6xxx aluminum alloy with improved recyclability

Abstract

The invention concerns an aluminum alloy of the 6XXX family, useful to increase the recycling rate in wrought products of this type of alloy, particularly for extruded products in the automotive field. In particular, the alloy of the invention contains, in wt.%, by weight, Si 0.3 – 1.4, Mg 0.1 - 1.2, Cu 0.02 – 1.2, Mn 0.02 – 1.0, Ni 0.1 – 0.4, Fe 0.3 – 0.6, Cr 0.05 – 0.4, Ti ≤ 0.2, Zr ≤ 0.3, V ≤0.2, Zn ≤1.0, aluminum and unavoidable impurities. The invention concerns also a heat-treated wrought product comprising an alloy according to the invention and a process for manufacturing a heat-treated wrought product.

Description

[0001] DESCRIPTION

[0002] Title: 6XXX ALUMINUM ALLOY WITH IMPROVED RECYCLABILITY

[0003] FIELD OF THE INVENTION

[0004] The invention concerns an aluminum alloy of the 6XXX family, useful to increase the recycling rate in wrought products of this type of alloy, particularly for extruded products in the automotive field.

[0005] STATE OF THE ART

[0006] Aluminum recycling has the advantage of being both economical and environmentally friendly. The production of secondary aluminum requires up to 95% less energy than primary aluminum, and reduces CO2 emissions. With a view to improving the environmental impact of aluminum production, the aluminum industry is seeking to maximize the proportion of recycled material in its products. However, increasing the level of recycled material generally leads to an increase in impurity content, particularly iron content, implying higher volume fractions and / or intermetallic particle sizes, which can be detrimental to process times such as homogenization, forming properties such as elongation and formability, consumption of free-Si in the alloy, thus decreasing the precipitation strengthening potential as well as reducing the dispersoid density, which also contributes to decreasing the strength of the aluminum alloy due to a less effective fibrous structure / substructure, and deterioration of surface properties such as response to anodizing. This difficulty is explained, for example, in the article "Texture control by thermomechanical processing of AA6xxx Al-Mg-Si sheet alloys for automotive applications-a review" in Materials Science and Engineering A336 (2002) 249-262.

[0007] To avoid these harmful effects, the metal can be purified.

[0008] Patent FR2902800 describes a process for manufacturing a remelting block from scrap, in particular for purifying scrap from alloys in the 2XXX or 7XXX series in terms of iron and silicon, without however eliminating additive elements such as zinc, copper and magnesium.

[0009] However, these additional purification steps can be difficult and costly to implement.

[0010] Patent application W02015 / 151907 Al also mentions the problem of impurity content in recycled alloys.

[0011] Patent application US20080175747 describes an alloy in which impurities have little effect on properties.

[0012] Patent application JP2007169740 A describes an alloy comprising, in wt.%, Si: 0.5 - 1.5%, Mg: 0.2 - 2.0%, and up to Fe: 1.5%, up to Mn: 1.0%, up to Cr: 0.5%, up to Zr: 0.5%, up to V: 0.3%, up to Ti: 0.2%, up to Zn = 1.5%, up to Cu: and containing not less than 0.015% and not more than 0.5% of Bi, Sn, Ga, Co, Ni, Ca, Mo, Be, Pb, and W remainder aluminum and impurities.

[0013] Patent application JP2016037632 describes an aluminum alloy sheet containing Mg: 0.2 to 2.0% by mass, Si: 0.3 to 2.0% by mass and Fe: 0.01 to 0.5% by mass and one or both of Ni and Co totalling 0.002 to 0.3% by mass and the balance Al with unavoidable impurities.

[0014] Patent application EP2072628 discloses an AIMgSi-type aluminum alloy extruded or forged product comprising, in wt.%: Si 0.5 to 0.95, Mg 0.6 to 0.95, Mn 0.1 to 0.3, V 0.05 to 0.25, Ni 0.05 to 0.25, Cu maximum 0.3, optionally one or two element(s) selected from the group consisting of: (Cr 0.05 to 0.2, and Zr 0.05 to 0.2), Zn< 0.2, Fe < 0.5, Ti < 0.1, inevitable impurities and balance aluminum.

[0015] Patent application JPH09-143604 discloses an alloy containing., by weight, 0.35 to 0.80% Mg, 0.20 to 0.90% Si, 0.16 to 0.25% Fe, 0.01 to 0.20% Cu, 0.01 to 0.15% Ni and 0.01 to 0.02% Ti, and the balance aluminum with impurities, and, optionally, one or two kinds of <+0.15% Mn and <+0.10% Cr may be incorporated therein.

[0016] Patent application W02023 / 209810 discloses a 6000 series aluminum alloy Al-Mg-Si-Ni characterized by containing more than 0 to 2.0 wt% of Fe and containing Ni such that 0.7<Ni (wt%) / Fe (wt%)<3.5.

