METHOD OF PRODUCING A HIGH-ENERGY HYDROFORMED STRUCTURE FROM A 7XXX-SERIES ALLOY

Abstract

A method of producing an integrated monolithic aluminum structure, the method includes the steps of: (a) providing an aluminum alloy plate with a predetermined thickness of at least 38.1 mm, wherein the aluminum alloy plate is a 7xxx-series alloy provided in an F-temper or an O-temper; (b) optionally pre-machining of the aluminum alloy plate to an intermediate machined structure; (c) high-energy hydroforming of the plate or optional intermediate machined structure against a forming surface of a rigid die having a contour in accordance with a desired curvature of the integrated monolithic aluminum structure, the high-energy hydroforming causing the plate or the intermediate machined structure to conform to the contour of the forming surface to at least one of a uniaxial curvature and a biaxial curvature; (d) solution heat-treating and cooling of the high-energy hydroformed structure; (e) machining and (f) ageing of the final integrated monolithic aluminum structure.

Claims

1-20. (canceled)

21. A method of producing an integrated monolithic aluminum structure, the method comprising the steps of: providing an aluminum alloy plate with a predetermined thickness of at least 38.1 mm, wherein the aluminum alloy plate is a 7xxx-series alloy provided in an F-temper or an O-temper; optionally pre-machining of the aluminum alloy plate to an intermediate machined structure; high-energy hydroforming of the plate or optional intermediate machined structure into a high-energy hydroformed structure against a forming surface of a rigid die having a contour in accordance with a desired curvature of the integrated monolithic aluminum structure, the high-energy hydroforming causing the plate or the intermediate machined structure to conform to the contour of the forming surface to at least one of a uniaxial curvature and a biaxial curvature; solution heat-treating and cooling of the high-energy hydroformed structure; machining of the solution heat-treated high-energy formed structure to a final machined integrated monolithic aluminum structure; and ageing of the final integrated monolithic aluminum structure to a desired temper.

22. The method according to claim 21, wherein the high-energy hydroforming step is by explosive forming.

23. The method according to claim 21, wherein the high-energy hydroforming step is by electrohydraulic forming.

24. The method according to claim 21, wherein following solution heat-treating and cooling of the high-energy hydroformed structure, in that order, the solution heat-treated high-energy formed structure is machined to a final machined integrated monolithic aluminum structure and then aged to a desired temper.

25. The method according to claim 21, wherein following solution heat-treating and cooling of the high-energy hydroformed structure, in that order, the solution heat-treated high-energy formed structure is aged to a desired temper and then machined to a final machined integrated monolithic aluminum structure.

26. The method according to claim 21, wherein following solution heat-treating and cooling of the high-energy hydroformed structure, said solution heat-treated structure is stress-relieved, by compressive forming, followed by machining and ageing to a desired temper of the integrated monolithic aluminum structure.

27. The method according to claim 21, wherein following solution heat-treating and cooling of the high-energy hydroformed structure, said solution heat-treated structure is stress-relieved, preferably by compressive forming in a next high-energy hydroforming step, followed by machining and ageing to a desired temper of the integrated monolithic aluminum structure.

28. The method according to claim 21, wherein the predetermined thickness of the aluminum alloy plate is at least 50.8 mm.

29. The method according to claim 21, wherein the predetermined thickness of the aluminum alloy plate is at most 127 mm.

30. The method according to claim 21, wherein the ageing of the integrated monolithic aluminum structure is to a desired temper selected from the group of: T4, T5, T6, and T7.

31. The method according to claim 21, wherein the ageing of the integrated monolithic aluminum structure is to a T7 temper.

32. The method according to claim 21, wherein the 7xxx-series aluminum alloy has a composition comprising, in wt. %: TABLE-US-00002 Zn 5.0% to 9.8%, Mg 1.0% to 3.0%, Cu up to 2.5%.

33. The method according to claim 21, wherein the 7xxx-series aluminum alloy has a composition comprising, in wt. %: TABLE-US-00003 Zn 5.0% to 9.8%, Mg 1.0% to 3.0%, Cu up to 2.5% and optionally one or more elements selected from the group consisting of: Zr up to 0.3%, Cr up to 0.3%, Mn up to 0.45%, Ti up to 0.15%, preferably up to 0.1%, Sc up to 0.5%, Ag up to 0.5%, Fe up to 0.25%, preferably up to 0.15%, Si up to 0.25%, preferably up to 0.12%, impurities and balance aluminum.

