Classifications

• • 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
  • C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon
• • 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
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/24—Selection of soldering or welding materials proper
  • B23K35/28—Selection of soldering or welding materials proper with the principal constituent melting at less than 950 degrees C
  • B23K35/286—Al as the principal 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
• • 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
  • C22C21/12—Alloys based on aluminium with copper as the next major constituent
  • C22C21/14—Alloys based on aluminium with copper as the next major constituent with silicon
• • 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
  • C22C21/12—Alloys based on aluminium with copper as the next major constituent
  • C22C21/16—Alloys based on aluminium with copper as the next major constituent with magnesium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/05—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys of the Al-Si-Mg type, i.e. containing silicon and magnesium in approximately equal proportions
• • 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

Definitions

• This invention pertains to aluminium aerospace alloys. More particularly, this invention pertains to aluminium alloys of the AA ⁇ xxx-series (or AA6000-series) that are suitable for welding, yet have improved performance properties, particularly corrosion resistance and damage tolerance properties.
• alloy designations and temper designations refer to the Aluminium Association designations in Aluminum Standards and Data and the Registration Records, as published by the Aluminum Association.
• Aluminium alloys 6061 and 6063 are well known heat treatable aluminium alloys. These alloys have useful strength and toughness properties in both T4 and T6 tempers. As is known, the T4 condition refers to a solution heat treated and quenched condition naturally aged to a substantially stable property level, whereas T6 tempers refer to a stronger condition produced by artificially ageing. These known alloys lack, however, sufficient strength for most structural aerospace applications. Several other Aluminium Association (“AA”) 6000 series alloys are generally unsuitable for the design of commercial aircraft which require different sets of properties for different types of structures.
• AA Aluminium Association
• the AA6013 alloy has attractive mechanical properties for use amongst others as a fuselage skin and furthermore this alloy is also weldable. However, there are at least two factors limiting the application of this AA6013 alloy. The first one is that the AA6013 alloy is susceptible to intergranular corrosion (IGC) attack, which can increase local stress concentrations when an alloy product is subjected to stress conditions such as repeated pressurization and depressurization of an aircraft fuselage in use, see for example the paper of T.D. Burleigh, "Microscopic Investigation of the Intergranular Corrosion of 6013-T&',
• AA6056-series alloy suitable for aerospace application.
• the registered compositional ranges for AA6056 are, in weight percent: Si 0.7 - 1.3
• Another method of controlling the resistance to intergranular corrosion of the AA6056 alloy is by providing it with a dilute AA7072 cladding having 0.25-0.7 wt.% Zn as disclosed in EP-1170118.
• a principal objective of the present invention is to provide an improved AA ⁇ xxx series alloy that is weldable, yet exhibits improved corrosion resistance properties.
• An object of the present invention is to provide a weldable AA6xxx-type series alloy product having improved resistance to intergranular corrosion compared to its AA6013 counterpart.
• a further object is to provide a weldable AA6xxx-type series alloy product having improved damage tolerance properties compared to its AA6013 counterpart.
• Another object is to provide a weldable AA6xxx-type series alloy product having an improved balance of intergranular corrosion resistance and damage tolerance properties compared to its AA6013 counterpart.
• the aluminium alloy of this invention offers greater resistance to intergranular corrosion resistance compared to its AA6013 aluminium alloy counterpart. Furthermore, in the peak aged condition, the aluminium alloy of this invention offers an improved ratio of UPE versus tensile strength.
• an AA6013 counterpart it is meant an aluminium alloy wrought product having a composition as defined above for AA6013 and processed and heat treated and having the same dimensions of length, width and thickness as the wrought product of the present invention to which it is compared.
• Fig. 1 shows schematically the UPE (vertical axis) against the yield strength (horizontal axis) of the five alloys tested.
• Fig. 2 shows schematically the maximum IGC depth of the five alloys tested.
• the present invention provides a weldable aluminium alloy wrought product having high strength and improved resistance to intergranular corrosion, the alloy consisting essentially of, in weight percent:
• Si about 0.2 to 1.3, preferably about 0.6 to 1.15, and more preferably about
• Mg about 0.4 to 1.5, preferably about 0.7 to 1.25, and more preferably about 0.7 to 1.05
