid-Open No. 2008-202121

However, the technique of adding Ag in Patent Literature 1 has a problem that the manufacturing cost increases because the base metal of Ag is expensive. Further, in Patent Document 2, since the solution treatment is performed near the melting start temperature of the aluminum alloy, the aluminum alloy is locally heated to the melting start temperature, the aluminum alloy is partially melted, and the structure of the aluminum alloy is deformed by high temperature heating. Partial recrystallization may lead to a decrease in strength.

Accordingly, an object of the present invention is to provide a high-strength aluminum alloy which is an Al--Cu--Mg-based aluminum alloy and which is excellent in heat resistance.

The present inventors have studied the relationship between the alloy components, working and treatment, and the internal structure, etc. As a result, the content of the alloy components, especially Cu and Mg, is set to a specific range, and the solution treatment is performed in two steps. By treating it, etc., it is possible to increase the strength of the aluminum alloy, suppress the coarsening of recrystallized grains, and form a fibrous structure with an average aspect ratio of 5 or more, thereby improving heat resistance. The inventors have found that a high-strength aluminum alloy can be obtained, and completed the present invention.

That is, the present invention (1) has Cu: 2.0 to 3.5 mass%, Si: 0.1 to 0.5 mass%, Fe: 0.5 to 1.0 mass%, Mn: 0.3 ~0.8 mass%, Mg: 1.5 to 2.5 mass%, Ti: 0.05 to 0.2 mass%, Ni: 0.5 to 2.0 mass%, and Zr: 0.05 to containing 0.3% by mass, the remainder consisting of inevitable impurities and aluminum,
A fiber structure in which the average aspect ratio of crystal grains in a cross section parallel to the plastic working direction is 5 or more, the tensile strength (A) at 25 ° C. is 480 MPa or more, and the tensile strength at 25 ° C. ( The difference (A - B) between A) and the tensile strength (B) measured at 25°C after being exposed for 10 hours at a temperature of 200°C is 50 MPa or less,
To provide an aluminum alloy extruded material characterized by

Moreover, the present invention (2) provides the aluminum alloy extruded material according to claim 1, further comprising Sc: 0.05 to 0.3% by mass.

In addition, the present invention ( 3 ) has Cu: 2.0 to 3.5% by mass, Si: 0.1 to 0.5% by mass, Fe: 0.5 to 1.0% by mass, Mn: 0.3 ~0.8 mass%, Mg: 1.5 to 2.5 mass%, Ti: 0.05 to 0.2 mass%, Ni: 0.5 to 2.0 mass%, and Zr: 0.05 to A homogenization treatment of holding an aluminum alloy ingot containing 0.3% by mass and the balance consisting of inevitable impurities and aluminum at a temperature of 400 to 520 ° C. for 1 to 20 hours;
A hot working step of hot working the homogenized material obtained by the homogenization treatment at a temperature of 300 to 500 ° C.;
A first-stage solution treatment in which the hot-worked material obtained by the hot-working step is held at a temperature range 10 to 20° C. lower than the melting start temperature of the hot-worked material for 0.5 to 5 hours; A second-stage solution treatment in which the second-stage solution treatment is held for 0.5 to 5 hours at a temperature range 5 to 10 ° C higher than the first-stage solution treatment temperature, and then water-cooled and quenched. and
An artificial aging treatment in which the two-step solution treated material obtained by the two-step solution treatment is held at a temperature of 150 to 220 ° C. for 2 to 30 hours,
A method for producing an aluminum alloy extruded material having
The aluminum alloy extruded material has a fiber structure in which the average aspect ratio of crystal grains in a cross section parallel to the direction of plastic working is 5 or more, the tensile strength (A) at 25 ° C. is 480 MPa or more, and 25 ° C. The difference (AB) between the tensile strength (A) at 200° C. and the tensile strength (B) measured at 25° C. after being exposed for 10 hours at a temperature of 200° C. is 50 MPa or less,
To provide a method for producing an aluminum alloy extruded material characterized by

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a high-strength aluminum alloy which is an Al--Cu--Mg-based aluminum alloy and has excellent heat resistance.

