KR102407828B1 - Wrought magnesium alloys with high mechanical properties and method for preparing the same - Google Patents

Abstract

The present invention relates to bismuth (Bi) in an amount of 2.0 to 8.0% by weight; 0.5 to 6.5% by weight of aluminum (Al); Magnesium (Mg) balance; And it relates to a magnesium alloy extruded material containing unavoidable impurities, wherein the magnesium alloy extruded material according to the present invention further includes aluminum (Al) in the Mg-Bi binary alloy, thereby promoting dynamic recrystallization during extrusion to obtain uniform and fine grains. It has fine secondary phase (Mg ₃ Bi ₂ ) particles that are precipitated during extrusion together with the configured microstructure, and shows significantly improved strength and elongation compared to conventional magnesium extrusion materials without containing rare earth metals.

Description

High physical properties magnesium alloy processing material and manufacturing method thereof

The present invention relates to a magnesium alloy processed material and a method for manufacturing the same, and more particularly, to a magnesium alloy processed material with high physical properties and a method for manufacturing the same, which overcomes low mechanical properties, which is a disadvantage of conventional commercial magnesium extrusion materials, without including expensive rare earth metals. is about

As international environmental regulations become increasingly stringent, lightweight vehicles with low carbon dioxide emissions and excellent fuel efficiency have become a major focus of the automobile industry.

Accordingly, magnesium-based magnesium (Mg: 1.738 g/cm 3 , Fe: 7.874 g/cm 3 , Ti: 4.506 g/cm 3 and Al: 2.70 g/cm 3 ) has a significantly lower density compared to other structural material metals. Alloys are attracting considerable interest in the industry as a material for reducing the weight of automobiles.

On the other hand, existing research on magnesium alloys has focused on magnesium alloys for casting to be applied to automobile engines and gear parts based on the excellent castability of magnesium, but magnesium alloy castings have better mechanical properties as they have casting defects. In order to obtain this, studies on magnesium alloy processed materials obtained through plastic working processes such as extrusion, rolling, and forging are being actively conducted.

In particular, magnesium alloy extruded materials exhibit superior mechanical properties compared to cast materials, making them suitable for use in automobile body and chassis components such as bumper beams, radiator supports, engine cradles and subframes.

However, the low strength and high price of the magnesium alloy extruded material compared to the aluminum alloy extruded material is still a major obstacle to the wide application of the magnesium alloy extruded material in the automobile industry and the like.

Korean Patent Registration No. 10-0994812 (Registration Date: 2010.11.10) Korean Patent Publication No. 10-2012-0095184 (published on August 28, 2012)

The technical problem to be solved by the present invention is significantly improved mechanical properties compared to the conventional magnesium extruded material, which has difficulty in expanding industrial applications due to conventional low mechanical properties (strength, elongation) without including expensive rare earth elements as alloy elements It is to provide a novel magnesium alloy having a and a method for manufacturing the same.

In order to achieve the technical problem as described above, the present invention provides 2.0 to 8.0 wt% of bismuth (Bi); 0.5 to 6.5% by weight of aluminum (Al); Magnesium (Mg) balance; And it provides a magnesium alloy extruded material containing unavoidable impurities.

The magnesium alloy extruded material is characterized in that it does not contain a rare-earth metal as an alloying element.

In addition, the magnesium alloy extruded material is characterized in that it comprises Mg ₃ Bi ₂ precipitated particles as a secondary phase (second phase).

In addition, the magnesium alloy extruded material is 3.0 to 7.0% by weight of bismuth (Bi); 2.0 to 6.0% by weight of aluminum (Al); Magnesium (Mg) balance; and unavoidable impurities, wherein the ultimate tensile strength (UTS) × elongation value is 4000 MPa·% or more.

In addition, the magnesium alloy extruded material is 5.0% by weight of bismuth (Bi); 6.0% by weight of aluminum (Al); Magnesium (Mg) balance; and unavoidable impurities, wherein the ultimate tensile strength (UTS) × elongation value is 5792 MPa·%.

