JP7078839B2 - Magnesium alloy, its manufacturing method, and electronic equipment - Google Patents

Description

The present invention relates to a magnesium alloy, a method for producing the same, and an electronic device.

Internal parts such as a mechanical drive unit and a power supply are arranged inside the housing of an electronic device such as a notebook computer. Since it is necessary to protect internal parts of such electronic devices from impacts and pressures received from the outside, mechanical strength is required for the housing. For such a housing, a stamped product or a machined product of iron or aluminum alloy has been widely used as a metal housing.

With the diversification of uses and places of use of electronic devices, it has come to be assumed that electronic devices are carried. In addition to mechanical strength, lightness is also required for the housing of such electronic devices. In order to meet this demand, lightweight and highly rigid magnesium alloys that have been pressed have come to be used.

As a magnesium alloy for press working, an AZ31B alloy in which 3% of aluminum and 1% of zinc are added to magnesium is on the market. Further, a magnesium alloy containing lithium has been proposed (see, for example, Patent Document 1).
However, since these materials are very active as compared with iron or aluminum alloys, there is a problem that they are inferior in corrosion resistance. Further, these materials are not suitable for the semi-solid casting method because they are alloys having no solid-state temperature indicating a semi-solid state. The semi-solid casting method has the advantages that rust is less likely to occur during casting and the molten metal is easy to manage, as compared with the mold casting method, which is a general casting method.

In order to solve the problem of inferior corrosion resistance, techniques for improving the corrosion resistance of the surface by forming a film on the alloy surface by metal plating, chemical conversion treatment, zinc diffusion film, etc. have been proposed (for example, Non-Patent Document 1, Patent Documents 2 to 2). 3). However, as the thickness of the coating increases, there is a problem that the alloy itself becomes heavier. In order to solve this problem, a method of forming a thin film in order to reduce the thickness of the film can be considered. However, in the production of a thin film, it is difficult to completely cover the alloy surface due to film formation defects and the like. If the alloy surface is not completely covered, the corrosion resistance will be insufficient. Therefore, a magnesium alloy having good corrosion resistance has been desired. The magnesium alloy used in the above technique is the same as the above technique in that it is not suitable for the semi-solid casting method because it is an alloy that does not have a solid phase line temperature indicating a semi-solid state.

Japanese Unexamined Patent Publication No. 9-41066 Japanese Unexamined Patent Publication No. 10-14039 Japanese Unexamined Patent Publication No. 2000-160320

Aluminum Research Journal No. 9, p121

It is an object of the present invention to provide a magnesium alloy which can be applied not only to a mold casting method but also to a semi-solid casting method and has good corrosion resistance, a method for producing the same, and an electronic device using the magnesium alloy. ..

In one embodiment, the magnesium alloy is
Contains magnesium, lithium, zinc, beryllium,
It has a solid phase temperature and a liquidus temperature,
The difference (LS) between the liquidus temperature (L) and the solidus temperature (S) is 50 ° C. or higher.

Further, in one embodiment, the method for producing a magnesium alloy is
A temperature raising step of raising a mixture of magnesium, lithium, zinc, and beryllium at 750 ° C. ± 20 ° C. to 850 ° C. ± 25 ° C. at a heating rate of 50 ° C. ± 10 ° C./min while stirring by electromagnetic melting.
After the temperature raising step, a temperature lowering step of lowering the temperature of the mixture to 525 ° C. ± 10 ° C. at a temperature lowering rate of 30 ° C. ± 10 ° C./min while electromagnetic induction stirring is performed.
including.

Also, in one embodiment, the electronic device has the disclosed magnesium alloy.

As one aspect, it is possible to provide a magnesium alloy that can be applied not only to a mold casting method but also to a semi-solid casting method and has good corrosion resistance.
Further, as one aspect, it is possible to provide a method for producing a magnesium alloy which is applicable not only to a mold casting method but also to a semi-solid casting method and has good corrosion resistance.
Further, as one aspect, it is possible to provide an electronic device using a magnesium alloy which can be applied not only to a mold casting method but also to a semi-solid casting method and has good corrosion resistance.

