WO2018117713A1 - High strength magnesium alloy with excellent flame retardancy, and method for producing same - Google Patents

Abstract

An aspect of the present invention relates to a high strength magnesium alloy with excellent flame retardancy, wherein the magnesium alloy comprises 2.0-13.0 wt% of Al, 0.1-0.5 wt% of Mn, 0.0015-0.025 wt% of B, and 0.1-1.0 wt% of Y with the remainder comprising Mg and other unavoidable impurities, and comprises 6.5% or more of an Mg-Al intermetallic compound in terms of volume fraction, the Mg-Al intermetallic compound having an average grain size of 20-500 nm.

Description

High strength magnesium alloy with excellent flame retardancy and its manufacturing method

The present invention relates to a high strength magnesium alloy excellent in flame retardancy and a method of manufacturing the same.

Magnesium is one of the lightest metals in practical metals, so it can be applied as a structural material for portable electronic products such as smartphones, tablet PCs, and laptops, as well as for transportation of automobiles, trains, aircrafts, etc. Is spotlighted as an eco-friendly lightweight metal material.

Magnesium alloys are excellent in castability, so cast products manufactured through mold casting methods such as high pressure casting, low pressure casting and gravity casting have been mainly applied to practical products, and recently, they have been manufactured through processing processes such as rolling or extrusion. The development of products for the whole body materials and market expansion are also being promoted.

In general, the alloying elements added to the casting magnesium alloy and the magnesium alloy for the whole material are similar, and the most commonly used magnesium alloys are AZ-based alloys containing Al and Zn or AM containing Al and Mn. A system alloy is mentioned. The two kinds of alloys commonly contain Al, in order to improve the castability and tensile strength of magnesium.

AZ and AM-based magnesium alloys, which occupy most of commercial magnesium alloys, are suitable for manufacturing various mold casting products by improving the flowability of molten metal by Al addition, and also have advantages in billet casting and sheet casting for whole body materials. However, yield strength or tensile strength is significantly lower than that of competing aluminum alloys, so there is a problem in that the thickness of the product or the product shape should be modified and applied.

In addition, magnesium alloy has a problem that the use conditions are limited because of the high possibility of ignition due to high oxygen affinity.

Therefore, there is a demand for development of a high strength magnesium alloy having excellent flame retardancy and a method of manufacturing the same.

(Prior art document)

(Patent Document 1) Korean Unexamined Patent Publication No. 10-2015-0077494

One aspect of the present invention is to provide a high-strength magnesium alloy excellent in flame retardancy and a method of manufacturing the same.

In addition, the subject of this invention is not limited to the content mentioned above. The problem of the present invention will be understood from the general contents of the present specification, those skilled in the art will have no difficulty understanding the additional problem of the present invention.

One aspect of the present invention by weight, Al: 2.0 ~ 13.0%, Mn: 0.1 ~ 0.5%, B: 0.0015 ~ 0.025%, Y: 0.1 ~ 1.0%, the remaining Mg and inevitable impurities, Mg-Al It contains at least 6.5% by volume fraction of the intermetallic compound, the average particle diameter of the Mg-Al intermetallic compound relates to a high-strength magnesium alloy excellent in flame retardancy of 20 ~ 500nm.

In addition, another aspect of the present invention is by weight, Al: 2.0-13.0%, Mn: 0.1-0.5%, B: 0.0015-0.025%, Y: 0.1-1.0%, molten metal containing the remaining Mg and unavoidable impurities Preparing a;

Casting the molten metal to obtain a magnesium alloy cast material;

Obtaining a magnesium alloy by solution treatment of the magnesium alloy casting material in a temperature range of 370 to 490 ° C. for 2 to 20 hours;

Cooling the magnesium alloy to 100 ° C. or less; And

It relates to a method of producing a high-strength magnesium alloy having excellent flame retardancy comprising; aging treatment of the cooled magnesium alloy for 2 to 48 hours at 150 ~ 250 ℃.

