TWI500775B - Aluminum alloy and manufacturing method thereof - Google Patents

Description

Aluminum alloy and manufacturing method thereof

The present invention relates to an aluminum alloy and a method of manufacturing the same.

Magnesium is one of the main alloying elements in today's aluminum alloys. The addition of magnesium can increase the strength of the aluminum alloy, making the alloy easy to surface treat and improve corrosion resistance. However, since magnesium has a high oxidation potential, oxides or impurities are mixed into the aluminum melt during the process of refining the alloy in the aluminum-added aluminum melt, which deteriorates the quality of the aluminum melt. In order to prevent the incorporation of oxides or impurities into the aluminum melt due to the addition of magnesium, a method of covering a surface of the melt with a protective gas such as sulfur hexafluoride (SF ₆ ) may be employed in the process of magnesium addition.

However, in the preparation of aluminum alloys, it is difficult to completely protect a large amount of added magnesium by using a protective gas. Moreover, sulfur hexafluoride (SF ₆ ), which is a shielding gas, is not only expensive but also causes environmental problems, and thus, the use of sulfur hexafluoride (SF ₆ ) has been gradually restricted worldwide.

The present invention provides an aluminum alloy which is manufactured in an environmentally friendly manner and which has excellent alloy characteristics, and a method of manufacturing the same. Further, the present invention provides a processed product using the aluminum alloy.

An embodiment of the method for producing an aluminum alloy according to the present invention, wherein a magnesium intermediate alloy containing a calcium-based compound and aluminum are provided. An intermediate alloy and an aluminum melted melt are formed and cast, and calcium is added to the master batch to form the intermediate alloy.

According to another embodiment of the method for producing an aluminum alloy of the present invention, the master batch may comprise pure magnesium, a magnesium alloy, pure aluminum or an aluminum alloy, and the magnesium alloy may comprise aluminum as an alloying element.

According to another embodiment of the method of the present invention, the method may further comprise adding iron less than or equal to 1.0% by weight (greater than 0%).

According to another embodiment of the method of the present invention, the intermediate alloy may be formed by the steps of melting the masterbatch to form a masterbatch melt and adding calcium to the masterbatch melt.

According to another embodiment of the method of the present invention, the intermediate alloy can be made to include a step of melting the masterbatch together with the calcium.

According to another embodiment of the method of the present invention, the masterbatch may comprise at least one of magnesium and aluminum, and the calcium-based compound may comprise a magnesium-calcium compound (Mg-Ca compound), an aluminum-calcium compound (Al-Ca compound) And at least one of a magnesium-aluminum-calcium compound (Mg-Al-Ca compound), and the magnesium-calcium compound may comprise a Mg ₂ Ca alloy, the aluminum-calcium compound comprising an Al ₂ Ca alloy and an Al ₄ Ca alloy At least one, and the magnesium-aluminum-calcium compound comprises a (Mg, Al) ₂ Ca alloy.

According to another embodiment of the method of the present invention, calcium and aluminum are first provided. A molten melt of calcium and aluminum is formed and cast. 0.1 to 40% by weight of calcium is added to the aluminum alloy.

The aluminum alloy according to an embodiment of the present invention may be an aluminum alloy produced by any of the above methods.

The aluminum alloy according to an embodiment of the present invention may have an aluminum matrix and a calcium-based compound present in the aluminum matrix, wherein the amount of calcium dissolved in the aluminum matrix is less than the solubility limit.

According to another aspect of the present invention, the aluminum alloy may contain less than or equal to 1.0% by weight of iron.

In an aluminum alloy according to another embodiment of the present invention, the aluminum matrix has a plurality of crystal domains, and the plurality of crystal domains form boundaries and are spaced apart from each other, wherein the calcium-based compound has the boundary. For example, the plurality of domains are grains and the boundary is a grain boundary. For another example, the plurality of crystal domains are phase regions formed by different phases, and the boundary is a phase boundary.

In an aluminum alloy according to another embodiment of the present invention, the aluminum matrix has a plurality of crystal domains, and the plurality of crystal domains form a boundary and are spaced apart from each other, wherein the calcium-based compound exists inside the crystal domain.

The aluminum alloy according to another embodiment of the present invention may comprise an aluminum matrix in which the dissolved amount of calcium reaches a dissolution limit, and a calcium-based compound is present in the aluminum matrix, wherein the amount of calcium in the aluminum matrix is 0.1 to 40% by weight. between.

An aluminum alloy according to another embodiment of the present invention, wherein the aluminum alloy has an average crystallite size smaller than an average grain size of an aluminum alloy produced under the same conditions without a calcium-based compound.

An aluminum alloy according to another embodiment of the present invention, wherein the aluminum alloy has a tensile strength greater than that of an aluminum alloy produced under the same conditions without a calcium-based compound.

According to an embodiment of the present invention, an intermediate alloy containing calcium as an additive is first prepared, and the intermediate alloy is added to aluminum to produce an aluminum alloy. The master alloy comprises a magnesium intermediate alloy formed using a pure magnesium or a magnesium alloy as a master batch, and an aluminum intermediate alloy formed using a pure aluminum or an aluminum alloy as a master batch.

In the present embodiment, pure magnesium or pure aluminum which is not intentionally added with an alloying element is defined as the substantial meaning of inevitably containing impurities in the production process of magnesium or aluminum. Magnesium alloys or aluminum alloys are respectively an alloy produced by intentionally adding alloying elements to magnesium or aluminum. A magnesium alloy containing aluminum as an alloying element is called a magnesium-aluminum alloy. This magnesium-aluminum alloy not only has aluminum as an alloying element but also has other alloying elements.

