JP6774787B2 - Magnesium alloy manufacturing method - Google Patents

Description

The present invention relates to a method for producing a magnesium alloy.

Magnesium has the lowest density (= 1.7 g / cm ³ ) among practical structural metal materials, has easy recyclability peculiar to metal materials, and has abundant resources, so it is lightweight for next-generation structural use. It is attracting attention as a material.

For example, in the automobile industry, members such as a steering wheel, a cylinder head cover, and an oil pan as exemplified in Patent Document 1 below are made of a magnesium alloy casting material. Further, for example, in home appliances, the housing of home appliances such as personal computers and mobile phones is made of magnesium alloy casting material.

Japanese Unexamined Patent Publication No. 2008-24113

The production method by the casting method of magnesium alloy castings has problems such as the need for post-treatment to compensate for casting defects, low yield, and problems in the strength and rigidity of members. In order to solve these problems, it is useful to study the additive alloy elements added to the magnesium alloy. In addition, the plastic working process generally has a high yield and can be said to be an effective means for expanding the demand for magnesium alloys because it can achieve high strength and high toughness at the same time as molding.

However, when the strength of the magnesium alloy is improved, for example, when rolling is performed as a plastic working process, crystallized substances and intermetallic compounds are arranged parallel to the rolling direction, and work hardening occurs or aggregates in the magnesium phase. There is a problem that a structure is formed and the anisotropy of mechanical properties is increased.

The present invention has been made in view of the existence of the above-mentioned problems, and an object of the present invention is to obtain a high-performance magnesium alloy material having high strength and high ductility and no anisotropy in mechanical properties. The purpose is to provide a method for producing a magnesium alloy.

The method for producing a magnesium alloy according to the present invention is 15 to 120 ° C. lower than the solidus temperature of the magnesium alloy after the first rolling process of rolling the magnesium alloy with a rolling reduction of 40% or more. It is a method for producing a magnesium alloy, in which a heat treatment process of performing heat treatment at a temperature of 10 minutes to 10 hours is performed, and then a second rolling process of rolling the magnesium alloy subjected to the heat treatment process is performed again. The magnesium alloy subjected to the second rolling process has a tensile strength of 300 MPa or more in the rolling direction of the second rolling process and a strain at break of 0.1 or more, and further, the first (Ii) For the magnesium alloy subjected to the rolling process, the tensile strength in the 45 ° direction or 90 ° direction with respect to the rolling direction of the second rolling process is the value of the tensile strength in the rolling direction of the second rolling process. It is ± 6%, and the strain in the 45 ° direction or 90 ° direction with respect to the rolling direction of the second rolling process is within ± 17% of the strain value at the time of breaking in the rolling direction of the second rolling process. it is characterized in that.

A method of manufacturing a magnesium alloy according to the present invention, the magnesium alloy the second rolling step has been performed, the average crystal grain size of the magnesium phase does not exceed 25μm or less, crystallized substances or metals intermetallic compounds The area ratio of the magnesium phase to the magnesium phase is 7% or less, the equivalent circle diameter of the crystallized product or the intermetallic compound is 0.1 to 9 μm, and the average value thereof can be 7 μm or less.

Further, in the method for producing a magnesium alloy according to the present invention, the crystallized product or the intermetallic compound formed at the grain boundary of the magnesium phase is finely dispersed, and the crystal is finely dispersed. The distance between the product or the intermetallic compound can be 0.14 μm or more.

According to the present invention, it is possible to provide a method for producing a magnesium alloy, which can obtain a high-performance magnesium alloy material having high strength and high ductility and no anisotropy in mechanical properties.

