ISSN 20702051, Protection of Metals and Physical Chemistry of Surfaces, 2014, Vol. 50, No. 2, pp. 236–243. © Pleiades Publishing, Ltd., 2014. Original Russian Text © A.M. Semenov, V.S. Sinyavskiy, V.D. Kalinin, 2014, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2014, Vol. 50, No. 2, pp. 211–218.

PHYSICOCHEMICAL PROBLEMS OF MATERIALS PROTECTION

Corrosion Resistance of Aluminum–Lithium Alloys under Various Climatic Conditions A. M. Semenova, *, V. S. Sinyavskiyb, **, and V. D. Kalinin a

Scientific Research Institute of Natural Gasses and Gas Technology, Gazprom VNIIGAZ, Razvilka, Moscow oblast, 142717 Russia b AllRussia Institute of Light Alloys, ul. Gorbunova 2, Moscow, 121596 Russia *email: [email protected] **email: [email protected] Received October 9, 2012

Abstract—The corrosion resistance (stress corrosion cracking, exfoliation, intergranular corrosion) of a wide group of aluminum–lithium alloys has been studied under atmospheric conditions with various corrosion environments. Corrosion behavior of experimental and commercial batches of aluminum–lithium alloys has been established as a function of the chemical composition of the alloys and ratio of Cu/Mg, Li/Cu + Mg. Under atmospheric conditions, the best corrosion properties are those of an alloy with a Cu/Mg ratio of 0.5 and a ration of Li/Cu + Mg of 0.96. It has been proved that a decrease in Li/Cu + Mg to 0.56–0.76 leads to impairment of corrosion properties. Accelerated corrosion tests result in the same conclusions. DOI: 10.1134/S2070205114020142

INTRODUCTION The requirements of modern materials have signif icantly expanded the scope of application of alumi num alloys. For instance, extruded profiles made of alloy 6063T6 are being successfully used for construct ing suspended ventilated facades. Tests of this alloy performed by AllRussia Institute of Light Alloys (VILS) showed that this alloy is not sensitive to exfoli ation corrosion and stress corrosion cracking. Such material can remain serviceable for more than 50 years [1]. Drill tubes made of alloys D16T and 1953 are used in the oil industry [2]. OSTG tubes of such alloys are also being developed [3]. The interest in aluminum alloys is primarily due to their low specific weight and high corrosion resistance even in hydrogensulfide environment [4]. VILS experts have recently new alloys of aluminum alloying with lithium [5, 6]. Fur ther improvement of Al–Li alloys resulted in develop ment of alloy 2099 by experts in the United States (Alcoa) and Canada [7, 8]. Aluminum–lithium alloys possess a unique set of properties: combination of high static and dynamic strength with the lowest (~2.56 × 103 kg/m3) density (in comparison with conventional ~2.7 × 103 kg/m3 aluminum alloys), high modulus of elasticity, and suf ficient weldability. It is obvious that the new genera tion of aluminum alloys will be of great interest to engineers in various industries, and, according to the predictions of some prominent scientists, it should be competitive with conventional aluminum alloys [9]. However, at present, aluminum–lithium alloys are used only in the aerospace industry. This is because of

their unstable properties and the higher costs of semi products. In addition, there is a lack of reliable inte grated data on corrosion resistance of such alloys under actual atmospheric conditions (only fragmen tary facts are available). The authors of [10–12] inform that operating aircrafts, in structures of which members of Al−Li−Cu alloy are used, in marine con ditions water condensate containing chlorides can develop on the surfaces. The authors of the publication [13] studied an alloy of Al−Li−Mg system (1420) note that on degree of corrosion aggression environments settle down in the following order: sea tropical atmo sphere, 3% solution of chloride sodium, chamber of a salt fog, environment of the industrial region. OJSC VILS, on the basis of tests carried out for 45 years in four exposure station and periodically on the deck of a scientificandresearch vessel, has acquired a broad experience in forecasting corrosion behaviour of traditional aluminium alloys in various atmospheric conditions [14]. As mentioned above, aluminum–lithium alloys are a new generation of aluminum alloys with unique engineering properties. Modern engineering struc tures operate under severe technological and climate conditions. Thus, fighter aircraft used on aircraft car riers pass via several climatic regions when on long distance missions. Therefore, determination of the corrosion properties of aluminum–lithium alloys under actual operating conditions is a focus of atten tion.