Fig. 1 is a flow chart showing a method of manufacturing an intermediate alloy according to an embodiment of the present invention.

Referring to Fig. 1, the method for producing the master alloy may include the following steps: a masterbatch melt forming step S1, an additive adding step S2, a stirring-resting step S3, a casting step S4, and a cooling step S5.

In the masterbatch melt forming step S1, a master batch may be placed in a furnace and the furnace is heated to form the masterbatch melt. For example, a magnesium or magnesium alloy as a masterbatch is placed in a furnace, and then the furnace is heated to form a magnesium melt. For example, magnesium is melted by heating the furnace at a temperature ranging from 600 ° C to 800 ° C. When the heating temperature is lower than 600 ° C, it is difficult to form a magnesium melt. On the contrary, when the heating temperature is higher than 800 ° C, the magnesium melt has a risk of burning.

For another example, aluminum or an aluminum alloy as a master batch may be placed in a furnace, and an aluminum melt is formed by heating the furnace at a temperature ranging from 600 ° C to 900 ° C. In the additive addition step S2, calcium as an additive is added to the masterbatch melt.

In the stirring-resting step S3, the masterbatch melt may be stirred or left to stand for a certain period of time. For example, the stirring or standing time may be from 1 to 400 minutes, and if the stirring and standing time is less than 1 minute, the additive may not be completely mixed into the masterbatch melt, and if it is longer than 400 minutes, the masterbatch The stirring and standing time of the melt are unnecessarily extended.

Calcium may be added between about 0.0001 part by weight and about 100 parts by weight, and preferably between 0.001 part by weight and 30 parts by weight, based on 100 parts by weight of the masterbatch. If the additive is less than 0.0001 parts by weight, the effects of the additive (e.g., increased hardness, slowed oxidation, increased combustion temperature, and reduced shielding gas) may be small. Also, the calcium-based compound in the magnesium intermediate alloy can be diluted in the process of adding to the aluminum alloy because the content of the intermediate alloy decreases as the amount of calcium added to the intermediate alloy increases. When the amount of calcium is more than 100 parts by weight, it is difficult to manufacture the intermediate alloy. The amount of calcium may be less than or equal to about 30 parts by weight in view of difficulty in manufacturing.

Meanwhile, when the intermediate alloy is formed by using pure magnesium or a magnesium alloy as a master batch, a small amount of a shielding gas may be selectively supplied for preventing the combustion of the magnesium melt. The shielding gas can use conventional sulfur hexafluoride (SF ₆ ), sulfur dioxide (SO ₂ ), carbon dioxide (CO ₂ ), 1,1,1,2-tetrafluoroethane (HFC-134a), magnesium smelting protective fluid. (NovecTM 612), an inert gas, its equivalent or a mixture thereof. However, the present invention does not always require this shielding gas, and therefore may not be supplied.

As described above, when calcium is added in the additive addition step S2 and/or the stirring-resting step S3, the combustion temperature is raised due to an increase in the oxidation resistance of magnesium in the melt, thereby greatly reducing the requirement of the magnesium melt. The shielding gas is used or the shielding gas is not required to be used. Therefore, according to the method for producing the magnesium intermediate alloy, environmental pollution can be suppressed by reducing or not using the amount of the protective gas such as sulfur hexafluoride (SF ₆ ).

After the stirring-resting step S3 of the masterbatch melt is completed, the magnesium melt is cast into a mold in step S4, and then the magnesium melt is cooled in step S5, and the cured intermediate alloy is Separated from the mold.

The temperature of the mold in the casting step S4 may be room temperature (for example, 25 ° C) to 400 ° C. In the cooling step S5, after the mold is cooled to room temperature, the intermediate alloy can be separated from the mold. However, if most of the intermediate alloy has solidified, the intermediate alloy can be separated even before reaching room temperature.

Therefore, the mold can be selected from any one selected from the group consisting of a metal mold, a ceramic mold, a graphite mold, and the like. And the casting method may include sand casting, die casting, gravity casting, continuous casting, low pressure casting, extrusion casting, dewaxing casting, touch casting or the like.

Gravity casting refers to a method of pouring an alloy melt into a mold by gravity. Low-pressure casting can refer to a method of pouring a melt into a mold by applying a pressure on the surface of the alloy melt by using a gas. . The cathodic casting system adopts a combination of advantages such as conventional casting and forging methods, and is subjected to die casting in a semi-solid state. However, the invention is not limited to the type of mold and the method or process of casting.

The prepared magnesium intermediate alloy may have a matrix having a plurality of crystal domains, and the plurality of crystal domains are spaced apart from each other with a boundary therebetween. For example, the plurality of crystal domains may be a plurality of crystal grains separated by grain boundaries, or may be a plurality of phase regions, wherein the plurality of phase regions are formed by phase boundaries between each other.

At the same time, a calcium-based compound is formed during the preparation of the intermediate alloy and can be dispersed in the matrix of the intermediate alloy. The calcium-based compound may be a compound formed by reacting calcium added in the additive addition step S2 with other elements such as magnesium and/or aluminum in the master batch.

For example, in the case where the master batch is pure magnesium or a magnesium alloy, may be formed calcium magnesium / calcified compound, such as Mg ₂ Ca reacted with the magnesium alloy. As another example, when the masterbatch is pure aluminum or an aluminum alloy, calcium can react with aluminum to form an aluminum/calcium compound such as an Al ₂ Ca alloy or an Al ₄ Ca alloy.

