ALUMINUM ALLOY AND MANUFACTURING METHOD THEREOF

Abstract

According to the present invention, an aluminum alloy comprises 18 to 50 parts by weight of Zinc (Zn), 0.05 to 5 parts by weight of Copper (Cu), 0.001 to 0.3 parts by weight of crystal micronization elements which are at least one of vanadium (V), zirconium (Zr), titanium (Ti) and Boron (B), the rest being aluminum (Al) and other unavoidable impurities, based on the total weight of the alloy.

Claims

1. An aluminum alloy comprising: 18 to 50 parts by weight of Zinc (Zn); 0.05 to 5 parts by weight of Copper (Cu); 0.001 to 0.3 parts by weight of crystal micronization elements which is at least one of vanadium (V), zirconium (Zr), titanium (Ti) and Boron (B); and the rest being aluminum (Al) and other inevitable impurities, based on the total weight of the alloy.

2. The aluminum alloy of claim 1, wherein a tensile strength in 230 to 450 MPa and an elongation in the cast state is 2.75 to 20%.

3. The aluminum alloy of claim 2, wherein a tensile strength in the cast state is more than 310 MPa.

4. The aluminum alloy of claim 2, wherein the elongation in the cast state is more than 10%.

5. The aluminum alloy of claim 1, wherein the micronization elements comprises at least one of titanium and boron in the range of 0.001 to 0.2 parts by weight, based on the total weight of the alloy.

6. The aluminum alloy of claim 5, wherein the micronization elements further comprises 0.01 to 0.05 parts by weight of zirconium, based on the total weight of the alloy.

7. The aluminum alloy of claim 5, wherein the micronization elements further comprises 0.005 to 0.05 parts by weight of vanadium, based on the total weight of the alloy.

8. The aluminum alloy of claim 1, wherein a yield strength in the cast state is more than 250 MPa.

9. A method for manufacturing an aluminum alloy comprising: the step of manufacturing an alloy molten comprising 18 to 50 parts by weight of Zinc (Zn), 0.05 to 5 parts by weight of Copper (Cu), 0.001 to 0.3 parts by weight of micronization elements which are at least one of vanadium (V), zirconium (Zr), titanium (Ti) and Boron (B), and the rest being aluminum (Al) and other unavoidable impurities based on the total weight of the alloy; and the step for casting the alloy molten.

10. The method for manufacturing an aluminum alloy of claim 9, further comprising the step of forming a solid solution by heat-treating the cast alloy molten at a temperature of 150 to 500° C.

11. The method for manufacturing an aluminum alloy of claim 10, further comprising the step of generating discontinuous precipitates by aging treatment the alloy molten with the solid solution at a temperature of 120 to 200° C.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0029] FIG. 1 is a flowchart illustrating a method for manufacturing an aluminum alloy according to an embodiment of the present invention.

[0030] FIG. 2 and FIG. 3 are graphs illustrating a measurement result of mechanical physical properties of an aluminum alloy according to an experimental example and a comparative example of the present invention.

[0031] FIG. 4 to FIG. 6 are images of optical microscopy (called OM as below) illustrating an interface of an aluminum alloy manufactured according to a comparative example of the present invention.

[0032] FIG. 7 to FIG. 15 are images of OM illustrating an interface of an aluminum alloy manufactured according to an experimental example of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0033] According to an embodiment of the present invention, an aluminum alloy comprises 18 to 50 parts by weight of Zinc (Zn), 0.05 to 5 parts by weight of Copper (Cu), crystal micronization elements which is at least one of vanadium (V), zirconium (Zr), titanium (Ti) and Boron (B) in the amount of 0.001 to 0.3 parts by weight, and the rest being aluminum (Al) and other inevitable impurities, based on the total weight of the alloy.

[0034] Zinc (Zn) effectively increases tensile strength and hardness. According to an embodiment of the present invention, an aluminum alloy comprises 18 to 50 parts by weight of zinc based on the total weight of the alloy. While it is not limited thereto, the effect of increasing tensile strength is insignificant if the content of zinc is less than 18 parts by weight and a casting property is lowered and may cause hot shortness, if the content of zinc is more than 50 parts by weight,

[0035] The zinc content may be 20 to 50 parts by weight, 20 to 45 parts by weight, 20 to 40 parts by weight, 30 to 50 parts by weight, 30 to 45 parts by weight or 30 to 40 parts by weight, but it is not limited thereto. It may be suitable for the zinc content in the range of 30 to 45 parts by weight, based on the total weight of the alloy, though it is not limited thereto, Copper (Cu) is added for increasing strength. The addition of copper to the aluminum alloy reduces the size of the zinc particle during cooling after the heat-treatment, thereby significantly reducing the distance between the particles.