And, in another aspect of the present invention, as a method for manufacturing the magnesium alloy extruded material, (a) 2.0 to 8.0 wt% of bismuth (Bi); 0.5 to 6.5% by weight of aluminum (Al); Magnesium (Mg) balance; and manufacturing a magnesium alloy billet by casting a molten magnesium alloy containing unavoidable impurities; (b) homogenizing heat treatment and cooling the magnesium alloy billet prepared in step (a); And (c) extruding the homogenized heat-treated magnesium alloy billet in step (b); provides a method of manufacturing a magnesium alloy extruded material comprising a.

In this case, in step (a), 2.0 to 8.0 wt% of bismuth (Bi); 0.5 to 6.5% by weight of aluminum (Al); Magnesium (Mg) balance; and maintaining a molten magnesium alloy containing unavoidable impurities at 670 to 770 ^o C for 20 minutes and then casting to prepare a magnesium alloy billet.

In addition, in step (b), the magnesium alloy billet is subjected to a homogenization heat treatment at 350 to 550 ^o C for 0.5 to 72 hours, followed by water cooling.

In addition, it is characterized in that the extruded after preheating the billet homogenized heat treatment in step (c) at 200 ~ 450 ^o C.

The magnesium alloy extruded material according to the present invention further includes aluminum (Al) in the Mg _- Bi binary alloy, thereby promoting dynamic recrystallization during extrusion. ₂ ) By having particles, it exhibits significantly improved strength and elongation compared to conventional magnesium extruded materials without including rare earth metals.

1 is a result of measuring the change in the dynamic recrystallization (dynamic recrystallization, DRX) fraction in the surface portion, 1/4 portion, and the center of the magnesium alloy extruded material prepared in Comparative Examples 2, 5 and 8, respectively.
2 is an electron backscatter diffraction (electron backscatter diffraction) in the surface portion (S), 1/4 portion (Q) and the center (C) of the magnesium alloy extruded material prepared in Comparative Example 2, Example 5 and Example 8, respectively. This is an inverse pole figure map measured by the ) method ( d _DRX : average grain size of dynamically recrystallized grains, d _unDRX : average grain size of non-dynamic recrystallized grains).
3 is a scanning electron microscope (SEM) photograph of the central portion (C) of the magnesium alloy extruded material prepared in Examples 5 and 8, respectively.
4 is a tensile stress-strain graph of the magnesium alloy extruded material prepared in Comparative Example 2, Example 5, and Example 8, respectively.

In describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

Since the embodiment according to the concept of the present invention can have various changes and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the present specification or application. However, this is not intended to limit the embodiment according to the concept of the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, or substitutes included in the spirit and scope of the present invention.

The terminology used herein is used only to describe specific embodiments, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as “comprise” or “have” are intended to designate that the described feature, number, step, operation, component, part, or a combination thereof exists, and includes one or more other features or numbers. , it is to be understood that it does not preclude the possibility of the existence or addition of steps, operations, components, parts, or combinations thereof.

Hereinafter, the present invention will be described in detail.

The magnesium alloy extruded material according to the present invention includes 2.0 to 8.0 wt% of bismuth (Bi); 0.5 to 6.5% by weight of aluminum (Al); Magnesium (Mg) balance; And it is manufactured by extruding a magnesium alloy containing unavoidable impurities.

The reason for limiting the alloy composition as described above in the magnesium alloy extruded material according to the present invention is as follows.

Bismuth (Bi)

Bismuth (Bi) may be added to the magnesium alloy to have favorable conditions for high-temperature extrusion and precipitation strengthening. The maximum solid solution limit of Bi is as high as 9% at 551 ℃, and the melting point of the secondary phase Mg ₃ Bi ₂ formed by adding Bi is 823 ℃. can be improved

When the content of bismuth contained in the magnesium alloy extruded material according to the present invention is less than 2.0 wt%, the precipitation strengthening effect cannot be effectively exhibited after extrusion due to the lack of dissolved Bi solute atoms, so the strength of the final extruded material is low and exceeds 8.0 wt% In this case, the coarse Mg ₃ Bi ₂ dispersed phase remaining after the homogenization heat treatment remains in the final extruded material, which is not preferable because it may cause premature failure during the tensile test.

Accordingly, the magnesium alloy extruded material according to the present invention preferably includes Bi in an amount of 2.0 to 8.0 wt%.

Aluminum (Al)

Aluminum (Al) is an element added to the Mg-Bi alloy to improve the physical properties of the magnesium alloy.

