A specific aluminum alloy and a process for manufacturing a part comprising such an associated aluminum alloy

Abstract

Aluminium alloy consisting of, in % by weight: Si: between 6.5 and 8.5; Zn: between 0.2 and 0.8; Mn: between 0.2 and 0.5; Mg: between 0.1 and 0.5; Fe: 0.15 < Fe ≤ 0.35; Cu: between 0.05 and 0.35; Ti: less than or equal to 0.2; Zr: less than or equal to 0.3; Mo: less than or equal to 0.2; Ni: less than or equal to 0.1; Pb: less than or equal to 0.1; Cr: less than or equal to 0.03; V: less than or equal to 0.03; Sr: between 0.01 and 0.025; the remainder being aluminium and unavoidable impurities.

Description

Title of the invention: A special aluminum alloy and a method for manufacturing a part comprising such an associated aluminum alloy

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

[0002] Furthermore, the invention relates to a method of producing a part from such an aluminium alloy, in particular a secondary melt.

[0003] In a motor vehicle, certain parts are made from aluminum alloy called "primary smelting", that is to say, directly from an ore, Bauxite.

[0004] Conventionally, the parts are manufactured by casting process from this alloy.

[0005] In particular, certain structural parts of the body of a motor vehicle are made from a primary aluminum alloy, according to standard EN 1706-2021, consisting of, in % by weight:

[0006] If: between 6.5 and 8.5;

[0007] Mn: between 0.35 and 0.75;

[0008] Mg: between 0.10 and 0.45;

[0009] Fe: less than 0.25;

[0010] Cu: less than or equal to 0.05;

[0011] Zn: less than or equal to 0.03;

[0012] Ti: less than or equal to 0.2;

[0013] the remainder being aluminium and unavoidable impurities.

[0014] This primary aluminum alloy exhibits sufficient deformation capacity, i.e. a good level of elongation at break A%, greater than or equal to 7%, compatible with use in such structural parts.

[0015] It has a yield strength at 0.2% plastic deformation Rp0.2, greater than or equal to 100 MPa, a mechanical strength Rm greater than or equal to 200 MPa, and a hardness HB greater than or equal to 60.

[0016] These performances are obtained in the as-founded state thanks to the limited presence of residual metallic elements, such as iron, copper, nickel and zinc, which degrade the performance properties of the aluminum alloy.

[0017] However, the energy consumption required to produce this primary aluminum alloy results in the emission of a particularly high amount of CO2.

[0018] On the contrary, obtaining an aluminum alloy called "second melting", that is to say a recycled aluminum alloy, obtained by a new melting of aluminum alloy parts and / or scraps, generates a much lower quantity of CO2.

[0019] Scraps are understood to mean debris, rejects or waste of aluminium alloy, in particular from all industrial sectors.

[0020] However, the residual element content of secondary aluminum alloys is higher than in primary aluminum alloys. This results in a negative impact on the mechanical properties of the material.

[0021] The invention therefore aims to remedy these drawbacks and to provide an aluminum alloy that can be derived from the recovery of secondary aluminum alloy while guaranteeing mechanical performance equivalent to a primary aluminum alloy.

[0022] An aluminum alloy is therefore proposed, consisting of, in % by weight:

[0023] If: between 6.5 and 8.5;

[0024] Zn: between 0.2 and 0.8;

[0025] Mn: between 0.2 and 0.5;

[0026] Mg: between 0.1 and 0.5;

[0027] Fe: 0.15 <Fe <0.35;

[0028] Cu: between 0.05 and 0.35;

[0029] Ti: less than or equal to 0.2;

[0030] Zr: less than or equal to 0.3;

[0031] Mo: less than or equal to 0.2;

[0032] Ni: less than or equal to 0.1;

[0033] Pb: less than or equal to 0.1;

[0034] Cr: less than or equal to 0.03;

[0035] V: less than or equal to 0.03;

[0036] Sr: between 0.01 and 0.025;

[0037] the remainder being aluminium and unavoidable impurities.

