Aluminum alloys and related methods of manufacture

Abstract

Disclosed is an aluminum alloy comprising the following, in wt.%: Si: 6.5 to 8; cu: from 0.15 to 0.35; mg: 0.2 to 0.45%; less than 0.4% of Fe; mn: less than 0.2; less than 0.15% of Cr; less than 0.3% of Ni; zn: less than 0.4; less than 0.1 part of Pb; less than 0.1 of Sn; ti: 0.1 to 0.2%; aluminum and unavoidable impurities.

Description

[0001] The present invention generally relates to an aluminum alloy, in particular a secondary aluminum alloy.

[0002] Furthermore, the present invention relates to a method for manufacturing an aluminum alloy, in particular a secondary aluminum alloy.

[0003] In motor vehicles, combustion engine cylinder heads are conventionally produced from so-called "primary" aluminum alloys (i.e., aluminum alloys obtained directly from the ore bauxite). Thus, the cylinder heads are manufactured by casting such alloys.

[0004] Conventionally, primary aluminum alloys contain the following in weight %:

[0005] Si: between 6.5 and 7.5;

[0006] Cu: between 0.4 and 0.6;

[0007] Mg: between 0.25 and 0.45;

[0008] Fe: less than 0.2;

[0009] Mn: less than 0.1;

[0010] Cr: less than 0.15;

[0011] Ni: less than 0.3;

[0012] Zn: less than 0.1;

[0013] Pb: less than 0.05;

[0014] Sn: less than 0.05;

[0015] Ti: between 0.1 and 0.2;

[0016] The balance is aluminum and unavoidable impurities.

[0017] Primary aluminum alloys have a high thermal conductivity (i.e., the material has a high ability to allow heat to pass through) and a good level of elongation at break A (in %).

[0018] These property qualities are obtained by virtue of the limited presence of residual metallic elements (such as iron, copper, magnesium, and zinc) that reduce the thermal conductivity characteristics of the aluminum alloy and by virtue of the application of heat treatment.

[0019] The heat treatment applied to the primary alloy typically includes solutionizing at a temperature of about 535 °C ± 5 °C for a duration of about 145 ± 30 min; followed by air quenching and aging at a temperature of about 190 °C ± 5 °C for a duration of about 105 ± 5 min.

[0020] This results in a primary alloy having a thermal conductivity λ of approximately 160 W / m.K and an elongation at break A of greater than or equal to 4%.

[0021] This primary aluminum alloy also has a tensile strength Rm of greater than or equal to 210 MPa, a 0.2% offset yield strength Rp0.2 of greater than or equal to 190 MPa, and an HB hardness of greater than or equal to 90.

[0022] However, due to the energy consumption required for production, the primary aluminum alloy emits much more CO 2 than the so-called "secondary" aluminum alloy.

[0023] "Secondary alloy" should be understood to mean a recycled aluminum alloy obtained by remelting parts and / or scrap made of aluminum alloy.

[0024] "Scrap" should be understood to mean aluminum alloy fragments, defective products, or other wastes from all industrial sectors.

[0025] However, it is not possible to envisage the use of these recycled secondary aluminum alloys. Specifically, their residual element content is higher than that in the primary aluminum alloy. This has a negative impact on the mechanical and thermal conductivity properties.

[0026] Certain uses, such as the manufacture of combustion engine cylinder heads, require high thermal conductivity performance quality. So far, in order to ensure appropriate thermal conductivity, the use of primary aluminum alloy has thus been mandatory.

[0027] Therefore, the object of the present invention is to overcome these drawbacks and to propose an aluminum alloy having a thermal conductivity performance quality and mechanical characteristics comparable to those of the primary aluminum alloy and which can be obtained from the recycling of secondary aluminum alloy.

[0028] Therefore, an aluminum alloy is proposed, which comprises the following in weight %:

[0029] Si: between 6.5 and 8;

[0030] Cu: between 0.15 and 0.35;

[0031] Mg: between 0.2 and 0.45;

[0032] Fe: less than 0.4;

[0033] Mn: less than 0.2;

[0034] Cr: less than 0.15;

[0035] Ni: less than 0.3;

[0036] Zn: less than 0.4;

[0037] Pb: less than 0.1;

[0038] Sn: less than 0.1;

[0039] Ti: between 0.1 and 0.2;

[0040] Aluminum and inevitable impurities.