[0017] The problem that the present invention seeks to solve is therefore to propose an alloy that can tolerate an increased impurity content, particularly iron, and therefore not require additional purification, and also to limit the duration of homogenization treatments.

[0018] DESCRIPTION OF THE INVENTION

[0019] A first object of the invention is an aluminum-based alloy comprising, in % by weight,

[0020] Si: 0.3 - 1.4;

[0021] Mg: 0.1 - 1.2;

[0022] Cu: 0.02 - 1.2;

[0023] Mn: 0.02 - 1.0;

[0024] Ni: 0.1 - 0.4;

[0025] Fe: 0.3 - 0.6;

[0026] Cr: 0.05 - 0.4;

[0027] Ti: < 0.2;

[0028] Zr: < 0.3;

[0029] V: < 0.2; Zn: <1.0; aluminum and unavoidable impurities.

[0030] Another object of the invention is a heat-treated wrought product comprising an alloy according to the invention.

[0031] Yet another object of the invention is a process for manufacturing a heat-treated wrought product according to the invention comprising the steps of

[0032] - Supply pure or alloyed aluminum in the form of primary metal ingots from electrolysis and / or pre-consumer manufacturing scrap and / or post-consumer scrap, said scrap having optionally been melted down separately and possibly solidified, and of addition elements in suitable form;

[0033] - Prepare a load with the supplied aluminum, melt this load and add the additives to obtain a bath of liquid metal in an alloy according to the invention,

[0034] - Cast, preferably by vertical semi-continuous casting with direct cooling, said liquid metal bath to obtain a blank suitable for hot working, typically a rolling plate, a forging blank or an extrusion billet;

[0035] - Homogenize the blank at a temperature of at least 500°C;

[0036] - Hot-work and optionally cold-cold work the blank by rolling, extrusion and / or forging to obtain a wrought product;

[0037] - Solution heat-treat the wrought product thus obtained at a temperature of at least 500°C and quench;

[0038] - Natural age and / or artificially age the solution heat treated and quenched wrought product thus obtained.

[0039] Yet another object of the invention is the use of a product according to the invention for automobile construction, building construction, aircraft construction or industrial construction.

[0040] FIGURES

[0041] Figure 1 shows an electron microscopy image in backscattered-electron (BSE) contrast of intermetallic particles of alloy H cast in billets of diameter 152 mm.

[0042] Figure 2 shows an electron microscopy image in backscattered-electron (BSE) contrast of intermetallic particles of alloy I cast in billets of diameter 152 mm.

[0043] Figure 3 shows the intermetallic compounds (IMCs) size distribution, alloy H in black and alloy I in white. DETAILED DESCRIPTION OF THE INVENTION

[0044] Unless otherwise stated, all indications concerning the chemical composition of alloys are expressed as a percentage by weight based on the total weight of the alloy. The expression 1.4 Cu or 1.4 (Cu) means that the copper content expressed in % by weight is multiplied by 1.4. Alloys are designated in accordance with the regulations of The Aluminum Association, known to the person skilled in the art. Unless otherwise stated, the metallurgical temper definitions of EN515 - 2017 apply.

[0045] The present inventors have found that, surprisingly, the addition of nickel in precise quantity to AIMgSi alloys, also known as 6XXX series alloys, makes it possible to tolerate an increased impurity content, particularly iron without loss of strength.

[0046] Intermetallic particles are compounds containing several metallic elements or metalloids formed during solidification after the formation of face-centered cubic aluminum crystal, such as AU Fe, Mg2 Si, AIFeSi, AIFeMnSi, etc...

[0047] Alloys according to the invention are AIMgSi alloys. They contain from 0.3% to 1.4% Si and from 0.1% to 1.2% Mg.

[0048] In an embodiment, the content of Si is at least 0.4%, or is at least 0.5%, or is at least 0.6%, or is at least 0.7%, or is at least 0.8%, or is at least 0.9%, or is at least 1.0%, or is at least 1.1%, or is at least 1.2%, or is at least 1.3%, and / or is at most 1.4%, or is at most 1.3%, or is at most 1.2%, or is at most 1.1%, or is at most 1.0%, or is at most 0.9%, or is at most 0.8%, or is at most 0.7%, or is at most 0.6%, or is at most 0.5%.

[0049] In a preferred embodiment the content of Si is from 0.4% to 1.1%, preferably 0.6% to 1.0% and more preferably from 0.7% to 0.9%.

[0050] In an embodiment, the content of Mg is at least 0.2%, or is at least 0.3%, or is at least 0.4%, or is at least 0.5%, or is at least 0.6%, or is at least 0.7%, or is at least 0.8%, or is at least 0.9%, or is at least 1.0%, or is at least 1.1%, and / or is at most 1.2%, or is at most 1.1%, or is at most 1.0%, or is at most 0.9%, or is at most 0.8%, or is at most 0.7%, or is at most 0.6%, or is at most 0.5%, or is at most 0.4%, or is at most 0.3%.

