KR20180044213A - High formability magnesium alloy sheet and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a high formability magnesium alloy sheet and a manufacturing method thereof. According to one embodiment of the present invention, the magnesium alloy sheet comprises, with respect to 100 weight percent of the total alloy: 3.0 or less weight percent of Zn (excluding 0 weight percent); 1.5 or less weight percent of Ca (excluding 0 weight percent); 1.0 or less weight percent of Mn (excluding 0 weight percent); and the remainder being Mg and unavoidable impurities. Moreover, the magnesium alloy sheet satisfies [Zn] / [Ca] <= 4.0 and [Zn] + [Ca] > [Mn], wherein [Zn], [Ca], and [Mn] mean a weight percent of each component.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high magnesium alloy sheet,

One embodiment of the present invention relates to a high-form magnesium alloy sheet and a method of making the same.

In recent years, light weight (gram, gram) marketing has been actively performed in mobile and IT fields. More specifically, as the functions of the mobile device field become diversified, the product weight is required to be lighter. As a result, there is an increasing interest in magnesium plates having excellent non-strength (strength against density).

The density of magnesium is 1.74 g / cm 3, which is the lightest metal among the structural metals including aluminum and steel. In addition, it is a metal that is attracting attention in mobile and IT fields because of its excellent vibration absorbing ability and electromagnetic wave shielding ability. In addition, in the automobile sector, studies are being actively carried out in advanced countries including Europe to reduce the weight of the vehicle body due to the regulation of fuel economy and performance improvement, and magnesium is being reported as a substitute metal. However, since magnesium is expensive compared to competitive materials such as aluminum and stainless steel, its application is limited to only some parts that are required to be lightweight.

In addition, magnesium is difficult to form at room temperature due to hexagonal close packing (HCP). However, since the warm forming process is essential for the application of the product, the investment cost of the mold / heating device for the warm forming becomes large. In addition, it takes time for sticking, scratching, and heating between the mold and the material, thereby deteriorating the productivity. Therefore, not only the price of the magnesium material, but also the processing cost of the magnesium alloy is more expensive than the competitive material.

On the basis of this, a magnesium alloy for improving room temperature moldability has been developed. However, a lithium alloy or a rare earth element having a high value is added, or the manufacturing process is complicated.

An embodiment of the present invention provides a high-formed magnesium alloy sheet and a method of manufacturing the same by controlling the composition range of the Zn, Ca, and Mn components of the magnesium alloy sheet and the relationship of the components.

Specifically, it is intended to provide a magnesium alloy sheet excellent in moldability by controlling the Mg-Ca system secondary phase through the composition of the alloy and the manufacturing conditions.

The magnesium alloy sheet material according to one embodiment of the present invention contains not more than 3.0 wt% of Zn (excluding 0 wt%), not more than 1.5 wt% of Ca (not more than 0 wt%), not more than 1.0 wt% of Mn (Excluding 0% by weight), balance Mg and other unavoidable impurities. At this time, the magnesium alloy sheet material may further contain not more than 0.3% by weight of Al relative to 100% by weight of the entire magnesium alloy sheet material.

Specifically, the magnesium alloy sheet material can satisfy the following formulas (1) and (2).

[Zn] / [Ca] &lt; / = 4.0 - (1)

[Zn] + [Ca] > [Mn] - (2)

Here, [Zn], [Ca], and [Mn] refer to weight percent of each component.

The maximum aggregate strength based on the {0001} plane of the magnesium alloy sheet material may be 1 to 4.

The critical dome height (LDH) of the magnesium alloy sheet may be 7 to 10 mm.

The yield strength of the magnesium alloy sheet material may be 170 MPa or more.

The tensile strength of the magnesium alloy sheet material may be 240 MPa or more.

The elongation of the magnesium alloy sheet material may be 20% or more.

The magnesium alloy sheet material may include crystal grains having an average particle diameter of 1 to 20 mu m.

The magnesium alloy sheet material may include a Mg-Ca based secondary phase, and the average particle size of the secondary phase may be 30 탆 or less.

