MXPA96003280A - Aluminum-li alloy thermal treatment - Google Patents

Abstract

The present invention relates to a method of heat treatment of an aluminum-lithium alloy characterized in that it comprises carrying out a succession of at least two stages of artificial aging, said treated alloy having a resistance to yield point less than 70 ksi, being the first stage carried out within a first temperature scale of 165§C to 130§C, and being a second stage carried out within a reduced temperature scale of 130§C to 90

Description

ALUMINUM-LITHIUM ALLOY THERMAL TREATMENT The present invention relates to the heat treatment of aluminum-lithium alloys, and in particular to such thermal treatment for the reinforcement of said alloys and for the optimization of the resistance to the fracture stress of the surface of the alloys. Such alloys are known in particular for use in aircraft coating constructions, and more particularly for the construction of tail and wings, and commercial aircraft fuselage. In this particular application, the low density, high rigidity and excellent fatigue properties of aluminum-lithium alloys make it possible to reduce the weight that is achieved to maximize the profitability of the aircraft. The prior art references that are relevant to this invention, known at the time of the invention, are as follows. "Effect of Thermal exposure at 70 C on the performance of damage tolerance aluminum- lithium alloy sheet" (Effect of thermal exposure to 70"C in the development of damage tolerant lithium aluminum alloy sheet.) February 1995.

Reference DRA / S C / P952008 by D.S. McDarmaid; "Mechanical properties of 2024-T3 aluminum allowy sheet" (Mechanical properties of sheets of aluminum alloy 2024 -T3). December 1991. Reference TR91071 by D.S. McDarmaid, CE. Thomas and C. Wheeler.

