Aluminum alloy

Abstract

An aluminum alloy has a low thermal conductivity at room temperature (25° C.) and a high thermal conductivity at high temperature (200° C.). The aluminum alloy includes 1˜2 wt % of magnesium (Mg), 1˜2 wt % of copper (Cu), 1˜2 wt % of zinc (Zn), 0.5˜2 wt % of nickel (Ni), and the remainder of aluminum (Al) and inevitable impurities.

Claims

1. An aluminum alloy, comprising: 1˜2 wt % of magnesium (Mg), 1˜2 wt % of copper (Cu), 1˜2 wt % of zinc (Zn), 0.5˜2 wt % of nickel (Ni), about0.5wt % of iron (Fe), about 0.5wt % of manganese (Mn), about 3.0wt % of silicon (Si), about 0.3wt % of zirconium (Zr) and a remainder of aluminum (Al) and inevitable impurities, wherein a thermal conductivity is 185 W/m*k or less at room temperature of about 25° C. and more than 185 W/m*k at high temperature 200° C.

2. The aluminum alloy of claim 1, wherein the aluminum alloy is used for an engine cylinder head.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawing, in which:

(2) FIG. 1 is a graph illustrating thermal conductivity of a conventional AC2B T7 aluminum alloy depending on the temperature;

(3) FIG. 2 is a graph illustrating thermal conductivity of an aluminum alloy according to an embodiment of the present invention depending on the temperature;

(4) FIG. 3 is a graph illustrating a decrease in thermal conductivity at high temperature due to the addition of Mg in an excessive amount (2.5 wt %);

(5) FIG. 4 is a graph illustrating a decrease in thermal conductivity at high temperature due to the addition of Cu in an excessive amount (3 wt %);

(6) FIG. 5 is a graph illustrating a decrease in thermal conductivity at high temperature due to the addition of Zn in an excessive amount (3 wt %); and

(7) FIG. 6 is a graph illustrating a decrease in thermal conductivity at high temperature due to the addition of Ni in an excessive amount (2.5 wt %).

DESCRIPTION OF SPECIFIC EMBODIMENTS

(8) The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. 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 “comprise”, “include”, “have”, etc. when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements and/or components but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or combinations thereof.

(9) Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

(10) Hereinafter, a detailed description will be given of an Al alloy according to preferred embodiments of the present invention with reference to the appended drawings.

(11) As illustrated in FIG. 2, an Al alloy having low thermal conductivity at room temperature and high thermal conductivity at high temperature has to contain 1˜2 wt % of Mg, 1˜2 wt % of Cu, 1˜2 wt % of Zn, 0.5˜2 wt % of Ni, and the remainder of Al and inevitable impurities. The inevitable impurities may include at least one of silicon (Si), iron (Fe), manganese (Mn), titanium (Ti), lead (Pb), tin (Sn), chromium (Cr), and zirconium (Zr).

(12) Solubility and resistivity of alloy elements for Al are summarized in Table 1 below. As such, Cu, Mg, Ni and Zn have low solubility. When elements having low solubility in an Al matrix are used in this way, intermetallic compounds resulting from reaction with different alloy elements may be maximized, and thereby desired properties may be obtained.

(13) TABLE-US-00001 TABLE 1 Resistivity Resistivity Thermal increment Energy release for solidification Strength cond, of Al Latent Specific Viscosity Yield Tensile (W/mK, Solubility In Out of Heat Heat H + c′DT variation MPa/ MPa/ MPa/ MPa/ Element 25° C.) in Al (wt %) solution Solution (H, kJ/kg) (c′, kJ/kg) (kJ/kg) of Al at % wt % at % wt % Phase Cr 94 0.77 4.00 0.18 402 0.66 −0.3 (+) Al.sub.2Cr Cu 400 5.65 0.34 0.03 205 0.45 −2.5 (+) 16.2 13.8 88.3 43.1 Al.sub.2Cu Fe 80 0.05 2.56 0.058 272 0.78 −1.5 (+) Al.sub.3Fe Mg 160 14.9 0.54 0.22 362 1.34 0.0 (−) 17.2 16.6 51.0 50.3 Al.sub.3Mg.sub.2 Mo 7.8 1.82 2.54 0.34 268 0.70 −1.6 (+) 30.3 53.8 Al.sub.6Mn Ni 91 0.05 0.81 0.061 292 0.56 −1.5 (+) Al.sub.3Ni Si 150 1.65 1.02 0.088 1804 0.93 14.0 (−) 9.3 9.2 40.0 39.6 Si Zn 120 82.8 0.09 0.09 111 0.48 −3.4 (0) 6.6 2.9 20.7 15.2 — Zr 23 0.28 1.74 1.74 212 0.37 −2.5 Al.sub.3Zr

