WO2009003679A1 - Crack stopper and method of manufacturing a crack stopper - Google Patents

Crack stopper and method of manufacturing a crack stopper Download PDF

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Publication number
WO2009003679A1
WO2009003679A1 PCT/EP2008/005365 EP2008005365W WO2009003679A1 WO 2009003679 A1 WO2009003679 A1 WO 2009003679A1 EP 2008005365 W EP2008005365 W EP 2008005365W WO 2009003679 A1 WO2009003679 A1 WO 2009003679A1
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WO
WIPO (PCT)
Prior art keywords
max
brazing
sheet
titanium
aluminium
Prior art date
Application number
PCT/EP2008/005365
Other languages
French (fr)
Inventor
Jacobus Van Rijkom
Adrianus Jacobus Wittebrood
Original Assignee
Aleris Aluminum Koblenz Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aleris Aluminum Koblenz Gmbh filed Critical Aleris Aluminum Koblenz Gmbh
Priority to DE112008001659.3T priority Critical patent/DE112008001659B4/en
Publication of WO2009003679A1 publication Critical patent/WO2009003679A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
    • B32B15/017—Layered products comprising a layer of metal all layers being exclusively metallic one layer being formed of aluminium or an aluminium alloy, another layer being formed of an alloy based on a non ferrous metal other than aluminium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K1/00—Soldering, e.g. brazing, or unsoldering
    • B23K1/19—Soldering, e.g. brazing, or unsoldering taking account of the properties of the materials to be soldered
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
    • B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering, brazing
    • B23K35/0233—Sheets, foils
    • B23K35/0238—Sheets, foils layered
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C14/00—Alloys based on titanium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/10—Alloys based on aluminium with zinc as the next major constituent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/08—Non-ferrous metals or alloys
    • B23K2103/10—Aluminium or alloys thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/08—Non-ferrous metals or alloys
    • B23K2103/14—Titanium or alloys thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/18—Dissimilar materials