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237

Table 1. Chemical composition of aluminum–lithium alloys Composition of elements, wt %

Element ratio

Sum of elements

Element ratio

Cu/Mg

Cu + Mg

Li/Cu + Mg

– – – 2.0 0.5 1.6 4.14 2.0 16.6

– – – 2.1 2.1 3.6 3.6 2.1 2.65

– – – 0.96 0.96 0.56 0.56 1.19 0.76

Alloy no. 1 2 3 4 5 6 7 8 (1440) 9 (1450)

Li

Cu

Mg

Zr

0.8 1.9 2.3 2.0 2.0 2.0 2.0 2.5 2.0

– – – 1.4 0.7 2.2 2.9 1.4 2.5

– – – 0.7 1.4 1.4 0.7 0.7 0.15

0.10 0.09 0.10 0.10 0.10 0.10 0.1 0.09 0.09

This work is purposed at determination of the cor rosion properties of semiproducts made of alumi num–lithium alloys under atmospheric conditions. MATERIALS AND METHODS The studies were performed on specimens cut out in the longitudinal and transversal directions of extruded aluminum–lithium strips. Their chemical composition is summarized in Table 1. In addition to the alloys of experimental batches, tests were per formed with commercial plates 55 mm in thickness made of alloy 1440 (the chemical composition corre sponds to alloy no. 8) and extruded semiproducts made of alloy 1450 (the chemical composition of which corresponds to that of alloy no. 9). Fullscale tests in a marine tropical atmosphere (with the main test period depending on the climatic conditions of the Indian Ocean) were carried out on the forecastle deck of the Izumrud research vessel. Specimens were placed into special cartridges, which then were positioned at an angle of 45° to the horizon. The location of posi tioning was selected with provision of testing of alumi num–lithium alloys under severe conditions of solar radiation and alternate wetting with marine water. The overall test period was 312 days. Specimens were tested at the exposure station of VILS (industrial atmo sphere, Fig. 1), at the Northern corrosion station (sea atmosphere of the Barents Sea coast), and in Cuba (tropical atmosphere). Accelerated corrosion tests were perform with regard to resistance to —stress corrosion cracking (SCC) in accordance with ISO 9591:2004 by the method of constant axial tensile stress and by the method of preset specimen deformation (Cring specimen); —exfoliation corrosion (EXCO) in accordance with ISO 11881:1999; —integranular corrosion (IGC) in accordance with ISO 11846:1995.

Electrochemical characteristics, corrosion poten tial Ecorr, and pitting potential Epitt were determined from polarization diagrams plotted by a PI501 potentiostat, ASTM G389(2010). The specimen microstructure was investigated using a Neophot 2 microscope, fractures were studied using an SMS2 scanning electron microscope, and the fine microstructure was studied using a JEM 100CX electron microscope at 1000 kV. Al–Li Binary Alloys Corrosion tests of semiproducts of Al–Li binary alloys showed that all three alloys are characterized by rather high corrosion properties. Cring test speci mens are not broken within 300 days under at a load 90% of yield strength (YS). Visual inspection of the specimens and microscope studies of polished sections also confirmed the absence of significant corrosion damage. However, in testing of specimens (a double cantilever beam), the growth rates of cracks on an independent plateau (V) are rather high and equal to 9.2 × 10–5 and 9.6 × 10–5 m/s for alloys 2 and 3, respec tively (Table 2). With increase in lithium content in

Fig. 1. Test facilities of exposure station, VILS.