Aluminum-lithium alloys (AL-LI) registered with the ALUMINUM ASSOCIATION as AA8090 and AA2091 (hereinafter referred to without the prefix "AA") in the form of recrystallized and tempered sheets under aging have been shown to have attributes of "Tolerance to Damage ", in which fatigue cracking growth rates are commendably slow, coupled with reasonably high levels of resistance to surface fracture force (Kc). As such, both products have been extensively investigated as potential alternatives to materials currently widely used for civil aviation coating applications, in particular for airframes, such as aleator 2024 T3 and 2014A T4, where the reduction of density associated with lithium alloys, would allow the saving of considerable amounts of weight. The plate-shaped 8090 has also been investigated for top and bottom wing and glue applications, and can also be considered for top wing coatings. In addition to the requirement for damage tolerance, there are several other necessary features that any new cladding material and particularly the glue and wing cladding materials must possess. This includes adequate strength, good resistance to corrosion and a frequent, not established, but very important long-term thermal stability requirement, ie the possibility of resisting prolonged periods at moderately elevated temperatures without appreciable or unacceptable loss in any of the key attributes. For a subsonic civil aviation fuselage, the worst case of considering thermal instability, involves territorial exposure to the combined effects of high environmental temperature and intense solar radiation. It is generally accepted that in fuselage coating temperatures in tropical conditions of up to 70-80 ° C, it can be achieved when the sun is at or near your Zenit. In the life of an airplane, this can, in the worst case, represent a cumulative exposure to high temperatures of approximately 65,000 hours (for example 6 hours per day for thirty years), although such exposure would only be achieved by aircraft either stored in desert conditions, or irregularly operated from tropical bases. Thermal stability is also an aspect of interest when considering the use of lithium aluminum alloys, for tail and wing coating applications. The alloys 8090 and 2091, have been primarily investigated for fuselage coating applications under conditions T81 and T84 respectively. Condition T81 for 8090 is achieved by hardening by artificial aging (aging) of condition T31 (ie treated and controlled exaggerated solution) for 24 hours at 150 C, while condition T84 for 2091 is achieved by aging of condition T3 for 12 hours at 135 C followed by a jump from room temperature to 135 C. These treatments are tried to produce products to mimic the mechanical properties of alelad 2024 T3 (ie the lower limit for the Test Resistance 0.2% "that has been established as approximately 270 MPa) so that substitution applications can be more easily considered. There is also the general perception that "aluminum alloys require a static resistance of at least equivalent to the aleator 2024 T3 to be successful in fuselage coating applications. This is not necessarily so, since the increase in the Young's Module associated with the lithium content is also capable of compensating for any slight reduction in strength that could now be seen as required in order to properly satisfy a real requirement for very high resistance to fractures and for good impact resistance. Despite the use of the artificial aging treatment, both aluminum products, referred to as they are known, lack thermal stability on the 70-85 C temperature scale and an increase in resistance combined with a disproportionately large reduction in the results. Kc, after the relatively short isothermal exposure (ie, a very significant effect after 1000 hours). This inverse relationship between the resistance and Kc for alloys aluminum-lithium, has been demonstrated on many occasions. Since the initial strength levels for both alloys aged for their respective prior art conditions (ie T81 and T84 for 8090 and 2091, respectively) are marginal for the intended application when compared to the aleator 2024 T3 (the current standard in the industries), this absence of thermal stability and pernicious effect on the resistance of any apparently very small increase in resistance, is widely considered as a major contributing factor that accounts for the current lack of any significant application of civil air fuselages. The cause of the thermal instability is attributed to a continuous precipitation of (Al3Li) of d '. The reason for the continuous precipitation of d1, and consequently the thermal instability, is that there is an inverse relationship between the equilibrium volume fraction of d 'and the temperature (that is, the equilibrium volume fraction increases while the temperature is reduced). The high diffusion rate of lithium in aluminum ensures that the formation of d 'is not an effectively controlled diffusion rate until the temperature drops considerably below the exposure temperature of interest. Therefore this is followed although extensive aging at aging temperatures of the prior art established (ie, 135- 150 C), will never achieve any approach to a complete precipitation of d ', and a high thermodynamic conduction force for continuous precipitation, coupled with adequate lithium diffusion rates, will exist at temperatures at or near (lower) than the maximum temperatures of thermal exposure considered. Instead, extensive aging at these higher temperatures will only serve to increase the volume fraction of other phases such as S '(AlCuMg) leaving a structure too high in strength but relatively low in d'. Subsequent long-term thermal exposure, therefore results in a large increase in the volume fraction of d1, an increase in strength and brittleness. To illustrate the effect of duplicate samples of continuous precipitation of d 'from a batch of (hereinafter referred to as "Lot 1" material) 8090 T81 were given a scale of thermal treatments prior to being exposed to an elevated temperature by a considerable length of time. The composition in percentage weight of the material of Lot 1, was: Li Cu Mg Fe Zr Al 2.23 1.14 0.79 0.045 0.06 Remaining The treatments chosen include a "reversion" of 10 minutes at 200 C of condition T81 (ie, causing a drop in the Test Resistance of 0.2% due to the dissolution of d '), followed by a re-aging of 170 ° C for 4 hours, ie to ensure a recovery of approximately the original level of the Test Resistance of 0.2% of T81 and, finally, a prolonged over-aging treatment of 220 ° C for 12 hours, in addition to the initial treatment of T81. After testing the tension in the cross-sectional lengthwise sample (LT), representative of each condition of the duplicate samples of all conditions that include the "Control" condition of T81, they were then exposed for 920 hours at 100'C , in order to crudely represent an exhibition of useful life at tropical temperatures. The results of the mechanical properties tests and the electrical conductivity measurements made are shown in Table l. It is clear from Table 1 that "the precipitation continues at 100" C results in a considerable increase in resistance.The reverted material recovers a higher resistance than is the case for the Control condition, which indicates the ineffectiveness of the reversal as a means to increase the resistance of 8090, where consideration must also be made of the effects of thermal instability, since the initial benefit of reversal is of short duration and the treatment can finally be expected to be harmful as the result in a higher final resistance after thermal exposure. The increase in the resistance of the material reversed on and above a non-reversed material at the conclusion of the thermal exposure is attributed to the additional precipitate S 'during the reversal process. Similarly, the additional increase in re-aged and reverted material strength followed by thermal exposure compared to any of the T81 and T84 plus reversal conditions, is attributed to the increased S ', associated with 4 hours at 170 C. Finally, the use of over-aging is seen to be completely ineffective in achieving stability with an elevation of 48 MPa in the 0.2% Test Resistance that is apparent at the conclusion of the 920 exposure hours. Similar results for all starting conditions would be anticipated by exposure to, say, 70 C and although a higher equilibrium volume fraction of d 'would be feasible at this temperature than at 100"C, although the exposure time required for to achieve saturation would be that much higher at the lower temperature due to the reduced diffusion rates It will be noted that sheet 8090 of Lot 1 had a Test Resistance of 0.2% T81 LT of 293 MPa and which then reached what it is believed to be the Test Resistance 0.2% saturated d1 of 320MPa following 920 hours of thermal exposure at 100"C, that is, an increase of 27MPa In accordance with the invention, an improved method of heat treatment of aluminum-lithium alloys, includes carrying out a succession of at least two stages of artificial aging, the first of such stages being carried out within a first temperature scale and at least one additional stage being carried out within a scale of successively reduced temperatures. the precipitation d * is thus achieved and for appropriately selected temperature scales of the volume fraction S 'is achieved in conjunction with this to achieve a condition of suitable use, but not excessive initial resistance that is compatible with the requirement of high Resistance to fracture, with the ability to retain adequate resistance to fracture following long-term exposure to temperature moderately elevated. Where other appropriate temperature scales are selected according to the present invention, it is possible to combine the promotion of dt precipitation with high levels of volume fraction S1, with which resulting in a level of resistance that is higher than any that it would be possible for an alloy of this composition for a given total aging treatment time. The conclusion reached was that the thermal stability a, said, 70-85 C, can only be achieved by performing an equilibrium volume fraction of d 'for this temperature. The achievement of saturation of d 'needs to be achieved without setting too high a 0.2% Test Resistance level that would otherwise be incompatible with the omnipresent requirement for high fracture resistance. Aging tests according to the present invention were then conducted using a starting condition material 8090 T31, which was reached by treatment by resolution and exaggerated control of some material 8090 T81 of Lot 1. The NB resolution treatment was carried out at 505 C to prevent grain growth. The aging process started at 150 ° C, but for a short duration (much less than 24 hours of the previous art, at 150 ° C), followed by progressive reductions in temperature and increases in aging time, so that The fraction of the volume of S 'and the different phases of d' can be covered and a high volume fraction of d 'can be verified In this way, it is now believed that a condition with a higher balance between the fractions of precipitated volumes of dy S ', and the precipitate size distribution can be achieved with a relatively low level of 0.2% Test Resistance (and, consequently, a high resistance to the fracture) and with limited capacity to resist further by the continuous precipitation of do The adoption of this form of gradually retrogressive aging treatment (RS-W) according to the invention, fully recognizes the need to precipitate enough S 'to prevent the that otherwise it would be a mechanism of plastic deformation called by the intense flat sliding deformation mechanism which, if not properly inhibited by the presence of S ', would then result in low levels of ductility, particularly in the longitudinal direction. During this initial work with Lot 1 material treated by resolution, a large number of combinations of aging RS-W temperature / time were studied. Of particular note were the treatments based around an aging sequence RS-W of 4 stages, starting with either 1 hour or 3 hours at 150"C followed by periods at 135 C, 120" C and 100'C as shown later: 1 hour / 150 + 6/135 + 3/120 + 50 / 100'C (See table 2A) 1 hour / 150 + 6/135 + 8/120 + 50 / 100'C (See table 2B) 1 hour / 150 + 6/135 + 16/120 + 50 / 100'C (See table 2C) 1 hour / 150 + 12/135 + 6/120 + 50/100 C (See table 2D) 1 hour / 150 + 12/135 + 16/120 + 50 / 100'C (See table 2E) 3 hours / 150 + 12/135 + 6/120 + 50/100 ° C (See table 2F) 3 hours / 150 + 6/135 + 16/120 + 50/100 ° C (See table 2G) These treatments and the resulting mechanical properties and electrical conductivity results, both during the aging sequence and as a result of several periods of thermal exposure at 85 C and 70 ° C, are shown in Tables 2A-2G. Subsequently, a new batch of sheet 8090 was obtained (hereinafter referred to as "Batch 2"), which had not previously been treated by a hot solution. This material was used for thermal treatment of the solution and aging tests in order to optimize the RS-W aging process. The composition in percent weight of the sheet material of "Lot 2", was: Li Cu Mg Fe Zr Al 2.26 1.21 0.69 0.047 0.66 Remaining From the results of the trials of the "Lot 1", it is noted that the 135" C stage was apparently resulting in excessive aging of the non d 'phases, and thus could be discontinued. It was also recognized that if the fuselage structure were to be adhesively bonded (ie, the junction of the reinforcement to the coating) then any one of a resin system that cures at 150 C or one at 120 C, such as REDUX (registered trademark), 775 (CIBA) or AF163-2 (3M), or similar, would be more likely to be used. In the case of REDUX 775 (cure at 15OC), the cure cycle can be combined with the RS-W aging stage at 150 ° C, and all subsequent stages would then be applied to the reinforcement / bonded joint assembly. In which case there would be an economic advantage in reducing the temperature of the second stage, such that the assembly would not receive an overpressure to protect the adhesive (phenolic). This would be achieved by reducing the temperature of the second stage from 135'C to 125-120C, with which the continuous use of an aging stage of 135 C would require this aging step to take place in an autoclave or a press of Union. If a 120 C cure resin system, such as AF163-2 were to be used, then the cure cycle can be introduced after completing all stages of aging of more than 120 C. No pressure would be required for any of the selected aging temperatures equal to or less than 120 C. A series of aging tests of RS-W was attempted using the material of "Lot 2", which has been treated by solution at 530 C, and exaggerated control of 1.75% ± 0.25d. Remarkable are the following RS-W treatments:1 hour / 150 + 6/135 + 8/120 + 50 / 120'C (Included in the material of Lot 2 of benchmark with Lot 1) (See Table 3A) 1 hour / 150 + 8/120 + 24/105 + 24 / 95'C (See Table 3B) 1 hour / 150 + 16/120 + 24/105 + 24 / 95'C (See Table 3C) 1 hour / 150 + 8/125 + 24/105 + 24 / 95C (See 3D Chart) 1 hour / 150 + 16/125 + 24/105 + 24 / 95'C (See Table 3E) 1 hour / 135 + 8/120 + 24/105 + 24 / 95'C (See Table 3F ) lhora / 135 + 16/120 + 24/105 + 24 / 95'C (See Table 3G) 2 hours / 120 + 32/105 + 24 / 95'C (See Table 3H) 8 hours / 120 + 24/105 + 24/95 C (See Table 3J) These tests showed that the 135 C stage was superfluous and that a direct transition from about 150 C to about 120 ° C (or 125 ° C) was preferable. The treatments started at 135'C to 120C, having some merits but produced a full thermal treatment condition that was lower in resistance, but finally, on thermal exposure, amounted to levels comparable with the treatments that started at 150 C, and thus it was expected not to be beneficial in terms of usable resistance. On the basis of the stress test data from the previous tests, the sequence 1 hour / 150 C + 8/120 C + 24/105 C + 24/95 C was selected for further investigation and refinement. This included Life-size aging sheets to enable the fracture resistance tests of the panel that is carried out. The result of the first test of resistance to fracture carried out in the material of "Lot 2" of thickness of 1.9mm, aged 1 hour / l50 ° C + 8 / l20"C + 24 / l05" C + 24 / 95'C, is shown in Figure 1 in the form of a curve of fracture resistance (Curve-R). The result was compared to the R-curves applicable to 8090 T81 and 8090 T81 of the prior art (Reference 1), a condition previously shown to produce improvements in strength together with alelad 2024 T3 (Reference 2). It can be seen that the application of the RS-W treatment of the invention, has produced a condition of very high resistances and that it is comparable to or better than the aleator 2024 T3. This is the first reported knowledge of the occurrence of sheet 8090, which exceeds the resistance of alelad 2024 T3. A second 8090 sheet of 1.9mm thickness was given to the previous RS-W treatment, followed by 2000 hours of thermal exposure between 70 C and 75'C. The R-curve for this material is shown in Figure 2 together with an unexposed R-curve. Also shown is an R-curve for 8090 T81 material from the prior art with and without 2000 hours of thermal exposure at 70"C (Reference 1). It can be seen "that although the RS-W material has suffered a reduction in strength, the reduction (approximately 6%) is much lower and of a much higher starting level than was the case for the prior art 8090 T81.