It is a flowchart which shows the example of the manufacturing method of the magnesium alloy which concerns on this embodiment. It is a schematic diagram for demonstrating the state of the crystallized material or the metal-to-metal compound which concerns on this embodiment, and FIG. 2A in FIG. 2 is a crystallized product of a magnesium alloy which has undergone the first rolling process or It is a figure which shows the state of the metal-to-metal compound, and the fraction (b) in FIG. 2 is a figure which shows the state which performed the heat treatment process on the magnesium alloy shown by the fraction (a) in FIG. FIG. 2C is a diagram showing a state in which the magnesium alloy shown in FIG. 2B in FIG. 2 is subjected to a second rolling process. It is a micro observation photograph which shows the metal structure of the magnesium alloy which performed the 1st rolling process which concerns on this embodiment, and the segment (a) in FIG. 3 is AMX1001 which performed the 1st rolling process. , FIG. 3B in FIG. 3 is an AZX811 subjected to the first rolling process. It is a micro-observation photograph which shows the metal structure of the magnesium alloy which performed the heat treatment process which concerns on this Embodiment, and the magnesium alloy which performed the heat treatment process which concerns on a comparative example, and the segment (a) in FIG. 4 is 450. It is a micro observation photograph which shows the metal structure of AMX1001 which performed the heat treatment processing process which concerns on this embodiment which performs the heat treatment processing at ℃ for 5 hours, and the fraction (b) in FIG. 4 is the heat treatment processing at 490 ° C. for 1 hour. It is a micro observation photograph which shows the metal structure of AMX1001 which performed the heat treatment process which concerns on the comparative example which performs. It is a micro observation photograph which shows the metal structure of the magnesium alloy which performed the heat treatment processing process which concerns on this Embodiment, and the fraction (a) in FIG. 5 is performed the heat treatment processing process which performs the heat treatment processing at 400 degreeC for 10 minutes. It is a micro observation photograph showing the metal structure of AZX811 that has been obtained, and the fraction (b) in FIG. 5 is a micro observation photograph showing the metal structure of AZX811 that has been subjected to a heat treatment processing step of performing a heat treatment process at 500 ° C. for 1 hour. FIG. 5C in FIG. 5 is a micro-observation photograph showing the metallographic structure of AZX612 subjected to the heat treatment processing step of performing the heat treatment processing at 450 ° C. for 10 hours. It is a figure which shows the Vickers hardness of the magnesium alloy which performed the heat treatment process which concerns on this embodiment, and the fraction (a) in FIG. 6 is the thing which used AZ61 as a magnesium alloy, and is shown in FIG. The fraction (b) is the one using AZX811 as the magnesium alloy, the fraction (c) in FIG. 6 is the one using AZ612 as the magnesium alloy, and the fraction (d) in FIG. 6 is , AMX1001 is used as the magnesium alloy. It is a micro observation photograph which shows the metal structure of AZX811 which performed the second rolling process after the heat treatment process which concerns on this embodiment. The figure which shows the SEM observation photograph of the magnesium alloy material which performed the 2nd rolling process on the magnesium alloy which performed the heat treatment process which concerns on this embodiment, and the magnesium alloy which performed the heat treatment process which concerns on a comparative example. FIG. 8A shows the AMX1001 subjected to the heat treatment process according to the present embodiment to which the second rolling process is performed, and the component diagram (b) in FIG. 8 shows the component diagram (b) in FIG. AMX1001 subjected to the heat treatment process according to the comparative example was subjected to the second rolling process, and the fractional diagram (c) in FIG. 8 was subjected to the heat treatment process according to the present embodiment. The AZX612 is subjected to the second rolling process, and the fraction (d) in FIG. 8 is the AZX612 subjected to the heat treatment process according to the comparative example, which is subjected to the second rolling process. .. It is a figure which shows the SEM observation photograph of the magnesium alloy material which performed the 2nd rolling process on the magnesium alloy which performed the heat treatment process which concerns on this embodiment, and FIG. 9 (a) in FIG. The AZX811 subjected to the heat treatment processing step according to the present embodiment is subjected to the second rolling processing step, and the fraction (b) in FIG. 9 shows the heat treatment processing step according to the present embodiment. The AZX811 is subjected to the second rolling process, and the fraction (c) in FIG. 9 shows the AZX612 subjected to the heat treatment process according to the present embodiment to be subjected to the second rolling process. Is. It is a figure which shows the FE-SEM observation photograph which shows the interval of a crystallized substance or an intermetallic compound.

Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. It should be noted that the following embodiments do not limit the invention according to each claim, and not all combinations of features described in the embodiments are essential for the means for solving the invention. ..

As a result of diligent research to solve the above-mentioned problems, the inventors performed rolling processing on the magnesium alloy under predetermined conditions, heat treatment processing under predetermined conditions, and again under predetermined conditions. It was found that a magnesium alloy material with high strength and high ductility and no anisotropy in mechanical properties can be obtained by rolling in. Therefore, in the embodiments described below, the method for producing a magnesium alloy found by the inventors and the analysis results and test results showing the characteristics of the magnesium alloy material produced by such a production method will be described. Here, FIG. 1 is a flowchart showing an example of a method for producing a magnesium alloy according to the present embodiment. Further, FIG. 2 is a schematic view for explaining the state of the crystallized product or the intermetallic compound according to the present embodiment, and FIG. 2A in FIG. 2 is magnesium subjected to the first rolling process. It is a figure which shows the state of the crystallized product of the alloy, or the intermetallic compound, and the fractional figure (b) in FIG. 2 is the state which performed the heat treatment process on the magnesium alloy shown by the fractional figure (a) in FIG. FIG. 2C is a diagram showing a state in which the magnesium alloy shown in FIG. 2B is subjected to a second rolling process.

The method for producing a magnesium alloy according to the present embodiment includes 6.0 to 10 mass% of Al, 0 to 1.5 mass% of Zn, 0 to 3.2 mass% of Ca, and 0.01 to 0.3 mass% of Mn. A magnesium alloy containing magnesium and having a component composition in which the balance is composed of magnesium and unavoidable impurities can be used.

Aluminum (Al) is added in the range of 6.0 to 10% in order to precipitate a precipitate (Al ₂ Ca) or a crystallized product (Mg ₁₇ Al ₁₂ ) with calcium inside the magnesium alloy. Is preferable. If the amount of aluminum added exceeds 10%, excessive precipitates are precipitated and the workability is lowered. Further, if the amount of aluminum added is less than 6.0%, it is difficult to obtain the desired strength.