FIG. 10 is a diagram of an example of the morphology of a fibrous tissue; FIG. 3 is a diagram of an example of the morphology of a recrystallized structure;

The aluminum alloy of the present invention has Cu: 2.0 to 3.5 mass%, Si: 0.1 to 0.5 mass%, Fe: 0.5 to 1.0 mass%, Mn: 0.3 to 0. .8% by mass, Mg: 1.5-2.5% by mass, Ti: 0.05-0.3% by mass, Ni: 0.5-2.0% by mass, and Zr: 0.05-0. An aluminum alloy containing 3% by mass, the balance being inevitable impurities and aluminum, and having a fiber structure in which the average aspect ratio of crystal grains in a cross section parallel to the direction of plastic working is 5 or more.

The aluminum alloy of the present invention contains Cu, Si, Fe, Mn, Mg, Ti, Ni, and Zr as essential components, and the remainder consists of unavoidable impurities and aluminum. Moreover, the aluminum alloy of the present invention can further contain Sc in addition to these components, if necessary.

The Cu content of the aluminum alloy of the present invention is 2.0-3.5 mass %, preferably 2.5-3.3 mass %. Cu is an element that contributes to improvement of mechanical properties such as tensile strength and fatigue strength. When the Cu content of the aluminum alloy is within the above range, the tensile strength is increased. On the other hand, if the Cu content of the aluminum alloy is less than the above range, the effect of improving strength is reduced, and if it exceeds the above range, the melting point is significantly lowered, so the solution treatment temperature must be lowered. Therefore, the degree of supersaturation in the matrix after solution treatment becomes small, and the effect of strength improvement cannot be obtained.

The Si content of the aluminum alloy of the present invention is 0.1-0.5 mass %, preferably 0.2-0.4 mass %. Si precipitates fine dispersed phases of Al--Mn--Si compounds together with Mn, enhances the pinning effect of dislocations, and prevents coarsening of recrystallized grains during solution treatment. When the Si content of the aluminum alloy is within the above range, the high temperature strength is increased. On the other hand, if the Si content of the aluminum alloy is less than the above range, the strength improvement effect is reduced, and if it exceeds the above range, coarse compounds are formed, resulting in low high-temperature strength.

The Fe content of the aluminum alloy of the present invention is 0.5-1.0 mass %, preferably 0.6-0.9 mass %. Fe forms a compound with Ni to improve heat resistance. When the Fe content of the aluminum alloy is within the above range, the heat resistance is enhanced. On the other hand, if the Fe content of the aluminum alloy is less than the above range, the effect of improving the heat resistance becomes small, and if it exceeds the above range, Fe-based compounds such as Al-Fe and Al-Fe-Cu are generated. Since it is dispersed in the matrix, the effect of improving heat resistance is reduced.

The Mn content of the aluminum alloy of the present invention is 0.3-0.8 mass %, preferably 0.4-0.7 mass %. Mn improves mechanical properties, and precipitates and disperses fine Al-Mn-Si-based compounds together with Si, thereby suppressing recrystallization that occurs during solution treatment of the alloy and forming a fibrous structure. , improve strength. When the Mn content of the aluminum alloy is within the above range, strength and heat resistance are enhanced. On the other hand, if the Mn content of the aluminum alloy is less than the above range, the effect of improving strength and heat resistance is reduced, and if it exceeds the above range, large crystallized substances are likely to occur during casting, resulting in a decrease in strength. Invite.

The Mg content of the aluminum alloy of the present invention is 1.5-2.5% by mass, preferably 1.7-2.1% by mass. Mg improves mechanical properties. When the Mg content of the aluminum alloy is within the above range, the strength is increased. On the other hand, if the Mg content of the aluminum alloy is less than the above range, the effect of improving the strength will be small, and if it exceeds the above range, the formability will be poor and the productivity will be low.

