KR101941774B1 - Die-casting magnesium alloy having high strength - Google Patents

Abstract

In the present invention, an alloy element such as calcium (Ca), strontium (Sr), micrometal (Mm), or yttrium (Y) is added based on a Mg-Al- It is an object of the present invention to provide a magnesium alloy for die casting which has economic and excellent tensile strength by controlling the addition ratio of alloy elements constituting the alloy system.
The magnesium alloy according to the present invention is characterized in that it comprises 6.0 to 8.5 wt% of Al, 0.2 to 1.0 wt% of Mn, 0.8 to 2.0 wt% of Ca, 0.05 to 0.5 wt% of Sr, 0.1 to 0.5 wt% of Y, 0.8 to 1.5% by weight, and the balance of magnesium and unavoidable impurities, wherein the content of Fe is 0.006% by weight or less, the content of Cu is 0.040% by weight or less, the content of Ni is 0.002% by weight or less and the tensile strength at room temperature Of not less than 250 MPa and an elongation of not less than 5%.

Description

{DIE-CASTING MAGNESIUM ALLOY HAVING HIGH STRENGTH}

The present invention relates to a magnesium alloy which can be used in a field where high mechanical and corrosion characteristics are required such as a vehicle or an electronic part. More specifically, the present invention relates to a magnesium alloy which is excellent in selection of alloying elements added to magnesium, Temperature strength and corrosion characteristics, and particularly to a magnesium alloy suitable for die casting casting.

Magnesium alloys are the lightest alloys currently commercialized and are used in automotive applications to maximize weight savings. In recent years, there has been a rapid increase in the demand for automobile parts employing magnesium alloys due to the enlargement through integration of parts and the application of automobile parts using processing materials.

On the other hand, in developing magnesium alloy for application to automobile parts, various matters should be considered at the same time, and first, it should have corrosion resistance suitable for high strength, high ductility and use environment. In addition, the elements added to the magnesium alloy for die casting are aluminum (Al), silicon (Si), calcium (Ca), tin (Sn), strontium (Sr) The higher the price, the higher the price.

The magnesium alloy for die casting mainly uses Al as the main alloy element because the addition of Al improves the corrosion resistance together with the strength of the magnesium alloy.

Currently, commercialized magnesium alloys for die casting include AZ91D, a high strength alloy, and AM50A and AM60B alloys with high ductility. However, there are no alloys satisfying both high strength and high ductility, and die casting magnesium alloy component manufacturers are largely small, Is not enough.

In addition, the magnesium alloy for diecasting which is currently being developed has a relatively poor corrosion resistance and thus has limitations in general application to automobiles and electronic parts.

Therefore, it is required to develop a magnesium alloy having aluminum (Al) as a main alloy element and excellent in strength, ductility and corrosion resistance. The magnesium alloy developed for this purpose is made of Al or Zn as a main alloy element, Ca, silicon (Si), rare earth (RE), and strontium (Sr).

In recent years, it has become an important development objective of magnesium alloys to lower the production cost while maintaining mechanical strength and corrosion resistance equivalent to those of conventional magnesium alloys. Examples of magnesium alloys developed for this purpose include the following.

Hydro Magnesium is a magnesium alloy for die casting that focuses on the improvement of AS and AE alloys. AS21X alloy, which is made by adding a small amount of misch metal instead of reducing the Mn content to AS21 alloy, And developed AE44 alloy which improved the characteristics of AE42 alloy.

In addition, Honda developed the ACM522 alloy with 2.5 wt% RE and 2.0 wt% Ca in the AM50 alloy with Mitsui Mining Smelting and applied it to the oil pan, There is an example applied to a hybrid car insight engine of the company.

Mitsubishi Aluminum developed MACS1X alloy by adding 1.6 ~ 2.4 wt.% Of Ca, Mn and Sr to AM50 and AM60 alloys and compared it with other alloys, Mass production.

GM has developed an AXJ alloy containing 1.7 to 3.3 wt% of Ca and 0.2 wt% of Sr in the AM50 alloy. However, in this case, there is also a problem such as mold adsorption and thermal cracking due to a high Ca content.

Korean Patent Publication No. 2006-0040745

The present invention is based on the Mg-Al-Mn alloy system and can be provided with high strength and high ductility corresponding to the previously developed magnesium alloy while minimizing the use of expensive alloying elements, To provide a method for producing an alloy.

One aspect of the present invention for solving the above problems is a method of manufacturing a semiconductor device, comprising: 6.0 to 8.5 wt% of Al; 0.2 to 1.0 wt% of Mn; 0.8 to 2.0 wt% of Ca; 0.05 to 0.5 wt% Wherein the Fe content is 0.006 wt% or less, the Cu content is 0.040 wt% or less, the Ni content is 0.002 wt% or less, the tensile strength at room temperature is 250 MPa or more, and the balance of magnesium and unavoidable impurities. , And an elongation of 5% or more.