And may include 1 to 20 secondary phases per 100 [mu] m ^{2 of} the magnesium alloy sheet material area.

A method for producing a magnesium alloy sheet material according to another embodiment of the present invention is a method for producing a magnesium alloy sheet material, which comprises not more than 3.0 wt% of Zn (excluding 0 wt%), 1.5 wt% or less of Ca (excluding 0 wt% 1.0% by weight or less (excluding 0% by weight), the balance Mg and other unavoidable impurities to prepare a cast material; Subjecting the cast material to homogenization heat treatment; Subjecting the homogenized heat treated cast material to hot rolling to prepare a rolled material; And finally annealing the rolled material.

At this time, the magnesium alloy sheet material further contains not more than 0.3% by weight of Al relative to 100% by weight of the entire molten alloy melt, and the magnesium alloy sheet material can satisfy the following formulas (1) and (2).

[Zn] / [Ca] &lt; / = 4.0 - (1)

[Zn] + [Ca] > [Mn] - (2)

Here, [Zn], [Ca], and [Mn] refer to weight percent of each component.

The step of final annealing the rolled material can be carried out at a temperature in the range of 200 to 500 ° C. Concretely, it can be carried out for not more than 5 hours (excluding 0 hours).

The step of homogenizing the cast material may be carried out at a temperature of 300 to 500 ° C. Specifically, it can be carried out for 5 to 30 hours.

The step of hot-rolling the homogenized heat-treated cast material to prepare a rolled material can be rolled at a temperature ranging from 150 to 400 ° C. Specifically, it can be rolled once or twice at a reduction ratio of 40% or less (excluding 0%) per rolling.

More specifically, when the cast material is warm-rolled at least two times, intermediate annealing may be performed at least once between the warm rolling.

The intermediate annealing may be performed at a temperature in the range of 300 to 500 ° C. Specifically, the intermediate annealing can be performed for not more than 5 hours (excluding 0 hours).

According to an embodiment of the present invention, the composition range of the Zn, Ca, and Mn components of the magnesium alloy sheet material and the relationship of the above components can be controlled to provide a magnesium alloy sheet of high molding.

Specifically, it is possible to provide a magnesium alloy sheet material excellent in strength and room temperature moldability by controlling the Mg-Ca system secondary phase.

Fig. 1 is a photograph of the microstructure of the magnesium alloy sheet material of Example 2 and Comparative Example 2 observed with an optical microscope. Fig.
2 shows the results of analysis of the secondary phase components of Example 2 and Comparative Example 2 by SEM-EDS.
FIG. 3 shows the results of analysis of the {0001} planes of Example 2 and Comparative Example 3 by the XRD pole diagram and EBSD.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

Thus, in some embodiments, well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention. Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise. Also, singular forms include plural forms unless the context clearly dictates otherwise.

The magnesium alloy sheet material according to one embodiment of the present invention may contain not more than 3.0 wt% of Zn (excluding 0 wt%), not more than 1.5 wt% of Ca (not more than 0 wt%), not more than 1.0 wt% of Mn 0% by weight), balance Mg and other unavoidable impurities.

And may further contain not more than 0.3% by weight of Al relative to 100% by weight of the entire magnesium alloy sheet material.

The composition range of the aluminum component may be such that it is added at an impurity level as compared with essential additive elements such as zinc, calcium, and manganese in the magnesium alloy sheet according to one embodiment of the present invention.

The reason for limiting the composition and composition of the magnesium alloy sheet according to one embodiment of the present invention will be described in detail.

Zn may include 3.0 wt% or less, but 0 wt% is excluded.

More specifically, Zn may be 0.5 to 3.0 wt%.

More specifically, when zinc is added, such as calcium, it may segregate in the grain boundary and the twin crystal phase to contribute to the generation and growth of the non-bottom grain recrystallized grains. As a result, softening phenomenon of the bottom surface is brought about, and the slip of the bottom surface is activated to improve the formability of the plate material. Therefore, when it is added in an amount less than 0.5% by weight, it may be difficult to ensure moldability.