Zinc (Zn) may be added in the range of 0 to 1.5%. Zinc contributes to the improvement of mechanical properties such as castability and strength, but when the amount of zinc added exceeds 1.5%, the castability deteriorates.

Calcium (Ca) is preferably added in the range of 0.4 to 3.2% in order to impart flame retardant properties to the magnesium alloy.

Manganese (Mn) is preferably added in the range of 0.01 to 0.3%. By adding manganese within this range, the influence of iron, which is an impurity element that lowers corrosion resistance, can be mitigated.

In the method for producing a magnesium alloy according to the present embodiment, as shown in FIG. 1, first, a first rolling process of rolling a magnesium alloy having the above composition with a rolling reduction of 40% or more is performed (step S10). A general rolling mill can be used in the first rolling process. The first rolling process is not particularly limited, but for example, the rolling process is performed so that the total reduction rate is 40% or more at a reduction rate of 5 to 20% with respect to the original plate thickness per pass. Can be done. The roll gap of the rolling mill is not particularly limited, but can be the same up to two times.

Next, in the method for producing a magnesium alloy according to the present embodiment, a heat treatment processing step of heat-treating the magnesium alloy subjected to the first rolling processing step is performed (step S20). In this heat treatment processing step, the magnesium alloy subjected to the first rolling processing step is heat-treated, for example, at a temperature about 15 to 120 ° C. lower than the solidus line temperature of the magnesium alloy for about 10 minutes to 10 hours. It is possible to do so. Here, the solidus temperature is measured by measuring a magnesium alloy piece cut into a block of about 15 mg using a differential thermal analyzer (TG-DTA, manufactured by Rigaku), and the first peak temperature obtained is the temperature. The solidus temperature was used. For AZ61, the temperature at which the first peak temperature was obtained and the weight change was started was defined as the solid phase temperature. As a result, the solidus temperature of AZ61 is about 530 ° C, the solidus temperature of AZX611 is about 553 ° C, the solidus temperature of AZX612 is about 522 ° C, and the solidus temperature of AZX811 is about. It was 516 ° C, the solidus temperature of AZX813 was about 530 ° C, and the solidus temperature of AMX1001 was about 502 ° C. Therefore, the heat treatment processing temperatures suitable for various magnesium alloys are about 410 to 515 ° C for AZ61, about 433 to 538 ° C for AZX611, about 402 to 505 ° C for AZX612, and about 396 to 501 ° C for AZX811. The temperature of AZX813 is about 410-515 ° C, and that of AMX1001 is about 382-487 ° C.

In the magnesium alloy subjected to the first rolling process, the crystallized products or intermetallic compounds formed at the grain boundaries of the magnesium phase are located at the grain boundaries as shown in the segment (a) in FIG. It is formed in the form of lumps, plates or granules. Here, as shown in the fractional diagram (a) in FIG. 2, "plate-like" indicates a state in which at least one or more magnesium crystal grains or magnesium phase crystal grain boundaries are formed in a plate shape. “Granular” refers to a state in which at least one or more magnesium crystal grains or magnesium phase crystal grain boundaries are formed granularly. Further, "lumpy" means a very large one as compared with a "plate-like" or "granular" crystallized product or an intermetallic compound, and straddles the grain boundaries of some magnesium crystal grains or magnesium phases. There is something that exists.

By subjecting the magnesium alloy subjected to the first rolling process to the heat treatment process under the above conditions, the Vickers hardness is HV60 or more, and the average crystal grain size of the magnesium phase is 10 to 30 μm. The crystallized product or the intermetallic compound formed at the grain boundaries of the magnesium phase is formed in a plate shape or granules at the grain boundaries as shown in the fractional diagram (b) in FIG. That is, by subjecting the magnesium alloy subjected to the first rolling process to the heat treatment process, the presence of large lumpy crystallized substances or intermetallic compounds is no longer recognized.

Further, the magnesium alloy subjected to the heat treatment processing step is subjected to a second rolling processing step of performing the rolling process again (step S30). A general rolling mill can be used in the second rolling process. The roll temperature of the roll of the rolling mill is preferably 50 to 150 ° C. Further, the magnesium alloy material to be subjected to the second rolling process is preferably heated to a temperature exceeding 350 ° C. Further, the amount of reduction per pass is preferably 5% or more with respect to the original plate thickness. Furthermore, the difference between the roll temperature and the temperature of the material is preferably 200 to 380 ° C.