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Table 2. Corrosion properties of extruded strip as a function of lithium content in alloy, aging: 170°C, 16 h, tropical marine atmosphere; electrochemical testing, 3% NaCl solution Corrosion tests

Tests of resistance to SCC Specimen type Alloy no. 1 2 3

102 278 296

|Ecorr–Epitt|1 B

DCB2

Cring

V, m/s

stress YS = 0.9 YS

1.0 × 10–5 9.2 × 10–5 9.6 × 10–5

5 specim > 300 days 5 specim > 300 days 5 specim > 300 days

YS MPa

0.076 0.151 0.169

EXCO

IGC

Pitting Pitting Pitting

Did not exist Did not exist Did not exist

1 Normal hydrogen electrode; 2 Double cantilever beam.

Table 3. Testing of resistance to SCC and EXCO of extruded strips with a cross section of 28 × 50 and 10 × 100 mm made of Al–Li–Cu–Mg alloys; aging: 170°C, 16 h Tests of resistance to SCC shorttransversal; average time before destruction of five specimens, days Alloy no.

accelerated tests

Tests of resistance to EXCO

fullscale Izumrud research vessel

accelerated tests solutions

stress = 100 MPa

Cring specimen stress = 200 MPa

2S

4S

fullscale Izumrud research vessel

estimation/h, mm estimation/h, mm estimation/h, mm 4 5 6 7

17 >38 12 5

>98 >140 >90 47

aluminum resistance to pitting corrosion also increases (absolute difference between the potentials Ecorr and Epitt). Therewith, it should be mentioned

(а)

(b)

(c)

(d)

(e)

(f)

Fig.2. Surface appearance of Al–Li–Mg–Cu alloys after testing in marine tropics (a, b, c) and in solution 4S in accordance with ISO 11881:1999 (d, e, f); (a, d) alloy no. 5, (b, e) alloy no. 6, and (c, f) alloy no. 7; 1 : 1.

EB /0.098 P/did not exist EC /0.150 EC /0.140

EC /0.095 P/0.050 EC /0.123 EC /0.120

EC /0.110 P/0.030 EC /0.135 EC /0.130

that, with an increase in lithium content in aluminum, the strength properties also monotonously increase. Al–Li–Cu–Mg Alloys Due to their low strength properties, aluminum– lithium binary alloys have not found commercial application; therefore, from the practical point of view, it is more reasonable to consider alloys of more complicated structure. Table 3 and Fig. 2 illustrate the results of corrosion tests (accelerated and fullscale test) of four Al–Li–Cu–Mg alloys. It can be seen in the table that the maximum resistance to stress corro sion cracking is that of alloy no. 5 with Cu/Mg ratio of 0.5 and cumulative content of these elements of 2.1 % (Table 1). Tests of resistance to EXCO show that alloy no. 5 is not sensitive to this type of corrosion (P esti mation) with penetration depth into specimen of 0.030–0.050 mm. As seen in the presented table, the accelerated tests in solutions confirm fullscale tests in marine tropical conditions. Herewith, tests of resis tance to EXCO showed that the results obtained in solution 4S correlate satisfactorily with marine tropi cal conditions (Fig. 2). Ringtype specimens of semiproducts made of alloys nos. 8 (1440) and 9 (1450) were tested for resis tance to SCC in the atmosphere of the Barents Sea and in an industrial atmosphere (the city of Moscow). From Table 4, it follows that commercial semiprod ucts that have been aged for maximum strength have a

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Table 4. Comparative tests of resistance to SCC of alloys (accelerated and fullscale test) as a function of chemical compo sition and type of semiproducts; aging for maximum strength: 170°C, 18–20 h Fullscale tests Alloy no.

