CN112041473A - Aluminum-copper-lithium alloy with improved compressive strength and improved toughness - Google Patents

Abstract

The invention relates to an aluminium alloy based product comprising: 4.0 to 4.6 wt.% Cu, 0.7 to 1.2 wt.% Li, 0.5 to 0.65 wt.% Mg, 0.10 to 0.20 wt.% Zr, 0.15 to 0.30 wt.% Ag, 0.25 to 0.45 wt.% Zn, 0.05 to 0.35 wt.% Mn, up to 0.20 wt.% Fe + Si, at least one element selected from Cr, Sc, Hf, V and Ti, the amount of said element (if selected) being 0.05 to 0.3 wt.% for Cr and Sc, 0.05 to 0.5 wt.% for Hf and V, 0.01 to 0.15 wt.% for Ti; the other elements are each up to 0.05% by weight and in total up to 0.15% by weight, the remainder being aluminium. The invention also relates to a method for obtaining such a product and to the use thereof for structural elements of aircraft.

Description

Aluminum-copper-lithium alloy with improved compressive strength and improved toughness

Technical Field

The present invention relates to products made of aluminium-copper-lithium alloys, more particularly such products intended for aeronautical and aerospace construction.

Prior Art

Aluminium alloy products are developed to produce high strength parts intended for use in particular in the aerospace industry.

In this regard, lithium-containing aluminum alloys are of great interest because lithium can reduce the density of aluminum by 3% and increase the elastic modulus by 6% per 1 wt.% added lithium. For these alloys to be selected for use in aircraft, their properties, which are linked to other service characteristics, must meet those of the usual alloys, in particular in terms of a compromise between static mechanical strength properties (tensile and compressive yield strength, ultimate tensile strength) and damage tolerance properties (toughness, fatigue crack propagation resistance), which are generally mutually exclusive. For some parts, such as the upper wing skin, compressive yield strength is an important property. Furthermore, these mechanical properties should preferably be stable over time and have good thermal stability, i.e. they do not change significantly due to ageing at the operating temperature.

These alloys must also have sufficient corrosion resistance, be able to be shaped according to conventional methods, and have low residual stresses so that they can be fully machined. Finally, they must be able to be obtained by robust manufacturing methods, in particular their properties must be able to be obtained on industrial plants where it is difficult to ensure that large parts have a temperature uniformity within a few degrees.

Patent US 5,032,359 describes a large class of aluminium-copper-lithium alloys in which the addition of magnesium and silver, in particular 0.3 to 0.5% by weight, allows to improve the mechanical strength.

Patent US 5,455,003 describes a method of manufacturing Al-Cu-Li alloys having improved mechanical strength and improved toughness at low temperatures, in particular due to suitable work hardening and tempering (revenu). This patent recommends in particular the following composition: 3.0-4.5 percent of Cu, 0.7-1.1 percent of Li, 0-0.6 percent of Ag, 0.3-0.6 percent of Mg and 0-0.75 percent of Zn.

Patent US 7,438,772 describes an alloy comprising: by weight percent, Cu: 3-5, Mg: 0.5-2, Li: 0.01-0.9 and the use of higher lithium contents is not recommended due to the reduced compromise between toughness and mechanical strength.

Patent US 7,229,509 describes an alloy comprising (in weight%): (2.5-5.5) Cu, (0.1-2.5) Li, (0.2-1.0) Mg, (0.2-0.8) Ag, (0.2-0.8) Mn, up to 0.4 of Zr or other grain refiners (e.g. Cr, Ti, Hf, Sc, V).

Patent application US 2009/142222 a1 describes an alloy comprising (in weight%): 3.4 to 4.2% of Cu, 0.9 to 1.4% of Li, 0.3 to 0.7% of Ag, 0.1 to 0.6% of Mg, 0.2 to 0.8% of Zn, 0.1 to 0.6% of Mn and 0.01 to 0.6% of at least one element for controlling the granular structure. This application also describes a method of manufacturing an extruded product.

Patent application WO2009/036953 relates to an aluminium alloy product for structural elements, the chemical composition of which comprises: cu 3.4 to 5.0, Li 0.9 to 1.7, Mg 0.2 to 0.8, Ag about 0.1 to 0.8, Mn 0.1 to 0.9, Zn up to 1.5, and one or more elements selected from: (Zr about 0.05 to 0.3, Cr 0.05 to 0.3, Ti about 0.03 to 0.3, Sc about 0.05 to 0.4, Hf about 0.05 to 0.4), Fe <0.15, Si <0.5, conventional and unavoidable impurities.