FIG. 1 is a perspective view of a notebook personal computer as an example of the disclosed electronic device.

(Magnesium alloy)
The disclosed magnesium alloys contain at least magnesium, lithium, zinc, and beryllium, and optionally other metals such as aluminum, tin, silicon, and calcium.
The magnesium alloy may contain unavoidable impurities.

The present inventors have made diligent studies to provide a magnesium alloy that can be applied not only to a mold casting method but also to a semi-solid casting method and has good corrosion resistance.
Then, the present inventors further add berylium to magnesium, lithium, and zinc to produce a magnesium alloy under agitation and under specific temperature conditions, thereby being excellent in corrosion resistance and also in a semi-solid casting method. We have found that applicable magnesium alloys are obtained.

The magnesium alloy has a solid phase temperature and a liquidus temperature.
The difference (LS) between the liquidus temperature (L) and the solidus temperature (S) is 50 ° C. or higher, and may be, for example, 50 ° C. or higher and 150 ° C. or lower, or 50 ° C. or higher. It may be ℃ or more and 140 ℃ or less, or it may be 50 ℃ or more and 130 ℃ or less.
The liquidus temperature is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the liquidus temperature may be 560 ° C. or higher and 700 ° C. or lower, or 570 ° C. or higher and 650 ° C. or lower. However, the temperature may be 580 ° C or higher and 620 ° C or lower.
The solid phase line temperature is not particularly limited and may be appropriately selected depending on the intended purpose. For example, it may be 490 ° C. or higher and 560 ° C. or lower, or 500 ° C. or higher and 550 ° C. or lower. ..

The liquidus temperature and the solidus temperature can be obtained by performing TG-DTA (differential thermal / thermogravimetric measurement). Specifically, it is measured by the following method.
TG-DTA analysis is performed under the condition of a heating rate of 20 ° C./min from room temperature to 650 ° C. in an Ar gas environment.
Since the heat absorption peak at a temperature lower than the liquidus temperature indicating the molten state of the magnesium alloy indicates that it is in a semi-solid state, the temperature indicating the minimum value at the heat absorption peak is the solid phase line temperature.
The appearance of the solid phase line temperature is considered to depend on the conditions for producing the magnesium alloy, and it is preferable to produce the magnesium alloy by the method for producing the magnesium alloy described later.

The disclosed magnesium alloy is applicable to the semi-solid casting method because the difference (LS) between the liquidus temperature (L) and the solidus temperature (S) is 50 ° C. or higher. Is.

<< Semi-solid casting method >>
The semi-solid casting method is one of the casting techniques.
The semi-solid manufacturing method, also called a thixomolding method, is a method of injection molding a metal or alloy in a semi-molten state (thixotropy), and has the following advantages, for example.
-Since metal or alloy chips are used as raw materials, a melting furnace and molten metal are not required.
-Since the injection speed is high, the surface quality is improved.
・ Precision molding of thin-walled products is possible.
-Since the melting temperature is lower than that of the mold casting method, dimensional accuracy and mechanical properties are improved.
-Since the heated raw material does not come into contact with the atmosphere, oxidation (rust) does not occur during processing.
The metal / alloy used in such a semi-solid casting method is required to have a sufficiently large temperature range between the solid phase line and the liquid phase line. This is because the temperature range from the temperature at which the alloy begins to melt to the temperature at which the alloy completely melts [that is, the solid-liquid co-existence region] is sufficiently large, and it is easy to control the casting temperature. To do. In this way, cast pieces with complex shapes and excellent mechanical properties can be produced.
The temperature range between the solid phase line and the liquid phase line applicable to the semi-solid casting method is empirically 50 ° C. or higher. When the temperature is 50 ° C. or higher, the temperature range between the solid phase line and the liquid phase line is sufficiently large, and the temperature range can be used for the semi-solid casting method.

