High elasticity hyper eutectic aluminum alloy and method for manufacturing the same

Abstract

Disclosed herein is a high-elasticity hypereutectic aluminum alloy, including: titanium (Ti) and boron (B), wherein a composition ratio of Ti: B is 3.5 to 5:1, boron (B) is included in an amount of 0.5 to 2 wt %, and both Al.sub.3Ti and TiB.sub.2 are included as reinforcing agents.

Claims

1. A high-elasticity hypereutectic aluminum alloy, comprising: copper (Cu) in an amount of about 4.5 wt %, magnesium (Mg) in an amount of about 0.60 wt %, silicon (Si) in an amount of about 17 to 19 wt %, zinc (Zn) in an amount of about 0.50 wt % boron (B) in an amount of about 0.5 to 2 wt %, titanium (Ti) in an amount of about 4 to 6 wt %, and a balance of aluminum (Al), wherein a composition ratio of Ti: B is between about 3.5 to about 5:1, and both Al.sub.3Ti and TiB.sub.2 are included as reinforcing agents.

2. A high-elasticity hypereutectic aluminum alloy, essentially consisting of: copper (Cu) in an amount of about 4.5 wt %, magnesium (Mg) in an amount of about 0.60 wt %, silicon (Si) in an amount of about 17 to 19 wt %, zinc (Zn) in an amount of about 0.50 wt %, boron (B) in an amount of about 0.5 to 2 wt %, titanium (Ti) in an amount of about 4 to 6 wt %, and a balance of aluminum (Al), wherein a composition ratio of Ti: B is between about 3.5 to about 5:1, and both Al.sub.3Ti and TiB.sub.2 are included as reinforcing agents.

3. A method of manufacturing the high-elasticity hypereutectic aluminum alloy of claim 1, comprising the steps of: introducing Al and an Al-B master alloy, and an Al-Ti master alloy or a Ti material into a melting furnace, wherein a composition ratio of Ti: B is between about 3.5 and about 5:1 and B is included in an amount of about 0.5 to 2 wt %, thereby preparing a molten metal; first stirring the molten metal to promote a reaction, wherein both Al.sub.3Ti and TiB.sub.2 are formed as reinforcing agents; introducing an additive; and second stirring the molten metal such that the formed reinforcing agents are uniformly dispersed in the molten metal.

4. The method of claim 3, wherein the Al-B master alloy comprises an amount of about 3 to 8 wt % of B and a balance of Al.

5. The method of claim 3, wherein the Al-Ti master alloy comprises an amount of about 5 to 10 wt % of Ti and a balance of Al.

6. A vehicle part manufactured from the high-elasticity hypereutectic aluminum alloy of claim 1.

7. A vehicle part manufactured from the high-elasticity hypereutectic aluminum alloy of claim 2.

Description

DETAILED DESCRIPTION

(1) It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

(2) The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

(3) Hereinafter, various exemplary embodiments of the present invention will be described in detail but not limited thereto.

(4) The present invention pertains to a high-elasticity hypereutectic aluminum alloy. The high-elasticity hypereutectic aluminum alloy may have improved elasticity due to both Al.sub.3Ti and TiB.sub.2 as reinforcing agents, and may be casted by general casting as well as by continuous casting due to substantially low process temperature or crystallization temperature of primary silicon (Si).

(5) The high-elasticity hypereutectic aluminum alloy according to an exemplary embodiment of the present invention may include: titanium (Ti) and boron (B). The high-elasticity hypereutectic aluminum alloy may have a composition ratio of Ti:B between about 3.5:1 and about 5:1, and boron (B) may be included in an amount of about 0.5 to 2 wt %. In particular, both Al.sub.3Ti and TiB.sub.2 may be included as reinforcing agents.

(6) An aluminum alloy in the related art, as a hypereutectic aluminum alloy, the content of silicon (Si) may be restricted to in a range of about 17 to 19 wt %, the content of boron (B) may be set in a range of about 0.5 to 2 wt % in order to maximize the formation of titanium compounds, for example, TiB.sub.2 (570 GPa) or Al.sub.3Ti (220 GPa), which may be most effective in improving elasticity. Further, the composition ratio of Ti:B may be set in a range between about 3.5 to about 5:1 as of a basic alloy system.