When the content of aluminum contained in the magnesium alloy extruded material according to the present invention is less than 0.5% by weight, the amount is not sufficient to promote dynamic recrystallization, so the size of the grains after extrusion is not uniform and the strength and ductility increase due to coarse initial grains It is difficult to expect the effect. On the other hand, when it exceeds 6.5 wt%, the coarse Mg ₁₇ Al ₁₂ phase formed during the solidification process during casting is not completely dissolved during homogenization heat treatment and is present in the final material after extrusion. It can be a cause and is not recommended.

Accordingly, the magnesium alloy extruded material according to the present invention preferably contains Al in the range of 0.5 to 6.5 wt%.

Other unavoidable impurities

The magnesium extruded material according to the present invention may contain impurities that are unavoidably mixed in the raw material of the alloy or in the manufacturing process, and among these impurities, Fe, Cu and Ni are components that play a role in worsening the corrosion resistance of the magnesium alloy. Accordingly, it is preferable to maintain the Fe content of 0.004 wt% or less, the Cu content of 0.005 wt% or less, and the Ni content of 0.001 wt% or less.

Furthermore, the magnesium extruded material according to the present invention may further include one or more alloying elements as necessary in addition to the aforementioned Bi and Al, and such additional alloying elements are typically tin (Sn) and zinc (Zn) as follows. , manganese (Mn), calcium (Ca), and the like, but is not necessarily limited thereto.

Tin (Sn)

Tin (Sn) exhibits an aging strengthening behavior by forming a fine Mg ₂ Sn precipitation phase through heat treatment when the maximum amount of tin (Sn) in the magnesium group is 14.5 wt % at 561 ° C., and when 1.0 wt % or more is added.

When Sn is added to the magnesium alloy in an amount of less than 1.0% by weight, precipitation strengthening phenomenon cannot be expected, and when added in excess of 3.0% by weight, the fraction of the coarse Mg ₂ Sn phase formed during casting is excessive, It is difficult to sufficiently remove, and even after processing heat treatment, a significant amount of these coarse particles are present in the tissue, which may lead to deterioration of mechanical properties.

Therefore, when the magnesium alloy extruded material according to the present invention includes Sn, it is preferably included in the range of 1.0 to 3.0 wt%.

Zinc (Zn)

Like aluminum, zinc (Zn) plays a role in increasing the strength of magnesium alloys through solid solution strengthening and precipitation strengthening.

When zinc is added in an amount of less than 0.1% by weight, an effect of increasing strength cannot be expected, and when zinc is added in an amount exceeding 3.5% by weight, microgalvanic corrosion may be promoted, and the corrosion resistance of the extruded material may be reduced.

Therefore, when the magnesium alloy extruded material according to the present invention contains Zn, it is preferably included in the range of 0.1 to 3.5 wt%.

Manganese (Mn)

Manganese (Mn) not only strengthens the solid solution but also forms various dispersed particles by combining with aluminum (Al), thereby contributing to an increase in the strength of the alloy and improving the corrosion resistance of the alloy.

When manganese (Mn) is added to the magnesium alloy in an amount of less than 0.05 wt%, it is difficult to expect this effect. This results in deterioration of the mechanical properties of the alloy.

Therefore, when the magnesium alloy extruded material according to the present invention contains Mn, it is preferably included in the range of 0.0 5 to 1.5 wt %.

Calcium (Ca)

Calcium (Ca) forms a Mg-Al-Ca intermetallic compound in the magnesium alloy containing aluminum to improve strength and heat resistance, and forms a thin and dense CaO oxide layer on the surface of the molten metal to inhibit oxidation of the magnesium alloy. improve the fire resistance of

When calcium is added in an amount of less than 0.05% by weight, the effect of improving the ignition resistance is not great, and when it exceeds 2.0% by weight, the castability of the molten metal is deteriorated, hot cracking occurs, and the die sticking with the mold is reduced. As it increases, there is a problem such as a large decrease in elongation, and in the case of an extrusion process, there is a problem in that the extrusion load is greatly increased and surface cracks occur.

Therefore, when the magnesium alloy extruded material according to the present invention contains Ca, it is preferably included in the range of 0.05 to 2.0 wt%.