• Cu about 0.1 to 1.1 , preferably about 0.5 to 1.1 , and more preferably about
• 0. 2 to 0.6 Fe about 0.02 to 0.3, preferably about 0.02 to 0.2, and more preferably about 0.02 to 0.15 Zn up to about 0.9 Cr up to about 0.25
• an important alloying element in the alloy according to this invention is titanium.
• the addition of Ti at levels of more than 0.06% to the alloy according to this invention has the effect of increasing the corrosion resistance, and the resistance against intergranular corrosion in particular.
• Ti levels at significant lower levels e.g. at about 0.03% or less
• the Ti content is in the range of about 0.06 to 0.19%, and preferably about 0.09 to 0.19%.
• the Cr content should be in the range of up to about 0.25%, and preferably about 0.05 to 0.25%, more preferably about 0.08 to 0.19%.
• the combined addition of Ti plus Cr should be in the range of about 0.12 to 0.3%, and preferably about 0.15 to 0.28%.
• Ti and Cr has also a very favourable effect of the strength levels and the Unit Propagation Energy ("UPE") making the alloy product a very attractive candidate for aerospace applications.
• UPE Unit Propagation Energy
• the ranges for the Ti and Cr contents are very critical. For example it has been found that the addition of more than 0.2% Ti may result in the formation of large primary phases which significantly reduce amongst others the tear strength (“TS”) and the UPE.
• Zr may be added to the aluminium alloy according to this invention up to 0.2%. If purposively added to the alloy it is preferably in the range of about 0.06 to 0.18%. Adding Zr to the alloy has the effect of maintaining favourable UPE levels while offering an increased yield strength.
• the intergranular corrosion resistance is slightly decreased compared to the alloy variant with solely the combined addition of Ti plus Cr. However, the overall balance of strength, damage tolerance and corrosion resistance is still favourable compared to its AA6013 counterpart.
• the Zr content is less than 0.05%, and more preferably the aluminium alloy is substantially free from Zr to obtain a fully recrystallised microstructure.
• the aluminium alloy according to this invention there is no purposive addition of Zn, but it may be tolerated as an impurity.
• the Zn content is in a range of less than about 0.25%, preferably less than about 0.05%, and more preferably less than about 0.02%.
• the aluminium alloy according to this invention there is a purposive addition of Zn to further improve the strength, wherein the Zn is preferably present in a range of about 0.5 to 0.9%, and preferably in a range of about 0.6 to 0.85%.
• a too high Zn content may have an adverse effect on the intergranular corrosion performance.
• the aluminium alloy according to the invention is substantially free from each of V, Sr, and Be.
• the alloy rolled products have a recrystallised microstructure, meaning that 80% or more, and preferably 90% or more of the grains in a T4 or artificially aged condition are recrystallised.
• Increased intergranular corrosion resistance is particularly useful for applications that expose the metal to corrosive environments, such as the lower portion of an aircraft fuselage. Moisture and corrosive chemical species tend to accumulate in these areas of an aircraft as solutions drain to the bottom of the fuselage compartment.
• the alloy product according to this invention has in a T6 temper an intergranular corrosion depth of attack of less than 100 micron when measured according to the MIL-H-6088 test, and preferably less than 90 micron, and in the best examples less than 50 micron.
• the aluminium alloy wrought product according to this invention is preferably provided as a rolled product such as a sheet or plate.
• a rolled product such as a sheet or plate.
• the alloy composition of this invention works well at resisting intergranular corrosion in both its clad and unclad varieties.
• the alloy layer applied overtop the invention is a AA7xxx-series alloy cladding, more preferably an AA7072 series alloy or the AlZn-cladding as disclosed in EP-1170118 (incorporated herein by reference), or the more commonly known cladding of the AAIxxx-series, such as the AA1145 aluminium.
• the alloy product according to the invention is being provided with a cladding thereon on one side of the AA1000-series and on the other side thereon of the AA4000-series.
• corrosion protection and welding capability are being combined.
• the product may be used successfully for example for pre- curved panels.
• the rolling practice of an asymmetric sandwich product 1000-series alloy + core + 4000-series alloy
• the rolling practice of an asymmetric sandwich product causes some problems such as banaring
• Aerospace applications of this invention may combine numerous alloy product forms, including, but not limited to, TIG welding, laser and/or mechanically welding (i.e. friction stir welding): sheet to a sheet or plate base product; plate to a sheet or plate base product; or one or more extrusions to such sheet or plate base products.
• TIG welding laser and/or mechanically welding
• sheet to a sheet or plate base product plate to a sheet or plate base product
• plate to a sheet or plate base product or one or more extrusions to such sheet or plate base products.
