Structural member for aeronautical construction with a variation of usage properties

Abstract

This invention relates to a process for manufacturing an aluminium alloy part with structural hardening as well as to structural members including monolithic structural members and to products prepared from such structural members. A suitable process of the present invention involves annealing in a linear furnace with a controlled temperature profile comprising at least two zones or groups of zones Z 1 , Z 2 . The length parallel to the axis of the linear furnace of each of the at least two zones or groups of zones Z 1 and Z 2 is generally at least about one meter.

1 . A process for manufacturing an aluminium alloy part with structural hardening, comprising: 
 solution heat treating a semi-finished rolled, extruded or forged product, followed by quenching,    optionally controlling tension with permanent elongation of at least 0.5%, and annealing,    wherein at least a portion of the annealing is conducted in a furnace with a controlled temperature profile comprising at least two zones or groups of zones Z 1 , Z 2  with initial temperatures T 1 and T   2  and having a temperature variation around the set temperature for each of the temperatures T 1 and T   2  that does not exceed about ±5° C. within the length of the zones or groups of zones, and wherein the difference between the set values of the initial temperatures T 1 and T   2  is greater than or equal to about 5° C., and the zones or groups of zones are optionally separated by a zone or a group of zones Z 1,2 , within which the initial temperature varies from T 1 to T   2 ,    and wherein the length parallel to the axis of the furnace of each of the at least two zones or groups of zones Z 1  and Z 2  is at least one meter.    
   
   
       2 . A process according to  claim 1 , wherein the temperature variation around the set temperature for each of the temperatures T 1  and T 2  does not exceed about ±4° C. within the length of the at least two zones or groups of zones Z 1  and Z 2 .  
   
   
       3 . A process according to  claim 1 , wherein the difference between the set temperatures T 1  and T 2  is from about 10° C. to about 80° C.  
   
   
       4 . A process according to  claim 1 , wherein the temperature in at least one of the zones or groups of zones Z 1  or Z 2  varies as a function of time according to at least two temperature plateaus, and/or according to a temperature ramp with no clearly defined plateau.  
   
   
       5 . A process according to  claim 1 , wherein the annealing in a linear furnace with controlled temperature gradient is followed by at least one forming or machining operation and annealing in a homogeneous furnace.  
   
   
       6 . A process according to  claim 1 , wherein the annealing in a linear furnace with a controlled temperature gradient is preceded by annealing in a homogeneous furnace.  
   
   
       7 . A process according to  claim 1 , wherein the length of the part is at least 7 meters.  
   
   
       8 . A process according to  claim 1 , wherein the aluminium alloy part with structural hardening is monolithic.  
   
   
       9 . A process according to  claim 1 , wherein the aluminium alloy part with structural hardening is assembled starting from at least two aluminium alloy parts with structural hardening.  
   
   
       10 . A process according to  claim 9 , wherein assembly of said at least two parts are made by riveting, bonding, laser beam welding, friction stir welding and/or electron beam welding.  
   
   
       11 . A process according to  claim 1 , wherein the annealing comprises a first homogeneous treatment at a temperature between 115° C. and 125° C. for a duration of from about 2 to about 12 hours, a second treatment during which one end of said part is treated at a temperature from about 115° C. to about 125° C., while the other end of said part is treated at a temperature from about 150° C. to about 160° C., both for a duration of between 8 and 24 hours.  
   
   
       12 . A monolithic structural member comprising an aluminium alloy with structural hardening having a length L greater than a width B and thickness E, suitable for aeronautical construction,  
     said monolithic structural member comprising at least two segments P 1  and P 2  each located on a different length of said structural member, wherein at least one physical property (measured at mid-thickness) of P 1  and/or P 2  selected from the group consisting of: 
 a) P 1 : K IC(L-T) ≧38 MPa{square root}m and P 2 : R m (L)≧580 MPa  
 b) P 1 : K IC(L-T) ≧40 MPa{square root}m and P 2 : R m (L)≧580 MPa  
 c) P 1 : K IC(L-T) ≧41 MPa{square root}m and P 2 : R m (L)≧580 MPa  
 d) P 1 : K IC(L-T) ≧42 MPa{square root}m and P 2 : R m (L)≧590 MPa  
 e) P 1 : K IC(L-T) ≧39 MPa{square root}m and P 2 : R m (L)≧580 MPa and P 2 : R m (TL)≧550 MPa  
 f) P 1 : K IC(L-T) ≧39 MPa{square root}m and P 2 : R m (L)≧580 MPa and P 2 : R p0.2 (L)≧550 MPa  
 i) P 1 : K IC(L-T) ≧39 MPa{square root}m and P 1 : R m (L)≧530 MPa, and P 2 : Rm(L)≧580 MPa  
 j) P 1 : K IC(L-T) ≧40 MPa{square root}m and P 1 : R m (L)≧540 MPa, and P 2 : Rm(L)≧590 MPa  
 k) P 1 : K app(L-T)(CCT406) >125 MPa{square root}m et P2: R m (L)>590 MPa.  
 
   
   
       13 . A structural member according to  claim 12 , wherein A (L) ≧9% in segments P 1  and P 2 .  
   
   
       14 . A structural member according to  claim 13 , wherein A (L) ≧9% outside segments P 1  and P 2 .  
   
