KR20160047447A - High strength magnesium alloy - Google Patents

Abstract

Provided are a high strength magnesium alloy, and a manufacturing method thereof. According to the present invention, the magnesium alloy comprises: 8.0-9.5 wt% of Al; 0.7-2.3 wt% of Zn; 0.5-3.0 wt% of at least one selected between Y and misch metal; and the remaining consisting of Mg. The magnesium alloy may additionally and selectively comprise 3.5-6.5 wt% of Sn. The magnesium alloy of the present invention has sufficient strength as an Mg-Al alloy comprises a large quantity of Al, and can mechanically be processed by extrusion or the like.

Description

High strength magnesium alloy < RTI ID = 0.0 >

The present invention relates to a high strength magnesium alloy usable as an extruded material and a method of manufacturing the same.

The magnesium alloy is an ultra-light alloy having a high specific strength and is excellent in mechanical properties and fluidity. Particularly, since magnesium alloy for casting can obtain high mechanical properties by precipitation hardening, it can be used in fields requiring automobile steel sheet or electromagnetic parts Can be widely used.

The magnesium alloy is mainly used in the form of a Mg-Al alloy containing a certain amount of Al. In the case of the Mg-Al alloy, the alloy produced in the molten alloy may be subjected to solution treatment or the solution-treated alloy may be aged ), And a precipitated phase is formed in most cases. In particular, when the Mg-Al alloy containing a certain amount of Al or more is subjected to the aging treatment after the solution treatment, the yield strength is greatly increased as compared with the case where only the solution treatment is performed

However, Mg-Al alloy containing a large amount of Al as above is mainly used as a casting material and has a disadvantage that it is difficult to use as an extruded material.

Accordingly, an object of the present invention is to provide a Mg-Al alloy containing a large amount of Al and a magnesium alloy capable of mechanical processing such as extrusion while having sufficient strength.

According to an aspect of the present invention, there is provided a magnesium alloy comprising:

At least one and at least one selected from the group consisting of Al, 8.0 to 9.5 wt% Al, 0.7 wt% to 2.3 wt% Zn, 0.5 wt% to 3.0 wt% Y and MishMetal.

In addition, the magnesium alloy according to the present invention preferably further comprises 3.5 to 6.5% by weight of Sn.

According to another aspect of the present invention, there is provided a method of manufacturing a magnesium alloy,

Forming a magnesium alloy melt containing Mg, Al, Sn and Zn;

Preparing a magnesium alloy casting material by using any magnesium alloy casting method;

And a step of solubilizing the magnesium alloy cast material,

The magnesium alloy formed by the casting magnesium alloy production method comprises at least one selected from 8.0 to 9.5 wt% Al, 0.7 wt% to 2.3 wt% Zn, 0.5 wt% to 3.0 wt% Y, And Mg as the remainder.

The method may further include the step of extruding the solution-treated magnesium alloy cast material.

Further, it is preferable that the above method further includes 3.5 to 6.5% by weight of Sn.

The reason for limiting the content of each component in the magnesium alloy according to the present invention is as follows.

Tin (Sn)

When Sn is added in an amount of 6.5 wt% or more, the coarse Mg ₂ Sn phase fraction formed during the solidification process is excessively excessive, which causes cracking during processing, resulting in deteriorated workability and a considerable amount of residual product in the final product. On the other hand, when it is added in an amount of less than 3.5% by weight, the precipitation strengthening phenomenon can hardly be expected, and the strength is lowered and the effect of inhibiting discontinuous precipitation of β-Mg ₁₇ Al ₁₂ phase can not be obtained. Therefore, the content of Sn in the present invention is preferably limited to 3.5 wt% to 6.5 wt%.

Aluminum (Al)

It is known that Al increases the precipitation strengthening effect by Mg ₂ Sn phase when added to a magnesium alloy containing Sn and contributes to increase the strength of the alloy through solid solution strengthening. In addition, an increase in the Al content in the magnesium alloy generally improves the fluidity and improves the casting, and at the same time increases the ignition resistance. However, when a small amount of aluminum is added, it is difficult to expect such an effect. If it is added in an amount exceeding 9.0 wt%, the thermal stability is poor and the coarse? -Mg ₁₇ Al ₁₂ process phase is excessively formed and the hot workability and tensile properties are deteriorated do. Therefore, Al is added in the range of 6.0 wt% to 9.5 wt% in the present invention.