Definitions

  • the invention relates to metallic crack stopper materials for application in a structural part of an aerospace vehicle and to a method of manufacturing such crack stopper materials.
  • the invention further relates to the use such crack stopper materials in amongst others a structural part of an aerospace vehicle.
  • aluminium 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 in 2006. For any description of alloy compositions or preferred alloy compositions, all references to percentages are by weight percent unless otherwise indicated.
  • the cracker stopper can be fastened to the structure by all means known in the art, such as for example by means of screws, rivets, adhesion, or welding, or combinations thereof.
  • a crack stopper as used here is a more general expression for what is also known in the art as “doubler” or “strap".
  • the method according to this invention results in a wholly metallic laminate product wherein the titanium or titanium alloy sheet is firmly bonded to an aluminium alloy sheet.
  • the metal laminate is for use as crack stopper and ideally is used for application in an aerospace vehicle.
  • the combined use of titanium and aluminium provides for a metal laminate having a high strength and stiffness due to the high modulus of elasticity of the titanium while having a lower specific density compared to a fully titanium product of similar gauge as the metallic laminate. In this way considerable weight is saved while the metallic laminate is still offering sufficient crack stopper capability.
  • the titanium can be bonded to the aluminium alloy sheet by means of a rolling operation.
  • the rolling is preferably carried out at a temperature of 150 0 C or less as higher rolling temperatures adversely affect the surface quality of the titanium sheet.
  • the rolling operation is carried out as a cold rolling operation, which means at a temperature of less than 50 0 C and preferably at ambient temperature.
  • the aluminium sheet and titanium sheets are pre-treated prior to roll bonding using techniques regular in the art, and which would involve degreasing, cleaning, and where necessary also grinding.
  • Brazing employs a filler metal, also referred to as a brazing alloy, having a liquidus above 45O 0 C and below the solidus of the base metal.
  • a filler metal also referred to as a brazing alloy
  • the titanium or titanium alloy sheet on one or both sides is bonded to the aluminium alloy sheet by means of an intermediate layer interposed between said titanium or titanium alloy sheet and said aluminium alloy sheet to form an intermediate sandwich product bonded by means of brazing to form the metal laminate, and wherein said intermediate layer is an aluminium brazing alloy. It is possible to bond the titanium or titanium alloy sheet directly to the aluminium alloy sheet in a brazing operation.
  • the titanium or titanium sheet is bonded to the aluminium alloy layer via the intermediate layer of aluminium brazing alloy forming an intermediate sandwich product, and then in a subsequent rolling operation a first metallic bond is established between the various metal layers in the intermediate sandwich product, where after the sandwich product is subjected to a brazing operation to form the crack stopper in the form of the metal laminate. In this way a strong bond is being obtained between the metal layers.
  • the aluminium brazing alloy is preferably an AISi brazing alloy, e.g. an AA4xxx-series aluminium alloy, comprising about 5 to 18% Si, and preferably about 6 to 14%.
  • the amount of Fe depends primarily on the origin of the alloy material and can be up to about 0.8%, and preferably is not more than about 0.6%.
  • grain refiner element Ti can be present in a range of up to about 0.2%, preferably up to about 0.15%. The balance is made by unavoidable impurities and aluminium.
  • the AISi brazing material further comprises Mg in a range of about 0.02 to 4%, and preferably about 0.02 to 1.5%.
  • Mg is to further enhance the brazeability in a vacuum brazing operation or in a controlled atmosphere brazing operation in the absence of a flux.
  • the AISi brazing alloy further contains a wetting element, preferably one or more wetting elements selected from the group comprising Bi, Pb, Li, Sb, and Th, and wherein the total amount of the wetting elements is in a range of about 0.01 to 0.5%.
  • the element Bi is selected from the group of wetting elements and is in a range of about 0.01 to 0.5%, and preferably in a range of about 0.01 to 0.1%, as being the most efficient wetting element for this purpose in this alloy system during a brazing operation.
  • an AISi based brazing material is preferred.
  • other aluminium brazing alloys can be used on a less preferred basis, such as AICuSn and AIAgCu fillers. It has been found, however, that these fillers can form undesirable fracture at the interface of the brazing material and the titanium base metals.
  • the aluminium brazing alloy is interposed between the aluminium alloy sheet and the titanium or titanium alloy sheet in the form of a brazing sheet product.
  • a brazing sheet product comprises of a core, typically of an aluminium alloy on one or both sides bonded to the aluminium brazing alloy.
  • the aluminium brazing alloy may be bonded to the core alloy in various ways, for example by means of roll bonding, cladding spray-forming, or semi-continuous or continuous casting processes.
  • the brazing operation in the method of this invention is preferably carried out in a vacuum brazing operation or in a controlled atmosphere brazing operation devoid of the use of a brazing flux material.
  • Controlled atmosphere brazing is typically carried out in a dry environment, and preferably using an argon or helium atmosphere.
