KR101124235B1 - Aluminium alloy and aluminium alloy casting - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to metal alloys and, more particularly, to aluminum alloys used in components such as electrical, electronic, mechanical, and the like, and aluminum alloy castings produced using the same. The aluminum alloy according to one embodiment contains 4 to 13% by weight of silicon (Si), 1 to 5% by weight of copper (Cu) and 26 or more and less than 40% by weight of zinc (Zn), with the remainder being aluminum (Al). ) And unavoidable impurities.

Description

Aluminum alloy and aluminum alloy casting

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to metal alloys and, more particularly, to aluminum alloys used in components such as electrical, electronic, mechanical, and the like, and aluminum alloy castings produced using the same.

Recently, as the appearance and functionality of electronic products such as notebooks and mobile phones are complicated, the need for high strength materials that can withstand more deformation is increasing. In particular, parts such as brackets that support the LCD panel part, or thin and complex hinges require a lightweight material for portability and high strength similar to that of stainless steel (eg, Stainless Steel 304). Do. However, stainless steel can be processed by pressing or forging method, but there is a limit to the realization of precise mechanical shape and mass production, and the specific gravity is 8.00 g / cm ^{3, which} is heavy, and the need to develop high strength lightweight alloy is increasing.

Accordingly, the present invention has been made to solve the above-mentioned problems, the strength is superior to conventional commercial aluminum alloy even through a conventional die casting method, having a strength similar to that of conventional stainless steel (for example, Stainless Steel 304) more than twice An aluminum alloy having light properties and an aluminum alloy casting made using such an aluminum alloy are provided. The foregoing problem has been presented by way of example, and the scope of the present invention is not limited by this problem.

According to one aspect of the invention, it contains 4 to 13% by weight of silicon (Si), 1 to 5% by weight of copper (Cu) and 26 or more and less than 40% by weight of zinc (Zn), the remainder is aluminum (Al) ) And an unavoidable impurity is provided.

According to a feature of the aluminum alloy according to one aspect of the invention, the content of the silicon may be 5 to 10% by weight.

According to another feature of the aluminum alloy according to one aspect of the invention, the content of the silicon may be 5 to 8% by weight or less, in this case, the content of copper may be 2 to 5% by weight, furthermore the content of zinc 26 to 35% by weight.

According to another aspect of the invention, 4 to 13% by weight of silicon (Si), 1 to 5% by weight of copper (Cu), 26 to 40% by weight of zinc (Zn), 0.1% by weight or less of strontium ( Aluminum alloy including Sr) and 43 to 69% by weight of aluminum (Al) may be provided.

According to a feature of the aluminum alloy according to another aspect of the present invention, the content of the silicon may be 5 to 10% by weight.

According to another feature of the aluminum alloy according to another aspect of the present invention, the content of the silicon may be 5 to 8% by weight or less, wherein the copper content may be 2 to 5% by weight, furthermore zinc content May be 26 to 35% by weight.

According to another feature of the aluminum alloy according to another aspect of the present invention, the strontium may be greater than 0 and less than 0.04% by weight.

According to another feature of the aluminum alloy according to another aspect of the present invention, the strontium may be greater than 0 and less than 0.02% by weight.

According to another feature of the aluminum alloy according to another aspect of the present invention, titanium (Ti), magnesium (Mg), nickel (Ni), vanadium (V), tin (Sn), iron (Fe), chromium (Cr ), Zirconium (Zr), scandium (Sc) and manganese (Mn) may further include any one or more of one or more elements selected from 3 wt% or more (greater than zero).

According to another aspect of the present invention, an aluminum alloy casting manufactured using the above-described aluminum alloy is provided.

Aluminum alloys and aluminum alloy castings according to embodiments of the present invention exhibited superior strength compared to conventional commercial aluminum alloys by controlling the alloy composition, but also significantly lighter than stainless steels. Therefore, the aluminum alloy and the aluminum alloy casting according to embodiments of the present invention can be stably applied to small / light weight products as well as large products.