When the master batch of the magnesium intermediate alloy is a magnesium aluminum alloy, the calcium may react with magnesium and/or aluminum to form at least one of a magnesium-calcium compound, an aluminum-calcium compound, and a magnesium-aluminum-calcium compound. The magnesium - calcium may Mg ₂ Ca alloy, the aluminum - calcium alloy may include Al ₂ Ca and Al ₄ Ca alloy at least one, and the magnesium - aluminum - calcium compound may be a (Mg, Al) ₂ Ca alloy.

The calcium-based compounds are likely to be distributed in the grain boundaries or phase boundaries, that is, the boundaries between the grains or the boundaries between the different phase regions.

Since the boundary is in an open state and has relatively high energy relative to the interior of the grain or phase region, it is an advantageous location for the formation and growth of the nucleation of the calcium-based compound.

Fig. 2 is a view showing the results of a transmission electron microscope (TEM) analysis of a magnesium intermediate alloy obtained by adding calcium to a magnesium-aluminum alloy master batch.

Fig. 2(a) shows the microstructure of the magnesium intermediate alloy observed in the BF mode, and Fig. 2(b) to (d) show the results of the mapping components of the compound region crystal domains shown by TEM, that is, respectively The results of the distribution areas of magnesium, aluminum, and calcium are shown. Referring to Figures 2(a) to (b), a rod-like compound is formed in the grain boundaries in the magnesium matrix. The magnesium matrix has a plurality of crystal domains (grains) and the compound is formed within the domain boundary (grain boundary). Referring to Figures 2(c) to (d), it is shown that the strength of aluminum and calcium is higher than that of the rod-like compound (see the bright portion in Figs. 2(c) to (d)). Therefore, the rod-shaped compound is an aluminum-calcium compound. This aluminum-calcium compound may be an Al ₂ Ca alloy or an Al ₄ Ca alloy. Thus, it was confirmed that calcium and aluminum were added in the magnesium aluminum alloy to form an aluminum-calcium compound.

At the same time, the results show that the aluminum-calcium compound is mainly distributed on the grain boundaries of the intermediate alloy. Since the grain boundary has the characteristics of an open structure, the calcium-based compound is mainly distributed on the grain boundary rather than inside the grain (inside the crystal domain). However, the results of this analysis are not intended to limit the calcium-based compound of the present embodiment to only the grain boundary, and the calcium-based compound may be found inside the crystal grain in some cases.

The intermediate alloy can be added to the aluminum melt to form a magnesium-containing aluminum alloy. In some cases, the master alloy itself can be used as an alloy for special applications. For example, the aluminum intermediate alloy formed by the above method can be used as an aluminum-calcium alloy. The calcium-based compound can be formed by an aluminum matrix formed by adding calcium to pure aluminum or an aluminum alloy. Calcium can be dissolved in the aluminum matrix up to the limit of dissolution.

In the case where the amount of calcium added to the aluminum is less than the solubility limit, the calcium may be dissolved in the aluminum matrix, and the amount of calcium added to the aluminum is greater than the solubility limit, and the remaining calcium may react with aluminum to form an aluminum-calcium compound. Calcium based alloy. In the case where calcium is added to the magnesium-aluminum alloy, the calcium-based compound may contain at least one of a magnesium-calcium compound, an aluminum-calcium compound, and a magnesium-aluminum-calcium compound.

The calcium-based compound is distributed over the grain boundaries or phase boundaries of the aluminum alloy, and the average size of the grains or phase regions is reduced by inhibiting the movement of grain boundaries or phase boundaries. This is because the calcium-based compound hinders the movement of grain boundaries or phase boundaries. Since the calcium-based compound refines the crystal grains or phase regions, mechanical properties such as strength and elongation, and the like can be improved. The strength of the calcium-based compound as an intermetallic compound is higher than that of the matrix to prevent displacement of the displacement and to increase the strength of the alloy.

For example, 0.1% to 40% by weight of calcium may be added to the aluminum alloy. In the case where the amount of calcium is less than 0.1% by weight, the effect of the aluminum-calcium compound can be ignored. Also, when the amount of calcium is more than 40% by weight, mechanical properties are deteriorated due to an increase in brittleness. Thus, the amount of calcium may be between 10% and 30% by weight, and more preferably between 15% and 30% by weight, preferably between 15% and 25% by weight.

In some cases, it is preferred that the calcium dissolved in the aluminum matrix be as small as possible. For example, if the amount of calcium dissolved in the aluminum matrix is not controlled to less than 500 ppm, the quality of the aluminum melt deteriorates due to bubbles in the aluminum melt. The cast material formed from the aluminum melt thus has a low strength and elongation due to minute voids generated by the bubbles.

Also, when the Mg ₂ S alloy capable of effectively increasing the strength of the aluminum-magnesium-bismuth alloy is suppressed, calcium may have a negative influence on mechanical properties. In these embodiments, it is desirable to control the amount of calcium to be less than the solubility limit, such as 500 ppm. When calcium is directly added to the aluminum melt, it is difficult to repeatedly control the amount of calcium to less than 500 ppm due to the difficulty in accurately controlling calcium loss in the aluminum melt. If this is the case, this problem can be solved by indirect rather than direct calcium addition in the intermediate alloy.

As described above, in the intermediate alloy, a small portion of calcium is dissolved in the matrix, and most of the calcium is present in the form of a calcium-based compound. The calcium-based compound is mainly an intermetallic compound and has a melting point higher than the melting point of aluminum (658 ° C). For example, the melting points of the Al ₂ Ca alloy and the Al ₄ Ca alloy which are aluminum/calcium compounds are 1079 ° C and 700 ° C, respectively, both higher than the melting point of aluminum.