  • Typical brazing temperatures for the method according to this invention are in the range of about 540 0 C to
  • the metal sheets are being kept flat by using appropriate means, for example by applying a pressure force or by clamping the laminate product between for example two thin plates.
  • the bonding of the metal laminate can be further improved by means of a deformation operation, typically carried out as a rolling operation whereby the total rolling reduction should be less than about 30%, preferably less than about 20%.
  • a deformation operation typically carried out as a rolling operation whereby the total rolling reduction should be less than about 30%, preferably less than about 20%.
  • the metal laminate can be stretched, for example up to about 2%, in order to improve on the flatness of the metal laminate.
  • the aluminium alloy sheet bonded to the titanium or titanium alloy sheet is preferably one selected from the group consisting of AA2xxx, AA3xxx, AA ⁇ xxx, AA ⁇ xxx, and AA7xxx- series alloys.
  • the AA5xxx-series alloys would include Al-Mg-Sc alloys.
  • Al-Li or AICuLi- based alloys can be used for manufacturing the crack stopper according to this invention.
  • the titanium alloy used for the bonding to the aluminium alloy sheet can be any titanium alloy qualified for use in an aerospace structure and having the required strength and stiffness and other engineering properties for the specific application.
  • the titanium sheet has a composition, in wt.%: Al 5.0 to 6.75, preferably 5.5 to 6.75
  • V 3.0 to 5.0, preferably 3.5 to 4.5
  • This compositional range would include TiAI6V4 or Ti-6-4 grade products providing the desired strength and stiffness and are qualified for various load-bearing constructions of aerospace applications.
  • the titanium alloy used for the bonding to the aluminium alloy sheet is a non-alloyed titanium sheet, in particular those having a chemical composition within the ranges, in wt.%:-
  • Fe 0.35 max. preferably 0.15 max., O 0.35 max., preferably 0.12 max.
  • H 0.015% max. preferably 0.013% max., impurities each 0.1% max., total 0.4% max., balance titanium.
  • the metal laminate according to the invention can be built up by two or more metal layers, for example titanium or titanium alloy sheet bonded on one side only to an aluminium alloy sheet or a titanium plate bonded on both sides to an aluminium alloy sheet or even a multi-layered product of for example an arrangement of aluminium-titanium-aluminium- titanium layers.
  • the use of more than one layer is favoured as it forms more barriers to be taken by a continuing crack propagation and thereby an enhanced functioning as crack stopper.
  • the total thickness of all titanium sheets is at least about 50% of the total thickness of the metal laminate. On a more preferred basis it is at least 60% of the total metal laminate thickness.
  • the metal laminate manufactured according to this invention has preferably a gauge in a range of about 0.4 to 15 mm. A more preferred upper limit is about 12 mm, and a preferred lower limit is about 1 mm.
  • the width of the crack stopper is chosen on its functional requirements, and would typically go up to about 20 cm.
  • it relates to a wing section and to a fuselage section of an aerospace vehicle reinforced locally with at least one crack stopper made from the Al-Ti laminate manufactured by the method according to this invention.
  • the crack stopper can be in the form of a doubler sheet or thin plate or a strap.
  • the method of bonding the metal laminate is selected from the group comprising of brazing, rolling, cold rolling, or any combination thereof.
  • crack stopper is rendered ideally suitable for application in aerospace vehicles, such as commercial and military aircraft, it can be used for a similar purpose in a vessel, a pressure vessel, a road tanker, a storage silo, or in pipes.
  • Example 1 A metal laminate product had been produced from an about 0.4 mm brazing sheet product consisting of an AA3xxx-series core alloy clad on both sides with an AA4104 brazing alloy (each cladding having a thickness of 8% of the brazing sheet thickness) and wherein said brazing sheet has been sandwiched between commercial available Ti-grade 5 sheets of 0.55 mm thickness. All sheets had dimensions of 100 by 300 mm. The Ti sheets have been pre-treated by grinding and cleaning. The whole metal laminate product had been clamped between two steel plates and vacuum brazed at 595°C for about 3 minutes. The resultant product is a metal laminate product consisting of two Ti sheets firmly bonded to each other via aluminium alloys formed by the brazing sheet product. The metal laminate product having a thickness of about 1.5 mm can be used as a crack stopper.
  • a metal laminate product had been product from a commercial available TiAI6V4 sheet of 1.5 mm which had been sandwiched between two aluminium brazing sheet products.
  • Each aluminium brazing sheet product consisted of an AA3xxx-series core alloy clad on one side with an AA4045 alloy having a clad layer thickness of 12%.
  • the clad layers faced the Ti sheet which had been pre-treated by grinding and cleaning.
  • the metal laminate product had been clamped between two steel plates and bonded to each others by brazing under an argon atmosphere at 615°C for about 3 minutes. Following the brazing operation the laminate product had been cold rolled using a reduction of about 8% to further improve the bonding between the metal sheets.
  • the metal laminate product having a thickness of about 2 mm can be used as a crack stopper.
  • aluminium alloys of different composition can be used, such as Al-Mg-Sc alloys or AA7000-series alloys.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Laminated Bodies (AREA)
  • Pressure Welding/Diffusion-Bonding (AREA)
  • Metal Rolling (AREA)