Patent application WO 2012/085359 a2 relates to a method of manufacturing a rolled product made of an aluminium-based alloy comprising 4.2 to 4.6 wt.% Cu, 0.8 to 1.30 wt.% Li, 0.3 to 0.8 wt.% Mg, 0.05 to 0.18 wt.% Zr, 0.05 to 0.4 wt.% Ag, 0.0 to 0.5 wt.% Mn, up to 0.20 wt.% Fe + Si, less than 0.20 wt.% Zn, at least one element selected from Cr, Se, Hf and Ti, the amount of said element (if selected) being, for Cr and Se, 0.05 to 0.3 wt.%, for Hf, 0.05 to 0.5 wt.%, for Ti, 0.01 to 0.15 wt.%, the other elements each being up to 0.05 wt.% and in total, the remainder being aluminium; the method comprises the steps of preparing, casting, homogenizing, rolling at a temperature above 400 ℃, solution heat treating, quenching, stretching by 2% to 3.5%, and tempering.

Patent application US2012/0225271a1 relates to a forged product having a thickness of at least 12.7mm, containing 3.00 to 3.80 wt.% Cu, 0.05 to 0.35 wt.% Mg, 0.975 to 1.385 wt.% Li, wherein-0.3 Mg-0.15Cu +1.65 ≦ Li ≦ -0.3Mg-0.15Cu +1.85, 0.05 to 0.50 wt.% of at least one grain structure control element, wherein the grain structure control element is selected from Zr, Sc, Cr, V, Hf, other rare earth elements and combinations thereof, up to 1.0 wt.% Zn, up to 1.0 wt.% Mn, up to 0.12 wt.% Si, up to 0.15 wt.% Fe, up to 0.15 wt.% Ti, up to 0.10 wt.% of other elements, the total amount of the other elements not exceeding 0.35 wt.%.

Application WO 2013/169901 describes an alloy comprising the following elements: 3.5 to 4.4% of Cu, 0.65 to 1.15% of Li, 0.1 to 1.0% of Ag, 0.45 to 0.75% of Mg, 0.45 to 0.75% of Zn and 0.05 to 0.50% of at least one element for controlling the granular structure in weight percentage. Advantageously, the alloy has a Zn to Mg ratio of 0.60 to 1.67.

There is a need for aluminium-copper-lithium alloy products having improved properties compared to the properties of the known products, in particular a compromise between static mechanical strength properties (in particular tensile and compressive yield strength) and damage tolerance properties (in particular toughness, thermal stability, corrosion resistance and machinability), while having a low density.

Furthermore, there is a need for a robust, reliable and economical method of manufacturing these products.

Disclosure of Invention

A first object of the present invention is an aluminium alloy based product comprising: 4.0 to 4.6 wt.% Cu, 0.7 to 1.2 wt.% Li, 0.5 to 0.65 wt.% Mg, 0.10 to 0.20 wt.% Zr, 0.15 to 0.30 wt.% Ag, 0.25 to 0.45 wt.% Zn, 0.05 to 0.35 wt.% Mn, up to 0.20 wt.% Fe + Si, at least one element selected from Cr, Sc, Hf, V and Ti, the amount of said element (if selected) being 0.05 to 0.3 wt.% for Cr and Sc, 0.05 to 0.5 wt.% for Hf and V, 0.01 to 0.15 wt.% for Ti, the other elements each being up to 0.05 wt.% and the total being up to 0.15 wt.%, the remainder being aluminum.

A second object of the invention is a method for manufacturing a product based on an aluminium alloy, in which, in turn,

a) preparing an aluminum-based liquid metal bath comprising: 4.0 to 4.6 wt.% Cu; 0.7 to 1.2 wt% Li; 0.5 to 0.65 wt.% Mg; 0.10 to 0.20 wt.% Zr; 0.15 to 0.30 wt% Ag; 0.25 to 0.45 wt.% Zn; 0.05 to 0.35 wt.% Mn; up to 0.20 wt% Fe + Si; at least one element selected from the group consisting of Cr, Sc, Hf, V and Ti, in amounts (if selected) of from 0.05 to 0.3 wt% for Cr and Sc, from 0.05 to 0.5 wt% for Hf and V, and from 0.01 to 0.15 wt% for Ti; each of the other elements is up to 0.05 wt% and the total amount is up to 0.15 wt%, the remainder being aluminum;

