JP2010116618A - Method for manufacturing magnesium alloy material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnesium alloy which has a higher strength than that of a conventional magnesium alloy. <P>SOLUTION: A method for manufacturing the magnesium alloy material includes the steps of: preparing a material to be worked of the magnesium alloy, which contains at least aluminum and zinc as an additive element; subjecting the material to be worked to temperature-lowering multispindle-forging treatment; and rolling the material to be worked which has been subjected to temperature-lowering multispindle-forging treatment, with a rolling reduction of 20% at the maximum. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a magnesium alloy, and more particularly to a method for producing a magnesium alloy containing aluminum and zinc.

  Magnesium alloys are lightweight and have high specific strength, and are expected to be applied as structural materials. Until now, magnesium alloys have been widely used as components for electronic devices, but recently, demand for structural materials for automobiles and the like has begun to increase rapidly. In particular, in the automotive field where weight reduction is in progress for improving fuel efficiency, the use of magnesium alloy has increased to about 5% for high-end cars in Japan, and 12 to 13% for middle-class cars or higher in Western Europe. In the future, application of magnesium alloy to low-priced vehicles is also expected.

  However, it is difficult to say that magnesium alloys currently used have sufficiently high strength as a structural material. Magnesium alloys are known as difficult-to-work materials, and there is a problem that it is difficult to expect the strength improvement effect by work hardening. This is because a magnesium alloy has a small number of active slip systems at room temperature, and when processing is performed, the number of slip systems is further reduced due to the texture formed. Accordingly, when a process such as a rolling process is performed on the magnesium alloy, the risk of causing defects such as cracks is extremely high.

Recently, in order to cope with the problem relating to the workability of such a magnesium alloy, a magnesium alloy containing aluminum and zinc (hereinafter referred to as “AZ-based magnesium alloy”) is subjected to a temperature-decreasing multiaxial forging process to obtain crystal grains. It has been proposed to improve the workability of AZ-based magnesium alloys (Patent Document 1).
JP 2007-291488 A

  However, even in the magnesium alloy manufactured by the method described in Patent Document 1, the strength (tensile strength) is only about 320 MPa at the maximum. Therefore, a magnesium alloy having higher strength is desired.

  This invention is made | formed in view of such a background, and it aims at providing the method of manufacturing the magnesium alloy which has high intensity | strength compared with the conventional magnesium alloy.

In the present invention, a method for producing a magnesium alloy material,
Preparing a magnesium alloy work material containing at least aluminum and zinc as additive elements;
Subjecting the work material to a temperature-lowering multi-axis forging process;
Rolling the temperature-decreasing multiaxial forging work material at a rolling reduction of 20% at maximum;
There is provided a method characterized by comprising:

Here, the method according to the invention further comprises:
You may have the step which carries out the aging treatment of the said workpiece material by which the rolling process was carried out.

Moreover, in the method according to the present invention, the step of performing a temperature-decreasing multi-axis forging process on the work material includes
A temperature-decreasing multi-axis forging process step may be performed in which the first pass forging is performed in the range of 573K to 673K and the final pass is forged in the range of 403K to 523K.

Further, in the step of performing the temperature-decreasing multi-axis forging treatment of the work material,
The temperature difference between the N-th pass forging (N is an integer of 1 or more) and the N + 1-th pass forging may be in the range of 10K to 100K.

Moreover, in the method according to the present invention, the step of performing a temperature-decreasing multi-axis forging process on the work material includes
In the N-th pass forging (N is an integer of 1 or more), the workpiece is cooled at a strain rate in the range of 3 × 10 ⁻³ / sec to ³ × 10 ⁻¹ / sec, and the temperature-lowering multiaxial forging process is performed. You may have the step to do.

  In the method according to the present invention, the strain rate in the last pass forging may be larger than the strain rate in the first pass forging.

  Alternatively, in the method according to the present invention, the strain rates in the forging of each pass may be substantially equal.

  Further, in the method according to the present invention, a total strain amount in the range of 1.0 to 6.4 may be introduced into the work material by the step of performing the temperature-decreasing multiaxial forging process on the work material.

  In the method according to the present invention, a workpiece having an average crystal grain size of 2 μm or less may be obtained by subjecting the workpiece to a temperature-decreasing multiaxial forging process.

  In the method according to the present invention, the rolling step may be performed at room temperature.