Another aspect of the present invention for solving the above-mentioned problems is to provide a method of manufacturing a semiconductor device, comprising: 6.0 to 8.5 wt% of Al; 0.2 to 1.0 wt% of Mn; 0.8 to 2.0 wt% of Ca; 0.05 to 00 wt% A method for producing a magnesium alloy, comprising the step of adding Mn to the FeMn compound and removing the FeMn compound with sludge by dissolving the magnesium alloy in an amount of 0.006 wt% or less, .

The magnesium alloy according to the present invention exhibits excellent room temperature strength and ductility and can be used for parts requiring high mechanical properties in automobile parts and parts for electronic equipment since diecasting is possible.

Further, according to the method for producing a magnesium alloy according to the present invention, the content of Fe having a bad influence on corrosion resistance can be kept very low, and the corrosion resistance is excellent.

Figs. 1 to No. 7 is a microstructure photograph of a magnesium alloy die cast.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. Also, when a part is referred to as "including " an element, it does not exclude other elements unless specifically stated otherwise.

The inventors of the present invention have conducted research to minimize the use of expensive alloying elements as much as possible and to have high strength and high ductility corresponding to magnesium alloys developed using existing expensive elements at a minimum cost, (Mg ₁₇ Al ₁₂ , Al ₈ Mn ₅ , (Mg, Al) ₂ Ca, Al ₁₁ Mn ₄ , and Al (Mg) ₄ led to the Sr, AlMgSr, Al ₂ Ce, invention ₁₁ Ce ₃ Al, etc.) type and by controlling the fraction, good mechanical properties (in mind that we can get the room temperature strength and ductility, and so on) and the corrosion resistance of the present.

The magnesium alloy according to the present invention is characterized in that it contains 6.0 to 8.5 wt% of Al, 0.2 to 1.0 wt% of Mn, 0.8 to 2.0 wt% of Ca, 0.05 to 0.5 wt% of Sr and 0.1 to 0.5 wt% of Y, .

In addition, it may further contain 1.0 to 1.5% by weight of mis-metal (Mm) as a rare earth element.

In the impurity, the content of Fe is 0.006 wt% or less, the content of Cu is 0.040 wt% or less, the content of Ni is 0.002 wt% or less % Or less.

The magnesium alloy according to the present invention preferably has a tensile strength at room temperature of 250 MPa or more and an elongation of 5% or more.

Further, the alloy according to the present invention can be preferably used for die casting casting.

Further, the alloy according to the present invention can be produced by a method of controlling the content of Fe contained as impurities to be 0.007% by weight or less by removing FeMn compounds through sintering by producing FeMn compounds at the time of dissolving the magnesium alloy .

The reason why the composition range of each component constituting the magnesium alloy according to the present invention is limited as described above is as follows.

Aluminum (Al): 6.0 to 8.5 wt%

Aluminum is solubilized in the magnesium matrix at a maximum solubility limit of about 12 wt% at 437 DEG C in the magnesium matrix and at most 9 wt% in the case of the Mg-Al binary alloy, and exhibits solid solution strengthening effect.

If the aluminum content is lowered to less than 6.0 wt%, it is preferable that the main composition of the die casting alloy is deteriorated and the strength at room temperature is lowered to be 6.0 wt% or more. On the other hand, aluminum reacts with magnesium to form a Mg ₁₇ Al ₁₂ phase, which contributes to improvement of strength at room temperature. However, since it inhibits high-temperature characteristics due to grain boundary softening due to a low melting point at a high temperature, it is preferable to limit it to 8.5 wt% or less.

Manganese (Mn): 0.2 to 1.0 wt%

Manganese reacts with iron, which has an adverse effect on the corrosion resistance of magnesium alloys, to form FeMn compounds, which are sludge-filtered to lower the iron content of magnesium alloys, thereby improving the corrosion resistance of magnesium alloys.

If the content of manganese is too low, the above effect can not be obtained. On the other hand, when 1.0 wt% or more of manganese is added, 1.0 wt% or less of Mn is produced and 0.5 wt% or less is more preferable because it produces primary Mn and decreases mechanical properties.

Calcium (Ca): 0.8 to 2.0 wt%

Calcium forms an oxide film on the surface of the magnesium alloy melt to improve the oxidation resistance during the casting process. It can reduce the consumption of SF ₆ gas, which is used as a protective gas in the dissolution of magnesium, and react with aluminum to form an intermediate phase such as Al ₂ Ca Thereby improving the corrosion resistance characteristic of the magnesium alloy.