b) casting a green article from the liquid metal bath;

c) homogenizing the crude product at a temperature of 450 ℃ to 550 ℃ and preferably 480 ℃ to 530 ℃ for 5 to 60 hours;

d) hot deforming, preferably by rolling, the homogenized raw product;

e) solution heat treating the hot deformed product at 490 to 530 ℃ for 15min to 8h and quenching the solution heat treated product;

f) cold-deforming the product with a deformation rate of 2 to 16%;

g) tempering is carried out, wherein the cold-deformed product is brought to a temperature of 130 to 170 ℃ and preferably 140 to 160 ℃ for 5 to 100 hours and preferably 10 to 70 hours.

Another object of the invention is an alloy product according to the invention or obtainable according to the method of the invention, having a thickness of 8 to 50mm, having the following properties at medium thickness:

i) compressive yield strength Rc_p0.2(L) ≥ 590MPa, preferably Rc_p0.2(L)≥595MPa；

ii) toughness K_app(L-T) 60MPa ≥ m, preferably K_app(L-T) ≧ 75MPa √ m, where Kapp (L-T) is the value of the apparent stress intensity factor at break defined according to standard ASTM E561(2015), measured on a CCT sample with a width W of 406mm and a thickness B of 6.35 mm;

iii) tensile yield strength Rp_0.2(L) and compressive yield strength Rc_p0.2Difference Rp between (L)_0.2(L)-Rc_p0.2(L) is less than or equal to 10MPa, preferably less than or equal to 5 MPa.

Another object is a structural component of an aircraft, preferably a wing skin element on the aircraft.

Drawings

FIG. 1: toughness K of the alloy of example 1_appL-T and compressive yield strength Rc_p0.2L is a compromise between.

FIG. 2: toughness K of the alloy of example 2_qL-T and compressive yield strength Rc_p0.2L is a compromise between.

FIG. 3: compressive yield strength Rc of the alloy of example 2_p0.2L and tensile yield strength R_p0.2L is a compromise between.

FIG. 4: toughness K of the alloy of example 3_appL-T and compressive yield strength Rc_p0.2L is a compromise between.

Detailed Description

Unless otherwise indicated, all indications relating to the chemical composition of the alloy are expressed as weight percentages based on the total weight of the alloy. The expression 1.4Cu means the copper content in wt. -% multiplied by 1.4. The name of The alloy conforms to The Aluminum Association (The Aluminum Association) specifications known to those skilled in The art. When the concentration is expressed in ppm (parts per million), the index value also refers to the mass concentration.

Unless otherwise stated, the metallurgical state definitions given in the European standard EN 515(1993) apply.

Tensile static mechanical characteristics, in other words, ultimate tensile strength R_mConventional yield strength R at 0.2% elongation_p0.2And elongation at break A%, determined by tensile testing according to standard NF EN ISO 6892-1(2016), the sampling and testing directions being defined according to standard EN 485 (2016). R_p0.2(L) means R measured in the longitudinal direction_p0.2。

Compressive yield strength Rc_p0.2Measured at 0.2% compression according to standard ASTM E9-09 (2018). Rc (Rc)_p0.2(L) means Rc measured in the longitudinal direction_p0.2。

Stress intensity factor (K)_1C) Measured according to standard ASTM E399 (2012).

Stress intensity factor (K)_Q) Measured according to standard ASTM E399 (2012). Standard ASTM E399 (2012) provides for the determination of K_QWhether or not it is K_1CA criterion of valid values of (a). K obtained for different materials for a given specimen geometry_QThe values are comparable to each other, provided that the yield strengths of the materials are of the same order of magnitude.

Unless otherwise stated, the definition of the standard EN 12258(2012) applies.

Apparent stress intensity factor at break (K)_app) Andstress intensity factor at break (K)_c) The values of (A) are as defined in the standard ASTM E561.

A curve of the effective stress intensity factor as a function of the effective crack extension, called the R-curve, is given, measured according to the standard ASTM E561 (ASTM E561-10-2).

