shape AlTi, which have the roll of nucleus of crystallization with action of finishing of casting Microst 
structure Alloys 
Conclusions 
The studies and microstructural researches about the strengthening mechanism through precipitation Ivan A 
of Al-Li based alloys realised through DSC, TEM, HREM and CRSS methods settled that this 
mechanism take place as follows: ou sol.sol. = G-P zone — 8’ (Al:Li) — 7” (ALi). Fal 
I: 
The initial process is a quickly ordering followed by a lent decomposition of ol oversaturation 
solid solution. In the ordered matrix take place the homogeneous process of 6’ phase germination, 
which influence the mechanical characteristics. The ordered matrix and the AlLi (8°) precipitate Abstracı 
allow the development of the process of planar slight which start after the quenching. 
Comet: 
The effects of strengthening produced by 8 phase on underaged alloys is main owned to the of rare car 
hardening phenomenon through ordering. the interna 
internal 0 
resulted n 
temperatul 
References diem 
(1) D.B. Williams: “Aluminium-Lithium”, TMS-AIME (1981) 89. damen} 
(2) T.H.Jr. Sanders, E.A.Jr. Starke: ““Aluminium-Lithium”, TMS-AIME (1984) 1. van) 
(3) W. Lacom: J. Mater. Scie. Forum 13/14 (1987), 69-84. oo 
(4) S. Ceresara, A. Giarda: Philosophical Magazine 35 (1977), 97. Ny 
(5) B.J Shain, HT. Li, HY. Lee, H. Chen: Metallurgical Transaction A 21 (1990), 1133. al 
(6) W.A. Soffa, D.E. Lauglin: “Solid-Solid Phase Transformation”, AIME Acta Metalurgica 37 or 
(1989), 3019 
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