NB: The comparative data extracted in graphic form from the References 1 and 2 are presented for illustrative purposes only and are not intended to limit the invention. The tests were also conducted to determine the sensitivity to the variations of time and temperature for the first stage of aging and to determine if the final stage of 24 hours / 95 ° C can be usefully truncated. The results of these tests are shown in Tables 4A, 4B and 4C for the material in Lot 2. It was established that the first stage can be reduced to 0.75 hours or extended to 1.25 hours without being apparent the undue harmful effects. It was also found that the final stage can be truncated to 8 hours for material giving 1 hour / 150 ° C or 1.25 hours / 150 ° C without a significant effect on the final resistance and, for applications where the resistance is not critical, this stage can be omitted complementamente and / or adopart the treatment of aging of 150 ° C shortened. The preferred aging treatment identified as a result of this work is: 1 hour / l50 ° C + 8 / l20 ° C + 24 / l05 ° C + 8/95 ° C The four stage treatment has the advantage of maximizing the degree of beneficial resistance (ie, reinforcement due to precipitation of d ') without requiring a too long aging treatment "that could be non-economic. It was found that the treatment is reasonably insensitive to aging temperatures within the ± 5 ° C scale (all stages) and to variations in the length of individual treatments within the ± 25% scale of the established time. It was also found that this preferred aging treatment generates the optimum strength for intergranular corrosion as measured by the ASTM GllO corrosion test with the penetration depth of the corrosion limited to approximately 150wm and with a tendency to form localized corrosion cavities with very little or virtually no intergranular attack present. This is a very marked contrast for 8090 T81 which frequently exhibits in excess of 250-300 μm-attack and which is characterized by an extended network of intergranular penetration. The intergranular attack forms for the RS-W and T81 conditions are shown in Figures 3 and 4 respectively. Several more life-size leaves were then devoted to the preferred aging treatment of 1 hour / l50 ° C + 8 / l20 ° C + 24/105 ° C + 8/95 ° C. These sheets were intended to establish the initial resistance level for 1.6 mm sheets and to provide specimens for long-term thermal exposure, such that it can be determined the R curves of the thermally sensitized material. The results of a test of the R curve on this material in the fully heat-treated condition are shown in Figure 5. The R curve is slightly less than for the 1.9mm material and the difference is considered to be due to the plan lamination associated with the 1.6mm caliber, differences in lithium depletion, or a resistance effect per se, or a combination of these effects. One sheet of Lot 2 material sufficient for a large number of stress tests has been given to the preferred aging treatment and a 2000-hour thermal exposure test at 70 ° C has been completed, together with the comparative Lot 2 material, Initially aged to the condition of T81. The results are shown in Table 5 and are represented as the 0.2% Test Resistance versus the Log10 Exposure Time in Figure 6. It is apparent from Figure 6 that the T81 material has been subjected to an incubation period of approximately at the 100-hour exposure point somewhere, slightly in excess of the 100-hour exposure point during which it was apparent that virtually no 0.2% Test Resistance was changed. There was then a rapid increase in the 0.2% Test Resistance. In contrast, the material aged by RS-W exhibited no such effect of incubation and a fixed elevation was evidenced in the Test Resistance of 0. 2% versus the Logarithmic Exposure Time. It should be noted that the gradient of the two curves (excluding the incubation period for T81) seems almost identical, indicating that "the" advantage "of the lower resistance in the Material RS-W is being maintained and extrapolated to the point of 65,000 hours suggested that the T81 material would eventually age at a 0.2% Test Resistance of approximately 349 MPa considering that the RS-W material would not exceed approximately 318 MPa. This represents an improvement in terms of preventing an increase in strength of approximately 31 MPa that would otherwise occur. However, this end predicts the 0.2% Test Resistance level for the RS-W material of Block 2 to be considered as approximately 25-30 MPa above a value considered compatible with a goal of equalizing strength to strength. of fracture of the surface of the alcald 2024 T3. To achieve a further reduction in the 0.2% saturated Test Strength level of d ', a compositional adjustment that is made in combination with the RS-W treatment may be required. It is believed that for the 8090 alloy the magnesium level should be reduced from the level of 0.69% present in Lot 2 to substantially the minimum level in the compositional register (ie 0.6%), or the same to lower this value as low as substantially 0.4%. This will also restrict the reinforcement attributed to the precipitation of S and it will increase the limit of solubility of lithium in aluminum, thereby restricting the degree of precipitation of d '. Similarly, the lithium level may also need to be maintained at or level below the minimum composition of 8090 (ie 2.2%). Reducing copper levels can be counterproductive in terms of resistance and thus, dilution below the level of Lot 2 may be undesirable. To further illustrate the benefit of reducing the aging temperature according to the invention, in order to increase the volume fraction of the d 'precipitate, some recrystallized 8090 T31 sheet was aged for 24 hours at 170 ° C in order to reach a condition of medium resistance, and then subsequently aged for 8 hours at 120 ° C. The longitudinal tension properties after aging for 24 hours at 170 ° C according to the prior art are shown below together with the properties after the subsequent 8 hour period of aging at 120 ° C according to the present invention. It can be seen that a significant increase in the resistance results from the inclusion of a relatively short aging stage at a lower temperature, and that the final resistance level reached is significantly higher than that which would have resulted from, said, hours (ie 24 + 8 hours) at 170 ° C.

Resistance Resistance Treatment% Elongation Aging 0.2% stress test (MPa) (MPa) 24 hrs at 170 ° C 374 468 24 hrs at 170 ° C 406 499 8 hrs at 120 ° C The aging concept of RS-W according to the invention combines an aging stage of the prior art with an additional aging stage or stages at reduced temperatures for the initial aging stage to achieve a medium to high resistance condition, which could therefore be seen to be advantageous in terms of maximizing the resistance that can finally be achieved, as well as achieving a given level of resistance in a short total aging time that would otherwise be possible. This type of process is applicable to all alloys of Al-Li strengthened in part by the precipitation of d 'and is applicable to all forms of products such as plates, extrusions, forgings, tubes, etc. This particular form of the aging treatment according to the present invention is now called Gradually Highly Retrogressive Aging ("HSRS-W).