[0041] In this alloy, the percentages are defined relative to the total weight of the alloy.

[0042] It has surprisingly been found that a copper content between 0.15% by weight and 0.35% by weight enables sufficient mechanical strength of the aluminum alloy material to be ensured up to 275 °C, while ensuring a low negative impact of copper on the thermal conductivity of the material.

[0043] The heat resistance provided by a copper content between 0.15% by weight and 0.35% by weight is particularly advantageous for the application of aluminum alloys in combustion engines of motor vehicles.

[0044] Another subject of the present invention relates to a method for manufacturing an aluminum alloy, the method comprising the following steps:

[0045] a) providing an aluminum alloy as described above;

[0046] b) subjecting the alloy provided in step a) to a heat treatment, the heat treatment comprising the following steps:

[0047] i) solutionizing the aluminum alloy at a temperature of 535 °C ± 5 °C, for a duration between 145 and 175 min;

[0048] ii) performing air quenching; and

[0049] iii) aging at a temperature between 200 °C and 220 °C, preferably between 200 °C and 215 °C, for a duration between 90 and 275 min, preferably between 195 and 275 min, more preferably between 180 and 260 min.

[0050] Other features, aspects, subjects and advantages will become apparent from the following description and the following examples, which are given by way of illustration only.

[0051] Hereinafter, the expression "at least one / kind" is equivalent to the expression "one / kind or more than one / kind".

[0052] Furthermore, the limit values of the value ranges are included in the range, in particular in the expression "between... and...".

[0053] Furthermore, within the meaning of the present invention, the expression "less than" is equivalent to the expression "strictly lower than".

[0054] In the presented example, the aluminum alloy is a secondary aluminum alloy intended for the manufacture of cylinder heads for combustion engines of motor vehicles.

[0055] The aluminum alloy according to the invention comprises the following, in % by weight:

[0056] Si: between 6.5 and 8;

[0057] Cu: between 0.15 and 0.35;

[0058] Mg: between 0.2 and 0.45;

[0059] Fe: less than 0.4;

[0060] Mn: less than 0.2;

[0061] Cr: less than 0.15;

[0062] Ni: less than 0.3;

[0063] Zn: less than 0.4;

[0064] Pb: less than 0.1;

[0065] Sn: less than 0.1;

[0066] Ti: between 0.1 and 0.2;

[0067] Aluminum and unavoidable impurities.

[0068] Preferably, all unavoidable impurities account for less than 0.15% by weight.

[0069] Preferably, each unavoidable impurity is present in an amount less than 0.05% by weight.

[0070] Thus, the aluminum alloy comprises a major amount of aluminum, as well as residual elements and unavoidable impurities.

[0071] In one embodiment, the aluminum alloy may consist of the following, in % by weight:

[0072] Si: between 6.5 and 8;

[0073] Cu: between 0.15 and 0.35;

[0074] Mg: between 0.2 and 0.45;

[0075] Fe: less than 0.4;

[0076] Mn: less than 0.2;

[0077] Cr: less than 0.15;

[0078] Ni: less than 0.3;

[0079] Zn: less than 0.4;

[0080] Pb: less than 0.1;

[0081] Sn: less than 0.1;

[0082] Ti: between 0.1 and 0.2;

[0083] The balance is aluminum and unavoidable impurities.

[0084] Within the meaning of the present invention, silicon, iron, copper, manganese, magnesium, chromium, nickel, zinc, lead, tin and titanium are residual elements.

[0085] A copper content between 0.15 wt% and 0.35 wt% ensures that the aluminum alloy material has sufficient mechanical heat resistance, while at the same time ensuring that the negative impact of copper on its thermal conductivity is small.

[0086] The contents of iron and manganese in wt% are strictly less than 0.4 and strictly less than 0.2 respectively. This value range of iron and manganese ensures a limited impact on the thermal conductivity and elongation at break characteristics of the aluminum alloy.

[0087] In particular, an iron content of less than 0.4 wt% results in the formation of a small amount of intermetallic compounds, such that the elongation at break ability of the aluminum alloy is not affected.

[0088] In one embodiment, the aluminum alloy may comprise an iron content in wt% of: 0.2 ≤ Fe < 0.4.

[0089] In another embodiment, the aluminum alloy may comprise an iron content in wt% of: 0.2 < Fe < 0.4.