In order to obtain the effect of calcium, it should be added in an amount of not less than 0.8 wt%. On the other hand, when the content of calcium exceeds 2.0 wt%, the adsorption of the mold is increased due to the reaction with the die casting mold, and the recovery rate of the magnesium alloy It is preferably 0.8 to 2.0% by weight.

Strontium (Sr): 0.05 to 0.5 wt%

Strontium improves the fluidity of the molten metal and functions to refine the crystal grains of the magnesium alloy, thereby improving the strength of the magnesium alloy. In addition, it reacts with aluminum or magnesium to generate compounds such as Al ₄ Sr and MgAlSr which are thermally stable in the grain boundary, thereby contributing to the improvement of strength. Strontium is a relatively expensive element. When it exceeds 1.0% by weight, the elongation is lowered. Therefore, when the content is less than 0.5% by weight, .

Yttrium (Y): 0.1 to 0.5 wt%

Yttrium has a large solubility in magnesium alloys and is an effective element for precipitation strengthening. Al ₂ O ₃ An oxide layer is formed to increase ignition resistance. In addition, it reacts with aluminum to generate a thermally stable Al ₂ Y phase, which contributes to improvement of mechanical properties. Since Y is a relatively expensive element, it is preferably contained in the range of 0.1 wt% or more and 0.5 wt% or less.

Mis-metal (Mm): 0.8 to 1.5 wt%

The mis-metal to be added to the present invention may generally be a mixture of one or more elements belonging to atomic number 57 (La, lanthanum) to 71 (Lu, ruthenium). On the other hand, cerium richmicum metal (Mm) is composed of approximately 50% by weight of Ce, 25% by weight of La, 20% by weight of Nd and 5% by weight of Pr, It is a preferable example because it is less expensive than other rare earth metals.

It is preferable to add at least 0.8 wt% or more of magnesium to the rare earth metal in order to improve the strength and corrosion resistance by generating a middle phase of Al ₁₁ RE _{3 in} the grain boundary due to reaction with aluminum. When the rare earth metal is added in an excessive amount, There is a problem that not only the cost is increased but also the strength and elongation are lowered, so that it is limited to 1.5% by weight.

On the other hand, when the sum of addition amounts of mis-metal (Mm) and yttrium (Y) is more than 2.0% by weight in the case of including mis-metal (Mm), the tensile strength and elongation may be rather lowered. As shown in FIG.

In addition, the magnesium alloy includes reactive precipitates between Mg and the alloying elements, and the reactive precipitates are distributed more in the grain boundaries than in the grain.

Other unavoidable impurities

The magnesium alloy according to the present invention may include a raw material of the alloy or an impurity which is inevitably incorporated in the manufacturing process. Of the impurities that can be contained in the magnesium alloy according to the present invention, Fe, Cu and Ni may deteriorate the corrosion resistance of the magnesium alloy It is a component that plays a role. Therefore, it is preferable that the Fe content is 0.007 wt% or less, the Cu content is 0.040 wt% or less, and the Ni content is 0.003 wt% or less.

Hereinafter, the magnesium alloy according to the present invention will be described in more detail with reference to examples.

First, the magnesium alloy was cast using a 350-ton cold chamber die casting machine and a 240-liter vacuum tank equipped with a melt temperature of 690 캜, a mold temperature of 200 캜, and an injection pressure of 260 kgf / Diecasting magnesium alloys having various compositions as shown in Table 1 below were prepared.

In order to observe the microstructure of the magnesium alloy prepared in the composition of Table 1, specimens for microstructure observation were collected from the alloying specimens prepared by the die casting process. Each specimen was mounted on a resin and sanded 100 to 4000 times After mechanical polishing with 0.05 mm alumina powder, it was etched with a 0.5% Nital solution.

Fig. 1 alloy composition of a magnesium alloy. As can be seen from microstructural photographs, most of the precipitate phases are distributed more in the grain boundaries than in the mouth. Mg ₁₇ Al ₁₂ , which is a process system, is also formed mainly in the grain boundary because most of the phases generated due to the rapid cooling rate are intensively formed in the grain boundaries due to the characteristics of the die casting process. This phenomenon is caused by the other No. Magnesium alloys with 2-7 alloy compositions were also observed.

The precipitation phases of Ca, Mn, Sr, Mm, Y, etc., which react with magnesium or aluminum through EDS of XRD and SEM to form these phases, are shown in Table 1 below.

