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

Abstract

A method of producing an integrated monolithic aluminum structure including providing an 7xxx-series aluminum alloy plate with a predetermined thickness of at least 10 mm, and wherein the plate has been solution heat treated and stretched, heat-treating the plate product in a first of a plurality of artificial ageing steps required to achieve a final temper state, high-energy hydroforming the plate against a forming surface of a rigid die having a contour with a desired curvature of the integrated monolithic aluminum structure, the high energy forming causing the aluminum alloy plate to conform to the forming surface contour to at least one of a uniaxial curvature and a biaxial curvature, heat-treating the integrated monolithic aluminum structure through a remaining ageing step of the ageing steps to achieve a desired final temper, and machining the high-energy formed structure to a near-final or final machined 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 7xxx-series aluminum alloy solution heat-treated, cooled and stretched plate with a predetermined thickness of at least 10 mm; heat-treating the aluminum alloy plate in a first artificial ageing step of a plurality of artificial ageing steps required to achieve a final temper state; optionally, either before or after the first ageing step, a pre-machining operation of the aluminum alloy plate to an intermediate machined structure; high-energy hydroforming the aluminum alloy plate or the intermediate machined structure against a forming surface of a rigid die having a contour at least substantially in accordance with a desired curvature of the integrated monolithic aluminum structure, the high energy forming causing the aluminum alloy plate or the intermediate machined structure to substantially conform to the contour of the forming surface to at least one of a uniaxial curvature and a biaxial curvature; heat-treating the integrated monolithic aluminum structure through a remaining artificial ageing step of the plurality of artificial ageing steps to achieve a desired final temper, the desired final temper preferably selected from the group of T6 and T7; and machining or mechanical milling the high-energy formed structure to a near-final or final machined integrated monolithic aluminum structure.

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, in that order, the high-energy hydroformed structure is machined to a near-final or final machined integrated monolithic aluminum structure and then artificial aged to a desired final temper.

25. The method according to claim 21, wherein, in that order, the high-energy hydro formed structure is artificial aged to a desired final temper and then machined to a near-final or final machined integrated monolithic aluminum structure.

26. The method according to claim 21, wherein the high-energy hydroformed structure is stress-relieved, by compressive forming, followed by machining and artificial ageing to a desired final temper of the integrated monolithic aluminum structure.

27. The method according to claim 21, wherein the high-energy hydroformed structure is stress-relieved, by compressive forming in a next high-energy hydroforming step, followed by machining and artificial ageing to a desired final 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 19 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 a time delay between solution heat-treatment of the 7xxx-series aluminum alloy plate material and the first artificial ageing step of a plurality of ageing steps required to achieve a final temper state is at least 168 hours.

31. The method according to claim 21, wherein the first artificial ageing step comprises heat treating the aluminum alloy plate at a temperature of at least 70° C.

32. The method according to claim 31, wherein the first artificial ageing step comprises heat treating the aluminum alloy plate at temperature for 3 to 20 hours.

33. The method according to claim 21, wherein the remaining artificial ageing step comprises heat treating the high-energy hydroformed structure at a temperature of at least 130° C.

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

35. 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%, and Cu up to 2.5%.

36. The method according to claim 35, wherein the 7xxx-series aluminum alloy has a composition comprising, in wt. %: TABLE-US-00004 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: TABLE-US-00005 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%, and impurities and balance aluminum.

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

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

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

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

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The invention shall also be described with reference to the appended drawings, in which:

[0074] FIG. 1 shows a flow chart illustrating one embodiment of the method according to this invention; and

[0075] FIG. 2 shows a flow chart illustrating another embodiment of the method according to this invention.

[0076] 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

[0077] In FIG. 1 the method comprises, in that order, a first process step of providing a 7xxx-series aluminum alloy plate material having been solution heat treated, cooled and stretched and having a predetermined thickness of at least 10 mm. Then the plate material is heat-treated in a first artificial ageing step of a plurality of ageing steps required to achieve a final temper state (a T6 or a T7 temper). The purpose of which is to prevent further natural ageing and creating stable properties in the aluminum alloy plate.

[0078] Upon performing the first ageing step and prior to the high-energy hydroforming operation, the intermediate aluminum alloy plate product having stable mechanical properties may be stored in inventory or delivered or transported to another location or facility for further processing.

[0079] In a next process step, the aged plate material is pre-machined (this is an optional process step and on a less preferred basis can be performed prior to the first ageing 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.

[0080] In a preferred embodiment, the high-energy hydroformed structure is stress relieved after the high-energy hydroforming operation, more preferably in an operation including in a cold compression type of operation.

[0081] Then, there is either machining or mechanical milling of the high-energy hydroformed structure to a near-final or final machined integrated monolithic aluminum structure, followed by artificial ageing of the machined integrated monolithic aluminum structure to the desired final temper (preferably a T6 or T7 temper) to develop the required strength and other engineering properties relevant for the intended application of the integrated monolithic aluminum structure.

[0082] Or, in an alternative embodiment, there is firstly artificial ageing of the high-energy hydroformed structure to a desired final temper (preferably a T6 or T7 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 high-energy formed structure in its final temper into a near-final or final machined integrated monolithic aluminum structure.

[0083] 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, and 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.

[0084] 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 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). An aluminum 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 the 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 FIG. 3C. 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.

[0085] 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.