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Wrought aluminium AA7000-series alloy product and method of producing said product

a technology of wrought aluminium and alloys, applied in the field of wrought aluminium aa7000series alloy products and methods of producing said products, can solve the problems of stress corrosion cracking of alloys aa7075, exfoliation corrosion, etc., and achieve the effect of improving strength and toughness properties and reducing hot crack sensitivity during welding

Inactive Publication Date: 2007-07-05
CORUS ALUMINUM WALZPRODUKTE GMBH (DE)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006] It is an object of this invention to provide a wrought alloy product, ideally for aerospace application or tooling plate, of the AA7000-series having a combination of improved strength and toughness properties and reduced hot crack sensitivity during welding, relative to at least one alloy selected from the group consisting of AA7050 or AA7075 and, when in an artificially aged condition, having a hardness of more than 180 HB.
[0007] It is another object of this invention to provide a wrought alloy product of the AA7000-series having a combination of improved IGC-resistance, improved strength properties, reduced hot crack sensitivity during welding and, when in an artificially aged condition, having a hardness of more than 180 HB.
[0008] It is yet another object of this invention to provide a wrought alloy product of the AA7000-series having a combination of good weldability, improved strength properties and, when in an artificially aged condition, having a hardness of more than 180 HB.
[0009] It is also an object of this invention to provide a method for producing a wrought alloy product of the AA7000-series having a combination of improved strength and toughness properties, reduced hot crack sensitivity during welding and, when in an artificially aged condition, having a hardness of more than 180 HB or a wrought alloy product of the AA7000-series having a combination of improved IGC-resistance, improved strength properties, reduced hot crack sensitivity during welding and, when in an artificially aged condition, having a hardness of more than 180 HB which can be executed more economically than currently known and practiced industrial scale methods.
[0018] and balance aluminium, the product having reduced hot crack sensitivity, also having improved strength and toughness properties, and when in artificially aged condition having a hardness of more than 180 HB.

Problems solved by technology

In this condition however, alloys AA7075 and similar alloys are susceptible to stress corrosion cracking (“SCC”), exfoliation corrosion (“EXCO”) and intergranular corrosion (“IGC”).
It is known that higher strengths can be obtained by higher levels of alloying additions (in particular Zn, Mg and Cu) but this increase in strength leads to lower toughness values.
In addition thereto, the high copper content of the aforementioned alloys makes them susceptible to hot cracking after welding.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0113] Lab ingots of chemistries A.1 to A.7 indicated in Table 1 have been cast and processed according to the following route (v=heating rate, @=at): [0114] Homogenisation: v=30° C. / h+12 h @ 470° C., [0115] Pre-heat: v=35° C. / h+6 h @ 420° C., [0116] Hot rolling: from 80 mm gauge to 30 mm, [0117] SHT: v=as fast as possible, 2 h @ 470° C. followed by water quench, [0118] Stretching: 1.5%,

[0119] Ageing: T76, v=30° C. / h+5 h@120° C. / h plus v=15° C. / h+12 h@145° C. / h.

TABLE 1Composition of alloys in wt. % (0.06 Fe, 0.04 Si, 0.04 Ti, 0.10 Zr,balance aluminium), mechanical properties (L direction) and fracturetoughness (L-T direction) of the alloys.RpRmKIC*AlloyZnMgCu(MPa)(MPa)(MPa{square root over (m)})AA7055-ref. AMS 420659361424.2T7751AA7449-ref. AMS 425053857924.2T7651A.17.52.80.1553154970.1A.27.44.20.1658961440.6A.39.51.90.1655455862.1A.49.52.30.1558059541.3A.59.52.80.1562363630.8A.69.43.30.1764766626.4A.711.02.80.1865966924.2

*KIC is fracture toughness

[0120] As is apparent from Tabl...

example 2

[0121] Lab ingots of chemistries B.1 to B.4 as indicated in Table 2 have been cast and processed according to the route described above except that the final hot rolling thickness was 3 mm and that the alloy B.2 has been homogenised for a longer time (12 h @470° C. followed by 24 h @475° C.) wherein the homogenisation step comprises a first and a second stage.