Calculating the critical stress intensity factor K from the R curve_CI.e. the strength factor that destabilizes the crack. Further, the stress intensity factor K is calculated by assigning the initial crack length at the start of the single load to the critical load_CO. These two values are calculated for a sample having the desired shape. K_appRepresenting the factor K corresponding to the sample used for the R-curve test_CO。K_effRepresenting the factor K corresponding to the sample used for the R-curve test_C。

Such mechanical parts, whose static and/or dynamic mechanical properties are particularly important for the performance of the structure and which usually require or undergo structural calculations, are referred to herein as "structural elements" or "structural elements" of the mechanical construction. These are typically elements whose failure may compromise the security of the construction, its user, the consumer or others. In the case of aircraft, these structural elements include, in particular, the elements constituting the fuselage (for example fuselage skins, english fuselage skins), stiffeners or stiffeners (stringings) of the fuselage, watertight bulkheads (bulkheads), circumferential frames (circular frames) of the fuselage, wings (for example upper or lower wing skins), stiffeners (strikers or stiffeners), stiffeners) and spars (spars) and empennages, in particular consisting of horizontal and vertical stabilizers, as well as floor beams (floor rails), seat tracks (seat tracks) and doors.

According to the invention, a selected class of aluminium alloys containing in particular specific and critical amounts of lithium, copper, magnesium, silver, manganese and zinc allows the production of structural elements, in particular upper wing skin panels, having a high compressive yield strength Rcp_0.2(L), compressive yield Strength Rcp_0.2(L) and tensile yield strength Rp_0.2(L) is smaller than the difference between (L),and a particularly improved apparent stress intensity factor K at break_app. The alloy composition chosen according to the invention also allows all or part of the above advantages to be obtained over a wide tempering time range, in particular over a range of at least 5 hours at a given tempering temperature. This composition therefore allows ensuring the robustness of the manufacturing process and therefore the final properties of the product during industrial manufacturing.

The aluminum alloy-based product of the present invention comprises: 4.0 to 4.6 wt.% Cu, in weight percent; 0.7 to 1.2 wt% Li; 0.5 to 0.65 wt.% Mg; 0.10 to 0.20 wt.% Zr; 0.15 to 0.30 wt% Ag; 0.25 to 0.45 wt.% Zn; 0.05 to 0.35 wt.% Mn; up to 0.20 wt% Fe + Si; at least one element selected from the group consisting of Cr, Sc, Hf, V and Ti; the other elements are each up to 0.05% by weight and in total up to 0.15% by weight, the remainder being aluminium.

The copper content of the product of the invention is 4.0 to 4.6 wt.%, preferably 4.2 to 4.5 wt.%, and more preferably 4.2 to 4.4 wt.%. In an advantageous embodiment, the minimum copper content is 4.25% by weight.

The lithium content of the products of the invention is between 0.7 and 1.2% by weight. Advantageously, the lithium content is between 0.8 and 1.0% by weight; preferably 0.85 to 0.95 wt%.

An increase in the copper content and to a lesser extent the lithium content contributes to an improvement in the static mechanical strength, however, copper has an adverse effect on the density in particular, the copper content preferably being limited to a preferred maximum of 4.4% by weight. An increase in the lithium content has a favourable effect on the density, however the inventors have observed that for the alloy of the invention a preferred lithium content of 0.85 to 0.95 wt% allows to improve the compromise between mechanical strength (tensile and compressive yield strength) and toughness. A high lithium content, in particular above the preferred maximum value of 0.95 wt.%, can lead to a reduction in toughness.

The magnesium content of the product of the invention is between 0.5 and 0.65% by weight. Preferably, the magnesium content is at least 0.50 wt% or even at least 0.55 wt%, which improves both static mechanical strength and toughness. In particular, for the compositions selected according to the invention, a magnesium content of more than 0.65% by weight can lead to a reduction in the toughness.

The zinc and silver contents are 0.25 to 0.45 wt% and 0.15 to 0.30 wt%, respectively. These zinc and silver contents are necessary to ensure that the value of compressive yield strength is close to that of tensile yield strength. In an advantageous embodiment, the tensile yield strength Rp of the product of the invention_0.2(L) and compressive yield Strength Rcp_0.2The difference between (L) is less than or equal to 10MPa, preferably less than or equal to 5 MPa.

The presence of silver and zinc allows a good compromise to be obtained between the various desired properties. In particular, the presence of silver allows to obtain products in a reliable and robust way, i.e. to achieve the required compromise of properties over a wide range of tempering times, in particular over a time range of more than 5 hours, which is compatible with the variability inherent to industrial manufacturing processes. A minimum silver content of 0.20% by weight is advantageous. A maximum silver content of 0.27% by weight is advantageous.