Also, in the method according to the present invention, the aging treatment step comprises:
You may have the step which carries out the aging process in the temperature range of 373K-473K for the said workpiece material by which the rolling process was carried out.

  In the method according to the present invention, the material to be processed may be a magnesium alloy material containing 2 to 10% by mass of aluminum and 0.1 to 2% by mass of zinc.

The material to be processed further includes
It may contain at least one element selected from the group consisting of manganese, iron, silicon, copper, nickel and calcium.

  For example, the workpiece material may be a magnesium alloy material containing 2.5 to 3.5 mass% aluminum and 0.6 to 1.4 mass% zinc.

  Alternatively, the material to be processed may be a magnesium alloy material containing 5.5 to 7.2% by mass of aluminum and 0.5 to 1.5% by mass of zinc.

  Alternatively, the material to be processed may be a magnesium alloy material containing 8.3 to 9.7% by mass of aluminum and 0.35 to 1.0% by mass of zinc.

  The present invention can provide a method for producing a magnesium alloy having a higher strength than conventional magnesium alloys.

  The present invention will be described in detail below.

  Conventionally, magnesium alloys are known as difficult-to-process materials having poor processability. For example, when a process such as a rolling process is performed on an AZ-based magnesium alloy, defects such as cracks are generated. This is because a magnesium alloy generally has a small number of slip surfaces and tends to form a texture, and slip deformation hardly occurs.

  On the other hand, recently, it has been proposed that the AZ-based magnesium alloy material is subjected to a temperature-decreasing multiaxial forging process to refine the crystal grains, thereby improving the workability of the AZ-based magnesium alloy material. (Patent Document 1 mentioned above). The “temperature-decreasing multi-axis forging process” will be described later.

  However, in this method, although the workability of the obtained AZ-based magnesium alloy material is improved, the strength improvement effect is insufficient, and further strength improvement is required (the tensile strength is 300 at the maximum). About 400 MPa).

  Under such a background, the inventors of the present application proceeded with earnest research on the strength improvement technology of the magnesium alloy material, and further applied a cold rolling process to the magnesium alloy material after the temperature-decreasing multi-axis forging process, thereby obtaining a material. It came to the thought that there was a possibility that it could improve the strength. However, until now, there have been few examples of cold rolling on difficult-to-work magnesium alloy materials, and it has been unclear how far cold rolling is possible. Furthermore, since subsequent plastic working is difficult, there is a background that an increase in strength due to cold rolling has been avoided. Therefore, the inventors of the present application actually perform a temperature-decreasing multi-axis forging process of the magnesium alloy material under various conditions, and the cold rolling process is performed on the obtained magnesium alloy material under various conditions. The experiment was repeated. As a result, the magnesium alloy material after the temperature-decreasing multi-axis forging process can be cold-rolled up to a maximum of 20%. By performing such a process, the strength of the material is actually improved. And, for example, the inventors found that the tensile elongation is not impaired and reached the present invention.

That is, in the present invention, a method for producing a magnesium alloy material,
Preparing a magnesium alloy work material containing at least aluminum and zinc as additive elements;
Subjecting the work material to a temperature-lowering multi-axis forging process;
Rolling the temperature-decreasing multiaxial forging work material at a rolling reduction of 20% at maximum;
There is provided a method characterized by comprising:

  The magnesium alloy material obtained by the method according to the present invention exhibits significantly higher strength than the conventional alloy that has been subjected to the temperature-decreasing multiaxial forging process.

FIG. 1 shows an example of a tensile test result at room temperature of an AZ-based magnesium alloy sample (AZ61) obtained by the method according to the present invention. The strain rate during the test was 8.3 × 10 ⁻² / sec. In addition, the average crystal grain size of the material immediately after the temperature-decreasing multiaxial forging process was about 2 μm or less. The rolling reduction rate during the rolling process of the alloy sample was 15%.

  From this figure, it can be seen that the alloy sample obtained by the method according to the present invention has a tensile strength exceeding about 450 MPa and an extremely good strength can be obtained.

  In the figure, it can be seen that the alloy sample of the present invention exhibits an elongation of about 30%. Generally, the elongation of the AZ-based magnesium alloy material after the temperature-decreasing multiaxial forging process is about 20%. Therefore, it can be seen that the method according to the present invention is effective in improving the workability as well as improving the strength of the magnesium alloy material. This is a characteristic completely different from a general coarse-grained magnesium alloy material, and is a characteristic of an ultrafine-grained magnesium alloy.