The Ti content of the aluminum alloy of the present invention is 0.05-0.3 mass %, preferably 0.1-0.2 mass %. Ti forms a fine intermetallic compound, and a fine crystal grain structure can be stably obtained. When the Ti content of the aluminum alloy is within the above range, formation of coarse compounds in the ingot of the aluminum alloy is suppressed, so that high formability can be maintained. On the other hand, if the Ti content of the aluminum alloy is less than the above range, the above effect will be reduced, and if it exceeds the above range, formability will be poor. Also, Ti may be added alone, or may be added in combination with B in a composite manner. A greater effect can be obtained by containing B together for crystal grain refinement.

The Ni content of the aluminum alloy of the present invention is 0.5-2.0 mass %, preferably 0.8-1.3 mass %. Ni forms a compound with Fe to improve heat resistance. When the Ni content of the aluminum alloy is within the above range, the heat resistance is enhanced. On the other hand, if the Ni content of the aluminum alloy is less than the above range, the effect of improving the heat resistance becomes small, and if it exceeds the above range, Ni-based compounds such as Al-Ni-based and Al-Ni-Cu-based compounds are generated. Dispersion in the matrix results in low high temperature strength.

The Zr content of the aluminum alloy of the present invention is 0.05-0.3 mass %, preferably 0.1-0.2 mass %. Zr suppresses the coarsening of recrystallized grains that occur during the solution treatment by finely dispersing the Al ₃ Zr compound, forms a fibrous structure, and increases the strength. When the Zr content of the aluminum alloy is within the above range, the strength is increased. On the other hand, if the Zr content of the aluminum alloy is less than the above range, the strength improvement effect will be small, and if it exceeds the above range, large crystallized substances will occur during casting, resulting in poor moldability.

When the aluminum alloy of the present invention contains Sc, the Sc content of the aluminum alloy of the present invention is 0.05-0.3% by mass, preferably 0.1-0.2% by mass. Sc suppresses the coarsening of recrystallized grains that occur during the solution treatment by finely dispersing the Al ₃ Sc compound, and contributes to precipitation hardening at around 300° C., resulting in high heat resistance. When the Sc content of the aluminum alloy is within the above range, the heat resistance is enhanced. On the other hand, if the Sc content of the aluminum alloy is less than the above range, the effect of improving the heat resistance becomes small, and if it exceeds the above range, coarse compounds are formed without fine precipitation, resulting in a decrease in strength.

The aluminum alloy of the present invention has a fiber structure in which the average aspect ratio of crystal grains in a cross section parallel to the direction of plastic working is 5 or more. Since the aluminum alloy has a fiber structure (for example, the structure shown in FIG. 1) in which the average aspect ratio of crystal grains in a cross section parallel to the direction of plastic working is 5 or more, heat resistance is enhanced. On the other hand, if a recrystallized structure (for example, the structure shown in FIG. 2) is formed in the plastic working direction of the aluminum alloy and the average aspect ratio of the crystal grains in the parallel cross section is less than 5, the heat resistance will be low. In the present invention, the average aspect ratio of crystal grains in a cross section parallel to the direction of plastic working is obtained by the following measuring method. A cross section parallel to the direction of plastic working of each test material is electrolytically etched to expose crystal grains, and the material structure is photographed with a polarizing optical microscope at a magnification of 25 times. Next, arbitrarily select 10 crystal grains from the crystal grains observed on the photograph, and for each crystal grain, "(length in the direction of plastic working) / (length in the direction perpendicular to the direction of plastic working)" The aspect ratio is calculated by the formula, and the average of 10 selected crystal grains is obtained to obtain the average aspect ratio. If the aspect ratio is sufficiently large, the length of all crystal grains in the direction of plastic working exceeds the field of view, and the aspect ratio can be determined to be 5 or more, the average aspect ratio is set to 5 or more.

