Abstract: The effect of Li addition on the aging behavior and mechanical properties of an Al Mg Si alloy has been investigated. An Li v model has been suggested to explain the modifications caused by the Li addition. According to this mechanism, the preferential clustering of Li and vacancies inhibits the formation of dislocation loops and diffusion of Si and Mg atoms, so that the precipitation of G.P. zones is limited and delayed. Consequently, the ordered δ' phase becomes the predominant precipitate, and Mg 2Si phase can form only after aging for very long time. Furthermore, the effect of thermomechanical aging (TMA) on microstructure and properties of an Al Li Mg Si alloy has been carried out too. It has been found that TMA accelerates the aging reaction and peak strength of the Al Li Mg Si alloy greatly. The TMA improves the strength of Al Li Mg Si significantly, and does not destroy the elongation. Al Li Mg Si alloy has a bright applying prospect for it shows comparable strength and elongation with Al Mg Si alloys after TMA, but it possesses a lower density and higher modulus.

Key words: A l-L i-M g-Si alloys, TMA, mechanical p ropert ies, m icro st ructures