<Magnesium>
The magnesium is the main component of the magnesium alloy.
The content of the magnesium in the magnesium alloy is not particularly limited and may be appropriately selected depending on the intended purpose. For example, it may be 80% by mass or more or 85% by mass or more. ..

<Lithium>
The lithium contributes to weight reduction of the magnesium alloy.
The content of lithium in the magnesium alloy is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 6% by mass or more and 16% by mass or less, and 7% by mass or more and 11% by mass or less. It is preferable, and it is particularly preferable that it is 8% by mass or more and 10% by mass or less. When the content is 16% by mass or less, the weight can be reduced without deteriorating the corrosion resistance.

<Zinc>
The zinc contributes to improving the strength of the magnesium alloy.
The zinc content in the magnesium alloy is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.1% by mass or more and 4% by mass or less, and 0.2% by mass or more and 2% by mass. % Or less is more preferable, and 0.5% by mass or more and 1.5% by mass or less is particularly preferable. When the content is 4% by mass or less, the strength can be improved without causing embrittlement.

<Beryllium>
Magnesium alloys containing magnesium, lithium, and zinc (eg, LZ91 alloys) usually have no solid phase line, or even if they have a solid phase line, the temperature between the liquid phase line. The range is small.
The present inventors have found that appropriate addition of beryllium to a magnesium alloy produces a solid phase line having a large temperature difference from the liquid phase line.

Further, the magnesium alloy containing lithium has a problem that the bare corrosion resistance of the magnesium alloy is low due to its high oxidizing property.
The present inventors have found that the bare corrosion resistance of a magnesium alloy can be improved by appropriately adding beryllium to the magnesium alloy.

The content of beryllium in the magnesium alloy is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.01% by mass or more and 2% by mass or less, and 0.02% by mass or more. More preferably, it is 5% by mass or less. It is even more preferably 0.02% by mass or more and 1% by mass or less, and particularly preferably 0.03% by mass or more and 0.5% by mass or less. The content of beryllium is preferably in the above range from the viewpoint of sufficiently obtaining the effect of adding the beryllium and preventing the magnesium alloy from becoming hard and brittle.

<Other metals>
Examples of the other metal include aluminum, tin, silicon, calcium and the like. These may be used alone or in combination of two or more.

<< Aluminum >>
The aluminum contributes to improving the strength of the magnesium alloy.
The content of the aluminum in the magnesium alloy is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.1% by mass or more and 10% by mass or less, and 1% by mass or more and 8% by mass or less. Is more preferable, and 2% by mass or more and 7% by mass or less is particularly preferable. Even if the content exceeds 10% by mass, the effect of improving the strength does not change.

<< Tin >>
The tin contributes to improving the strength of the magnesium alloy.
The content of the tin in the magnesium alloy is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.1% by mass or more and 5% by mass or less, and 0.5% by mass or more and 4% by mass. % Or less is more preferable, and 1% by mass or more and 3% by mass or less is particularly preferable. Even if the content exceeds 5% by mass, the effect of improving the strength does not change.

<< Silicon >>
The silicon contributes to improving the strength of the magnesium alloy.
The content of the silicon in the magnesium alloy is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.1% by mass or more and 5% by mass or less, and 0.2% by mass or more and 3% by mass. % Or less is more preferable, and 0.5% by mass or more and 2% by mass or less is particularly preferable. Even if the content exceeds 5% by mass, the effect of improving the strength does not change.

<< Calcium >>
The calcium contributes to the improvement of the strength of the magnesium alloy and also to the prevention of combustion in the semi-solid manufacturing method.
The content of the calcium in the magnesium alloy is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.1% by mass or more and 5% by mass or less, and 0.5% by mass or more and 4% by mass. % Or less is more preferable, and 1% by mass or more and 3% by mass or less is particularly preferable. Even if the content exceeds 5% by mass, the effect of improving the strength does not change.

(Manufacturing method of magnesium alloy)
The disclosed method for producing a magnesium alloy includes at least a temperature raising step and a temperature lowering step, and further includes other steps such as a holding step and a mixture preparation step, if necessary.
The method for producing the magnesium alloy is a preferred method for producing the disclosed magnesium alloy.

