Role of vacancies in coprecipitation of δ′ – and S–phasesin Al–Li–Cu

Abstract

Precipitation reactions in a series of Al–Li–Cu–Mg alloys, encompassing the composition ranges of the commercial Lital A and Lital B materials, have been studied to determine the role of solute and vacancy concentrations on homogeneous S-phase (Al₂CuMg) precipitation. Homogeneous precipitation of S-phase only occurs when a critical combination of free vacancy and copper and magnesium supersaturation is achieved. Lithium reduces the free-vacancy concentration by strong binding between vacancies and lithium atoms or atom clusters. Precipitation of δ′ (Al₃ Li) releases the bound vacancies and thereby promotes S-phase formation and, in extreme cases, vacancy condensation, producing dislocation loops.

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References

NOBLE

and THOMPSON

G. E.

: Met. Sci., 1971, 5, 114.

GREGSON

P. J.

and FLOWER

H. M

: Acta Metall., 1985, 33, 527.

WILLIAMS

O. B.

and EDINGTON

J. W.

: Met. Sci., 1975, 9, 529.

B. P.

, LIEDL

G. L.

, KULWICKI

J. H.

, and SANDERS

T. H.

: Mater. Sci. Eng., 1985, 70, 217.

GAYLE

F. W.

and SANDE

J. B. VANDER

: Scripta Metall., 1984, 18, 473.

GREGSON

P.I.

and FLOWER

H. M.

: J. Mater. Sci. Lett., 1984, 3, 829.

MAKIN

P. L.

and RALPH

: J. Mater. Sci., 1984, 19, 3835.

BAUMANN

S. F.

and WILLIAMS

D. B.

: Scripta Metall., 1984, 18, 611.

BAUMANN

S. F.

and WILLIAMS

D. B.

: ACta Metall., 1985, 33, 1069.

10.

FOX

, McDARMAID

D. S.

, and FLOWER

H. M.

: in ‘Al-Li alloys’, (ed. Baker

et al.), 263-272; 1986, London, The Institute of Metals.

11.

WEATHERLY

G. C.

: PhD thesis, Cambridge University, 1966.

12.

PEEL

C. J.

et al.: Proc. 2nd Int. Conf. on ‘Al-Li alloys’, 1983, The Metallurgical Society of AIME, 363.

13.

GREGSON

P. J.

, PEEL

C. J.

, and EVANS

: in ‘Al-Li alloys’, (ed. Baker

et al.), 516-523; 1986, London, The Institute of Metals.

14.

GRIMES

, CORNISH

A. J.

, MILLER

W. S.

, and REYNOLDS

M. A.

: Met. Mater., 1985, 1, 357.

15.

RAMAN

K. S.

: Scripta Metall., 1971, 5, 791.

16.

CERESARA

, GIARDA

, and SANCHEZ

: Philos. Mag., 1977, 35, 97.

17.

LORIMER

G. W.

and NICHOLSON

R. B.

: ‘The mechanism of phase transformations in crystalline solids’, 1969; 36, London, The Institute of Metals.

18.

UNWIN

P. N. T.

, LORIMER

G. W.

, and NICHOLSON

R. B.

: Acta Metall., 1969, 17, 1363.

19.

PIKE

: Personal communication, University of Reading, 1985.

Role of vacancies in coprecipitation of δ′ – and S–phasesin Al–Li–Cu–Mg alloys

Abstract

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