Therefore, even when an intermediate alloy containing calcium present in the matrix and the calcium compound is added to the aluminum alloy, only a small amount of calcium is diluted and supplied to the aluminum matrix, and a large amount of calcium exists in the form of a calcium-based compound. Thus, the aluminum alloy has a structure in which a small amount of calcium is dissolved in the matrix, such as less than 500 ppm, and the calcium-based compound is dispersed on the substrate. Therefore, when the amount of calcium dissolved in the matrix is more than 500 ppm, the problem can be overcome and the mechanical properties of the alloy can be improved by the dispersion of the calcium-based compound.

As described above, the calcium-based compound is interspersed between the fine particles in the aluminum alloy, which increases the strength of the aluminum alloy. The aluminum alloy grains or phase regions of the present invention are finer and have a smaller average size than aluminum alloys which do not have such calcium-based compounds. The refinement of grains or phase regions produced by the calcium-based compound can simultaneously improve strength and elongation.

The method for producing an aluminum alloy according to an embodiment of the present invention is described in detail below. The manufacturing method may include: providing an aluminum alloy containing a calcium-based compound and aluminum; forming a melt in which the intermediate alloy and aluminum are melted and casting the melt.

For example, in order to form a melt having the intermediate alloy and aluminum fusion, aluminum is first melted to form an aluminum melt, and then the intermediate alloy containing a calcium-based compound is added to the aluminum melt and melted. As another example, the melt can also be formed by charging aluminum and an intermediate alloy together in a melting apparatus, such as a furnace, and then heating them together.

Fig. 3 illustrates an embodiment of the method for producing an aluminum alloy of the present invention. Specifically, FIG. 3 is a flow chart illustrating a method of manufacturing an aluminum alloy using a process in which an aluminum melt is first formed, and then an intermediate alloy is added to the aluminum melt, and the intermediate alloy is melted.

As shown in FIG. 3, the manufacturing method may include the following steps: an aluminum melt forming step S11, an intermediate alloy adding step S12, a stirring-resting step S13, a casting step S14, and a cooling step S15.

In step S11, aluminum is placed in a furnace, and the furnace is heated at a temperature ranging from 600 ° C to 900 ° C to form an aluminum melt. In step S11, the aluminum may be any one selected from the group consisting of pure aluminum, an aluminum alloy, and equivalents thereof. The aluminum alloy may be, for example, selected from the group consisting of 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, 7000 series, and 8000 series forged aluminum or 100 series, 200 series, 300 series, 400 series, 500 series, and Any of the 700 series cast aluminum.

Here, the aluminum alloy of each embodiment of the present invention will be more specifically explained. Aluminum alloys have been developed in various types based on their use, and various types of aluminum alloys are classified by the American Aluminum Association standard.

Table 1 shows the composition of the main alloying elements of the alloy series in four numbers and further subdivided by the four names into the modified elements of each alloy series.

The first number represents the alloy series and its main alloying elements; the second number represents 0, which is expressed as a base alloy, such as a modified alloy of 1 to 9; in addition, a representative of a new alloy developed separately The letter is N. For example, 2xxx represents an aluminum-based alloy of the aluminum-copper series, 21xx~29xx is the modified aluminum-copper series base alloy, and 2Nxx is a newly developed alloy other than the association standard.

The third and fourth numbers indicate the purity of aluminum in terms of pure aluminum and alloys. These figures are the names of the alloys used by Alcoa in the past. For example, in the case of pure aluminum, 1080 means that the purity of aluminum is greater than 99.80%, and 1100 represents 99.00% of aluminum. The main components of these aluminum alloys are listed in Table 2 below:

Next, in step S12, the intermediate alloy produced by the above method is added to the aluminum melt. The intermediate alloy may be added in an amount of from about 0.0001 part by weight to about 30 parts by weight based on 100 parts by weight of the aluminum in the step S12. For example, the master alloy can be added in the form of an ingot. Again, for example, the master alloy may be added to other forms such as powders and granules. The size of the intermediate alloy can be appropriately selected depending on the conditions of the melting, and this does not limit the scope of the embodiment.

During the addition of the intermediate alloy, the dissolved calcium and calcium-based compounds contained in the intermediate alloy are added to the aluminum melt. As described above, the calcium-based compound supplied in the aluminum melt may contain at least one of a magnesium-calcium compound, an aluminum-calcium compound, and a magnesium-aluminum-calcium compound.

At this time, a small amount of shielding gas may be additionally supplied to prevent the intermediate alloy from being oxidized. The shielding gas can use conventional sulfur hexafluoride (SF ₆ ), sulfur dioxide (SO ₂ ), carbon dioxide (CO ₂ ), 1,1,1,2-tetrafluoroethane (HFC-134a), magnesium smelting protective fluid (NovecTM 612), an inert gas and its equivalent, or a mixture thereof, thereby suppressing oxidation of the magnesium intermediate alloy.

However, such a shielding gas is not always required in this embodiment. That is, in the case of the magnesium intermediate alloy containing a calcium-based compound, since the oxidation resistance of the magnesium intermediate alloy is improved, the flame resistance can be increased, and impurities such as oxides in the melt do not contain impurities. The conventional magnesium of calcium-based compounds is greatly reduced. Therefore, according to the method for producing an aluminum alloy of the present embodiment, the quality of the melt is remarkably improved in quality due to the greatly improved cleanliness of the aluminum melt even without using a shielding gas.

Then in the stirring-resting step S13, the aluminum melt can be stirred or left standing for a certain period of time. For example, the aluminum melt can be stirred or left to stand for about 1 to 400 minutes. Here, if the stirring and standing time is less than 1 minute, the magnesium intermediate alloy cannot be sufficiently mixed into the aluminum melt. Conversely, if it exceeds 400 minutes, the stirring and standing time of the aluminum melt may not need to be increased.