[0090] In another embodiment, the aluminum alloy may comprise an iron content in wt% of: 0.25 ≤ Fe < 0.4.

[0091] In another embodiment, the aluminum alloy may comprise a manganese content in wt% of: 0.1 ≤ Mn < 0.2.

[0092] Preferably, the aluminum alloy comprises a silicon content between 7 wt% and 8 wt%. Keeping silicon within this value range enables the reduction of its negative impact on the thermal conductivity of the aluminum alloy.

[0093] Advantageously, the magnesium content is between 0.2 wt% and 0.45 wt%, ensuring a limited impact of magnesium on the thermal conductivity characteristics of the aluminum alloy.

[0094] Preferably, the magnesium content is between 0.3% and 0.4% by weight. Magnesium makes it possible to ensure the mechanical characteristics after heat treatment.

[0095] The zinc content, in % by weight, is strictly less than 0.4. This value range of zinc ensures a limited effect on the thermal conductivity of the aluminum alloy.

[0096] In one embodiment, the aluminum alloy may comprise the following zinc content in % by weight: 0.1 ≤ Zn < 0.4.

[0097] In one embodiment, the aluminum alloy may comprise the following zinc content in % by weight: 0.1 < Zn < 0.4.

[0098] In one embodiment, the aluminum alloy may comprise the following zinc content in % by weight: 0.15 ≤ Zn < 0.4.

[0099] The contents of lead and tin, in % by weight, are strictly less than 0.1. This value range of lead and tin ensures a limited effect on the thermal conductivity.

[0100] In one embodiment, the aluminum alloy may comprise the following lead content in % by weight: 0.05 ≤ Pb < 0.1.

[0101] In another embodiment, the aluminum alloy may comprise the following lead content in % by weight: 0.05 < Pb < 0.1.

[0102] In another embodiment, the aluminum alloy may comprise the following lead content in % by weight: 0.075 ≤ Pb < 0.1.

[0103] In another embodiment, the aluminum alloy may comprise the following tin content in % by weight: 0.05 ≤ Sn < 0.1.

[0104] In one embodiment, the aluminum alloy may comprise the following tin content in % by weight: 0.05 < Sn < 0.1.

[0105] In another embodiment, the aluminum alloy may comprise the following tin content in % by weight: 0.075 ≤ Sn < 0.1.

[0106] According to an example, the aluminum alloy may comprise 7.46% by weight of silicon, 0.25% by weight of copper, 0.35% by weight of magnesium, 0.34% by weight of iron, 0.15% by weight of manganese and 0.15% by weight of titanium.

[0107] The method for manufacturing an aluminum alloy according to the present invention comprises the following steps:

[0108] a) providing an aluminum alloy as described above;

[0109] b) Heat-treat the alloy provided in step a), the heat treatment comprising the following steps:

[0110] i) Solutionize the aluminum alloy at a temperature of 535 °C ± 5 °C for a duration between 145 and 175 min;

[0111] ii) Perform air quenching; and

[0112] iii) Age at a temperature between 200 °C and 220 °C for a duration between 90 and 275 min.

[0113] In the first step i), heat the aluminum alloy to a temperature suitable for the aluminum alloy in order to obtain a solid solution and cause a uniform distribution within the aluminum of the various soluble components formed by the residual elements and inevitable impurities.

[0114] Then perform quenching in the second step ii). "Quenching" should be understood to mean cooling the aluminum alloy in air until its temperature reaches ambient temperature in order to fix the solid solution obtained in step i).

[0115] In the example presented, the ambient temperature is 23 °C.

[0116] Then heat the aluminum alloy in the third step iii) in order to form a uniformly distributed precipitate and induce hardening of the alloy, thereby resulting in its final thermal conductivity and elongation at break characteristics.

[0117] According to an exemplary embodiment, the aluminum alloy provided in step a) can be a secondary aluminum alloy.

[0118] The heat treatment of the aluminum alloy as described above enables mechanical and thermal conductivity characteristics equivalent to those of a primary aluminum alloy to be achieved.

[0119] Thus, a material having a thermal conductivity of approximately 160 W / m.K can be obtained from a secondary aluminum alloy.

[0120] It is also possible to achieve an elongation at break of up to 4%, a tensile strength Rm of greater than or equal to 210 MPa, a 0.2% offset yield strength Rp0.2 of greater than or equal to 190 MPa, and a HB hardness of greater than or equal to 90.

