KR101581852B1 - Method for manufacturing of magnesium alloy sheet with improved formability and the magnesium alloy sheet thereby - Google Patents
Method for manufacturing of magnesium alloy sheet with improved formability and the magnesium alloy sheet thereby Download PDFInfo
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- KR101581852B1 KR101581852B1 KR1020140082984A KR20140082984A KR101581852B1 KR 101581852 B1 KR101581852 B1 KR 101581852B1 KR 1020140082984 A KR1020140082984 A KR 1020140082984A KR 20140082984 A KR20140082984 A KR 20140082984A KR 101581852 B1 KR101581852 B1 KR 101581852B1
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Abstract
Description
The present invention relates to a method of manufacturing a magnesium alloy sheet material and a magnesium alloy sheet material produced thereby, and a method of improving the moldability of a magnesium alloy sheet material by simultaneously compressively deforming a magnesium alloy sheet material in a biaxial direction and heat- ≪ / RTI >
Magnesium is the lightest metal with the smallest density among structural metals including aluminum and steel at a density of 1.74 g / cm < 3 >. In addition, it has high non-rigidity, excellent machinability, vibration absorption ability, electromagnetic wave shielding property and the like.
It is also the eighth most abundant element on earth, accounting for 2.7% of the earth's surface, and 0.13% of the seawater is made up of magnesium, so resources are endless. Furthermore, it is an environmentally friendly material because it is easy to recycle.
The magnesium alloy having the above characteristics has recently been increasingly used in place of the aluminum alloy in accordance with the demand for light weight of transportation equipment for improving the fuel consumption. In addition, according to the requirements of light weight and excellent electromagnetic wave shielding, 3Cs products Is increasing.
However, the magnesium alloy has a problem of lower strength, ductility and corrosion resistance than the aluminum alloy. Among these, the ductility of the magnesium alloy can be improved by increasing the processing temperature, but it is difficult to perform compression molding on a product having a complicated shape or a sharp corner, which has limitations in commercialization.
In order to improve the moldability of the magnesium plate, a method of adding a rare earth element to activate the non-slip slip system and a method of activating the slip of the slip by weakening the bottom surface texture by severe shear deformation have been proposed.
However, these methods have limited application due to their high production cost and low productivity.
On the other hand, Japanese Patent No. 19311335 discloses a magnesium alloy plate, a resin-coated magnesium alloy sheet,
discloses a method of producing a magnesium alloy molded article. Specifically, a magnesium alloy sheet and a resin film are provided, and at least one surface of the magnesium alloy sheet is covered with the resin film. The dynamic elastic modulus of the resin film at 20 ° C is 1.0 × 10 9 N / m 2 or more and 3.5 x 10 9 N / m 2 or less and a breaking extension of 100% or more and 600% or less as measured according to JIS K7127 of the resin film, and the magnesium alloy plate Coated magnesium alloy plate with a peel strength of 5 N / 20 mm or more.
However, the above method introduces a resin separately to magnesium, which makes it difficult to apply a pure magnesium alloy sheet material.
Recently, a method of weakening the bottom surface texture by inducing twinning in the lateral direction of the magnesium plate with developed bottom texture has been proposed. However, this method has a problem that it can not be applied to a thin plate which is expected to be used.
Accordingly, the inventors of the present invention have confirmed that moldability can be improved by compressive deformation in a biaxial direction and heat treatment at a certain temperature while carrying out a study on a method of producing a magnesium alloy that can be molded into a thin plate material.
SUMMARY OF THE INVENTION [0006]
And a method of manufacturing a magnesium alloy sheet material.
A further object of the present invention is to provide
And a method for improving moldability of a magnesium alloy sheet material.
According to an aspect of the present invention,
(Step 1) simultaneously performing a compression deformation of the magnesium alloy sheet material in a direction perpendicular to the rolling surface direction and the rolling surface direction; And
And a step of heat treating the magnesium alloy sheet material (step 2).
