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The aluminium-lithium alloys are modern materials capable to present higher mechanical properties reported to specific gravity being from this point of view very interesting for aerospace industry. By means of optimal correlation's between the chemical composition, the mode of elaboration and casting, the conditions of plastic deformations and heat treatment, these alloys can present mechanical and plasticity properties comparable with those of the DURAL (2024) types, on the lower density conditions. In the paper are presented the results of the studies and experimental researches made upon some lithium-lithium based alloys of the 2090 type, supplementary alloyed with Ti, for the use in aerospace constructions. There are made structure and property researches on the cast semi-manufactured product, plastic deformed and respective heat-treated to obtain the maximum mechanical characteristics.

The experimental researches made to settle the behaviour at cold plastic deformation of Al-Li alloys used in aeronautical constructions was realized on anneal samples through upsetting, rolling, drawing and torsion methods. The aim of this paper is to determined the behaviour at cold plastic deformation and the maximum possible degree of deformation, until don't appear cracks, through these four methods presented above for some Al-Li base alloys. By examination of the results obtained through these methods, it was determined the maximum possible degree of deformation until don't appear cracks and the equations which describe the behaviour of the tested alloy to cold plastic deformation.

The aluminium alloys with lithium content of 2090 type represent metallic materials of high technical interest, with radical perspectives in the aeronautical and spatial industries and in other technical domains. These interest are due first of all to the special characteristics of reduced specific masses and of mechanical resistance obtained through alloying with Cu and Mg, and through complex heat treatments. The impurities and microadditions of alloying for the Al-Li system have a great influence on the structure and properties of these alloys and they determine decisively the hardening heat treatments results. The present paper includes studies and experimental researches of optical and electronic microscopy regarding some aluminium-lithium base alloys of 2090 type supplementary alloyed with Ti for the finishing of the structure and improve the properties of these alloys which are used in aeronautical constructions.