[0121] These property qualities of the aluminum alloy are particularly advantageous for manufacturing combustion engine cylinder heads for motor vehicles.

[0122] Advantageously, the manufacturing method according to the invention may include, before step a), a step of adjusting the amounts of these chemical elements in the secondary aluminum alloy to obtain the aluminum alloy as described above. The producer of the secondary alloy may adjust the quantity and type of available scrap before casting the secondary ingot to meet the chemical composition requirements in its melting furnace and holding furnace.

[0123] Preferably, the aging is carried out at a temperature between 200 °C and 215 °C.

[0124] Preferably, the aging step iii) is carried out at a temperature between 195 and 275 min.

[0125] More preferably, the aging step iii) is carried out at a temperature between 180 and 260 min, whereby the obtained thermal conductivity is optimal.

[0126] Another subject of the invention relates to a motor vehicle part, which includes at least one aluminum alloy as described above.

[0127] It will be particularly possible to define that cylinder heads, chassis parts, rims or any other motor vehicle parts are incorporated with at least one aluminum alloy as described above.

[0128] Advantageously, the aluminum alloy provided in step a) is cast into a mold to obtain a part, such as a cylinder head.

[0129] Therefore, the heat treatment of step b) is directly carried out on the part.

[0130] Another subject of the invention relates to a motor vehicle, which includes at least one aluminum alloy as defined in any one of claims 1 to 6 and / or at least one cylinder head as defined in claim 10.

[0131] It will also be possible to define that parts for the fields of aviation, rail or freight transport are incorporated with at least one aluminum alloy as described above.

[0132] The aluminum alloy according to the invention and the heat treatment of the aluminum alloy enable parts requiring high thermal conductivity to be manufactured from secondary aluminum alloy.

[0133] This makes it possible to particularly envisage increasing the amount of recycled materials in motor vehicles.

[0134] Compared with the use of primary aluminum alloy, the use of secondary aluminum alloy is a much more economical solution.

[0135] In addition, considering the sharp reduction in CO 2 emissions generated by this manufacturing method, producing parts from recycled aluminum alloy is particularly ecological. Specifically, the CO 2The amount is more than three times less than that emitted by parts made of primary aluminum alloy.

Claims

1. An aluminum alloy, comprising the following in weight %: Si: between 6.5 and 8; Cu: between 0.15 and 0.35; Mg: between 0.2 and 0.45; Fe: less than 0.4; Mn: less than 0.2; Cr: less than 0.15; Ni: less than 0.3; Zn: less than 0.4; Pb: less than 0.1; Sn: less than 0.1; Ti: between 0.1 and 0.2; aluminum and inevitable impurities.

2. The alloy according to claim 1, comprising Si between 7 wt% and 8 wt%.

3. The alloy according to claim 1 or 2, comprising, in weight %: 0.1 ≤ Mn < 0.

2.

4. The alloy according to any one of the preceding claims, comprising: Mg between 0.3 wt% and 0.4 wt%.

5. The alloy according to any one of the preceding claims, comprising, in weight %: 0.2 ≤ Fe < 0.

4.

6. The alloy according to any one of the preceding claims, comprising, in weight %: 0.1 ≤ Zn < 0.

4.

7. A method for manufacturing an aluminum alloy, which comprises the following steps: a) providing an aluminum alloy according to any one of the preceding claims; b) heat-treating the alloy provided in step a), the heat treatment comprising the following steps: i) solutionizing the aluminum alloy at a temperature of 535 °C ± 5 °C for a duration between 145 and 175 min; ii) performing air quenching; and iii) aging at a temperature between 200 °C and 220 °C, preferably between 200 °C and 215 °C, for a duration between 90 and 275 min, preferably between 195 and 275 min, more preferably between 180 and 260 min.

8. The manufacturing method according to claim 7, wherein, the aluminum alloy provided in step a) is a secondary alloy.

9. The manufacturing method according to claim 8, comprising, before step a), the step of adjusting the amounts of these chemical elements in the secondary aluminum alloy to obtain an aluminum alloy according to any one of the preceding claims.

10. A motor vehicle part, comprising at least one aluminum alloy according to any one of claims 1 to 6.

11. A motor vehicle, comprising at least one aluminum alloy according to any one of claims 1 to 6 and / or at least one part according to claim 10.