[0036] In an embodiment of the present invention, copper (Cu) is incorporated in zinc to lower the interface energy on a Zn precipitate phase/an Al matrix phase. As the interface energy on the precipitation phase and the matrix phase decreases, the average size of precipitates decreases. Thus, the addition of copper reduces the average size of the precipitate zinc. As a result, the spacing between the zinc particles is greatly reduced and the strength of the cast alloy is increased.

[0037] In an aluminum alloy for casting according to the present invention, copper is added in the amount of 0.05 to 5 parts by weight based on the total weight of the alloy. If the zinc content is less than 0.05 parts by weight, the effect of increasing tensile strength is insignificant, and if the zinc content is more than 5 parts by weight, the casting property is lowered and may cause the hot shortness, though it is not limited thereto.

[0038] The content of zinc may be in the amount of 0.05 to 5 parts by weight, 0.05 to 4 parts by weight, 0.05 to 3 parts by weight, 0.05 to 2 parts by weight, 0.1 to 5 parts by weight, 0.1 to 4 parts by weight, 0.1 to 3 parts by weight, 0.1 to 2 parts by weight, 0.5 to 5 parts by weight, 0.5 to 4 parts by weight, 0.5 to 3 parts by weight, 0.5 to 2 parts by weight, 1 to 5 parts by weight, 1 to 4 parts by weight, 1 to 3 parts by weight, 1 to 2 parts by weight, 2 to 5 parts by weight, 2 to 4 parts by weight, 2 to 3 parts by weight, 3 to 5 parts by weight or 3 to 4 parts by weight, though it is not limited thereto.

[0039] It may be suitable for the copper content in the range of 1 to 4 parts by weight, based on the total weight of the alloy, but it is not limited thereto,

[0040] The aluminum alloy of the present invention may have at least one of a diameter and a length of a Zn phase in an Al base of 10 to 100 nm. As described above, according to the present invention, if copper is added to the aluminum alloy, the average size of zinc which is a precipitate phase decrease. As a result, the distance between the zinc particles is greatly reduced and the strength of the cast alloy is increased. Though it is not limited thereto, if at least one of the diameter and the length of the Zn phase in the Al matrix is less than 10 nm or exceeds 100 nm, the increase in the strength of the alloy due to the addition of copper may be insignificant.

[0041] Crystal micronization elements expands the whole interface area and is added for expanding the whole area of the interface discontinuous precipitates. The addition of crystal micronization elements makes the discontinuous precipitates increased, the mechanical property of the aluminum alloy improved and the elongation optimized.

[0042] According to an embodiment of the present invention, the aluminum alloy comprises 0.001 to 0.3 parts by weight of crystal micronization elements, based on the total weight of the alloy. Though it is not limited thereto, if the content of crystal micronization elements is less than 0.001 parts by weight, the improvement effect of the mechanical property and the elongation is insignificant and also, if the content of crystal micronization elements exceeds 0.3 parts by weight, the mechanical property may possibly be decreased instead.

[0043] The content of crystal micronization elements may be 0.001 to 0.3 parts by weight, 0.002 to 0.2 parts by weight, and 0.01 to 0.1 parts by weight, but it not limited thereto. Besides, according to an embodiment of the present invention, the aluminum alloy may comprise at least one of titanium and boron in the amount of 0.001 to 0.2 parts by weight, 0.005 to 0.1 parts by weight or 0.01 to 0.02 parts by weight, based on the total weight of an aluminum alloy.

[0044] Moreover, according to an embodiment of the present invention, the aluminum alloy may comprise at least one of zirconium and vanadium in the amount of 0.005 to 0.3 parts by weight, 0.01 to 0.2 parts by weight or 0.025 to 0.05 parts by weight, based on the total weight of an aluminum alloy.

[0045] Additionally, according to an embodiment of the present invention, the aluminum alloy may comprise 0.005 to 0.02 parts by weight of titanium, 0.001 to 0.004 parts by weight of boron and 0.025 to 0.05 parts by weight of vanadium, based on the total weight of an aluminum alloy. According to an embodiment of the present invention, the aluminum alloy further comprises at least one of magnesium weighing more than 0 and less than 1 parts, and silicon weighing more than 0 and less than 0.5 parts, based on the total weight of an aluminum alloy.

