JP7550052B2 - Magnesium alloy sheet material and its manufacturing method - Google Patents

Description

An embodiment of the present invention relates to a magnesium alloy sheet material and a manufacturing method thereof.

Recently, there has been growing interest in lightweight structural materials, and active research is being conducted into these materials. As a result, there has been growing interest in magnesium sheet material, which has excellent specific strength (strength relative to density).

Magnesium has a density of 1.74 g/ ^cm2 and is the lightest of all structural metals, including aluminum and steel. Magnesium is a metal that has been gaining attention in the IT/Mobile field due to its excellent vibration absorption and electromagnetic wave shielding properties.

In the automotive field, developed countries, particularly Europe, are actively conducting research into reducing vehicle weight due to fuel efficiency regulations and performance improvements. For this reason, magnesium is being considered as one of the alternative metals.

However, magnesium sheet material has an HCP structure, and the deformation mechanism at room temperature is limited, making it impossible to form at room temperature. This places some limitations on its application to the automotive industry. Various research efforts have been made to overcome this issue.

For example, there are differential speed rolling, where the upper and lower rolls are at different speeds, the ECAP process, and high-temperature rolling, where the material is rolled at temperatures close to the eutectic temperature of magnesium sheet metal. However, all of these processes are still far from being commercialized.

As another example, there is an improvement method using alloys, as in the previous patent (Korean Patent Publication No. 2012-0055304). Specifically, magnesium plate material containing 1-10% by weight of Zn and 0.1-5% by weight of Ca can be used. However, the plate material cannot be applied to the strip casting method. As a result, mass production is lacking, and there are problems with long-term casting due to the fusion phenomenon between the casting material and the roll during long-term casting.

Meanwhile, the previous patent (Korean Patent Application No. 2015-0185017) improved the process of the conventional alloy of 3% Al, 1% Zn, and 1% Ca by weight, and was able to obtain a high forming limit with a dome height of 7 mm or more. However, this technology requires intermediate annealing at least once during the rolling stage and warm forming. This results in high process costs and large investment costs for dies/heating equipment, etc. This results in reduced productivity and high processing costs for magnesium alloys compared to competing materials.

In addition, in the case of the highly formable E-form alloy (AZX311) sheet material currently developed by our company, anisotropy exists when parts are formed. Therefore, we aim to provide a magnesium alloy sheet material that solves the above-mentioned problems.

We provide a magnesium alloy sheet material that has excellent room temperature formability and does not have large anisotropy in its physical properties, and a method for manufacturing the same.

Specifically, the fraction of secondary phases generated can be reduced by reducing the aluminum content. This increases the grain boundary segregation effect, improving room temperature formability.

In addition, secondary phase stringers can also be reduced as the proportion of secondary phases is reduced. Therefore, we aim to provide a magnesium alloy sheet material in which the physical properties do not differ significantly between when the sheet material is stretched in the transverse direction (TD) and when it is stretched in the rolling direction (RD).

The magnesium alloy sheet material, which is one embodiment of the present invention, may contain, relative to 100% by weight, 0.5-1.5% by weight of Al, 0.1-0.7% by weight of Zn, 0.1-0.5% by weight of Ca, 0.01-0.3% by weight of Mn, with the balance being Mg and other unavoidable impurities.

The Al content may be 0.5 to 1.3 wt% relative to 100 wt% of the magnesium alloy sheet material.

The magnesium alloy sheet material may include a secondary phase, and the area fraction of the secondary phase may be 5% or less relative to 100% of the total area of the magnesium alloy sheet material.

The secondary phase may be Al ₂ Ca, Al ₈ Mn ₅ , or a combination thereof.

The magnesium alloy plate material may include a stringer, the length of which may be up to 50 μm or less.

The limit bending radius (LBR) value in the rolling direction (RD) of the magnesium alloy sheet material at 150°C or higher may be 0 to 0.5 R/t.

The limit bending radius (LBR) value of the magnesium alloy sheet in the sheet width direction (TD) at 150°C or higher may be 0 to 0.5 R/t.