The effects of the present invention are not limited to those mentioned above, and other effects, which are not mentioned above, will be clearly understood by those skilled in the art from the following description.

Figure 1 shows the tensile test results of the experimental example and the ADC12 alloy of a commercial aluminum alloy according to the present invention.
2 is a result of comparing the microstructure of the commercial aluminum alloy and the aluminum alloy according to an embodiment of the present invention.
3 and 4 are the results of observing the microstructure of the aluminum alloy according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you.

In embodiments of the present invention, the weight percent (wt%) is expressed as a percentage of the weight of the component in the weight of the total alloy. It can be understood that the range for the weight percent does not include the boundary value when it is above or below, but includes the boundary value when it is simply designated as a range or above or below.

In embodiments of the present invention, unavoidable impurities may refer to impurities that can be introduced unintentionally in the manufacture of aluminum alloys or aluminum castings.

Copper alloy according to an embodiment of the present invention can be formed by adding silicon (Si), copper (Cu) and zinc (Zn) to the main element aluminum. The content of aluminum, which is the main element of the aluminum alloy, may occupy the remainder other than the additional element, and thus the content may vary depending on the content of the additional element. The aluminum alloy may contain unavoidable impurities which are inadvertently contained in each element or at the alloying stage.

For example, the aluminum alloy contains 4 to 13% by weight of silicon, 1 to 5% by weight of copper and at least 26 to less than 40% by weight of zinc, with the remainder consisting of aluminum and unavoidable impurities.

Silicon is highly fluid in the molten aluminum and can be added to improve the injectability during solidification. In addition, in the case of an aluminum-silicon alloy (Al-Si alloy), it may exhibit a mixed structure of the primary α-aluminum phase and the process silicon phase during casting, and the process silicon phase may be improved to be refined from the needle bed to the particulate or fibrous shape. In this case, the mechanical strength can be significantly improved.

However, in some cases, the brittleness of the alloy is increased and mechanical properties are degraded, which may cause a problem that the product is broken when the product is separated from the mold during the die casting process. Therefore, considering all of these effects, the silicon content of the present embodiment may be limited to the range of 4 to 13% by weight, may be strictly limited to the range of 5 to 10% by weight, and more strictly 5 to 8% by weight. It may be limited to the following.

Copper has a maximum solid solubility of about 5.6% by weight at an eutectic temperature of 548 ° C. for aluminum and may exhibit a solid solution strengthening effect when employed in aluminum. In addition, when zinc is added to aluminum, it reacts with zinc and aluminum to form an Al-Zn-Cu compound, which acts as an obstacle that prevents the movement of dislocations during deformation of the alloy or inhibits grain growth. It can contribute to improving the strength of the alloy.

However, if the content is too high, the brittleness is increased, the mechanical properties are lowered, and since it is a heavier element than aluminum, it is not effective in reducing the specific gravity, and may deteriorate the castability of aluminum. Therefore, the copper content in the present embodiment may be limited to the range of 1 to 5% by weight, strictly 2 to 5% by weight, taking all of these effects into consideration.

When zinc is added to aluminum, it is dissolved in about 80% by weight at 382 ° C., but the solid solution decreases rapidly with decreasing temperature, so in the case of the aluminum alloy according to the present invention, about 18% by weight Zinc is in a dissolved state. At this time, the excess zinc that is not dissolved may be used to react with aluminum and copper to form an Al-Zn-Cu compound as described above. Therefore, in order to obtain all the effects of solid solution strengthening and compound formation of zinc, it is necessary to add more than 26% by weight of zinc into aluminum.

However, zinc is an element that is heavier than aluminum, and thus is disadvantageous in weight reduction. If the content exceeds 36% by weight, the vacancy of the β phase is a mixed phase of the β 'phase and the α phase as the two phases of vacancy, resulting in low strength and high elongation. The amount can be increased. In addition, when the zinc content is 40% by weight, the process Si phase in the aluminum alloy is present in the primary α phase, thereby increasing the grain size and decreasing the strength. Therefore, zinc needs to be limited to the range of less than 40% by weight in view of such a point.