In addition, the solution of the said subject does not enumerate all the characteristics of this invention. Various features of the present invention and the advantages and effects thereof can be understood in more detail with reference to the following specific embodiments.

According to the present invention, there is an effect that can provide a high-strength magnesium alloy excellent in flame retardancy and a method for producing the same.

1 is a photograph of the microstructure of the magnesium alloy cast material of Comparative Material 1 (a) and Inventive Material 7 (b).

Figure 2 is a microstructure photograph after completion of the solution treatment of Comparative Material 1.

Figure 3 is a microstructure photograph after the solution treatment of Inventive Material 7.

Figure 4 is a graph showing the results of measuring the hardness value according to the aging time for Comparative Material 1 (a) and Inventive Material 7 (b) at 200 ℃.

5 is a photograph observing the microstructure of the magnesium alloy after the aging treatment of Comparative Material 1 (a), Invention Material 7 (b), and Comparative Material 5 (c).

6 is a graph showing the change in hardness value and the size of Mg-Al intermetallic compound in the grains with respect to the aging time of the invention material 7.

7 is a graph showing the volume fraction of the Mg-Al intermetallic compound according to the aging time of the invention material 7.

Hereinafter, preferred embodiments of the present invention will be described. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

The present inventors have studied in depth to solve the problems of the ignition characteristics and low strength of magnesium alloys, it is possible to finely distribute a large amount of intermetallic compound by complex addition of B and Y and aging treatment, accordingly It was confirmed that the flame retardancy and high strength can be secured and came to complete the present invention.

High strength magnesium alloy with excellent flame retardancy

Hereinafter, a high strength magnesium alloy excellent in flame retardancy according to an aspect of the present invention will be described in detail.

High-strength magnesium alloy having excellent flame retardancy according to an aspect of the present invention is by weight%, Al: 2.0 ~ 13.0%, Mn: 0.1 ~ 0.5%, B: 0.0015 ~ 0.025%, Y: 0.1 ~ 1.0%, the remaining Mg and inevitable Impurities, containing at least 6.5% Mg-Al intermetallic compound by volume fraction, the average particle diameter of the Mg-Al intermetallic compound is 20 ~ 500nm.

First, the alloy composition of the present invention will be described in detail. The unit of each element content hereafter means weight% unless there is particular notice.

Al: 2.0 ~ 13.0%

Al is an element that increases tensile strength or yield strength and improves castability by improving flowability of the molten alloy.

If the Al content is less than 2.0%, the above effects are insufficient. On the other hand, when the Al content is more than 13.0% can increase the brittleness can reduce the workability and ductility. Therefore, the Al content is preferably 2.0 to 13.0%.

In addition, the lower limit of Al content may be 2.5%, and the lower limit may be 6.5% to secure a tensile strength of 160 MPa or more. A more preferable upper limit of the Al content may be 12.0%, and a more preferable upper limit may be 11.0%.

Mn: 0.1 ~ 0.5%

Mn is an element that contributes to an increase in tensile strength by making grains fine by forming an intermetallic compound with Al. In addition, through the formation of intermetallic compounds it lowers the corrosion rate of magnesium by lowering the Fe, a representative impurity element unnecessary for magnesium alloy.

If the Mn content is less than 0.1%, the above effects are insufficient. On the other hand, when the Mn content is more than 0.5%, brittleness may be caused by excessive formation of acicular intermetallic compounds. Therefore, the Mn content is preferably 0.1 to 0.5%.

In addition, the lower limit of the Mn content may be 0.11%, and the upper limit may be 0.45%.

B: 0.0015-0.025%

B (boron) is known to be a rare element in magnesium alloys because it has a very high melting point, and its solubility in a solid or liquid magnesium is almost zero.