SCALE OF THERMAL TREATMENTS The nature of the thermal treatment according to the RS-W aspect of the invention is such that there is a wide range of treatments that roughly achieve the same final condition. A very broad scale of RS-W treatment intended to produce a condition of high strength to the fracture force of the surface is therefore described and then several refinements culminating in a preferred scale (Scale 4 of RS-W) that It is particularly suitable for the 8090 alloy and which achieves an optimal combination of initial strength, stiffness and thermal stability is disclosed. The HSRS-W aging treatment according to the invention combines the process of maximizing the volume fraction of d 'with an aging treatment intended to produce a medium to high resistance condition (ie, high in S' and d). ') to result in an increased resistance level that greater than what would result from the aging treatment of only the prior art or of an isothermal aging treatment over the entire length that is only carried out at the highest temperatures. For "short" aging stages (ie, less than or equal to 3 hours substantially) the indicated time may begin when the temperature of the product as determined by a contact-based temperature measuring device (thermocouple) reaches a temperature within 5 ° C of the nominal treatment temperature. Typically, for an aging stage of 150 ° C applied to a sheet of 1.6mm thick and with the sheets loaded inside a preheated air circulation oven, a reheating time of 10 to 15 minutes has been found to be appropriate. For aging times greater than about 3 hours the delay between the oven and metal air temperatures can be ignored, and the treatment time then begins when the oven air temperature returns to the set temperature. For several short aging treatments the use of an oil bath or the like may be necessary instead of an air oven. In such cases, appropriate adjustments to the metal's overheating will be needed. Treatments below 90 ° C are considered ineffective, according to the invention. A continuous transition between the temperatures shown in any pair of immediate stages is considered as part of the scale of temperatures and time scales specified.

TREATMENT RS-W - SCALE 1 Temperature Scale Time Scale Stage 1 165 to 130 ° C 15 minutes to 24 hours Stage 2 130 to 90 ° C 1 hour to 72 hours RS-W TREATMENT - SCALE 2 Temperature Scale Time Scale Stage I 160 to 130 ° C 30 minutes to 12 hours Stage 2 130 to 90 ° C 2 hours to 72 hours TREATMENT RS-W - SCALE 3 Temperature Scale Time Scale Stage 1 150 - 5 ° C 45 minutes to 75 minutes Stage 2 120 ± 5 ° C 4 to 12 hours Stage 3 105 - 5 ° C 12 A 36 hours Stage 4 95 - 5 ° C zero to 24 hours TREATMENT RS-W - SCALE 4 Temperature Scale Time Scale Stage 1 150 = 5 ° C 1 hour ± 15 minutes Stage 2 120 r 5 ° C 8 - 2 hours Stage 3 105 = 5 ° C 24 Í 6 hours Stage 4 95 = 5 ° C zero to 8 hours HSRS-W The HSRS-W treatment scales are described either as 2 stages or as 4 stages (ie, 4 stage treatment but with the optional fourth stage which, if omitted, results in a 3 stage treatment ).

HSRS-W TREATMENT OF TWO STAGES - SCALE 1 Temperature Scale Time Scale Stage 1 190 t 40 ° C 20 minutes at 72 hours Stage 2 120 r 30 ° C 1 hour at 48 hours HSRS-W TREATMENT OF TWO STAGES - SCALE 2 Temperature Scale Time Scale Stage l 170 ± 20 ° C 4 hours to 48 hours Stage 2 125 ± 15 ° C 4 hours to 36 hours HSRS-W TREATMENT OF TWO STAGES - SCALE 3 Temperature Scale Time Scale Stage 1 170; 20 ° C 12 hours at 36 hours Stage 2 125 = 15 ° C 6 hours at 24 hours HSRS-W TREATMENT OF TWO STAGES - SCALE 4 Temperature Scale Time Scale Stage 1 170 ± 10 ° C 24 ± 4 hours Stage 2 125 - 10 ° C 8 - 2 hours HSRS-W TREATMENT OF THREE / FOUR STAGES - SCALE 1 Temperature Scale Time Scale Stage l 170 ± 20 ° C 4 hours to 48 hours Stage 2 125 = 15 ° C 6 hours to 24 hours Stage 3 105 = 10 ° C 8 hours to 30 hours Stage 4 95 ± 5 ° C zero to 8 hours HSRS-W TREATMENT OF THREE / FOUR STAGES - SCALE 2 Temperature Scale Time Scale Stage 1 170 ± 10 ° C 24 ± 4 hours Stage 2 125 ± 10 ° C 8 ± 4 hours Stage 3 105: 5 ° C 18 ± 6 hours Stage 4 95 - 5 ° C zero to 8 hours In summary, the use of the RS-W aging method of the present invention provides a means to ensure a level of strength for aluminum-lithium alloys, such as 8090, "which are reinforced by the precipitation of S 'and d' , which is comparable with conventional aluminum-copper alloy materials, while also restricting the degree of undesirable and subsequent reinforcement, and the associated loss in fracture resistance that may occur due to prolonged exposure to temperatures moderately elevated, as found by fuselage structures and tail and wing lining during exposure to the site when relatively high ambient temperatures exist and / or there is significant heating due to solar radiation. The use of the HSRS-W aging method of the invention provides a means to achieve a resistance level for aluminum-lithium alloys, such as 8090, which is reinforced by the precipitation of d1 and S ', which is comparable with aluminum-copper alloy materials and also aluminum-zinc. The invention also provides a means of achieving an improved level of strength of all other lithium-aluminum alloys, whether in the form of plate, sheet form, extruded form or any other primarily reinforced by precipitation of d '(Al3Li) precipitates in conjunction with other precipitates such as S '(Al2CuMg). In addition, the invention also provides an improvement in the strength of the 8090 alloy in the form of recrystallized sheets to intergranular corrosion.

INITIAL CONDITION PROPERTIES AS RECEIVES PROPERTIES AFTER 920 HOURS A RESISTANCE TO ALARG-CONDUCT RESISTANCE. RESISTANCE TO ALARG-CONDUCT RESISTANCE. PROOF OF 0.2% ELECT. PROOF OF 0.2% ELECT. p. MPa%% IACS MPa MPa%% IACS T81 IT31 + 160 C / 24 HOURS) 293 424 13.5 lß.B 320 439 10.2 19.6 T81 + REVERSION 260 379 14.8 17.6 324 431 10.3 19.8 (200 * C / 10 MINUTES! 68 Tßl + 200'CMO MINUTES + * - 295 416 13.6 18.6 339 471 10.0 20.3 170 * C / 4 HOURS T81 + 200 C / 12 HOURS 346 411 8.4 18.3 394 471 5.4 20.4 TABLE 1 ELECTRICAL CONDUCTIVITY AND MECHANICAL PROPERTIES AT ENVIRONMENTAL TEMPERATURE OF LOT 1 8090 IN SEVERAL INITIAL CONDITIONS AFTER 920 HOURS AT lOOoC THERMAL EXPOSURE.

CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (THERMAL TEMPERATURE HOURS 0.1X 0.2X 0.5X AMBIENT VOLTAGE% 150"C 135 # C 120" C 100"C 85 # C 70" C Mf "Mr * Mr * Nfa XI? CS 205 216 238 342 20.0 249 260 284 384 15.8 256 267 291 392 15.8 to 30 255 277 303 408 15.8 6 50 100 274 285 310 413 13.9 6 50 500 282 294 318 416 14.3 6 50 300 500 284 294 319 416 13.3 TABLE 2A MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 1 OF LEAF 8090 OF 1.6mm IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 1h / 160 * C + 6h / 135 * C + 3h / 120 * C -I- 60h.100 * CY THERMAL EXPOSURE AFTER 86 * CY 70"C. STARTING CONDITION: SOLUTION TREATED TO SOS AND EXAGGERATED CONTROL OF 2% ± 0.6% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (HOURS AT TEMPERATURE) THERMAL O. U 0.2X 0.5X THE AMBIENT VOLTAGE 150ßC 133 »C 120» C 100"C 85 # C 70 # C HG. NPB nn T? IIACS 205 216 238 342 20.0 249 260 284 384 15.8 8 - - 252 269 294 393 14.9 t 8 50 - 264 280 303 406 14.5 8 50 100 277 287 311 413 14.5 8 50 500 284 296 321 426 16.1 50 500 500 281 292 316 419 13.6 TABLE 28 MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 1 OF LEAF 8090 FROM 1 6m IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING FROM 1/16 '' C + 6h / 136 * C + 8/120 * C + 60h / 100 * CY THERMAL EXPOSURE POSTER 86 * CY 70 * C. DEPARTURE CONDITION: SOLUTION TREATED AT 606 C AND EXAGGERATED CONTROL OF 2% ± 0.6% IN THE LONGITUDINAL DIRECTION AGING TREATMENT CONDUCTIVITY SENSITIZATION TEST RESISTANCE RESISTANCE TO EXTENSION (HOURS AT TEMPERATURE) ELECTRIC TO TEMP. THERMAL ENVIRONMENTAL TENSION 0.1X 0.2X 0.5X IS0C 13S »C 120» C 100 * C Í3 # C 70 »C Mr * Mr * r * Mr * XIACI 205 216 238 342 20.0 6 ---. 6 -. - 249 260 284 384 15.8 6 16 - 265 275 301 403 15.4 6 16 50 251 280 306 407 15.8 co 6 16 50 100 276 287 312 413 14.9 6 16 50 SOO 283 295 320 423 13.3 16 30 500 300 283 294 319 420 12.2 TABLE 2C MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 1 OF LEAF 8090 DE L .ßm IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 1h / 16"C + 6h.136 * C + 16h / 120 * C + 60h / 10? 'CY THERMAL EXPOSURE AFTER 86"C AND 70" C CONDITION OE DEPARTURE: SOLUTION TREATED AT 606 C AND EXAGGERATED CONTROL OF 2% ± 0.6% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (HOURS AT TEMPERATURE) THERMAL THE AMBIENT VOLTAGE 0.1X 0.2X O.SX 150'C 135 «C HO * C 100 # C ß5» C 70 »C Mr * M * Mr * Mr * XI? CS 1 - . 1 - 205 216 238 342 20.0 17. 1 12 - 260 270 293 393 14.7 18. 1 12 6 269 278 302 403 14.7 18. 1 12 6 50 272 287 312 411 14.1 19. fó 1 12 6 50 100 274 290 316 420 14.8 19. 1 12 6 50 500 292 301 323 432 16.8 19. 1 12 6 50 SOO 500 2 28899 300 323 428 13.3 19.