The ratio of the limit bending radius (LBR) value in the sheet width direction (TD) to the rolling direction (RD) of the magnesium alloy sheet at 150°C or higher may be 0.8 to 1.2.

The limit dome height (LDH) of the magnesium alloy sheet material may be 8 mm or more.

A method for producing a magnesium alloy sheet material according to another embodiment of the present invention may include the steps of preparing a molten alloy containing, relative to 100% by weight, 0.5-1.5% by weight of Al, 0.5-1.5% by weight of Zn, 0.1-1.0% by weight of Ca, 0.01-1.0% by weight of Mn, the balance being Mg and other unavoidable impurities, casting the molten alloy to prepare a cast material, rolling the cast material to prepare a rolled material, and final annealing the rolled material.

In the step of preparing the molten alloy, the content of Al may be 0.5 to 1.3 wt % relative to 100 wt % of the entire molten alloy.

The step of casting the molten metal to prepare the casting material may be performed by a strip casting method.

The step of rolling the cast material to prepare the rolled material may involve rolling at a reduction rate of 50% or less (excluding 0%) per rolling pass.

Specifically, the cast material may be rolled once or twice or more.

More specifically, rolling can be performed at a temperature range of 100 to 350°C.

The step of rolling the cast material to prepare a rolled material may further include a step of intermediate annealing the rolled material.

The step of intermediate annealing the rolled material may be carried out at a temperature in the range of 300 to 500°C.
Specifically, it may be carried out for 30 minutes to 6 hours.

The final annealing of the rolled material may be carried out at 250°C or higher. Specifically, it may be carried out for 30 to 600 minutes.

According to one embodiment of the present invention, the fraction of secondary phases and secondary phase stringers can be controlled according to the aluminum content, and a magnesium alloy sheet material can be produced that does not have large anisotropy during bending tests in the rolling direction (RD) and sheet width direction (TD).

In addition, it is possible to simultaneously provide magnesium alloy sheet material with excellent formability at room temperature.

1A to 1C are diagrams sequentially illustrating a mechanism of crack formation by a secondary phase stringer during a tensile test in the transverse direction (TD) of a plate material. FIG. 2 is a view of a cross section of Example 1 observed by SEM. FIG. 2 is a view of a cross section of Comparative Example 1 observed by SEM. FIG. 1 is a SEM observation of a cross section in which a crack was generated during a bending test in Comparative Example 1. FIG. 1 is a cross-sectional view of Example 2 observed under an optical microscope.

The advantages and features of the present invention, as well as the methods for achieving them, will become apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be realized in various different forms. The embodiments are provided merely to complete the disclosure of the present invention and to fully inform those skilled in the art of the present invention of the scope of the invention, and the present invention is defined solely by the claims. The same reference characters refer to the same elements throughout the specification.

Therefore, in some embodiments, well-known techniques are not specifically described to avoid ambiguous interpretation of the present invention. Unless otherwise defined, all terms (including technical and scientific terms) used in this specification are used with the meaning commonly understood by those having ordinary skill in the art to which the present invention belongs. When a part "comprises" a certain component throughout the specification, this does not mean excluding other components, but may further include other components, unless otherwise specified to the contrary. In addition, the singular form includes the plural form unless otherwise specified in the text.

A magnesium alloy sheet material according to one embodiment of the present invention may contain, relative to 100% by weight, 0.5 to 1.5% by weight of Al, 0.1 to 1.5 % by weight of Zn, 0.1 to 1.0 % by weight of Ca, 0.01 to 0.3% by weight of Mn, with the balance being Mg and other inevitable impurities.

Specifically, the Al content may be 0.5 to 1.3 wt% relative to 100 wt% of the magnesium alloy sheet material.

The reasons for limiting the components and composition of the magnesium alloy sheet material are explained below.

Al may be contained in an amount of 0.5 to 1.5% by weight. More specifically, it may be contained in an amount of 0.5 to 1.3% by weight. More specifically, aluminum improves formability at room temperature, so when it contains this amount, it can be cast by strip casting.