However, in the present invention, it is added to ensure flame retardancy and high strength, and in particular, by adding B and Y to a magnesium alloy and performing aging treatment, it contributes to the formation of a large amount of Mg-Al intermetallic compound to improve tensile strength. In addition, flame retardancy and strength can be further improved than when B is added alone. In addition, it can contribute to preventing the oxidation of the molten metal can reduce the use of expensive SF ₆ gas or SO ₂ gas that can cause environmental pollution can be reduced production costs and environmental protection.

When the B content is less than 0.0015%, the above effects are insufficient. On the other hand, when the B content is greater than 0.025%, there is a problem in that the Al-B compound is formed at the grain boundary to reduce ductility. Therefore, it is preferable that B content is 0.0015 to 0.025%.

In addition, the lower limit of the B content may be more preferably 0.002%, and more preferably 0.02%.

Y: 0.1-1.0%

Y is an element that combines with Al to form a precipitate and contributes to the improvement of strength, and has a high oxygen affinity to strengthen the protective film on the surface of the molten metal to inhibit oxidation of the molten metal and to improve flame retardancy even after solidification.

In addition, by complex addition with B as described above and aging treatment, not only contributes to the formation of a large amount of Mg-Al intermetallic compound to improve the tensile strength, but also further improve the flame retardancy than when added alone.

If the Y content is less than 0.1%, the above effects are insufficient. On the other hand, when the Y content is more than 1.0%, there is a fear that ductility is reduced due to coarse Al-Y compound formation. Therefore, the Y content is preferably 0.1 to 1.0%.

Also, the lower limit of the Y content may be 0.11%, and the upper limit may be 0.95%.

The remaining component of the present invention is magnesium (Mg). However, in the conventional manufacturing process, impurities which are not intended from the raw material or the surrounding environment may be inevitably mixed, and thus cannot be excluded. Since these impurities are known to those skilled in the art, all of them are not specifically mentioned in the present specification. For example, there may be Fe, Cu, Ni, Ca, Na, Ba, F, S, N and the like.

In this case, in addition to the alloy composition described above, Zn: 0.3 to 3.0% by weight% may be further included.

Zn: 0.3 ~ 3.0%

Zn is a solid solution strengthening element, and promotes the formation of Mg ₁₇ Al ₁₂ phase, or is an element to improve the tensile strength by forming a separate intermetallic compound containing Zn, such as Mg ₂ Zn.

If the Zn content is less than 0.3%, the above effects are insufficient. On the other hand, when the Zn content is more than 3.0%, a large amount of separate intermetallic compounds containing Zn such as Mg ₂ Zn may be formed to increase brittleness, which may result in a decrease in ductility or toughness.

Therefore, it is preferable that Zn content is 0.3 to 3.0%. In consideration of the improvement of strength and the reduction of brittleness, a more preferable range is 0.5 to 1.5% by weight.

The high-strength magnesium alloy excellent in flame retardancy according to an aspect of the present invention not only satisfies the alloy composition described above, but also contains Mg-Al intermetallic compound in a volume fraction of 6.5% or more, and the average particle diameter of the Mg-Al intermetallic compound is 20 ˜500 nm.

Mg-Al intermetallic compound may be formed when the main alloying element added to magnesium is Al, and a representative Mg-Al intermetallic compound is Mg ₁₇ Al ₁₂ phase. Mg-Al intermetallic compound plays a role of ensuring high strength.

Since the maximum amount of Al or other alloying elements added to the magnesium alloy is less than the maximum high capacity of each alloying element with respect to Mg, Mg-Al metal is used because most Al is dissolved in the Mg matrix rather than causing the formation of intermetallic compounds in the grains. The formation of the liver compound is not a general phenomenon, and it is difficult to form a large amount of Mg-Al intermetallic compound. In the present invention, a large amount of Mg-Al intermetallic compound can be secured by complex addition of B and Y and aging treatment.

If the volume fraction of the Mg-Al intermetallic compound is less than 6.5%, it is difficult to secure high strength. Therefore, the volume fraction of the Mg-Al intermetallic compound is preferably at least 6.5%, more preferably at least 7.0%, even more preferably at least 7.5%.