A minimum content of zinc of 0.30% by weight is advantageous. Advantageously, the maximum zinc content is 0.40% by weight. Preferably, the Zn content is 0.30 to 0.40 wt%.

Advantageously, the sum of the Zn, Mg and Ag contents is between 0.95 and 1.35 wt%, preferably between 1.00 and 1.30 wt%, still more preferably between 1.15 and 1.25 wt%. The inventors have observed that, especially for upper-wing skin structural elements, only specific and critical values of the sum of Zn, Mg and Ag achieve the desired optimum performance compromise.

The manganese content is 0.05 to 0.35 wt.%. Advantageously, the Mn content is between 0.10 and 0.35 wt.%. In one embodiment, the manganese content is from 0.2 to 0.35 wt.%, and preferably from 0.25 to 0.35 wt.%. In another embodiment, the manganese content is from 0.1 to 0.2 wt.%, and preferably from 0.10 to 0.20 wt.%. In particular, the addition of Mn allows to obtain high toughness. However, if the Mn content is greater than 0.35 wt%, the fatigue life may be significantly reduced.

The Zr content of the alloy is 0.10 to 0.20 weight percent. In an advantageous embodiment, the Zr content is from 0.10 to 0.15% by weight, preferably from 0.11 to 0.14% by weight.

The sum of the iron content and the silicon content is at most 0.20% by weight. Preferably, the iron and silicon content is at most 0.08 wt% each. In an advantageous embodiment of the invention, the iron and silicon content is at most 0.06% by weight and 0.04% by weight, respectively. The controlled and limited iron and silicon content contributes to an improved compromise between mechanical strength and damage tolerance.

The alloy also contains at least one element selected from the group consisting of Cr, Sc, Hf, V and Ti in an amount (if selected) to assist in controlling the grain size, 0.05 to 0.3 wt% for Cr and Sc, 0.05 to 0.5 wt% for Hf and V, and 0.01 to 0.15 wt% for Ti. In an advantageous embodiment, the addition of 0.01 to 0.15% by weight of titanium is selected. In a preferred embodiment, the Ti content is from 0.01 to 0.08 wt.%, preferably from 0.02 to 0.06 wt.%. Advantageously, in the embodiment in which titanium is chosen for addition, the content of Cr, Sc, V and Hf is limited to a maximum content of 0.05% by weight, these elements may have an adverse effect, in particular on the density, and they are added only in order to further promote the production of a substantially non-recrystallized structure (if necessary). In a particularly advantageous manner, Ti is present in particular in the form of TiC particles. Surprisingly, the inventors have observed that, in the particular case of the alloy of the invention, the presence of TiC particles in the grain refining bar during casting (AlTiC refinement) allows to obtain a product with the best compromise of properties. Advantageously, the refiner has the formula AlTi_xC_yIt also writes as AT_xC_yWherein x and y are contents in weight% of Ti and C for 1 weight% of Al, and x/y>4. In particular, AlTiC refinement of the alloy of the invention allows improving the toughness K_appL-T and compressive yield strength R_cp 0.2L.

The content of the alloying elements may be selected to minimize the density. Preferably, the additive elements contributing to the increase in density (e.g., Cu, Zn, Mn, and Ag) are minimized, and the elements contributing to the decrease in density (e.g., Li and Mg) are maximized to achieve 2.73g/cm or less³And preferably less than or equal to 2.72g/cm³The density of (c).

The content of other elements is up to 0.05% by weight each and a total of up to 0.15% by weight. The other elements are usually unavoidable impurities.

The method of manufacturing the product of the invention comprises the steps of preparation, casting, homogenization, hot deformation, solution heat treatment and quenching, stretching 2 to 16% and tempering.

In a first step, a liquid metal bath is prepared to obtain an aluminum alloy having the composition of the present invention.

The liquid metal bath is then cast into the form of a raw product, preferably in the shape of a rolled ingot or an extruded billet.

The crude product is then homogenized to reach a temperature of 450 ℃ to 550 ℃ and preferably 480 ℃ to 530 ℃ for 5 to 60 hours. The homogenization process may be performed in one or more stages.

After homogenization, the crude product is typically cooled to room temperature and then preheated for hot deformation. The hot deformation may be in particular extrusion or hot rolling. Preferably, it is a hot rolling step. The hot rolling is carried out to a preferred thickness of 8 to 50mm and in a preferred manner 15 to 40 mm.