Specifically, in the rolling step of the method for manufacturing a magnesium alloy sheet material described later, the rolling texture changes to a strong basal plane texture. At this time, there is a solute dragging effect as a mechanism for suppressing the change to the basal plane texture. The solute dragging mechanism can reduce grain boundary mobility when heat or deformation is applied by segregating elements such as Ca, which has a larger atomic radius than Mg, within the crystal grain boundaries. This can suppress the formation of a basal plane texture due to dynamic recrystallization during rolling or rolling deformation.

Therefore, when aluminum is added in an amount exceeding 1.5 wt%, the amount of Al ₂ Ca secondary phase also increases rapidly, so the amount of Ca segregated at the grain boundaries may decrease. Therefore, the solute traction effect may also decrease. In addition, the fraction of the secondary phase decreases, so that stringers may also be reduced. The stringers will be described in detail below.

On the other hand, if aluminum is added at less than 0.5 wt%, it may be impossible to cast using the strip casting method. Aluminum improves the fluidity of the molten metal, preventing roll sticking during casting. Therefore, Mg-Zn magnesium alloys without aluminum added cannot be cast using the strip casting method due to the actual roll sticking phenomenon.

Zn may be present in amounts of 0.1 to 1.5 % by weight.

More specifically, when zinc is added together with calcium, it improves the formability of sheet materials by activating basal slip due to the softening phenomenon of the non-basal plane. However, when added in an amount exceeding 1.5 wt%, it combines with magnesium to form an intermetallic compound, which may adversely affect formability.

Ca may be contained in an amount of 0.1 to 1.0 wt %.

When added together with zinc, calcium brings about a softening phenomenon of the non-basal surfaces and improves the formability of the sheet material by activating non-basal slip.

More specifically, in the manufacturing method of magnesium alloy sheet material described later, the texture has a characteristic of changing into a strong basal plane texture during rolling. The solute dragging effect is a mechanism for suppressing this characteristic. More specifically, elements with a larger atomic radius than Mg segregate within the grain boundaries, which can reduce boundary mobility when heat or deformation is applied. In this case, Ca can be used as the element with a larger atomic radius than Mg. In this case, it is possible to suppress the formation of basal plane texture due to dynamic recrystallization during rolling or rolling deformation.

However, when the amount of added exceeds 1.0 wt %, adhesion to the casting roll increases during strip casting, causing severe sticking, which reduces the fluidity of the molten metal and reduces castability, which can reduce productivity.

Mn may be present in amounts of 0.01-0.3 wt%.

Manganese forms Fe-Mn compounds and serves to reduce the content of Fe in the sheet material. Therefore, when manganese is contained, Fe-Mn compounds can be formed in the form of dross or sludge in the molten alloy state before casting. Therefore, a sheet material with a low content of Fe can be manufactured during casting. Furthermore, manganese can form an Al ₈ Mn ₅ secondary phase with aluminum. This serves to suppress the amount of calcium consumed and increase the amount of calcium that can segregate at the grain boundaries. Therefore, when manganese is added, the solute attraction effect can be further improved.

The magnesium alloy sheet may have calcium element segregated at the grain boundaries. In this case, the calcium element may segregate at the grain boundaries in the form of a solute, not in the form of an intermetallic compound.

More specifically, calcium does not form a secondary phase with elements such as aluminum, but rather dissolves and segregates to the grain boundaries in the form of a solute, thereby reducing the mobility of the grain boundaries and suppressing the formation of basal plane texture. This makes it possible to provide a magnesium alloy sheet material with excellent formability at room temperature.

Therefore, the magnesium alloy sheet may include a secondary phase that is _Al2Ca , _Al8Mn5 , or a combination thereof, and the area fraction of the secondary phase may be ₅ % or less, more specifically, 3% or less, and even more specifically, 1% or less, relative to 100% of the total area of the magnesium alloy sheet.

This is a significantly lower figure than other conventional magnesium alloy sheet materials that contain more than 1.5% by weight of Al relative to the total weight of the magnesium alloy sheet material.