The upper limit of the volume fraction of the Mg-Al intermetallic compound does not need to be particularly limited. However, when the Mg-Al intermetallic compound is more than 30%, the Mg-Al intermetallic compound may have a coarse particle size and may increase brittleness. The volume fraction of may be 30% or less, more preferably 25% or less.

When the average particle diameter of the Mg-Al intermetallic compound is less than 20 nm, the fraction of the Mg-Al intermetallic compound is low, making it difficult to secure high strength, and when it exceeds 500 nm, brittleness is increased.

At this time, the Al-Mn intermetallic compound, Al-Y intermetallic compound further comprises one or more, the total may be 5% or less in volume fraction. If it is more than 5%, the Mn and Y content may be excessive and brittleness may increase.

At this time, the magnet alloy of the present invention may have a ignition temperature of 700 ℃ or more.

In addition, the magnetic alloy of the present invention may have a hardness of 70Hv or more.

In addition, the magnet alloy of the present invention may have a tensile strength of 130 MPa or more and an elongation of 3% or more. In addition, it is possible to secure the tensile strength of 160MPa or more by controlling the Al content and the like.

Manufacturing method of high strength magnesium alloy with excellent flame retardancy

Hereinafter, another aspect of the present invention will be described in detail a method for producing a high strength magnesium alloy excellent in flame retardancy.

Another aspect of the present invention is a method for producing a high-strength magnesium alloy having excellent flame retardancy, comprising: preparing a melt that satisfies the alloy composition described above; Casting the molten metal to obtain a magnesium alloy cast material; Obtaining a magnesium alloy by solution treatment of the magnesium alloy casting material in a temperature range of 370 to 490 ° C. for 2 to 20 hours; Cooling the magnesium alloy to 100 ° C. or less; And aging the cooled magnesium alloy for 2 to 48 hours at 150 to 250 ° C.

Melt Preparation Steps

A molten metal that satisfies the alloy composition described above is prepared. It does not need to specifically limit, According to the general preparation of the molten metal for magnesium alloys.

For example, the above-described alloying elements are prepared in accordance with the proposed composition range, and then charged into a melting crucible and then dissolved. Since the melting point of the magnesium alloy is relatively low, any method such as gas, electric furnace, induction melting furnace, etc. may be applied.

In preparing the alloying elements, each alloying element may be prepared in a pure form, but may be charged to the crucible in the form of a mother alloy in which Mn, B, and Y are mixed with Mg or Al. Since B, Y, and Mn have a high melting point, it is advantageous to dissolve it in the crucible in the form of a mother alloy mixed with Mg or Al.

In addition, when the prepared melting material is charged into the crucible, charging and carrying out the melting process in order from the element having the lowest melting point in turn may be advantageous.

Casting steps

The molten metal is cast to obtain a magnesium alloy cast material. The casting step need not be particularly limited as in the molten metal preparation step.

For example, the method of using a movable mold and the method of using a fixed mold can be used. Representative methods of using a movable mold include twin roll casting and belt casting using a movable mold such as twin roll or twin belt. In addition, a typical method using a stationary mold may be continuous casting or semi-continuous casting such as billet casting, and may also include mold casting such as high pressure casting, low pressure casting, and gravity casting.

Although the above various methods can be used as the casting process, it is advantageous to apply a casting method that can increase the cooling rate because boron or yttrium having a low solubility in magnesium is added together with aluminum. To this end, the mold must be cooled with cooling water, and when cooling water is applied, the mold surface must be kept above room temperature so that condensate can be removed from the mold surface before casting, and then the mold surface should be kept below room temperature after condensate is removed.

Solvent Treatment Step

The magnesium alloy casting material is subjected to a solution treatment for 2 to 20 hours at a temperature range of 370 to 490 ° C. to obtain a magnesium alloy. Mg-Al intermetallic compounds are also formed in magnesium alloy castings, but due to their coarse form (Coarse Mg-Al) or mixed with Mg matrix (Lamellar Mg-Al) To solute the compound.