However, if it is added in an amount exceeding 3.0% by weight, it may adversely affect moldability because it forms a large amount of additional intermetallic compounds in addition to existing intermetallic compounds by bonding with magnesium and calcium. Further, when casting, sticking occurs more deeply and molding may be difficult. Accordingly, when zinc is contained in the above range, an effect of improving moldability at room temperature can be expected.

Ca may contain up to 1.5% by weight, but excluding 0% by weight.

More specifically, Ca may be 0.1 to 1.5% by weight.

More specifically, calcium, like zinc, may be segregated in grain boundaries and twin systems during addition to contribute to the production and growth of non-bottom recrystallized grains. As a result, softening phenomenon of the bottom surface is brought about, and the slip of the bottom surface is activated to improve the formability of the plate material. Therefore, when it is added in an amount of less than 0.1% by weight, it is difficult to secure moldability.

However, the addition of more than 1.5% by weight reduces the fluidity of the molten alloy and lowers the main constituent, so that the productivity may be reduced, cracks may be generated at the time of rolling, and the rolling property of the plate material may be deteriorated. Accordingly, when calcium is contained in the above range in the present invention, an effect of improving the room temperature moldability can be expected within a range that does not inhibit the main composition and rolling property.

Mn may include not more than 1.0 wt%, but not 0 wt%.

More specifically, manganese acts as a recrystallization nucleation site to generate fine grains, and then to suppress grain growth, thereby providing fine and uniform grains. Therefore, in the method of manufacturing a magnesium alloy sheet, which is another embodiment of the present invention described later, it is possible to provide fine crystal grains in the homogenization heat treatment step, and finely control the crystal grains of the final magnesium alloy sheet material.

Accordingly, when the manganese is contained in the range as described above, the crystal grains of the homogenized heat treatment plate are finely formed, and defects such as abnormal crystal growth and orange peel due to the shear band in the warm rolling step and surface cracks can be prevented . Therefore, the rolling property can be facilitated. In addition, when manganese is contained in the above range, impurities such as iron (Fe) and silicon (Si) can be controlled and the corrosion resistance can be excellent.

Therefore, a plate material having fine crystal grains can be produced through addition of manganese, so that both the strength and the formability can be excellent.

The magnesium alloy sheet material may satisfy the following formulas (1) and (2).

[Zn] / [Ca] &lt; / = 4.0 - (1)

[Zn] + [Ca] > [Mn] - (2)

Here, [Zn], [Ca], and [Mn] refer to weight percent of each component.

More specifically, the formula (1) may be 3 or less.

It is possible to prevent the secondary phase coarsening generated by further limiting the composition ratios of Zn and Ca components as well as the composition ratios as in the above formula (1), and realize the desired high strength and high molding properties.

Specifically, the magnesium alloy sheet material may satisfy formula (2) ([Zn] + [Ca]> [Mn]). Concretely, when the sum of the Zn and Ca composition is equal to or smaller than the composition of Mn, the rolling property and the formability may be deteriorated.

The magnesium alloy sheet material satisfying the above-described components and composition ranges may include a Mg-Ca based secondary phase. At this time, the average particle size of the secondary phase may be 30 탆 or less. Specifically, it may be 25 占 퐉 or less. More specifically, it may be 20 mu m or less.

The average particle diameter in this specification means the average diameter of the spherical substance present in the unit of measurement. If the material is an acetal, it means the diameter of the sphere calculated by approximating the spherical material to the spherical shape.

That is, the range of the secondary phase diameter is significantly smaller than that of the secondary phase of the general magnesium alloy plate.

When the average particle size of the secondary phase exceeds 30 탆, the moldability of the alloy material may be lowered.

As will be described later, this can be visually confirmed through the drawings.

And may include 1 to 20 secondary phases per 100 [mu] m ^{2 of} the magnesium alloy sheet material area.

When the number of the secondary phases is the same as above, the strength and moldability of the magnesium alloy sheet material can be excellent.