  In the method according to the present invention, it is preferable to perform an aging treatment after rolling the magnesium alloy material that has been subjected to temperature-decreasing multiaxial forging at a rolling reduction of 20% at the maximum. Thereby, the strength of the magnesium alloy material is further improved.

  FIG. 2 shows an example of a tensile test result performed using such an alloy sample under the same conditions as in FIG. This alloy sample was obtained by subjecting the alloy sample used in the test of FIG. 1 to an aging treatment at about 423 K for 1 hour. From this figure, it can be seen that the strength of the alloy sample is further improved by adding an aging treatment step.

  Thus, in the method according to the present invention, a magnesium alloy material having a significantly higher strength can be obtained as compared with a material subjected to conventional temperature-decreasing multiaxial forging treatment.

(Manufacturing method of magnesium alloy material according to the present invention)
Hereinafter, the present invention will be described in detail with reference to the drawings. In FIG. 3, an example of the flowchart of the method of manufacturing the magnesium alloy by this invention is shown.

  As shown in FIG. 3, the method according to the present invention includes a step S110 for preparing a work material made of an AZ-based magnesium alloy, a step S120 for performing a temperature lowering multiaxial forging process on the work material, and a temperature lowering multiaxial forging process. Step S130 for cold rolling the material. Further, as described above, the method according to the present invention may further optionally include step S140 of aging the cold-rolled material.

  Hereinafter, each step will be described in detail.

(1. Step of preparing work material)
First, a work material made of an AZ-based magnesium alloy is prepared. The material to be processed may be any magnesium alloy as long as it is an AZ-based magnesium alloy (that is, a magnesium alloy containing aluminum and zinc), and the composition is not particularly limited. For example, the work material may include elements such as manganese (Mn), iron (Fe), silicon (Si), copper (Cu), nickel (Ni), and / or calcium (Ca).

  The material to be processed is, for example, a magnesium alloy (AZ31 alloy) containing about 3 mass% aluminum and about 1 mass% zinc, a magnesium alloy containing about 6 mass% aluminum and about 1 mass% zinc (AZ61 alloy). A magnesium alloy (AZ80 alloy) containing about 8 wt% aluminum and less than about 1 wt% zinc, or a magnesium alloy containing about 9 wt% aluminum and about 1 wt% zinc (AZ91 alloy), etc. Also good.

  Examples of the AZ31 alloy include AZ31B further containing 0.20 to 1.0% by mass of Mn or AZ31M containing 0.025 to 0.06% by mass of Ca. The AZ61 alloy may contain, for example, 0.15 to 0.40 mass% of Mn. The AZ80 alloy may contain, for example, 0.10 to 0.40 mass% of Mn. The AZ91 alloy may contain, for example, 0.15% by mass or more of Mn.

  The average crystal grain size of the work material is not particularly limited. However, the work material having a larger average crystal grain size needs to introduce more strain into the work material in the subsequent cooling down multi-axis forging process step. Occurs. Otherwise, a magnesium alloy structure composed of fine crystal grains cannot be obtained after the temperature-decreasing multiaxial forging process.

  In the present application, the “average crystal grain size” is a value measured by a linear crossing method using an optical microscope and a transmission electron microscope.

(2. Falling temperature multi-axis forging process step)
Next, the above-mentioned work material is subjected to a temperature-decreasing multi-axis forging process.

  Here, “temperature-decreasing multi-axis forging process” means performing “multi-axis forging process” while gradually or stepwise reducing the temperature of the work material for each forging of “multi-axis forging process”. Means the generic name of the method. The “multi-axis forging process” refers to a processing method that repeats compression by changing the forging direction of the work material so that the major axis direction becomes the compression direction for each forging process in one direction.

  In order to better understand the characteristics of such a “temperature-decreasing multi-axis forging process” method, first, a specific example of the “multi-axis forging process” method will be described with reference to FIG.

  FIG. 4 is a diagram schematically illustrating the multi-axis forging method. First, a rectangular work material 4 as shown in FIG. 4A is prepared. Next, the work material 4 is forged along the first direction (X-axis direction) (first pass).

