Sage Journals: Discover world-class research

Abstract

The emergence of lithium containing aluminium alloys as potential light metals for aircraft structures has engendered an unprecedented widespread interest aimed at improving their mechanical properties and studying their cyclic fatigue characteristics. The phenomenon of fatigue is environment sensitive and the alternating moisture conditions experienced by this candidate airframe material can be a handicap when designing for enhanced fatigue resistance. In this paper, the fatigue properties, deformation characteristics, and cyclic stress response of the commercial Al–Li–Cu–Mn and the experimental Al–Li–Mn and Al–Li–Cu–Mg–Zr alloys cycled to failure are compared over a range of plastic strain amplitudes in various environments, spanning the inert to the very aggressive. Abnormal plastic strain–fatigue life behaviour was observed for all the alloy systems and is attributed to differences in the distribution of deformation as a function of plastic strain amplitude and to change in the relative amounts of intergranular and transgranular fracture as a function of strain amplitude. Cyclic deformation was also observed to produce softening in the three alloys for most of their fatigue life. The softening is due to progressive loss of ordering contributions to hardening and is a mechanical and not an environmental effect.

MST/888

Get full access to this article

View all access options for this article.

References

SANDERS

T. H.

JR and STARKE

E. A.

JR (eds): ‘Aluminum—lithium alloys I: Proceedings of the first international confer-ence on aluminum—lithium alloys’, 1981, Warrendale, PA, The Metallurgical Society of AIME.

SANDERS

T. H.

, JR and E. A. STARKE, JR WO: ‘Aluminum—lithium alloys II: Proceedings of the second international conference on aluminum—lithium alloys’, 1984, Warrendale, PA, The Metallurgical Society of AIME.

BAKER

et al. (eds): ‘Aluminium—lithium alloys III’ (Proc. 3rd Int. Conf.); 1986, London, The Institute of Metals.

STARKE

E. A.

JR and SANDERS

T. H.

JR (eds): ‘Aluminium alloys: Their physical and mechanical properties’, 1986, London, EMAS.

Aluminum-Lithium Alloys IV: Proceedings of the Fourth International Conference on Aluminum-Lithium Alloys, Paris, France , 1987 (in press).

LEBARON

I. M.

: US Patent no. 2,381,219, Granted 1945.

STARKE

E. A.

, JR, T. H. SANDERS, JR, and PALMER

I. G.

: J. Met., 1980, 33, 24.

NESS

and RYUM

: Scr. Metall., 1981, 5, 987.

GALBRAITH

J. M.

, TOSTEN

M. H.

, and HOWELL

P. R.

: J. Mater. Sci., 1987, 22, 27.

10.

FENG

W. X.

, LIN

F. S.

, and STARKE

E. A.

, JR: Metall. Trans., 1984, 15A, 1209.

11.

CHEN

R. T.

and STARKE

E. A.

, JR: Mater. Sci. Eng., 1984, 67, 229.

12.

VASUDEVAN

A. K.

, BRETZ

P. E.

, MUELLER

L. N.

, and SURESH

: Mater. Sci. Eng., 1984, 64, 113.

13.

VASUDEVAN

A. K.

and SURESH

: Metall. Trans., 1985, 16A, 475.

14.

SRIVATSAN

T. S.

and COYNE

E. J.

, JR: Int. J. Fatigue, 1986, 8, (4), 201–208.

15.

MEYN

D. A.

: Trans. ASM, 1968, 61, 52.

16.

WEI

R. P.

: Int. J. Fract. Mech., 1968, 4, (2), 159.

17.

WEI

R. P.

and SIMMONS

G. W.

: Int. J. Fraet., 1981, 17, 235.

18.

LYNCH

S. P.

: in ‘Fatigue mechanisms’, (ed. Fong

J. T.

), STP 675, 174; 1979, Philadelphia, PA, ASTM.

19.

COYNE

E. J.

, JR, T. H. SANDERS, JR, and E. A. STARKE, JR: in Ref. 1, pp. 293-305.

20.

SRIVATSAN

T. S.

, YAMAGUCHI

, and STARKE

E. A.

, JR: Mater. Sci. Eng., 1986, 83, 87–107.

21.

YAN

B. D.

, FARRINGTON

G. C.

, and LAIRD

: Acta Metall., 1985, 33, (9), 1593.

22.

GYSLER

, CROOKS

R. E.

, and STARKE

E. A.

, nu in Ref. 1, pp. 263-270.

23.

RINICER

J. G.

, MAREK

, and SANDERS

T. H.

, JR: Mater. Sci. Eng., 1984, 64, 203–210.

24.

SRIVATSAN

T. S.

, COYNE

E. J.

JR , and STARKE

E. A.

, JR: J. Mater. Sci., 1986, 21, 1553–1560.

25.

BRESHNAHAN

K. M.

: MSc thesis, Georgia Institute of Tech-nology, Atlanta, GA, 1984.

26.

SANDOR

B. I.

: ‘Fundamentals of cyclic stress and strain’; 1972, Madison, WI, University of Wisconsin Press.

27.

TOMKINS

: Philos. Mag., 1968, 18, 1041–1049.

28.

SANDERS

R. E.

JR and STARKE

E. A.

, JR: Mater. Sci. Eng., 1977, 28, 53–63.

29.

SANDERS

T. H.

JR and STARKE

E. A.

, JR: Metall. Trans., 1976, 7A, 1107–1115.

30.

LIN

F. S.

and STARKE

E. A.

, JR: Mater. Sci. Eng., 1979, 39, 27–34.

31.

COFFIN

L. F.

JR : J. Mater., 1971, 6, 388.

32.

LUDTKA

G. M.

and LAUGHLIN

D. E.

: Metall. Trans., 1982, 13A, 411–416.

33.

SRIVATSAN

T. S.

, COYNE

E. J.

JR and STARKE

E. A.

JR : in ‘Microstructural science’, Vol. 13, (ed. Shiels

S. A.

et al.), 247–262; 1985, Metals Park, OH, ASM.

34.

BRESHNAHAN

K. M.

and STARKE

E. A.

, sic ‘The characteristics of the microstructure and mechanical properties of an ingotmetallurgy Al—Li—Cu—Mg—Zr—Ge alloy’, work performed at Georgia Institute of Technology, Atlanta, GA, 1984.

35.

COOK

R. H.

and SKELTON

R. P.

: Int. Metall. Rev., 1974, 19, 199.

36.

SANDERS

T. H.

, JR: ‘Factors influencing fracture toughness and other properties of aluminum—lithium alloys’, Final Report, Naval Air Development Command, Contract no. N62269-76-C-0271, Naval Air Systems Command, June 1979.

37.

FIELD

D. J.

, BUTLER

E. P.

, SCAMANS

G. M.

: in Ref. 1, p. 325.

38.

DIETER

G. E.

: ‘Mechanical metallurgy’, 2 edn; 1976, New York, McGraw-Hill.

39.

ABEL

and HAM

R. K.

: Ada Metall., 1966, 14, 1495.

40.

LYNCH

S. P.

and RYDER

D. A.

: Aluminium, 1973, 49, 141–146.

41.

FOURNIER

and PINEAU

: Metall. Trans., 1977, 8A, 1095–1105.

42.

SRIVATSAN

T. S.

: PhD thesis, Georgia Institute of Technology, Atlanta, GA, 1984.

43.

SRIVATSAN

T. S.

and COYNE

E. J.

, Mc Mater. Sci. Technol., 1987, 3, 130.

Micromechanisms governing fatigue behaviour of lithium containing aluminium alloys

Abstract

Get full access to this article

References