In a magnesium alloy containing magnesium, lithium, zinc, and beryllium, the present inventors set the difference (LS) between the liquidus line temperature (L) and the solid phase line temperature (S) to be 50 ° C. or higher. Therefore, various conditions for producing the magnesium alloy were examined.
Therefore, when the magnesium alloy is produced under specific temperature rising conditions and specific temperature lowering conditions while performing electromagnetic induction stirring, the liquidus phase line temperature (L) and the solid phase line temperature (S) in the obtained magnesium alloy are obtained. ) And the difference (LS) can be 50 ° C. or higher.
This is because the presence of beryllium is important for the development of the solid phase line temperature in the magnesium alloy, and the beryllium is uniformly dispersed in the magnesium alloy to obtain the liquidus temperature (L) and the solid phase line. It is considered that this is because the difference (LS) from the temperature (S) can be increased. In order to uniformly disperse beryllium in the magnesium alloy, stirring and temperature control during alloy production are important.

The electromagnetic induction stirring is a method of stirring a melt by using stirring energy generated by an electromagnetic force, and is generally used for stirring a high-temperature melt such as a metal melt. The electromagnetic induction stirring is also referred to as electromagnetic stirring.
The electromagnetic induction stirring can be performed by using, for example, an electromagnetic induction stirring device.
As a method of the electromagnetic induction stirring by the electromagnetic induction stirring device, for example, an induction method using a moving magnetic field, a rotating magnetic field, or the like is general. By forming a moving magnetic field, a rotating magnetic field, or the like to move the melt, the melt is agitated.

The stirring conditions for the electromagnetic induction stirring in the disclosed method for producing a magnesium alloy are not particularly limited and may be appropriately selected depending on the intended purpose.

<heating process>
In the temperature raising step, a mixture of magnesium, lithium, zinc, and beryllium at 750 ° C. ± 20 ° C. is heated to 850 ° C. ± 25 ° C. at a heating rate of 50 ° C. ± 10 ° C./min while stirring by electromagnetic melting. It is a process.
The stirring conditions for the electromagnetic induction stirring in the temperature raising step are not particularly limited and may be appropriately selected depending on the intended purpose.

The mixture can be prepared, for example, by using the mixture preparation step described later.
The content of the magnesium in the mixture is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the content of magnesium in the magnesium alloy exemplified in the above description of the magnesium alloy may be used. Can be mentioned.
The content of the lithium in the mixture is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the content of the lithium in the magnesium alloy exemplified in the above description of the magnesium alloy may be used. Can be mentioned.
The zinc content in the mixture is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the zinc content in the magnesium alloy exemplified in the above description of the magnesium alloy may be used. Can be mentioned.
The content of beryllium in the mixture is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the content of beryllium in the magnesium alloy exemplified in the above description of the magnesium alloy may be used. Can be mentioned.

In the disclosed method for producing a magnesium alloy, the difference (LS) between the liquidus line temperature (L) and the solid phase line temperature (S) is 50 unless the temperature is raised under the conditions of the temperature raising step. It is not possible to obtain the magnesium alloy having a temperature of ° C or higher. For example, if the temperature after the temperature rise exceeds 875 ° C., the mixture may ignite.

<Temperature lowering process>
The temperature lowering step is a step of lowering the temperature of the mixture to 525 ° C. ± 10 ° C. at a temperature lowering rate of 30 ° C. ± 10 ° C./min while electromagnetically induced stirring after the temperature raising step.
The stirring conditions for the electromagnetic induction stirring in the temperature lowering step are not particularly limited and may be appropriately selected depending on the intended purpose.

In the disclosed method for producing a magnesium alloy, the difference (LS) between the liquidus temperature (L) and the solidus temperature (S) is 50 ° C. or more unless the temperature is lowered under the conditions of the temperature lowering step. The magnesium alloy is not available.

The mixture cooled to 525 ° C ± 10 ° C is subjected to, for example, a casting step described later and molded into a desired shape.