  Next, as shown in FIG. 4B, the work material 4 is forged along the second direction (Y-axis direction) (second pass). Further, as shown in FIG. 4 (3), the work material 4 is forged along the third direction (Z-axis direction) (third pass). The material 4 to be processed returns to the initial shape in appearance by three passes (FIG. 4 (4)).

  Here, the aspect ratio of the work material 4 is determined by the compression ratio by forging from each compression axis direction (X, Y, and Z directions) shown in FIGS. In other words, the aspect ratio of the work material 4 can be changed by the compression rate for each pass to be adopted. For example, in the example of FIG. 4, the aspect ratio of the workpiece 4 is 1.0 (Z direction): 1.49 (Y direction): 2.22 (X direction). This corresponds to the case where the processing strain ε introduced into the workpiece 4 is 0.8 in one pass. Therefore, in the example of FIG. 4, in order to set the total strain amount Σε introduced into the workpiece 4 to 3.2, a total of four passes of processing is necessary.

  It is obvious to those skilled in the art that the numerical values of the processing strain ε and the total strain amount Σε shown here are only examples. The total strain amount Σε introduced by this treatment is preferably in the range of 1.0 to 6.4, for example, in the range of 1.2 to 4.0.

  In general, in such a “multi-axis forging process” method, a large strain is introduced into the work material 4 and a structure composed of fine crystal grains can be obtained.

  However, in the case of a difficult-to-process magnesium alloy material such as an AZ-based magnesium alloy material, even if the “multi-axis forging process” is performed at a constant temperature, fine crystal grains can be obtained in a uniform state and further improved in strength. There is a problem that it is extremely difficult to raise.

  Therefore, in the present invention, the “temperature-decreasing multi-axis forging process” method is applied. FIG. 5 schematically shows the relationship between the processing temperature and the pass (time) in the “temperature-decreasing multi-axis forging process” method.

In cooling multiaxial forging, the first pass is carried out at a temperature T _1. Next, the second pass is performed at a temperature T ₂ (T ₂ <T ₁ ). Similarly, the N-th pass is performed at each temperature T _N , and finally the last pass is performed at the temperature T _L.

  In this method, since the temperature during the forging process is lowered for each pass and the multi-axis forging process of the magnesium alloy is performed, a uniform structure composed of fine crystal grains can be formed relatively easily.

Temperatures _{T 1} during the first time pass, for example, in the range of 573K～673K. Further, the temperature _{TL at} the final pass is, for example, in the range of 403K to 523K, and the temperature difference ΔT between the passes is, for example, in the range of 10K to 100K. Note that the temperature difference ΔT between the passes may be constant or may change with the passes.

  It will be apparent to those skilled in the art that these temperature examples are merely examples, and any temperature conditions suitable for refining the crystal grains of the alloy material may be used.

In the present invention, the strain rate of each pass in the “cooling multiaxial forging process” is usually in the range of 3 × 10 ⁻³ / sec to ³ × 10 ⁻¹ / sec.

  This strain rate may be substantially constant in each pass.

  Alternatively, the strain rate in the last pass forging may be larger than the strain rate in the first pass forging. In normal cases, the crystal grains of the material are refined every time the forging pass is repeated. Therefore, in the last pass or a pass in the vicinity thereof, even if processing is performed at a strain rate larger than that in the first pass, there is little risk that the material will crack or crack. In addition, this makes it possible to perform the “temperature-decreasing multi-axis forging process” more quickly.

In the above expression, only the relationship between the strain rate in the first pass and the last pass is shown. However, it will be apparent to those skilled in the art that the relationship between strain rates in each pass during this period may be any relationship as long as the material does not crack or crack. For example, the strain rate in the second and subsequent passes of forging may be greater than the strain rate in the first pass of forging. Further, for example, the strain rate may be gradually increased (linearly or nonlinearly) for each pass. Alternatively, the first few passes are performed at a relatively low strain rate (eg, on the order of 10 ⁻³ / sec) for the first few passes, and the next few passes are moderate strain rates (eg, ^10-2 was performed in / sec order), the last few passes, the relatively large strain rate (for ^example, carried out in 10 -1 / sec order), be changed to "discontinuous" good.