Abstract

The invention relates to a crack stopper in the form of a metal laminate and to a method of manufacturing a crack stopper for application in a structural part of an aerospace vehicle, the method comprising the steps of (a) providing one or more aluminium alloy sheets, (b) providing an titanium or titanium alloy sheet, (c) bonding the aluminium sheet and the titanium sheet to form a metal laminate and wherein the method of bonding the metal laminate is selected from the group of brazing, rolling, cold rolling, or a combination thereof. The invention further relates to the use of such crack stopper materials in a structural part of an aerospace vehicle.

Description

Crack stopper and method of manufacturing a crack stopper
FIELD OF THE INVENTION The invention relates to metallic crack stopper materials for application in a structural part of an aerospace vehicle and to a method of manufacturing such crack stopper materials. The invention further relates to the use such crack stopper materials in amongst others a structural part of an aerospace vehicle.
BACKGROUND TO THE INVENTION
As will be appreciated herein below, except as otherwise indicated, aluminium 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 in 2006. For any description of alloy compositions or preferred alloy compositions, all references to percentages are by weight percent unless otherwise indicated.
The design of commercial aircraft requires different sets of properties for different types of structures on the airplane. In many parts, resistance to crack propagation either in the form of fracture toughness or fatigue crack growth is essential. Therefore, many significant benefits can be realised by improving fracture toughness and resistance to fatigue crack propagation of the aluminium used in structural parts of an aerospace vehicle. However, when constructing an airplane it is common that for certain critical areas of the load-bearing structure these are locally reinforced by applying a crack stopper, sometimes also known as a tear strap, for the purpose to stop or reduce the growth of any fatigue crack present. This local reinforcement is an extra sheet or thin plate with the purpose to increase the local cross section in order to reduce locally the nominal stress level. For example in some fuselages of commercial aircraft this is done by patches made from commercial available Ti-6-4 sheet.
The cracker stopper can be fastened to the structure by all means known in the art, such as for example by means of screws, rivets, adhesion, or welding, or combinations thereof.
A crack stopper as used here is a more general expression for what is also known in the art as "doubler" or "strap".
However; there is a need for crack stopper materials combining high stiffness with low specific density. DESCRIPTION OF THE INVENTION
It is an object of the invention to provide a method of manufacturing crack stopper materials for application in a structural part of an aerospace vehicle. It is another object of the invention to provide for a new use of the crack stopper materials manufactured with the present method.
These and other objects and further advantages are met or exceeded by the present invention concerning a method of manufacturing a crack stopper in the form of a metal laminate for application in a structural part of an aerospace vehicle, the method comprising the steps of
(a) providing one or more aluminium alloy sheets or strips;
(b) providing an titanium or titanium alloy sheet or strips;
(c) bonding the aluminium sheet and the titanium sheet to form a metal laminate and wherein the method of bonding is selected from the group of brazing, rolling, cold rolling, or a combination thereof.
The method according to this invention results in a wholly metallic laminate product wherein the titanium or titanium alloy sheet is firmly bonded to an aluminium alloy sheet. The metal laminate is for use as crack stopper and ideally is used for application in an aerospace vehicle. The combined use of titanium and aluminium provides for a metal laminate having a high strength and stiffness due to the high modulus of elasticity of the titanium while having a lower specific density compared to a fully titanium product of similar gauge as the metallic laminate. In this way considerable weight is saved while the metallic laminate is still offering sufficient crack stopper capability.
According to the method the titanium can be bonded to the aluminium alloy sheet by means of a rolling operation. The rolling is preferably carried out at a temperature of 1500C or less as higher rolling temperatures adversely affect the surface quality of the titanium sheet. Ideally the rolling operation is carried out as a cold rolling operation, which means at a temperature of less than 500C and preferably at ambient temperature. The aluminium sheet and titanium sheets are pre-treated prior to roll bonding using techniques regular in the art, and which would involve degreasing, cleaning, and where necessary also grinding. In accordance with the invention it has been found that titanium can be bonded to the aluminium sheet by means of brazing. Brazing, by definition, employs a filler metal, also referred to as a brazing alloy, having a liquidus above 45O0C and below