TABLE 2D MEASUREMENTS OE ELECTRICAL CONDUCTIVITY AND TRANSVERSE TENSION PROPERTIES DISTANT FOR LOT 1 OF LEAF 8090 DE l .ßmp. IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OE 1h / 160 * C + 12h / 136 * C + 6/120 * C + 60/10? 'C AND THERMAL EXPOSITION POSTERI AT 85'C AND 70 * C. DEPARTURE CONDITION: SOLUTION TREATED AT 60S * C AND EXAGGERATED CONTROL OF 2% ± 0.6% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. TEMPERATURE RISKS) THERMAL THE AMBIENT VOLTAGE 0.1X 0.2X 0.5X 150 «C 135 # C 120» C 100 «C 8S * C 70 * C M * Mr * Mr * Mr * XIACS 205 216 238 342 20.0 17.5 12 260 270 295 393 14.7 18.5 12 16 274 284 309 410 15.5 18.9 12 16 50 274 289 314 417 13.6 19.2 you 12 16 50 100 283 293 319 422 12.8 19.5 12 16 50 500 290 299 324 427 11.8 19.6 12 16 SO S --- 0 SOO 292 302 327 427 12.3 19.8 TABLE 2E ELECTRICAL CONDUCTIVITY MEASUREMENTS AND TRANSVERSE TENSION PROPERTIES DISTANT FOR LOT 1 OF LEAF 8090 DE t .S pi IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 1 / 1SO * C + 12h / 136 * C + 161.- 120 * 0 + 60h / 100 * CY THERMAL EXPOSURE AFTER 86 * CY 70'C. DEPARTURE CONDITION: SOLUTION TREATED AT 606 * C AND EXAGGERATED CONTROL OF 2% ± 0.6% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (HOURS AT TEMPERATURE! THERMAL THE AMBIENT VOLTAGE 0.1X 0.2X 0.5X ISSO'C 135 * C 120 »C 100 # C 85ßC 70 # C M * Mr * Mr * Nr * XIAC8 237 247 270 372 16.0 266 279 304 406 15.0 277 287 311 413 17.4 50 264 293 318 421 14.3 50 100 285 296 322 423 13.3 50 SOO 291 301 323 429 13.6 SO SOO SOO 291 302 326 429 14.1 TABLE 2F THE CONDUCTIVITY MEASUREMENTS THE CTRICA AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 1 OF LEAF 8090 OF L. Mm mm IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 3l? / 16? 'C + 12h- 35 * C + 6h / 120 * C + 60h / 100 * CY THERMAL EXPOSURE AFTER 86'C AND 70 * C. DEPARTURE CONDITION: SOLUTION TREATED AT 606 C AND EXAGGERATED CONTROL OF 2% ± 0.6% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (HOURS AT TEMPERATURE! THERMAL 0.1X 0.2X O.SX THE AMBIENT VOLTAGE I50 # C 135 * C 120 * C 100 # C ßs »c 70« C Mr * Mr * Mr * Mr * XIACS 237 247 270 372 16.0 17.9 12 266 279 304 406 15.0 18.7 12 16 280 291 316 422 16.5 19.1 12 16 50 273 291 317 418 13.3 19.4 12 12 50 100 279 298 324 426 12.3 19.6 12 16 50 500 294 303 328 434 12.6 19.7 12 16 50 500 SOO 294 306 331 436 11.8 20.0 TABLE 2G MEASUREMENTS OE ELECTRICAL CONDUCTIVITY AND TRANSVERSE TENSION PROPERTIES DISTANT FOR LOT 1 OF LEAF 8090 OF 1-½ mm IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 3h / 16"C + 12h / 136 * C + 1ßh.120 * C + 60h.100 * CY THERMAL EXPOSURE AFTER 86"C AND 70 * C. DEPARTURE CONDITION: SOLUTION TREATED AT 506 * C AND EXAGGERATED CONTROL OF 2% ± 0.6% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. TEMPERATURE INHERITING) THERMAL 0.1X 0.2X 0.SX THE ENVIRONMENTAL TENSION 150 # C 135 »C ItO'C 100 # C 85 * C 70» C MP «NF * Nfa Hr * XIACS 224. 2 232.0 234.3 366.3 20.6 16.4 239. 1 267.3 290.8 398.2 18.5 17.5 273. 4 283.4 307.9 414.3 14.4 17.9 8 50 287.2 293.1 320.2 430.0 16.8 18.3 6 8 50 100 288.7 296.5 320.9 429.8 17.2 18.3 tt 6 8 50 250 290.5 298.0 322.1 429.3 14.6 18.6 6 8 50 250 500 297.3 309.7 328.3 434.3 12.7 18.8 8 50 (301.7) (307.3) (320.6) (413.2) (12.8) (18.3) TABLE 3A ELECTRICAL CONDUCTIVITY MEASUREMENTS AND DISTANT TRANSVERSAL TENSION PROPERTIES FOR LOT 2 OF LEAF 8090 FROM 1.9-nm IN EACH AGING STAGE FOR THE AGING SEQUENCE OF 1h / 15? 'C + 6hM36 * C + 8h / 120 * C + SOh / 100'CY THERMAL EXPOSURE AFTER 85 * C AND 70 * C. (LONGITUDINAL RESULTS SHOWN IN PARENTHESIS). DEPARTURE CONDITION: SOLUTION TREATED AT S30 C AND EXAGGERATED CONTROL OF 2% t 0.6% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (HOURS AT TEMPERATURE) THERMAL 0.1X 0.2X 0.5X THE ENVIRONMENTAL TENSION 150 »C 120» C 105 * C 95 # C 83 # C 70 * C Mr * Nr * Nr * Nr * XIACS 224. 2 232.0 234.3 366.3 20.6 16.4 233. 7 260.9 283.3 394.3 18.3 17.4 268. 1 273.5 299.2 409.7 18.0 17.8 274. 1 281.1 306.2 413.6 19.1 17.9 * Ü 100 277.4 284.7 308.4 416.3 14.7 18.2 8 2S0 283.2 291.0 315.8 422.4 17.7 18.3 8 250 300 288.5 296.1 320.5 427.0 16.8 18.4 8 250 SOO 287.9 294.7 317.7 426.9 19.3 18.4 (288.7) (293.5) (303.9) (4 40022..55)) (13.9) (17.9) TABLE 3B MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE TENSION PROPERTIES DISTANT FOR LOT 2 OF LEAF 8090 FROM 1.9mm IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 1h.16? "C + 8h / 120 * C + 24h / 106 * C + 24h / 9ß'CY THERMAL EXPOSURE AFTER 8S * CY 70 * C (LONGITUDINAL RESULTS SHOWN IN PARENTHESIS) STARTING CONDITION: SOLUTION TREATED AT 63? "C AND EXAGGERATED CONTROL OF 2% * 0.6% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (I (HOURS AT TEMPERATURE! THERMAL 0.1X 0.2X 0.5X THE ENVIRONMENTAL VOLTAGE 150 * C 120 # C 105ßC 95 «C 85 * C 70» C Nr * Nr * Mr * Nr * XIACS 224. 2 232.0 254.3 366.3 20.6 16.4 16 264.4 272.1 295.1 405.7 18.5 17.5 16 24 274.1 281.9 305.7 415.6 19.0 18.0 16 24 24 276.9 284.5 309.1 419.7 16.4 18.1 & 16 24 24 100 274.8 282.5 306.1 417.7 17.6 18.3 16 24 24 230 285.8 293.6 317.9 424.5 14.4 18.4 16 24 24 250 500 290.7 298.4 323.2 433.6 17.6 18.6 16 24 24 (299.4) (304.7) (316.3) (405.7) (12.6) ( 18.1) TABLE 3C MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE TENSION PROPERTIES DISTANT FOR LOT 2 OF LEAF 8090 OF 1.9mm IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 1h / 160 * C + 16h / 12? "C + 24h / 106 * C + 24h / 96 * CY THERMAL EXPOSURE AFTER 85 * C AND 70 * C (LONGITUDINAL RESULTS SHOWN IN PARENTHESIS) ODE CONDITION: SOLUTION TREATED AT 630 * C AND EXAGGERATED CONTROL OF 2% ± 0.6% IN THE LONGITUDINAL DIRECTION OE TREATMENT CONDUCTIVITY AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (HOURS AT TEMPERATURE THERMAL THE AMBIENT VOLTAGE 0.1X 0.2X 0.5X 150 »C 125» C 10S »C 95 # C 85« C 70 * C Mr * Nr * Nr * Mr * XIACS 224. 2 232.0 254.3 366.3 20.6 16.4 2. 34. 3 263.2 286.4 398.2 18.7 17.4 269. 8 277.7 300.7 410.8 14.1 17.9 273. 6 282.9 306.6 417.4 17.7 18.1 & 100 282.0 289.3 312.3 423.8 17.1 18.3 230 286.6 294.1 318.0 428.3 16.3 18.4 230 300 287.3 294.8 318.7 424.9 17.1 18.5 250 SOO 286.0 293.1 316.5 424.6 16.3 18.5 (293.7) (299.6) (312.1) (403.2) (12.7) (18.0) TABLE 30 MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE TENSION PROPERTIES DISTANT FOR LOT 2 OF LEAF 8090 OF 1.9mm IN CAOA AGING STAGE FOR THE SEQUENCE OF AGING OF 1h / 160 * C + 8h / 126 * C -I- 24h.106 * C + 24h / 96 * CY THERMAL EXPOSURE AFTER 85 * C AND 70 * C. (LONGITUDINAL RESULTS SHOWN IN PARENTHESIS). CONDITION OF DEPARTURE: SOLUTION TREATED AT 630 * C AND CONTROL EXAGERATED OE 2% * 0.6% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (HOURS AT TEMPERATURE) THERMAL 0.1X 0.2-t O.SX THE ENVIRONMENTAL TENSION 150 »C 125 * C 105 * C 95 # C ß5 # C 70" C NP * HP * HP * NPA XIACS 224. 2 232.0 234.3 366.3 20.6 16.4 16 267.1 274.9 298. 406.9 17.6 17.6 16 24 279.6 287.4 311.6 420.6 20.1 18.1 16 24 24 285.1 292.7 317.0 425.6 14.9 18.2 é 16 24 24 100 287.9 295.4 319.2 428.0 14.8 18.4 16 24 24 250 291.5 299.4 324.7 433.7 13.9 18.5 16 24 24 250 SOO 293.2 300.5 324.0 433.9 15.8 IB. 16 24 24 (301.4) (306.8) (318.7) (410.2) (12.4) (18.2) TABLE 3E MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 2 OF LEAF 8090 FROM 1.9? M IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OE 1h / 160 * C + 16h / 126 * C + 24h / 106 * C + 24h / 96 * CY THERMAL EXPOSURE AFTER 8S * CY 7? "C. (LONGITUDINAL RESULTS SHOWN IN PARENTHESIS) STARTING CONDITION: SOLUTION TREATED AT 630 * CY AND EXAGGERATED CONTROL OE 2% ± 0.6% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMPERATURE TEMPERATURE TEMPERATURE) THERMAL ENVIRONMENTAL TENSION • C 120 »C 105» C 95 # C 85"C 70" C HP * NP * HP * HPa XI? CS 198. 4 205.9 225.8 341.6 22.4 15.9 232. 2 239.4 260.6 374.4 19.3 16. ß 24 252.1 259.5 282.1 399.3 20.3 17.4 24 24 256.6 264.2 286.5 399.0 20.3 17.5 24 24 100 267.3 274.9 298.3 412.8 19.5 17.9 8 24 24 250 278.2 283.6 309.3 418.3 15.5 18.0 8 24 24 250 500 279.4 286.6 309.4 420.3 16.3 18.2 2 * 24 250 1250 283.8 290.5 313.0 425.4 17.2 18.2 24 24 (273.9) (278.3) (290.8) ((338866..99)) (10.5) (.5) TABLE 3F MEASUREMENTS OE ELECTRICAL CONDUCTIVITY AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 2 OF LEAF 8090 FROM 1.9 m IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 1/135 * C + 8h / 120 * C + 24 .105 * C + 24/95 * CY THERMAL EXPOSURE AFTER 85 * CY 7? "C. (LONGITUDINAL RESULTS SHOWN IN PARENTHESIS). * CONDUCTIVITY TREATMENT OF TEST RESISTANCE RESISTANCE TO ELECTRIC ALARG TO TEMP AGING SENSITIZATION (HOURS AT TEMPERATURE! THERMAL ENVIRONMENTAL TENSION 0. 1X 0.2X 0.5X X 135 * C 120 »C 105 # C 95 * C 85» C 70 # C NPa NPa NPa MPa XIACS 198. 4 205.9 225.8 341.6 22.4 15.9 16 -. 16 - - 245.3 252.7 274.8 387.5 22.8 17.2 16 24 - 258.9 266.2 288.8 400.0 19.0 17.5 16 24 24 261.8 269.6 292.5 393.5 16.4 17.8 ro 16 24 24 100 270.2 277.2 299.5 414.8 18.1 18.0 16 24 24 250 280.2 287.9 311.9 420.6 13.9 18.1 16 24 24 230 500 282.4 288.9 311.6 417.6 16.7 18. 16 24 24 250 1250 289.2 296.5 319.7 425.8 14.9 18.4 14 24 24 (286.6) (292.0) (303.8) (399.3) (U.8) (17.8) TABLE 3G MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 2 OE SHEET 8090 DE 1 9n > ... AT EACH AGING STAGE FOR THE AGING SEQUENCE OF 1h / 135'C + 16h / 12? 'C + 24/105"C + 24h / 95 * CY THERMAL EXPOSURE AFTER 85 * C AND 70 * C. ( LONGITUDINAL RESULTS SHOWN IN PARENTHESIS).

CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP- (HOURS AT TEMPERATURE) THERMAL AMBIENT VOLTAGE 0.1X 0.2X 0.5X 135 * C 120 »C 105 * C 95'C 85« C 70"C NPa MPa NPa NPa IACS 189. 5 196.2 213.5 336.1 20.7 15. 7 32 235.2 242.2 263.5 375.5 21.4 16. 8 2 32 24 242.7 249.9 271.3 386.7 18.6 17, .1 2 32 24 100 256.2 263.6 286.2 403.7 19.3 17 6 .5 2 32 24 250 267.7 274.9 297.2 411.9 16.9 17 .7 32 24 250 500 272.4 279.2 301.3 414.3 15.8 18.0 32 24 250 1250 276.1 283.5 306.5 412.5 17.1 18.0 32 24 (260.0) (263.8) (274.8) (377.4) (16.6) (17.1) TABLE 3H MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 2 OF LEAF 2 8090 OF 1.9 m IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 2/12"C + 32h / 120 * C + 24h / 9S * CY THERMAL EXPOSURE AFTER 85 * CY 70 * C (LONGITUDINAL RESULTS SHOWN IN PARENTHESIS) STARTING CONDITION: SOLUTION TREATED AT 630 C AND EXAGGERATED CONTROL OF 2% ± 0.5% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (HOURS AT TEMPERATURE) THERMAL ENVIRONMENT 0.1X 0.2X 0.5X THE TENSION 135 * C 120 * C 105 * C 95 »C 85« C 70 # C NPa NPa NPa NPa XIACS 8 217.8 224.9 244.8 364.1 21.5 16.4 8 240.6 247.5 268.4 389.9 18.6 17.1 8 249.5 256.7 279.1 388.7 18.3 17.4 8 100 262.6 269.6 291.0 408.8 16.5 17.6 £ 8 250 271.9 278.6 300.9 413.9 19.1 17.8 8 250 500 271.3 278.6 300.7 413.1 20.5 18.1 8 250 1250 279.0 286.0 308.7 416.4 17.0 18.1 8 (265.2) (269.8) (281.1) (3 38844..11)) (167.6 (17.3) TABLE 3J MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 2 OF LEAF 8090 OE 1 9mn? AT EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 8/120 * C + 24h / 120 * C + 24h / 95 * C AND THERMAL EXPOSITION AFTER 86 * C AND 70 * C. (LONGITUDINAL RESULTS SHOWN IN PARENTHESIS). DEPARTURE CONDITION: SOLUTION TREATED AT 530 * C AND EXAGGERATED CONTROL OF 2% ± 0.5% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (HOURS AT TEMPERATURE) THERMAL TENSION 0.1X 0.2X 0.5X AMBIENCE 150'C 120 # C 105'C 95 * C 85ßC 70 # C NPa NPa NPa NPa XIACS 0. 75 241.6 248.7 271.3 389.4 20.7 17.6 0. 75 24 261.6 268.4 291.4 405.2 20.1 18.0 cp 0. 75 24 262.3 270.2 294.4 406.3 18.6 18.2 0. 75 24 24 268.3 276.1 300.6 417.5 19.6 18.2 TABLE 4A MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 2 OF LEAF 8090 FROM 1 611 ... 1 AT EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 0.7BI./15? "C + 8l? / 12 ? 'C + 24/105 * C + 8h / 9S * CO 24h / 95 * C STARTING CONDITION: SOLUTION TREATED AT 530 C AND EXAGGERATED CONTROL OF 1.75% ± 0.25% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (HOURS AT TEMPERATURE) THERMAL TENSION 0.1X 0.2X O.SX AMBIENTE 150 * C 120 # C 105 * C 95 # C 85 # C 70 «C NPa HPa NP * NPa XIACS 1. 00 250.1 258.2 283.4 394.4 18.3 17.8 1. 00 24 266.7 274.8 299.7 411.3 19.3 18.1 1. 00 24 272.1 280.2 303.8 421.0 18.1 18.3 55 1. 00 24 24 273.6 281.5 306.3 415.8 16.2 18.3 TABLE 4B MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 2 OF LEAF 8090 FROM 1.6 Nm IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING OF 1 h / 15"c + 8h / 120 * C + 24h / 10S * C + 8 .9S * CO 24/95 * C STARTING CONDITION: SOLUTION TREATED AT 530 C AND EXAGGERATED CONTROL OF 1.76% ± 0.25% IN THE LONGITUDINAL DIRECTION CONDUCTIVITY TREATMENT AGING SENSITIZATION TEST RESISTANCE RESISTANCE TO ELECTRICAL EXTENSION TO TEMP. (HOURS AT TEMPERATURE THERMAL THE AMBIENT VOLTAGE 0.1X 0.2X O.SX 150ßC 120 »C 105 # C 95 # C 85 # C 70ßC NPa NPa NPa NPa XIACS 1. 25 247.8 25S.1 278.6 391.4 18.9 17.9 1. 25 24 270.7 278.9 304.3 415.2 16.8 18.2 1. 25 24 272.9 280.9 306.2 419.7 16.8 18.3 1. 25 24 24 272.2 279.4 303.4 416.8 18.0 18.4 TABLE 4C MEASUREMENTS OF ELECTRICAL CONDUCTIVITY AND TRANSVERSE STRESS PROPERTIES DISTANT FOR LOT 2 OF LEAF 8090 OE l .ßmro IN EACH PHASE OF AGING FOR THE SEQUENCE OF AGING 1.25 h / 1BO * C + 8h / 120 * C + 24h / 105 * C + 8h / 96 * CO 24h / 95 * C STARTING CONDITION: SOLUTION TREATED AT 630 C AND EXAGGERATED CONTROL OF 1.75% ± 0.25% IN THE LONGITUDINAL DIRECTION HOURS OF CONDITION RREESSIISSIT [? ENNCIA RESISTANCE LENGTHENING EXPOSURE OF PRT TES TO THE THERMAL TENSION AT 0.2% 70 ° C MPa MPa% - (CONTROL) T81 309. .41 441.3 13.3 - (CONTROL) RS-W 279. • O2 413.72 16.62 100 T81 314.5 449.4 13.9 100 RS-W 284.91 416.71 16.81 200 T81 315 446.1 14.2 200 RS-W 286 422.31 17.31 500 T81 314. 451.9 13.3 500 RS-W 291, 431.71 15.81 1000 T81 316.4 454.3 11.1 1000 RS-W 297.71 440.41 16.11 2000 T81 330.71 466.3 12.61 2000 RS-W 300.81 436.9 15.71 TABLE 5 PROPERTIES OF TEN, TRANSVERSAL DN DISTANT AT ENVIRONMENTAL TEMPERATURE FOR BATCH 2 OF SHEET 8090 OF 1.6mm FROM THERMAL EXPOSURE TEST AT 70 ° C INVOLVING T81 AND AGED MATERIAL TO THE PREFERRED RS-W CONDITIONS (ie, lh / l50 ° C + 8h / l20 ° C + 24h / l05 ° C + 8h / 95 ° C).