  The average crystal grain size of the work material obtained after the “temperature-decreasing multiaxial forging process” is, for example, 2 μm or less, or 1 μm or less (for example, 0.8 μm). In addition, in the work material having an average crystal grain size exceeding 2 μm, there is a possibility that the risk of causing cracks and cracks in the material during the next cold rolling process step is increased.

(3. Cold rolling process step)
Next, the forged material is cold-rolled. The method of the cold rolling treatment is not particularly limited. For example, a conventional method of rolling a work material by passing the work material between a pair of rolling rolls using a conveyor belt (so-called roll rolling). Or the like) may be used. The temperature of the cold rolling treatment is not particularly limited, and is, for example, room temperature. The rolling speed (material feed speed by the conveyor belt) is not limited to this, but is, for example, about 1 × 10 ⁻¹ cm / second.

  In FIG. 6, the hardness change after the cold rolling process in each rolling reduction with respect to the magnesium alloy sample after a temperature fall multiaxial forge process is shown. The cold rolling process was performed at room temperature. The triangle symbol represents the result of the sample (AZ61 magnesium alloy) after two passes of the temperature-decreasing multi-axis forging process, and the round and square symbols represent the total of four passes and five passes of the temperature-decreasing multi-axis forging process, respectively. The result in the sample (AZ61 magnesium alloy) after implementation is shown.

  As shown in the figure, it can be seen that the hardness of the material is increased due to the increase in the rolling reduction during the cold rolling process in any number of passes in the temperature-decreasing multiaxial forging process. In the figure, the hardness of the material before the cold rolling process increases as the number of passes in the temperature-decreasing multi-axis forging process increases. This is because the crystal grains are refined by repeating the temperature-decreasing multi-axis forging process. It is because it was done. For example, the average crystal grain sizes of the samples immediately before the rolling process (that is, after the temperature-decreasing multiaxial forging process) are 0.8 μm (square mark: 5 passes), 1.20 μm (circle mark: 4 passes), and 3. 7 μm (triangle mark: 2 passes).

  Even in the case of magnesium alloys, which have been said to be harder to process than before, the increase in hardness of such materials is intended to improve the work hardening effect and further improve the strength by appropriate additional rolling after the temperature-decreasing multi-axis forging process. It shows that it can be done.

  Thus, in this invention, the intensity | strength of material can be improved more by carrying out the cold rolling process of the magnesium alloy material by which the temperature fall multiaxial forge process was carried out.

  Here, in the present invention, the reduction ratio of the material by the cold rolling process is suppressed to about 20% or less. This is because when the rolling reduction exceeds 20%, there is a high risk that the material will be cracked or cracked after the cold rolling process. Moreover, it is preferable that the reduction rate of the material by the cold rolling process is 5% or more. If it is less than 5%, the effect of the cold rolling treatment is reduced.

(4. Aging process step)
Next, if necessary, the cold-rolled material may be further aged. Although the temperature of an aging treatment is not restricted to this, For example, it is the range of 373K-473K. Moreover, the time of an aging treatment is not limited to this, For example, it is the range of several minutes-several hours. The aging treatment may be performed, for example, in an oil bath.

  Through such steps, a magnesium alloy material having high strength can be obtained.

  Examples of the present invention will be described below.

Example 1
An AZ-based magnesium alloy material (Osaka Fuji Industrial Co., Ltd .: AZ61) having the composition shown in Table 1 was prepared. The dimensions of the alloy material are vertical (X direction) 31 mm × horizontal (Y direction) 21 mm × height (Z direction) 14 mm. The average grain size was about 57 μm.

次に、この合金材料を用いて、降温多軸鍛造処理を実施した。まず最初に、温度６２３Ｋで、合金材料の縦方向（Ｘ方向）に沿って、合金材料を鍛造した（第１パス）。第１パスにより導入された歪み量εは、０．８であった（すなわち、鍛造後のＸ方向の寸法は、１４ｍｍ）。次に、合金材料の横方向（Ｙ方向）に沿って、温度５７３Ｋで、合金材料を鍛造した（第２パス）。第２パスにより導入された歪み量εは、０．８であった（すなわち、鍛造後のＹ方向の寸法は、１４ｍｍ）。次に、合金材料の高さ方向（Ｚ方向）に沿って、温度５２３Kで、合金材料を鍛造した（第３パス）。第３パスにより導入された歪み量εは、０．８であった（すなわち、鍛造後のＺ方向の寸法は、１４ｍｍ）。次に、再度合金材料の縦方向（Ｘ方向）に沿って、温度５０３Ｋで、合金材料を鍛造した（第４パス）。第４パスにより導入された歪みεは、０．８であった。以上の降温多軸鍛造工程により、合金材料には、合計３．２の累積歪みΣεが導入された。各パスにおいて、ひずみ速度は、いずれも３×１０−^３／ｓｅｃとした。