Type of semiproducts

Accelerated test

YS MPa

coast of the Barents Sea

VILS industrial atmosphere

stress SCC, MPa Plate, h = 55 mm Extruded

8 9

410 470

>175 >175

rather high level of threshold stresses within stress cor rosion cracking. Herewith, the fullscale tests corre late satisfactory with accelerated ones. Alloy 1450 exhibits higher resistance to stress corrosion cracking than does alloy 1440. Comparison of threshold stresses within SCC of semiproducts made of alloy 1450 have showed (Fig. 3) that the most aggressive test environment was the trop ical marine coastal atmosphere (the exposure station in Cuba and the Izumrud research vessel). The atmo spheric conditions of the Barents Sea coast and Mos cow industrial atmosphere (VILS) were less aggressive. Fullscale tests of semiproducts made of commer cial alloys 1440 and 1450 in a marine tropical atmo sphere in Cuba and on board the research vessel (Table 5) revealed the existence of minor centers of EXCO for a naturally aged state, EA⎯EB estimation. Semiproducts aged for maximum strength made of alloy 1440 have an EXCO estimation at the level of EA. Semiproducts made of alloy 1450 become insensitive to EXCO, the specimen surface contains only individ ual corrosion damages, pittings. The tests in a marine tropical atmosphere (Cuba and research vessel) corre spond with laboratory tests.

>175 250

– 250

An overaged state at 190°С for 36 h (Table 6) exhib its an obvious dissonance between accelerated and atmosphere fullscale tests. Semiproducts made of alloys 1440 and 1450 became sensitive during overag ing to EXCO, EA⎯EB estimation. In the overaged state, the corrosion properties of alloy 1450 are higher than those of alloy 1440. Tests in solutions do not con firm atmospheric results and overestimate EXCO: EC⎯ED. While summing up the data in Tables 5 and 6 and Fig. 3, it can be noted that, in terms of resistance to SCC and EXCO, the aggression of atmospheric mediums decreased in the series marine tropics of Cuba and the Izumrud research vessel → Barents Sea coast → Moscow industrial atmosphere. Metallographic and Metallophysical Studies In order to reveal particular features of cracking propagation in aluminum–lithium alloys, metallo graphic studies of alloys no. 3 and no. 9 were carried out (Figs. 4 and 5), as well as fractographic studies of the fracture surface upon stress corrosion cracking of alloy no. 9 (Figs. 6 and 7a, 7b). The structure of Al–Li binary alloys is the solid solution of Li in Al with pre cipitations of strengthening phase δ'(Al3Li), uniformly

Threshold level of SCC, MPa

300 3

250 200

1

4

3

2

4

3

3 4

150 3

1

100

2

50 0 VILS 2year testing

Coast of the Barents Sea 2year testing

1

4

2

Cuba marine tropics

4 1

2

1

Izumrud research vessel

2 Accelerate testing

Fig. 3. Threshold level of stresses at SCC as a function of testing climatic conditions: VILS; coast of the Barents Sea; marine trop ics, Cuba; Izumrud research vessel; laboratory accelerated tests; alloy 1450, extruded strip 60 × 30 mm; (1) natural aging; (2) 120°C, 20 h; (3) 170°C, 20 h; and (4) 190°C, 36 h. PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 50 No. 2 2014

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Table 5. Testing of commercial semiproducts made of alloys 1440 (plate h = 55 mm) and 1450 (extruded) for resistance to EXCO as a function of aging regime EXCO test Alloy

VILS 2year testing

Aging regime

1440 Natural aging

Coast of the Barents Sea 2year testing

Cuba 1.5year testing

Izumrud research vessel marine tropics 312 days

Accelerate testing 2S

4S

–

P

EA

EA

EB

EB

170°C, 18 h

–

P

EA

EA

EA

EB

1450 Accelerate testing

P

EA

EB

EB

EB

EC

P

P

P

P

EA

EA

170°C, 20 h

Table 6. EXCO tests of industrial semiproducts of alloys 1440 (plate) and 1450 (extruded panel) in overaged state (at 190°C for 36–48 hours) EXCO test Alloy

Coast VILS of the Barents Sea 2year testing 2year testing

Cuba 1.5year testing

Izumrud research vessel marine tropics 312 days

Accelerate testing solutions 2S

4S

1440

–

P

–

EB

EC

EC

1450

P

EA

EA

EA

EC

ED

distributed in the grain body up to boundary (Fig. 4). In complexalloying alloys, cracking propagation within SCC is of intercrystalline character. After mechanical breakage of tested specimens (Fig. 7b), the breakage is mainly of transcrystalline type in the form of peculiar brittle fractures. Viscous pit ting fracture, which is characteristic of numerous highstrength aluminum alloys, is not observed in this case.