[0038] The aluminum alloy according to the invention allows for a greater number of residual elements compared to a primary alloy. Such iron, copper, and zinc contents in the aluminum alloy make it possible to consider the use of secondary aluminum alloys while guaranteeing equivalent mechanical properties, and in particular sufficient deformation capacity for automotive applications, with suitable material behavior in the event of impact and suitability for mechanical assemblies.

[0039] In particular, the mechanical properties of the as-cast aluminum alloy according to the invention are at least equivalent to the mechanical properties of a primary aluminum alloy according to standard EN 1706-2021, without it it may be necessary to carry out a heat treatment on the aluminum alloy according to the invention.

[0040] Another object of the invention relates to a method for making a part comprising the following steps:

[0041] a) provide an aluminium alloy as previously described;

[0042] b) produce the part from the aluminium alloy supplied in step a) according to one of the casting processes among high pressure die casting (HPDC), low pressure die casting (LPDC) and counter pressure casting (CPC).

[0043] Such a manufacturing process allows the development of a secondary aluminum alloy with particularly advantageous mechanical properties for the formation of structural parts of motor vehicle bodywork, via CO2 emissions up to three times lower than for the development of a primary aluminum alloy.

[0044] Other features, aspects, objects and advantages will become apparent from the description that follows and from the following examples, given purely for illustrative purposes.

[0045] In what follows, the expression "at least one" used is equivalent to the expression "one or more".

[0046] Moreover, the bounds of a domain of values ​​are included in that domain, in particular in the expression "between".

[0047] Furthermore, for the purposes of the invention, the expression "less than" is equivalent to the expression "strictly less than".

[0048] The aluminum alloy according to the invention consists of, in % by weight:

[0049] If: between 6.5 and 8.5;

[0050] Zn: between 0.2 and 0.8;

[0051] Mn: between 0.2 and 0.5;

[0052] Mg: between 0.1 and 0.5;

[0053] Fe: 0.15 <Fe <0.35;

[0054] Cu: between 0.05 and 0.35;

[0055] Ti: less than or equal to 0.2;

[0056] Zr: less than or equal to 0.3;

[0057] Mo: less than or equal to 0.2;

[0058] Ni: less than or equal to 0.1;

[0059] Pb: less than or equal to 0.1;

[0060] Cr: less than or equal to 0.03;

[0061] V: less than or equal to 0.03;

[0062] Sr: between 0.01 and 0.025;

[0063] the remainder being aluminium and unavoidable impurities.

[0064] For the purposes of the present invention, "unavoidable impurity" means an atom, or group of atoms, other than Si, Zn, Mn, Mg, Fe, Cu, Ti, Zr, Mo, Ni, Pb, Cr, V and Sr which is present in a content of less than 0.05% by weight relative to the total weight of the aluminum alloy and whose presence does not affect the properties, in particular mechanical properties, of the aluminum alloy.

[0065] In other words, each unavoidable impurity is present in a content of less than 0.05% by weight relative to the total weight of the aluminum alloy.

[0066] Preferably, the total unavoidable impurities represent less than 0.15% by weight.

[0067] The aluminium alloy is therefore made up of aluminium in major quantity, as well as addition elements, residual elements and possible unavoidable impurities.

[0068] The aluminum alloy according to the invention is a secondary aluminum alloy.

[0069] For the purposes of the invention, silicon, zinc, manganese, magnesium, iron, copper, titanium, and strontium are added alloying elements whose content is adjusted to improve the performance of the aluminum alloy, and zirconium, molybdenum, nickel, lead, chromium, and vanadium are residual elements resulting from the recycling of the primary aluminum alloy.

[0070] Such a secondary aluminum alloy can be intended for the manufacture of a part for a motor vehicle, such as a structural part of a painted assembled body, an opening or a chassis part.

[0071] The aluminium alloy according to the invention is not limited to an application in the automotive field and can be used in any type of industrial field requiring such a material.

[0072] The copper content of between 0.05 and 0.30% by weight makes it possible to obtain sufficient mechanical characteristics, in particular thanks to the precipitation of compounds of the type Al2Cu, and of the phases S (Al2CuMg) and Q (Al2Cu-Q).