• extrusions to such sheet or plate base products.
• One particular embodiment envisions replacing the manufacture of today's airplane fuselage parts from large sections of material from which significant portions are machined away.
• panels can be machined or chemically milled to remove metal and reduce thickness at selective strip areas to leave upstanding ribs between the machined or chemically milled areas. These upstanding ribs provide good sites for welding stringers thereto for reinforcement purposes.
• Such stringers can be made of the same
• a method of manufacturing the alloy product according to this invention comprising the steps of: a. casting an ingot having a chemical composition of, in wt.%: Si about 0.2 to 1.15 Mg about 0.4 to 1.5 Cu about 0.1 to 1.3 Mn up to 0.7
• Ti up to about 0.19, and preferably about 0.06 to 0.19
• the alloy product is ideally provided in a T4 temper by allowing the product to naturally age to produce an improved alloy product having good formability, or in a T6 temper by artificial ageing.
• an ageing cycle comprising exposure to a temperature of between
• the aluminium alloy as described herein can be provided in process step (a) as an ingot or slab for fabrication into a suitable wrought product by casting techniques currently employed in the art for cast products, e.g. DC-casting, EMC-casting, EMS-casting. Slabs resulting from continuous casting, e.g. belt casters or roll caster, may be used also.
• the rolling faces of both the clad and the non-clad products are scalped in order to remove segregation zones near the cast surface of the ingot.
• the cast ingot or slab may be homogenised prior to hot working, preferably by means of rolling and/or it may be preheated followed directly by hot working.
• the homogenisation and/or preheating of the alloy prior to hot working should be carried out at a temperature in the range of 490 to 58O 0 C in single or in multiple steps. In either case, the segregation of alloying elements in the material as-cast is reduced and soluble elements are dissolved. If the treatment is carried out below 49O 0 C, the resultant homogenisation effect is inadequate.
• the temperature is above 580 0 C, eutectic melting might occur resulting in undesirable pore formation.
• the preferred time of the above heat treatment is between 2 and 30 hours. Longer times are not normally detrimental.
• Homogenisation is usually performed at a temperature above 540 0 C.
• a typical preheat temperature is in the range of 540 to 570 0 C with a soaking time in a range of 4 to 16 hours.
• the alloy product is cold worked, preferably after being cold rolled, or if the product is not cold worked then after hot working, the alloy product is solution heat treated at a temperature in the range of 480 to 590 0 C, preferably 530 to 57O 0 C, for a time sufficient for solution effects to approach equilibrium, with typical soaking times in the rang of 10 sec. to 120 minutes.
• care should be taken against too long soaking times to prevent diffusion of alloying element from the core into the cladding detrimentally affecting the corrosion protection afforded by the cladding.
• the alloy product be cooled to a temperature of 175°C or lower, preferably to room temperature, to prevent or minimise the uncontrolled precipitation of secondary phases, e.g. Mg 2 Si.
• cooling rates should not be too high in order to allow for a sufficient flatness and low level of residual stresses in the alloy product. Suitable cooling rates can be achieved with the use of water, e.g. water immersion or water jets. While the invention is particularly suited to fuselage skins, it also may find other applications such as automotive sheet, railroad car sheet, and other uses.
• Table 1 The chemical compositions of the ingot cast alloys. All percentages are by weight, balance aluminium and unavoidable impurities.
• the tensile testing has been carried out on the bare sheet material in the T6-temper and having a fully recystallised microstructure.
• small euro-norm specimens were used, average results of 3 specimens are given, and "Rp” stands for yield strength, "Rm” for ultimate tensile strength, and El for elongation (A50).
• the results of the tensile tests have been listed in Table 2.
• the UPE versus the yield strength is also schematically shown in Fig. 1.
• the "TS" stands for tear strength, and has been measured in the L-T direction in accordance with ASTM-B871-96.
• UPE Unit Propagation Energy
• ASTM-B871-96 is a measure for toughness, in particular for the crack growth
• TS is in particular a measure for crack initiation.
• ICG lntergranular corrosion resistance

Priority Applications (1)

Applications Claiming Priority (3)

Publications (1)

Family

ID=36691353

Family Applications (1)

Country Status (5)

Families Citing this family (37)

Family Cites Families (10)

• 2007
  • 2007-06-08 FR FR0755594A patent/FR2902442B1/fr not_active Expired - Fee Related
  • 2007-06-13 US US11/762,546 patent/US20080145266A1/en not_active Abandoned
  • 2007-06-14 WO PCT/EP2007/005280 patent/WO2007144186A1/en active Application Filing
  • 2007-06-14 CN CN2007800256035A patent/CN101484598B/zh not_active Expired - Fee Related
  • 2007-06-14 EP EP07726035A patent/EP2032729A1/de not_active Ceased

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events