<Holding process>
The holding step is a step of holding the mixture at 850 ° C. ± 25 ° C. for 5 to 15 minutes while electromagnetically induced stirring between the temperature raising step and the temperature lowering step. By providing the holding step, the compatibility of magnesium, lithium, zinc, and beryllium in the mixture can be made more reliable.
The stirring conditions for the electromagnetic induction stirring in the holding step are not particularly limited and may be appropriately selected depending on the intended purpose.

<Mixture preparation process>
The mixing step is a step of adding beryllium to a solution obtained by dissolving the magnesium, lithium, and zinc at 750 ° C. ± 20 ° C. to obtain the mixture.
When beryllium is added to a solution obtained by mixing and melting magnesium, lithium, and zinc, beryllium is easily dissolved in the obtained mixture. In that respect, the mixture is preferably obtained in the mixture preparation step.

<Other processes>
Examples of the other steps include a casting step and the like.

<< Casting process >>
The obtained magnesium alloy, which is the mixture, is molded into a desired shape through, for example, a casting step.
The casting step is not particularly limited as long as it is a step of casting the magnesium alloy, and can be appropriately selected depending on the intended purpose. For example, a gravity casting method, a mold casting method, a semi-solid casting method and the like can be used. Can be mentioned.
The gravity casting method is a method of casting the magnesium alloy by pouring it into a mold using gravity. The gravity casting method is also called gravity.
The mold casting method is a method of casting by pouring the magnesium alloy into a mold using pressure. The mold casting method is also called die casting.
The semi-solid casting method is as described above.

(Electronics)
The electronic device has the disclosed magnesium alloy. The electronic device is not particularly limited and may be appropriately selected according to the purpose. Examples thereof include personal computers (notebook personal computers, desktop personal computers), telephones, mobile phones, copiers, facsimiles, various printers, digital cameras, televisions, videos, CD devices, DVD devices, air conditioners, remote control devices and the like. Among these, notebook personal computers and mobile phones (including smartphones) are particularly preferable in terms of being carried and used.

In the electronic device, the magnesium alloy is, for example, a housing of the electronic device.

Here, FIG. 1 shows a notebook personal computer as an example of the disclosed electronic device.
The notebook personal computer 20 of FIG. 1 includes a notebook personal computer main body 21 and a liquid crystal display panel unit 22 that is rotated and opened. The notebook personal computer main body 21 has a keyboard unit 23 and a pointing device 24 as input means on the upper surface of the flat housing 25. Inside the housing 25, a hard disk device, a printed circuit board on which a CPU, a memory, and the like are mounted, a battery, and the like are housed.
For example, the magnesium alloy is used for the housing 25.

(Example 1)
As the magnesium alloy, an MLZ-containing magnesium alloy (LZ91) containing magnesium (90 parts by mass), lithium (9 parts by mass), and zinc (1 part by mass) was used. After melting the magnesium alloy (100 parts by mass) at 750 ° C., electromagnetic induction stirring was performed. Beryllium (1 part by mass) was added thereto, and the temperature was raised to 850 ° C. at a heating rate of 50 ° C./min while continuing electromagnetic induction stirring. Then, while continuing electromagnetic induction stirring, the mixture was cooled to 525 ° C. at a cooling temperature of 30 ° C./min. Then, the material cast by gravity using a mold of 250 mm × 30 mm × 45 mm was naturally cooled to room temperature to obtain the magnesium alloy of Example 1.

<Evaluation of corrosion resistance>
The corrosion resistance of the obtained magnesium alloy was tested by a salt spray test by the following method.
The obtained magnesium alloy was cut out to a width of 10 mm, and the surface was polished with No. 400 abrasive paper until the unevenness disappeared to obtain a salt spray test piece (sample).
The obtained sample was subjected to a salt spray test by a method according to JIS Z 2371-2001. The spraying conditions are shown below.