If the solution temperature is less than 370 ℃ or the holding time is less than 2 hours, the total amount of Mg-Al intermetallic compound is difficult to be employed. If the solution temperature is higher than 490 ℃ or holding time is more than 20 hours, the production cost increases Productivity may drop, and oxidation may occur before B and Y are added. Therefore, more preferably, it can be carried out for 2 to 20 hours in the temperature range of 400 ~ 460 ℃.

Cooling stage

The magnesium alloy is cooled to 100 ° C. or less. This is to minimize the natural aging phenomenon that may appear before aging treatment.

At this time, the cooling rate may be 1 ~ 100 ℃ / sec. This is to minimize the natural aging phenomenon that can occur during cooling and to prevent the precipitated Al element from randomly precipitation. For example, it is preferable to cool rapidly by methods such as forced air blowing, water cooling, oil cooling, and the like.

Aging Process Steps

The cooled magnesium alloy is aged at 150 to 250 ° C. for 2 to 48 hours. In the microstructure of the magnesium alloy cooled after the solution treatment, since most Al elements added as alloy elements do not form a separate intermetallic compound in a solid solution of Mg matrix, the strength of the material cannot be efficiently increased. In the present invention, by aging treatment to precipitate a large amount of Mg-Al intermetallic compound to increase the strength, to ensure excellent flame retardancy. However, when B and Y are added in the range set forth in the present invention, a large amount of Mg-Al intermetallic compound can be precipitated through the above-described aging treatment.

In addition, since the precipitation by the aging treatment is a solid phase reaction proceeding in a solid phase, it is possible to form an Mg-Al intermetallic compound having a particle shape, an average particle diameter, a volume fraction, etc., which is advantageous for improving strength and flame retardancy.

If the aging treatment temperature is less than 150 ° C. or the holding time is less than 2 hours, it is difficult to sufficiently secure the Mg-Al intermetallic compound. On the other hand, when the aging treatment temperature is greater than 250 ° C. or the retention time is more than 48 hours, Mg-Al intermetallic compounds may be employed, and the production cost may increase and productivity may decrease. Therefore, it is preferable to aging for 2 to 48 hours at 150 ~ 250 ℃. More preferably, the temperature and the holding time may be increased within the temperature and the holding time according to the amount of Al added.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, it is necessary to note that the following examples are only for illustrating the present invention in more detail, and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the claims and the matters reasonably inferred therefrom.

(Example 1)

The molten metal having the component composition shown in Table 1 was cast to cast a magnesium alloy casting material having a thickness of 10 mm. The magnesium alloy casting material was solution treated at 420 ° C. for 4 hours, cooled to 20 ° C., and aged at 200 ° C. for 12 hours to prepare a magnesium alloy.

The Mg-Al intermetallic compound and mechanical properties of the magnesium alloy were measured and listed in Table 1 below. The size of the Mg-Al intermetallic compound measured the average size measured by the equivalent circular diameter.

Except for the alloying elements listed in Table 1, it was magnesium, and Mg-Al means Mg-Al intermetallic compound.

The ignition temperature measurement was confirmed as the temperature at which ignition occurred while raising the temperature inside the furnace body while leaving a sample of 10 g in the form of a chip in the furnace in an atmospheric atmosphere.