The aluminum alloy of the present invention has a tensile strength (A) at 25 ° C. of 480 MPa or more, and has a tensile strength (A) at 25 ° C. and a temperature of 200 ° C. After 10 hours of exposure and holding, The difference (AB) from the tensile strength (B) when measured at °C is 50 MPa or less. 2. Description of the Related Art Parts for an internal combustion engine mounted on an engine or the like may lose strength when used for a long time in a high temperature environment. The aluminum alloy of the present invention has a tensile strength (A) at 25 ° C. of 480 MPa or more, and the tensile strength (A) at 25 ° C. and after exposure and holding at a temperature of 200 ° C. for 10 hours , The difference (AB) from the tensile strength (B) when measured at 25 ° C. is 50 MPa or less, so that the strength is high and the strength reduction of the parts in a high temperature environment is minimized. can be reduced and the product life can be extended. The tensile strength (B) is measured by heating the test object to 200°C at a heating rate of 100°C/hour, then holding it at 200°C for 10 hours, and then air-cooling it to about room temperature. It is the tensile strength when the test object is measured at 25°C after it has been heated. Moreover, the tensile strength (A) is the tensile strength when the test object is measured at 25° C. before the test object is subjected to the heat treatment described above.

The aluminum alloy of the present invention may contain elements other than those mentioned above as unavoidable impurity elements. The content of the inevitable impurity elements in the aluminum alloy of the present invention is not particularly limited as long as the effects of the present invention are not impaired, and the content of each inevitable impurity element is 0.05% by mass or less. is preferred.

The aluminum alloy of the present invention is manufactured, for example, by the method of manufacturing the aluminum alloy of the present invention described below.

The method for producing the aluminum alloy of the present invention comprises: Cu: 2.0 to 3.5% by mass; Si: 0.1 to 0.5% by mass; Fe: 0.5 to 1.0% by mass; 3 to 0.8% by mass, Mg: 1.5 to 2.5% by mass, Ti: 0.05 to 0.3% by mass, Ni: 0.5 to 2.0% by mass, and Zr: 0.05 A homogenization treatment of holding an aluminum alloy ingot containing ~0.3% by mass and the balance consisting of inevitable impurities and aluminum at a temperature of 400 to 520 ° C. for 1 to 20 hours;
A hot working step of hot working the homogenized material obtained by the homogenization treatment at a temperature of 300 to 500 ° C.;
A first-stage solution treatment in which the hot-worked material obtained by the hot-working step is held at a temperature range 10 to 20° C. lower than the melting start temperature of the hot-worked material for 0.5 to 5 hours; A second-stage solution treatment in which the second-stage solution treatment is held for 0.5 to 5 hours at a temperature range 5 to 10 ° C higher than the first-stage solution treatment temperature, and then water-cooled and quenched. and
An artificial aging treatment in which the two-step solution treated material obtained by the two-step solution treatment is held at a temperature of 150 to 220 ° C. for 2 to 30 hours,
A method for producing an aluminum alloy characterized by having

In the method for producing an aluminum alloy according to the present invention, first, an aluminum alloy having a predetermined composition is melted, and a billet made of the aluminum alloy having a predetermined composition is cast by DC casting. The Cu content in the billet is 2.0 to 3.5 mass%, preferably 2.5 to 3.3 mass%, and the Si content is 0.1 to 0.5 mass%, preferably 0. .2 to 0.4 mass %, the Fe content is 0.5 to 1.0 mass %, preferably 0.6 to 0.9 mass %, the Mn content is 0.3 to 0 .8 wt%, preferably 0.4 to 0.7 wt%, Mg content is 1.5 to 2.5 wt%, preferably 1.7 to 2.1 wt%, Ti content The amount is 0.05-0.3% by weight, preferably 0.1-0.2% by weight, and the Ni content is 0.5-2.0% by weight, preferably 0.8-1.0% by weight. 3% by mass, the Zr content is 0.05 to 0.3% by mass, preferably 0.1 to 0.2% by mass, and if necessary, when Sc is contained, the Sc content is , 0.05 to 0.3% by weight, preferably 0.1 to 0.2% by weight.