By minimizing the secondary phase fraction within the above range, it is possible to improve grain boundary segregation and improve room temperature formability. In addition, it is possible to reduce secondary phase stringers that occur due to an increase in the secondary phase fraction.

In this specification, stringer means that the secondary phase solidifies and forms a band in the rolling direction (RD).

Specifically, the magnesium alloy plate material includes a stringer, and the length of the stringer may be up to 50 μm or less.

The stringer length range is a maximum of 50 μm or less, which means that there are almost no stringers included.

On the other hand, when the secondary phase solidifies and band-shaped stringers with a maximum length of more than 50 μm are present in the rolling direction (RD), the magnesium alloy sheet has large anisotropy in its physical properties. Specifically, when the magnesium alloy sheet contains stringers with a maximum length of more than 50 μm in the rolling direction, the secondary phase breaks along the stringers formed in the rolling direction (RD) during bending or tension in the sheet width direction (TD), and cracks can easily propagate.

In particular, when such secondary phase stringers are present near the surface of the magnesium alloy sheet, cracks may occur more easily during bending tests in the sheet width direction, which is perpendicular to the rolling direction.

Figure 1 shows the mechanism of crack formation caused by secondary stringers.

Figure 1 shows the mechanism of crack formation caused by secondary stringers during a tensile test in the transverse direction (TD) of a plate.

As shown in Figure 1, it can be seen that the cracks progress along the secondary stringers (white dots) formed in the tensile rolling direction (RD) in the sheet width direction (TD). In other words, it can be deduced that the cracks tend to continue along the secondary stringers because the direction of crack progression is parallel to the secondary stringers.

Therefore, in the case of magnesium alloy sheets containing secondary phase stringers, when the sheet is stretched in the width direction (TD), the anisotropy may be inferior to when the sheet is stretched in the rolling direction (RD). This results in a large difference in physical properties between when the sheet is stretched (bending) in the rolling direction (RD) and when the sheet is stretched (bending) in the width direction (TD).

That is, in this specification, the criterion for secondary phase stringers that have an inferior effect on bending anisotropy is defined as stringers whose maximum length exceeds 50 μm.

In this specification, the sheet width direction (TD) refers to the direction perpendicular to the rolling direction (RD).

In addition, in this specification, anisotropy means that the physical properties are different in the rolling direction (RD) and the sheet width direction (TD). As will be described later, in this specification, anisotropy was measured by performing bending tests in the rolling direction (RD) and the sheet width direction (TD) using a V-bending test. Therefore, the limit bending radius (LBR) value from the bending test is shown as an index of anisotropy.

Therefore, excellent anisotropy means that there is little difference in physical properties between the rolling direction (RD) and the sheet width direction (TD).

Therefore, the limit bending radius (LBR) value of the magnesium alloy sheet material in the rolling direction (RD) at 150°C or higher may be 0 to 0.5 R/t.

Meanwhile, the limit bending radius (LBR) value of the magnesium alloy sheet material in the sheet width direction (TD) at 150°C or higher may be 0 to 0.5R/t.

In this specification, the limit bending radius (LBR) means the ratio of the inner radius of curvature (R) of the sheet material to the thickness (t) of the sheet material after the V-bending test. Specifically, it can be the inner radius of curvature of the sheet material (R) / thickness (t) of the sheet material.

Specifically, the ratio of the limit bending radius (LBR) in the sheet width direction (TD) to the rolling direction (RD) of the magnesium alloy sheet may be 0.8 to 1.2.

The above range means that there is not a large difference in physical properties between the rolling direction (RD) and the sheet width direction (TD).

The limit dome height (LDH) of the magnesium alloy sheet material may be 8 mm or more.

In this specification, the limit dome height (LDH) refers to a value derived by the Erichsen test at room temperature. The formability of the sheet material can be compared from this value.

More specifically, the Erichsen value means the height to which a sheet material is deformed before it breaks when it is deformed into a cup shape. Therefore, the higher the deformation height of a magnesium alloy sheet material, the higher the Erichsen value. This results in excellent formability.

As a result, the limit dome height of the magnesium alloy sheet material according to one embodiment of the present invention can be at a superior level compared to conventional magnesium alloy materials.