By performing the second rolling process on the magnesium alloy subjected to the heat treatment process described above under the above conditions, the magnesium phase becomes finer and magnesium is formed as shown in the fraction (c) in FIG. Crystallized products or intermetallic compounds formed in the form of plates or granules are finely dispersed at the crystal grain boundaries of the phase. In the magnesium alloy material subjected to the second rolling process, the average crystal grain size of the magnesium phase is 25 μm or less, the equivalent circular diameter of the crystallized product or the intermetallic compound is 0.1 to 9 μm, and the average thereof. The value is 7 μm or less. Here, the equivalent circular diameter of the crystallized product or the intermetallic compound is the diameter (D) calculated from the formula of crystal grain area: A = π / 4 × D ² assuming that the crystallized product or the intermetallic compound is circular. ). Further, the interval between the crystallized products of the magnesium alloy material or the intermetallic compound subjected to the second rolling process is 0.14 μm or more. Here, the interval between the crystallized product or the intermetallic compound was determined from an FE-SEM observation photograph using a field emission scanning electron microscope (FE-SEM; JEOL 7001 manufactured by JEOL Ltd.) as described later.

Further, when the second rolling process is applied to the magnesium alloy subjected to the heat treatment process, the tensile strength in the rolling direction (parallel to the direction) is 300 MPa or more and the strain at break is 0.1 or more. -A highly ductile magnesium alloy material can be obtained. The magnesium alloy material subjected to this second rolling process has a tensile strength in the 45 ° direction or 90 ° direction with respect to the rolling direction in the second rolling process, and has a tensile strength in the rolling direction (0 ° direction) in the second rolling process. ), The tensile strength value is ± 6%, and the strain in the 45 ° or 90 ° direction with respect to the rolling direction in the second rolling process is when the second rolling process breaks in the rolling direction (0 ° direction). The strain value is within ± 17%. Therefore, according to the method for producing a magnesium alloy according to the present embodiment, it is possible to obtain a high-performance magnesium alloy material in which anisotropy is not observed in the mechanical properties.

From the above, according to the method for producing a magnesium alloy according to the present embodiment, the massive, plate-like or granular crystallized product or intermetallic compound produced by subjecting the above-mentioned magnesium alloy to the first rolling process is heat-treated. It becomes plate-shaped or granular depending on the processing process. Then, by subjecting the magnesium alloy to the second rolling process, the above-mentioned plate-like or granular crystallized products or intermetallic compounds are finely dispersed, and have high strength and high ductility and are anisotropic to mechanical properties. It is possible to obtain a high-performance magnesium alloy material in which is not recognized.

The method for producing a magnesium alloy according to this embodiment has been described above. Next, analysis results and test results showing the characteristics of the magnesium alloy obtained by the method for producing the magnesium alloy according to the present embodiment will be described.

The structure of the magnesium alloy obtained by the above-mentioned magnesium alloy production method was observed using an optical microscope and a scanning electron microscope (SEM; JCM-6000, manufactured by JEOL Ltd.). Here, in the nomenclature of the alloy name, "A" represents "Al", "Z" represents "Zn", "X" represents "Ca", and "M" represents "Mn". Represent. The numbers following the alphabet represent the approximate addition concentration (mass%) of each element. For example, the approximate concentration of the additive element of AZX811 is Mg-8mass% Al-1mass% Zn-1mass% Ca.

[Magnesium alloy subjected to the first rolling process]
First, the inventors analyzed a magnesium alloy having the above-mentioned composition and subjected to a first rolling process. Here, FIG. 3 is a micro observation photograph showing the metal structure of the magnesium alloy subjected to the first rolling process according to the present embodiment, and FIG. 3A in FIG. 3 is the first rolling process. AMX1001 is subjected to the above, and the fraction (b) in FIG. 3 is the AZX811 subjected to the first rolling process.

As shown in the fraction (a) in FIG. 3, the AMX1001 alloy, which has been rolled with a rolling reduction of 50% as the first rolling step, has a plate-like or intermetallic compound with coarse lumpy crystallization. It can be seen that granular crystallized products or intermetallic compounds are present. The average crystal grain size of the magnesium phase of this magnesium alloy was 19 μm. Further, as shown in the fraction (b) in FIG. 3, the AZX811 alloy, which has been rolled with a rolling reduction of 50% as the first rolling process, contains plate-like or granular crystallized substances or intermetallic compounds. It turns out that it exists. The average crystal grain size of the magnesium phase of this magnesium alloy was 18 μm.

[Magnesium alloy with heat treatment process]
Next, the inventors analyze and test the magnesium alloy subjected to the first rolling process, and the magnesium alloy subjected to the heat treatment process according to the present embodiment and the heat treatment process according to the comparative example. It was. Here, FIG. 4 is a micro-observation photograph showing the metallographic structure of the heat-treated magnesium alloy according to the present embodiment and the heat-treated magnesium alloy according to the comparative example, and the components in FIG. FIG. (A) is a micro-observation photograph showing the metal structure of AMX1001 subjected to the heat treatment processing step according to the present embodiment in which heat treatment processing is performed at 450 ° C. for 5 hours, and FIG. 4 (b) in FIG. 4 is a microscopic observation photograph. It is a micro observation photograph which shows the metal structure of AMX1001 which performed the heat treatment process which concerns on the comparative example which performs the heat treatment process at 490 degreeC for 1 hour. Further, FIG. 5 is a micro-observation photograph showing the metal structure of the magnesium alloy subjected to the heat treatment processing step according to the present embodiment, and FIG. 5A in FIG. 5 shows the heat treatment processing at 400 ° C. for 10 minutes. It is a micro observation photograph which shows the metal structure of AZX811 which performed the heat treatment process to perform, and the fraction (b) in FIG. 5 is the metal of AZX811 which performed the heat treatment process which performs the heat treatment process at 500 degreeC for 1 hour. It is a micro-observation photograph showing a structure, and the fraction (c) in FIG. 5 is a micro-observation photograph showing a metal structure of AZX612 subjected to a heat treatment processing step of performing a heat treatment process at 450 ° C. for 10 hours.