In the homogenization treatment according to the aluminum alloy production method of the present invention, a billet obtained by casting is homogenized by holding at a temperature of 400 to 520° C. for 1 to 20 hours to obtain a homogenized material. When the homogenization temperature is less than 400°C, sufficient homogenization is not performed, and when it exceeds 520°C, unevenly distributed micro-segregation causes eutectic melting, resulting in low fatigue strength. If the homogenization time is less than 1 hour, sufficient homogenization will not be achieved, and if it exceeds 20 hours, the heat treatment furnace will be occupied for too long for the homogenization treatment, increasing the production cost.

In the hot working step according to the method for producing an aluminum alloy of the present invention, the homogenized material is hot worked at a temperature of 300 to 500° C. to obtain a hot worked material. Extrusion and forging are preferable as the hot working. In the hot working step, hot working is performed one or more times. If hot working is not performed, microscopic segregation is present in the as-cast structure, resulting in low fatigue strength. If the hot working temperature is less than 300°C, processing strain is accumulated inside the material, which causes coarsening of crystal grains during solution treatment, resulting in a decrease in strength. Heat generated during working deformation is added, and eutectic melting occurs partially, resulting in a decrease in fatigue strength.

In the two-stage solution treatment according to the method for producing an aluminum alloy of the present invention, the hot-worked material is held in a temperature range 10 to 20 ° C. lower than the melting start temperature of the hot-worked material for 0.5 to 5 hours. After the first solution treatment and the second solution treatment in which the temperature is maintained for 0.5 to 5 hours at a temperature range 5 to 10 ° C higher than the first solution treatment temperature, water cooling is performed. and quenching to obtain a two-stage solution heat-treated material.

In the first-stage solution treatment, by heating in a temperature range 10 to 20 ° C lower than the melting start temperature of the hot-worked material, the micro-segregation is thermally eliminated from the surface to the inside of the hot-worked material and homogenized. By eliminating the melting start temperature difference between the surface layer and the inside, it becomes possible to perform the second-stage solution treatment at a higher temperature than the first-stage solution treatment. The higher the temperature of the solution treatment, the greater the amount of supersaturated solid solution in the alloy matrix, the greater the amount of fine precipitates produced by artificial aging, and the higher the strength. If the difference between the melting start temperature of the hot-worked material and the first-stage solution treatment temperature is less than 10°C, eutectic melting occurs in the presence of microsegregation, the toughness decreases, and the surface If the difference between the melting start temperature of the hot-worked material and the first-stage solution treatment temperature exceeds 20 ° C., homogenization is not sufficient, and the second-stage solution treatment Eutectic melting may occur in the heat treatment. Also, if the first-stage solution treatment time is less than 0.5 hours, homogenization is not sufficient, and eutectic melting may occur in the second-stage solution treatment. If the solution treatment time exceeds 5 hours, the occupancy time of the heat treatment furnace becomes too long, increasing the production cost. In the first-stage solution treatment, heating in a temperature range 10 to 20 ° C. lower than the melting start temperature of the hot-worked material means, for example, that the hot-worked material after hot working has a melting start temperature of 500 ° C. If so, it means that the first stage of solution heat treatment involves heating in the temperature range of 480 to 490°C.

In the second-stage solution treatment, heating is performed at a temperature range 5 to 10°C higher than the first-stage solution treatment temperature. As the amount increases, the amount of fine precipitates produced by artificial aging increases, and the strength increases. If the difference between the second-stage solution treatment temperature and the first-stage melting start temperature exceeds 10°C, the formation of a partial recrystallized structure and eutectic melting will occur, and the strength and Charpy impact value will decrease. If the difference between the second-stage solution treatment temperature and the first-stage solution treatment temperature is less than 5°C, a supersaturated solid solution of Cu and Mg in the alloy matrix will occur. Since the amount is less, the strength is not increased. In addition, if the second-stage solution treatment time is less than 0.5 hours, the amount of supersaturated solid solution of Cu and Mg in the alloy matrix decreases, so the strength does not increase. If the hardening treatment time exceeds 5 hours, the occupancy time of the heat treatment furnace becomes too long, increasing the manufacturing cost. In the second-stage solution treatment, heating in a temperature range 5 to 10 ° C higher than the first-stage solution treatment temperature means, for example, if heating is performed at 485 ° C. in the first-stage solution treatment, two The step of solution heat treatment means heating in a temperature range of 490 to 495°C.