division	Alloy composition (% by weight)				Mg-Al		Mechanical properties			Ignition temperature ( o C)
	Al	Mn	B	Y	Size (nm)	Fraction (vol%)	TS (MPa)	El (%)	Hardness (Hv)
Comparative material 1	9	0.34	-	-	193	2.6	113	5.2	59	530
Comparative material 2	3	0.05	0.013	1.23	178	1.7	113	5.2	48	624
Comparative material 3	6	0.21	0.001	0.41	205	2.1	121	4.2	53	590
Comparative material 4	9	0.45	0.412	0.05	232	3.8	124	3.1	63	647
Comparative material 5	3	0.74	-	0.72	184	1.4	114	4.3	50	634
Comparative Material 6	6	0.12	0.003	1.21	212	2.4	123	3.4	56	660
Comparative material 7	9	0.33	-	0.21	228	3.1	125	3.2	61	612
Invention 1	2.8	0.12	0.018	0.92	134	7.5	135	5.8	71	721
Invention Material 2	2.7	0.32	0.012	0.63	128	8.1	138	6.2	72	712
Invention 3	3.1	0.44	0.006	0.31	133	8.7	142	6.1	74	718
Invention 4	3.4	0.42	0.003	0.13	129	9.8	144	5.7	78	715
Invention 5	5.6	0.12	0.017	0.12	153	13.3	151	4.6	84	747
Invention Material 6	6.2	0.3	0.012	0.54	161	14.4	155	5.8	87	733
Invention Material 7	6.2	0.4	0.006	0.81	154	14.7	158	4.7	88	742
Invention Material 8	5.8	0.42	0.002	0.88	139	13.8	152	4.4	85	739
Invention Material 9	8.5	0.12	0.013	0.14	176	19.1	164	3.5	103	783
Invention 10	10.6	0.3	0.003	0.51	184	21.6	167	4.6	107	776
Invention 11	9.8	0.4	0.009	0.94	179	20.3	172	4.2	106	782
Invention Material12	8.7	0.42	0.019	0.45	172	19.4	168	3.7	104	785

Inventive materials satisfying the alloy composition and manufacturing conditions presented in the present invention include Mg-Al intermetallic compound by more than 6.5% by volume fraction, and the average particle diameter of the Mg-Al intermetallic compound satisfies 20 ~ 500nm You can check it. In addition, the ignition temperature is more than 700 ℃ excellent flame retardancy, it can be seen that the mechanical properties are also superior to the comparative materials.

On the other hand, the comparative materials satisfy the manufacturing conditions presented in the present invention, but did not satisfy the alloy composition, it could be confirmed that the Mg-Al intermetallic compound was not sufficiently secured. In addition, the flame retardancy is inferior, and the mechanical properties can be confirmed that the heat is inferior to the invention materials.

(Example 2)

The change in manufacturing process of Comparative Material 1 and Inventive Material 7 of Table 1 was observed more closely.

1 is a photograph of the microstructure of the magnesium alloy cast material of Comparative Material 1 (a) and Inventive Material 7 (b). The casting structure of Comparative Material 1 was composed of Mg matrix and coarse Mg-Al intermetallic compound (Coarse Mg-Al), Mg matrix and Mg-Al intermetallic compound mixed structure (Lamellar Mg-Al), and Al-Mn intermetallic. In addition to the above structure, Al-Y intermetallic compound (Al-Y) was observed in the cast structure of Inventive Material 7, which is composed of a compound (Al-Mn), and yttrium and boron were added, and a boron-containing intermetallic compound was separately observed. It wasn't.

When the comparative material and the invention material having such a cast structure are solution treated, most Mg-Al intermetallic compounds except Al-Mn or Al-Y intermetallic compounds are employed as the matrix structure as shown in Figs. Will not be observed. The cast structure and the optical structure of the solution treatment material are almost similar except for the presence or absence of Al-Y intermetallic compound, but the aging treatment material shows a big difference.

This difference can be seen first in the hardness measurement results according to the aging time. As a result of measuring the hardness value according to the aging time for Comparative Material 1 (a) and Inventive Material 7 (b) at 200 ℃ as shown in Figure 4, it can be confirmed that the hardness of the invention material is significantly higher, and also the hardness of Comparative Material 1 Although the value is almost unchanged according to the aging time, it can be seen that the hardness value of the invention material increases greatly when the aging time exceeds 1 hour. In particular, after 3 hours, the maximum hardness value corresponding to peak aging is shown, and the hardness value shows 97 ~ 107Hv value which is 60% higher than the average hardness value of the cast material aged less than 1 hour. have. In addition, the maximum hardness value of the invention material 7 shows a value nearly twice the maximum hardness value of the comparative material.