Further, according to the present invention,
(Step 1) simultaneously performing a compression deformation of the magnesium alloy sheet material in a direction perpendicular to the rolling surface direction and the rolling surface direction; And
And a step of heat treating the magnesium alloy sheet material (step 2). The present invention also provides a method for improving the moldability of a magnesium alloy sheet material.
The magnesium alloy sheet manufacturing method according to the present invention can improve the moldability at room temperature by changing the texture to non-bottom surface by performing the biaxial forming and heat treatment, and does not cause buckling phenomenon and is applied to thinner plate There are advantages.
1 is a schematic diagram showing step 1 of the manufacturing method according to the present invention;
FIG. 2 is a photograph of a magnesium alloy plate material before and after the deformation of step 1 of Example 1 by an optical microscope; FIG.
FIG. 3 is a graph showing a photograph of a magnesium alloy plate material subjected to the heat treatment in Example 2 and an azimuthal difference distribution observed by electron backscattering diffraction; FIG.
FIG. 4 is a graph showing a photograph of a magnesium alloy plate material subjected to the heat treatment in Example 1 and an azimuth angle difference distribution observed by electron backscattering diffraction; FIG.
5 is a GND density photograph of an inverse pole figures (IPF) map and a commercial program crosscourt obtained by observing a magnesium alloy sheet after deformation of step 1 of Example 1 by electron backscattering diffraction;
6 is a graph showing Erickson test conducted on the magnesium alloy sheet produced in Examples 1 and 2 and Comparative Examples 1 and 2, and the height of the limit dome.
According to the present invention,
(Step 1) simultaneously performing a compression deformation of the magnesium alloy sheet material in a direction perpendicular to the rolling surface direction and the rolling surface direction; And
And a step of heat treating the magnesium alloy sheet material (step 2).
Hereinafter, a method of manufacturing a magnesium alloy sheet according to the present invention will be described in detail.
In the method of manufacturing a magnesium alloy sheet material according to the present invention, the step 1 is a step of compressively deforming a magnesium alloy sheet material in a direction perpendicular to a rolling direction and a direction perpendicular to a rolling direction. Fig. 1 shows an example of the step 1.
In the past, a method of weakening the bottom surface texture has been proposed by compressing the magnesium plate having the developed bottom surface texture in the lateral direction to induce twinning. However, there is a problem that it can not be applied to thinner sheets.
On the other hand, the present invention not only compressively deforms the magnesium alloy sheet material in the direction perpendicular to the rolling direction, but also compresses and deforms simultaneously in the direction of the rolling surface, so that buckling does not occur and is applied to thin sheet materials This is possible.
In addition, the difference in residual stress between grains is large due to biaxial deformation, which leads to the growth of the twinned grains in the heat treatment step of the subsequent process, so that the texture can be changed to non-basal and the formability can be improved .
At this time, the magnesium alloy sheet material may be at least one selected from the group consisting of AZ31, ZM21, ZC63, AZ91, AZ91D, AM50A, AM60B and AZ81, but the magnesium alloy sheet material is not limited thereto.
The compression deformation of step 1 can be performed at room temperature, but is not limited thereto.
The compressive strain in the direction perpendicular to the rolled surface direction of the step 1 can be performed with a strain of 1 to 10%.
If the compressive strain is performed with a strain of less than 1%, grain growth may occur only in the specific crystal grains of the heat treatment in step 2, resulting in a structure in which the crystal grain size is uneven, and when the compressive strain exceeds 15% A buckling phenomenon may occur.
The stress in the rolling direction direction of the step 1 may be 400 to 600 kgf / mm 2 .
If the stress is less than 400 kgf / mm 2 , there is a problem of buckling due to compressive deformation along the axis on the rolled surface. When the stress exceeds 600 kgf / mm 2 , Increasing the friction may cause problems such as increased load and specimen damage when compressing in the width direction.
The thickness of the magnesium plate of step 1 may be 0.1 to 30 mm.