[0051] In a preferred embodiment the content of Mg is from 0.3% to 1.0%, preferably from 0.3% to 0.9% and more preferably from 0.5% to 0.9%.

[0052] Copper is added to the AIMgSi alloys of the invention, in particular to improve mechanical properties. In an embodiment, the content of Cu is at least 0.06%, or is at least 0.10%, or is at least 0.14%, or is at least 0.18%, or is at least 0.22%, or is at least 0.26%, or is at least 0.30%, or is at least 0.34%, or is at least 0.38%, or is at least 0.42%, or is at least 0.46%, or is at least 0.50%, or is at least 0.54%, or is at least 0.58%, or is at least 0.62%, or is at least 0.66%, or is at least 0.70%, or is at least 0.74%, or is at least 0.78%, or is at least 0.82%, or is at least 0.86%, or is at least 0.90%, or is at least 0.94%, or is at least 0.98%, or is at least 1.02%, or is at least 1.06%, and / or is at most 1.10%, or is at most 1.06%, or is at most 1.02%, or is at most 0.98%, or is at most 0.94%, or is at most 0.90%, or is at most 0.86%, or is at most 0.82%, or is at most 0.78%, or is at most 0.74%, or is at most 0.70%, or is at most 0.66%, or is at most 0.62%, or is at most

[0053] 0.58%, or is at most 0.54%, or is at most 0.50%, or is at most 0.46%, or is at most 0.42%, or is at most 0.38%, or is at most 0.34%, or is at most 0.30%, or is at most 0.26%, or is at most 0.22%, or is at most 0.18%, or is at most 0.14%, or is at most 0.10%.

[0054] In a preferred embodiment the content of Cu is from 0.6% to 1.1% and preferably from 0.7% to 1.0%. In another preferred embodiment the content of Cu is from 0.1% to 0.8%.

[0055] For the major elements Mg, Si and Cu, the contents of alloys AA6009, AA6010, AA6011, AA6111

[0056] AA6013, AA6113, AA6018, AA6019, AA6020, AA6023, AA6024, AA6026, AA6028, AA6031.

[0057] AA6033, AA6040, AA6041, AA6042, AA6043, AA6055, AA6056, AA6156, AA6061, AA6261.

[0058] AA6361, AA6262, AA6963, AA6064, AA6065, AA6066, AA6070, AA6086, AA6091, AA6092. AA6099 are embodiments of the invention.

[0059] Embodiments of the invention for the major elements Mg, Si and Cu are also within alloys AA6101, AA6101A, AA6101B, AA6201, AA6201A, AA6401, AA6501, AA6002, AA6003, AA6103, AA6005, AA6005A, AA6005B, AA6005C, AA6105, AA6205, AA6305, AA6006, AA6106, AA6206, AA6306, AA6008, AA6012, AA6012A, AA6014, AA6015, AA6016, AA6016A, AA6116, AA6021, AA6022, AA6025, AA6027, AA6151, AA6351, AA6351A, AA6451, AA6951, AA6053, AA6060, AA6160, AA6260, AA6360, AA6460, AA6460B, AA6560, AA6660, AA6162, AA6063, AA6063A, AA6463, AA6463A, AA6763, AA6068, AA6069, AA6070, AA6081, AA6181, AA6181A, AA6082, AA6082A, AA6182.

[0060] The Mn content is from 0.02 to 1.0%. In an embodiment, the content of Mn is at least 0.05%, or is at least 0.10%, or is at least 0.15%, or is at least 0.20%, or is at least 0.25%, or is at least 0.30%, or is at least 0.35%, or is at least 0.40%, or is at least 0.45%, or is at least 0.50%, or is at least 0.55%, or is at least 0.60%, or is at least 0.65%, or is at least 0.70%, or is at least 0.75%, or is at least 0.80%, or is at least 0.85%, or is at least 0.90%, and / or is at most 0.95%, or is at most 0.90%, or is at most 0.85%, or is at most 0.80%, or is at most 0.75%, or is at most 0.70%, or is at most 0.65%, or is at most 0.60%, or is at most 0.55%, or is at most 0.50%, or is at most 0.45%, or is at most 0.40%, or is at most 0.35%, or is at most 0.30%, or is at most 0.25%, or is at most 0.20%, or is at most 0.15%, or is at most 0.10%.

[0061] In a preferred embodiment the content of Mn is from 0.3% to 0.7% and preferably from 0.4% to 0.6%. In another preferred embodiment the content of Mn is from 0.05% to 0.7%.

[0062] The Ni content is from 0.1 to 0.4% by weight. In an embodiment, the content of Ni is at least 0.15%, or is at least 0.20%, or is at least 0.25%, or is at least 0.30%, and / or is at most 0.35%, or is at most 0.30%, or is at most 0.25%, or is at most 0.20%.

[0063] In a preferred embodiment the content of Ni is from 0.1% to 0.4% preferably from 0.15% to 0.35% and more preferably from 0.18% to 0.28%.