(7) Silicon (Si), as used herein, as a main element of aluminum alloy for casting may have a great effect on fluidity and casting quality, and improve elasticity. However, when silicon (Si) is added in an amount of 19 wt % or greater, primary Si particles may be formed, and thus the microstructure of an aluminum alloy may be non-uniform, and the workability thereof may deteriorate. In an exemplary embodiment of the present invention, an aluminum alloy including a substantial amount of Si needs a continuous casting process instead of general casting process, and a post-molding process. In an exemplary embodiment of the present invention, for the purpose of obtaining an aluminum alloy having a uniform and fine structure even at the time of applying a general casting process, such as gravity casting, low-pressure casting or the like, the content of Si in the alloy system may be in an amount of 17 to 19 wt %.

(8) Ti and B may be the most important elements in the hypereutectic aluminum alloy according to an exemplary embodiment, because TiB.sub.2 and Al.sub.3Ti, as reinforcing agents, may be formed when Ti and B are added to aluminum. Particularly, when the composition ratio of Ti:B is about 3.5:1 or less, TiB.sub.2 may be formed substantially without Al.sub.3Ti, and thus the improvement of elasticity may be insufficient. Further, when the composition ratio of Ti:B is about 6:1 or greater, the melting point of the aluminum alloy may increase to about 800° C. or greater, and thus substantially large amount of oxide inclusion may be generated in molten metal, and the concentration of gas in the molten metal may increase, thereby causing a negative effect on the inner quality of a cast product.

(9) Further, the content of B may be at least of about 0.5 wt % in order to form a minimum amount of TiB.sub.2, and may be less than about 2 wt % due to the increase of dissolution temperature, the control of inclusion and the increase in cost of a raw material. Accordingly, to form both Al.sub.3Ti and TiB.sub.2, Ti and B may be included with the composition ratio of Ti:B between about 3.5:1 and 5:1.

(10) In an exemplary embodiment, the hypereutectic aluminum alloy may include: copper (Cu) in an amount of about 4.0 to 5.0 wt %, magnesium (Mg) in an amount of about 0.45 to 0.65 wt %, manganese in an amount of about 0.1 wt %, silicon (Si) in an amount of 17 to 19 wt %, zinc (Zn) in an amount of about 0.10 wt %, and a balance of aluminum (Al), thereby obtaining both elasticity and castability. The hypereutectic aluminum alloy may further comprise B in an amount of about 0.5 to 2 wt % and titanium in an amount of about 4 to 6 wt %. In particular, the composition ratio of Ti:B may be in a range between about 3.5:1 and 5:1.

(11) In an exemplary embodiment, the aluminum alloy of the present invention basically may include copper (Cu) in an amount of about 4.0 to 5.0 wt %, magnesium (Mg) in an amount of about 0.45 to 0.65 wt %, manganese in an amount of about 0.1 wt %, silicon (Si) in an amount of 17 to 19 wt %, zinc (Zn) in an amount of about 0.10 wt %, and a balance of aluminum, wherein the content of B may be in an amount of about 0.5 to 2 wt %, and the content of Ti may be adjusted such that the composition ratio of Ti:B in a range between about 3.5:1 and about 5:1. In addition, other alloy elements, such as Si, Cu, Mg and the like, may be included at the same composition ratio as that of the aluminum alloy A390. Accordingly, the aluminum alloy of the present invention may include both Al.sub.3Ti and TiB.sub.2 as reinforcing agents.

(12) In Table 1, provided are the compositions of exemplary Al—Si—Ti—B alloys according to an exemplary embodiment of the present invention.

(13) TABLE-US-00001 TABLE 1 Si Fe Cu Mn Mg Zn Ti B Al Conventional A390 17 0.5 4.0 0.1 0.45 0.1 0.2 — bal- commercially to to to ance available 19 5.0 0.65 alloy Invention EXAM- 14 — — — — — 4 1 bal- PLE 1 to to to ance. 20 6 2 EXAM- 17 0.5 4.0 0.1 0.45 0.1 4 1 bal- PLE 2 to to to to to ance 19 5.0 0.65 6 2

(14) Provided in Table 2 are the results of evaluating the Al—Si—Ti—B alloy system of which the contents of Ti and B were adjusted and the content of Si is about 17 wt %, and the results of evaluating the Al—Si—Ti—B alloy system, of which the content of Si was changed with the composition ratio of Ti:B set to 5:1.

