EP1644546B1 - Use of pipes made from al/zn/mg/cu alloys with improved compromise between static mechanical properties and tolerance to damage - Google Patents

Description

Technical field of the invention

The present invention relates to alloys of Al-Zn-Mg-Cu type with compromised static mechanical characteristics - improved damage tolerance, as well as structural elements for aeronautical construction incorporating wrought half-products made from these alloys.

State of the art

It is known that during the manufacture of semi-finished products and structural elements for aeronautical construction, the various desired properties can not be optimized all at the same time and independently of each other. When modifying the chemical composition of the alloy or the parameters of the product development processes, several critical properties can even show antagonistic tendencies. This is sometimes the case of the properties grouped under the term "static mechanical resistance" (in particular the tensile strength R _m and the yield strength R _p0.2 ) on the one hand, and the properties gathered under the term "tolerance". damage "(including toughness and resistance to crack propagation) on the other hand. Some common properties such as fatigue strength, corrosion resistance, formability and elongation to failure are complicated and often unpredictable to the properties (or "characteristics") mechanical. The optimization of all the properties of a material for aircraft construction therefore very often involves a compromise between several key parameters.

Al-Zn-Mg-Cu alloys (belonging to the family of 7xxx alloys) are commonly used in aircraft construction, and in particular in the construction of civil aircraft wings. For the extrados of the wings is used for example a skin made of alloy plates 7150, 7055, 7449, and possibly stiffeners profiles of alloys 7150, 7055 or 7449. The alloys 7150, 7050 and 7349 are also used for the manufacture of fuselage stiffeners. The 7475 alloy is sometimes used for the manufacture of lower wing panels, in particular by machining of heavy plates, whereas the spun wing stiffeners are usually made of alloys of 2xxx type (eg 2024, 2224, 2027).

Some of these alloys have been known for decades, such as alloys 7075 and 7175 (zinc content between 5.1 and 6.1% by weight), 7475 (zinc content between 5.2 and 6.2%) , 7050 (zinc content between 5.7 and 6.7%), 7150 (zinc content between 5.9 and 6.9%) and 7049 (zinc content between 7.2 and 8.2%). These alloys have different compromises between toughness and yield strength.

The patent application EP 0 257 167 A1 discloses an alloy developed specifically for the reverse spin fabrication of pressure-resistant hollow bodies. This alloy has the composition (in percent by mass): Zn 6.25 - 8.0 Mg 1,2 - 2,2 Cu 1,7 - 2,8 Zr≤ 0.05 Fe≤ 0.20 (Fe + Si) ≤ 0.40 Cr 0.15 - 0.28 Mn≤ 0.20 Ti≤ 0.05. These products do not exceed, in the solution and return state, values of R _m = 530 MPa, values of R _p0.2 = 480 MPa, and A = 15.4%. The increase in zinc (at 8.0%), Cu (at 2.2%) and Mg (at 2.4%) leads to an increase of R _m (up to 570 MPa) and R _p0.2 (up to 525 MPa), but these products have a poor behavior in burst.

The request for EP 0 589 807 Al discloses a pressurized gas cylinder with the composition Zn 6.9, Cu 2.3, Mg 1.9, Zr 0.11 which shows in the T73 state the following static mechanical characteristics in direction L: $${\mathrm{<figure-callout\; id="2"\; label="R\; p"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R\; </figure-callout>}}_{\mathrm{p}}=\mathrm{392}\mathrm{MPa},{\mathrm{R}}_{\mathrm{m}}=\mathrm{459}\mathrm{MPa},\mathrm{AT}=\mathrm{15},\mathrm{2}\%\mathrm{.}$$

• Zn 5,9 - 6,7 , Mg 1,6 - 1,86 , Cu 1,8 - 2,4 , Zr 0,08 - 0,15

pour la fabrication d'élément de structure pour avions. Ces éléments de structure sont optimisés pour montrer une forte résistance mécanique, ténacité et résistance à la fatigue.The patent US 5,865,911 (Aluminum Company of America) discloses an Al-Zn-Cu-Mg alloy of composition

• Zn 5.9 - 6.7, Mg 1.6 - 1.86, Cu 1.8 - 2.4, Zr 0.08 - 0.15

for the manufacture of structural element for aircraft. These structural elements are optimized to show high mechanical strength, toughness and fatigue resistance.

• et comportant chacun Mg 1,5 Zr 0,11 ,

ainsi que des procédés de traitement thermomécanique appropriés pour la fabrication d'éléments de structure pour avions.The patent application WO 02/052053 discloses three Al-Zn-Cu-Mg alloys of composition Zn 7.3 Cu 1.6, Zn 6.7 Cu 1.9, Zn 7.4 Cu 1.9

• and each having Mg 1.5 Zr 0.11,

as well as thermomechanical treatment processes suitable for the manufacture of aircraft structural elements.

Also known alloy 7040 whose standardized chemical composition is: Zn 5.7 - 6.7 Mg 1.7 - 2.4 Cu 1,5 - 2,3 Zr 0.05 - 0.12 If ≤ 0.10 Fe ≤ 0.13 Ti ≤ 0.06 Mn ≤ 0.04 other elements ≤ 0.05 each and ≤ 0.15 in total.

Alloy 7085 is also known whose standardized chemical composition is: Zn 7.0 - 8.0 Mg 1,2 - 1,8 Cu 1,3 - 2,0 Zr 0.08 - 0.15 If ≤ 0.06 Fe ≤ 0.08 Ti ≤ 0.06 Mn ≤ 0.04 Cr ≤ 0.04 other elements ≤ 0.05 each and ≤ 0.15 in total.

More recently, the Applicant has found the advantage of reducing the concentration of Cu and Mg relative to an alloy type 7050 (see EP 0 876 514 B1 ). For a strong plate, the compromise between toughness and mechanical strength is thus improved.