Next, a temperature-decreasing multiaxial forging process was performed using this alloy material. First, the alloy material was forged at a temperature of 623 K along the longitudinal direction (X direction) of the alloy material (first pass). The strain amount ε introduced by the first pass was 0.8 (that is, the dimension in the X direction after forging was 14 mm). Next, the alloy material was forged at a temperature of 573 K along the transverse direction (Y direction) of the alloy material (second pass). The strain amount ε introduced by the second pass was 0.8 (that is, the dimension in the Y direction after forging was 14 mm). Next, the alloy material was forged at a temperature of 523 K along the height direction (Z direction) of the alloy material (third pass). The strain amount ε introduced by the third pass was 0.8 (that is, the dimension in the Z direction after forging was 14 mm). Next, the alloy material was forged again at a temperature of 503 K along the longitudinal direction (X direction) of the alloy material (fourth pass). The strain ε introduced by the fourth pass was 0.8. Through the above temperature-decreasing multiaxial forging process, a total of 3.2 cumulative strain Σε was introduced into the alloy material. In each pass, the strain rate was 3 × 10 ⁻³ / sec.

  The average crystal grain size of the alloy material after the temperature-decreasing multiaxial forging process was about 1.2 μm.

  Next, cold rolling treatment was performed using the obtained alloy material. The cold rolling treatment was performed by a conventional roll rolling method at room temperature, and the reduction rate was 15%.

  Next, an aging treatment was performed using the alloy material after rolling. The aging treatment was performed by holding the rolled alloy material for 1 hour in an oil bath having a temperature of 423K.

  The sample according to Example 1 was obtained through the above steps.

(Example 2)
A sample according to Example 2 was produced in the same manner as in Example 1. However, in this Example 2, the aging treatment was not performed on the alloy material after rolling.

(Comparative Example 1)
An AZ-based magnesium alloy material (Osaka Fuji Industrial Co., Ltd .: AZ61) having the composition shown in Table 1 was prepared. The dimensions of the alloy material are vertical (X direction) 31 mm × horizontal (Y direction) 21 mm × height (Z direction) 14 mm. The average grain size was about 57 μm.

Next, using this alloy material, a temperature-decreasing multiaxial forging process of a total of 4 passes was performed under the same conditions as in Example 1. The cumulative strain Σε was 3.2. In each pass, the strain rate was 3 × 10 ⁻³ / sec. The average crystal grain size of the alloy material after the temperature-decreasing multiaxial forging process was about 1.2 μm.

  The alloy sample thus obtained is referred to as a sample according to Comparative Example 1. In the sample according to Comparative Example 1, the cold rolling process and the aging process are not performed.

(Comparative Example 2)
An aging treatment was performed using the sample according to Comparative Example 1. The aging treatment was performed by holding the rolled alloy material for 1 hour in an oil bath having a temperature of 423K.

  The alloy sample thus obtained is referred to as a sample according to Comparative Example 2.

(Strength evaluation of each sample)
A tensile test was carried out using each sample produced by the method described above. An Instron type tensile tester (model number TENSILON UCT-10T) was used as the tensile tester. The strain rate applied to the sample was 8.3 × 10 ⁻² / sec. The test was conducted at room temperature.

  FIG. 7 collectively shows the results (stress-strain curves) obtained for each sample.

  First, in the sample according to Comparative Example 1 (sample in which only the temperature-decreasing multiaxial forging process was performed), the tensile strength was about 400 MPa and the elongation was about 20%. Further, the sample according to Comparative Example 2 (the sample subjected to the aging treatment after the temperature-decreasing multiaxial forging process) had a tensile strength of about 400 MPa, which was the same as the sample according to Comparative Example 1. The elongation was about twice that of the sample according to Comparative Example 1.

