Sage Journals: Discover world-class research

Abstract

The effects of increasing lithium contents on precipitation and hardening mechanisms of 7075 Al–Zn–Mg–Cu alloy have been investigated. It is shown that low (0·7 wt-%) and high (2 wt-%) lithium additions change the precipitation sequence and the age hardening behaviour of the base alloy. In addition, the phases precipitated on aging of the base alloy, i.e. solute rich Guinier–Preston (GP) zone, η′, and η (MgZn₂), are completely suppressed. Instead, 7075–0·7Li aged at 120°C reveals the precipitation sequence: vacancy rich GP zone→T′→T ((AI,Zn)₄₉Mg₃₂), and 7075–2Li aged at both 120 and 160°C produces dominant δ′ (Al₃Li) and the limited and delayed formation of course T phase precipitates. Correspondingly, the age hardening response which is significant in 7075 alloy is decreased, especially for the 2%Li containing alloy for which a remarkably low age hardening efficiency in both natural aging and artificial aging was obtained. These results are interpreted in terms of the effect of preferential clustering of lithium atoms and vacancies on the initial clustering and nucleation mode. This clustering prevents the formation of solute rich GP zones by inhibiting diffusion of zone forming atoms into zones, thereby causing the modification or even change of composition, morphology, dispersion, and structure of subsequent precipitates.

MST/1776

Get full access to this article

View all access options for this article.

References

DEAN

W. A.

: ‘Aluminium’, Vol. 1, ‘Properties, physical metallurgy and phase diagrams’, 163; 1967, Metals Park, OH, ASM.

SANKARAN

K. K.

and GRANT

N. J.

: Mater. Sci. Eng., 1980, 44, 213.

PALMER

I. G.

, LEWIS

R. E.

, and CROOKS

D. D.

: in ‘Aluminium—lithium alloys’, (ed. Sanders

T. H.

Jr and Starke

E. A.

, Jr) 205; 1981, Warrendale, PA, The Metallurgical Society of AIME.

JONES

W. R. D.

and DAS

P. P.

: J. Inst. Met., 1959-1960, 88, 435.

SANDERS

T. H.

and BALMUTH

E. S.

: Met. Prog., 1978, 113, 32.

SANDERS

T. H.

, LUDWICZAK

E. A.

, and SAWTELL

R. R.

: Mater. Sci. Eng., 1980, 43, (1), 247.

GAYLE

E W.

: in Aluminium—lithium alloys’, (ed. Sanders

T. H.

Jr and Starke

E. A.

Jr ), 119; 1981, Warrendale, PA, The Metallurgical Society of AIME.

SANKARAN

K. K.

, SASTRY

S. M. L.

, and O'NEAL

J. E.

: in Aluminium—lithium alloys’, (ed. Sanders

T. H.

Jr and Starke

E. A.

Jr ), 189; 1981, Warrendale, PA, The Metallurgical Society of AIME.

GYSLER

, CROOKS

, and STARKE

E. A.

, Jr: in ‘Aluminium—lithium alloys’, (ed. Sanders

T. H.

Jr and Starke

E. A.

Jr ), 263; 1981, Warrendale, PA, The Metallurgical Society of AIME.

10.

STARKE

E. A.

, Jr, T. II. SANDERS, Jr, and PALMER

I. G.

: J. Met., 1981, 33, 24.

11.

PALMER

I. G.

, LEWIS

R. E.

, and CROOKS

D. D.

: in Proc. Conf. on ‘High strength PM aluminium alloys’, (ed. Koczak

M. J.

and Hildeman

G. H.

), 396; 1982, Warrendale, PA, The Metallurgical Society of AIME.

12.

BAUMANN

S. F.

and WILLIAMS

D. B.

: in Aluminium—lithium alloys II’ (ed. Sanders

T. H.

Jr and Starke

E. A.

Jr ), 17; 1983, Warrendale, PA, The Metallurgical Society of AIME.

13.

GREGSON

P. J.

and FLOWER

H. M.

: Acta Metall., 1985, 33, 527.

14.

WHITE

, MILLER

W. S.

, PALMER

I. G.

, DAVIS

, and SAIN

T. S.

: in Aluminium—lithium alloys III’, (ed. C. Baker, P. J. Gregson, S. J. Harris, and C. J. Peel), 530; 1986, London, The Institute of Metals.

15.

CASSADA

W. A.

, SHIFLET

G. J.

, and STARKE

E. A.

, Jr: Acta Metall., 1986, 34, 367.

16.

POLMEAR

I. J.

and SCOTT-YOUNG

: J. Inst. Met., 1958-1959, 87, 65.

17.

THOMAS

and NUTTING

: J. Inst. Met., 1959-1960, 88, 81.

18.

STALEY

J. T.

, BROWN

R. H.

, and SCHMIDT

: Metall: Trans., 1972, 3, 191.

19.

STALEY

J. T.

: Metall. Trans., 1974, 5, 929.

20.

LLOYD

D. J.

and CHATURVEDI

M. C.

: J. Mater. Sci., 1983, 17, 1819.

21.