Problem

The problem to which the present invention attempts to respond is to propose a wrought product of Al-Zn-Mg-Cu type alloy which makes it possible to achieve very high levels of static mechanical resistance while presenting a level of sufficient in other properties of use, including toughness, corrosion resistance and fatigue crack propagation resistance (cracking) for use in the manufacture of structural parts or components that meet high requirements such as frames, forks and handlebars of cycles or baseball bats.

Objects of the invention

• Zn 6,7 - 7,5 % Cu 2,0 - 2,8 % Mg 1,6 - 2,2 %
• Zr 0,08 - 0,20 %
• Fe + Si < 0,20 %

autres éléments ≤ 0,05 % chacun et ≤ 0,15 % au total,
le reste aluminium
pour la fabrication de cadres, fourches et guidons de cycles ou de battes de baseball.The object of the present invention is constituted by the use of a spun product, in the form of an aluminum alloy tube, characterized in that it comprises (in mass%):

• Zn 6.7 - 7.5% Cu 2.0 - 2.8% Mg 1.6 - 2.2%
• Zr 0.08 - 0.20%
• Fe + Si <0.20%

other elements ≤ 0,05% each and ≤ 0,15% in total,
the rest aluminum
for the manufacture of frames, forks and handlebars of cycles or baseball bats.

Description of figures

• The figure 1 shows the section of "I" profiles whose manufacture is described in Example 1.
  • 1 = thick branch, 2 = Thick branch thickness 1, 3 = sole,
  • 4 = thickness of the sole 3, 5 = long branch, 6 = height, 7 = width.
• The figure 2 shows the section of profiles whose manufacture is described in Examples 3 and 5.
• The figure 3 shows the section of "inverted T" sections whose manufacture is described in example 4 (same symbols as figure 1 , 8 = reinforcement width).

Description of the invention a) Terminology

Unless stated otherwise, all the information relating to the chemical composition of the alloys is expressed in percent by weight. Therefore, in a mathematical expression, "0.4 Zn" means: 0.4 times the zinc content, expressed in mass percent; this applies mutatis mutandis to other chemical elements. Unless otherwise indicated, all the chemical compositions indicated in the present description and the examples were determined on samples obtained by taking a representative sample of liquid metal during the casting, followed by the solidification of the liquid metal taken in a form. which ensures a good homogeneity of the concentration of the elements in the solid. Determination of the concentration of the chemical elements was made by solid-state X-ray spectroscopy or by solution analysis. The designation of the alloys follows the rules of The Aluminum Association, known to those skilled in the art. The metallurgical states are defined in the European standard EN 515. The chemical composition of standardized aluminum alloys is defined for example in the standard EN 573-3. Unless otherwise stated, the static mechanical characteristics, ie the breaking strength R _m , the yield _stress R _p0,2 , and the elongation at break A, are determined by a tensile test according to EN 10002-1 standard, the location and direction of specimen collection being defined in EN 485-1. The yield strength in compression was measured by a test according to ASTM E9. Toughness K _IC was measured according to ASTM E 399. The R-curve is determined according to ASTM 561-98 standard. From the curve R, the critical stress intensity factor K _C is calculated, ie the intensity factor which causes the instability of the crack. The stress intensity factor K _{CO is} also calculated by assigning to the critical load the length initial crack, at the beginning of monotonous loading. These two values are calculated for a specimen of the desired shape. K _app denotes the K _CO corresponding to the test piece used to perform the R curve test. The resistance to exfoliating corrosion was determined according to the EXCO test described in the ASTM G34 standard.

Unless otherwise stated, the definitions of the European standard EN 12258-1 apply. The term "sheet metal" is used here for rolled products of any thickness.

The term "machining" includes any material removal process such as turning, milling, drilling, reaming, tapping, EDM, grinding, polishing.

The term "spun product" also includes products that have been drawn after spinning, for example by cold drawing through a die. It also includes drawn products.

The term "structural element" refers to an element used in mechanical engineering for which the static and / or dynamic mechanical characteristics are of particular importance for the performance and integrity of the structure, and for which a calculation of the structure is usually prescribed or performed. It is typically a mechanical part whose failure is likely to endanger the safety of said construction, its users, its users or others. For an aircraft, these structural elements include the elements that make up the fuselage (such as fuselage skin (fuselage skin in English), stiffeners or stringers, bulkheads, fuselage (circumferential frames), wings (such as wing skin), stiffeners (stiffeners), ribs (ribs) and spars) and empennage including horizontal stabilizers and vertical stabilizers horizontal or vertical stabilizers, as well as floor beams, seat tracks and doors.

The term "monolithic structure element" refers to a structural element that has been obtained from a single piece of semi-finished product, rolled, forged or molded, without assembly, such as riveting, welding, bonding, with another room.

où TEQ(160°C) est le temps équivalent à 160°C correspondant à un revenu d'une durée de t_réel à T_réel (en °K), où Q est une énergie d'activation de 132000 kJ/mol et R=8.31 kJ/mol/(°K).In determining the tempering times at a given temperature, the notion of time equivalent to a reference temperature (for example at 160 ° C.) is used. The calculation below gives the formula used: $$\mathit{TEQ}\left(160°\mathrm{VS}\right)=\exp \left[\frac{\mathrm{<figure-callout\; id="1"\; label="Q\; R"\; filenames="imgf0001.png"\; state="\{\{state\}\}">Q\; </figure-callout>}}{R}\left(\frac{1}{\left(160+273\right)}\frac{1}{\left(t_{\mathit{real}}+273\right)}\right)\right]\times t_{\mathit{real}}$$

where TEQ (160 ° C) is the time equivalent to 160 ° C corresponding to an income of a duration of _real t at _real T (in ° K), where Q is an activation energy of 132000 kJ / mol and R = 8.31 kJ / mol / (° K).

b) Detailed description of the invention

According to the invention, the problem is solved by the use of products spun in the form of a tube having the combination of a fine adjustment of the content of alloying elements and conditions of the heat treatment, in particular the homogenization of the raw forms. , as well as the solution and the income of the products obtained by hot transformation.