(14) Mg plays a role in decreasing thermal conductivity at room temperature (25° C.), and has to be added in a relatively large amount compared to a conventional AC2B Al alloy, in order to reduce thermal conductivity at room temperature. The reason why thermal conductivity at room temperature is reduced by Mg is that resistivity of Mg solid-solved in an Al matrix is high. Hence, Mg is added in an amount of at least 1 wt %. If the amount of Mg exceeds 2 wt %, thermal conductivity at high temperature (200° C.) may decrease. Hence, the upper limit of the amount of Mg is set to 2 wt %. As illustrated in FIGS. 2 and 3, thermal conductivity at high temperature (200° C.) may be decreased when Mg is added in an amount of 2.5 wt %.

(15) Zn has low atomic scattering resistance in an Al matrix. Accordingly, Zn in solid-solution state has a low increment in resistivity depending on the increase in temperature, compared to other elements, and is thus effective at increasing thermal conductivity at high temperature (200° C.). Also, since Zn has high solubility in Al, it may be easily deposited upon thermal treatment, thereby enhancing mechanical strength. To attain such effects, Zn is added in an amount of 1 wt % or more. If the amount of Zn exceeds 2 wt %, thermal conductivity at high temperature (200° C.) may decrease. Hence, the upper limit of the amount of Zn is set to 2 wt %. As illustrated in FIGS. 2 and 5, when 3 wt % of Zn is added, thermal conductivity at high temperature (200° C.) is decreased.

(16) Cu is added in an amount of 1 wt % or more to ensure the strength of an alloy. If the amount of Cu exceeds 2 wt %, thermal conductivity at high temperature (200° C.) may decrease. Hence, Cu is used in an amount of 2 wt % or less. As illustrated in FIGS. 2 and 4, thermal conductivity at high temperature (200° C.) is decreased when 3 wt % of Cu is added.

(17) Ni is added in an amount of 0.5 wt % or more to ensure castability. If the amount of Ni exceeds 2 wt %, thermal conductivity at high temperature (200° C.) may decrease. Hence, Ni is used in an amount of 2 wt % or less. As illustrated in FIGS. 2 and 6, thermal conductivity at high temperature (200° C.) is decreased when 2.5 wt % of Ni is added.

(18) The Al alloy according to the present invention has a thermal conductivity of 185 W/m*k or less at room temperature (25° C.) and a thermal conductivity of 185 W/m*k or more at high temperature (200° C.), and is preferably utilized for an engine cylinder head.

(19) A conventional AC2B Al alloy has high thermal conductivity at room temperature (25° C.) and low thermal conductivity at high temperature (200° C.). Whereas, the Al alloy according to the present invention has low thermal conductivity at room temperature (25° C.) and high thermal conductivity at high temperature (200° C.), thus further increasing engine efficiency, ultimately contributing to enhancement in fuel efficiency.

EXAMPLE

(20) As illustrated in FIG. 2, an Al alloy having a composition of Al-1Cu-0.5Fe-2Mg-0.5Mn-0.5Ni-3Si-1Zn-0.3Zr according to the present invention can exhibit low thermal conductivity at room temperature (25° C.) and high thermal conductivity at high temperature (200° C.)

(21) Although the preferred embodiments of the present invention are described with reference to the appended drawings, it will be appreciated that the present invention may be embodied in other specific forms without changing the technical spirit or essential features by one of ordinary skill in the art.

(22) Therefore, the aforementioned embodiments are merely illustrative but are construed as limiting the present invention. The scope of the present invention is represented by the claims below rather than the detailed description, and the meaning and scope of the claims and all modifications or variations derived from equivalents thereof are intended to be incorporated within the scope of the present invention.