In order to prepare the extruded material of high physical properties magnesium alloy as described above, in the present invention, (a) 2.0 to 8.0 wt% of bismuth (Bi); 0.5 to 6.5% by weight of aluminum (Al); Magnesium (Mg) balance; and casting a molten magnesium alloy containing unavoidable impurities to prepare a magnesium alloy billet; (b) homogenizing heat treatment and cooling the magnesium alloy billet prepared in step (a); and (c) extruding the magnesium alloy billet that has been homogenized and heat treated in step (b).

In step (a), 2.0 to 8.0 wt% of bismuth (Bi); 0.5 to 6.5% by weight of aluminum (Al); Magnesium (Mg) balance; And after preparing a molten metal containing unavoidable impurities, the billet may be cast by injecting it into a preheated metal mold.

In the casting process in this step, it is preferable to cast the magnesium alloy molten metal after maintaining it at 670 to 770 ^o C for 20 minutes. When the magnesium alloy molten metal is cast at less than 670 °C, there is a problem in that the fluidity of the molten magnesium alloy is low and casting is difficult. In addition, when the molten magnesium alloy is cast at a temperature exceeding 770° C., the molten magnesium alloy is rapidly oxidized and impurities may be mixed during casting, thereby reducing the purity of the magnesium alloy billet manufactured therefrom.

In addition, the molten magnesium alloy may be prepared by melting the raw material of the magnesium alloy, and the method for preparing the molten magnesium alloy is not limited thereto, as long as it is a method commonly used in the art. For example, gravity casting, continuous casting , sand casting or pressure casting can be used.

Next, the step (b) is a step of homogenizing and heat treating the manufactured magnesium alloy billet and then cooling it. , it is possible to improve the high-temperature workability and mechanical properties of the magnesium alloy by forming equiaxed a-Mg particles.

The range of the homogenization treatment temperature can be appropriately selected by those skilled in the art according to the types of constituent elements constituting the magnesium alloy billet, and the homogenization treatment of the magnesium alloy billet is preferably carried out at 350 to 550 ° C. If the homogenization treatment temperature is less than 350 ℃, the temperature is low, so that the homogenization of alloy element segregation and solid solution into the matrix of the secondary phase formed during solidification is not sufficiently achieved. There is a problem in that the dissolution of phosphorus may occur and the physical properties may be deteriorated.

In addition, if the homogenization treatment time is less than 0.5 hours, the diffusion of the alloying elements of the magnesium alloy billet does not occur sufficiently, so the effect of the homogenization treatment may not appear. It is not economical because the rise is not large.

In addition, in order to make the microstructure of the magnesium alloy billet into a super-solid solution state through the homogenization treatment, it is preferable to rapidly cool the magnesium alloy billet through water cooling or the like.

Finally, in step (c), the homogenization heat treatment is a step of extruding the magnesium alloy billet and processing it into an extruded material.

For example, a magnesium alloy extruded material can be manufactured by directly extruding or indirectly extruding a magnesium alloy. It is preferable to extrude after preheating to a temperature for 0.5 to 2 hours.

Hereinafter, the present invention will be described in more detail by way of examples.

Embodiments according to the present specification may be modified in various other forms, and the scope of the present specification is not to be construed as being limited to the embodiments described below. The embodiments of the present specification are provided to more completely explain the present specification to those of ordinary skill in the art.

<Examples 1 to 10>

In order to prepare a magnesium alloy extruded material according to the present invention, magnesium alloy casting billets having the composition shown in Table 1 below were prepared as follows. In the manufacturing process of the billet for extrusion, a pure Mg ingot with a purity of 99.99% is dissolved in a carbon crucible in a mixed gas atmosphere of CO ₂ and SF ₆ , bismuth and aluminum are added, and then maintained at 720 ° C. for 20 minutes for stabilization, and the molten metal After sufficiently stirring to make the mixture uniform, it was tapped into a steel mold preheated to 210 °C. The chemical composition of the cast alloy was measured with an inductively coupled plasma spectrometer (PerkinElmer, Optima 7300DV).

Next, the cast billet was subjected to homogenization heat treatment in an inert gas atmosphere using an electric furnace at 410 ° C. for 24 hours, and then cooled with water to prevent static precipitation of Bi and Al dissolved in the magnesium matrix during cooling.