[0064] The Fe content is from 0.3 to 0.6% by weight. In an embodiment, the content of Fe is at least 0.30%, or is at least 0.35%, or is at least 0.40%, or is at least 0.45%, or is at least 0.50%, or is at least 0.55%, and / or is at most 0.60%, or is at most 0.55%, or is at most 0.50%, or is at most 0.45%, or is at most 0.40%, or is at most 0.35%.

[0065] In a preferred embodiment the content of Fe is from 0.30% to 0.60% and preferably from 0.40% to 0.55%.

[0066] In an embodiment the ratio Ni (wt%) / Fe (wt%) is at most 0.6 and preferably at most 0.5.

[0067] The Cr content is from 0.05% to 0.4% by weight. In an embodiment, the content of Cr is at least 0.10%, or is at least 0.15%, or is at least 0.20%, or is at least 0.25%, or is at least 0.30%, and / or is at most 0.35%, or is at most 0.30%, or is at most 0.25%, or is at most 0.20%, or is at most 0.15%.

[0068] In a preferred embodiment the content of Cr is from 0.05% to 0.2%, preferably from 0.06% to 0.15% and more preferably from 0.08% to 0.13%.

[0069] The Ti content is up to 0.2% by weight. In an embodiment, the content of Ti is at least 0.01%, or is at least 0.02%, or is at least 0.03%, or is at least 0.04%, or is at least 0.05%, or is at least 0.06%, or is at least 0.07%, or is at least 0.08%, or is at least 0.09%, or is at least 0.10%, or is at least 0.11%, or is at least 0.12%, or is at least 0.13%, or is at least 0.14%, or is at least 0.15%, or is at least 0.16%, or is at least 0.17%, or is at least 0.18%, and / or is at most 0.19%, or is at most 0.18%, or is at most 0.17%, or is at most 0.16%, or is at most 0.15%, or is at most 0.14%, or is at most 0.13%, or is at most 0.12%, or is at most 0.11%, or is at most 0.10%, or is at most 0.09%, or is at most 0.08%, or is at most 0.07%, or is at most 0.06%, or is at most 0.05%, or is at most 0.04%, or is at most 0.03%, or is at most 0.02%. The addition of titanium may be done in the form of titanium metal and / or Ti B2and / or TiC. In a preferred embodiment the content of Ti is from 0.01% to 0.10% and preferably from 0.02% to 0.08%.

[0070] The Zr content is at most 0.3% by weight. In an embodiment, the content of Zr is at least 0.01%, or is at least 0.03%, or is at least 0.05%, or is at least 0.07%, or is at least 0.09%, or is at least 0.11%, or is at least 0.13%, or is at least 0.15%, or is at least 0.17%, or is at least 0.19%, or is at least 0.21%, or is at least 0.23%, or is at least 0.25%, and / or is at most 0.28%, or is at most 0.26%, or is at most 0.24%, or is at most 0.22%, or is at most 0.20%, or is at most 0.18%, or is at most 0.16%, or is at most 0.14%, or is at most 0.12%, or is at most 0.10%, or is at most 0.08%, or is at most 0.06%, or is at most 0.04%.

[0071] In a preferred embodiment the content of Zr is from 0.10% to 0.20% and preferably from 0.12% to 0.18%.

[0072] The V content is at most 0.2% by weight. In an embodiment of the invention the V content is from 0.05 to 0.20% by weight. In an embodiment, the V content is at least 0.06%, or is at least 0.07%, or is at least 0.08%, or is at least 0.09%, or is at least 0.10%, or is at least 0.11%, or is at least 0.12%, or is at least 0.13%, or is at least 0.14%, or is at least 0.15%, or is at least 0.16%, or is at least 0.17%, or is at least 0.18%, and / or is at most 0.19%, or is at most 0.18%, or is at most 0.17%, or is at most 0.16%, or is at most 0.15%, or is at most 0.14%, or is at most 0.13%, or is at most 0.12%, or is at most 0.11%, or is at most 0.10%, or is at most 0.09%, or is at most 0.08%, or is at most 0.07%. In a preferred embodiment the V content is at most 0.05% and preferably at most 0.04%.

[0073] The Zn content is at most 1.0% by weight. In an embodiment, the Zn content is from 0.03 to 1.0% by weight. In an embodiment, the Zn content is at least 0.05%, or is at least 0.10%, or is at least 0.15%, or is at least 0.20%, or is at least 0.25%, or is at least 0.30%, or is at least 0.35%, or is at least 0.40%, or is at least 0.45%, or is at least 0.50%, or is at least 0.55%, or is at least 0.60%, or is at least 0.65%, or is at least 0.70%, or is at least 0.75%, or is at least 0.80%, or is at least 0.85%, or is at least 0.90%, and / or is at most 0.95%, or is at most 0.90%, or is at most 0.85%, or is at most 0.80%, or is at most 0.75%, or is at most 0.70%, or is at most 0.65%, or is at most 0.60%, or is at most 0.55%, or is at most 0.50%, or is at most 0.45%, or is at most 0.40%, or is at most 0.35%, or is at most 0.30%, or is at most 0.25%, or is at most 0.20%, or is at most 0.15%, or is at most 0.10%. In a preferred embodiment the Zn content is at most 0.05% and preferably at most 0.04%.