(15) TABLE-US-00002 TABLE 2 Elastic Melting modulus (GPa) point (° C.) None of Ti and B Al—17Si 78 645 Ti/B = 1 Al—17Si—1B—1Ti 80 653 Ti/B = 2.3 Al—17Si—1B—2.3Ti 83 655 Ti/B = 3.5 Al—17Si—1B—3.5Ti 83.4 645 Ti/B = 5 Al—17Si—1B—5Ti 86.7 627 Ti/B = 6 Al—17Si—1B—6Ti 88.6 675 Ti/B = 7 Al—17Si—1B—7Ti 90.8 708 Ti:B = 5:1 None of Ti and B Al—17Si 78 645 Si = 13 Al—13Si—1B—5Ti 83.2 721 Si = 15 Al—15Si—1B—5Ti 84.8 680 Si = 17 Al—17Si—1B—5Ti 86.7 627 Si = 19 Al—19Si—1B—5Ti 88.23 655 Si = 21 Al—21Si—1B—5Ti 90 686

(16) As shown in Table 2, in the hypereutectic aluminum alloy, Si may be solid-dispersed in Al.sub.3Ti by the addition of Ti, and thus the effect of improving elasticity may be restricted by primary Si. Therefore, controlling the composition ratio of Ti/B in order to maximize the elasticity of the hypereutectic aluminum alloy may be required to maximize the formation of a reinforcing agent. Simultaneously, Si content may be changed to consider the effect thereof the hypereutectic aluminum alloy.

(17) Accordingly, when the composition ratio of Ti:B was set in a range between about 3.5:1 and about 5:1, and the melting point of the hypereutectic aluminum alloy was lowered, thereby improving the fluidity and castability thereof. Further, the lowering of the melting point may be advantageous in terms of the process window of Si texture control in the hypereutectic aluminum alloy.

(18) Meanwhile, when the composition ratio of Ti:B is set in a range between about 3.5:1 and to about 5:1 and the content of Si is set in a range of about 17 to 19 wt %, the elasticity of the hypereutectic aluminum alloy of the present invention may be improved by about 11.5% or greater compared to that of a conventional aluminum alloy, and the melting point thereof may be lowered by at most 19° C., for example, from about 645 to about 627° C., compared to that of the conventional aluminum alloy. Further, reinforcing particles may be formed in addition to primary Si particles, thereby improving the wear resistance thereof. A continuous casting process, such as high dissolution temperature, or rapid cooling speed, may be applied to general hypereutectic aluminum for the purpose of the refinement and uniform dispersion of Si particles. However, in the present invention, due to the lowering of the melting point, a high-efficiency general casting process may be applied instead of a high-cost continuous casting process.

(19) The results of evaluating the elasticity and melting point of the aluminum alloy according to various exemplary embodiments of the present invention while changing the content of Si with the composition ratio of Ti:B about 5:1 are given in Table 3 below.

(20) TABLE-US-00003 TABLE 3 Elastic Melting Al.sub.2Cu.sub.2 modulus point (Unit: wt %) Al Si Al.sub.2Cu TiB.sub.2 AlB.sub.2 Al.sub.3Ti Mg.sub.8Si.sub.6 α (GPa) (° C.) Specific Elastic 66.3 161 209 564 234 220 245 298 — — properties modulus (GPa) of reinforcing agent Density 2.7 2.33 4.22 4.49 3.16 3.3 2.76 3.54 — — (g/cm.sub.3) Commercially A390 75.4 16.4 5.6 — — — 1.7 0.9 85 661 available material Si = 13 A390- 68.8 12.5 5.8 3.2 — 7.4 1.4 0.6 91.6 725 5Ti—1B Si = 17 A390- 64.7 16.4 5.7 3.2 — 7.4 1.7 0.9 95.4 639 5Ti—1B Si = 19 A390- 60.5 18.5 5.8 3.2 — 7.4 1.4 0.9 97.3 670 5Ti—1B

(21) In the case of A390 alloy, the content of Ti is restricted to about 0.2 wt % or less, and B is not added. In the Examples of Table 3 above, the contents of Ti and B are adjusted, the content of Si is varied as about 13 wt %, about 17 wt % and about 19 wt %, and other elements of the alloy composition thereof are maintained as the same as a conventional A390 alloy. For example, in the case of A390-1B-5Ti, the content of B is adjusted to about 1 wt %, the content of Ti is adjusted to about 5 wt %, other added elements are maintained as the same as the conventional A390 alloy, while the content of Si is varied as about 13 wt %, about 17 wt % and about 19 wt %, and a balance of Al is included.