After processing the homogenized heat-treated billet to a diameter of 68 mm and a length of 120 mm, it was preheated at 350 ° C. for 1 hour, and then directly extruded at a ram speed of 1 mm / s and an extrusion ratio of 10 to have a diameter of 21.5 mm. An extruded bar was prepared.

<Table 1>

<Comparative Examples 1 to 5>

A magnesium alloy extruded material was prepared in the same manner as in Examples 1 to 10, except for having the alloy composition shown in Table 2 below.

<Table 2>

<Experimental example>

The microstructure properties of the extruded material were analyzed using FE-SEM equipped with an electron backscatter diffraction (EBSD) detector.

In order to quantitatively analyze the change in the dynamic recrystallization (DRX) fraction according to the change in the aluminum (Al) content, the area fraction of unrecrystallized grains in the surface part, 1/4 part, and central region of the longitudinal section of the extruded material was measured. In the optical micrograph of the area, it was measured for a relatively large area of 18.8 mm ² .

The EBSD experiment was performed in an alloy prepared in Comparative Example 2 (B5), an alloy prepared in Example 5 (BA53) and an alloy (BA56) prepared in Example 8 with a step size of 0.9 μm in a 2.02 mm ² area for the longitudinal section, It was performed using TexSEM Laboratories (TSL) data acquisition software under the condition of confidence index > 0.1.

1 shows the recrystallization fractions in the surface portion (S), 1/4 portion (Q) and the center portion (C) of the magnesium alloy extruded material prepared in Comparative Examples 2, 5 and 8, respectively, as a function of the Al content. showed

The higher the Al content in all parts, the more the recrystallization fraction increases, and the increase is more pronounced in the central part (69.3-100%) than in the surface part (90.3-100%).

In general, the effective strain applied to the material during extrusion is higher at the surface than at the center because the surface portion experiences more metal flow than the center portion during extrusion. Also, the deformation temperature is higher at the surface part due to the friction between the billet and the container wall. Therefore, a larger effective strain and strain temperature promotes recrystallization during hot extrusion, so that the surface portion of the extruded material exhibits a higher recrystallization fraction.

In the extruded material (B5) prepared in Comparative Example 2, the average recrystallization fraction calculated based on the recrystallization fraction of each part is relatively low (80.3%), and the difference in the recrystallization fraction between the surface part and the center part is relatively high (21.0%) It was found that the microstructure non-uniformity of the extruded material was high (FIG. 1). However, when Al is added to the Mg-Bi binary alloy, the recrystallization fraction is increased throughout the extruded material and the uniformity of the microstructure is also greatly improved. As the Al content increased from 0 wt% to 6 wt%, the average recrystallization fraction increased from 80.3% to 99.4%, and the difference in the DRX fraction greatly decreased from 21.0% to 1.4%, so that the uniformity of the microstructure of the extruded material was the corresponding Al It significantly increases within the content range.

Since the alloy (BA56) prepared in Example 8 already has an almost completely recrystallized microstructure, there is little change in the microstructure when the Al content is increased from 6 wt% to 9 wt%.

From the above results, it can be seen that adding Al to the Mg-Bi binary alloy effectively promotes the recrystallization behavior during extrusion, thereby obtaining an extruded Mg-Bi-Al alloy having a uniform grain structure.

The effect of Al addition on the grain size in the microstructure of the extruded material was obtained from the inverse pole figure map of the surface portion (S), the quarter portion (Q) and the center portion (C) of the longitudinal section of the extruded material. was used for analysis (FIG. 2).

The average size of non-dynamically recrystallized grains (48.3 ~ 89.1 μm) is much larger than that of dynamically recrystallized grains (4.9 ~ 13.7 μm), and since the effective strain in the surface portion is larger, the size of the unrecrystallized grains in the surface portion is larger in the central portion. smaller than the unrecrystallized grain size of In addition, as the Al content increased from 0 wt% to 6 wt%, the size of unrecrystallized grains in the center decreased from 89.1 μm to 68.6 μm due to the promotion of dynamic recrystallization.