[0046] According to an embodiment of the present invention, magnesium (Mg) may be supplementally added for increasing tensile strength and hardness. According to an embodiment of the present invention, magnesium may be added in the amount of more than 0 and less than 1 parts by weight, based on the total weight of the aluminum alloy, if the content of magnesium is more than 1 parts by weight, it may cause crystalline corrosion, stress corrosion, etc. and may cause the reduction of erosion resistance and the rapid reduction of elongation.

[0047] The content of magnesium may be 0.1 to 0.9 parts by weight, 0.1 to 0.7 parts by weight, 0.1 to 0.5 parts by weight, 0.1 to 0.3 parts by weight, 0.2 to 0.9 parts by weight, 0.2 to 0.7 parts by weight, 0.2 to 0.5 parts by weight, or 0.2 to 0.3 parts by weight, but it is not limited thereto. The content of magnesium may be preferably in the range of 0.1 to 0.3 parts by weight, but it is not limited thereto.

[0048] In one other embodiment of the present invention, silicon may be added for improving the casting property and upgrading the mechanical property. According to an embodiment of the present invention in the aluminum alloy, silicon is added in the amount of more than 0 and less than 0.5 parts by weight, based on the total weight of the aluminum alloy. If the content of silicon exceeds 0.5 parts by weight, it may cause the elongation to drop sharply without increasing the strength.

[0049] The content of silicon may be 0.05 to 0.4 parts by weight, 0.05 to 0.3 parts by weight, 0.05 to 0.2 parts by weight, 0.05 to 0.1 parts by weight, 0.1 to 0.4 parts by weight, 0.1 to 0.3 parts by weight, or 0.1 to 0.2 parts by weight, but it is not limited thereto. The content of silicon is preferably 0.05 to 0.2 parts by weight based on the total weight of the alloy.

[0050] According to an embodiment of the present invention, the aluminum alloy may have tensile strength of 310, 320, 340, 350 or more than 360 MPa in the cast state.

[0051] Moreover, according to an embodiment of the present invention, the aluminum alloy may have yield strength of 250, 260, 270 or more than 290 MPa in the cast state.

[0052] Additionally, according to an embodiment of the present invention, the aluminum alloy may have the elongation of 2.75, 5, 10, 11 or more than 13% in the cast state.

[0053] FIG. 1 is a flowchart roughly illustrating the method of manufacturing the aluminum alloy according to an embodiment of the present invention. Referring to FIG. 1, the manufacturing method depending on an embodiment will be explained in detail as follows.

[0054] According to an embodiment of the present invention, the method of manufacturing an aluminum alloy comprises a step of manufacturing the alloy molten including 18 to 50 parts by weight of zinc, 0.05 to 5 parts by weight of copper, micronization elements which is at least one of vanadium, zirconium, titanium and boron in the amount of 0.001 to 0.2 parts by weight, the best being aluminum, and other unavoidable precipitates inevitable impurities (S100) based on the total weight of the aluminum alloy, a step of casting the alloy molten (S200), a step of forming a solid solution by heat-treating the cast alloy molten (S300) and a step of forming the discontinuous precipitates by aging treatment the aluminum alloy with the solid solution (S400).

[0055] First, alloy materials for casting are prepared and the alloy molten are manufactured (S100). More specifically, based on the total weight, the alloy molten containing 18 to 50 parts by weight of zinc, 0.05 to 5 parts by weight of copper, at least one of micronization elements which are vanadium, zirconium, titanium, and boron in the amount of 0.001 to 0.2 parts by weight, the rest being aluminum and other unavoidable impurities is manufactured. When the manufacturing process is in progress, the step of manufacturing the alloy molten (S100) is performed at the temperature of 650 to 750° C., and degassing process may be carried out after the alloy is completely melted.

[0056] Subsequently, the manufactured alloy molten is cast by injecting the manufactured alloy molten in a mold or a sand mold (S200). Therefore, according to an embodiment of the present invention, a casting manufactured from the alloy is provided.

[0057] Next, a solid solution is formed after an aluminum alloy is heat-treated (S300). At this time, the heat-treatment may be homogenization treatment and/or solution treatment. Due to the generation of the solid solution, the aluminum alloy becomes a state containing the solid solution.