<< Spraying conditions >>
Spray room temperature: 35 ± 2 ° C
Air saturation: 47 ± 2 ° C
Spray amount: 1.5 ± 0.5 ml / 80 cm ² / h
Salt water concentration: 5 ± 1%
NaCl purity: 99.5% or more pH value: 6.5-7.2
Spray exposure time: 240h
After spraying with salt water under the above conditions, the sample was washed with pure water, dried, and then the weight change from the initial stage was measured to calculate the weight change rate.

<< Evaluation Criteria >>
The following points were given according to the rate of change in weight after the salt spray test. In addition, the evaluation 3 or more was passed (magnesium alloy which can withstand practical use).
・ Weight change rate: No change 5
・ Weight change rate: 2.5% or less 4
・ Weight change rate: 5% or less 3
・ Weight change rate: 10% or less 2
・ Weight change rate: Over 10% 1
The rate of change in weight after subjecting the sample of Example 1 to the salt spray test was 4.

<TG-DTA analysis>
TG-DTA (differential thermal / thermogravimetric measurement) was performed to determine the solid phase temperature and the liquidus temperature of the magnesium alloy. Specifically, the measurement was performed by the following method.
TG-DTA analysis was performed under the condition of a heating rate of 20 ° C./min from room temperature to 650 ° C. in an Ar gas environment.
Since the heat absorption peak at a temperature lower than the liquidus temperature indicating the molten state of the magnesium alloy indicates that it is in a semi-solid state, the temperature indicating the minimum value at the heat absorption peak is the solid phase line temperature.
As a result of the measurement, the solidus line temperature was 500 ° C. and the liquidus line temperature was 620 ° C.

(Example 2)
A magnesium alloy of Example 2 was obtained in the same manner as in Example 1 except that beryllium was changed to 0.03 parts by mass in Example 1.
The obtained magnesium alloy of Example 2 was subjected to a salt spray test in the same manner as in Example 1. The rate of change in weight after the sample was subjected to the salt spray test was 4.
For the obtained magnesium alloy of Example 2, TG-DTA measurement was performed in the same manner as in Example 1. As a result of the measurement, the solidus temperature was 522 ° C and the liquidus temperature was 596 ° C.

(Example 3)
A magnesium alloy of Example 3 was obtained in the same manner as in Example 1 except that the casting method was changed to the mold casting method in Example 1.
The obtained magnesium alloy of Example 3 was subjected to a salt spray test in the same manner as in Example 1. The rate of change in weight after the sample was subjected to the salt spray test was 4.
For the obtained magnesium alloy of Example 3, TG-DTA measurement was carried out in the same manner as in Example 1. As a result of the measurement, the solidus line temperature was 500 ° C. and the liquidus line temperature was 620 ° C.

(Example 4)
The magnesium alloy of Example 4 was obtained in the same manner as in Example 1 except that the casting method was changed to the semi-solid casting method in Example 1.
The obtained magnesium alloy of Example 4 was subjected to a salt spray test in the same manner as in Example 1. The rate of change in weight after the sample was subjected to the salt spray test was 4.
For the obtained magnesium alloy of Example 4, TG-DTA measurement was performed in the same manner as in Example 1. As a result of the measurement, the solidus line temperature was 500 ° C. and the liquidus line temperature was 620 ° C.

(Example 5)
In Example 1, a magnesium alloy of Example 5 was obtained in the same manner as in Example 1 except that 1 part by mass of beryllium was changed to 5 parts by mass of aluminum and 0.5 part by mass of beryllium.
The obtained magnesium alloy of Example 5 was subjected to a salt spray test in the same manner as in Example 1. The rate of change in weight after the sample was subjected to the salt spray test was 3.
For the obtained magnesium alloy of Example 5, TG-DTA measurement was carried out in the same manner as in Example 1. As a result of the measurement, the solidus temperature was 532 ° C and the liquidus temperature was 596 ° C.