The magnesium alloy sheet material may include crystal grains having an average particle diameter of 1 to 20 mu m.

By controlling the composition and composition of the aforementioned magnesium alloy sheet material, it is possible to obtain the crystal grain size in the above range. More specifically, when the grain size of the magnesium alloy sheet is in the above range, the strength can be excellent.

The maximum aggregate strength based on the {0001} plane of the magnesium alloy sheet material may be 1 to 4.

Since the aggregate strength of the magnesium alloy sheet material is in the above range, since the crystal grains of various orientations are distributed and the fraction of the bottom grain (the crystal grains in the C axis orientation) is small, it is possible to provide a magnesium alloy sheet material excellent in moldability have.

In the present specification, the bottom crystal grains means a crystal grains having a bottom orientation. Specifically, magnesium has an HCP (Hexagonal Closed Pack) crystal structure. At this time, the crystal grains when the C axis of the crystal structure is parallel to the thickness direction of the plate material is referred to as crystal grains (that is, bottom crystal grains) Quot; Therefore, in the present specification, the bottom grain can also be expressed as "< 0001 > // C axis ".

Specifically, the smaller the maximum aggregate strength with respect to the {0001} plane of the magnesium alloy sheet material, the more crystal grains of various orientations are distributed. Further, as the crystal grains of various orientations are distributed and the fraction of the bottom surface crystal grains is lower, a magnesium alloy plate material having excellent formability can be obtained.

Therefore, the magnesium alloy sheet according to an embodiment of the present invention has a maximum aggregate strength of 1 to 4 on the {0001} plane, so that the moldability can be excellent.

The Erickson value of the magnesium alloy sheet at room temperature may be 7 to 10 mm.

In this specification, the Erickson value means an experimental value derived from the Ericsson test at room temperature. More specifically, the Erickson value refers to the height at which the sheet material is deformed until a fracture occurs, when the sheet material is deformed into a cup shape.

Therefore, the room temperature moldability can be compared through the Erickson value.

The yield strength of the magnesium alloy sheet material may be 170 MPa or more. Specifically, it may be 170 to 220 MPa.

Also, the tensile strength of the magnesium alloy sheet material may be 240 MPa or more. Specifically, it may be 240 to 300 MPa.

The elongation of the magnesium alloy sheet material may be 20% or more. Specifically, it may be 20 to 30%.

However, the present invention is not limited thereto. Specifically, the yield strength, the tensile strength, and the elongation are preferably as good as possible, and the magnesium alloy sheet according to one embodiment of the present invention can realize mechanical properties at least the minimum value.

In addition, the strength and elongation of the magnesium alloy sheet according to one embodiment of the present invention are excellent in strength and elongation as compared with the conventional case in which an additional element is added to the AZ-based magnesium alloy.

Thus, by controlling the composition and composition of the magnesium alloy sheet material as described above, it is possible to provide a magnesium alloy sheet material excellent in both strength and moldability.

A method for producing a magnesium alloy sheet material according to another embodiment of the present invention is a method for producing a magnesium alloy sheet material, which comprises not more than 3.0 wt% of Zn (excluding 0 wt%), 1.5 wt% or less of Ca (excluding 0 wt% 1.0% by weight or less (excluding 0% by weight), the balance Mg and other unavoidable impurities, to prepare a casting material (S10); A step (S20) of homogenizing the cast material; A step (S30) of hot-rolling the homogenized heat-treated cast material to prepare a rolled material; And a final annealing step (S40) of the rolled material. The present invention also provides a method of manufacturing a magnesium alloy sheet material.

(Excluding 0 wt.%), Ca: 1.5 wt.% Or less (excluding 0 wt.%), Mn: 1.0 wt.% Or less (excluding 0 wt.%) (S10) of preparing a cast material by casting a molten alloy containing impurities such as aluminum and other unavoidable impurities.

And may further contain not more than 0.3% by weight of Al relative to 100% by weight of the entire magnesium alloy molten metal.

