Aluminum alloy and its use for a vehicle part

Abstract

Aluminum alloy, comprehensive: 8.5 wt.% to 9.5 wt.% magnesium (Mg); 1.9 wt.% to 3.4 wt.% silicon (Si); 0.4 wt.% to 2.0 wt.% copper (Cu); and a residue of aluminum (Al), wherein the structure of the aluminium alloy contains particles of an Al-Mg-Cu-based intermetallic compound, and the content of the Al-Mg-Cu-based intermetallic compound in the aluminium alloy is 7.0 wt.% to 9.5 wt.%.

Description

TECHNICAL AREA

[0001] The present invention relates to a high-strength and highly corrosion-resistant lightweight aluminum alloy that does not cause white rust to form on aluminum parts of vehicles, and in particular to a high-strength and highly corrosion-resistant aluminum alloy based on aluminum-magnesium-silicon-copper (Al-Mg-Si-Cu) and a vehicle part for the use of the aluminum alloy. BACKGROUND

[0002] The present invention relates to a high-strength and highly corrosion-resistant aluminum alloy that can be used for aluminum parts of vehicles, and in particular to a high-strength and highly corrosion-resistant Al-Mg-Si-Cu-based aluminum alloy with the advantages of a conventional Al-Si-Cu-based die-casting alloy (hereinafter referred to as ADC10 / 12). The ADC10 / 12 alloy is used for die-cast vehicle parts and is still widely used due to its low cost and good castability. However, as the environmental conditions for driving motor vehicles have deteriorated, the performance limits of the ADC10 / 12 have been recognized.Therefore, there is a need for a new alloy material that can compensate for these performance limitations, for example with regard to damage to vehicle parts due to lack of durability, which did not previously occur on the parts, and white rust due to salts in seawater or de-icing.

[0003] Furthermore, many countries, including developing nations, have made efforts to prevent environmental pollution by enacting environmental protection regulations. Under such regulations, numerous studies have been conducted to reduce the weight of vehicle components in order to improve fuel efficiency in the automotive industry. However, vehicle manufacturers have faced difficulties in finding an alternative alloy material that offers the same basic performance at competitive prices to replace existing commercially available alloys.

[0004] DE 840 920 B discloses the use of aluminum alloys for machine parts subjected to sliding friction. DE 747 355 A describes the use of an aluminum alloy for pistons of internal combustion engines. WO 2012 / 070 803 A2 discloses a method for casting an Al-Mg-Si-Cu alloy that can be used in automobile bodies. WO 2011 / 090 451 A1 describes a cast alloy of the Al-Mg-Si type. DE 38 42 812 A1 discloses a cast lightweight material based on aluminum. JP 2011-80 118 A describes an aluminum alloying element and a method for its production.

[0005] The description provided above as related prior art to the present invention is intended only to facilitate understanding of the present invention and should not be considered by those skilled in the art as part of the prior art. SUMMARY OF THE INVENTION

[0006] The present invention provides a lightweight aluminum alloy with high strength and high corrosion resistance that prevents the formation of white rust on aluminum vehicle parts. In particular, the present invention provides an Al-Mg-Si-Cu-based aluminum alloy with high strength and high corrosion resistance and a vehicle part manufactured using the alloy.

[0007] The aluminum alloy contains 8.5 wt.% to 9.5 wt.% magnesium (Mg), 1.9 wt.% to 3.4 wt.% silicon (Si), 0.4 wt.% to 2.0 wt.% copper (Cu), and a remainder of aluminum. The structure of the aluminum alloy contains particles of an Al-Mg-Cu-based intermetallic compound, with the content of this compound ranging from 7.0 wt.% to 9.5 wt.%. The Mg to Si ratio in the aluminum alloy can be 3.1 to 4.3. The aluminum alloy may also contain primary magnesium silicide (Mg₂Si) crystal particles within its structure. The size of these primary Mg₂Si crystal particles can range from 2 µm to 30 µm.