• Zn 6,7 - 7,5 (de préférence : 6,9 - 7,3) ;
• Cu 2,0 - 2,8 (de préférence : 2,2 - 2,6) ;
• Mg 1,6 - 2,2 (de préférence 1,8 - 2,0) ;
• Zr 0,08-0,20,
• Fe + Si < 0,20 et préférentiellement < 0,15 ;

autres éléments ≤ 0,05 chacun et ≤ 0,15 au total ;
le reste aluminium.In the use according to the invention, an alloy of composition is first prepared

• Zn 6.7 - 7.5 (preferably 6.9 - 7.3);
• Cu 2.0 - 2.8 (preferably: 2.2 - 2.6);
• Mg 1.6 - 2.2 (preferably 1.8 - 2.0);
• Zr 0.08-0.20,
• Fe + Si <0.20 and preferentially <0.15;

other elements ≤ 0.05 each and ≤ 0.15 in total;
the rest aluminum.

In the context of the present invention, the content of alloying elements must not significantly exceed their solubility limit, otherwise the persistence of intermetallic phases during the dissolution process, which can adversely affect damage tolerance. For a given magnesium content, the copper content can be brought to a level fairly close to the solubility limit, which depends on the magnesium content. Thus, a composition in which 3.8 <Cu + Mg <4.8, and preferably 3.9 <Cu + Mg <4.7 is preferred. In an advantageous embodiment of the invention, 4.0 <Cu + Mg <4.8 is chosen. In another advantageous embodiment, 4.1 <Cu + Mg <4.7 is chosen
Below a magnesium content of about 1.6% there is a risk of slits forming during casting, and a minimum content of about 1.7% or even 1.8% is preferred. The ratio Cu / Mg must be at least 1.0 in order to obtain a good compromise of properties, and in particular a good tolerance to damage, but must not exceed 1.5 to ensure acceptable flowability. It is preferred that it be between 1.1 and 1.5, and even more preferably between 1.1 and 1.4.
The applicant has found that above a magnesium content of about 2.2%, it no longer obtains acceptable toughness properties.

In an advantageous embodiment of the invention, the magnesium and copper content is chosen such that 4.2 <Cu + Mg <4.7 and Cu / Mg are between 1.15 and 1.45.
The addition of zirconium at a level of 0.08-0.20% limits the recrystallization. A Zr content of not more than 0.15% is preferred to avoid the formation of primary phases. When several of these antirecrystallizing elements are added, their sum is limited by the appearance of the same phenomenon. In an advantageous embodiment, only zirconium is added.

This alloy is then cast according to one of the techniques known to those skilled in the art to obtain a raw form, such as a spinning billet or a rolling plate. This raw form is then homogenized. The purpose of this heat treatment is threefold: (i) to dissolve the coarse soluble phases formed on solidification (ii) to reduce the concentration gradients to facilitate the dissolution stage and (iii) to precipitate the dispersoids in order to limit / to suppress the recrystallization phenomena during the dissolution stage. The Applicant has found that the alloy according to was characterized by a particularly low end of solidification temperature compared to the 7040, 7050 or 7475 type alloys. The same is true of the temperature above which the partial melting is observed. from the alloy to the thermodynamic equilibrium (so-called solidus temperature). For these reasons, homogenization with a rapid rise to a single temperature creates a risk of burning, and does not give a satisfactory dissolution of the particles. Homogenization in at least two steps reduces this risk and improves the result. In a preferred embodiment, the homogenization is carried out in two stages, with a first stage between 452 and 473 ° C., typically for a period of between 4 and 30 hours (preferably between 4 and 15 hours), followed by second step between 465 and 484 ° C, and preferably between 467 and 481 ° C, typically for a period of between 4 and 30 hours (preferably between 4 and 16 hours). In a particular embodiment, the first step is carried out between 457 and 463 ° C, and the second between 467 and 474 ° C. In another embodiment, the homogenization is carried out in a single stage with a linear rise at 40 ° C. per hour to a temperature of between 467 and 481 ° C., preferably between 471 and 481 ° C., and typically during a duration of between 4 and 30 hours.
It is also possible to homogenize in three stages. The homogenization can also be carried out in a single step, with a temperature rise below 200 ° C./h, and preferably between 20 and 50 ° C./h up to a plateau between 465 and 484 ° C., and preferentially between 471 and 481 ° C.

The raw form is then hot processed to form products spun in the form of tubes. The spinning is preferably done at a die temperature included between 380 and 430 ° C, and preferably between 390 and 420 ° C, by one of the methods known to those skilled in the art, such as direct spinning or reverse spinning. It is preferred that the hot-spinning process be carried out with a billet temperature between 400 and 460 ° C, and preferably between 420 ° C and 440 ° C.
It is thus possible to obtain spun products which nowhere show a coarse cortical layer with a thickness greater than 3 mm, and preferably limited to 1 mm, especially in the case of less thick spun products.

The hot transformation can optionally be followed by a cold transformation. For example, spun and drawn tubes can be made.

The products obtained are then dissolved. In a preferred embodiment of the invention, the temperature is continuously increased for a period of between 2 and 6 hours, and preferably approximately 4 hours, up to a temperature of between 470 and 500 ° C. (preferentially not exceeding 485 ° C.). ° C), preferably between 474 and 484 ° C, and even more preferably between 477 and 483 ° C, and maintains the product at this temperature for a period of between 1 and 10 hours, and preferably about 2 to 4 hours. Then, the products are quenched, preferably in a preferably liquid quenching medium such as water, said liquid preferably having a temperature not exceeding 40 ° C.