Specifically, the magnesium alloy melt can satisfy the following formulas (1) and (2).

[Zn] / [Ca] &lt; / = 4.0 - (1)

[Zn] + [Ca] > [Mn] - (2)

Here, [Zn], [Ca], and [Mn] refer to weight percent of each component.

The reason for limiting the composition and the composition range of the molten alloy is the same as the reason for limiting the composition and the composition range of the magnesium alloy plate described above, so that the description is omitted.

More specifically, the alloy melt can be cast by gravity casting, continuous casting, strip casting (thin sheet casting), sand casting, vacuum casting, centrifugal casting, die casting, or chisel molding.

However, the present invention is not limited thereto, and any method capable of producing a cast material is possible.

Thereafter, a step (S20) of homogenizing the cast material is performed; Can be performed.

Specifically, it can be carried out at 300 to 500 ° C.

More specifically, it may be carried out for 5 to 30 hours.

More specifically, overheating can be prevented by homogenizing the casting material in the temperature and time range, and the microstructure and segregation of the casting material can be sufficiently homogenized.

Thereafter, step (S30) of warm rolling the homogenized heat-treated cast material to prepare a rolled material may be performed.

Specifically, hot rolling can be performed in a temperature range of 150 to 400 占 폚.

More specifically, in the case of warm rolling at less than 150 ° C, a large amount of surface scattering type cracks or edge cracks may occur.

On the other hand, when warm rolling is performed at a temperature higher than 400 ° C, there may arise a problem of equipment such as the necessity of changing the component of the equipment to a heat resistant material for rolling at a high temperature. As a result, problems such as an increase in process cost and a decrease in productivity are caused, and mass production of the magnesium alloy sheet material may be difficult.

In addition, the cast material can be warm-rolled at least once or twice at a reduction ratio of 40% or less (excluding 0%) per rolling.

The homogenized heat-treated cast material can be warm-rolled by using a warm rolling mill.

When the cast material is warm-rolled at least two times, intermediate annealing may be performed at least once between the warm rolling. The intermediate annealing may be carried out at 300 to 500 ° C.

The intermediate annealing can be performed for 5 hours or less (excluding 0 hours).

More specifically, if the temperature and time range are not satisfied, the stress of the hardened tissue is not sufficiently solved by the cumulative rolling reduction, and the annealing process may not be performed properly. Further, the abnormal crystal grains can grow due to excessive annealing.

Further, the thickness of the rolled material that is warm-rolled at least twice may be 2.0 mm or less.

Thereafter, a step (S40) of final annealing the rolled plate can be carried out.

Concretely, it can be carried out at 200 to 500 ° C.

More specifically, it can be carried out for not more than 5 hours (excluding 0 hours).

More specifically, by finally annealing the rolled material in the temperature and time range, the magnesium alloy sheet produced can secure the desired moldability at room temperature.

Hereinafter, the embodiment will be described in detail. The following examples are illustrative of the present invention only and are not intended to limit the scope of the present invention.

Example  And Comparative Example

As shown in the following Table 1, when the range according to one embodiment of the present invention is satisfied, it is classified as an invention material. Meanwhile, when the range according to one embodiment of the present invention is not satisfied, it is classified as a comparative material.

Then, using the inventive material and the comparative material shown in Table 1, a magnesium alloy plate material was produced under the following conditions.

First, an alloyed molten metal of an inventive material and a comparative material was cast to produce a cast material.

Thereafter, the cast material was subjected to homogenization heat treatment at 330 to 450 DEG C for 16 hours.

The homogenized heat-treated cast material was rolled at 300 DEG C at a reduction ratio of 10 to 20% to prepare a rolled material. At this time, intermediate annealing was performed at 450 占 폚 for 0.5 to 1 hour.