The product thus obtained is then subjected to a solution heat treatment to a temperature of 490 to 530 ℃ for 15min to 8h, then quenched with water, usually at room temperature.

The product is then cold-deformed to a deformation ratio of 2 to 16%. It may be a controlled stretch with a permanent set of 2 to 5%, preferably 2.0 to 4.0%. In an alternative advantageous embodiment, the cold deformation is carried out in two steps: the product is first cold-rolled with a reduction in thickness of 8% to 12% and then stretched in a controlled manner with a set of 0.5 to 4%.

The product is then subjected to a tempering step by heating at a temperature of 130 to 170 ℃ and preferably 140 to 160 ℃ for 5 to 100 hours and preferably 10 to 70 hours.

The inventors have observed that, unexpectedly, the specific content and critical content of the alloy of the invention allow to achieve excellent properties, in particular the compressive yield strength Rc_p0.2(L) and plane stress toughness K_appIn particular an improved compromise between. Advantageously, these properties are obtained with the alloy of the invention, regardless of the tempering time at 155 ℃ of 15 to 25h, which ensures the robustness of the manufacturing process.

Advantageously, the granular structure of the resulting product is mainly non-recrystallized. The ratio of non-recrystallized granular structure at intermediate thickness is preferably at least 70% and preferably at least 80%.

The products obtained by the process of the invention, in particular rolled products having a thickness of 8 to 50mm, have the following characteristics at medium thicknesses:

i) compressive yield strength Rc_p0.2(L) ≥ 590MPa, preferably Rc_p0.2(L) 595MPa or more, wherein the compressive yield strength Rc_p0.2(L) measured at 0.2% compression in the longitudinal direction according to standard ASTM E9 (2018);

ii) toughness K_app(L-T) 60MPa ≥ m, preferably K_app(L-T) ≥ 75MPa m, where the value K of the apparent stress intensity factor at break is defined according to the standard ASTM E561(2015)_app(L-T) was measured on a CCT specimen having a width W of 406mm and a thickness B of 6.35 mm;

iii) tensile yield strength R_p0.2(L) and compressive yield strength Rc_p0.2The difference R between (L)_p0.2(L)-Rc_p0.2(L) is less than or equal to 10MPa, preferably less than or equal to 5 MPa.

Advantageously, the characteristics i) and ii) are obtained at a given tempering temperature within a wide range of tempering times, in particular within a range of at least 5 hours. This composition therefore allows ensuring the robustness of the manufacturing process and therefore the final properties of the product during industrial manufacturing.

In an advantageous embodiment, the toughness is such that K_app(L-T)≥-0.48Rc_p0.2(L) +355.2, where K_app(L-T), expressed in MPa √ m, as a value of the apparent stress intensity factor at break defined according to standard ASTM E561(2015), measured on a CCT specimen with a width W of 406mm and a thickness B of 6.35 mm; and Rc_p0.2(L), expressed in MPa, is the compressive yield strength measured at 0.2% compression according to the standard ASTM E9 (2018).

The alloy product of the invention allows in particular the manufacture of structural elements, in particular aircraft structural elements. In an advantageous embodiment, the preferred aircraft structural element is an aircraft upper wing skin element.

These and other aspects of the invention are explained in more detail using the following illustrative and non-limiting examples.

Examples

Example 1.

In this example, a plate made of an alloy having a composition as listed in Table 1 and having a cross section of 406X 1520mm was cast.

TABLE 1 composition of alloys N DEG 1 to 8 in% by weight

Alloy (I)	Si	Fe	Cu	Mn	Mg	Zn	Ti	Zr	Li	Ag
											1	0.02	0.03	4.6	0.32	0.62	0.62	0.03	0.13	0.91	0.01
2	0.02	0.03	4.3	0.31	0.60	0.35	0.03	0.12	0.91	0.24
											3	0.03	0.05	4.5	0.34	0.71	0.04	0.04	0.11	1.03	0.21
4	0.03	0.04	4.3	-	0.33	0.03	0.02	0.15	1.13	0.21
											5	0.03	0.04	4.2	0.33	0.54	-	0.03	0.13	0.88	0.19
6	0.02	0.04	4.4	0.02	0.21	0.04	0.02	0.14	1.05	0.21
											7	0.03	0.04	3.9	-	0.36	-	0.03	0.11	1.31	0.36
8	0.04	0.06	4.1	0.42	0.42	0.02	0.02	0.15	1.18	0.29

For each composition, the plates were subjected to a first stage homogenization at 500 ℃ for 15h, followed by a second stage homogenization at 510 ℃ for 20 h. The plate is hot-rolled at a temperature higher than 440 ℃ to obtain a sheet with a thickness of 25mm for alloys 2 to 8 and a sheet with a thickness of 28mm for alloy 1. The sheet was solution heat treated at about 510 ℃ for 3h and water quenched at 20 ℃. The sheet is then stretched at a permanent elongation of 2% to 6%.