[0074] A preferred composition of the aluminum-based alloy according to the invention comprise in % by weight Si 0.4 - 1.1, Mg 0.3 - 0.9, Cu 0.1 - 0.8, Mn 0.05 - 0.7, Ni 0.1 - 0.4, Fe: 0.3 - 0.6, Cr 0.05 - 0.2, Ti < 0.2, Zr < 0.2, V < 0.15; Zn <1.0, aluminum and unavoidable impurities.

[0075] The other elements are unavoidable impurities, typically containing no more than 0.05% by weight, or no more than 0.04%, no more than 0.03%, no more than 0.02%, no more than 0.01%. In one embodiment other elements < 0.05% each and < 0.15% total. The rest is aluminum.

[0076] Alloys according to the invention may have the advantage of a smaller average intermetallic particle size. It was also found that the intermetallic particles are more rounded.

[0077] An object of the invention is a heat-treated wrought product comprising an alloy according to the invention. By heat-treated product is meant in the context of the invention a product in a T temper which means a heat-treated alloy product heat-treated to obtain stable tempers other than F, O or H. Typically, the heat-treated product is in a T3, T4, T5, T6, T7, T8 or T9 temper.

[0078] An object of the invention is an extruded product comprising an alloy according to the invention. An extruded product according to the invention typically has a thickness of 0.5 mm to 30 mm and preferably 0.8 mm to 20 mm. Another object of the invention is a forged product comprising an alloy according to the invention. A forged product according to the invention typically has a local thickness of 0.5 mm to 300 mm and preferably 0.8 mm to 150 mm. A forged product of the invention may advantageously be obtained by forging an extruded product according to the invention. Another object of the invention is a rolled product comprising an alloy according to the invention. A rolled product according to the invention typically has a thickness of 0.5 mm to 300 mm and preferably 0.8 mm to 150 mm.

[0079] A preferred product according to the invention is an extruded product.

[0080] A process for obtaining a heat-treated wrought product according to the invention comprises the steps of

[0081] - Supply pure or alloyed aluminum in the form of primary metal ingots from electrolysis and / or pre-consumer manufacturing scrap and / or post-consumer scrap, said scrap having optionally been melted down separately and possibly solidified, and of addition elements in suitable form;

[0082] - Prepare a load with the supplied aluminum, melt this load and add the additives to obtain a bath of liquid metal in an alloy according to the invention,

[0083] - Cast, preferably by vertical semi-continuous casting with direct cooling, said liquid metal bath to obtain a blank suitable for hot working, typically a rolling plate, a forging blank or an extrusion billet;

[0084] - Homogenize the blank at a temperature of at least 500°C; - Hot-work and optionally cold-cold work the blank by rolling, extrusion and / or forging to obtain a wrought product;

[0085] - Solution heat-treat the wrought product thus obtained at a temperature of at least 500°C and quench;

[0086] - Natural age and / or artificially age the solution heat treated and quenched wrought product thus obtained.

[0087] In a first step, pure or alloyed aluminum is supplied in the form of a primary metal ingot from electrolysis and / or pre-consumer manufacturing scrap and / or post-consumer scrap, which has optionally been melted down separately and solidified, and additives in suitable form.

[0088] Pure or alloyed aluminum in the form of primary metal ingots generally has the disadvantage of generating significant CO2 emissions during manufacture, and it is therefore tried to limit its use. With regard to other sources of metal, a distinction is made between pre-consumer scrap, which is generated before the metal is delivered to the end customer: the window buyer, vacuum chamber user, car buyer, aircraft manufacturer etc., and post-consumer scrap, which is recovered after the product has been used, typically from the used car. The manufacturing stages of aluminum products generate a great deal of pre-consumer scrap during all stages. This may include, for example, ends of cast plates or billets that have been cut off before hot working, ends of rolled or extruded products that have been cut off during the sheet or section manufacturing process, skeletons of blanks used for stamping, machining chips, etc. Examples of post-consumer scrap include used window frames, automotive parts recovered from scrap yards, crushed automobiles, dismantled aircraft, etc. Post-consumer scrap can be supplied raw, in compacted form or optionally having been melted down separately and possibly solidified. Addition elements are also supplied in suitable form. These may be elements in their metallic or alloyed form.

[0089] In a subsequent step, a load is formed from all or part of the supplied aluminum, this load is melted and additives are added to obtain a liquid metal bath with a composition according to the invention. Some of the supplied aluminum may already be in liquid form.