  On the other hand, in the sample according to Example 2 (sample in which only cold rolling treatment was performed after the temperature-decreasing multi-axis forging), the tensile strength increased to about 450 MPa. Also, the elongation was about 1.5 times that of Comparative Example 1. Further, in the sample according to Example 1 (the sample subjected to the cold rolling treatment and the aging treatment after the temperature-decreasing multiaxial forging), the tensile strength reached about 550 MPa. Also, the elongation increased about 1.5 times compared to the sample according to Comparative Example 1.

  Thus, in the samples according to Examples 1 and 2, it was found that the strength was significantly increased as compared with Comparative Examples 1 and 2.

  As described above, according to the method of the present invention, the strength of the magnesium alloy can be significantly improved without impairing the workability of the magnesium alloy.

  The present invention can be applied to a method for producing a magnesium alloy.

It is the figure which showed an example of the tension test result of the magnesium alloy obtained by the method by this invention. It is the figure which showed an example of the tension test result of the magnesium alloy obtained by another method by this invention. It is an example of the flowchart of the manufacturing method of the magnesium alloy by this invention. It is the figure which showed schematically an example of the multi-axis forge processing method. It is the figure which showed typically an example of the relationship between the temperature and time in the temperature fall multi-axis forge processing method. It is the figure which showed the relationship between the reduction rate in the case of a cold rolling process, and the hardness of a sample in the sample after temperature-fall multi-axis forging process. It is the figure which showed the tension test result of each sample.

Explanation of symbols

  4 Work material

Claims (16)

A method for producing a magnesium alloy material comprising:
Preparing a magnesium alloy work material containing at least aluminum and zinc as additive elements;
Subjecting the work material to a temperature-lowering multi-axis forging process;
Rolling the temperature-decreasing multiaxial forging work material at a rolling reduction of 20% at maximum;
A method characterized by comprising: further,
The method according to claim 1, further comprising the step of aging treatment of the rolled workpiece material. The step of subjecting the workpiece material to a temperature-decreasing multi-axis forging process includes:
The temperature-decreasing multi-axis forging process step of forging the first pass in the range of 573K to 673K and forging the final pass in the range of 403K to 523K is provided. Method. In the step of subjecting the work material to a temperature-lowering multi-axis forging process,
The temperature difference between the forging of the Nth pass (N is an integer of 1 or more) and the forging of the (N + 1) th pass is in the range of 10K to 100K. The method as described in one. The step of subjecting the workpiece material to a temperature-decreasing multi-axis forging process includes:
In the N-th pass forging (N is an integer of 1 or more), the workpiece is cooled at a strain rate in the range of 3 × 10 ⁻³ / sec to ³ × 10 ⁻¹ / sec, and the temperature-lowering multiaxial forging process is performed. The method according to claim 1, further comprising the step of:   The method according to any one of claims 1 to 5, wherein a strain rate in the last pass forging is larger than a strain rate in the first pass forging.   6. A method according to any one of claims 1 to 5, characterized in that the strain rates in the forging of each pass are substantially equal.   The total strain amount in the range of 1.0 to 6.4 is introduced into the work material by the step of performing the temperature-decreasing multiaxial forging process on the work material. The method according to one.   The method according to any one of claims 1 to 8, wherein the material to be processed having an average crystal grain size of 2 µm or less is obtained by performing the temperature-decreasing multiaxial forging process on the material to be processed.   The method according to claim 1, wherein the rolling is performed at room temperature. The aging treatment step includes:
The method according to any one of claims 2 to 10, further comprising the step of aging the rolled material to be processed in a temperature range of 373K to 473K.   The said work material is a magnesium alloy material containing 2-10 mass% aluminum and 0.1-2 mass% zinc, It is any one of Claim 1 thru | or 11 characterized by the above-mentioned. Method. The workpiece material further includes:
13. The method of claim 12, comprising at least one element selected from the group consisting of manganese, iron, silicon, copper, nickel and calcium.   The work material is a magnesium alloy material containing 2.5 to 3.5% by mass of aluminum and 0.6 to 1.4% by mass of zinc. the method of.   The said work material is a magnesium alloy material containing 5.5-7.2 mass% aluminum and 0.5-1.5 mass% zinc, The Claim 12 or 13 characterized by the above-mentioned. the method of.   14. The work material is a magnesium alloy material containing 8.3 to 9.7% by mass of aluminum and 0.35 to 1.0% by mass of zinc. the method of.

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