The article investigated into a series of aluminum– lithium alloys, including Al–Li binary alloys of various chemical compositions with different ratios of alloying components Cu/Mg and Li/Cu + Mg. It was estab lished that, in a marine tropical atmosphere, binary aluminum–lithium alloys have high corrosion charac teristics. Extruded strips made of such alloys have no

Fig. 4. Fine microstructure of alloy no. 3, light field image ×51429; precipitations of metastable δ'(Al3Li) phase and subgrain boundary.

Fig. 5. Corrosion crack propagation in a specimen of Cring made of alloy no. 9, ×250.

RESULTS AND DISCUSSION

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obvious sensitivity to exfoliation corrosion despite the granular structure being noticeably oriented along the main deformation vector [15, 16]. Due to selective etching of Li in Al–Li binary alloys, the resistance to local types of corrosion increases, as does the corro sion rate in terms of weight loss [17]. Rather high rates of crack growth should be mentioned; they increase with an increase in lithium content and, hence, with accumulation of δ'(Al3Li) phase in the alloy [18]. Such behavior of the alloys can be explained in terms of the dislocation–electrochemical mechanism of stress corrosion cracking or, as it is also known, the electrochemical–mechanical theory [19, 20]. This theory is based on interaction of metastable and stable phases with dislocations, numerous examples con firms validity of this theory [21]. In our previous works [22, 23], we showed that the addition of Cu and Mg into aluminum–lithium binary alloys leads not only to a significant increase in strength and other engineering characteristics, but also to the occurrence of sensitivity to stress corrosion cracking, EXCO, and IGC. Results were obtained for accelerated corrosion tests. This work confirms it using real conditions of operation of engineering articles made of aluminum–lithium alloys in environments with various contents of chlo rine ions and with various degrees of corrosion aggres sion. The data in Tables 5 and 6 and Fig. 3 make it pos sible to identify the marine environment of Cuba and marine tropics of the Indian Ocean (Izumrud research vessel) as the most aggressive conditions. Tests per formed by the research vessel under the extremely aggressive conditions of the marine tropics made it possible to, in a moderate length of time (312 days of exposure), provide preliminary conclusions regarding the corrosion behavior of aluminum–lithium alloys under atmospheric conditions. Semiproducts in a nat urally aged state and that have been aged to obtain a maximum strength state exhibit a satisfactory correla tion between fullscale and accelerated tests both with regard to resistance to SCC and EXCO (Fig. 3, Tables 3, 5). There is no such correspondence in the overaged state (190°С, 36–48 h) (Table 6). If the labo ratory tests show rather low resistance to EXCO, EC estimation, then the atmospheric tests determine semiproducts at the level of EA. An important conclu sion is arrived at: for aluminum–lithium alloys of test solutions 2S and 4S, an ISO 11881:1999 additional test should be developed and carried out. It should be noted that the corrosion properties of 1450 alloy with minor addition of Mg are superior to those of alloy 1440. A gain in the corrosion properties for alloy 1450 due to minor controlled addition of Mg has been proved elsewhere [22, 23]. The new alloy 2099 with high corrosion properties also contains a minor con trolled addition of Mg [24]. Previously in [25], for alloys no. 4 and 5, we estab lished the dependence of corrosion resistance on the

241

Fig. 6. Electron fractogram of destruction surface in Cring specimens, alloy no. 9, aging: 170°C, 20 h; ×1000.

(а)

(b) Fig. 7. Electron fractogram of destruction surface within SCC and mechanical break, Cring specimens, alloy no. 9; ×1000; ageing: 170°C, 20 h. (a) stress corrosion cracking; (b) mechanical break.