[0073] In addition, the maximum value of 0.30 of the copper content advantageously avoids the strong reactivity of the material when a cataphoresis step is carried out on the aluminum alloy, thus limiting a decrease in the deformation capacity of the material.

[0074] In one embodiment, the copper content may be between 0.05 and 0.30.

[0075] In another embodiment, the copper content may be: 0.05 < Cu < 0.30.

[0076] In another embodiment, the copper content may be: 0.05 < Cu < 0.30.

[0077] In another embodiment, the copper content may be: 0.05 < Cu < 0.30.

[0078] The zinc content, between 0.2 and 0.8% by weight, also increases slightly the mechanical characteristics of the material.

[0079] The limited content of zinc, limited to a maximum value of 0.8% by weight, avoids the risk of hot cracking and ensures that the resistance to atmospheric corrosion is not degraded.

[0080] The presence of zinc in such a range of values ​​allows in particular the use of 7000 series aluminum alloy scraps (Al-Zn) which makes it possible to increase the mechanical characteristics of the aluminum alloy part according to the invention to be manufactured.

[0081] A silicon content of between 6.5 and 8.5% by weight maximizes the deformation capacity of the aluminum alloy. This level of content prevents an excessively high proportion of the eutectic phase.

[0082] Moreover, the flowability obtained thanks to such a silicon content is advantageous for casting the aluminum alloy in the liquid state into a mold, particularly for pressure die casting, commonly called the HPDC process for the abbreviation of the English terms "High Pressure Die Casting".

[0083] The strontium content of between 0.01 and 0.025% by weight makes it possible to modify the morphology of the eutectic phase by making it sufficiently fine so that it does not harm the elongation capabilities of the aluminium alloy.

[0084] Strontium is therefore an addition element intended to modify the structure of the eutectic phase by obtaining a granular morphology, improving the deformation capacity of the aluminum alloy in the solid state.

[0085] The aluminum alloy comprises a magnesium content of between 0.10 and 0.50% by weight. Such a range of values ​​is particularly advantageous for further improving the mechanical properties of the material, notably through the precipitation of hardening compounds, of the Mg2Si type and S phases.

[0086] An iron content of 0.15 < Fe < 0.35 helps to limit the sticking of the recycled, second-melt aluminum alloy in the metal mold, in particular.

[0087] In one embodiment, the iron content may be: 0.15 < Fe < 0.35.

[0088] The iron, chromium and manganese levels are thus adjusted so as to minimize the formation of harmful intermetallic compounds and their growth in size and percentage.

[0089] In one embodiment, the chromium content of the aluminum alloy, in % by weight, can be: 0 < Cr < 0.03.

[0090] In one embodiment, the chromium content of the aluminum alloy, in % by weight, can be: 0 < Cr < 0.03.

[0091] Preferably, the titanium content is between 0.05 and 0.2 wt%, which allows for refining the microstructure of the material by enabling the formation of nuclei before the solidification of the alpha phase of aluminum. The greater the number of nuclei, the smaller the grain size.

[0092] Titanium is an alloying element used to refine the structure of the aluminum alloy in the solid state. The refinement of the structure can be determined by measuring the dendritic arm spacing, known by the acronym DAS (Dendrite Arm Spacing).

[0093] In one embodiment, the manganese content can be between 0.4 and 0.5% by weight. This provides an advantageous compromise between a minimum manganese content to avoid sticking during a molding operation and a maximum manganese content to avoid the formation of harmful intermetallics in the finished aluminum alloy part.

[0094] In one embodiment, the manganese content may be: 0.4 < Mn < 0.5% by weight.

[0095] Another object of the invention relates to a method for making a part comprising the following steps:

[0096] a) provide an aluminium alloy as previously described;

[0097] b) produce the part from the aluminium alloy supplied in step a) according to one of the casting processes among high pressure die casting (HPDC), low pressure die casting (LPDC) and counter pressure casting (CPC).