   
       15 . A structural member according to  claim 12 , wherein the length F P1  and F P2  (expressed as a percent of the length L) of said at least two segments P 1  and P 2  is such that F P1 ≧25% and F P2 >25%.  
   
   
       16 . A structural member according to  claim 15 , wherein F P1 ≧35% and F P2 ≧30%.  
   
   
       17 . A structural member according to  claim 16 , wherein F P1 ≧40% and F P2 ≧30%.  
   
   
       18 . A structural member according to  claim 12 , wherein the alloy comprises from about 7 to about 15% of zinc, from about 1 to about 3% of copper and/or from about 1.5 to about 3.5% of magnesium.  
   
   
       19 . A structural member according to  claim 18 , wherein zinc is from about 8 to about 13%.  
   
   
       20 . A structural member according to  claim 19 , wherein copper is from about 1.3 to about 2.1%.  
   
   
       21 . A structural member according to  claim 20 , wherein magnesium is from about 1.8 to about 2.7%.  
   
   
       22 . A structural member according to  claim 12 , wherein the length of the part is at least 7 meters.  
   
   
       23 . A method for making an aircraft wing panel, wing stringers, wing spars, fuselage stiffeners, fuselage panels and/or butt straps comprising using a structural member according to  claim 12 .  
   
   
       24 . An aircraft comprising at least one wing panel made from a structural member according to  claim 12 , wherein said segment P 1  is located close to the fuselage, and said segment P 2  is close to the geometric tip of the wing.  
   
   
       25 . A method for forming a hardened aluminium alloy part comprising treating said part in a furnace having at least two zones, each at least one meter in length at a temperature that is maintained approximately constant in said at least two zones.  
   
   
       26 . A monolithic structural member prepared from a process of  claim 25 .  
   
   
       27 . An aircraft comprising a structural member of  claim 26 .  
   
   
       28 . A semi-product in which (measured at mid-thickness) comprising an aluminium alloy with structural hardening having a length L greater than a width B and thickness E, suitable for aeronautical construction, said semi-product comprising at least two segments P 1  and P 2  each located on a different length of said semi-product, wherein at least one physical property (measured at mid-thickness) of P 1  and/or P 2  selected from the group consisting of: 
 a) R p0.2 , determined in the L direction or in the LT direction, has a difference  p0.2(P2) -R p0.2(P1)  of at least 50 MPa and preferably of at least >75 MPa, and/or    b) R p0.2 , determined in the ST direction, has a difference R p0.2(P2) -R p0.2(P1)  of at least 30 MPa and preferably at least 50 MPa, and/or    c) K IC , measured in the L-T direction, has a difference K IC(P1) -K IC(P2)  of at least 5 MPa{square root}m and preferably of at least 7 MPa{square root}m, and/or    d) K app , measured in the L-T direction, has a difference K app(P1) -K app(P2)  of at least 10 MPa{square root}m and preferably of at least 15 MPa{square root}m.    
   
   
       29 . A single monolithic structural member that is at least bi-functional.  
   
   
       30 . A structural member of  claim 29  comprising an alloy selected from the group consisting of 7449, 7349 and 7056.  
   
   
       31 . A semi-product of  claim 28 , wherein said alloy is selected from the group consisting of 7449, 7349 and 7056.  
   
   
       32 . A structural member of  claim 29  that does not have a continuous variation of properties along its entire length, and said structural member comprises at least two segments in which at least some physical properties thereof are constant over a predetermined length of the segment.  
   
   
       33 . A member of  claim 32 , wherein said predetermined length is at least one meter.  
   
   
       34 . A member of  claim 32 , wherein said predetermined length is at least two meters.  
   
   
       35 . A method of  claim 25  wherein the product produced thereby does not have a continuous variation of properties along its entire length, and said product produced comprises at least two segments in which at least some physical properties thereof are constant over a predetermined length of the segment.  
   
   
       36 . A method of  claim 35 , wherein said predetermined length is at least one meter.  
   
   
       37 . A method of  claim 35 , wherein said predetermined length is at least two meters.  
   
   
       38 . A structural member of  claim 26  that does not have a continuous variation of properties along its entire length, and said structural member comprises at least two segments in which at least some physical properties thereof are constant over a predetermined length of the segment.  
   
   
       39 . A member of  claim 38 , wherein said predetermined length is at least one meter.  
   
   
       40 . A member of  claim 38 , wherein said predetermined length is at least two meters.  
   
   
       41 . An aircraft comprising a structural member of  claim 38 .  
   
   
       42 . An aircraft comprising a structural member of  claim 39 .  
   
   
       43 . An aircraft comprising a structural member of  claim 40 .  
   
   
       44 . A process of  claim 1 , wherein said aluminum alloy is selected from the group consisting of 2xxx, 4xxx, 6xxx, 7xxx and 8xxx alloys.  
   
   
       45 . A structural member of  claim 12  wherein said aluminum alloy is selected from the group consisting of 2xxx, 4xxx, 6xxx, 7xxx and 8xxx alloys.  
   
   
       46 . A method of  claim 25  wherein said aluminum alloy part comprises 2xxx, 4xxx, 6xxx, 7xxx and/or 8xxx alloys.  
   
   
       47 . A monolithic structural member prepared using a method of  claim 46 .  
   
   
       48 . An aircraft comprising a monolithic structural member of  claim 47.