the solidus of the base metal. In an embodiment of the method the titanium or titanium alloy sheet on one or both sides is bonded to the aluminium alloy sheet by means of an intermediate layer interposed between said titanium or titanium alloy sheet and said aluminium alloy sheet to form an intermediate sandwich product bonded by means of brazing to form the metal laminate, and wherein said intermediate layer is an aluminium brazing alloy. It is possible to bond the titanium or titanium alloy sheet directly to the aluminium alloy sheet in a brazing operation. In an alternative mode the titanium or titanium sheet is bonded to the aluminium alloy layer via the intermediate layer of aluminium brazing alloy forming an intermediate sandwich product, and then in a subsequent rolling operation a first metallic bond is established between the various metal layers in the intermediate sandwich product, where after the sandwich product is subjected to a brazing operation to form the crack stopper in the form of the metal laminate. In this way a strong bond is being obtained between the metal layers.
The aluminium brazing alloy is preferably an AISi brazing alloy, e.g. an AA4xxx-series aluminium alloy, comprising about 5 to 18% Si, and preferably about 6 to 14%. The amount of Fe depends primarily on the origin of the alloy material and can be up to about 0.8%, and preferably is not more than about 0.6%. As grain refiner element Ti can be present in a range of up to about 0.2%, preferably up to about 0.15%. The balance is made by unavoidable impurities and aluminium.
In an embodiment the AISi brazing material further comprises Mg in a range of about 0.02 to 4%, and preferably about 0.02 to 1.5%. The addition of Mg is to further enhance the brazeability in a vacuum brazing operation or in a controlled atmosphere brazing operation in the absence of a flux.
In a further embodiment the AISi brazing alloy further contains a wetting element, preferably one or more wetting elements selected from the group comprising Bi, Pb, Li, Sb, and Th, and wherein the total amount of the wetting elements is in a range of about 0.01 to 0.5%. In a preferred embodiment the element Bi is selected from the group of wetting elements and is in a range of about 0.01 to 0.5%, and preferably in a range of about 0.01 to 0.1%, as being the most efficient wetting element for this purpose in this alloy system during a brazing operation.
In the method according to this invention an AISi based brazing material is preferred. However, other aluminium brazing alloys can be used on a less preferred basis, such as AICuSn and AIAgCu fillers. It has been found, however, that these fillers can form undesirable fracture at the interface of the brazing material and the titanium base metals.
In a further embodiment the aluminium brazing alloy is interposed between the aluminium alloy sheet and the titanium or titanium alloy sheet in the form of a brazing sheet product. Such a brazing sheet product comprises of a core, typically of an aluminium alloy on one or both sides bonded to the aluminium brazing alloy. The aluminium brazing alloy may be bonded to the core alloy in various ways, for example by means of roll bonding, cladding spray-forming, or semi-continuous or continuous casting processes.
The brazing operation in the method of this invention is preferably carried out in a vacuum brazing operation or in a controlled atmosphere brazing operation devoid of the use of a brazing flux material. Controlled atmosphere brazing is typically carried out in a dry environment, and preferably using an argon or helium atmosphere. Typical brazing temperatures for the method according to this invention are in the range of about 5400C to
6200C. During the brazing operation it is preferred that the metal sheets are being kept flat by using appropriate means, for example by applying a pressure force or by clamping the laminate product between for example two thin plates.
Following the brazing operation the bonding of the metal laminate can be further improved by means of a deformation operation, typically carried out as a rolling operation whereby the total rolling reduction should be less than about 30%, preferably less than about 20%. After the brazing operation or after any rolling operation the metal laminate can be stretched, for example up to about 2%, in order to improve on the flatness of the metal laminate.
Following the brazing operation and a possible subsequent rolling operation and/or a stretching operation it is possible to subject the metallic laminate to an artificial ageing treatment to optimise the engineering properties of the aluminium alloy used. The aluminium alloy sheet bonded to the titanium or titanium alloy sheet is preferably one selected from the group consisting of AA2xxx, AA3xxx, AAδxxx, AAδxxx, and AA7xxx- series alloys. The AA5xxx-series alloys would include Al-Mg-Sc alloys. Also Al-Li or AICuLi- based alloys can be used for manufacturing the crack stopper according to this invention.
If more than one aluminium sheet is used in the crack stopper according to this invention, then it is also possible to use different aluminium alloys and which may also be of different thickness.