A method for producing a magnesium alloy sheet material according to another embodiment of the present invention may include the steps of preparing a molten alloy (S100) containing, relative to a total weight percentage of 100%, 0.5-1.5% Al, 0.5-1.5% Zn, 0.1-1.0% Ca, 0.01-1.0% Mn, the remainder being Mg and other unavoidable impurities, casting the molten alloy to prepare a cast material (S200), rolling the cast material to prepare a rolled material (S300), and final annealing the rolled material (S400).

Specifically, in step S100, Al may be 0.5 to 1.0 wt% relative to the total weight of the molten alloy (100 wt%).

The specific reasons for limiting the components and composition of the molten metal are the same as those for limiting the components and composition of the magnesium alloy plate material previously explained, and therefore will not be repeated here.

Then, in step S200, the casting method for preparing the casting material may be die casting, direct chill casting, billet casting, centrifugal casting, tilt casting, metal mold gravity casting, sand casting, strip casting, or a combination thereof, but is not limited thereto.

More specifically, it can be cast by strip casting. Strip casting may be possible with a molten alloy of the above-mentioned composition.

More specifically, the molten metal can be cast at a speed of 0.5 to 10 mpm.

Therefore, the thickness of the produced casting material may be 3-13 mm, but is not limited to this.

In step S300, rolling may be performed at a reduction rate of 50% or less (excluding 0%) per rolling pass. More specifically, if the reduction rate per rolling pass exceeds 50%, cracks may occur during rolling.

In the following, in this specification, the rolling reduction ratio means the difference between the thickness of the material before passing through the rolling rolls during rolling and the thickness of the material after passing through the rolling rolls, divided by the thickness of the material before passing through the rolling rolls, and then multiplied by 100.

Specifically, the cast material can be rolled once or more than once. More specifically, if the cast material is thick, it can be rolled more than once.

More specifically, rolling can be performed at a temperature range of 100 to 350°C. More specifically, if the rolling temperature is less than 100°C, cracks may be induced during rolling. On the other hand, if the rolling temperature exceeds 350°C, Ca segregation may decrease, which may be disadvantageous.

Furthermore, the step (S300) may further include a step (S310) of intermediate annealing the rolled material.

Specifically, when rolling is performed two or more times, intermediate annealing can be performed between the rolling steps. In this case, the step (S310) can be performed at a temperature range of 300 to 500°C. More specifically, it can be performed for 30 minutes to 6 hours.

More specifically, when intermediate annealing is performed under the above conditions, the stress generated during rolling can be sufficiently relieved. More specifically, the stress can be relieved by recrystallization within a range that does not exceed the melting temperature of the rolled material. Furthermore, recrystallization can also induce the formation of crystal grains with non-basal plane crystal orientation.

Finally, the final annealing step (S400) of the rolled material may be performed at a temperature of 250° C. or more, specifically, at a temperature of 250 to 450° C.
More specifically, it can be carried out for 30 minutes to 600 minutes.

Recrystallization can be easily formed by final annealing under the above conditions.

The present invention will be described in more detail below with reference to examples. However, the following examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples.

Manufacturing Examples Magnesium alloy sheets according to the examples and comparative examples were manufactured using the components and compositions shown in Table 1 below.

Specifically, a molten alloy containing the components and composition disclosed in Table 1 below was prepared. The molten alloy was then cast by strip casting to prepare a cast material. The cast material was then rolled 7 to 10 times at 200°C with a reduction rate of 25% per rolling.

Intermediate annealing was also performed between the rolling steps. Specifically, this was performed at 400°C for 3 hours.

Finally, the rolled plate was given a final annealing at 300°C.

The tensile strength (YS), elongation (El), limit dome height (LDH), and limit bending radius (LBR) of the examples and comparative examples manufactured in this manner were evaluated and are shown in Table 1 below.

At this time, the evaluation methods for each physical property are as follows:

[Method of measuring tensile strength]
It means the value obtained by dividing the maximum tensile load until the test piece breaks by the cross-sectional area of the test piece before the test. Specifically, the measurement was performed at room temperature using a uniaxial tensile tester, and the strain rate was 10 ^-3 /s.