[0090] The process according to the invention is advantageous because it enables a high percentage of pre-consumer manufacturing scrap and / or post-consumer scrap to be used in the constitution of the load. In an embodiment, the load contains at least 20% or at least 30% or at least 40% or at least 50% or at least 60% or at least 70% or at least 80% or at least 90% pre-consumer manufacturing scrap. In an embodiment, the load contains at least 20% or at least 30% or at least 40% or at least 50% or at least 60% or at least 70% or at least 80% or at least 90% post- consumer scrap. Thus, in an embodiment, the load contains at least 20% or at least 30% or at least 40% or at least 50% or at least 60% or at least 70% or at least 80% or at least 90% or at least 95% of pre-consumer manufacturing scrap and post-consumer scrap. The load is then melted and its composition adjusted using additives to obtain a liquid metal bath with a composition in accordance with the invention.

[0091] In a subsequent step, the liquid metal bath is cast, preferably by direct-cooling vertical semi- continuous casting, to obtain a blank suitable for hot-working, typically a rolling plate or billet.

[0092] In a subsequent step, the resulting blank is homogenized at a temperature of at least 500°C. The homogenization time during which the entire blank has reached a temperature of at least 500°C is typically at least 2 hours or at least 3 hours or at least 4 hours or at least 5 hours or at least 6 hours. In certain embodiments, alloys according to the invention can be used to reduce homogenization time. Thus, the homogenization time during which the entire blank has reached a temperature of at least 500°C is advantageously at most 12 hours or at most 11 hours or at most 10 hours or at most 9 hours or at most 8 hours. In an embodiment, homogenization is carried out in two steps, the second step having a higher temperature than the first step.

[0093] In a subsequent step, the homogenized blank is hot- and optionally cold-worked by rolling, extruding and / or forging to obtain a wrought product. Hot working is typically started at a temperature of at least 400°C. In an embodiment, the blank is cooled from the homogenization temperature to the hot working temperature, optionally by forced cooling. In another embodiment, the blank is cooled to room temperature after homogenization, then reheated to the hot-working start temperature.

[0094] In a subsequent step, the wrought product thus obtained is solutionized at a temperature of at least 500°C and quenched. Quenching is typically carried out with water by immersion or sprinkling, although air quenching is also possible for certain products, notably extruded products.

[0095] In an optional further step, the wrought product thus solutionized and quenched can be cold worked and / or stress-relieved. In an embodiment the wrought product thus solutionized and quenched is straightened by stretching, for example by application of a stretching with an elongation from 0.5 to 2%.

[0096] In a subsequent step, the solution-heat treated and quenched wrought product thus obtained is aged at room temperature and / or artificially aged to obtain a heat-treated wrought product.

[0097] In an embodiment, for the manufacture of extrusions, the re-heating step before extrusion consists in a pre-heating of the cast billet, between 410°C and 530°C during a period of less than 1 hour, before performing subsequently the extrusion step.

[0098] In another embodiment, for the manufacture of extrusions, the re-heating step consists in a solution heat treating step, before performing the extrusion step. It consists in a soaking step at a temperature between Ts-80°C and Ts, wherein Ts is the solidus temperature of the said 6xxx aluminum alloy and quenching the billet until billet mean temperature reaches a value between 400°C and 480 °C while ensuring billet surface never goes below a temperature substantially close to 400 °C before performing the extrusion step. The quenched billet is then extruded. The extrusion is performed immediately after the step of quenching. Immediately corresponds typically to a time period between 1 second to 2 minutes. This time period has to be limited to avoid that the surface temperature of the billet goes below 400°C. Quenching step is preferably performed by water spraying.

[0099] In an embodiment the extrusion is a hollow extrusion. The geometry of the cross section of said hollow extrusion is preferably suitable to obtain a good aptitude for crush.

[0100] In an embodiment, the extrusion is a plain extrusion or a solid extrusion.

[0101] In another embodiment for the manufacture of extrusions, after the extrusion step, the extrusion is press quenched. Preferably, the extrusion is intensively cooled down by water spraying or immersion to obtain a satisfying yield strength and good crush properties after artificial ageing. The cooling rate is at least 50°C / s, more preferably higher than 100°C / s and even more higher than 120°C / s.

[0102] In an embodiment for the manufacture of extrusions, the quenched extrusion is then naturally aged during less than 100 days. Natural ageing corresponds to properties changes at room temperature after quenching. It may start immediately after quenching or after an incubation period. Preferably, natural ageing period is less than 15 days, more preferably less than 48h, more preferably less than 24 h, even more preferably less than 12 h and even more preferably less than 1 hour to obtain good crush properties. To permit to have a consistent process, it is preferable that the natural ageing is controlled and lasts more than 0.5 h. In a more preferred embodiment, the duration of natural ageing after quenching is between 0.5 h to 10 days, more preferably between 0.2 h to 24 h, more preferably between 0.2 h to 12 h and even more preferably between 0.2 h to 1 h.