Zinc (Zn)

It is known that when Zn is added to a magnesium alloy containing Sn, the Mg ₂ Sn phase, which is a high-temperature stable phase, is refined to increase the precipitation strengthening effect and contribute to increase the strength of the alloy through solid solution strengthening. If it is added in an amount of less than 0.7 wt%, it is difficult to expect such an effect. If it is added in an amount of more than 2.3 wt%, it becomes difficult to carry out homogenization heat treatment at a high temperature and the proportion of coarse Mg ₂ Sn phase in the tissue increases, Become vulnerable. Therefore, in the present invention, Zn is preferably added in the range of 0.7 wt% to 2.3 wt%.

Mesh metal (MM) and Y

In the present invention, Mishimetal is not particularly limited as long as it is a cerium rare earth element and is a kind of Mish Metal already known in the technical field of the present invention. Mishimetal or Y has a small amount of high capacity, which makes it possible to miniaturize the crystal grain at the high temperature with the AIRE phase and at the time of extrusion, and has excellent dispersion strengthening effect with respect to small crystal grains. It is difficult to expect such an effect when the amount of mish metal or Y is less than 0.5% by weight. When the amount exceeds 3.0% by weight, the crystal grains increase again. Therefore, in the present invention, 3.0% by weight.

The magnesium alloy according to the present invention has the above-described structure and can be used not only as a cast material but also as an extruded material when the Al content exceeds 6%, and has a higher strength than a conventional magnesium alloy containing Al.

1 is a SEM image and a TEM image of a magnesium alloy according to a first embodiment of the present invention.
2 is a SEM image and a TEM image of a magnesium alloy according to a third embodiment of the present invention.
3 is a SEM image and a TEM image of a magnesium alloy according to a fifth embodiment of the present invention.
4 is a SEM image and a TEM image of a magnesium alloy according to a sixth embodiment of the present invention.

A magnesium alloy according to a preferred embodiment of the present invention and a method of manufacturing the magnesium alloy will be described in detail below. However, the following examples are illustrative only and do not limit the invention.

Manufacture of Magnesium Alloys

The inventors of the present invention have solved the problems of the prior art described above and manufactured a magnesium alloy having various compositions in order to accomplish the object of the present invention. A method of manufacturing a magnesium alloy according to a preferred embodiment of the present invention is as follows.

number Mg Al Zn Sn MM Y Remarks Example 1 Remainder 9.0 1.0 0 One 0 AZ91-1MM Example 2 Remainder 9.0 1.0 0 2 0 AZ91-2MM Example 3 Remainder 9.0 1.0 5 One 0 AZT915-1MM Example 4 Remainder 9.0 1.0 5 2 0 AZT915-2MM Example 5 Remainder 9.0 1.0 0 0 One AZ91-1Y Example 6 Remainder 9.0 1.0 5 0 One AZT015-1Y Comparative Example 1 Remainder 9.0 1.0 0 0 0 AZ91 Comparative Example 2 Remainder 9.0 1.0 5 0 0 AZT915

(Unit: wt%)

First, raw materials of Mg (99.9%), Sn (99.99%), Al (99.9%) and Zn (99.99%) were prepared and melted in an electric furnace, respectively. To Example 6 and Comparative Example 1 and Comparative Example 2 were prepared. The magnesium alloy according to the preferred embodiments and the comparative examples of the present invention is subjected to a solution treatment to form a single phase (alpha phase), and an extruded material extruded at a temperature of about 300 DEG C is used. Further, according to the preferred embodiment and the comparative example of the present invention, the β-phase is composed of Mg ₁₇ Al ₁₂ unless otherwise specified as a precipitate phase.