After the stirring and the standing aluminum melt are substantially completed in step S13, the aluminum melt is cast into a mold of step S14, and after cooling in step S15, the solidified aluminum alloy is separated from the mold. The temperature of the mold in step S14 may be room temperature (for example, 25 degrees Celsius) to 400 degrees Celsius. In the cooling step S15, the aluminum alloy can be separated from the mold after the mold is cooled to room temperature. However, if the aluminum alloy has been fully cured, the aluminum alloy can be separated from the mold even before the temperature reaches room temperature. The casting method will not be described here because the method for producing the magnesium intermediate alloy has been described in detail.

The aluminum alloy thus formed may be selected from the group consisting of 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, 7000 series, and 8000 series forged aluminum, or 100 series, 200 series, 300 series, 500 series, and Any of the 700 series cast aluminum.

As described above, since the cleanliness of the aluminum melt is improved in the case of adding a magnesium intermediate alloy containing a calcium-based compound, the mechanical properties of the aluminum alloy are greatly improved. That is to say, due to the improvement of the melt cleanliness, there are no impurities, such as oxides or inclusions, which may deteriorate the mechanical properties in the casted aluminum alloy, and the internal bubbles in the cast aluminum alloy are also the same. Significantly reduced. Since the interior of the aluminum alloy has a relatively clean state relative to the conventional aluminum alloy, the mechanical properties of the aluminum alloy of the present invention are better than those of the conventional aluminum alloy, so that not only excellent yield strength and tensile strength but also excellent elongation are obtained. rate.

Therefore, although an aluminum alloy having the same magnesium content is produced, the cast aluminum alloy of the present invention has better characteristics due to purification of the quality of the melt.

Similarly, the amount of magnesium lost in the melt is also reduced. Therefore, even if the actual increase amount of the magnesium of the present invention is less than the magnesium content of the conventional method, an aluminum alloy having the same content of magnesium as the conventional aluminum alloy can be economically produced.

Moreover, in the addition of the magnesium intermediate alloy of the present invention to the aluminum melt, the instability of magnesium in the aluminum melt is remarkably improved as compared with the conventional aluminum alloy, and thus it is easier to compare with the conventional aluminum alloy. Increase the magnesium content.

The dissolution of magnesium into aluminum is up to about 15% by weight, and the dissolution of magnesium into aluminum causes an increase in the mechanical properties of aluminum. For example, if magnesium is added to an aluminum alloy of 300 series or 600 series, the strength and elongation of the aluminum alloy will be improved.

However, since the oxide or inclusions generated by magnesium are mixed into the melt due to the high oxidation potential of magnesium, the quality of a conventional aluminum alloy is deteriorated. This problem becomes more serious as the content of magnesium becomes larger, and thus although a protective gas is used, it is very difficult to stably increase the magnesium content added to the aluminum melt.

In contrast, since the magnesium intermediate alloy can be stably added to the aluminum melt in the present invention, it is ensured when the magnesium content in the aluminum alloy is easily increased to increase the magnesium ratio as compared with the conventional method. Its castability. Therefore, since the magnesium intermediate alloy of the present invention is added to the 300 series or 600 series aluminum alloy to suppress the incorporation of oxides or inclusions, the strength and elongation and castability of the aluminum alloy can be improved; Aluminum alloys of the 500 series or 5000 series are also possible.

For example, the aluminum alloy of the present invention can easily increase the amount of magnesium dissolved to 0.1 wt% or more, and also increase the amount of magnesium dissolved to 5 wt% or more, further up to 6 wt% or more, even from 10 wt% to 15 wt%. % solubility limit or more.

The stability of magnesium in aluminum alloys can play an advantageous role in the recycling of waste aluminum alloys. For example, when a recycled waste having a high magnesium content is used in the process of manufacturing an aluminum alloy, an operation for reducing the magnesium content to a desired ratio (hereinafter referred to as "magnesium removal process") is performed. The difficulty and cost of magnesium removal operations increase as the magnesium content requirements decrease.

For example, in the case of 383 aluminum alloy, it is technically easy to reduce the magnesium content to 0.3% by weight, but it is difficult to reduce it to 0.1% by weight. It is also possible to use chlorine to reduce the ratio of magnesium, however the use of chlorine is harmful to the environment, resulting in an increase in cost.

However, since the aluminum alloy of the present invention produced using a calcium-based compound can maintain a magnesium ratio of more than 0.3% by weight, the present invention has technical, environmental, and cost advantages.

Also, the aluminum alloy of the present invention may further comprise a step of increasing a small amount of iron in the above-described manufacturing method, for example, after the step S11 of forming an aluminum melt or after the step S12 of adding a magnesium intermediate alloy. At this time, the amount of iron added is less than that of the conventional method. That is, conventional cast aluminum alloys, for example, in the case of die-cast aluminum alloys, typically cause solder to be broken by the solder between the mold made of iron-based metal and the aluminum cast material. In order to solve this problem, 1.0 to 1.5% by weight of iron has been added to the aluminum alloy during the die casting of the aluminum alloy. However, an increase in iron will cause another problem that deteriorates the corrosion resistance and elongation of the aluminum alloy.

However, the aluminum alloy of the present invention may contain a high ratio of magnesium, and the welding problem caused by conventional molds can be significantly improved compared to conventional alloys after the addition of a relatively small amount of iron. Therefore, the problem of corrosion resistance and elongation reduction occurring in the conventional die cast aluminum alloy casting material can be solved.