(Example 6)
In Example 1, a magnesium alloy of Example 6 was obtained in the same manner as in Example 1 except that 1 part by mass of beryllium was changed to 2 parts by mass of tin and 0.5 part by mass of beryllium.
The obtained magnesium alloy of Example 6 was subjected to a salt spray test in the same manner as in Example 1. The rate of change in weight after the sample was subjected to the salt spray test was 4.
For the obtained magnesium alloy of Example 6, TG-DTA measurement was carried out in the same manner as in Example 1. As a result of the measurement, the solidus temperature was 511 ° C and the liquidus temperature was 586 ° C.

(Example 7)
In Example 1, a magnesium alloy of Example 7 was obtained in the same manner as in Example 1 except that 1 part by mass of beryllium was changed to 1 part by mass of silicon and 0.5 part by mass of beryllium.
The obtained magnesium alloy of Example 7 was subjected to a salt spray test in the same manner as in Example 1. The rate of change in weight after the sample was subjected to the salt spray test was 4.
For the obtained magnesium alloy of Example 7, TG-DTA measurement was performed in the same manner as in Example 1. As a result of the measurement, the solidus temperature was 531 ° C and the liquidus temperature was 598 ° C.

(Example 8)
In Example 1, a magnesium alloy of Example 8 was obtained in the same manner as in Example 1 except that 1 part by mass of beryllium was changed to 2 parts by mass of calcium and 0.5 part by mass of beryllium.
The obtained magnesium alloy of Example 8 was subjected to a salt spray test in the same manner as in Example 1. The rate of change in weight after the sample was subjected to the salt spray test was 4.
For the obtained magnesium alloy of Example 8, TG-DTA measurement was performed in the same manner as in Example 1. As a result of the measurement, the solidus temperature was 537 ° C and the liquidus temperature was 590 ° C.

(Comparative Example 1)
A magnesium alloy of Comparative Example 1 was obtained in the same manner as in Example 1 except that beryllium was not added in Example 1.
The obtained magnesium alloy of Comparative Example 1 was subjected to a salt spray test in the same manner as in Example 1. The rate of change in weight after the sample was subjected to the salt spray test was 1.
The obtained magnesium alloy of Comparative Example 1 was subjected to TG-DTA measurement in the same manner as in Example 1. As a result of the measurement, the solidus line temperature did not appear, and the liquidus line temperature was 598 ° C.

(Comparative Example 2)
In Example 1, a magnesium alloy of Comparative Example 2 was obtained in the same manner as in Example 1 except that the material was melted at 750 ° C. and then cooled by natural cooling without electromagnetic induction stirring. In the above natural cooling, the cooling rate from 750 ° C to 580 ° C was about 5 ° C / min.
The obtained magnesium alloy of Comparative Example 2 was subjected to a salt spray test in the same manner as in Example 1. The rate of change in weight after the sample was subjected to the salt spray test was 2.
For the obtained magnesium alloy of Comparative Example 2, TG-DTA measurement was carried out in the same manner as in Example 1. As a result of the measurement, the solidus temperature was 590 ° C and the liquidus temperature was 635 ° C.

The above results are summarized in Table 1.