Aluminum alloy according to another embodiment of the present invention is 4 to 13% by weight of silicon (Si), 1 to 5% by weight of copper (Cu), 26 to more than 40% by weight of zinc (Zn), 0.1% by weight or less It may include strontium (Sr) and 43 to 69% by weight of aluminum (Al).

For example, when strontium is additionally added, the strength of the aluminum alloy may be improved by miniaturizing the crystal structure of the aluminum alloy. That is, in the case of an aluminum alloy containing silicon, it is possible to exhibit a mixed structure of the primary α phase and the eutectic Si phase during casting, and by adding strontium, it is possible to contribute to the improvement of strength by miniaturizing the microstructure of the eutectic Si phase.

However, when the content of strontium is high, mechanical properties may be lowered by crystallization of the compound containing strontium. Therefore, the strontium content of the present embodiment may be limited to the range of 0.1 wt% or less, strictly greater than 0 and less than 0.04 wt%, more strictly greater than 0 and less than 0.02 wt%, taking all these effects into consideration. .

In addition, in addition to silicon, copper, zinc, and strontium, the main element aluminum may be added in small amounts of additive elements for improving the strength of the aluminum alloy. As the additive element, titanium (Ti), magnesium (Mg), nickel (Ni), vanadium (V), tin (Sn), iron (Fe), chromium (Cr), zirconium (Zr), scandium (Sc) And manganese (Mn), and one or more selected from these additive elements may be added in a range of 3 wt% or less in total.

Aluminum alloy casting according to an embodiment of the present invention can be manufactured using the above-described aluminum alloy. Here, the casting may include a pure casting manufactured through casting and a product obtained by molding a preformed casting into a predetermined shape, such as an extrusion billet, a rolling plate, and the like. Examples of pure castings include sand casting, die casting, gravity mold casting, low pressure casting, squeeze casting, lost wax casting, thixo casting, and the like.

Gravity casting may refer to a method of injecting a molten alloy into the mold using gravity, and low pressure casting may refer to a method of injecting molten metal into the mold by applying pressure to the molten surface of the molten alloy using gas. . Thixocasting is a casting technique in a semi-melt state that combines the advantages of conventional casting and forging.

The aluminum alloy casting according to this embodiment can be manufactured through any of the processes including the above-described process, and can have appropriate strength and workability without performing heat treatment. Optionally, the aluminum alloy casting may undergo a post-manufacture heat treatment step depending on its use and shape.

Hereinafter, experimental examples are provided to help the understanding of the present invention. However, the following experimental examples are only for helping understanding of the present invention, and the present invention is not limited to the following experimental examples.

Table 1 shows the results of tensile strength as the alloy composition and the mechanical properties of the experimental and comparative examples according to the present invention.

Si Cu Zn Al Sr Tensile Strength (Mpa) Example 1 5.0 2.0 26.0 66.7 0.0 433.4 Example 2 6.0 2.0 26.0 65.7 0.0 441.6 Example 3 6.0 3.5 30.0 60.2 0.0 451.8 Example 4 6.0 5.0 30.0 58.7 0.0 439.4 Example 5 7.0 2.0 26.0 64.7 0.0 444.6 Example 6 7.0 2.0 30.0 60.7 0.0 440.9 Example 7 6.0 5.0 30.0 58.7 0.0 436.2 Example 8 6.0 3.5 31.0 59.2 0.0 443.1 Example 9 6.0 2.0 32.0 59.7 0.0 419.7 Example 10 6.0 2.0 32.0 59.7 0.0 416.8 Example 11 6.0 2.0 35.0 56.7 0.0 443.2 Example 12 6.0 3.5 35.0 55.2 0.0 444.0 Example 13 6.0 5.0 35.0 53.7 0.0 440.6 Example 14 8.0 2.0 26.0 63.7 0.0 441.7 Example 15 8.0 2.0 27.0 62.4 0.0 441.9 Example 16 8.0 3.5 28.0 60.2 0.0 436.7 Example 17 8.0 2.0 30.0 59.7 0.0 430.2 Example 18 6.0 2.0 30.0 61.5 0.0 420.2 Example 19 6.0 2.0 30.0 61.7 0.02 488.8 Example 20 6.0 2.0 28.0 63.6 0.02 465.1 Example 21 6.0 2.0 30.0 61.6 0.1 438.0 Comparative Example 1 0.0 2.1 30.1 67.4 0.0 321.1