As the heat treatment processing step according to the embodiment, the AMX1001 alloy subjected to the heat treatment processing at 450 ° C., which is 52 ° C. lower than the solid phase line temperature of the AMX1001 alloy, 502 ° C., for 5 hours is shown in the segment (a) in FIG. As shown, the crystallized material or intermetallic compound formed at the crystal grain boundary of the magnesium phase is formed as a plate or granular material at the crystal grain boundary, and there is no coarse lumpy crystallized product or intermetallic compound. I understand. The average crystal grain size of the magnesium phase of this magnesium alloy was 22 μm.

On the other hand, as the heat treatment process according to the comparative example, the AMX1001 alloy subjected to the heat treatment process at 490 ° C., which is 12 ° C. lower than the solid phase line temperature of the AMX1001 alloy, for 1 hour, is as shown in the fraction (b) in FIG. It can be seen that the crystallized products or intermetallic compounds formed at the grain boundaries of the magnesium phase exist in a coarse and network-like manner and are not completely dispersed. The average crystal grain size of the magnesium phase of this magnesium alloy was 20 μm.

As described above, by performing the heat treatment processing step on the magnesium alloy subjected to the first rolling processing step under the above-mentioned temperature conditions, rearrangement of the crystallized product or the intermetallic compound occurs, and the crystallized product or the said It was confirmed that the intermetallic compound was finely present in the crystal grain boundary of the magnesium phase in the form of plates or granules.

Furthermore, the inventors obtained a suitable heat treatment processing time for the heat treatment processing step according to the present embodiment from the analysis and test results of the following examples.

As shown in FIG. 5A, the heat treatment process according to the present embodiment is performed for 10 minutes at 400 ° C., which is 116 ° C. lower than the solid phase line temperature of the AZX811 alloy, 516 ° C. It can be seen that in the AZX811 alloy, the crystallized products or intermetallic compounds formed at the grain boundaries of the magnesium phase are formed in plate-like or granular form at the grain boundaries. The average crystal grain size of the magnesium phase of this magnesium alloy was 18 μm.

As shown in the intermetallic diagram (b) in FIG. 5, as the heat treatment processing step according to the present embodiment, heat treatment processing is performed at 500 ° C., which is 16 ° C. lower than the solid phase line temperature of the AZX811 alloy, 516 ° C., for 1 hour. In the AZX811 alloy, the crystallized products or intermetallic compounds formed at the crystal grain boundaries of the magnesium phase are formed in plate or granular form at the crystal grain boundaries, and there are no coarse lumpy crystals or intermetallic compounds. I understand. The average crystal grain size of the magnesium phase of this magnesium alloy was 20 μm.

As shown in the fraction (c) in FIG. 5, as the heat treatment processing step according to the present embodiment, the AZX612 was heat-treated at 450 ° C., which is 72 ° C. lower than the solid phase temperature of the AZX612 alloy, 522 ° C. for 10 hours. In the alloy, as in the above-mentioned examples, the crystallized product or the intermetallic compound formed at the crystal grain boundary of the magnesium phase is formed in a plate shape or a granular shape at the crystal grain boundary, and the crystallized product or the metal in the form of a coarse mass is formed. It can be seen that there is no intermetallic compound. The average crystal grain size of the magnesium phase of this magnesium alloy was 14 μm.

In this way, the magnesium alloy subjected to the first rolling process is subjected to a heat treatment process in which the magnesium alloy is heat-treated at a temperature about 15 to 120 ° C. lower than the solidus line temperature for about 10 minutes to 10 hours. , As shown in FIG. 2B, crystallized products or intermetallic compounds formed at the grain boundaries of the magnesium phase are formed at the grain boundaries in the form of plates or granules, resulting in coarse lumpy crystallization. It was confirmed that there were no substances or intermetallic compounds.

Here, various magnesium alloys subjected to the first rolling process were heat-treated under different temperature and time conditions, and the Vickers hardness of the obtained magnesium alloy was measured. The result is shown in FIG. As can be seen from FIG. 6, when the magnesium alloy subjected to the first rolling process is heat-treated, the Vickers hardness becomes HV60 or more.