In addition, in the case of Comparative Example 2, which is a binary Mg-Bi system, a large number of coarse non-recrystallized crystal grains exist, and the difference in structure between the surface portion (S) and the center portion (C) of the extruded material is large. On the other hand, in the case of Examples 5 and 8, which are Mg-Bi-Al alloy extruded materials according to the present invention, the amount of unrecrystallized grains is small and the structure is uniform throughout. Therefore, when Al is added to the Mg-Bi binary alloy, recrystallization during extrusion is promoted, so that the average grain size of the extruded material is reduced and a finer and more uniform structure can be obtained.

The finer grain size improves the strength of the extruded material by increasing the grain boundary reinforcing effect during tensile deformation, and the reduction of the coarse unre-settled grain fraction suppresses the formation of microcracks during tensile deformation, thereby improving the ductility of the extruded material.

3 shows an SEM photograph of the extruded center of the alloy (BA53) prepared in Example 5 and the alloy (BA56) prepared in Example 8. A small amount of undissolved Mg ₃ Bi ₂ particles rearranged along the extrusion direction (ED) were observed in both extrudates. In addition, as dynamic precipitates formed during extrusion, very fine and uniformly distributed Mg ₃ Bi ₂ precipitates with a size of 100 to 200 nm exist in both extruded materials, and the size and number thereof are confirmed to be similar regardless of the Al content. The fine precipitates uniformly formed throughout these materials effectively hinder the movement of dislocations during tensile deformation to cause a precipitation strengthening effect, thereby increasing the strength of the extruded material.

In order to analyze the mechanical properties of the magnesium alloy extruded material, a tensile test specimen having a gauge diameter of 6 mm and a gauge length of 25 mm obtained by processing the magnesium alloy extrusion material was used with an Instron 8516 tester to measure 1 x 10 ^-3 s ^-1 at room temperature. A tensile test was performed at a rate of strain, and the results are shown in Tables 1, 2 and 4 above.

As can be seen from the mechanical properties measurement results shown in Tables 1 and 2, the tensile strength * elongation of the Mg-Bi binary extruded materials of Comparative Examples 1 to 5 were 1197 MPa·% or less, whereas Examples 1 to 10 of Mg-Bi-Al ternary extruded material has excellent physical properties of 2228 MPa·% or more.

In particular, it was found that the Mg-Bi-Al ternary extruded materials of Examples 2, 4-8, and 10 containing 2 wt % or more of Al had very excellent mechanical properties with tensile strength * elongation of 4000 MPa·% or more.

As mentioned above, although embodiments of the present invention have been described with reference to the accompanying drawings, those of ordinary skill in the art to which the present invention pertains can practice the present invention in other specific forms without changing its technical spirit or essential features. You can understand that there is Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (9)

5.0% by weight of bismuth (Bi);
6.0% by weight of aluminum (Al);
Magnesium (Mg) balance; and unavoidable impurities,
A magnesium alloy extruded material, characterized in that the ultimate tensile strength (UTS) × elongation value is 5792 MPa·%. According to claim 1,
A magnesium alloy extruded material, characterized in that it does not contain a rare-earth metal as an alloying element. According to claim 1,
Magnesium alloy extruded material, characterized in that it comprises Mg ₃ Bi ₂ precipitated particles as a secondary phase (second phase). delete delete (a) 5.0% by weight of bismuth (Bi); 6.0% by weight of aluminum (Al); Magnesium (Mg) balance; and manufacturing a magnesium alloy billet by casting a molten magnesium alloy containing unavoidable impurities;
(b) homogenizing heat treatment and cooling the magnesium alloy billet prepared in step (a); and
(c) extruding the homogenized heat-treated magnesium alloy billet in step (b); 7. The method of claim 6,
5.0% by weight of bismuth (Bi) in step (a); 6.0% by weight of aluminum (Al); Magnesium (Mg) balance; and maintaining a molten magnesium alloy containing unavoidable impurities at 670 to 770 ^o C for 20 minutes and then casting the magnesium alloy billet. 7. The method of claim 6,
Method for producing a magnesium alloy extruded material, characterized in that the magnesium alloy billet in step (b) is subjected to a homogenization heat treatment at 350 to 550 ^o C for 0.5 to 72 hours, followed by water cooling. 7. The method of claim 6,
Method for producing a magnesium alloy extruded material, characterized in that the extruded after preheating the billet homogenized heat treatment in step (c) at 200 ~ 450 ^o C.

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