Alloy number Furtherance Generated Enhancement Award One Mg-8.0Al-0.3Mn Mg ₁₇ Al ₁₂ 2 Mg-8.0Al-0.3Mn-1.0Ca Mg ₁₇ Al ₁₂ , (Mg, Al) ₂ Ca, Al ₈ Mn ₅ , Al ₁₁ Mn ₄ 3 Mg-8.0Al-0.3Mn-1.0Ca-0.1Sr _{Mg 17 Al 12, (Mg,} Al) 2 Ca, Al 8 Mn 5, Al 11 Mn 4, Al 4 Sr, AlMgSr 4 Mg-8.0Al-0.3Mn-1.0Ca-0.1Sr-0.1Y _{Mg 17 Al 12, (Mg,} Al) 2 Ca, Al 8 Mn 5, Al 11 Mn 4, Al 4 Sr, AlMgSr, Al 3 Y 5 Mg-8.0Al-0.3Mn-1.0Ca-0.1Sr-0.3Y _{Mg 17 Al 12, (Mg,} Al) 2 Ca, Al 8 Mn 5, Al 11 Mn 4, Al 4 Sr, AlMgSr, Al 2 Y 6 Mg-8.0Al-0.3Mn-1.0Ca-0.1Sr-0.3Y-1.0Mm _{Mg 17 Al 12, (Mg,} Al) 2 Ca, Al 8 Mn 5, Al 11 Mn 4, Al 4 Sr, AlMgSr, Al 2 Y, Al 2 Ce, Al 11 Ce 3 7 Mg-8.0Al-0.3Mn-1.0Ca-0.1Sr-0.3Y-2.0Mm _{Mg 17 Al 12, (Mg,} Al) 2 Ca, Al 8 Mn 5, Al 4 Sr, Al 2 Y, Al 2 Ce, Al 11 Ce 3

The tensile test of the magnesium alloy with microstructure at room temperature was carried out using a rod-shaped specimen with a gauge distance of 20 mm and a diameter of 4 mm (ASTM B557M). In order to prevent premature failure of the specimen during the tensile test Before the experiment, the surface of the specimen was polished using sandpaper 2,000 times.

The tensile test was carried out at a nominal strain rate of 2 x 10 < ^-4 > / s at room temperature. For the reproducibility of the experimental results, five or more specimens were subjected to tensile tests under the same conditions, .

For comparison with the alloy according to the embodiment of the present invention, a room temperature tensile test was also carried out for a commercial AZ91D alloy.

Alloy number Furtherance 25 ℃ Yield strength
(MPa) The tensile strength
(MPa) Elongation
(%) One Mg-8.0Al-0.3Mn 148.2 223.8 5.1 2 Mg-8.0Al-0.3Mn-1.0Ca 173.4 233.9 3.8 3 Mg-8.0Al-0.3Mn-1.0Ca-0.1Sr 174.8 247.9 5.3 4 Mg-8.0Al-0.3Mn-1.0Ca-0.1Sr-0.1Y 167.0 259.7 6.9 5 Mg-8.0Al-0.3Mn-1.0Ca-0.1Sr-0.3Y 167.0 264.0 7.7 6 Mg-8.0Al-0.3Mn-1.0Ca-0.1Sr-0.3Y-1.0Mm 174.1 257.9 5.8 7 Mg-8.0Al-0.3Mn-1.0Ca-0.1Sr-0.3Y-2.0Mm 171.5 216.6 2.3 AZ91D Mg-9.0Al-1Zn-0.3Mn 150.0 230.0 3.0

As shown in Table 2 above, no. 4 ~ No. 6 alloy has a tensile strength of 257.9 ~ 264.0MPa which is superior to AZ910D and elongation is 5.8 ~ 6.9%, which is superior to other alloy composition.

On the other hand, in the case of the No. 7 alloy, it is estimated that the amount of Mm added was as much as 2.0% by weight and the flowability of the molten metal was remarkably decreased to deteriorate the mechanical properties due to casting defects.

Claims (7)

Al: 6.0 to 8.5% by weight,
Mn: 0.2 to 1.0% by weight,
0.8 to 2.0% by weight of Ca,
0.05 to 0.5% by weight of Sr,
0.1 to 0.5% by weight of Y,
0.8 to 1.5% by weight of Mm,
The remaining magnesium and unavoidable impurities,
In the impurities, the content of Fe is 0.006 wt% or less, the content of Cu is 0.040 wt% or less, the content of Ni is 0.002 wt%
A tensile strength at room temperature of 250 MPa or more, an elongation of 5% or more,
Die cast casting, magnesium alloy. delete delete delete The method according to claim 1,
Wherein the magnesium alloy includes reaction precipitates between Mg and an alloy element, and the reactive precipitates are distributed more in grain boundaries than in the grain. delete delete

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