In the artificial aging treatment according to the method for producing an aluminum alloy of the present invention, the two-stage solution-treated material is held at a temperature of 150 to 220° C. for 2 to 30 hours. When the artificial aging treatment temperature is less than 150°C, the amount of precipitates is small, resulting in low strength. On the other hand, if the artificial aging treatment temperature is less than 2 hours, the amount of precipitation is small and the strength is low.

The aluminum alloy obtained by carrying out the method for producing an aluminum alloy of the present invention has a fiber structure in which the average aspect ratio of crystal grains in a cross section parallel to the direction of plastic working is 5 or more. Therefore, the aluminum alloy obtained by performing the method for producing an aluminum alloy of the present invention has a tensile strength (A) at 25 ° C. of 480 MPa or more, and a tensile strength (A) at 25 ° C. The difference (AB) from the tensile strength (B) measured at 25°C after being exposed to a temperature of 200°C for 10 hours is 50 MPa or less. That is, the aluminum alloy obtained by carrying out the method for producing an aluminum alloy of the present invention has high strength and high heat resistance.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples shown below.

(Example 1 and Comparative Example 1)
Aluminum alloy billets (diameter 90 mm) having compositions shown in Table 1 (Example) and Table 2 (Comparative Example) obtained by DC casting were homogenized at 470°C for 20 hours. In addition, in Table 1 and Table 2, the content is mass %, and the balance is aluminum. Then, it was hot extruded at 400° C. to obtain a hot extruded material in the form of a round bar with a diameter of 15 mm. Next, the hot extruded material is held at a temperature of 520 ° C. for 2 hours as a first-stage solution treatment, and then held at a temperature of 527 ° C. for 2 hours as a second-stage solution treatment. Quenching by cooling was performed. Then, artificial aging treatment was performed at 190° C. for 20 hours to obtain an aluminum alloy with a T6 temper.
Then, the obtained aluminum alloy was evaluated. Table 3 shows the results.

<Measurement of eutectic melting start temperature>
The hot extruded material was measured with a differential scanning calorimeter to determine the eutectic melting start temperature.

<Measurement of tensile strength>
The tensile strength was measured according to JIS Z 2241.
The test samples were an aluminum alloy obtained by artificial aging treatment (test sample 1) and an aluminum alloy obtained by artificial aging treatment, which were heated to 200 ° C. at a heating rate of 100 ° C./hour, and then , and held at 200° C. for 10 hours, followed by air cooling to obtain an aluminum alloy (test sample 2) cooled to about room temperature.

<Measurement of average aspect ratio of crystal grains>
A cross section parallel to the direction of plastic working of the aluminum alloy was exposed to crystal grains by electrolytic etching, and the material structure was photographed with a polarizing optical microscope at a magnification of 25 times. Select 10 arbitrarily from the crystal grains observed on the photograph, and for each crystal grain, by the formula "(length in the direction of plastic working) / (length in the direction perpendicular to the direction of plastic working)" , to calculate the aspect ratio. The aspect ratios of 10 arbitrarily selected crystal grains were averaged to obtain an average aspect ratio. When the aspect ratio is sufficiently large, the length of all crystal grains in the direction of plastic working exceeds the field of view, and the aspect ratio can be determined to be 5 or more, the average aspect ratio is set to 5 or more.