Finally, the rolled material was subjected to final annealing as shown in Table 2 below to produce a magnesium alloy sheet material.

division Alloy name Al Zn Ca Mn Equation (1)
Zn + Ca > Mn Equation (2)
Zn / Ca Inventory 1 Mg-1.0Zn-0.6Ca-0.3Mn - 1.07 0.61 0.35 O 1.75 Inventory 2 Mg-1.5Zn-0.6Ca-0.3Mn - 1.55 0.60 0.35 O 2.58 Inventory 3 Mg-2.0Zn-0.6Ca-0.3Mn - 2.23 0.59 0.31 O 3.77 Comparison 1 Mg-0.3Zn-0.2Ca-1.2Mn - 0.38 0.22 1.26 X 1.73 Comparative material 2 Mg- 3.0 Zn-0.6Ca-0.3Mn - 3.04 0.55 0.32 O 5.52 Comparative material 3 Mg-3.0Al-1.0Zn (AZ31) 2.98 0.79 - 0.33 O - Comparison 4 Mg-3.0Al-0.6Ca-1.0Zn 2.98 0.79 0.65 0.33 O 1.22 Comparative material 5 Mg-2.0Zn-0.1Ca-0.3Mn - 2.09 0.11 0.32 O 20

As a result, Table 2 shows mechanical properties of the magnesium alloy sheet according to Examples and Comparative Examples and Erickson's values at room temperature.

The Ericsson numerical measurement method is as follows.

Specifically, a magnesium alloy plate having a size of 50 to 60 mm in each of the width and the length was used, and a lubricant was used on the surface of the plate to reduce the friction between the plate and the spherical punch.

At this time, the temperature of the die and the spherical punch was set at room temperature.

More specifically, after inserting the magnesium alloy sheet material between the upper die and the lower die, the outer peripheral portion of the sheet material was fixed with a force of 10 kN, and then, using a spherical punch having a diameter of 20 mm, . Thereafter, the punch was inserted until the plate material was broken, and then the deformation height of the plate material was measured at the time of breaking.

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

Kinds division Final annealing temperature
And time Yield strength
(MPa) The tensile strength
(MPa) Elongation
(%) Erickson Value (mm) Inventory 1 Example  One 400 ° C, 30 minutes 174 246 23.1 8.3 Inventory 2 Example  2 400 ° C, 30 minutes 185 254 22.2 9.0 Inventory 3 Example  3 400 ° C, 30 minutes 191 263 20.9 8.1 Comparison 1 Comparative Example 1 400 ° C, 30 minutes 125 208 23.4 5.5 Comparative material 2 Comparative Example 2 400 ° C, 30 minutes 173 253 19.1 6.9 Comparative material 3 Comparative Example 3 350 ℃, 30 minutes 165 257 24.5 3.5 Comparison 4 Comparative Example 4 400 ° C, 30 minutes 151 251 19.6 7.4 Comparative material 5 Comparative Example 5 400 ° C, 30 minutes 152 237 22.6 7.1

As a result, it can be seen that Examples 1 to 3 have a much higher Ericson value than the Comparative Examples. Specifically, it can be seen that the present example has a yield strength of 170 MPa or more, a tensile strength of 240 MPa or more, an elongation of 20% or more, and a room temperature Erickson value of 7 mm or more.

Specifically, the composition of Zn, Ca, and Mn satisfies the range according to one embodiment of the present invention, but satisfies both the formula [Zn] + [Ca]> [Mn] and the formula [Zn] / [Ca] It can be confirmed that the comparative example which does not have the effect of heating strength and formability.

These characteristics can also be confirmed through the drawings.

Fig. 1 is a photograph of the microstructure of the magnesium alloy sheet material of Example 2 and Comparative Example 2 observed with an optical microscope. Fig.

As a result, comparing the microstructures of Example 2 and Comparative Example 2 in which the final annealing conditions were the same and the components of the alloy were different, the secondary phase in the form of agglomerated black in Comparative Example 2, It can be seen with the naked eye.

In addition, in the case of Comparative Example 2 using Comparative Material 2 having a higher Zn content than Example 2 using Invention Material 2, it can be seen that the size of the secondary phase is coarse.

As described above, the coarse secondary phase adversely affects the moldability.