[Magnesium alloy material subjected to the second rolling process]
Next, the inventors perform the first rolling process according to the present embodiment, and then perform the second rolling process again on the magnesium alloy subjected to the heat treatment process according to the present embodiment. The magnesium alloy material obtained by performing the rolling process was analyzed. Here, FIG. 7 is a micro-observation photograph showing the metallographic structure of AZX811 subjected to the second rolling process after the heat treatment process according to the present embodiment.

The inventors have performed a rolling process with a rolling reduction of 50% as the first rolling process according to the present embodiment, and then heat-treated for 1 hour at 460 ° C., which is 56 ° C. lower than the solidus line temperature of AZX811. The AZX811 that had been subjected to the heat treatment processing step for processing was subjected to rolling processing with a rolling reduction ratio of 75% as the second rolling processing step to obtain a magnesium alloy material. The result is shown in FIG. As shown in FIG. 7, in the magnesium alloy material produced by the method for producing a magnesium alloy according to the present embodiment, the magnesium phase becomes finer and the crystallites or intermetallics formed at the crystal grain boundaries of the magnesium phase It can be seen that the compounds are discontinuous and finely dispersed. Further, it is confirmed that the crystallized product or the intermetallic compound exists in a curved line, although it is discontinuous. Further, crystallized substances or intermetallic compounds are formed not only in the direction parallel to the rolling direction but also in the grain boundaries in the direction substantially perpendicular to the rolling direction. With such a configuration, according to the present embodiment, it is considered possible to obtain a magnesium alloy material in which anisotropy is not observed in the mechanical properties.

Further, the inventors have divided the magnesium alloy subjected to the first rolling process into a magnesium alloy subjected to the heat treatment process according to the present embodiment and a magnesium alloy subjected to the heat treatment process according to the comparative example. , The magnesium alloy material subjected to the second rolling process, which is subjected to the re-rolling process, was analyzed and tested. Here, FIG. 8 shows a magnesium alloy material obtained by subjecting a second rolling process to a magnesium alloy subjected to the heat treatment process according to the present embodiment and a heat treatment process according to a comparative example. FIG. 8A is a diagram showing an SEM observation photograph of the above, in which FIG. 8A is a second rolling process applied to the AMX1001 subjected to the heat treatment process according to the present embodiment. The fractional diagram (b) in FIG. 8 shows the AMX1001 subjected to the heat treatment processing according to the comparative example subjected to the second rolling process, and the fractional diagram (c) in FIG. 8 relates to the present embodiment. The second rolling process is applied to the AZX612 that has been subjected to the heat treatment process, and the fraction (d) in FIG. 8 shows the second rolling process of the AZX612 that has been subjected to the heat treatment process according to the comparative example. Is given. Further, FIG. 9 is a diagram showing an SEM observation photograph of the magnesium alloy material obtained by subjecting the magnesium alloy subjected to the heat treatment processing step according to the present embodiment to the second rolling processing step, and is shown in FIG. FIG. (A) shows the AZX811 subjected to the heat treatment processing step according to the present embodiment to undergo the second rolling processing step, and FIG. 9 (b) in FIG. 9 shows the heat treatment according to the present embodiment. The second rolling process is applied to the AZX811 subjected to the processing step, and the fraction (c) in FIG. 9 shows the second rolling process on the AZX612 subjected to the heat treatment processing step according to the present embodiment. It has been processed. Further, FIG. 10 is a diagram showing an FE-SEM observation photograph showing the spacing between crystallized substances or intermetallic compounds. In the SEM observation photographs of FIGS. 8, 9 and 10, the white and gray portions indicate crystallized substances or intermetallic compounds. Here, some of the crystals that are not crystallized or intermetallic compounds are white or gray due to the concentration bias due to etching after tissue polishing and the crystal grains, but they are excluded from the evaluation target. The equivalent circular diameter D of the crystallized product or the intermetallic compound is calculated from the formula of crystal grain area: A = π / 4 × D ² assuming that the crystallized product or the intermetallic compound is circular as described above. did. Moreover, the interval of the crystallized product or the intermetallic compound was determined from the FE-SEM observation photograph as described above.

As shown in the fraction (a) in FIG. 8, as the heat treatment processing step according to the present embodiment, heat treatment processing is performed at 450 ° C., which is 52 ° C. lower than the solid phase line temperature of the AMX1001 alloy, 502 ° C., for 5 hours. When the AMX1001 is subjected to a second rolling process in which a rolling process with a rolling reduction of 75% is performed, the magnesium phase becomes finer and the crystallized matter or the intermetallic compound formed at the crystal grain boundary of the magnesium phase becomes finer. , It was confirmed that it was discontinuous and finely dispersed. That is, the state is as shown in the segment diagram (c) in FIG. The area ratio of the crystallized product or the intermetallic compound is 6.9%, the equivalent circle diameter of the crystallized product or the intermetallic compound is 1.0 to 8.6 μm, and the average diameter of the equivalent circle diameter is 6. It was 5.5 μm.