5 is a photograph observing the microstructure of the magnesium alloy after the aging treatment of Comparative Material 1 (a), Invention Material 7 (b), and Comparative Material 5 (c). Inventive material 7 can confirm that a large amount of Mg-Al intermetallic compound having a size of several tens of nm is precipitated, and thus the hardness value of the inventive material is greatly increased.

FIG. 6 shows the change in hardness value (rhombus) and the size of Mg-Al intermetallic compound (square) in grains with respect to the aging time of Inventive Material 7, and FIG. 7 shows the Mg-Al intermetallic according to the aging time. The volume fraction of the compound is shown. As shown in FIGS. 6 and 7, when the inventive material 7 was aged for 3 hours or more, the average size and volume fraction of the Mg-Al intermetallic compound were grown to 20 nm or more and 10 vol% or more, respectively.

Although described with reference to the embodiments above, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

Claims (11)

1. By weight, Al: 2.0-13.0%, Mn: 0.1-0.5%, B: 0.0015-0.025%, Y: 0.1-1.0%, remaining Mg and inevitable impurities,

   Mg-Al intermetallic compound containing at least 6.5% by volume,

   The high-strength magnesium alloy having excellent flame retardancy of the average particle diameter of the Mg-Al intermetallic compound is 20 ~ 500nm.
2. The method of claim 1,

   The magnesium alloy is a weight percent, Zn: high strength magnesium alloy having excellent flame retardancy further comprises 0.5 to 1.5%.
3. The method of claim 1,

   The magnesium alloy further comprises at least one of Al-Mn intermetallic compound and Al-Y intermetallic compound, the sum of which is 5% or less by volume fraction, high strength magnesium alloy having excellent flame retardancy.
4. The method of claim 1,

   The magnesium alloy is a high-strength magnesium alloy excellent in flame retardancy of the ignition temperature 700 ℃ or more.
5. The method of claim 1,

   The magnesium alloy is a high strength magnesium alloy excellent in flame retardancy of 70Hv or more hardness.
6. The method of claim 1,

   The magnesium alloy is a high strength magnesium alloy excellent in flame retardancy of 130MPa or more tensile strength, 3% or more elongation.
7. Preparing a molten metal including Al: 2.0 to 13.0%, Mn: 0.1 to 0.5%, B: 0.0015 to 0.025%, Y: 0.1 to 1.0%, remaining Mg, and unavoidable impurities;

   Casting the molten metal to obtain a magnesium alloy cast material;

   Obtaining a magnesium alloy by solution treatment of the magnesium alloy casting material in a temperature range of 370 to 490 ° C. for 2 to 20 hours;

   Cooling the magnesium alloy to 100 ° C. or less; And

   Aging the cooled magnesium alloy for 2 to 48 hours at 150 ~ 250 ℃; manufacturing method of high strength magnesium alloy having excellent flame resistance.
8. The method of claim 7, wherein

   The molten metal by weight, Zn: a method of producing a high-strength magnesium alloy excellent flame retardancy further comprises 0.5 to 1.5%.
9. The method of claim 7, wherein

   The preparing of the molten metal is performed by charging a crucible in the form of a mother alloy in which Mn, B, and Y are mixed with Mg or Al.
10. The method of claim 7, wherein

    The step of preparing the molten metal is a method of producing a high-strength magnesium alloy having excellent flame retardancy, characterized in that the charging is carried out in the crucible in order from the element having a low melting point.
11. The method of claim 7, wherein

    The cooling step of producing a high-strength magnesium alloy having excellent flame retardancy, characterized in that performed at a cooling rate of 1 ~ 100 ℃ / second.

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