As a result, as shown in Table 2, the Erickson value of Comparative Example 2 is 6.9 mm, while the Erickson value of Example 2 is 9.0 mm.

In addition, when the content of Zn is added in an amount exceeding 3% by weight, the crystal grains can be locally coarsened as in Comparative Example 2. [ As a result, mechanical properties and moldability may be deteriorated.

2 shows the results of analysis of the secondary phase components of Example 2 and Comparative Example 2 by SEM-EDS.

When a sample is irradiated with a certain wavelength using a SEM-EDS analyzer, a peak may appear at a value corresponding to the energy of the material. At this time, component analysis can be derived from the wavelengths shown.

Specifically, it can be seen that a secondary image (dark gray spherical shape) is finely dispersed in an EDS (Energy Dispersive Spectroscopy) photograph of a scanning electron microscope (SEM) of Example 2. As a result of analyzing the secondary phase component of Example 2, it can be seen that it is a Mg-Ca secondary phase. At this time, the size of the secondary phase was about 20 mu m or less.

On the other hand, the secondary phase (white) of the microstructure of Comparative Example 2 in which the content of Zn exceeded 3.0 wt% was confirmed. However, as a result of analyzing the secondary phase component of Comparative Example 2, it can be seen that the secondary phase is a Ca-Mg-Zn three-phase system.

In other words, in Example 2, as a result of the content ratio of Zn and Ca and the content ratio of Zn / Ca satisfying all the ranges defined in the embodiment of the present invention, the Mg-Ca binary system secondary phase It was also confirmed that the formation of the phase was easy.

Further, as can be seen from FIG. 2, the secondary phase of Comparative Example 2 in which the Zn content is excessive is larger than that of the secondary phase of Example 2.

On the other hand, in Example 2 of the present application, the Ma-Ca-based secondary phase is finely dispersed and distributed at a level of 20 탆 or less, thereby contributing to improvement of the strength and moldability of the magnesium alloy sheet material.

FIG. 3 shows the results of analysis of the {0001} planes of Example 2 and Comparative Example 3 by the XRD pole diagram and EBSD.

Specifically, FIG. 3 shows the texture according to the crystal orientation of the crystal grains by using the XRD pole figure method and EBSD (Electron Backscatter Diffraction) method.

The EBSD can inject electrons into the specimen through the e-electron beam and measure the crystal orientation of the grains using inelastic scattering diffraction at the back of the specimen.

The pole figure is a stereo projection of the direction of the arbitrarily fixed crystal coordinate system in the specimen coordinate system. More specifically, the poles for the {0001} planes of the crystal grains of various orientations can be displayed in the reference coordinate system, and the poles can be represented by plotting density contours according to the poles density distribution. At this time, the poles are fixed in a specific lattice direction by the Bragg angle, and a plurality of poles can be displayed for a single crystal.

Therefore, the numerical representation of the density distribution values of the contour lines indicated by the poling method can be referred to as the set intensity for the {0001} plane.

Accordingly, as the aggregation strength becomes smaller, crystal grains of various orientations are distributed. As the aggregation strength becomes larger, it can be interpreted that the crystal grains of < 0001 > // C axis orientation are distributed much.

First, as shown in Fig. 3, it can be seen that the grain size of the grain in Example 2 is as fine as 1 to 20 占 퐉 as compared with that of Comparative Example 3.

In addition, the maximum aggregate strength of the {0001} plane of Example 2 was 2.46. Which is significantly lower than that of Comparative Example 3 with a maximum aggregate strength of 12.11. From this, it can be interpreted that the crystal grains of various orientations are distributed in Example 2 of the present invention, whereas the crystal grains (bottom crystal grains) of the <0001> // C axis orientation are distributed much in Comparative Example 3.