In the present invention, deformation is simultaneously performed in the biaxial direction, so that a thinner magnesium plate can be molded.
In the method of manufacturing a magnesium alloy sheet material according to the present invention, the step 2 is a step of heat-treating the magnesium alloy sheet material.
By heat-treating the plate subjected to biaxial deformation, the growth of the twined grains is induced, and the texture can be changed to non-basal and the formability can be improved.
The heat treatment in step 2 may be performed at 250 to 400 ° C.
If the heat treatment in step 2 is carried out at a temperature of less than 250 ° C, the tensile twin is still distributed in the microstructure and crystal grains may not grow, and the heat treatment in step 2 If the temperature is higher than 400 DEG C, the size of crystal grains may become coarsened.
The heat treatment in step 2 may be performed for 30 minutes to 2 hours.
If the heat treatment of step 2 is carried out for less than 30 minutes, the tensile twin is still distributed in the microstructure, and only a specific crystal grain grows, causing a problem of nonuniform distribution of crystal grain size And if the heat treatment in step 2 is performed for more than 2 hours, there may arise a problem of increase in crystal grain size and process economical cost.
Further, according to the present invention,
A magnesium alloy sheet produced according to the above production method is provided.
According to the above manufacturing method, the magnesium alloy sheet material can be manufactured in which the bottom surface texture is weakened due to the change of the microstructure of the magnesium alloy sheet material and the moldability is improved.
Further,
An electronic product case including the magnesium alloy plate, or an automotive exterior plate.
Magnesium is characterized by high non-strength, excellent machinability, vibration absorption ability, electromagnetic wave shielding property and the like.
The magnesium alloy sheet manufactured according to the above-described method has the above-described merits as well as excellent moldability, so that it can be applied to various products such as an electronic case and an automobile exterior panel. However, the use of the magnesium alloy sheet is limited It is not.
According to the present invention,
(Step 1) simultaneously performing a compression deformation of the magnesium alloy sheet material in a direction perpendicular to the rolling surface direction and the rolling surface direction; And
And a step of heat treating the magnesium alloy sheet material (step 2). The present invention also provides a method for improving the moldability of a magnesium alloy sheet material.
Hereinafter, the method for improving the moldability of the magnesium alloy sheet according to the present invention will be described in detail.
In the method for improving the moldability of the magnesium alloy sheet material according to the present invention, the step 1 is a step of compressively deforming the magnesium alloy sheet material simultaneously in the direction of the rolling surface and the direction perpendicular to the rolling surface direction.
At this time, the magnesium alloy sheet material may be at least one selected from the group consisting of AZ31, ZM21, ZC63, AZ91, AZ91D, AM50A, AM60B and AZ81, but the magnesium alloy sheet material is not limited thereto.
The compression deformation of step 1 can be performed at room temperature, but is not limited thereto.
The compressive strain in the direction perpendicular to the rolled surface direction of the step 1 can be performed with a strain of 1 to 10%.
If the compressive strain is performed with a strain of less than 1%, grain growth may occur only in the specific crystal grains of the heat treatment in step 2, resulting in a structure in which the crystal grain size is uneven, and when the compressive strain exceeds 15% A buckling phenomenon may occur.
The stress in the rolling direction direction of the step 1 may be 400 to 600 kgf / mm 2 .
If the stress is less than 400 kgf / mm 2 , there is a problem of buckling due to compressive deformation along the axis on the rolled surface. When the stress exceeds 600 kgf / mm 2 , Increasing the friction may cause problems such as increased load and specimen damage when compressing in the width direction.
The thickness of the magnesium plate of step 1 may be 0.1 to 30 mm.
In the present invention, deformation is simultaneously performed in the biaxial direction, so that a thinner magnesium plate can be molded.
In the method of improving moldability of a magnesium alloy sheet material according to the present invention, the step 2 is a step of heat-treating the magnesium alloy sheet material.