[0058] The range of the temperature to generate a solid solution may be 150 to 500° C. The temperature range can be determined in consideration of the maximum employment limit temperature at which the liquid phase of the aluminum alloy is not formed and the solid solution can be formed. In the case of an aluminum alloy, discontinuous precipitates are not produced because a poly-phase is formed without forming a single phase at a temperature exceeding 500° C. The step of forming a solid solution may be performed by heating for 30 minutes or more. Although it is not limited thereto, the heat treatment is preferably carried out at 400° C. for 120 minutes to form a solid solution.

[0059] Subsequently, discontinuous precipitates using the aluminum alloy including a solid solution are forcibly formed (S400). The step of forcibly forming discontinuous precipitates is a step of forming discontinuous precipitates or lamellar precipitates in the alloy and then the aluminum alloy containing a solid solution is performed by aging treatment to forcibly form discontinuous precipitates or lamellar precipitates of 5% or more per unit area. The age-treatment may be performed at 120 to 200° C. which is lower than that of forming the solid solution. For example, the age-treatment may be performed at 160° C. The age-treatment may be performed for 5 minutes to 400 minutes. For instance, if the alloy material includes a precipitation-accelerating metal, water quenching or air quenching may be performed after the solid solution is formed. By age-treatment for more than 2 hours, discontinuous precipitates may be forcibly produced. As described above, water quenching or air quenching before the age-treatment possibly make oriented type precipitates formed by lowering temperature speed very quickly. In the case that the temperature is lowered slowly, even if the discontinuous precipitates or lamellar precipitates are forcibly formed, these precipitates may not be oriented.

[0060] After the discontinuous precipitates or the lamellar precipitates are forcibly formed as described above, the aluminum alloy containing the precipitates is calcined to form oriented precipitates (S500).

[0061] The step of forming oriented precipitates is a step of artificially orienting the forcibly formed discontinuous precipitates, and may be carried out through rolling, drawing and/or extrusion. A drawing ratio, which is a reduction rate of the cross-sectional area, may be more than 50%. As the drawing ratio increases, the thickness of the oriented precipitates itself and the distance between the oriented precipitates may decrease, and the tensile strength may be improved. The step of orientation (S500) may be performed in a liquid nitrogen atmosphere. If the step of orientation is performed in a liquid nitrogen atmosphere, the heat generated in the step for orientation may be minimized to facilitate orientation alignment of the discontinuous precipitates, resulting in increased tensile strength.

[0062] As described above, during the manufacturing process, the aluminum alloy of the present invention forcibly forms discontinuous precipitates and lamellar precipitates, includes oriented precipitates formed from those, and may be provided as a metal material which has excellent physical properties such as tensile strength, elongation and conductivity improved simultaneously.

[0063] Therefore, the aluminum alloy of the present invention can improve both tensile strength and elongation at the same time only by casting, and can further improve strength and elongation if being processed so that it can valuably be used for the production of casting and processing materials.

[0064] More particularly, according to the present invention, the aluminum alloy is expected to reduce noise and vibration, if it is used for automobile materials so that it is usefully applied for short absorber covers, B fillers and joint nodes of automobiles, various kinds of brackets of driving system, and materials of mount and support.

Experimental Example

[0065] Hereinafter, the present invention will be described in more detail with reference to specific production examples, comparative examples and their property evaluation results of the present invention.

[0066] Table 1 shows contents of experimental examples and comparative examples of the aluminum alloy according to the present invention.

[0067] The aluminum alloy of the present invention, having the content of each element in Table 1 was cast by a compact 50 Kg electric furnace melting and high-frequency induction melting. All alloys were cast using a 99.9% pure raw material and master alloy. Using an electric furnace, 5 kg of each specimen was melted and temperature was maintained at 700° C. After complete melting, a degassing operation was performed with Ar gas for 10 minutes. After molten state was maintained for 10 minutes, it was filled into a sand mold.

[0068] In five minutes after filling, the ingot was taken out of the mold. Homogenization treatment was carried out at 450° C. for 120 minutes in order to remove impurities generated during casting. Subsequently, annealing was performed at a reduction rate of 20% at 400° C. every 15 minutes to perform swaging to a total cold processing area reduction rate of 75%. After 1 hour, the swaged result was subjected to solution treatment at 400° C. for 3 hours, followed by water-quenching treatment. In only the case of the experimental examples of 2 and 3, the swaged result was subjected to solution treatment at 380° C. and 390° C. respectively for 1.5 hours, followed by water-quenching treatment. Then, precipitation treatment for producing discontinuous precipitates was carried out at 160° C. for 360 minutes.