Then, the products can be subjected to controlled traction with a permanent elongation of the order of 1 to 5%, and preferably 1.5 to 3%.

Then, the products are subjected to a treatment of income, which influences in a big way on the final properties of the product. The plaintiff found that double-income income was good. However, income can be realized in three stages, or as ramping income. One can even consider an income in one step.
For a two-step process, a first stage of between 110 ° C and 130 ° C is suitable. In an advantageous embodiment of the present invention, the first stage is between 115 ° C and 125 ° C. For this preferred temperature range, an equivalent TEQ treatment time (160 ° C.) of between 0.1 and 2 hours, and preferably between 0.1 and 0.5 hours, may be used. The second stage is advantageously between 150 and 170 ° C. According to the findings of the applicant, if one aims to optimize the compromise between R _0.2 and K _app , the equivalent treatment time TEQ (160 ° C) for this second stage is advantageously between 4 and 16 hours, and preferably included between 6 and 12 o'clock. If the aim is to optimize the compromise between R _0.2 and K _IC , a second longer stage at a temperature of between 150 ° C and 170 ° C is preferable, for example an equivalent treatment time TEQ (160 ° C) included between 16 and 30 hours. In an advantageous embodiment, the second stage was carried out at a temperature of 160 ° C. for 24 hours.
In a first particular embodiment, the temperature of the second stage is between 155 and 165 ° C. The control of the duration of this second stage is particularly important for the final properties of the product. In a particularly advantageous embodiment of this first particular embodiment, the second stage is between 157 and 163 ° C, and its duration is between 6 and 10 hours. In another particular embodiment of the invention, the second stage is carried out at a slightly lower temperature, between 150 and 160 ° C.

If one considers a monogonal income, it will be advantageous to use a temperature of the order of 115 to 145 ° C for a duration of the order of 4 to 50 hours, for example 48 hours at 120 ° C. For example, an equivalent TEQ processing time (160 ° C.) of the order of 0.6 hours to 1.20 hours can be used. These single-stage treatments make it possible to obtain products in the T6 state.

The use according to the invention, thanks to the compromise of properties, is very interesting for applications that require both a high mechanical strength, and a high tolerance against occasional overloads without leading to the sudden rupture of the part. The use of spun products in the form of tubes according to the invention is suitable for the manufacture of parts or structural elements which meet high safety requirements. Applicant has manufactured by spinning, possibly followed by a cold drawing, tubes for the manufacture of frames, forks and handlebar cycles (bicycles, tricycles, motorcycles etc.), or baseball bats. A method of manufacture is preferably chosen which leads to a fiber structure of the tubes.

The invention will be better understood with the aid of the examples, which are however not limiting in nature.

Examples

Examples 1 to 5 and the alloys N and O of Example 6 are not part of the invention but are useful for understanding the invention.

Example 1

1. 1) 13 heures à 460 °C
2. 2) 14 heures à 470 °C.

Tableau 1 Alliage Zn Mg Cu Fe Si Zr Ti Mn A 6,75 1,9 2,6 0,08 0,05 0,12 0,03 0,01 The spinning billets with a diameter of 291 mm (alloy A), the composition of which is indicated in Table 1, were cast by semi-continuous casting. These billets were homogenized in two stages:

1. 1) 13 hours at 460 ° C
2. 2) 14 hours at 470 ° C.

<u> Table 1 </ u> Alloy Zn mg Cu Fe Yes Zr Ti mn AT 6.75 1.9 2.6 0.08 0.05 0.12 0.03 0.01

The content of Cu, Mg and Zn was determined by chemical analysis after dissolution of a part of the sample, while the other elements were determined by solid X-ray spectroscopy.

Section sections "I" were spun (see Figure 1 : thickness of the order of 17 mm to 22 mm, width of the order of 160 mm and height of the order of 80 mm) from peeled billet diameter 270 mm, at a temperature of between 390 and 410 ° C and a container temperature of between 400 and 420 ° C, with an exit velocity of about 0.5 m / min. The profiles were dissolved by increasing the temperature continuously for 3 hours to 481 ± 3 ° C and keeping them at this temperature for 6 hours, then quenched in water between 22 and 25 hours. ° C and tractionned with a permanent deformation between 1.5 and 3%. Over-treatment was then performed to obtain T76 products. The over-income was carried out in two stages: first at 120 ° C for 6 hours, then at 160 ° C for a variable period. The thickness of the recrystallized coarse grain layer measured in the center of the soleplate is less than 1 mm. To characterize the products obtained, their static mechanical characteristics (R _m , R _p0.2 , A) according to EN 10001-2, their resistance to exfoliating corrosion according to ASTM G34 ("Exco" test), their resistance were determined. stress corrosion according to ASTM G 47, their crack propagation speed according to ASTM E647 (so-called "da / dn" test) in the TL or LT direction for a ΔK value of 50 MPa√m and a charge ratio R = 0.1 and their stress intensity factor K _app (so-called "apparent K" parameter). The latter was calculated using the maximum load measured during the test according to ASTM E561-98 on specimens of width W equal to 100 mm, and the initial crack length (at the end of pre-cracking) in the formulas indicated by the standard cited.