The heat treatment in step 2 may be performed at 250 to 350 ° C.
If the heat treatment in step 2 is carried out at a temperature of less than 250 ° C, the tensile twin is still distributed in the microstructure and crystal grains may not grow, and the heat treatment in step 2 If the temperature is higher than 400 DEG C, the size of crystal grains may become coarsened.
The heat treatment in step 2 may be performed for 30 minutes to 2 hours.
If the heat treatment of step 2 is carried out for less than 30 minutes, the tensile twin is still distributed in the microstructure, and only a specific crystal grain grows, causing a problem of nonuniform distribution of crystal grain size And if the heat treatment in step 2 is performed for more than 2 hours, there may arise a problem of increase in crystal grain size and process economical cost.
Hereinafter, the present invention will be described in detail with reference to Examples. However, the following examples are intended to illustrate the present invention, but the present invention is not limited to the following examples.
≪ Example 1 >
Step 1: A AZ31 magnesium alloy sheet material (thickness: 1.2 mm) rolled and processed was compression-deformed in a direction perpendicular to the rolling direction by 5% in the rolling direction and subjected to a stress of 500 kgf / mm 2 in the thickness direction of the sheet material Biaxial deformation was performed.
Step 2: The modified magnesium alloy sheet material was heat-treated at 300 ° C for 1 hour.
≪ Example 2 >
A magnesium alloy sheet material was prepared in the same manner as in Example 1, except that the heat treatment was performed at a temperature of 200 ° C in the step 2 of Example 1.
≪ Example 3 >
A magnesium alloy sheet material was prepared in the same manner as in Example 1 except that the magnesium alloy sheet material having a thickness of 10 mm was used in Step 1 of Example 1 above.
<Example 4>
A magnesium alloy sheet material was prepared in the same manner as in Example 1 except that the magnesium alloy sheet material having a thickness of 30 mm was used in Step 1 of Example 1 above.
≪ Comparative Example 1 &
The rolled AZ31 magnesium alloy sheet (thickness: 1.2 mm) was heat-treated at 300 占 폚 for 1 hour.
≪ Comparative Example 2 &
A magnesium alloy plate was produced in the same manner as in Comparative Example 1, except that the heat treatment was performed at a temperature of 200 ° C in Comparative Example 1.
Experimental Example 1 Microstructure Analysis of Magnesium Alloy Sheet
In order to analyze the microstructure of the magnesium alloy sheet material of Example 1, the magnesium alloy sheet material of Example 1 and the magnesium alloy sheet material after the deformation were observed with an optical microscope. The results are shown in Fig. 2, and an electron backscattering diffraction (EBDS ). The results are shown in FIGS. 3 and 4. The inverse pole figures (IPF) map in the plate thickness direction ND and the GND (crosscourt) analysis using the commercial program cross- The geometrically necessary dislocation density was observed and the results are shown in Fig.
As shown in Fig. 2, a microstructure having an average crystal grain size of 8 mu m was observed before the deformation of the magnesium alloy, and after the biaxial deformation, the crystal grains were tweened to have a microstructure having an average crystal grain size of 3.78 mu m have.
As shown in FIG. 3 and FIG. 4, the magnesium microstructure after the heat treatment was examined. As a result, it was found that the microstructure was not changed and the tensile twin was still present in Example 2 in which the heat treatment was performed at 200 ° C. However, in the case of Example 1 in which the heat treatment is performed at 300 ° C, it can be seen that the crystal grains grow, the bottom texture is weakened, and the tensile twin is annihilated.
Observing the crystal grains after the deformation of Example 1 in Fig. 5, it can be seen that the non-bottom side texture is grown due to the uneven deformation.
As a result, grains having a large difference in residual stress due to biaxial deformation of magnesium are produced, which leads to the growth of the twinned grains in the heat treatment step, so that the texture changes to non-basal.