TABLE-US-00001 TABLE 1 Solution Aging Tensile Yield Treatment Treatment strength Strength Elongation Al Zn Cu Ti B Zr V (° C.) (° C.) (Mpa) (Mpa) (%) Comparative Bal. 33 0.8 — — — — 400 160 342.5 283.5 11.05 example1 Comparative Bal. 33 2 — — — — 400 160 368.5 301 8.5 example2 Comparative Bal. 33 1 — — — — 400 160 349.5 294.6 8.7 example3 Experimental Bal. 33 1 0.01 0.002 — 400 160 361.7 292.4 13.1 example1 Experimental Bal. 33.3 1 0.01 0.002 — 0.01 380/390 160 351 277 13.5 example 2 Experimental Bal. 33.3 1 0.01 0.002 0.025 — 380/390 160 362.3 291.7 11.8 example 3 Experimental Bal. 33.1 1 0.01 0.002 — — 400 160 346.3 281 11.3 example 4 Experimental Bal. 33.1 1 0.01 0.002 — 0.01 400 160 358.3 290 15.6 example 5 Experimental Bal. 33.1 1 0.01 0.002 — 0.05 400 160 351.3 284.3 12.4 example 6 Experimental Bal. 33.1 1 0.01 0.002 — 0.01 400 160 353.3 292.9 12.9 example 7 Experimental Bal. 33.1 1 0.01 0.002 —  0.025 400 160 355.3 293 13.8 example 8 Experimental Bal. 33.1 1 0.01 0.002 — 0.05 400 160 350.7 284 13.2 example 9 Experimental Bal. 33.1 1 0.01 0.002 —  0.075 400 160 358.7 286.3 11.8 example 10 Experimental Bal. 33.1 1 0.01 0.002 — 0.1  400 160 363.3 295.3 11.8 example 11 Experimental Bal. 33.1 1 0.01 0.002 — 0.15 400 160 362.3 296.7 11.3 example 12

[0069] Evaluation of Mechanical Properties of Cast State

[0070] A specimen has been manufactured in accordance with KS B 0801, and tensile strength, yield strength and elongation have been measured in accordance with the test method of tensile strength of metal material, KS B 0802. FIG. 2. and FIG. 3. are graphs illustrating tensile strength, yield strength and elongation of alloys in the cast state, which are manufactured from an experimental example and a comparative example. As shown in FIG. 2. and FIG. 3, experimental examples of the present invention containing crystal micronization elements have equivalent levels of tensile strength and yield strength to the ones of comparative examples, and at the same time have remarkable elongation.

[0071] OM images magnified respectively 50 times, 200 times and 500 times are of alloy specimens of comparative example 3 in FIG. 4 to FIG. 6, of comparative example 1 in FIG. 7 to FIG. 9, of comparative example 4 in FIG. 10 to FIG. 12, of comparative example 5 in FIG. 13 to FIG. 15. It is noticed that as shown in FIG. 7 to FIG. 15, crystal grains of the experimental examples of the present invention have more micronized than the ones of the comparative examples of FIG. 4. to FIG. 6. Particularly, as shown in FIG. 13 to FIG. 15, the addition of vanadium leads to enhance the micronizing effect of crystal grains.

[0072] The images of FIG. 7 to FIG. 15 have illustrated that discontinuous precipitation (DP) in which a composition and crystal orientation discontinuously change with grain boundary as a boundary have been created because continuous precipitation (CP) small and evenly spread in the whole specimen, grain boundary diffusion and grain boundary migration cause irregular extraction. Discontinuous precipitates created like the above reduce inclusion formed in the interface, develop stable crystal grain interface, and eventually improve elongation of the aluminum alloy. An embodiment of the present invention has been described hereinabove, and the present disclosure may be variously modified and altered with addition, change, deletion or supplement of elements by those skilled in the art to which the present disclosure pertains without departing from essential features of the present disclosure. This is also included in the scope of the present invention's spirit.

[0073] The object of the present invention is not limited by the features described above, other unmentioned tasks to solve should be clearly understood by the skilled artisan with the details below.

[0074] The scope of the present disclosure should be determined by the claims.