[0008] In a further exemplary embodiment of the present invention, a vehicle part can be manufactured by casting and performing a heat treatment using the aluminum alloy with the composition described above. The heat treatment can be carried out at a temperature between 200°C and 250°C for a period of between 1.5 and 4.5 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above and further tasks, features and advantages of the present invention will become clearer from the following detailed description in conjunction with the accompanying drawings, in which: Fig.Figure 1 shows exemplary microscopic views of the microstructures of an aluminium alloy according to an exemplary embodiment of the present invention (left, DEVELOPED ALLOY) and a pseudobinary eutectic alloy of the prior art (right, PRIMARY ART EXAMPLE); Fig. 2 is an exemplary schematic representation showing an example of hot cracking; and Fig. Three exemplary photographic images show the decrease in corrosion resistance due to galvanic corrosion corresponding to changes in copper (Cu) content. DETAILED DESCRIPTION

[0010] An exemplary embodiment of the present invention will be described in detail below. However, this exemplary embodiment is intended only for illustrative purposes and is not meant to limit the present invention, which is defined solely by the scope of the claims as described below.

[0011] It is understood that the term "vehicle" or "vehicle-like" or any other similar term as used herein includes motor vehicles in general, such as passenger cars including all-terrain sports cars (SUVs), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft and the like, and hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other vehicles powered by alternative fuels (e.g., fuels derived from resources other than petroleum). As defined herein, a hybrid vehicle is a vehicle that has two or more energy sources, for example, both gasoline-powered and electric-powered vehicles.

[0012] Exemplary embodiments of the present invention are described below with reference to the accompanying drawings. The present invention relates to a high-strength and highly corrosion-resistant lightweight aluminum alloy that prevents the formation of white rust on aluminum parts of vehicles, and in particular to a high-strength and highly corrosion-resistant Al-Mg-Si-Cu-based alloy.

[0013] The aluminum alloy comprises 8.5 wt.% to 9.5 wt.% magnesium (Mg), 1.9 wt.% to 3.4 wt.% silicon (Si), and 0.4 wt.% to 2.0 wt.% copper (Cu), with aluminum as the remainder. The structure of the aluminum alloy contains particles of an Al-Mg-Cu-based intermetallic compound, with the content of this compound ranging from 7.0 wt.% to 9.5 wt.%. Furthermore, the Mg to Si ratio can be 3.1 to 4.3 for the production and appropriate distribution of the Al-Mg-Cu-based intermetallic compound. This ensures the high strength and corrosion resistance of the aluminum alloy. The aluminum alloy may contain primary Mg₂Si crystal particles within its structure. The size of these primary Mg₂Si crystal particles can range from 2 µm to 30 µm.

[0014] In a further exemplary embodiment of the present invention, a vehicle part is manufactured by casting and performing a heat treatment using the aluminum alloy with the above composition. The heat treatment can be carried out at a temperature between 200°C and 250°C for a duration of between 1.5 and 4.5 hours.

[0015] The present invention provides an aluminum alloy comprising Al as the main component, 8.5 wt.% to 9.5 wt.% Mg, 1.9 wt.% to 3.4 wt.% Si, and 0.4 wt.% to 2.0 wt.% Cu for the production and suitable distribution of an Al-Mg-Cu-based intermetallic compound to ensure high strength and high corrosion resistance. Therefore, advantageous properties such as low weight (e.g., reduced weight), high strength, and high corrosion resistance can be obtained compared to the existing ADC10 / 12 alloy for die-casting applications.

[0016] The prior art describes a process for obtaining a pseudobinary eutectic Al-Mg2Si structure by suppressing the formation of an intermetallic compound, limiting the Mg to Si ratio to 1.98 to 2.5 to achieve a specific microstructure, and performing ultrasonic treatment by adding Mg, Si, and Cu. However, achieving such an alloy with a pseudobinary eutectic structure of Al-Mg2Si, or with a higher Al-Mg2Si content, requires more processing steps to achieve the desired pseudobinary eutectic structure, thus increasing the quality deviation.