Table 2 shows the influence of the duration of the second income stage on certain properties measured at the end of the profile; the mechanical characteristics having been measured at 20 ° C. The results of the tensile test were obtained on specimen of circular section, diameter 10 mm, half-thickness and half-width in the long branch. The KIc toughness results were obtained on specimens taken at mid-thickness and mid-width in the long branch or the thickest branch. The EXCO corrosion results were obtained on specimens taken at mid-thickness and half-width in the branch. The results of Kapp were obtained on specimens mid-thickness and centered in the sole of the profile containing the long branch. Table 2: Duration of the ^2nd stage of income 8 am 12 h 24 h TEQ (160 ° C) 8.71 h 12.71 h 24.71 EXCO: surface EA EA EA EXCO: T / 10 EB EB EB EXCO: T / 2 EA EA EB K _{app (LT)} [MPa√m] (soleplate) 89.3 83.0 80.2 K _{IC (LT)} [MPa√m] (long branch) 38.8 40.5 43.5 K _{IC (LT)} [MPa√m] (thick branch) 45.7 42.6 46.6 K _{IC (TL)} [MPa√m] (long branch) 27.0 28.6 30.7 K _{IC (TL)} [MPa√m] (thick branch) 24.5 26.1 29.2 R _{m (L)} [MPa] (long limb) 629 616 561 R _{m (L)} [MPa] (thick branch) 646 621 572 R _{p0,2 (L)} [MPa] (long branch) 604 582 507 R _{p0,2 (L)} [MPa] (thick branch) 621 586 519 A _(L) [%] (long arm) 12.6 13.2 13.9 A _(L) [%] (thick branch) 12.4 13.1 13.3 EXCO: resistance to exfoliating corrosion, determined by EXCO surface test; at 1/10 of the thickness (T / 10) and at mid-thickness (T / 2) in the long branch K _{app (LT)} : measured with a CCT test specimen W = 100mm and B = 6 mm K _{IC (LT or TL)} (long branch): with B = 12.5 mm and W = 25 mm K _{IC (LT or TL)} (thick branch): with B = 15 mm and W = 30 mm

We note that a duration of 8 hours or 12 hours gives very good results.

The K _{apP (LT)} toughness at -50 ° C was 87.6 MPa√m for an 8 hour income, and 83.5 MPa√m for a 24 hour duration (on specimens with B = 6 mm).
For a product having undergone a second stage of recovery at 160 ° C for 8 hours, the LT properties were at 20 ° C: $${\mathrm{<figure-callout\; id="2"\; label="R\; p"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R\; </figure-callout>}}_{\mathrm{p}}=579\mathrm{MPa},R_{\mathrm{m}\left(\mathrm{LT}\right)}=609\mathrm{MPa},\mathrm{AT}\left(\mathrm{LT}\right)=12\%\mathrm{.}$$

Table 3 shows the crack propagation speed measured in the LT direction with B = 7.61 mm, W = 96.6 mm, R = 0.10, and P _min = 600 N and P _max = 6000 N for a duration of income of 6 hours at 120 ° C and 8 hours at 160 ° C. The "Compact-voltage panel" type samples were taken at mid-thickness and half-width of the sole at the end of the profile. Table 3: ΔK [MPa√m] da / dn [mm / cycle] at 20 ° C da / dn [mm / cycle] at -54 ° C 10 9.50 10 ^-5 5.74 10 ^-6 15 4.44 10 ^-4 2.48 10 ^-4 20 1.01 10 ^-3 6.76 10 ^-4 25 2.04 10 ^-3 1.10 10 ^-3 30 3.55 10 ^-3 2.24 10 ^-3

Stress corrosion samples were taken at the end of the profile at mid-thickness of the sole at two positions in the section: at mid-width of the long branch and at mid-width of the opposite branch in the sole. The results of corrosion resistance under constant stress in the TL direction with σ = 300, 350 and 400 MPa of imposed stress are presented in Table 4. The monitoring of these tests stopped after 30 days. Table 4: Duration of the ^2nd stage of income 8 am 24 h TEQ (160 ° C) 8.71 h 24.71 σ = 300 MPa > 30 days (6 samples) > 30 days (6 samples) σ = 350 MPa > 30d (3 samples) > 30d (3 samples) σ = 400 MPa ≥24j (3 samples) > 30d (3 samples)

Stress corrosion samples in a corrosive medium were taken at mid-thickness and half-width of the long branch at the end of the profile. The crack propagation in corrosive medium in the thickness direction (determined by the so-called double cantilever beam (DCB) method according to EN ISO 7539-6) was of the order of 5 10 ^-9 m / s for a second income level of 8 hours at 160 ° C.

Example 2

An alloy whose composition is shown in Table 5 was cast. Spinning billets having a diameter of 410 mm were cast. The homogenization conditions were the same as in Example 1. After peeling, there were obtained billets with a diameter of 390 mm. They were spun with a temperature of between 410 and 430 ° C and a container temperature of about 420 ° C with an exit speed of 0.65 to 0.8 m / min, in flats of section 279 x 22 mm. <u> Table 5 </ u> Alloy Zn mg Cu Fe Yes Zr Ti Cr mn K 6.78 1.91 2.49 0.08 0.05 0.11 0.03 0.00 0.01

The products were put in solution with a rise in temperature in 35 minutes up to 479 ± 2 ° C, with a step of 4 hours at this temperature. The quenching was carried out in cold water. Then, the flats were tractionned with a permanent elongation of between 1.5 and 3%. The income was made in two stages: 6 hours at 120 ° C + 8 hours at 160 ° C. Ultrasonic testing verified the absence of internal defects (class AA MIL-STD-2154). The thickness of the recrystallized coarse grain layer measured at the center of the soleplate is less than 1 mm.