Further, the following additional notes will be disclosed.
(Appendix 1)
Contains magnesium, lithium, zinc, beryllium,
It has a solid phase temperature and a liquidus temperature,
A magnesium alloy characterized in that the difference (LS) between the liquidus temperature (L) and the solidus temperature (S) is 50 ° C. or higher.
(Appendix 2)
The magnesium alloy according to Appendix 1, wherein the difference (LS) is 50 ° C. or higher and 150 ° C. or lower.
(Appendix 3)
The magnesium alloy according to any one of Supplementary note 1 to 2, wherein the liquidus temperature (L) is 560 ° C. or higher and 700 ° C. or lower.
(Appendix 4)
The magnesium alloy according to any one of Supplementary note 1 to 3, wherein the magnesium content is 80% by mass or more.
(Appendix 5)
The magnesium alloy according to any one of Supplementary note 1 to 4, wherein the content of beryllium is 0.01% by mass or more and 2% by mass or less.
(Appendix 6)
The magnesium alloy according to any one of Supplementary note 1 to 5, wherein the lithium content is 6% by mass or more and 16% by mass or less.
(Appendix 7)
The magnesium alloy according to any one of Supplementary note 1 to 6, wherein the zinc content is 0.1% by mass or more and 4% by mass or less.
(Appendix 8)
The magnesium alloy according to any one of Supplementary note 1 to 7, further comprising at least one of aluminum, tin, silicon, and calcium.
(Appendix 9)
A temperature raising step of raising a mixture of magnesium, lithium, zinc, and beryllium at 750 ° C. ± 20 ° C. to 850 ° C. ± 25 ° C. at a heating rate of 50 ° C. ± 10 ° C./min while stirring by electromagnetic melting.
After the temperature raising step, a temperature lowering step of lowering the temperature of the mixture to 525 ° C. ± 10 ° C. at a temperature lowering rate of 30 ° C. ± 10 ° C./min while electromagnetic induction stirring is performed.
A method for producing a magnesium alloy, which comprises.
(Appendix 10)
The method for producing a magnesium alloy according to Appendix 9, wherein the magnesium alloy according to any one of Supplements 1 to 8 is obtained.
(Appendix 11)
2. Production method.
(Appendix 12)
The magnesium alloy according to any one of Supplementary note 9 to 11 obtained by adding beryllium to the mixture obtained by dissolving the magnesium, the lithium, and the zinc at 750 ° C. ± 20 ° C. Production method.
(Appendix 13)
An electronic device comprising the magnesium alloy according to any one of Supplementary Notes 1 to 8.

20 Notebook PC 21 Notebook PC body 22 Liquid crystal display panel part 23 Keyboard part 24 Pointing device 25 Housing

Claims (7)

A temperature raising step of raising a mixture of magnesium, lithium, zinc, and beryllium at 750 ° C. ± 20 ° C. to 850 ° C. ± 25 ° C. at a heating rate of 50 ° C. ± 10 ° C./min while stirring by electromagnetic melting.
After the temperature raising step, a temperature lowering step of lowering the temperature of the mixture to 525 ° C. ± 10 ° C. at a temperature lowering rate of 30 ° C. ± 10 ° C./min while electromagnetic induction stirring is performed.
Including
The magnesium content in the mixture is 80% by mass or more, the lithium content is 6% by mass or more and 16% by mass or less, and the zinc content is 0.1% by mass or more and 4% by mass. % Or less, and the content of the beryllium is 0.01% by mass or more and 2% by mass or less.
A method for producing a magnesium alloy, which comprises obtaining a magnesium alloy in which the difference (LS) between the liquidus temperature (L) and the solid phase temperature (S) is 50 ° C. or higher. The method for producing a magnesium alloy according to claim 1, wherein the content of beryllium is 0.02% by mass or more and 1.5% by mass or less. The method for producing a magnesium alloy according to any one of claims 1 to 2, wherein the lithium content is 7% by mass or more and 11% by mass or less. The method for producing a magnesium alloy according to any one of claims 1 to 3, wherein the zinc content is 0.2% by mass or more and 2% by mass or less. The mixture further contains at least one of aluminum, tin, silicon, and calcium.
The content of the aluminum in the mixture is 0.1% by mass or more and 10% by mass or less, the content of the tin is 0.1% by mass or more and 5% by mass or less, and the content of the silicon is. The method for producing a magnesium alloy according to any one of claims 1 to 4 , wherein the content of calcium is 0.1% by mass or more and 5% by mass or less, and the calcium content is 0.1% by mass or more and 5% by mass or less . The magnesium alloy according to any one of claims 1 to 5, which comprises a holding step of holding the magnesium alloy at 850 ° C. ± 25 ° C. for 5 to 15 minutes with electromagnetic induction stirring between the temperature raising step and the temperature lowering step. Manufacturing method. The magnesium alloy according to any one of claims 1 to 6, wherein the mixture is obtained by adding beryllium to a solution obtained by dissolving the magnesium, the lithium, and the zinc at 750 ° C. ± 20 ° C. Manufacturing method.

Images