[0103] In an embodiment for the manufacture of extrusions, the naturally aged product is aged according to a thermomechanical ageing, so called TMA which consists in three successive steps: - Step 1: an artificial preageing treatment is performed during a duration tl at a temperature Tl. Conditions tl and Tl are selected to increase the yield strength by 5% to 20%, preferably by 6% to 19%, and more preferably by 8% to 18% compared to the yield strength of the extrusion after the end of the natural ageing step, ie corresponding to the T4 temper properties. The duration tl and the temperature T1 of the preageing treatment are respectively typically between 15 min to 100 hours and 120°C to 190°C to obtain an artificially preaged extrusion.

[0104] - Step 2: a plastic deformation of said artificially preaged extrusion is performed and corresponds to a plastic deformation between 1% to 80%, preferably between 1% to 50%, more preferably between 1% to 20, more preferably between 2% to 7% and even more preferably between 2% to 6%. Said plastic deformation is preferably obtained by stretching, or by in any others techniques such as hydroforming or pressing or stamping or bending or roll bending or stretch bending or rotary stretch bending or pulse magnetic forming or flow forming or forging or rolling or drawing or deep drawing or impact or inverse extrusion or punching or blanking. Said plastic deformation is preferentially performed at room temperature. In one preferred embodiment, said plastic deformation is applied uniformly on the said artificially preaged extrusion. In one other embodiment, said plastic deformation is applied locally on the said artificially preaged extrusion.

[0105] - Step 3: a final artificial ageing treatment of said deformed extrusion with a duration t2 at a temperature T2 whose duration t2 and temperature T2 are selected to reach a maximum yield strength or an overaged temper. Preferably, final artificial ageing treatment is an overaged temper to obtain the good crashability performance. Typically said temperature T2 is between 140°C to 200°C and the duration t2 between 1 to 100 hours. Said final artificial ageing treatment may be performed in multiple steps. Multiple steps include the ramp-up to reach the plateau temperature T2. This ramp up is possibly done by a progressive increase in temperature or by an intermediate plateau. In an embodiment, final artificial ageing is done in two steps with a first step at a temperature T3 and a duration t3 and a second step at a temperature T4 and a duration t4; temperature T3 being lower than temperature T4.

[0106] Preferably for the manufacture of extrusions the artificial aging is such that the equivalent time t(eq) at 170°C is between 1 h and 80 h, preferentially between 1 and 35 h and more preferably between 2 and 20 h.

[0107] Equivalent time t(eq) at 170°C is defined by the formula:

[0108] T (eq) = (J exp (-Q / RT')dt ) / exp - Q / RTref) where T' (in Kelvin) is the instantaneous treatment temperature, which changes with time t' (in hours), and Tref is a reference temperature set at 443 K (170°C). t(eq) is expressed in hours, with the constant R = 8.31 J / mol / K and the activation energy of the diffusion of Mg, Q = 130400 J / mol. The formula giving t(eq) takes account of the heating and cooling phases.

[0109] Applications for products according to the invention include automotive construction (e.g. body skins and reinforcements, shock-absorbing systems, battery boxes), building construction (e.g. carpentry, joinery, decoration, etc.), aircraft construction (e.g. fuselage, electrical connections, etc.) and industrial construction (e.g. pylons, vacuum chambers, railroad rails). The preferred application for products according to the invention is automotive construction.

[0110] EXAMPLES

[0111] Example 1

[0112] In this example, aluminum alloys were cast as in 250g, TP1 shape (The Aluminum Association, Standard Test Procedure for Aluminum Alloy Grain Refiners Washington D.C., 1990). Vickers hardness test were used as evaluation method.

[0113] The composition of the alloys tested is provided in Table 1

[0114] Table 1 - Alloy composition in wt.%

[0115] The results of the hardness measurement are provided in Table 2

[0116] Table 2 - Hardness measurements

[0117] As illustrated by example B, increasing the Fe content to about 0.5 wt.% results in a decrease of hardness from 131 to 122. This negative effect can be avoided by the addition of nickel. Example 2

[0118] In this example, aluminum alloys were cast as in billets of diameter 80 mm and 152 mm. Vickers hardness test were used as evaluation method.

[0119] The composition of the alloys tested is provided in Table 3

[0120] Table 3 - Alloy composition in wt.%

[0121] The results of the hardness measurement are provided in Table 4

[0122] Table 4 - Hardness measurements

[0123] The as-cast images of intermetallic particles of alloys H and I in billets of diameter 152 mm obtained by BSE contrast electron microscopy are shown in Figures 1 and 2, respectively.

[0124] The size distribution of intermetallic particles is provided in Figure 3. The alloy according to the invention have a smaller average intermetallic particle size. It is also observed that the intermetallic particles are more rounded

[0125] Example 3

[0126] Billets of diameter 152 mm of example 2 were homogenized and subsequently extruded into a flat strip having a thickness of 2.5 mm and a width of 50 mm to allow us to observe the performance of the alloy as extruded material. The extrudates were solution heat treated, quenched and aged to a T6 temper then evaluated for tensile properties and bending performance.