The sheet was subjected to a single stage tempering as shown in table 2. Samples were taken at medium thickness to measure the static mechanical characteristics in the longitudinal direction under tension and compression. In-plane stress toughness at intermediate thicknesses in the L-T direction was also measured during R-curve testing using 406mm wide and 6.35mm thick CCT specimens. The results are shown in Table 2 and FIG. 1.

The structure of the resulting sheet is largely non-recrystallized. The proportion of non-recrystallized granular structure at medium thickness is 90%.

Table 2 controlled stretching and tempering conditions at medium thickness of each sheet and the mechanical properties obtained.

Example 2

In this example, in addition to the alloy sheet 2 of example 1, a sheet having a cross section of 406 × 1520mm was cast, the composition of which is given in table 3.

Table 3, compositions of alloys 2 and 10, in weight%,

alloy (I)	Si	Fe	Cu	Mn	Mg	Zn	Ti	Zr	Li	Ag
												2	0.02	0.03	4.3	0.31	0.60	0.35	0.03	0.12	0.91	0.24
10	0.04	0.02	4.3	0.31	0.64	0.33	0.03	0.14	0.90	0.35

The plates were homogenized at about 510 ℃ and then peeled. After homogenization, the plate was hot-rolled to obtain a sheet with a thickness of 25 mm. The sheet was solution heat treated at about 510 ℃ for 3 hours, quenched in cold water, and stretched at a permanent elongation of 3%.

The structure of the resulting sheet is mainly non-recrystallized. The proportion of non-recrystallized granular structure at medium thickness is 90%.

The sheet is tempered at 155 ℃ for 15 to 50 hours. Sampling at medium thickness to measure static mechanical characteristics under tension, compression in longitudinal directionAnd toughness K in the L-T direction_Q. The width W of the test piece used for the toughness measurement was 40mm and the thickness B was 20 mm. The results are shown in table 4 and fig. 2 and 3.

Table 4: the tempering conditions of the sheets 2 and 10 and the mechanical properties obtained.

Example 3

In this example, in addition to the sheet of alloy 2 of example 1, a sheet with a cross section of 406 x 1700mm was cast using AlTiC refinement (grain refining rods containing TiC type nuclei), the composition of which is shown in Table 3.

Table 5 composition of alloys 2 and 9 in weight%.

Alloy (I)	Si	Fe	Cu	Mn	Mg	Zn	Ti	Zr	Li	Ag
												2	0.02	0.03	4.3	0.31	0.60	0.35	0.03	0.12	0.91	0.24
9	0.02	0.04	4.3	0.14	0.61	0.36	0.05	0.13	0.88	0.25

The plates were homogenized at about 510 ℃ and then peeled. After homogenization, the plate was hot-rolled to obtain a sheet with a thickness of 25 mm. The sheet was solution heat treated at about 510 ℃ for 3h, quenched in cold water, and stretched at 3% permanent elongation.

The sheet is tempered at 155 ℃ for 15 to 25 hours. Samples were taken at medium thickness to measure static mechanical characteristics under tension, compression in the longitudinal direction and toughness, K, in the L-T direction_Q. The width W of the test piece used for the toughness measurement was 40mm and the thickness B was 20 mm. Some samplesThe product conforms to K_1CThe validity criterion of (2). Measurements of in-plane stress toughness were also obtained on CCT samples 406mm wide and 6.35 thick. The results are shown in Table 6 and FIG. 4.