From this, it can be seen that the embodiment has better moldability because the fraction of the bottom surface crystal grain is smaller than that of the comparative example.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (19)

3.0 wt% or less (excluding 0 wt%), Ca: 1.5 wt% or less (excluding 0 wt%), Mn: 1.0 wt% or less (excluding 0 wt%), balance Mg and others Including unavoidable impurities,
Further comprising, by weight, not more than 0.3 wt% of Al, based on 100 wt% of the entire magnesium alloy plate material,
A magnesium alloy plate material satisfying the following formulas (1) and (2):
[Zn] / [Ca] &lt; / = 4.0 - (1)
[Zn] + [Ca] &gt; [Mn] - (2)
[Zn], [Ca], and [Mn] refer to weight percent of each component.
The method of claim 1,
Wherein the magnesium alloy sheet has a maximum aggregate strength of 1 to 4 on a {0001} plane.
The method of claim 1,
Wherein the magnesium alloy sheet has a critical dome height (LDH) of 7 to 10 mm.
The method of claim 1,
And the yield strength of said magnesium alloy sheet material is not less than 170 MPa.
The method of claim 1,
Wherein the magnesium alloy sheet has a tensile strength of 240 MPa or more.
The method of claim 1,
Wherein the magnesium alloy sheet material has an elongation of at least 20%.
The method of claim 1,
Wherein the magnesium alloy sheet material is a magnesium alloy sheet material including crystal grains having an average particle diameter of 1 to 20 mu m
The method of claim 1,
Wherein the magnesium alloy sheet material comprises a Mg-Ca based secondary phase,
And the average particle size of the secondary phase is 30 占 퐉 or less.
The method of claim 1,
Wherein the magnesium alloy sheet material comprises 1 to 20 secondary phases per 100 mu m ^{2 of} the magnesium alloy sheet material area.
3.0 wt% or less (excluding 0 wt%), Ca: 1.5 wt% or less (excluding 0 wt%), Mn: 1.0 wt% or less (excluding 0 wt%), balance Mg and others Casting an alloy melt containing unavoidable impurities to prepare a cast material;
Subjecting the cast material to homogenization heat treatment;
Subjecting the homogenized heat treated cast material to hot rolling to prepare a rolled material; And
And finally annealing the rolled material. The method of manufacturing the magnesium alloy sheet material includes:
Wherein the magnesium alloy sheet further comprises at least 0.3% by weight of Al relative to 100% by weight of the alloy melt, and the magnesium alloy sheet satisfies the following formulas (1) and (2)
[Zn] / [Ca] &lt; / = 4.0 - (1)
[Zn] + [Ca] &gt; [Mn] - (2)
[Zn], [Ca], and [Mn] refer to weight percent of each component.
11. The method of claim 10,
Wherein the step of final annealing the rolled material comprises:
A method for producing a magnesium alloy sheet material, the method comprising:
12. The method of claim 11,
Wherein the step of final annealing the rolled material comprises:
A method of manufacturing a magnesium alloy sheet material which is conducted for 5 hours or less (excluding 0 hours).
11. The method of claim 10,
A step of subjecting the cast material to a homogenizing heat treatment,
A method for producing a magnesium alloy sheet material in a temperature range of 300 to 500 ° C.
The method of claim 13,
A step of subjecting the cast material to a homogenizing heat treatment,
Wherein the magnesium alloy sheet material is applied for 5 to 30 hours.
11. The method of claim 10,
Hot rolling the homogenized heat treated cast material to prepare a rolled material,
A method for producing a magnesium alloy sheet material which is rolled at a temperature range of 150 to 400 占 폚.
16. The method of claim 15,
Hot rolling the homogenized heat treated cast material to prepare a rolled material,
And rolling at least once or twice or more at a reduction ratio of 40% or less (excluding 0%) per rolling.
17. The method of claim 16,
Hot-rolling the homogenized heat-treated cast material to prepare a rolled sheet material,
The cast material is warm-rolled twice or more,
And intermediate annealing is performed at least once between the warm rolling.
The method of claim 17,
Wherein the intermediate annealing is performed in a temperature range of 300 to 500 占 폚.
The method of claim 18,
Wherein the intermediate annealing is performed for 5 hours or less (excluding 0 hours).

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