[Method of measuring elongation rate]
It is the ratio of elongation of a material during a tensile test, and refers to the percentage of the length of the test specimen changed relative to the length of the test specimen before the test. Specifically, the condition was the same as that for measuring tensile strength, and the increase in length was measured relative to the initial length of the gauge part.

[Method of measuring the Erichsen number]
A magnesium alloy plate having a width and length of 50 to 60 mm was used, and a lubricant was applied to the surface of the plate to reduce friction between the plate and the spherical punch.

At this time, the die and spherical punch were kept at room temperature during the test.

More specifically, after inserting a magnesium alloy sheet between an upper die and a lower die, the outer periphery of the sheet was fixed with a force of 10 kN, and then a spherical punch with a diameter of 20 mm was used to deform the sheet at a speed of 5 mm/min. The punch was then inserted until the sheet broke, and the deformation height of the sheet at the time of breakage was measured.

The deformation height of the plate measured in this way is called the Erichsen value or limit dome height (LDH).

[Method of measuring limit bending radius (V-bending)]
The result of the V-bending test is called the limit bending radius (LBR).

Specifically, a heating wire is installed in the device consisting of a die and a punch so that the temperature can be controlled to the target temperature. Both the die and punch can have a 90° angle. There are various types of punches with a radius of curvature ranging from 0R to 9R.

After bending the plate material using the above device, the radius of the punch that can bend without cracks is calculated. At this time, the bending speed of the punch was measured at 30 to 60 mm per second.

The equipment used was a mechanical 60 ton servo press, and a V-bending mold containing a punch and die was installed in the press.

As shown in Table 1, Comparative Example 1, which has an aluminum content of 2% by weight, has an excellent limit dome height (LDH) value, but an inferior limit bending radius (LBR) value.

In particular, in Comparative Example 1, the ratio of the limit bending radius (LBR) value in the rolling direction (RD) to the limit bending radius (LBR) value in the sheet width direction (TD) at 200°C is 3.75, indicating that tensile anisotropy is large in both the rolling direction and the sheet width direction.

In addition, it can be seen that Comparative Example 4 had superior anisotropy compared to Comparative Examples 1 to 3, but had an inferior limit bending radius (LBR) value compared to Examples 1 and 2.

This can also be confirmed by the drawings of the present invention.

Figure 2 shows a cross section of Example 1 observed with an SEM.

2, it can be confirmed with the naked eye that there are no secondary phase stringers with a length exceeding 50 μm in Example 1. Therefore, it can be deduced that there is not a large difference in physical properties during tension between the rolling direction (RD) and the sheet width direction (TD) in Example 1.

Figure 3 shows a cross section of Comparative Example 1 observed with an SEM.

On the other hand, as shown in FIG. 3, in Comparative Example 1, it can be seen that the secondary phase solidified on the surface and under the surface of the sheet material, and band-shaped stringers were included in the rolling direction. It was also confirmed that the length of the stringers was at least 100 μm.

This explains why Comparative Example 1 has large anisotropy in the sheet material width direction and rolling direction.

Specifically, Figure 4 shows that cracks were generated during the bending test of Comparative Example 1.

Figure 4 shows a cross section of Comparative Example 1 where a crack was generated during a bending test, as observed by SEM. Specifically, as shown in Figure 4, stringers could be confirmed on the surface and below the surface in Comparative Example 1. As a result, it can be confirmed that cracks easily formed on the surface.

Figure 5 shows a cross section of Example 2 observed with an optical microscope.

As shown in Figure 5, it can be seen that Example 2 also contains secondary phases (black dots). However, it can be confirmed with the naked eye that the proportion of secondary phases is very small compared to the magnesium alloy sheet material.

As a result, the embodiment of the present invention can control the fraction of secondary phases and secondary phase stringers according to the aluminum content, and produce magnesium alloy sheet material that does not have large anisotropy during bending tests in the rolling direction (RD) and sheet width direction (TD).