ADLER

P. N.

, DELASI

, and GESCHWIND

: Metall. Trans., 1972, 3, 3191.

22.

DANN

N. C.

, RAJAN

, and WALLACE

: Metall. Trans., 1983, 14A, 1843.

23.

PARK

J. K.

and ARDELL

A. J.

: Metall. Trans., 1973, 4, 1957.

24.

ASHBY

M. E

and BROWN

L. M.

: Philos. Mag., 1963, 8, 1649.

25.

LYMAN

C. E.

and VANDERSANDE

J. B.

: Metall. Trans., 1976, 7A, 1211.

26.

ORTNER

S. R.

, GROVENOR

C. R. M.

, and SHOLLOCK

B. A.

: Scr. Metall., 1988, 22, 839.

27.

MONDOLFO

L. E

, GJOSTEIN

N. A.

, and LEVINSON

D. W.

: Trans. AIME, 1956, 206, 1378.

28.

AULD

J. H.

and McK

. COUSLAND: J. Aust. Inst. Met., 1974, 19, 194.

29.

GJONNES

and SIMENSEN

Chr J.

: Acta Metall., 1970, 18, 881.

30.

THOMAS

A. T.

: J. Inst. Met., 1967, 95, 92.

31.

THACKERY

P. A.

: J. Inst. Met., 1968, 96, 228.

32.

DeARDO

A. J.

, Jr and Chr. J. SIMENSEN: Metall. Trans., 1973, 4, 2413.

33.

HUANG

z. W.

: PhD thesis, The University of Birmingham, 1991.

34.

CORNISH

A. J.

and DAY

M. K. B.

: J. Inst. Met., 1969, 97, 44.

35.

MONDOLFO

L. F.

: J. Inst. Met., 1969, 97, 95.

36.

THACKERY

P. A.

and THOMAS

A. T.

: J. Inst. Met., 1971, 99, 114.

37.

CORNISH

A. J.

and DAY

M. K. B.

: J. Inst. Met., 1971, 99, 377.

38.

BERNOLE

and GRAF

: Mém. Étud. Sci. Rev. Métall., 1972, 69, 123.

39.

BERNOLE

and GRAF

: Métn. Étud. Sci. Rev. Métall., 1974, 71, 259.

40.

AULD

J. H.

and McK

. COUSLAND: Met. Sci., 1976, 10, 445.

41.

AULD

J. H.

and WILLIAMS

B. E.

: Acta Crystallogr., 1966, 21, 830.

42.

BERGMAN

, WANGH

J. L. T.

, and PAULING

: Acta Crystallogr., 1957, 10, 254.

43.

RYUM

: Z. Metallkd., 1975, 66, 377.

44.

MONDOLFO

L. F.

: ‘Aluminium alloys: structure and properties’, 581; 1976, London, Butterworths.

45.

HUANG

Z. W.

, LORETTO

M. H.

, SMALLMAN

R. E.

, and WHITE

: Acta Metall., to be published.

46.

DELASI

and ADLER

P. N.

: Metall. Trans., 1977, 8A, 1177.

47.

DELASI

and ADLER

P. N.

: Metall. Trans., 1977, 8A, 1185.

48.

NAESS

S. E.

: Scr. Metall., 1969, 3, 179.

49.

JURGENS

, KEMPE

, and LOFFLER

: Phys. Status Solidi (a), 1974, 21, K39.

50.

JURGENS

, KEMPE

, and LOFFLER

: Phys. Status Solidi (a), 1974, 25, K73.

51.

SUZUKI

, ASAMI

, and KANNO

: J. Jpn Inst. Light Met., 1972, 22, 52.

52.

GROMA

and SZENTIRMAY

: Scr. Metall., 1978, 12, 991.

53.

‘Physical metallurgy’ , 3 rev, and enlarged edn, (ed. Cahn

R. W.

and Haasen

, 198; 1983, Amsterdam, North-Holland.

54.

NICHOLSON

R. B.

, THOMAS

, and NUTTING

: J. Inst. Met., 1958-1959, 87, 429.

55.

ASANO

and HIRANO

: Trans. Jpn Inst. Met., 1968, 9, 149.

56.

SMITH

W. E

and GRANT

N. J.

: Metall. Trans., 1970, 1, 979.

57.

GROVE

C. A.

and JUDD

: Metall. Trans., 1973, 4, 1023.

58.

HIRSCH

P. B.

: J. Inst. Met., 1960-1961, 89, 303.

59.

HUANG

Z. W.

, SMALLMAN

R. E.

, LORETTO

M. H.

, and WHITE

: Mater. Sci. Technol., 1991, 7, 205.

60.

SCHMALZRIED

and GEROLD

: Z. Metallkd., 1958, 49, 291.

61.

LOFFLER

, KOVACS

, and LENDVAI

: J. Mater. Sci., 1983, 18, 2215.

62.

MONDOLFO

L. F.

: Metall. Rev., 1971, 5, 95.

63.

RYUM

: Z. Metallkd., 1975, 66, 338.

Influence of lithium additions on precipitation and age hardening of 7075 alloy

Abstract

Get full access to this article

References