Table 6: tempering conditions of the sheets 2 and 9 and mechanical properties obtained at medium thickness

Claims (12)

1. An aluminum alloy-based product, comprising: in terms of weight percentage, the weight percentage of the active carbon is,

4.0 to 4.6 wt.% Cu,

0.7 to 1.2 wt.% of Li

0.5 to 0.65 wt.% Mg,

0.10 to 0.20 wt.% Zr,

0.15 to 0.30 wt% Ag,

0.25 to 0.45 wt.% Zn,

0.05 to 0.35 wt.% Mn,

up to 0.20 wt.% Fe + Si,

at least one element selected from the group consisting of Cr, Sc, Hf, V and Ti, if selected, in an amount of 0.05 to 0.3 wt% for Cr and Sc, 0.05 to 0.5 wt% for Hf and V, 0.01 to 0.15 wt% for Ti,

the other elements are each up to 0.05% by weight and in total up to 0.15% by weight, the remainder being aluminium.

2. The aluminum alloy-based product of claim 1, wherein the Cu content is 4.2 to 4.5 wt.%, preferably 4.2 to 4.4 wt.%.

3. The aluminium alloy-based product according to claim 1 or 2, wherein the Li content is 0.8 to 1.0 wt. -%, preferably 0.85 to 0.95 wt. -%.

4. The aluminum alloy-based product of any of claims 1-3, wherein the Zn content is 0.30 to 0.40 wt.%.

5. The aluminum alloy-based product of any of claims 1-4, wherein the Mn content is 0.10 to 0.35 wt.%.

6. The aluminum alloy-based product of any of claims 1 to 5, wherein the sum of the Zn, Mg, and Ag contents is from 0.95 to 1.35 wt.%, preferably from 1.00 to 1.30 wt.%, more preferably from 1.15 to 1.25 wt.%.

7. The aluminum alloy-based product of any of claims 1 to 6, wherein the Zr content is 0.10 to 0.15 wt.%, preferably 0.11 to 0.14 wt.%.

8. The aluminum alloy-based product of any of claims 1 to 7, wherein the Ti content is 0.01 to 0.15 wt.% Ti, preferably 0.01 to 0.08 wt.%, more preferably 0.02 to 0.06 wt.%.

9. The aluminium alloy-based product according to claim 8, wherein Ti is present in particular in the form of TiC particles.

10. A method of manufacturing an aluminium alloy based product, wherein, in sequence,

b) preparing an aluminum-based liquid metal bath comprising: 4.0 to 4.6 wt.% Cu; 0.7 to 1.2 wt% Li; 0.5 to 0.65 wt.% Mg; 0.10 to 0.20 wt.% Zr; 0.15 to 0.30 wt% Ag; 0.25 to 0.45 wt.% Zn; 0.05 to 0.35 wt.% Mn; up to 0.20 wt% Fe + Si; at least one element selected from the group consisting of Cr, Sc, Hf, V and Ti, if selected, in an amount of 0.05 to 0.3 wt% for Cr and Sc, 0.05 to 0.5 wt% for Hf and V, 0.01 to 0.15 wt% for Ti; each of the other elements is up to 0.05 wt% and the total amount is up to 0.15 wt%, the remainder being aluminum;

b) casting a green article from the liquid metal bath;

c) homogenizing the crude product at a temperature of 450 ℃ to 550 ℃ and preferably 480 ℃ to 530 ℃ for 5 to 60 hours;

d) hot deforming, preferably by rolling, the homogenized raw product;

e) solution heat treating the hot deformed product at 490 to 530 ℃ for 15min to 8h and quenching the solution heat treated product;

f) cold-deforming the product with a deformation rate of 2 to 16%;

g) tempering is carried out, wherein the product is brought to a temperature of 130 to 170 ℃ and preferably 140 to 160 ℃ for 5 to 100 hours and preferably 10 to 70 hours.

11. The product according to any one of claims 1 to 9 or obtainable by the process of claim 10, having a thickness of from 8 to 50mm, at medium thickness:

i) compressive yield strength Rc_p0.2(L) ≥ 590MPa, preferably Rc_p0.2(L)≥595MPa；

ii) toughness K_app(L-T) 60MPa ≥ m, preferably K_app(L-T) 75MPa or more, wherein K is_app(L-T) is the value of the apparent stress intensity factor at break defined according to standard ASTM E561(2015), measured on CCT specimens with a width W of 406mm and a thickness B of 6.35 mm;

iii) tensile yield strength R_p0.2(L) and compressive yield strength Rc_p0.2The difference R between (L)_p0.2(L)-Rc_p0.2(L) is less than or equal to 10MPa, preferably less than or equal to 5 MPa.

12. An aircraft structural element, preferably an aircraft upper wing skin element, comprising a product according to any of claims 1 to 9 or according to claim 11.

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