The titanium alloy used for the bonding to the aluminium alloy sheet can be any titanium alloy qualified for use in an aerospace structure and having the required strength and stiffness and other engineering properties for the specific application. On a more preferred basis the titanium sheet has a composition, in wt.%: Al 5.0 to 6.75, preferably 5.5 to 6.75
V 3.0 to 5.0, preferably 3.5 to 4.5
C 0.1 max., preferably 0.08 max.
H 0.015 max. Fe 0.5 max., preferably 0.3 max.
N 0.05 max. O 0.2 max., unavoidable impurities and balance Ti.
This compositional range would include TiAI6V4 or Ti-6-4 grade products providing the desired strength and stiffness and are qualified for various load-bearing constructions of aerospace applications.
In another embodiment of the invention the titanium alloy used for the bonding to the aluminium alloy sheet is a non-alloyed titanium sheet, in particular those having a chemical composition within the ranges, in wt.%:-
Fe 0.35 max., preferably 0.15 max., O 0.35 max., preferably 0.12 max.,
N 0.05 max.,
C 0.06 max.,
H 0.015% max., preferably 0.013% max., impurities each 0.1% max., total 0.4% max., balance titanium.
The metal laminate according to the invention can be built up by two or more metal layers, for example titanium or titanium alloy sheet bonded on one side only to an aluminium alloy sheet or a titanium plate bonded on both sides to an aluminium alloy sheet or even a multi-layered product of for example an arrangement of aluminium-titanium-aluminium- titanium layers. The use of more than one layer is favoured as it forms more barriers to be taken by a continuing crack propagation and thereby an enhanced functioning as crack stopper. In order to maintain sufficient stiffness in the crack stopper it is desired that the total thickness of all titanium sheets is at least about 50% of the total thickness of the metal laminate. On a more preferred basis it is at least 60% of the total metal laminate thickness.
For the application as crack stopper the metal laminate manufactured according to this invention has preferably a gauge in a range of about 0.4 to 15 mm. A more preferred upper limit is about 12 mm, and a preferred lower limit is about 1 mm. The width of the crack stopper is chosen on its functional requirements, and would typically go up to about 20 cm. In a further aspect of the invention it relates to a wing section and to a fuselage section of an aerospace vehicle reinforced locally with at least one crack stopper made from the Al-Ti laminate manufactured by the method according to this invention. The crack stopper can be in the form of a doubler sheet or thin plate or a strap.
In a further aspect of the invention it relates to the use or to a method of use of a metal laminate of an titanium sheet bonded to at least one aluminium sheet as a crack stopper in a structural part of an aerospace vehicle, such as a fuselage section or a wing section. The method of bonding the metal laminate is selected from the group comprising of brazing, rolling, cold rolling, or any combination thereof.
Although the crack stopper according to this invention is rendered ideally suitable for application in aerospace vehicles, such as commercial and military aircraft, it can be used for a similar purpose in a vessel, a pressure vessel, a road tanker, a storage silo, or in pipes.
The invention will now be illustrated with reference to non-limiting embodiments according to the invention.
Example 1. A metal laminate product had been produced from an about 0.4 mm brazing sheet product consisting of an AA3xxx-series core alloy clad on both sides with an AA4104 brazing alloy (each cladding having a thickness of 8% of the brazing sheet thickness) and wherein said brazing sheet has been sandwiched between commercial available Ti-grade 5 sheets of 0.55 mm thickness. All sheets had dimensions of 100 by 300 mm. The Ti sheets have been pre-treated by grinding and cleaning. The whole metal laminate product had been clamped between two steel plates and vacuum brazed at 595°C for about 3 minutes. The resultant product is a metal laminate product consisting of two Ti sheets firmly bonded to each other via aluminium alloys formed by the brazing sheet product. The metal laminate product having a thickness of about 1.5 mm can be used as a crack stopper.
Example 2.
A metal laminate product had been product from a commercial available TiAI6V4 sheet of 1.5 mm which had been sandwiched between two aluminium brazing sheet products. Each aluminium brazing sheet product consisted of an AA3xxx-series core alloy clad on one side with an AA4045 alloy having a clad layer thickness of 12%. The clad layers faced the Ti sheet which had been pre-treated by grinding and cleaning. The metal laminate product had been clamped between two steel plates and bonded to each others by brazing under an argon atmosphere at 615°C for about 3 minutes. Following the brazing operation the laminate product had been cold rolled using a reduction of about 8% to further improve the bonding between the metal sheets. The metal laminate product having a thickness of about 2 mm can be used as a crack stopper.
It will be immediately apparent to the skilled person that instead of an AA3000-series core alloy also aluminium alloys of different composition can be used, such as Al-Mg-Sc alloys or AA7000-series alloys.