The amount of iron added during the aluminum alloy manufacturing process may be less than or equal to 1.0 wt% (greater than 0%), and more strictly less than or equal to 0.2 wt%, relative to the aluminum alloy. Therefore, the aluminum alloy matrix may contain iron of a certain composition.

The characteristics of the aluminum alloy produced by the manufacturing method of the present invention are explained in detail as follows. The aluminum alloy produced by the manufacturing method of the present invention comprises an aluminum matrix and a calcium-based compound present in an aluminum matrix in which magnesium is soluble in the aluminum matrix. Also, the amount of calcium dissolved in the aluminum matrix is less than the solubility limit, for example less than 500 ppm dissolved in the aluminum matrix.

The aluminum matrix may have a plurality of crystal domains, the plurality of crystal domains forming boundaries and spaced apart from each other, and the calcium-based compound may be present on or within the crystal domains. The aluminum matrix may be defined as a metal structure, the aluminum is the main element in the metal structure, and other alloying elements are dissolved in the metal structure, or other compounds other than the calcium-based compound form a single phase.

The plurality of crystal domains separated from each other may be a plurality of crystal grains conventionally separated by grain boundaries, or a plurality of phase regions formed by phase boundaries having two or more different phases.

The aluminum alloy of the present invention can be modified in mechanical properties by the calcium-based compound formed in the intermediate alloy. As described above, when an intermediate alloy is added to the aluminum melt, a calcium-based compound contained in the intermediate alloy is also added to the aluminum melt. The calcium-based compound is an intermetallic compound formed by the reaction of calcium and other metal elements and has a higher melting point than aluminum.

Therefore, in the case where an intermediate alloy containing a calcium-like compound is added to the aluminum melt, the calcium-based compound can be maintained inside the melt without being melted. And in the case of casting the aluminum melt to produce an aluminum alloy, the calcium-based compound may be contained in the aluminum alloy.

The calcium-based compound can be dispersed and distributed between the fine particles of the aluminum alloy. The calcium-based compound is a mesometallic compound which is a high-strength material compared to the aluminum matrix, and therefore, the strength of the aluminum alloy can be increased due to the dispersion distribution of such a high-strength material.

At the same time, the calcium-based compound provides a nucleation site during the phase change of the aluminum alloy from the liquid phase to a solid phase. That is to say, during the solidification of the aluminum alloy from the liquid phase to the solid phase, the phase change is carried out during grain formation and growth. Since the calcium-based compound itself acts as a heterogeneous nucleation region, the nucleation process in which the phase changes to the solid phase starts from the interface between the calcium-based compound and the liquid phase, so that the solid phase grains nucleate around the calcium-based compound. Growing.

In the case where the calcium-based compounds are distributed in a dispersed manner, the solid phases grown at the interface of each of the calcium-based compounds meet to form a boundary, and these boundaries may form grain boundaries or phase boundaries. Therefore, if the calcium-based compound is used as a nucleation site, the calcium-based compound exists inside the crystal grain or phase region, and the crystal grain or phase region appears finer than the case where the calcium-based compound does not exist.

Also, the calcium-based compound may be distributed on the grain boundary between the crystal grains or the phase boundary between the phase regions. This is because such a boundary is open and has relatively high energy relative to the inner region of the grain or phase region, and thus serves as an advantageous location for grain formation and growth of the calcium-based compound.

Therefore, in the case where the calcium-based compound is distributed at the grain boundary or phase boundary of the aluminum alloy, since the calcium-based compound hinders the movement of the grain boundary or the phase boundary, the average size of the crystal grain or the phase region passes through the suppression grain boundary or phase. The movement of the boundary is reduced.

Therefore, the aluminum alloy of the present invention can make crystal grains or phase regions smaller and have an average size smaller than that of an aluminum alloy in which no calcium-based compound is present. The refinement of the grains or phase regions by the calcium-based compound can simultaneously improve the strength and elongation of the alloy.

Similarly, the aluminum substrate can be selected from 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, 7000 series, and 8000 series forged aluminum or 100 series, 200 series, 300 series, 400 series, 500 series. And one of the 700 series cast aluminum.

In the following, experimental groups will be enumerated in order to understand the present invention. The experimental groups described below are only used to help the understanding of the invention and are not intended to limit the invention.

Table 3 shows the casting properties, the aluminum alloy produced by adding the intermediate alloy of calcium to aluminum (experiment group 1) and the aluminum alloy produced by adding pure magnesium and containing no calcium (control group 1). The intermediate alloy in the experimental group 1 used a magnesium-aluminum alloy as a master batch, and the weight ratio of calcium to the master batch was 0.3.

Specifically, the aluminum alloy of the experimental group 1 was produced by adding 305 g of a magnesium intermediate alloy to 2,750 g of aluminum, and the aluminum alloy of the control 1 was made by adding 305 g of pure magnesium to 2,750 g of aluminum. Made by.

Referring to Table 3, it was found that the amount of impurities (the amount of scum) floating on the surface of the melt in the magnesium intermediate alloy (experimental group 1) was small relative to the addition of pure magnesium (control group 1). Similarly, the aluminum alloy formed by adding the magnesium intermediate alloy (experimental group 1) had more magnesium content than the addition of pure magnesium (control group 1). Therefore, the manufacturing method of the present invention greatly reduces the loss of magnesium relative to the method of producing pure magnesium.

Similarly, it was found that the experimental group 1 in which the magnesium intermediate alloy was added was superior to the control group 1 in which pure magnesium was added, and the liquid fluidity of the melt and the hardness of the aluminum alloy were more excellent.