[0017] Accordingly, the present invention provides an aluminum alloy that can be used in conventional casting processes and which, compared to existing conventional alloys, can exhibit improved strength, lower density, and higher corrosion resistance. The aluminum alloy can be obtained by implementing a composite microstructure with a substantial number of particles consisting of an Al-Mg-Cu-based intermetallic compound and primary Mg₂Si crystal particles by optimizing the Mg to Si ratio.

[0018] Fig. Figure 1 shows exemplary microscopic images for comparing the microstructures of an alloy produced according to an exemplary embodiment of the present invention (left) and the pseudobinary eutectic structure of the prior art (right). As in Fig.As shown in Figure 1, the aluminum alloy of the present invention has a composite microstructure that can comprise Al-Mg-Cu-based (white) intermetallic compounds as main reinforcing phases and primary Mg₂Si crystal particles (black) with a size of approximately 2 µm to approximately 30 µm. Meanwhile, the eutectic Mg₂Si particles are finely dispersed in the pseudobinary eutectic structure within an Al matrix.

[0019] The present invention provides an aluminum alloy containing Al as the main component, 8.5 wt.% to 10.5 wt.% Mg, 1.9 wt.% to 3.4 wt.% Si, and 0.4 wt.% to 2.0 wt.% Cu. The Mg content in the alloy can be one of the most important elements for determining the high (e.g., improved) strength, high (e.g., improved) corrosion resistance, and low (e.g., reduced) density that are the alloy's main properties. Furthermore, the amount of Mg is 8.5 wt.% to 9.5 wt.%. If the amount of Mg is 8.0 wt.% or less, a desired content of Al-Mg-Cu-based intermetallic compound cannot be obtained despite the addition of Si due to the lack of a producible quantity of the Al-Mg-Cu-based intermetallic compound. Since the amount of the Al-Mg-Cu-based intermetallic compound, which determines the high strength and high corrosion resistance, decreases, the desired properties cannot be achieved.If the amount of Mg is 10.5 wt.% or more, the castability and mechanical properties deteriorate due to an increase in the particle size of the Al-Mg-Cu-based intermetallic compound and the formation of hot cracks.

[0020] With regard to the amount of silicon (Si), if the Si content is 1.9 wt.% or less, the castability cannot be sufficiently improved. Conversely, if the Si content is 3.4 wt.% or higher, Mg₂Si particles may be produced in excess instead of the Al-Mg-Cu-based intermetallic compound, which is the main reinforcing particle. Consequently, corrosion resistance and strength may be reduced. Therefore, to achieve optimal high strength and corrosion resistance, the Si content must be adjusted in accordance with the Mg content, and the Mg to Si ratio can range from 3.1 to 4.3.

[0021] Copper can form the Al-Mg-Cu intermetallic compound, which, in combination with magnesium, constitutes the reinforcing phase. If the amount of copper is 0.4 wt% or less, the reinforcing effect may be insufficient. If the amount of copper is 2.0 wt% or more, another intermetallic compound may form, causing galvanic corrosion with the aluminum matrix and resulting in reduced corrosion resistance of the alloy.

[0022] The examples according to the invention and comparative examples containing different amounts of Mg were tested, and each amount of Al-Mg-Cu-based intermetallic compound produced is shown in Table 1. Table 1 Object Al Mg (wt.%) Si (wt%) Cu (wt%) Amount of Al-Mg-Cu-based intermetallic compound produced (wt%) Comparative example Remaining share 7,5 3 0,9 4,0 Comparative example Remaining share 8,0 3 0,9 5,0 Inventive example Remaining share 8,5 3 0,9 7,0 Remaining share 9,0 3 0,9 8,0 Remaining share 9,5 3 0,9 9,5 Remaining share 10,0 3 0,9 10,5 Remaining share 10,5 3 0,9 12,0

[0023] Table 1 shows the changes in the amounts of Al-Mg-Cu-based intermetallic compound produced according to the Mg content in the alloy composition. As can be seen from Table 1, a sufficient amount of intermetallic compound is produced when Mg is added in an amount of 8.0 wt.% or more, and the amount of intermetallic compound generally increases with increasing Mg content. However, when a significant amount of magnesium of 10.5 wt.% or more is added, as in Fig. As shown in Figure 2, this can cause hot cracks and lead to an increase in the defective proportion during casting.