TABLE 2Composition of alloys in wt. %(0.06 Fe, 0.04 Si, 0.04 Ti, 0.10 Zr, balance aluminium)RpAlloyZnMgCu(MPa)EXCOB.19.32.30.16565EA / BB.29.42.30.80564ECB.39.32.80.16598EAB.410.72.80.15626EA

[0122] The mechanical (L-direction) and corrosion (EXCO, measured according to the standard ASTM G34-97) properties of the alloys are also shown in Table 2. An 0.8% Cu level (see alloy B.2) does not improve the mechanical properties, but has an adverse influence on the corrosion behaviour of the alloy. On the other hand, Mg and Zn additions (see alloys B.3 and B.4) lead to better corrosion properties and to a considerable strength increase....

example 3

[0123] Seven alloys with compositions as given in Table 3 were investigated. Most alloys (C.1-C.5) have low Cu levels and some contain more Cu (alloy C.6, C.7). They were all processed to 3.5 mm gauge plate according to the following route: [0124] Casting of ingots, machining rolling blocks of 80×80×100 mm3 out of the ingots. [0125] Homogenisation: v=30° C. / hr+470° C. @ 12 hrs for Cu≦0.20%, v=30° C. / hr+470° C. @ 12 hrs, v=15° C. / hr+475° C. @ 24 hrs for Cu>0.20%, [0126] Hot rolling: preheat @ 430° C., rolled from 80 mm to 3.5 mm thickness, [0127] SHT: 1 hr @ 470° C., followed by quenching in water or oil, [0128] stretching: 1.5%, [0129] After SHT, all the alloys in this example were aged into T6 temper.

[0130] Before artificial ageing the alloys were quenched in both water and oil, to investigate the quench sensitivity of the alloys. The oil quench is comparable to the quench rate in the core of a about 70 mm thick plate, where the plate core cannot be quenched as fast as the surface...

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Abstract

A wrought aluminium AA7000-series alloy product, including (in wt %): Zn 7.5 to 14.0, Mg 1.0 to 5.0, Cu<0.28, Fe<0.30, Si<0.25, and one or more members selected from the group of: Zr<0.30, Ti<0.30, Hf<0.30, Mn<0.80, Cr<0.40, V<0.40, and Sc<0.70, remainder: incidental elements and impurities, each <0.05, total <0.15, and balance aluminium. The product having reduced hot crack sensitivity, and improved strength and toughness properties, and when in artificially aged condition having a hardness of more than 180 HB.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This claims the benefit of U.S. provisional patent application No. 60 / 702,303, filed Jul. 26, 2005, and European patent application No. 05076673.2, filed Jul. 21, 2005, both incorporated herein by reference in their entirety.FIELD OF THE INVENTION [0002] This invention pertains to a weldable wrought aluminium AA7000-series alloy in the form of a rolled, extruded or forged product and to a method of producing said product. The invention further relates to a welded component comprising such a product. BACKGROUND TO THE INVENTION [0003] As will be appreciated herein below, except as otherwise indicated, alloy designations and temper designations refer to the Aluminum Association designations in Aluminum Standards and Data and the Registration Records, as published by the Aluminum Association. [0004] For any description of alloy compositions or preferred alloy compositions, all references to percentages are by weight percent unless otherwise...

Claims

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Application Information

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IPC IPC(8): C22C21/10
CPCC22C21/10
Inventor BUERGER, ACHIMSPANGEL, SABINE MARIAVAN DE LANGKRUIS, JORGENMORRA, PAOLA VALENTINA ABSALABENEDICTUS, RINZEBOEZEWINKEL, JOHANSENGO, SABRIHEINZ, ALFRED LUDWIGMORTIZ, CLAUS JURGENNORMAN, ANDREWKHOSLA, SUNIL
Owner CORUS ALUMINUM WALZPRODUKTE GMBH (DE)
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