High purity aluminum (99.8%) and zinc (99.9%) were used to prepare an aluminum alloy according to the present experimental example, and an aluminum mother alloy containing silicon, copper and strontium was added for addition of silicon, copper and strontium, respectively. It was.

Each alloying element was dissolved using an electric resistance furnace, and degassing and degassing treatment were performed by blowing argon (Ar) gas into the degassing apparatus for 5 minutes before injection.

In the case of strontium, an aluminum mother alloy containing strontium was added and maintained for a predetermined time, followed by tapping to prepare a test piece.

Specimens used to measure the mechanical properties of each experimental example were prepared using die casting. Specifically, a tensile test was performed two days after casting to cast a rod-shaped tensile specimen using a TOYO die-casting apparatus having a clamping force of 1,300 KN and to reduce the variation of mechanical properties. Mechanical properties were measured and seven or more specimens were used for the average value.

The die casting used in this test was performed under the casting temperature of 963 to 983K and the mold temperature of 463 to 473K. The test piece used for the test was manufactured as No. 14 rod proportional test piece in accordance with KSB0802 standard.

In order to observe the microstructure by the optical microscope (OM), specimens were taken from the central portion of the tensile test specimens. The specimens were polished with abrasive paper and abrasive cloth, washed with alcohol for 20 minutes, and then corroded. In addition, an analysis was performed using a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS) to analyze the solubility of zinc in the α-aluminum phase matrix and the type and shape of the process.

Meanwhile, ADC12 alloy, which is a commercial aluminum alloy, was used as a target for comparing the tensile strength of the aluminum alloy according to the present experimental example, and FIG. 1 shows the tensile test results of the experimental example 19 and the ADC12 alloy.

Referring to Table 1, in comparison with Example 21 and Comparative Example 1 having the same copper and zinc composition, the tensile strength of Example 21 with silicon was increased about 110 MPa compared to Comparative Example 1 without silicon. Able to know. From this, it can be seen that in the case of the aluminum alloy according to the embodiment of the present invention, the value of tensile strength is remarkably improved as the silicon is added.

In addition, referring to FIG. 1, the tensile strength of the alloys according to Experimental Examples 1 to 21 was about 120 MPa or more, compared to the tensile strength of the ADC12 alloy having silicon and copper as the major alloying elements as a commercial aluminum alloy. It can be seen.

From this, it can be seen that the aluminum alloy according to the embodiment of the present invention shows very excellent strength characteristics compared to the conventional commercial aluminum alloy.

The reason why the aluminum alloy according to the present experimental example shows superior characteristics compared to the ADC12 alloy is that zinc is added to the aluminum together with silicon and copper to refine the alloy structure.

Hereinafter, for convenience, an aluminum alloy in which zinc, silicon, and copper are added by weight percent of x, y, and z, respectively, is expressed as Al-xZn-ySi-zCu.

2A shows the alloy structure of the Al-30Zn alloy, and FIGS. 2B and 2C show the alloy structure of the Al-30Zn-6Si-2Cu and Al-40Zn-6Si-2Cu alloys, respectively.

Referring to FIG. 2A, it can be seen that in the case of Al-30Zn alloy, the aluminum-zinc process phase is uniformly dispersed at the grain boundary due to the excess zinc not dissolved in the primary α phase.