34. The method according to claim 21, wherein the 7xxx-series aluminum alloy has a Cu-content of 1.0% to 2.5%.

35. The method according to claim 21, wherein the 7xxx-series aluminum alloy has a Cu-content of up to 0.3%.

36. The method according to claim 21, wherein the solution heat-treatment is at a temperature in a range of 400° C. to 560° C.

37. The method according to claim 21, wherein the pre-machining and final machining comprises high-speed machining, preferably comprises numerically-controlled machining.

38. An integrated monolithic aluminum structure manufactured by the method according to claim 21.

39. A method of producing an aircraft structural part by producing an integrated monolithic aluminum structure according to the method of claim 21.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The invention shall also be described with reference to the appended drawings, in which:

[0075] FIG. 1 shows a flow chart illustrating one embodiment of the method according to this invention; and

[0076] FIG. 2 shows a flow chart illustrating another embodiment of the method according to this invention.

[0077] FIGS. 3A, 3B and 3C show cross-sectional side-views of an aluminum plate progressing through stages of a forming process from a rough-shaped metal plate into a shaped, near-finally shaped and finally-shaped workpiece, according to aspects of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] In FIG. 1 the method comprises, in that order, a first process step of providing an 7xxx-series aluminum alloy plate material in an F-temper or O-temper and having a predetermined thickness of at least 38.1 mm. In a next process step the plate material is pre-machined (this is an optional process step) into an intermediate machined structure and subsequently high-energy hydroformed, preferably by means of explosive forming or electrohydraulic forming, into a high-energy hydroformed structure with least one of a uniaxial curvature and a biaxial curvature. In a next process step there is solution heat-treating (“SHT”) and cooling of the high-energy hydroformed structure. In a preferred embodiment following SHT and cooling the intermediate product is stress relieved, more preferably in an operation including in a cold compression type of operation.

[0079] Then there is either machining or mechanical milling of the solution heat-treated high-energy formed structure to a near-final or final machined integrated monolithic aluminum structure, followed by ageing of the machined integrated monolithic aluminum structure to a desired temper to develop the required strength and other engineering properties relevant for the intended application of the integrated monolithic aluminum structure.

[0080] Or, in an alternative embodiment, there is firstly ageing of intermediate integrated monolithic aluminum structure to a desired temper to develop the required strength and other engineering properties relevant for the intended application of the integrated monolithic aluminum structure, for example an T7452 or T7652 temper, followed by machining or mechanical milling of the aged high-energy formed structure into a near-final or final machined integrated monolithic aluminum structure.

[0081] The method illustrated in FIG. 2 is closely related to the method illustrated in FIG. 1, except that in this embodiment there is a first high-energy hydroforming step, followed by a solution heat-treatment and cooling. Then at least one second high-energy hydroforming step is performed, the purpose of which is at least stress relief, followed by the ageing and machining as in the method illustrated in FIG. 1.

[0082] FIGS. 3A, 3B and 3C show a series in progression of exemplary drawings illustrating how an aluminum plate may be formed during an explosive forming process that can be used in the forming processes according to this invention. According to an explosive forming assembly 80a, a tank 82 contains an amount of water 83. A die 84 defines a cavity 85 and a vacuum line 87 extends from the cavity 85 through the die 84 to a vacuum (not shown). Aluminium plate 86a is held in position in the die 84 via a hold-down ring or other retaining device (not shown). An explosive charge 88 is shown suspended in the water 83 via a charge detonation line 89, with charge detonation line 19a connected to a detonator (not shown). As shown in FIG. 3B, the charge 88 (shown in FIG. 3A) has been detonated in explosive forming assembly 80b creating a shock wave “A” emanating from a gas bubble “B”, with the shock wave “A” causing the deformation of the aluminum plate 86b into cavity 85 until the aluminum plate 86c is driven against (e.g., immediately proximate to and in contact with) the inner surface of die 84 as shown in the explosive forming assembly 80c of FIG. 3C.

[0083] Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made without departing from the spirit or scope of the invention as herein described.

[0084] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.