<Experimental Example 2> Moldability analysis of magnesium alloy sheet
The magnesium alloy sheet materials produced in Examples 1 and 2 and Comparative Examples 1 and 2 were subjected to an Ericsson test at room temperature with a punch speed of 10 mm / s, a punch diameter of 20 mm and a specimen diameter of 50 mm, 6.
As shown in Fig. 6, in the case of Comparative Examples 1 and 2 in which the magnesium raw material was subjected only to the heat treatment without being deformed, the height of the limit dome was about 2.27 mm regardless of the temperature of the heat treatment. On the other hand, in case of Example 2 in which heat treatment was performed at 200 ° C after compression deformation, the limit dome height was 2.92 mm, and in Example 1 where deformation was performed at 300 ° C, the limit dome height was 4.30 mm 0.65 to 2.03 mm. In particular, in the case of Example 1 in which the heat treatment was performed at 300 ° C, it was found that the limit dome height was improved by about 90% as compared with Comparative Example 1.
This shows that the moldability of the magnesium alloy sheet material is improved by performing biaxial deformation, and especially when the heat treatment is performed at a temperature of 300 ° C after deformation, the moldability is higher.
Further, the magnesium alloy sheet material prepared in Example 3 was made into a processed specimen (thickness: 1.2 mm, diameter: 50 mm), the punch speed was 10 mm / s, the punch diameter was 20 mm, the specimen diameter was 50 mm, After the Ericsson test was carried out, the results are shown in Table 2.
As shown in Table 2, in Example 3 in which deformation and heat treatment were performed on a 10 mm plate, the limit dome height was 4.5 mm.
As a result, it can be seen that the magnesium alloy sheet material having a thickness of 10 mm is also biaxially deformed to improve the moldability of the magnesium alloy sheet material.
Claims (8)
(Step 2) of heat treating the magnesium alloy sheet material,
Wherein the compressive strain in the direction perpendicular to the rolling surface direction is performed at a strain of 1 to 10%.
Wherein the compressive strain of step 1 is performed at room temperature.
The above-
A lower die for positioning the magnesium alloy sheet material; A positioning pin provided on the lower die for fixing a position of the magnesium alloy sheet material positioned on the lower die; And an upper die positioned opposite the lower die and positioned on the other side of the face of the magnesium alloy sheet where the lower die is located,
The compression deformation in the rolling direction is performed by an anti-buckling force and a clamming force acting on the upper die,
Wherein the compression deformation in the direction perpendicular to the rolling surface direction is performed by a compression force acting on the lower die.
Wherein the stress in the direction of the rolling surface of step 1 is 400 to 600 kgf / mm < 2 >.
Wherein the heat treatment in step 2 is performed at 250 to 400 캜.
Wherein the heat treatment in step 2 is performed for 30 minutes to 2 hours.
(Step 2) of heat treating the magnesium alloy sheet material,
Wherein the compression deformation in the direction perpendicular to the rolling surface direction is performed at a strain of 1 to 10%.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110129695A (en) * | 2019-05-30 | 2019-08-16 | 重庆科技学院 | A method of preparing high performance magnesium alloy board |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR20110122902A (en) * | 2010-05-06 | 2011-11-14 | 국민대학교산학협력단 | Methods of controlling texture of material, and mg or mg alloy material formed using the same |
| KR20130092774A (en) * | 2012-02-13 | 2013-08-21 | 한국기계연구원 | A method for increasing formability of magnesium alloy sheet and magnesium alloy sheet prepared by the same method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR20110122902A (en) * | 2010-05-06 | 2011-11-14 | 국민대학교산학협력단 | Methods of controlling texture of material, and mg or mg alloy material formed using the same |
| KR20130092774A (en) * | 2012-02-13 | 2013-08-21 | 한국기계연구원 | A method for increasing formability of magnesium alloy sheet and magnesium alloy sheet prepared by the same method |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110129695A (en) * | 2019-05-30 | 2019-08-16 | 重庆科技学院 | A method of preparing high performance magnesium alloy board |
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