4^th International Aluminium Lithium Conference

J. Phys. Colloques 48 (1987) C3-457-C3-463
DOI: 10.1051/jphyscol:1987352

HIGH RESOLUTION TEM STUDY OF PRECIPITATES IN A RAPIDLY SOLIDIFIED Al-Li-Zr ALLOY

N.J. KIM¹, J.M. HOWE² et E.G. BODEN<sup>3

1</sup>  Metals and Ceramics Laboratory, Allied-Signal Incorporation, P.O. Box 1021 R, Morristown, NJ 07960, U.S.A.
²  Department of Metallurgical Engineering and Materials Science, Carnegie-Mellon University, Pittsburgh, PA 15213, U.S.A.
³  Applications Laboratory, Philips Electronic Instruments Incorporation, Mahwah, NJ 01430, U.S.A.

Abstract
In this investigation, high resolution transmission electron microscopy and image simulations are used to characterize the atomic structure, coherency and chemistry of δ' and A1₃Zr precipitates in a rapidly solidified Al-3.4Li-0.5Zr alloy. During aging, δ' precipitates around Al₃Zr while maintaining coherency across the interphase boundary. Coalescence occurs when δ' precipitates whose sublattices are in phase coarsen and impinge. On the other hand, δ' precipitates whose sublattices are antiphase appear not to coalesce and a layer of aluminum matrix exists between them. Deformation of the alloy results in a shearing of δ' precipitates which occurs in some cases, by multiple cross slip along intersecting (111) planes. Finally, the results suggest that there may be some incorporation of lithium in the Al₃Zr precipitates.