Claims

1. Method of manufacturing a crack stopper in the form of a metal laminate for application in a structural part of an aerospace vehicle, the method comprising the steps of (a) providing one or more aluminium alloy sheets;
(b) providing an titanium or titanium alloy sheet;
(c) bonding the aluminium sheet and the titanium sheet to form a metal laminate and wherein the method of bonding the metal laminate is selected from the group of brazing, rolling, cold rolling, or a combination thereof.
2. Method according to claim 1 , wherein the titanium alloy sheet on one or both sides is bonded to the aluminium alloy sheet by means of an intermediate layer interposed between said titanium alloy sheet and said aluminium alloy sheet to form an intermediate sandwich product bonded by means of brazing to form the metal laminate, and wherein said intermediate layer is an aluminium brazing alloy.
3. Method according to claim 2, wherein the aluminium brazing alloy is an AISi alloy comprising 5 to 18% Si, and preferably further having 0.02 to 4% Mg.
4. Method according to any one of claims 1 to 3, wherein brazing is carried out in a vacuum brazing operation or in a controlled atmosphere brazing operation devoid of the use of a brazing flux material.
5. Method according to any one of claims 1 to 4, wherein the aluminium alloy sheet is selected from the group consisting of AA2xxx, AA5xxx, AA6xxx, and AA7xxx-series alloy.
6. Method according to any one of claims 1 to 5, wherein the method of bonding the metal laminate consists of a combination of brazing and rolling.
7. Method according to any one of claims 1 to 6, wherein the metal laminate has a thickness wherein 50% or more, and preferably 60% or more, of the thickness is formed by the titanium alloy sheet(s).
8. Method according to any one of claims 1 to 7, wherein the titanium sheet has a composition, in wt.%: Al 5.5 to 6.75
V 3.5 to 4.5
C 0.08 max.
H 0.015 max.
Fe 0.3 max.
N 0.05 max.
O 0.2 max. unavoidable impurities and balance Ti.
9. Method according to any one of claims 1 to 7, wherein the titanium sheet has a composition, in wt.%:
Fe 0.35 max., preferably 0.15 max.,
O 0.35 max., preferably 0.12 max.,
N 0.05 max., C 0.06 max.,
H 0.015% max., preferably 0.013% max., impurities each 0.1% max., total 0.4% max., balance titanium.
10. Method according to any one of claims 1 to 9, wherein the metal laminate has a gauge in a range of 0.4 to 15 mm.
11. Use a metal laminate of an titanium sheet bonded to an aluminium sheet as a crack stopper in a structural part of an aerospace vehicle.
12. Use according to claim 11 , wherein the method of bonding laminate is selected from the group comprising of brazing, rolling, cold rolling, or combination thereof.
PCT/EP2008/005365 2007-07-02 2008-07-01 Crack stopper and method of manufacturing a crack stopper WO2009003679A1 (en)

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DE112008001659.3T DE112008001659B4 (en) 2007-07-02 2008-07-01 A method of making a tearstopper and using a metal laminate

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EP07012886.3 2007-07-02
EP07012886 2007-07-02
EP07025154 2007-12-27
EP07025154.1 2007-12-27

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CN102284833A (en) * 2011-05-23 2011-12-21 宋洪海 Production method of titanium-aluminium composite plates
ITRM20120168A1 (en) * 2012-04-19 2013-10-20 Ct Sviluppo Materiali Spa PROCEDURE FOR THE PRODUCTION OF A COMPOSITE MULTI-LAYER WITH A REINFORCED AND MULTI-LAYING COMPOSITE METALLIC MATRIX.

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DE112008001659T5 (en) 2010-05-12

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