Figure 4 (a) shows the observation of the electron probe microanalyzer (EPMA) of the microstructure of the aluminum alloy of the experimental group 1, and the figures (b) to (d) of the figure 4 show the differences of aluminum, calcium and magnesium. Use the mapping results observed by EPMA.

Referring to Figures 4(b) to (d), calcium, magnesium and aluminum were detected at the same position of the aluminum substrate, and thus it was known that calcium reacted with magnesium and aluminum to form a calcium-based compound.

Fig. 5 is a comparison result of the surface of the cast material of the aluminum alloy of the experimental group 1 and the control group 1. Referring to Fig. 5, the surface of the aluminum alloy casting material of the experimental group 1 can be confirmed as shown in Fig. 5a, for example, the surface of the aluminum alloy casting material of the example 1 shown in Fig. 5b is cleaner. This is because the calcium added to the magnesium intermediate alloy improves the castability. That is to say, the aluminum alloy to which pure magnesium is added (control group 1) has a burning mark on the surface thereof due to oxidation of pure magnesium during the casting process, however, the sintering of the cast aluminum alloy is suppressed by the use of the magnesium intermediate alloy added with calcium. The phenomenon of burning was obtained to obtain a cleaner aluminum alloy surface (Experiment Group 1).

Therefore, it was observed that the melt quality of the magnesium intermediate alloy was improved as compared with the melt quality of the pure magnesium, and the casting properties were accordingly improved.

Table 4 shows the mechanical properties of the experimental group 2 and the control group 2, and the experimental group 2 is an aluminum alloy manufactured by adding a magnesium intermediate alloy, and the magnesium intermediate alloy is made of the commercially available 6061 alloy of the aluminum alloy. Calcium was added, while control 2 was 6061 alloy. After casting, the sample of Example 2 was extruded and a T6 heat treatment was performed. The data of the control group 2 is referred to the value in the ASM standard (T6 heat treatment data).

As shown in Table 5, it can be seen that the tensile strength and yield strength of the aluminum alloy of the experimental group 2 are higher than those of the aluminum alloy available in the control group 2, and the elongation is greater than or equal to that available in the control group 2 on the market. Aluminum alloy. In general, the elongation will be relatively reduced as the strength of the alloy increases. However, the aluminum alloy of the present invention has a desirable property that the elongation and strength can be simultaneously increased. This result is related to the improved cleanliness of the aluminum alloy melt as described above.

Figure 6 shows the results of microstructure observations prepared in Experimental Group 2 and Control Group 2. Referring to Fig. 6, it is understood that the crystal grains of the aluminum alloy of the experimental group 2 in Fig. 6a are more refined than those of the aluminum alloy available in the control group 2 shown in Fig. 6b.

The grain refinement of the aluminum alloy in the experimental group 2 is considered to be suppressed by the calcium-based compound distributed at the grain boundary due to the growth of the grain boundary or the calcium-based compound acts as a nucleation site during the solidification process. Such grain refinement is considered to be one of the reasons why the aluminum alloy of the present invention has excellent mechanical properties.

S1. . . Masterbatch melt forming step

S2. . . Additive addition step

S3. . . Stirring-resting step

S4‧‧‧ casting steps

S5‧‧‧ Cooling step

S11‧‧‧ Aluminum melt forming step

S12‧‧‧ intermediate alloy addition step

S13‧‧‧Stirring-Standing Procedure

S14‧‧‧ casting steps

S15‧‧‧ Cooling step

Fig. 1 is a flow chart showing a method of producing a magnesium intermediate alloy added to an aluminum melt in the aluminum alloy manufacturing process of the embodiment of the present invention.

Fig. 2 shows the results of analysis of calcium-based compound components in a magnesium intermediate alloy.

Figure 3 is a flow chart illustrating the method of manufacturing an aluminum alloy of the present invention.

Fig. 4 is a result of analysis of composition of an aluminum alloy containing a magnesium intermediate alloy in which a calcium is added to the magnesium intermediate alloy.

Fig. 5 is a view showing a surface image of a calcium-containing intermediate alloy added to a casting material for an aluminum alloy, and a surface image of a casting material for adding an aluminum alloy of pure magnesium in the embodiment of the present invention.

Fig. 6 is a view showing the microstructure observation of the aluminum alloy produced by adding the magnesium intermediate alloy to the alloy 6061, and the microstructure observation result of the alloy 6061.

S1. . . Masterbatch melt forming step

S2. . . Additive addition step

S3. . . Stirring-resting step

S4. . . Casting step

S5. . . Cooling step

Claims (34)