On the other hand, referring to Figure 2b, it can be seen that in Al-30Zn-6Si-2Cu alloy growth of the primary α phase is suppressed, the grain size is significantly reduced in the range of several micrometers to 20 micrometers.

3 shows the results of the EDS analysis of the zinc content (% by weight) in each region of the Al-30Zn-6Si-2Cu alloy shown in FIG. 2B together with a table.

As shown in FIG. 3, it can be seen that up to about 18% by weight of zinc is dissolved in the α-Al phase (first region), and it can be seen that zinc is stably present in the vicinity of the process Si phase up to 18% (second). domain). At this time, it is determined that the excess zinc, which is not dissolved, reacts with aluminum and copper to form an Al-Zn-Cu compound (zones 3 and 4). It is estimated to contribute to. Therefore, the crystallization of the Al-Zn-Cu compound is expected to contribute to the improvement of the strength of the aluminum alloy together with the process Si phase.

However, as shown in FIG. 2C, in the Al-40Zn-6Si-2Cu alloy, the eutectic Si phase does not retreat to the grain boundary but is present in the primary α, resulting in an increase in grain size, thereby decreasing the strength. It is expected to. Therefore, it is expected that the zinc content of less than 40% by weight is preferable in terms of strength improvement.

Hereinafter, the experimental results according to the alloy composition shown in Table 1 will be described in more detail.

Referring to Table 1, in Examples 5, 6, 14, 15, 16, and 17 in which the content of silicon is more than 6 and 8% by weight and the content of copper is 2 to 3.5% by weight, the content of all zinc is about 430 to Relatively good tensile strength results in the 445 MPa range were obtained.

From this, the aluminum alloy according to the embodiment of the present invention was determined to exhibit a relatively good and stable strength characteristics compared to the region of 6 wt% or less when the silicon content exceeds 6 wt%.

Experimental Examples 19-21 are all aluminum alloys which added 0.02 to 0.1 weight% of strontium besides silicon, copper, and zinc as an addition element of an aluminum alloy.

Compared with Experimental Examples 19 and 20, respectively, Experimental Examples 19 and 20, it can be seen that the tensile strength is increased by 20 to 60 MPa or more by adding 0.02% by weight of strontium. This significant increase in tensile strength is believed to be due to the refinement of the Si phase due to the addition of strontium.

4A and 4B show the results of SEM observation of the alloy structure of the aluminum alloy having the same silicon, copper, and zinc composition as that of Experimental Example 18 without adding strontium and further adding 0.04% by weight of strontium.

In contrast to the structure (arrow) of the process Si phase of Figures 4a and 4b, it can be seen that it has a finer process Si phase when strontium is added.

On the other hand, when comparing the strontium content of 0.02% by weight when compared to Experimental Examples 19 and 21 showed a relatively better tensile strength results than when 0.1% by weight, from this it is necessary to maintain the content of strontium below 0.1% by weight You can see that there is.

The foregoing description of specific embodiments of the invention has been presented for purposes of illustration and description. Therefore, the present invention is not limited to the above embodiments, and various modifications and changes are possible in the technical spirit of the present invention by combining the above embodiments by those skilled in the art. It is obvious.

Claims (14)

Aluminum containing 4 to 13% by weight of silicon (Si), 1 to 5% by weight of copper (Cu) and at least 26 and less than 40% by weight of zinc (Zn), the remainder consisting of aluminum (Al) and unavoidable impurities alloy. The aluminum alloy of claim 1, wherein the content of silicon (Si) is 5 to 10 wt%. The aluminum alloy of claim 2, wherein the content of silicon (Si) is 5 to 8% by weight or less. The aluminum alloy according to claim 3, wherein the content of copper (Cu) is 2 to 5 wt%. The aluminum alloy according to claim 4, wherein the content of zinc (Zn) is 26 to 35 wt%. delete delete delete delete delete delete delete delete An aluminum alloy casting manufactured using the aluminum alloy according to any one of claims 1 to 5.

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