Cu/Mg ratio and showed that, at an equal amount of these elements—2.1%—the corrosion properties are better for the alloy with a low copper to magnesium ratio (0.5), that is, alloy no. 5. Data were obtained within accelerated corrosion tests. Atmospheric cor rosion tests (Table 3) confirmed this hypothesis com pletely. Alloy no. 5 is in fact insensitive to exfoliation corrosion and has high level of threshold stresses at resistance to SCC, stress level SCC is more than 200 MPa shorttransversal direction. The increase in the Cu/Mg ratio in aluminum–lithium alloys to 3.6 with a decrease in Li/Cu + Mg to 0.56 for alloys nos. 6 and 7 leads to a decrease in corrosion resistance. Resistance to SCC sharply decreases. Resistance to EXCO drops (EC estimation). The aforementioned regularities are confirmed by data obtained for semi products made of commercial alloys 1440 and 1450 (alloys nos. 8 and 9, respectively). Alloy no. 8 has sim ilar corrosion properties to alloy no. 4 (Tables 3, 5, 6) and a similar Li/Cu + Mg ratio. In alloy no. 9, the ratio of Li/Cu + Mg is 0.76 at rather high Cu/Mg = 16.6.

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This alloy has superior corrosion properties to those of alloy no. 8. The corrosion characteristics of alloy no. 9 can be adjusted by regimes of artificial aging, whereas the properties of alloy no. 8 can hardly be controlled in this manner. Development and propagation of corrosion cracks within testing of semiproducts for resistance to SCC has its peculiar features. Thus, Al–Li binary alloys in marine tropical atmosphere demonstrated sufficiently high corrosion resistance to pitting corrosion, and the rate of crack propagation is by an order of magnitude higher than that for conventional aluminum alloys. This is related to the peculiarities of interaction of strengthening and the electrically negative δ'(Al3Li) phase with dislocations. When dislocation passes through the (Al3Li)phase , an antiphase boundary is formed, which is eliminated by passing the second dis location. Therefore, accumulation of dislocations at subgrain boundaries increases, which promotes crack propagation. In the more complex alloys Al–Li–Cu and Al– Li–Cu–Mg, the phase composition differs from that of binary alloys, with additional phases appearing, which significantly increase the strength properties of the alloys. Propagation of corrosion cracks within tests of semiproducts for resistance to SCC occurs mainly between crystallites (along subgrain boundaries) (Fig. 7). It is highly probable that, in stress corrosion cracking of aluminum–lithium alloys, a significant role can be played by electrochemical factor due to precipitations of phase T1(Al2CuLi) at the grain boundary. Exactly these phases are responsible for variation of both strength characteristics and corro sion properties [26]. CONCLUSIONS 1. The corrosion resistance (SCC, EXCO, IGC) of numerous group of aluminum–lithium alloys has been studied under atmospheric conditions with vari ous levels of aggressiveness. With the aim of achieving correspondence, the atmospheric tests have been rep licated with accelerated tests. 2. It has been established that the highest level of aggressiveness is that of the marine tropics at the expo sure station in Cuba and on board the research vessel, with the least aggressive being the atmospheric condi tions of the VILS exposure station (the environment of an industrial district in Moscow). 3. Corrosion behavior of test and commercial batches of aluminum–lithium alloys has been estab lished as a function of chemical composition and the ratios of Cu/Mg and Li/Cu + Mg. Under atmospheric conditions, the best corrosion properties are those of the alloy with an Cu/Mg ratio of 0.5 and a Li/Cu + Mg ratio of 0.96. It has been proved that a decrease in

