Elastic Modulus of Al-Li Alloys.

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Lithium containing aluminum alloys have a potential importance as new alloys for aeronautical applications with high rigidity and low density. In the peresent work, measurements of the elastic modulus were made of such alloy systems as Al-Li, Al-Mg,and Al-Li-Mg that are the basic systems for the development of practical Al-Li alloys. The results are summarized as follows:(1) The single addition of Li to Al up to 14at% increases both the young's modulus(E) and the shear modulus(G) of Al. The young'.s modulus of the binary Al-Li solid solution is expressed by an empirical equation, E _<(Al-Li)> = 73 + 0.9 C _<Li> (GPa) where the Young's modulus of pure Al is 73 GPa, and C _<Li> is the at % of Li.(2) The single addition of Mg to Al up to 6 at% decreases, slightly but linearly with the Mg concentration, both E and G. The Young's modulus of the binary Al-Mg alloy is expressed by the following empirical equation, E (_<Al-Mg>) = 73 - 0.1 C _<Mg> (GPa) where C _<Mg> is the atomic % of Mg.(3) Among the intermetallic compounds that appear in the binary or ternary alloy systems, '-Al_3 Li phase has a tendency to increases both E and G of Al but the effects of T-Al _2 LiMg phase is negligible.(4) The effects of the complex addition of Li and Mg, within the solid solubility limits, seem to be additive, implying a negligible interaction between Li and Mg.(5) A large increase of the shear modulus(G) of Al by the addition of Li substantiates the possible stroung elastic interaction due to the modulus effects between the moving dislocations and the solute(Li) atmosphere, which successfully explain the observed high temperature strength of the solid solution Al-Li alloys.