Comparative example no. Nos. 21 to 37 were out of the scope of the present invention, and either the materials were not well formed, or good tensile strength was not obtained.
Comparative example no. In No. 21, the strength was low because the Cu content was less than 2.0% by mass.
Comparative example no. In No. 22, since the Cu content exceeded 3.5% by mass, the eutectic melting initiation temperature was low, recrystallization occurred, and the tensile strength of the material was low.
Comparative example no. In No. 23, since the Si content was less than 0.1% by mass, a recrystallized structure was formed, and the tensile strength and the average aspect ratio of crystal grains were low.
Comparative example no. In No. 24, since the Si content exceeded 0.5% by mass, a coarse compound was formed and the strength was lowered after being exposed to 200° C. for 10 hours.
Comparative example no. In No. 25, the strength was low because the Fe content was less than 0.1% by mass.
Comparative example no. In No. 26, since the Fe content exceeded 1.0% by mass, a coarse compound was formed, and the strength after exposure and holding at 200° C. for 10 hours decreased.
Comparative example no. In No. 27, since the Mn content was less than 0.3% by mass, a recrystallized structure was formed, and the tensile strength and the average aspect ratio of crystal grains were low.
Comparative example no. In No. 28, since the Mn content exceeded 0.8% by mass, a coarse compound was formed, and the strength after exposure to 200° C. for 10 hours decreased.
Comparative example no. No. 29 had a low strength because the Mg content was less than 1.5% by mass.
Comparative example no. In No. 30, since the Mg content exceeded 2.5% by mass, moldability was poor and cracks occurred during extrusion.
Comparative example no. In No. 31, since the Ti content was less than 0.05% by mass, a recrystallized structure was formed, and the tensile strength and the average aspect ratio of crystal grains were low.
Comparative example no. In No. 32, since the Ti content was 0.27% by mass , coarse compounds were generated in the ingot, and cracks were generated during extrusion.
Comparative example no. No. 33 had a low high-temperature strength because the Ni content was less than 0.5% by mass.
Comparative example no. In No. 34, since the Ni content exceeded 2.0% by mass, the Ni-based intermetallic compound was dispersed in the matrix and the high-temperature strength was low.
Comparative example no. In No. 35, since the Zr content was less than 0.05% by mass, a recrystallized structure was formed, and the tensile strength and the average aspect ratio of crystal grains were low.
Comparative example no. In No. 36, since the Zr content exceeded 0.3% by mass, coarse compounds were generated in the ingot, and cracks occurred during extrusion.
Comparative example no. In No. 37, since the Sc content exceeded 0.3% by mass, coarse compounds were formed without fine precipitation, resulting in low strength.
On the other hand, Example No. 1 to 20 are within the scope of the present invention, so the fiber structure has an average aspect ratio of 5 or more of the crystal grains in the cross section parallel to the plastic working direction, and the tensile strength measured at 25 ° C. is 480 MPa or more. And, the difference between the tensile strength (A) at 25 ° C., the tensile strength measured at 25 ° C., and the tensile strength measured at 25 ° C. after exposure and holding at a temperature of 200 ° C. for 10 hours is 50 MPa or less. Met.

(Example 2 and Comparative Example 2)
An aluminum alloy billet (90 mm in diameter) having the composition shown in Table 4 obtained by DC casting was homogenized at 470° C. for 20 hours. In addition, in Table 4, the content is mass %, and the balance is aluminum. Then, it was hot extruded at 400° C. to obtain a hot extruded material in the form of a round bar with a diameter of 15 mm. Next, the hot extruded materials were subjected to the first-stage solution treatment under the conditions shown in Table 5 or Table 6, followed by the second-stage solution treatment, and then quenched by water cooling. Then, artificial aging treatment was performed at 190° C. for 20 hours to obtain an aluminum alloy with a T6 temper.
Then, the obtained aluminum alloy was evaluated. Table 7 shows the results.