[0098] Preferably, the aluminium alloy supplied in step a) is a secondary smelting alloy, which allows for the recycling of these alloys and the production of the metallic alloy in a less energy-intensive manner and therefore with limited CO2 emissions.

[0099] Preferably, the embodiment process includes, prior to step a), a step of adjusting the quantity of the chemical elements of the second-melt aluminum alloy, obtained from the recycling of first-melt aluminum alloy, to obtain the aluminum alloy supplied in step a).

[0100] Advantageously, in step a), the manufacturing process may include a substep of casting the supplied aluminum alloy in order to give it a shape characteristic of its subsequent use.

[0101] Preferably, the embodiment process further comprises the following step:

[0102] c) carry out a cataphoresis step on the part, including a firing carried out at a temperature between 160°C and 195°C, for a time between 15 and 25 minutes.

[0103] Step c) is carried out on the part obtained at the end of step b).

[0104] Certain mechanical properties, such as the yield strength at 0.2% plastic deformation Rp0.2 and the elongation at break A%, can depend on the thickness of the part produced. The local cooling rate depends on the thickness of the part but also on the cooling capacity of the metal mold in which the part is cast. A difference in thickness between several portions of the part produced at Starting from the aluminum alloy according to the invention may lead to a slight disparity in the mechanical properties of the part.

[0105] The cataphoresis step c) has the advantage of homogenizing the mechanical characteristics of the part.

[0106] In particular, on a part comprising a first portion having a thickness El and a second portion of thickness having a thickness E2, El and E2 being different, El being for example double E2, the step c) of cataphoresis makes it possible to bring the mechanical properties of the first portion to properties equivalent to the mechanical properties of the second portion, the mechanical properties of the second portion remaining unchanged.

[0107] Cataphoresis also provides the material with anti-corrosion properties.

[0108] Another object of the invention is a part for a motor vehicle comprising at least one aluminium alloy, in particular secondary smelting, as previously described.

[0109] Another object of the invention is a motor vehicle comprising at least one aluminium alloy, in particular secondary smelting, as previously described and / or at least one part as previously described.

Claims

Demands

1. Aluminium alloy consisting of, in % by weight: Si: between 6.5 and 8.5; Zn: between 0.2 and 0.8; Mn: between 0.2 and 0.5; Mg: between 0.1 and 0.5; Fe: 0.15 < Fe < 0.35; Cu: between 0.05 and 0.35; Ti: less than or equal to 0.2; Zr: less than or equal to 0.3; Mo: less than or equal to 0.2; Ni: less than or equal to 0.1; Pb: less than or equal to 0.1; Cr: less than or equal to 0.03; V: less than or equal to 0.03; Sr: between 0.01 and 0.025; the remainder being aluminium and unavoidable impurities.

2. Alloy according to claim 1, wherein the manganese content is strictly less than 0.5% by weight.

3. Alloy according to claim 1 or 2, wherein the copper content is between 0.05 and 0.30 by weight.

4. Alloy according to any one of the preceding claims, wherein the titanium content is between 0.05 and 0.2% by weight.

5. A method for producing a part comprising the following steps: a) supplying an aluminum alloy according to any one of the preceding claims; b) producing the part from the aluminum alloy supplied in step a) according to one of the casting processes among high pressure die casting (HPDC), low pressure die casting (LPDC) and counter pressure casting (CPC).

6. A method of implementation according to claim 5, further comprising the following step: c) carrying out a cataphoresis step on the part, including a baking carried out at a temperature between 160°C and 195°C, for a time between 15 and 25 minutes.

7.

8.

9.

10. A method according to claim 6, wherein the aluminum alloy supplied in step a) is a secondary smelting alloy. A method according to claim 7, comprising, prior to step a), a step of adjusting the quantity of the chemical elements of the secondary smelting aluminum alloy to obtain an aluminum alloy as defined in any one of the preceding claims. Motor vehicle part comprising at least one aluminium alloy as defined in any one of claims 1 to 4. Motor vehicle comprising at least one aluminium alloy as defined in any one of claims 1 to 4 and / or at least one part as defined in claim 9.