Table 2 shows the results of measuring the yield strength, tensile strength and elongation of the magnesium alloys according to Examples 1 to 6, Comparative Examples 1 and 2. As shown in Table 2, it can be seen that the magnesium alloy according to Examples 1 to 4 including the MishMetal has a significantly higher yield strength and tensile strength than the magnesium alloy containing no MishMetal.

number Yield strength (MPa) Tensile Strength (MPa) Elongation (%) Example 1 261 379.9 9.3 Example 2 224 365 13.9 Example 3 282 376.7 8.7 Example 4 262 370.4 9.5 Example 5 261 376 9.2 Example 6 296 383.5 6.9 Comparative Example 1 171 324 27 Comparative Example 2 197 340 20

Fig. 1 (a) is a SEM image of a magnesium alloy according to Example 1 taken at various magnifications, and Fig. 1 (b) is a TEM image of a magnesium alloy according to Example 1. Fig.

As shown in FIG. 1, it can be confirmed that a large number of β phases (Mg ₁₇ Al ₁₂ ) and an intermetallic compound Al ₁₁ (RE) ₃ phase are formed on the α phase indicated by a dark color in the magnesium alloy according to Example 1 . In addition, the magnesium alloys according to Example 1 is made of Al ₁₁ (RE) ₃ and different from the size of the crystal grains is maintained below 1㎛, the grain inside has therefore a number of different forms β, Al ₁₁ (RE) ₃ phase and the β A sufficient level of strength can be maintained.

FIG. 2 (a) is a SEM image of the magnesium alloy according to Example 3 taken at various magnifications, and FIG. 2 (b) is a TEM image of the magnesium alloy according to Example 3. FIG.

As shown in FIG. 2, it can be confirmed that a large number of β phases (Mg ₁₇ Al ₁₂ ) and an intermetallic compound Al ₁₁ (RE) ₃ phase are formed on the α phase represented by a dark color in the magnesium alloy according to Example 3 . Example 3 is also a magnesium alloy Al ₁₁ (RE) _third image is formed according to, and the size of the crystal grains is maintained below 1㎛, the grain inside has on the image is formed because the number of β, Al ₁₁ (RE) ₃ phase and the β So that a sufficient level of strength can be maintained. Further, it can be confirmed that the alloy according to Example 3 has smaller crystal grains and more β-phase dispersions.

3 (a) is a SEM image photograph taken at various magnifications of the magnesium alloy according to Example 5 and SEM image photographs of the magnesium alloy according to Example 1, and FIG. 3 (b) Of the magnesium alloy according to the present invention. As shown in FIG. 3, it can be confirmed that a large number of β phases (Mg ₁₇ Al ₁₂ ) and an Al ₂ Y phase, which is an intermetallic compound, are formed on the α phase indicated by a dark color in the magnesium alloy according to Example 5. In addition, since the magnesium alloy according to Example 5 is kept smaller in grain size than the magnesium alloy according to Example 1 and a large number of β-phases are formed inside the crystal grains, the Al ₂ Y phase and the β- And has a higher strength than the above.

Fig. 4 (a) is a SEM image photograph taken at various magnifications of the magnesium alloy according to Example 6 and SEM image photographs of the magnesium alloy according to Example 1, and Fig. 4 (b) Of the magnesium alloy according to the present invention. As shown in FIG. 4, it can be seen that the magnesium alloy according to Example 6 also has a large number of β-phases and an intermetallic compound, Al ₂ Y phase, formed on the α-phase indicated by a dark color. In addition, the magnesium alloy according to Example 6 has a smaller grain size than that of the magnesium alloy according to Example 3, and has a greater strength than Example 4 because many β phases are formed inside the crystal grains.

The magnesium alloy according to the preferred embodiment of the present invention has been described in detail with reference to the accompanying drawings. However, it will be understood by those skilled in the art that various modifications and variations can be made in the present invention. Accordingly, the scope of the present invention is limited only by the scope of the following claims.

Claims (1)

Al from 8.0 wt% to 9.5 wt%
Zn to 0.7 wt% to 2.3 wt%
Y, and Mish metal is included in an amount of not less than 0.5% by weight and less than 3.0% by weight,
And magnesium (Mg).

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