The results of the tensile and compressive test are given in Table 6. The results of the tensile test were obtained on specimens of circular section, diameter 10 mm, at mid-thickness at the end of the flat and in two positions. in the section: mid-width and edge. The results of the compression test were obtained on specimen of circular section, diameter 10 mm, at mid-thickness at the end of the flat and at two positions in the section: at mid-width and edge. Table 6 R _{m (L)} [MPa] R _{p0.2 (L)} [MPa] A _(L) [%] R _{p0.2c (L} ) [MPa] R _{m (TL)} [MPa] R _{p0.2 (TL)} [MPa] A _(TL) [%] R _{p0,2c (TL)} [MPa] half width 631 602 12.2 604 609 583 11.3 614 edge 645 617 13.5 627 - - -

The K _IC , K _app and EXCO corrosion toughness results were obtained on specimens taken at mid-thickness and half-width at the end of the flat. The toughness and corrosion results are collated in Table 7. The test conditions are the same as those set forth in Example 1. Table 7 EXCO: surface EA EXCO: T / 2 EB K _{app (LT)} [MPa√m] 75.4 K _{IC (LT)} [MPam] 31.0 K _{IC (TL)} [MPa√m] 29.7 K _{app (LT)} : measured with B = 6 mm K _{IC (LT or TL)} : with B = 10 mm and W = 20 mm

Stress corrosion samples were taken at the end of the profile at mid-thickness and on both sides of the half-width. The results of corrosion resistance under constant stress in the TL direction with σ = 300, 350 and 400 MPa of imposed stress are shown in Table 8. The monitoring of these tests stopped after 40 days. <u> Table 8 </ u> Duration of the ^2nd stage of income 8 am TEQ (160 ° C) 8.71 h σ = 300 MPa > 40 days (3 samples) σ = 350 MPa > 40 days (3 samples) σ = 400 MPa ≥33j (3 samples)

Example 3:

Profiles of different geometries were spun from billets of composition A (see Example 1). The figure 2 shows the section of these profiles. The manufacturing method was similar to that of Example 1. The thickness of the product is of the millimeter order compared to the previous products. Nevertheless a microstructure with a small cortical layer with coarse grains could be obtained. Table 9 shows the static mechanical characteristics obtained for different income conditions. The first stage of income was always 6 hours at 120 ° C. <u> Table 9 </ u> Duration of the ^2nd stage of income at 160 ° C TEQ (160 ° C) R _{m (L)} [MPa] R _{p0.2 (L)} [MPa] A _(L) [%] EXCO surface EXCO T / 2 1 hour 1.77 635 595 11 P ED 2 hours 2.77 634 600 11 P ED 3 hours 3.77 632 602 9 P ED 4 hours 4.71 628 601 11 P ED 8 hours 8.71 621 593 10 P EB 16 hours 16.71 597 559 10 P EA / EB 32 hours 32.71 541 482 11 P EA / EB

The T6 state is close to the 6 hour point at 120 ° C + 1 h at 160 ° C.
Table 10 shows some tenacity-static mechanical characteristics compromise for some points corresponding to T7x states. The test conditions are the same as those presented in Example 1. Table 10 Duration of the ^2nd stage of income 8 am 12 h 24 h TEQ (160 ° C) 8.71 h 12.71 h 24.71 EXCO: surface P P P EXCO: T / 2 EB EB EA / EB K _{app (LT)} [MPa√m] 86.4 83.1 80.0 R _{m (L)} [MPa] 619 614 576 R _{p0.2 (L)} [MPa] 588 577 522 A _(L) [%] 12.5 10.9 11.7 EXCO: resistance to exfoliating corrosion, determined by EXCO surface test; mid-thickness (T / 2)

These profiles were used for the manufacture of fuselage frames.

Example 4

Inverted section 'T' sections were spun (see Figure 3 : thickness of the sole of the order of 25 mm, width of the reinforcement of the order of 40 mm, width of the sole of the order of 180 mm and height of the order of 70 mm) from billets of composition K (see example 2). The spinning conditions were similar to those of Example 2.

Three profiles labeled X, Y and Z have separately undergone the stages of solution dissolution, quenching and traction. The profiles X and Y have been dissolved as in Example 2. The Z profile has been dissolved in a temperature rise between 1h and 2h and maintaining 3 hours at 480 ± 2 ° C. The three sections were soaked in cold water and triturated between 1.5% and 3%. The profiles have been rectified to improve their straightness. The income was made in two stages with a first 6 hour stage at 120 ° C. Ultrasonic testing was performed to check for internal defects (Class A, MIL-STD-2154). The thickness of the recrystallized coarse grain layer measured at the center of the soleplate is less than 1 mm.

Tables 11, 12 and 13 show the influence of the duration of the second income stage on certain properties of the product for the three profiles respectively X, Y and Z; the mechanical characteristics having been measured at 20 ° C. The test conditions are the same as those presented in Example 1. The results of the tensile test were obtained on specimen of circular section, diameter 10 mm, half-thickness and half-width in the long limb. . The KIc toughness results and EXCO corrosion was obtained on specimens taken at mid-thickness and mid-width in the long limb. The results of Kapp were obtained on specimens centered in the sole of the profile containing the long branch. Table 11 - X Profile Duration of the ^2nd stage of income 24 h TEQ (160 ° C) 24.71 EXCO: surface EA EXCO: T / 2 EA K _{epp (LT)} [MPa√m] 76.2 K _{IC (LT)} [MPa√m] (B = 15 mm W = 30 mm) 43.8 K _{IC (TL)} [MPa√m] (B = 15 mm W = 30 mm) 28.4 K _{IC (LT)} [MPa√m] (B = 20 mm W = 76.2 mm) 45.6 K _{IC (TL)} [MPa√m] (B = 20 mm W = 76.2 mm) 30.0 R _{m (L)} [MPa] 576 R _{p0.2 (L)} [MPa] 526 A _(L) [%] 13.3 R _{p0.2c (L)} [MPa] 533 R _{m (TL)} [MPa] 545 R _{p0.2 (TL)} [MPa] 500 A _(TL) [%] 8.2 EXCO: resistance to exfoliating corrosion, determined by the EXCO test at the surface and at mid-thickness (T / 2) K _{app (LT)} : measured with B = 6 mm Duration of the ^2nd stage of income 8 am TEQ (160 ° C) 8.71 h K _{app (LT)} [Mpa√m] 87.6 R _{m (L)} [MPa] 639 R _{p0.2 (L)} [MPa] 609 A _(L) [%] 12.5 K _{app (LT)} : measured with B = 6 mm Duration of the ^2nd stage of income 8 am 24 h TEQ (160 ° C) 8.71 24.71 K _{app (LT)} [MPa√m] 84.2 75.4 K _{IC (LT)} [MPa√m] 33.0 - K _{IC (TL)} [MPa√m] 24.7 - R _{m (L)} [MPa] 650 R _{p0.2 (L)} [MPa] 621 At _(L) [%] 12.2 R _{m (TL)} [MPa] 602 R _{p0.2 (TL)} [MPa] 579 A (TL) [%] 8.5 K _{app (LT)} : measured with B = 5 mm K _{IC (LT or TL)} : with B = 25 mm and W = 76 mm