Comparative example no. Nos. 42 to 45 are outside the scope of the present invention, so the material was not well molded or did not have good tensile strength.
Comparative example no. 42 and comparative example no. 44, the difference between the eutectic melting start temperature of the hot-worked material and the first-stage solution treatment temperature exceeds 20 ° C., and the second-stage solution treatment temperature and the first-stage solution treatment temperature is less than 5°C, the amount of supersaturated solid solution due to solution treatment is small, and precipitation strengthening due to artificial aging treatment is insufficient, so that the effect of improving the strength of the material cannot be obtained.
Comparative example no. 43 and Comparative Example No. In 45, the difference between the eutectic melting start temperature of the hot-worked material and the first-stage solution treatment temperature is less than 10 ° C., and the second-stage solution treatment temperature and the first-stage solution treatment temperature are less than 10 ° C. Since the difference between the two exceeds 10°C, the material recrystallizes and the aspect ratio decreases, resulting in a decrease in the strength at 25°C and after exposure and holding at a temperature of 200°C for 10 hours.
On the other hand, Example No. 38 to 41 are within the scope of the present invention, so the fiber structure has an average aspect ratio of 5 or more of the crystal grains in the cross section parallel to the plastic working direction, and the tensile strength measured at 25 ° C. is 480 MPa or more. And, the difference between the tensile strength (A) at 25 ° C., the tensile strength measured at 25 ° C., and the tensile strength measured at 25 ° C. after exposure and holding at a temperature of 200 ° C. for 10 hours is 50 MPa or less. Met.

Claims (3)

Cu: 2.0 to 3.5% by mass, Si: 0.1 to 0.5% by mass, Fe: 0.5 to 1.0% by mass, Mn: 0.3 to 0.8% by mass, Mg: 1.5 to 2.5% by mass, Ti: 0.05 to 0.2 % by mass, Ni: 0.5 to 2.0% by mass, and Zr: 0.05 to 0.3% by mass, The balance consists of inevitable impurities and aluminum,
A fiber structure in which the average aspect ratio of crystal grains in a cross section parallel to the plastic working direction is 5 or more, the tensile strength (A) at 25 ° C. is 480 MPa or more, and the tensile strength at 25 ° C. ( The difference (A - B) between A) and the tensile strength (B) measured at 25°C after being exposed for 10 hours at a temperature of 200°C is 50 MPa or less,
An aluminum alloy extrusion characterized by: The aluminum alloy extruded material according to claim 1, further comprising Sc: 0.05 to 0.3% by mass. Cu: 2.0 to 3.5% by mass, Si: 0.1 to 0.5% by mass, Fe: 0.5 to 1.0% by mass, Mn: 0.3 to 0.8% by mass, Mg: 1.5 to 2.5% by mass, Ti: 0.05 to 0.2 % by mass, Ni: 0.5 to 2.0% by mass, and Zr: 0.05 to 0.3% by mass, A homogenization treatment in which an aluminum alloy ingot whose balance is inevitable impurities and aluminum is held at a temperature of 400 to 520 ° C. for 1 to 20 hours;
A hot working step of hot working the homogenized material obtained by the homogenization treatment at a temperature of 300 to 500 ° C.;
A first-stage solution treatment in which the hot-worked material obtained by the hot-working step is held at a temperature range 10 to 20° C. lower than the melting start temperature of the hot-worked material for 0.5 to 5 hours; A second-stage solution treatment in which the second-stage solution treatment is held for 0.5 to 5 hours at a temperature range 5 to 10 ° C higher than the first-stage solution treatment temperature, and then water-cooled and quenched. and
An artificial aging treatment in which the two-step solution treated material obtained by the two-step solution treatment is held at a temperature of 150 to 220 ° C. for 2 to 30 hours,
A method for producing an aluminum alloy extruded material having
The aluminum alloy extruded material has a fiber structure in which the average aspect ratio of crystal grains in a cross section parallel to the direction of plastic working is 5 or more, the tensile strength (A) at 25 ° C. is 480 MPa or more, and 25 ° C. The difference (AB) between the tensile strength (A) at 200° C. and the tensile strength (B) measured at 25° C. after being exposed for 10 hours at a temperature of 200° C. is 50 MPa or less,
A method for producing an aluminum alloy extruded material , characterized by:

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