[0024] Further examples and comparative examples according to the invention, containing different amounts of Cu, were tested, and the mechanical properties of the Al-10Mg-2Si-based alloy were measured, as shown in Table 2, to demonstrate the high strength property of the Al-Mg-Si-Cu-based alloy of the present invention. Table 2 Object Al Mg (wt.%) Si(wt.%) Cu(wt.%) Tensile strength (MPa) Yield limit (MPa) Comparative example Remaining share 10 3 0,3 280 160 Inventive example Remaining share 10 3 0,4 310 175 Remaining share 10 3 0,5 325 185 Remaining share 10 3 0,7 325 210 Remaining share 10 3 0,9 335 220

[0025] Table 2 shows the changes in the mechanical properties of the Al-10Mg-3Si-based alloy according to the Cu content in the alloy composition. Table 2 shows that the mechanical properties, e.g., tensile strength or yield strength, of the Al-Mg-Si-based alloy increase with increasing Cu content. Therefore, a Cu content of 0.4 wt.% or more can be added to achieve a desired high strength of 300 MPa or higher. As with Mg, the mechanical properties generally improve with increasing Cu content. However, if the amount of Cu exceeds 2.0 wt.%, corrosion resistance may decrease due to galvanic corrosion, as shown in [reference missing]. Fig. Figure 3 shows the amount of Cu. Therefore, the amount of Cu is in the range of 0.4 wt.% to 2.0 wt.%.

[0026] As mentioned above, the durability of the aluminum alloy in an exemplary embodiment of the present invention can be improved by approximately 40% or more compared to the prior art. Furthermore, white rust, which appears in various aluminum parts, can be avoided by developing such a new high-strength / high-corrosion-resistant aluminum alloy. Additionally, the weight of the aluminum alloy can be reduced by approximately the same order of magnitude compared to the conventional prior art alloy by reducing the density by approximately 7%. Thus, the present invention is remarkable in terms of reducing the weight and cost of various aluminum castings and improving their durability.

[0027] Although the present invention has been described with reference to exemplary embodiments shown in the drawings, it is obvious to those skilled in the art that the present invention can be altered and modified in different ways without deviating from the scope of the present invention as defined in the following claims.

Claims

[1] Aluminium alloy, comprising: 8.5 wt.% to 9.5 wt.% magnesium (Mg); 1.9 wt.% to 3.4 wt.% silicon (Si); 0.4 wt.% to 2.0 wt.% copper (Cu); and a residue of aluminum (Al), wherein the structure of the aluminium alloy contains particles of an Al-Mg-Cu-based intermetallic compound, and the content of the Al-Mg-Cu-based intermetallic compound in the aluminium alloy is 7.0 wt.% to 9.5 wt.%. [2] Aluminium alloy according to claim 1, wherein the ratio of Mg to Si is 3.1 to 4.

3. [3] Aluminium alloy according to claim 1, wherein the structure of the aluminium alloy comprises primary magnesium silicide (Mg2Si) crystal particles. [4] Aluminium alloy according to claim 3, wherein the size of the primary Mg2Si crystal particles is 2 µm to 30 µm. [5] Vehicle part produced by casting and performing a heat treatment using the aluminium alloy of claim 1. [6] Vehicle part according to claim 5, wherein the heat treatment is carried out at a temperature between 200°C and 250°C for a period of time between 1.5 hours and 4.5 hours.

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