An aluminum alloy manufacturing method, comprising: providing an intermediate alloy of aluminum and a calcium-based compound; forming a melt, the intermediate alloy and aluminum are melted in the melt; and casting the melt to form the aluminum An alloy having at least a calcium element derived from the intermediate alloy; wherein the intermediate alloy is formed by adding calcium to a master batch, which is added in an amount of 0.0001 part by weight based on 100 parts by weight of the master batch. 100 parts by weight of calcium, wherein the masterbatch based on 100 parts by weight is added with calcium greater than the solubility limit and less than or equal to 100 parts by weight, and the masterbatch contains pure magnesium or a magnesium having calcium as an alloying element alloy. An aluminum alloy manufacturing method, the method comprising: providing an intermediate alloy of aluminum and a calcium-based compound; forming a melt, the intermediate alloy and aluminum are melted in the melt; and casting the melt to form the aluminum An alloy having at least a calcium element derived from the intermediate alloy; wherein the intermediate alloy is formed by adding calcium to a master batch containing pure aluminum or an aluminum alloy, and the intermediate alloy is attached to the master batch A calcium amount greater than the dissolution limit of the intermediate alloy is added to obtain the calcium-based compound. The method for producing an aluminum alloy according to claim 1 or 2, further comprising adding iron of less than or equal to 1.0% (greater than 0%) by weight. The method for manufacturing an aluminum alloy according to claim 3, wherein the iron is added The addition amount is less than or equal to 0.2% by weight. The method for producing an aluminum alloy according to claim 1 or 2, wherein the aluminum based on 100 parts by weight provides an intermediate alloy of between 0.0001 part by weight and 30 parts by weight. The method for producing an aluminum alloy according to claim 1 or 2, wherein the forming a melt step comprises: forming an aluminum melt by melting aluminum; and adding the intermediate alloy to the aluminum melt, and The intermediate alloy melts. The method for producing an aluminum alloy according to claim 1 or 2, wherein the forming of a melt step comprises: melting the intermediate alloy together with aluminum. The method for producing an aluminum alloy according to claim 1 or 2, wherein the step of producing the intermediate alloy comprises: forming a masterbatch melt by melting the master batch; and adding calcium to the masterbatch melt. The method for producing an aluminum alloy according to claim 1 or 2, wherein the step of producing the intermediate alloy comprises: melting the master batch together with calcium. The method for producing an aluminum alloy according to claim 1, wherein the master batch contains at least one of magnesium and aluminum, and the calcium-based compound is formed by reacting calcium with magnesium or aluminum in the master batch. The method for producing an aluminum alloy according to claim 2, wherein the calcium base The compound is formed by the reaction of calcium with aluminum in the masterbatch. The method for producing an aluminum alloy according to claim 10, wherein the calcium-based compound comprises at least one of a magnesium-calcium compound, an aluminum-calcium compound, and a magnesium-aluminum-calcium compound. The method for producing an aluminum alloy according to claim 12, wherein the magnesium-calcium compound comprises a Mg ₂ Ca alloy. The method for producing an aluminum alloy according to claim 12, wherein the aluminum-calcium compound comprises at least one of an Al ₂ Ca alloy and an Al ₄ Ca alloy. The method for producing an aluminum alloy according to claim 14, wherein the magnesium-aluminum-calcium compound comprises a (Mg,Al) ₂ Ca alloy. The method for producing an aluminum alloy according to claim 1 or 2, wherein the aluminum is pure aluminum or an aluminum alloy. An aluminum alloy manufactured by the method for producing an aluminum alloy according to any one of claims 1 to 16. The aluminum alloy according to claim 17, wherein the aluminum alloy comprises one selected from the group consisting of 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, 7000 series, and 8000 series forged aluminum or 100 series, 200 At least one of the series, 300 series, 400 series, 500 series, and 700 series cast aluminum. An aluminum alloy comprising: an aluminum matrix; and a calcium-based compound present in the aluminum matrix; Wherein magnesium is dissolved in the aluminum matrix, the amount of calcium dissolved in the aluminum matrix is less than a solubility limit, and wherein the magnesium intermediate alloy is melted by adding a magnesium intermediate alloy containing the calcium-based compound to the aluminum matrix. In the body, the intermediate alloy is prepared by adding calcium to a base material melt, and the base material includes aluminum or magnesium. The aluminum alloy according to claim 19, wherein the amount of calcium dissolved in the aluminum matrix is less than or equal to 500 ppm. The aluminum alloy according to claim 19, further comprising iron of less than or equal to 1.0% by weight (greater than 0%). The aluminum alloy according to claim 21, wherein the amount of iron is less than or equal to 0.2% by weight. The aluminum alloy according to claim 19, wherein the aluminum matrix has a plurality of crystal domains, and the plurality of crystal domains form a boundary and are spaced apart from each other, wherein the calcium-based compound exists on the boundary. The aluminum alloy according to claim 19, wherein the aluminum matrix has a plurality of crystal domains, and the plurality of crystal domains form boundaries and are spaced apart from each other, wherein the calcium-based compound is present in the crystal domains. The aluminum alloy according to claim 23, wherein the plurality of crystal domains are crystal grains, and the boundary is a grain boundary. The aluminum alloy according to claim 23, wherein the plurality of crystal domains are phase regions formed by different phases, and the boundary is a phase boundary. The aluminum alloy according to claim 19, wherein the calcium-based compound comprises There are at least one of a magnesium-calcium compound, an aluminum-calcium compound, and a magnesium-aluminum-calcium compound. The aluminum alloy according to claim 27, wherein the magnesium-calcium compound comprises a Mg ₂ Ca alloy. The aluminum alloy according to claim 27, wherein the aluminum-calcium compound comprises at least one of an Al ₂ Ca alloy and an Al ₄ Ca alloy. The application of the alloy of the scope of patent 27, wherein the magnesium - aluminum - calcium compound contains a (Mg, Al) ₂ Ca alloy. The aluminum alloy according to claim 27, wherein the aluminum matrix comprises one selected from the group consisting of 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, 7000 series, and 8000 series forged aluminum or 100 series, 200 At least one of the series, 300 series, 400 series, 500 series, and 700 series cast aluminum. The aluminum alloy according to claim 23, wherein the aluminum alloy has a crystal domain having an average size smaller than a crystal grain average size of an aluminum alloy produced under the same conditions without a calcium-based compound. The aluminum alloy according to claim 19, wherein the aluminum alloy has a tensile strength greater than that of an aluminum alloy produced under the same conditions without a calcium-based compound. The aluminum alloy according to claim 19, wherein the tensile strength of the aluminum alloy is greater than the tensile strength of the aluminum alloy produced under the same conditions without the calcium-based compound, and the elongation is greater than or equal to the same condition. The elongation of an aluminum alloy without a calcium-based compound.