In addition, it is possible to simultaneously provide magnesium alloy sheet material with excellent formability at room temperature.

Although the embodiments of the present invention have been described above with reference to the attached drawings, a person having ordinary knowledge in the technical field to which the present invention pertains can understand that the present invention can be embodied in other specific forms without changing its technical concept or essential features.

Therefore, it should be understood that the above embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims set forth below rather than the above detailed description, and all modifications and alterations derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims (11)

The magnesium alloy sheet material is composed of 0.5 to 1.5 wt % Al, 0.1 to 1.5 wt % Zn, 0.1 to 1.0 wt % Ca, 0.01 to 0.3 wt % Mn, the balance being Mg and other inevitable impurities, relative to 100 wt % of the entire magnesium alloy sheet material;
The magnesium alloy sheet material includes a secondary phase of an intermetallic compound,
The area fraction of the secondary phase is 5% or less with respect to 100% of the total area of the magnesium alloy plate material;
The magnesium alloy sheet material includes a stringer, and the stringer has a dot shape formed by solidifying the secondary phase and forms a discontinuous band in a rolling direction (RD),
The length of the stringer is up to 50 μm or less.
Magnesium alloy sheet material. The magnesium alloy sheet material according to claim 1, in which the Al content is 0.5 to 1.3 wt % relative to 100 wt % of the entire magnesium alloy sheet material. 3. The magnesium alloy sheet of claim 2, wherein the secondary phase is _Al2Ca , _{Al8Mn5 ,} or a combination thereof. The magnesium alloy sheet material according to any one of claims 1 to 3, wherein the limit bending radius (LBR) value in the rolling direction (RD) of the magnesium alloy sheet material at 150 to 250°C is 0 to 0.5 R/t. The magnesium alloy sheet material according to any one of claims 1 to 4, wherein the limit bending radius (LBR) value in the sheet width direction (TD) at 150 to 250°C is 0 to 0.5 R/t. The magnesium alloy sheet material according to any one of claims 1 to 5, wherein the ratio of the limit bending radius (LBR) value in the sheet width direction (TD) to the rolling direction (RD) of the magnesium alloy sheet material at 150 to 250°C is 0.8 to 1.2. The magnesium alloy sheet material according to any one of claims 1 to 6, wherein the limit dome height (LDH) of the magnesium alloy sheet material is 8 mm or more. A method for producing the magnesium alloy sheet material according to any one of claims 1 to 7,
A step of preparing a molten alloy containing, relative to a total of 100% by weight, 0.5 to 1.5% by weight of Al, 0.5 to 1.5% by weight of Zn, 0.1 to 1.0% by weight of Ca, 0.01 to 1.0% by weight of Mn, the balance being Mg and other unavoidable impurities;
Casting the molten metal to prepare a casting material;
rolling the cast material to prepare a rolled material; and subjecting the rolled material to final annealing,
The step of rolling the cast material to prepare a rolled material is performed at a temperature range of 100 to 350° C.,
The step of final annealing the rolled material is carried out at 250 to 450 ° C. for 30 to 600 minutes,
The step of rolling the cast material to prepare a rolled material includes rolling the cast material at a reduction of 50% or less (excluding 0%) per rolling pass,
The step of rolling the cast material to prepare a rolled material further includes a step of intermediate annealing the rolled material,
The step of intermediate annealing the rolled material is carried out at a temperature range of 300 to 500 ° C. for 30 minutes to 6 hours.
A manufacturing method of magnesium alloy sheet material. In the step of preparing the molten alloy,
The method for producing a magnesium alloy sheet according to claim 8, wherein Al is 0.5 to 1.3 wt % relative to 100 wt % of the entire molten alloy. The step of rolling the cast material to prepare a rolled material includes:
The method for producing a magnesium alloy sheet according to claim 8 or 9, wherein the cast material is rolled once or at least twice. The step of casting the molten metal to prepare a casting material includes:
The method for producing the magnesium alloy sheet material according to any one of claims 8 to 10, wherein casting is performed by a strip casting method.

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