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High strength Al-Zn alloy and method for producing such an alloy product

Inactive Publication Date: 2005-02-17
ALERIS ALUMINUM KOBLENZ GMBH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

It is therefore the object of the present invention to provide an improved Al—Zn alloy preferably for plate products with high strength and an improved balance of toughness and corrosion performance. More specifically, it is the object of the present invention to provide an alloy which can be used for upper wing applications in aerospace with an improved compression yield strength with properties which are better than the properties of a conventional AA7055-alloy in the T77 temper.
It is another object of the invention to obtain an AA7000-series aluminium alloy which exhibits strength in the range of T6-type tempers and toughness and corrosion resistance properties in the range of T73-type tempers.
It is furthermore an object of the present invention to provide an alloy that can be used in an age-creep forming process, which is an alloy which does not need a complicated or cumbersome ageing process.

Problems solved by technology

However, these applications result in exposure to a wide variety of climatic conditions necessitating careful control of working and ageing conditions to provide adequate strength and resistance to corrosion, including both stress corrosion and exfoliation.
It has been reported that the known precipitation-hardened aluminium alloys AA7075 and other M7000-series alloys, in the T6 temper condition, have not given sufficient resistance to corrosion under certain conditions.
However, the three step ageing procedure is cumbersome and difficult to perform so that the costs for producing such alloy increase.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

Tests were performed comparing the performance of the alloy according to the present invention and AA7150-T77 alloys. It has been found that the examples of the alloy of the present invention show an improvement over conventional AA7150-T77-temper alloys.

On an industrial scale four different aluminium alloys have been cast into ingots, homogenized, preheated for more than 6 hours at 410° C. and hot rolled to 30 mm plates. Thereafter, the plates were solution heat treated at 475° C. and water quenched. Thereafter, the quenched product was aged by a two-step T79-T76 ageing procedure. The chemical compositions are set out in Table 1.

TABLE 1Chemical composition of thin plate alloys, in wt. %,balance aluminium and inevitable impurities, Alloys1 to 4 with Mn ≦ 0.02:SiFeCuMnMgCrZnTiZrAlloy 10.030.062.230.002.080.006.240.030.10(7050)Alloy 20.050.082.050.012.040.016.180.040.11Alloy 30.050.092.200.012.300.017.030.040.10Alloy 40.040.071.910.022.130.006.940.030.11

The aged alloys were ther...

example 2

When higher strength levels are required and toughness properties are less important conventional AA7055-T77 alloys are preferred instead of AA7150-T77 alloys as an alloy for upper wing applications. The present invention therefore disclosed optimised copper and magnesium windows which show properties equal or better than conventional AA7055-T77 alloys.

11 different aluminum alloys were cast into ingots having the following chemical composition as set out in Table 5.

TABLE 5Chemical composition of 11 alloys, in wt. %, balancealuminium and inevitable impurities, Zr = 0.08,Si = 0.05, Fe = 0.08.AlloyCuMgZnMn12.402.208.20.0021.942.338.20.0031.262.328.10.0042.361.948.10.0051.941.928.10.0061.302.098.20.0071.921.548.10.0081.271.578.10.0092.342.258.10.07102.382.098.10.00112.351.538.20.00

Strength and toughness properties were measured after pre-heating the cast alloys for 6 hours at 410° C. and then hot rolling the alloys to a gauge of 28 mm. Thereafter, solution heat treating was applie...

example 3

The influence of manganese was investigated on the properties of the inventive alloy. An optimum manganese level was found between 0.05 and 0.12 in alloys with a high amount of zinc. The results are shown in Tables 7 and 8. All not mentioned chemistry properties and processing parameters are similar to those of Example 2.

TABLE 7Chemical composition of three alloys (Mn-0, Mn-1 and Mn-2), in wt. %, balance aluminium and inevitable impurities,Zr = 0.08, Si = 0.05, Fe = 0.08.AlloyCuMgZnMnMn-01.942.338.20.00Mn-11.942.278.10.06Mn-21.962.298.20.12

TABLE 8Overview of strength and toughness of three alloys accordingto Table 7 in the identified directions.RpRmKqAlloyLLTLLTL - TMn-061456164260429.3Mn-161256263560231.9Mn-261256063959629.9

As shown in Table 8 the toughness properties decrease while strength properties increase. For alloys with high amounts of zinc an optimised manganese level is between 0.05 and 0.12.

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Abstract

The present invention relates to a high strength Al—Zn alloy product with an improved combination of corrosion resistance and toughness, the alloy including essentially (in weight percent): Zn: 6.0-9.5, Cu: 1.3-2.4, Mg: 1.5-2.6, Mn and Zr<0.25 but preferably in a range between 0.05 and 0.15 for higher Zn contents, other elements each less than 0.05 and less than 0.25 in total, balance aluminium, wherein (in weight percent): 0.1[Cu]+1.3<[Mg]<0.2[Cu]+2.15. The invention also relates to a method to produce these alloy products, and to some preferred applications thereof such as upper wing applications in aerospace.

Description

FIELD OF THE INVENTION The present invention relates to a wrought high strength Al—Zn alloy product with an improved combination of corrosion resistance and toughness, a method for producing a wrought high strength Al—Zn alloy product with an improved combination of corrosion resistance and toughness and a plate product of such alloy, optionally produced in accordance with the method. More specifically, the present invention relates to a wrought high strength Al—Zn alloy designated by the 7000-series of the international nomenclature of the Aluminium Association for structural aeronautical applications. Even more specifically, the present invention relates to a new chemistry window for an Al—Zn alloy product having improved combinations of strength, toughness and corrosion resistance, which does not need specific ageing or temper treatments. BACKGROUND OF THE INVENTION It is known in the art to use heat treatable aluminium alloys in a number of applications involving relatively hi...

Claims

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Application Information

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IPC IPC(8): C22C21/00C22C21/10C22F1/053
CPCC22F1/053C22C21/10
Inventor BENEDICTUS, RINZEKEIDEL, CHRISTIAN JOACHIMHEINZ, ALFRED LUDWIG
Owner ALERIS ALUMINUM KOBLENZ GMBH
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