On the other hand, as shown in the fraction (b) in FIG. 8, as the heat treatment process according to the comparative example, the heat treatment process was performed at 490 ° C., which is 12 ° C. lower than the solidus line temperature of the AMX1001 alloy, 502 ° C., for 1 hour. When the AMX1001 is subjected to a second rolling process of rolling with a rolling reduction of 75%, it can be seen that the crystallized substances or intermetallic compounds existing in the network are not completely dispersed even after the rolling process. .. The area ratio of the crystallized product or the intermetallic compound is 11.0%, the equivalent circle diameter of the crystallized product or the intermetallic compound is 1.0 to 15.2 μm, and the average diameter of the equivalent circle diameter is 6. It was .2 μm.

Further, as shown in the fraction (c) in FIG. 8, as the heat treatment processing step according to the present embodiment, the heat treatment processing is performed at 500 ° C., which is 22 ° C. lower than the solid phase line temperature of the AZX612 alloy, for 1 hour. When the applied AZX612 is subjected to a second rolling process for rolling with a rolling reduction of 75%, the magnesium phase becomes finer and is formed at the crystal grain boundaries of the magnesium phase, as in the case described above. It was confirmed that the crystallized product or the intermetallic compound was discontinuous and finely dispersed. That is, the state is as shown in the segment diagram (b) in FIG. The area ratio of the crystallized product or the intermetallic compound was 6.5%, the equivalent circular diameter of the crystallized product or the intermetallic compound was 0.1 to 3.4 μm, and the average diameter was 1.0 μm. ..

On the other hand, as shown in the fraction (d) in FIG. 8, as the heat treatment process according to the comparative example, the heat treatment process was performed at 400 ° C., which is 122 ° C. lower than the solidus line temperature of the AZX612 alloy, 522 ° C. for 1 hour. When the AZX612 is subjected to a second rolling process of rolling with a rolling reduction of 75%, the crystallized substances or intermetallic compounds existing in the net are dispersed even after the rolling process, as in the case described above. You can see that it is not rolling. The area ratio of the crystallized product or the intermetallic compound is 8.2%, the equivalent circle diameter of the crystallized product or the intermetallic compound is 0.1 to 14.0 μm, and the average diameter of the equivalent circle diameter is 5. It was .2 μm.

Further, as shown in FIG. 9A, as the heat treatment processing step according to the present embodiment, a 10-minute heat treatment process is performed at 400 ° C., which is 116 ° C. lower than the solid phase line temperature of the AZX811 alloy, 516 ° C. When the applied AZX811 is subjected to a second rolling process for rolling with a rolling reduction of 75%, the magnesium phase becomes finer and is formed at the crystal grain boundaries of the magnesium phase, as in the case described above. It was confirmed that the crystallized product or the intermetallic compound was discontinuously and finely dispersed. That is, the state is as shown in the segment diagram (b) in FIG. The area ratio of the crystallized product or the intermetallic compound is 3.4%, the equivalent circle diameter of the crystallized product or the intermetallic compound is 0.1 to 4.1 μm, and the average diameter of the equivalent circle diameter is 1. It was 5.5 μm.

Further, as shown in the fraction (b) in FIG. 9, as the heat treatment processing step according to the present embodiment, the heat treatment processing is performed at 500 ° C., which is 16 ° C. lower than the solid phase line temperature of the AZX811 alloy, which is 516 ° C., for 1 hour. When the applied AZX811 is subjected to a second rolling process for rolling with a rolling reduction of 75%, the magnesium phase becomes finer and is formed at the crystal grain boundaries of the magnesium phase, as in the case described above. It was confirmed that the crystallized product or the intermetallic compound was discontinuously and finely dispersed. That is, the state is as shown in the segment diagram (b) in FIG. The area ratio of the crystallized product or the intermetallic compound is 3.1%, the equivalent circle diameter of the crystallized product or the intermetallic compound is 0.1 to 4.0 μm, and the average diameter of the equivalent circle diameter is 1. It was .3 μm.

Further, as shown in the fraction (c) in FIG. 9, as the heat treatment processing step according to the present embodiment, heat treatment processing is performed at 450 ° C., which is 72 ° C. lower than the solid phase line temperature of AZX612 alloy, for 10 hours. When the applied AZX612 is subjected to a second rolling process for rolling with a rolling reduction of 75%, the magnesium phase becomes finer and is formed at the crystal grain boundaries of the magnesium phase, as in the case described above. It was confirmed that the crystallized product or the intermetallic compound was discontinuously and finely dispersed. That is, the state is as shown in the segment diagram (c) in FIG. The area ratio of the crystallized product or the intermetallic compound is 6.4%, the equivalent circle diameter of the crystallized product or the intermetallic compound is 0.1 to 6.4 μm, and the average diameter of the equivalent circle diameter is 2. It was .2 μm.

Further, as shown in FIG. 10, in the AZX811 as a magnesium alloy subjected to the second rolling process, the spacing between the crystallized substances or the intermetallic compounds formed discontinuously shall be 0.14 μm or more. I found out.