We note that a duration of 8 hours or 24 hours for the 2nd stage of income gives very good compromises of results.

Stress corrosion samples were taken at the end of the profile at mid-thickness of the sole at two positions in the section: at mid-width of the long branch and at mid-width of the opposite branch in the sole. The results of corrosion resistance under constant stress in the TL direction with σ = 300, 350 and 400 MPa of imposed stress are presented in table 14. The follow-up of these tests stopped after 40 days. <U> Table </ u><u> 14 </ u> Duration of the ^2nd stage of income 8 am 24 h TEQ through (160 ° C) 8.71 h 24.71 σ = 300 MPa > 40j (4 samples) > 40j (4 samples) σ = 350 MPa ≥24j (4 samples) > 40j (4 samples) σ = 400 MPa ≥21j (4 samples) ≥38j (4 samples)

Example 5:

An alloy whose composition is shown in Table 15 was cast. Spinning billets having a diameter of 525 mm were cast. The homogenization conditions were 15 hours between 473 and 481 ° C. after a controlled temperature increase at 40 ° C./h. After peeling, billets having a diameter of 498 mm were obtained. They were spun in a container at a temperature between 410 and 430 ° C and a billet entered at 420 and 440 ° C, with an exit velocity between 0.6 m / min and 1.0 m / min in the form of an illustrated section on the figure 3 (Thickness of the sole of the order of 27 mm, width of the reinforcement of the order of 40 mm, width of the sole of the order of 205 mm and height of the order of 80 mm). <U> Table </ u><u> 15 </ u> Alloy Zn mg Cu Fe Yes Zr Ti Cr mn H 6.95 1.89 2.18 0.06 0.04 0.10 0.02 0.00 0.00

The products were dissolved with a rise in temperature between 1h and 2h up to 480 ± 2 ° C, with a plateau of 3 hours at this temperature. The quenching was carried out in cold water between 21 and 22 ° C. Then the extruded sections and quenched were triturated with a permanent elongation of between 1.5 and 3%. The profiles have been rectified to improve their straightness. A first income of 6h at 120 ° C was achieved. Ultrasonic testing was performed to check for internal defects (Class A, MIL-STD-2154). A second income was made for 8 hours at 160 ° C. The thickness of the recrystallized coarse grain layer measured at the center of the soleplate is less than 1 mm.

The results of the tensile test (on specimen of circular section, diameter 10 mm, taken at the end of the profile, at mid-thickness and half-width in the long branch) are collated in table 16. This table also contains the toughness results and Kapp both taken from the soleplate. The test conditions are the same as those presented in Example 1 except for the thickness B of the CCT test specimen for Kapp characterization which is 5 mm. <u> Table 16 </ u> Duration of the ^2nd stage of income 8 am 24 h TEQ (160 ° C) 8.71 24.71 K _{app (LT)} [MPa√m] 84.1 79.3 K _{IC (LT)} [MPa√m] (soleplate) 37.2 - K _{IC (TL)} [MPa√m] (soleplate) 28.8 - R _{m (L)} [MPa] (soleplate) 637 R _{p0,2 (L)} [MPa] (soleplate) 609 A _(L) [%] (sole) 13.2 R _{m (TL)} [MPa] (soleplate) 602 R _{p0,2 (TL)} [MPa] (soleplate) 577 A _(TL) [%] (soleplate) 9.9 K _{app (LT)} : measured with B = 5 mm K _{IC (LT or TL)} : with B = 25 mm and W = 76 mm