[0127] The results are provided in Table 5 Table 5 - Mechanical properties obtained on the extruded products

[0128] The results show that an addition of 0.2wt.% Ni to the alloy with 0.5 wt.% Fe enabled to mitigate the detrimental effect of the high-Fe. Since intergranular corrosion (IGC) is also one of the key performance indicators that needs to be evaluated, IGC test using the ISO 11846 B standard were also performed. The results show that the addition of 0.2 wt.% Ni the alloy with a Fe level of 0.5wt.% does not negatively impact the IGC resistance and it is still well below the maximum limit (< 300 pm). Therefore, a very good balance between strength, ductility and corrosion resistance can be obtained in the Ni-added high-Fe 6xxx alloys.

[0129] Table 6 - Intergranular corrosion evaluation based on the ISO 11846 B method

Claims

CLAIMS1. Aluminum-based alloy comprising, in % by weight,- Si: 0.3 - 1.4;- Mg: 0.1 - 1.2;- Cu: 0.02 - 1.2;- Mn : 0.02 - 1.0;- Ni: 0.1 - 0.4;- Fe: 0.3 - 0.6;- Cr: 0.05 - 0.4;- Ti: < 0.2;- Zr: < 0.3;- V : < 0.2;- Zn : < 1.0;- aluminum and unavoidable impurities.

2. Alloy according to claim 1 wherein the content of Si is from 0.4% to 1.1%, preferably from 0.6% to 1.0% and more preferably from 0.7% to 0.9%.

3. An alloy according to claim 1 or claim 2 wherein the content of Mg is from 0.3% to 1.0%, preferably from 0.3% to 0.9% and more preferably from 0.5% to 0.9%.

4. An alloy according to any one of claims 1 to 3 wherein the content of Cu is from 0.6% to 1.1% and preferably from 0.7% to 1.0%.

5. Alloy according to any one of claims 1 to 4 wherein the content of Mn is from 0.05% to 0.7%, preferably from 0.3% to 0.7% and more preferably from 0.4% to 0.6%.

6. Alloy according to any one of claims 1 to 5 wherein the content of Ni is from 0.1% to 0.4%, preferably from 0.15% to 0.35% and more preferably from 0.18% to 0.28%.

7. Alloy according to any one of claims 1 to 6 wherein the content of Fe is from 0.40% to 0.60% and preferably from 0.45% to 0.55%.

8. Alloy according to any one of claims 1 to 7 wherein the content of Cr is from 0.05% to 0.2%, preferably from 0.06% to 0.15% and more preferably from 0.08% to 0.13%.

9. Alloy according to any one of claims 1 to 8 wherein the content of Ti is from 0.01% to 0.10% and preferably from 0.02% to 0.08%.

10. Alloy according to any one of claims 1 to 9 wherein the content of Zr is from 0.10% to 0.20% and preferably from 0.12% to 0.18%.

11. Alloy according to any one of claims 1 to 10 wherein the content of V is at most 0.05% and preferably at most 0.04%.

12. Aluminum-based alloy according to any one of claims 1 to 11 comprising, in % by weight Si 0.4 - 1.1, Mg 0.3 - 0.9, Cu 0.1 - 0.8, Mn 0.05 - 0.7, Ni 0.1 - 0.4, Fe: 0.3 - 0.6, Cr 0.05 - 0.2, Ti < 0.2, Zr < 0.2, V < 0.15; Zn <1.0, aluminum and unavoidable impurities.

13. Heat-treated wrought product comprising an alloy according to any one of claims 1 to 12.

14. Heat treated wrought product according to claim 13 wherein the product is an extruded product.

15. A method of manufacturing a product according to claim 13 comprising the steps of- Supply pure or alloyed aluminum in the form of primary metal ingots from electrolysis and / or pre-consumer manufacturing scrap and / or post-consumer scrap, said scrap having optionally been melted down separately and possibly solidified, and of addition elements in suitable form;- Prepare a load with the supplied aluminum, melt this load and add the additives to obtain a bath of liquid metal in an alloy according to the invention,- Cast, preferably by vertical semi-continuous casting with direct cooling, said liquid metal bath to obtain a blank suitable for hot working, typically a rolling plate, a forging blank or an extrusion billet;- Homogenize the blank at a temperature of at least 500°C;- Hot-work and optionally cold-cold work the blank by rolling, extrusion and / or forging to obtain a wrought product;- Solution heat-treat the wrought product thus obtained at a temperature of at least 500°C and quench;- Natural age and / or artificially age the solution heat treated and quenched wrought product thus obtained.

16. Method according to claim 13 in which the load contains at least 30% post-consumer scrap.

17. Use of a product according to claim 12 in automobile construction, building construction, aircraft construction or industrial construction.

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