From the above, when the magnesium alloy subjected to the heat treatment processing step according to the present embodiment is subjected to the second rolling processing step, the magnesium phase becomes finer and the crystallized product formed at the crystal grain boundary of the magnesium phase or It was found that the intermetallic compound was discontinuous and finely dispersed. The area ratio of the crystallized product or the intermetallic compound is 7% or less, the equivalent circle diameter of the crystallized product or the intermetallic compound is 0.1 to 9 μm, and the average diameter of the equivalent circle diameter is 7 μm or less. It was confirmed that It was also found that the interval between the crystallized products or the intermetallic compounds was 0.14 μm or more. On the other hand, it was confirmed that even if the second rolling process was performed on the heat-treated magnesium alloy according to the comparative example, the crystallized products or the intermetallic compounds existing in the network were not completely dispersed.

Further, the inventors conducted a mechanical property test on the magnesium alloy material produced by the method for producing a magnesium alloy according to the present embodiment and the magnesium alloy material according to a comparative example. Here, the measurement of the tensile strength of the magnesium alloy material is a room temperature tensile test at a quasi-static strain rate according to the JIS Z2241 metal material tensile test method, and is a direction parallel to the rolling direction (0 ° direction), 45. The test was performed in the ° direction and the 90 ° direction. More specifically, in the tensile test, the magnesium alloy material was rolled in the rolling direction, the 45 ° direction, and the 90 ° direction, and the plate thickness of the magnesium alloy material was left as it was, and the parallel portion dimensions were width 5 mm × length 30 mm and width 12.5 mm. A plate-shaped test piece having a length of 60 mm was prepared, and the test piece was used at room temperature at an initial strain rate of 1.1 × 10 ^-3 s- ¹ . The breaking strain of the magnesium alloy material was measured based on the JIS Z2241 metal material tensile test method. The results are shown in Table 1.

As shown in Table 1, when the second rolling process is applied to the magnesium alloy subjected to the heat treatment process according to the present embodiment, the tensile strength in the rolling direction (0 ° direction) of the second rolling process is 300 MPa or more. It can be seen that the strain at break is 0.1 or more. That is, according to the method for producing a magnesium alloy according to the present embodiment, it is possible to obtain a magnesium alloy material having high strength and high ductility.

Further, when the second rolling process is performed on the magnesium alloy subjected to the heat treatment process according to the present embodiment, the tensile strength in the 45 ° direction or 90 ° direction with respect to the rolling direction of the second rolling process becomes the second. (Ii) The value of the tensile strength in the rolling direction of the rolling process is ± 6%, and the strain in the 45 ° or 90 ° direction with respect to the rolling direction of the second rolling process is a break in the rolling direction of the second rolling process. The value of rolling strain is within ± 17%. That is, it was confirmed that the magnesium alloy material obtained by the method for producing a magnesium alloy according to the present embodiment does not show anisotropy in mechanical properties.

Therefore, according to the method for producing a magnesium alloy according to the present embodiment, it is possible to obtain a high-performance magnesium alloy material having high strength and high ductility and having no anisotropy in mechanical properties.

Although the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the scope described in the above embodiments. Various changes or improvements can be made to the above embodiments. It is clear from the description of the claims that such modified or improved forms may also be included in the technical scope of the present invention.

S10 first rolling process, S20 heat treatment process, S30 second rolling process.

Claims (3)

After performing the first rolling process of rolling a magnesium alloy with a rolling reduction of 40% or more, heat treatment is performed for 10 minutes to 10 hours at a temperature 15 to 120 ° C. lower than the solidus temperature of the magnesium alloy. In the method for producing a magnesium alloy, which is subjected to a second rolling process in which the process is performed and the magnesium alloy subjected to the heat treatment process is further rolled.
The magnesium alloy subjected to the second rolling process has a tensile strength of 300 MPa or more in the rolling direction of the second rolling process, a strain at break of 0.1 or more, and further.
The magnesium alloy subjected to the second rolling process has a tensile strength in the 45 ° direction or 90 ° direction with respect to the rolling direction of the second rolling process, and a tensile strength in the rolling direction of the second rolling process. The value of ± 6%, and the strain in the 45 ° or 90 ° direction with respect to the rolling direction of the second rolling process is ± 17% of the strain value at break in the rolling direction of the second rolling process. A method for producing a magnesium alloy, which is characterized by being within. In the method for producing a magnesium alloy according to claim 1,
The second rolling magnesium process is performed alloy has an average crystal grain size of the magnesium phase does not exceed 25μm or less, crystallized substances or is at an area ratio of 7% or less relative to the magnesium phase gold intermetallic compound, A method for producing a magnesium alloy, characterized in that the equivalent circular diameter of the crystallized product or the intermetallic compound is 0.1 to 9 μm and the average value thereof is 7 μm or less. In the method for producing a magnesium alloy according to claim 2,
The crystallized product or the intermetallic compound formed at the grain boundary of the magnesium phase is finely dispersed, and the interval between the finely dispersed crystallized product or the intermetallic compound is 0.14 μm. A method for producing a magnesium alloy, which is characterized by the above.