(22) As shown in Table 3 above, when the composition ratio of Ti:B is about 5:1 and the content of Si is about 17 wt %, the elasticity of the hypereutectic aluminum alloy in an exemplary embodiment of the present invention may be improved by about 12.2% or greater compared to that of a conventional aluminum alloy, and the melting point thereof and the crystallization temperature of primary Si may be lowered by at most 22° C., for example, from about 661 to about 639° C., compared to that of the conventional aluminum alloy. Further, the reinforcing particles may be formed in addition to primary Si particles, thereby improving the wear resistance thereof.

(23) In the related arts, a continuous casting process, such as high dissolution temperature and rapid cooling speed, may be applied to general hypereutectic aluminum for the purpose of the refinement and uniform dispersion of Si particles. However, according to an exemplary embodiment the present invention, due to the lowering of the melting point, a high-efficiency general casting process may be applied instead of a high-cost continuous casting process.

(24) Meanwhile, the method of manufacturing the high-elasticity hypereutectic aluminum alloy according to an exemplary embodiment of the present invention may include steps of: introducing Al and an Al—B master alloy, and an Al—Ti master alloy or a Ti material into a melting furnace such that a composition ratio of Ti:B in a range of between about 3.5:1 and about 5:1 and B may be included in an amount of about 0.5 to 2 wt %, thereby preparing a molten metal; first stirring the molten metal to promote a reaction such that both Al.sub.3Ti and TiB.sub.2 are formed as reinforcing agents; introducing an additive; and second stirring the molten metal such that the formed reinforcing agents are uniformly dispersed in the molten metal.

(25) In particular, the Al—B master alloy may include B in an amount of about 3 to 8 wt % and a balance of Al. Further, the Al—Ti master alloy may include Ti in an amount of about 5 to 10 wt % and a balance of Al. In the case of the Ti material, a high-concentration, for example, from about 75 to about 95 wt %, Ti material containing sodium-free flux as a reaction activator or a pure (100 wt %) Ti material may be used. In an exemplary embodiment of the present invention, a Ti material having a concentration of about 75 wt % may be used.

(26) Meanwhile, in the first and second stirring steps, stirring speed may be about 500 rpm or greater. Further, the diameter of a stirring bar may be about 40 mm or greater because the diameter thereof may have an effect on the acceleration of a reaction and the dispersion of reinforcing particles. When the stirring speed is less than about 500 rpm, deterioration of fluidity may occur due to the remaining of coarse Al.sub.3Ti particles, deterioration of elasticity may occur due to the insufficient formation of TiB.sub.2 and the deviation may be caused according to the region of the molten metal.

(27) As described above, a conventional hypereutectic aluminum alloy may cause problems in that a continuous casting process must be applied due to high-temperature dissolution and rapid cooling speed, and in that inclusions may increase and economical efficiency may decrease. However, in various exemplary embodiment of the present invention, a general casting process may be used in addition to a continuous casting process because the process temperatures, such as dissolution temperature, primary silicon (Si) crystallization temperature, and the like, in the manufacturing of the hypereutectic aluminum alloy may be lower than those of a commercially available hypereutectic aluminum alloy in the manufacturing thereof, and process may be substantially controlled although a continuous casting process is used.

(28) Further, according to the present invention, elasticity, strength, wear resistance, workability and the like of the hypereutectic aluminum alloy may be improved by the optimization of a titanium compound by forming maximum amount of fine TiB.sub.2 particles, distributing the fine TiB.sub.2 particles uniformly, and forming Al.sub.3Ti particles, and the like, through the control of a composition ratio. Although the exemplary embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.