Li/Cu + Mg to 0.56–0.76 leads to decrease in corro sion properties. Accelerated tests have provided the same conclusions. 4. It has been found that the results of accelerated tests of resistance to EXCO and SCC of serially pro duces semiproducts made of alloys 1440 and 1450 cor relate satisfactory with atmospheric data only in natu rally and artificially aged states for maximum strength. In the overaged state, the results of laboratory tests have not been confirmed with fullscale results. 5. In order to arrange the results of accelerated tests of resistance to EXCO of semiproducts made of alumi num–lithium alloys in accordance with atmospheric data, it is necessary to the adjust chemical composi tion of solutions 2S and 4S in accordance with ISO 11881:1999. 6. Corrosion cracks propagate mainly intercrystal line; however, in the area of the mechanical break, the fracture pattern varies significantly from the conven tional alloys D16 and V95. The fracture in this area obtains a transcrystallite break. REFERENCES 1. Sinyavskiy, V.S. and Kalinin, V.D., Zashch. Met., 2007, vol. 43, no. 6, p. 631. 2. Sinyavskiy, V.S. and Ust’yantsev, V.U., Zashchita ot korrozii buril’nykh trub iz alyuminievykh splavov (Pro tection from Corrosion Drilling Tubes Made of Alu minium Alloys), Moscow: “Nedra”, 1976. 3. Fain, G.M., Shtamburg, V.F., and Danelyants, S.M., Neftyanye truby iz legkikh splavov (Petroleum Tubes Made of Light Alloys), Moscow: “Nedra”, 1990. 4. Sinyavskiy, V.S. and Kalinin, V.D., Tekhnologiya Legkikh splavov, 1997, no. 6, p. 15. 5. Fridlyander I.N., Kolobnev N.I. V sb. Aviatsionnye materialy na rubezhe XXXXI vv (Aviation Materials at the Turn of the 20th Century), Moscow: VIAM, 1994. 6. Davydov, V.G., Osobennosti Tekhnologii pri proizvod stve AlLi splavov. TL, no. 1, p. 5. 7. Babel, H., Gibson, J., Tarkanian, M., et al., Alumin iumLithium with KeyLocked Inserts for Aerospace Applications JMEPEG, 2007. 8. BoisBrochu, A., Tchitembo, GomaF.A., Blais, C., et al., Mechanical Properties, Microstructure and Tex ture Advance Materials Research, 2012, vol. 409, p. 29. 9. Giummarra, C., Bruce, Thomas., and Roberto, J., Rioja // proc. of lmt, Light Metals Technology, 2007. 10. Ahmad, Z. and Abdul, AleemB.J., J. Mater. Engineer ing and Performance, 1996, vol. 5. no. 2, p. 235. 11. Grimes, R., Cornish, A.J., Miller, W.S., and Reynolds, M.A., Aerospace Mater, 1985, no. 6, p. 57. 12. Dorward, R.C. and Hasse, K.R., Corrosion, 1988, vol. 44, no. 12, p. 932. 13. Batrakov, V.P., Karimova, S.A., and Komisarova, V.S., Zashch. Met., 1981, vol. 17, no. 6, p. 627. 14. Sinyavskiy, V.S. and Kalinin, V.D., Zashch. Met., 2005, vol. 41, no. 4, p. 347.

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CORROSION RESISTANCE OF ALUMINUM–LITHIUM ALLOYS 15. Kolotyrkin, Ya.M., Sinavsky, V.S., Kiselev, V.D., et al., 6th Int. Aluminum–Lithium Conf. Garmish– Partenkirchen (FRG). 1991. V. 2. P. 843. 16. Sinyavskiy, V.S., Semenov, A.M., and Valkov, V.D., Tekhnologiya Legkikh Splavov, 1991, no. 910, p. 12. 17. Semenov, A.M., Tekhnologiya Legkikh Splavov, 2010, no. 4, p. 86. 18. Semenov, A.M. and Sinyavskiy, V.S., Tekhnologiya Legkikh Splavov, 2009, no. 4, p. 95. 19. Sinyavskiy, V.S., Valkov, V.D., and Kalinin, V.D., Kor roziya i zashchita alyuminievykh splavov (Corrosion and Protection of Aluminum Alloys, Moscow: Metal lurgiya, 1986. 20. Thomas, K.C. and Allio, R.J., Nature, 1965, vol. 206, p. 82.

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