Example 6

Bills with L, M, N and O compositions were cast with diameters of 200 mm (see Table 17). All the compositions have undergone the same homogenization between 473 ° C. and 481 ° C. for 15 hours. After homogenization the billets were crimped and drilled in the center to allow needle spinning. Seamless tubes were spun. The spinning blanks were cold drawn to produce tubes with a diameter of between 20 and 30 mm and a wall thickness between 2 and 5 mm. Cold drawing increases the stored energy that is the main driver of recrystallization. The variation of the transition elements (see Table 17) made it possible to generate different microstructures. After stretching; the tubes were dissolved at temperatures above 480 ° C for 1 h before cold water quenching (~20 ° C).
The tubes were not pulled after quenching. A first stabilization step for 6 hours at 120 ° C. was carried out before complete kinetics as shown in Tables 18 to 20. The mechanical properties were measured on specimens curved in the direction of spinning L. Table 17 Alloy Zn mg Cu Fe Yes Zr Ti Cr mn sc Hf The 7.01 1.84 2.37 0.06 0.03 0.14 0.04 0.00 0.00 0.00 0.00 M 6.79 1.79 2.30 0.06 0.03 0.13 0.04 0.00 0.00 0.07 0.00 NOT 6.78 1.75 2.29 0.10 0.04 0.00 0.04 0.00 0.00 0.00 0.46 O 6.74 1.82 2.31 0.12 0.04 0.06 0.04 0.00 0.00 0.00 0.41 Duration of the ^2nd income step at 160 ° C TEQ R _{m (L)} [MPa] R _{p0.2 (L)} [MPa] A _(L) [%] 2 hours 2.77 620 571 13.7 4 hours 4.71 619 584 15.6 8 hours 8.71 606 581 9.6 12 hours 12.71 597 568 12.7 16 hours 16.71 580 541 12.0 24 hours 24.71 537 482 12.5 32 hours 32.71 521 458 12.4 Duration of the ^2nd stage of income at 160 ° C TEQ R _{m (L)} [MPa] R _{p0.2 (L)} [MPa] A _(L) [%] 2 hours 2.77 653 622 14.2 12 hours 12.71 616 588 10.5 16 hours 16.71 596 560 15.1 24 hours 24.71 554 506 11.2 Duration of the ^2nd stage of income at 160 ° C TEQ R _{m (L)} [MPa] R _{p0.2 (L)} [MPa] A _(L) [%] 2 hours 2.77 611 557 11.9 12 hours 12.71 593 559 11.6 24 hours 24.71 543 487 14.2 Duration of the ^2nd stage of income at 160 ° C TEQ R _{m (L)} [MPa] R _{p0.2 (L)} [MPa] A _(L) [%] 2 hours 2.77 606 551 10.7 12 hours 12.71 586 554 11.3 16 hours 16.71 572 531 13.9 24 hours 24.71 535 478 12.5

The T6 state is close to the 6 hour point at 120 ° C + 1 h at 160 ° C.

These tubes are used for sports and leisure market applications: frames, forks and handlebars cycles, baseball bats, such use of alloy tube L being according to the invention.

Claims (17)

1. Use of an extruded product in the form of an aluminium alloy tube, characterised in that it comprises (as a % by mass):

   (a) Zn 6.7 - 7.5% Cu 2.0 - 2.8% Mg 1.6 - 2.2%;

   (b) Zr 0.08 - 0.20% Fe + Si < 0.20%;

   (c) other elements ≤ 0.05% each and ≤ 0.15% in total;

   (d) the remainder aluminium,

   for the manufacture of cycle frames, forks and handlebars or baseball bats.
2. Use according to claim 1, characterised in that the magnesium and copper content thereof is such that 3.8 < (Cu + Mg) < 4.8,
   and preferably 3.9 < (Cu + Mg) < 4.7,
   and more preferentially 4.1 < (Cu + Mg) < 4.7.
3. Use according to claim 1 or 2, characterised in that the Cu:Mg ratio is between 1.0 and 1.5, preferentially between 1.1 and 1.5, and more preferentially between 1.1 and 1.4.
4. Use according to any one of claims 1 to 3, characterised in that Zn is between 6.9 and 7.3%.
5. Use according to any one of claims 1 to 4, characterised in that Cu is between 2.2 and 2.6%.
6. Use according to any one of claims 1 to 5, characterised in that Mg is between 1.7 and 2.0%, and preferentially between 1.8 and 2.0%.
7. Use according to any one of claims 1 to 6, characterised in that the alloy further contains up to 0.8% manganese.
8. Use according to any one of claims 1 to 7, characterised in that Si + Fe does not exceed 0.15%.
9. Use according to any one of claims 1 to 8, characterised in that the tube has undergone solution heat treatment, stretching and ageing, said ageing including a first stage at a temperature between 110°C and 125°C, and preferentially between 115 and 125°C, and a second stage at a temperature between 150 and 170°C, and preferentially between 150 and 165°C.
10. Use of an extruded product in the form of an aluminium alloy tube according to any one of claims 1 to 9, characterised in that the method for manufacturing the tube comprises the following steps:

    (a) preparing an alloy having a composition according to any one of claims 1 to 9,

    (b) casting a crude form such as a rolling ingot or an extrusion or forging billet,

    (c) homogenising said crude form,

    (d) hot transformation to obtain a first intermediate product,

    (e) solution heat treating said first intermediate product,

    (f) quenching

    (g) optionally controlled stretching,

    (h) ageing.
11. Use according to claim 10, characterised in that the homogenisation (step a) is performed in two steps, with a first stage between 452 and 473°C, preferentially between 457 and 473°C, and a second stage between 465 and 484°C, and preferentially between 467 and 481°C.
12. Use according to claim 10, characterised in that the homogenisation (step a) is performed in a single step, with a temperature rise less than 200°C/hour, and preferentially between 20 and 50°C/hour up to a stage between 465 and 484°C, and preferentially between 471 and 481°C.
13. Use according to any one of claims 10 to 12, characterised in that hot transformation is performed by extrusion with a billet temperature between 400 and 460°C, and preferentially between 420°C and 440°C.
14. Use according to any one of claims 10 to 13, characterised in that the solution heat treatment temperature does not exceed 500°C, and preferably does not exceed 485°C.
15. Use according to claim 14, characterised in that the solution heat treatment ends with a stage between 470 and 485°C, preferentially between 475 and 484°C, and more preferentially between 477 and 483°C for a period between 1 and 10 hours.
16. Use according to any one of claims 10 to 15, characterised in that the controlled stretching results in a permanent elongation between 1 and 5%, and preferentially between 1.5 and 3%.
17. Use according to any one of claims 10 to 16, characterised in that the ageing treatment includes

    a) a first stage at a temperature between 110°C and 130°C, and preferentially between 115 - 125°C, and preferably, in the latter case, for a period between 2 and 10 hours, and more preferentially between 5 and 7 hours;

    b) a second stage at a temperature between 150°C and 170°C, and preferentially between 155 and 165°C, and more preferentially between 157 and 163°C, and preferably for a period between 4 and 12 hours, and more preferentially between 6 and 10 hours.

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