Average of two tests. Average of 16 tests. The highest and lowest extreme values of the 0.2% Test Resistance for the "Control" RS-W tests were 2.3 MPa above the average and 2.5 MPa below the average.

Claims (14)

NOVELTY OF THE INVENTION CLAIMS

1. A method of heat treatment of an aluminum-lithium alloy characterized in that it includes carrying out a succession of at least two stages of artificial aging, the first of such stages being carried out within a first temperature range and therefore the an additional stage being carried out within a scale of reduced temperatures.

2. A method of heat treatment of an aluminum-lithium alloy, according to claim 1, further characterized by including carrying out the first stage of artificial aging substantially within the temperature range of 165 ° C to 130 ° C and substantially within the time scale of 15 minutes to 24 hours, and subsequently carrying out a second of said artificial aging stage substantially within a temperature range of 130 ° C to 90 ° C and substantially within a time scale. from 1 hour to 72 hours.

3. A method of heat treatment of an aluminum-lithium alloy, according to claim 1, further characterized by including carrying out the first stage of artificial aging within a scale of temperature of 160 ° C to 130 ° C and substantially within a time scale of 30 minutes to 12 hours, and subsequently carrying out a second stage of artificial aging substantially within a temperature range of 130 ° C to 90 ° C and substantially within a time scale of 2 to 72 hours.

4. A method of heat treatment of an aluminum-lithium alloy, according to claim 1, further characterized by including carrying out the first stage of artificial aging substantially within a temperature range of 155 ° C to 145 ° C and substantially within a time scale of 45 minutes to 75 minutes, subsequently carrying out a second stage of artificial aging substantially within a temperature range of 125 ° C to 115 ° C and substantially within a time scale of 4 hours. hours to 12 hours, subsequently carrying out a third stage of artificial aging substantially within a temperature range of 110 ° C to 100 ° C and substantially within a time scale of 12 to 36 hours, and subsequently carrying out a fourth stage of artificial aging substantially within a temperature range of 100 ° C to 90 ° C and substantially within a time scale of zero ho Flush to 24 hours.

5. A method of heat treatment of an aluminum-lithium alloy, according to claim 1, further characterized by including carrying out the first artificial aging stage substantially within a temperature range of 155 ° C to 145 ° C and substantially within a time scale of 45 minutes to 75 minutes, subsequently carrying out a second stage of artificial aging substantially within a range of temperature of 125 ° C to 115 ° C and substantially within a time scale of 6 hours to 10 hours, subsequently carrying out a third stage of artificial aging substantially within a temperature range of 110 ° C to 100 ° C and substantially within a time scale of 18 to 30 hours, and subsequently carrying out a fourth stage of artificial aging substantially within a temperature range of 100 ° C to 90 ° C and substantially within a time scale of zero hours to 8 hours.

6. A method of heat treatment of an aluminum-lithium alloy, according to claim 1, further characterized by including carrying out the first stage of artificial aging substantially within a temperature range of 230 ° C to 150 ° C and substantially within a time scale of 20 minutes to 72 hours, and subsequently carry out a second stage of artificial aging substantially within a temperature range of 150 ° C to 90 ° C and substantially within a time scale of 1 hours to 48 hours.

7. A method of heat treatment of an aluminum-lithium alloy, in accordance with. claim 1, further characterized in that it includes carrying out the first stage of artificial aging substantially within a temperature range of 190 ° C to 150 ° C and substantially within a time scale of 4 hours to 48 hours, and subsequently carrying out a second stage of artificial aging substantially within a temperature range of 140 ° C to 110 ° C and substantially within a time scale of 4 hours to 36 hours.

8. A method of heat treatment of an aluminum-lithium alloy, according to claim 1, further characterized in that it includes carrying out the first stage of artificial aging substantially within a temperature range of 190 ° C to 150 ° C and substantially within a time scale of 12 hours to 36 hours, and subsequently carrying out a second stage of artificial aging substantially within a temperature range of 140 ° C to 110 ° C and substantially within a time scale of 6 hours to 24 hours.

9. A method of heat treatment of an aluminum-lithium alloy, according to claim 1, further characterized by including carrying out the first stage of artificial aging substantially within a temperature range of 180 ° C to 160 ° C and substantially within a time scale of 20 hours to 28 hours, and subsequently carrying out a second stage of artificial aging substantially within a scale of temperature from 135 ° C to 115 ° C and substantially within a time scale of 6 hours to 10 hours.

10. A method of heat treatment of an aluminum-lithium alloy, according to claim 1, further characterized by including carrying out the first stage of artificial aging substantially within a temperature range of 190 ° C to 150 ° C and substantially within a time scale of 4 hours to 48 hours, subsequently carrying out a second stage of artificial aging substantially within a temperature range of 140 ° C to 110 ° C and substantially within a time scale of 6 hours. hours to 24 hours, subsequently carrying out a third stage of artificial aging substantially within a temperature range of 115 ° C to 95 ° C and substantially within a time scale of 8 to 30 hours, and subsequently carrying out a fourth stage of artificial aging substantially within a temperature range of 100 ° C to 90 ° C and substantially within a time scale of zero hours to 8 hours.

11. A method of heat treatment of an aluminum-lithium alloy, according to claim 1, further characterized by including carrying out the first stage of artificial aging substantially within a temperature range of 180 ° C to 160 ° C and substantially within a time scale of 20 hours to 28 hours, and subsequently carry out a second stage of artificial aging substantially within a temperature range of 135 ° C to 115 ° C and substantially within a time scale of 4 hours to 12 hours, subsequently carrying out a third stage of artificial aging substantially within a temperature range of 110 ° C to 100 ° C and substantially within a time scale of 12 to 24 hours, and subsequently carrying out a fourth stage of artificial aging substantially within a temperature range of 100 ° C to 90 ° C and substantially within from a time scale of zero hours to 8 hours.

12. A method for forming a thermally bonded, adhesive-bonded structure of at least two components, at least one of which comprises an aluminum-lithium alloy, the method characterized in that it includes the steps of forming a pre-assembly. curing of the components and adhesive and treating the assembly with heat according to the method of claim 1, whereby the adhesive is cured during at least one of the stages of artificial aging and in this way the heat-treated structure adhesively bonded .

13. A method of heat treating an aluminum-lithium alloy substantially as described herein.

14. A method for forming a bonded heat treated structure substantially as described herein. ABSTRACT A method of heat treatment of an aluminum-lithium alloy is provided. The method includes carrying out a succession of at least two stages of artificial aging. The first of such steps is carried out within a first temperature scale and one or more additional steps are carried out within reduced temperature ranges successively to promote the precipitation of the d 'phase of the alloy.