INVESTIGATION OF THE STRUCTURAL TRANSFORMATIONS IN THE AL-LI-CU-MG(8090) ALLOY

The precipitation processes in quenched Al-2.4Li-1.16Cu-0.8Mg(wt.%) al loy (8090) from the solid solution stare (T-q = 803 K) have been inves tigated via the Vickers microhardness measurements, scanning electron microscopy and differential scanning calorimetry. On the basis of Kiss inger's analytical equation of the DSC thermograms, the overall activa tion energies associated with the transformation processes are evaluat ed. The activation energy associated with the formation of the GPB zon es and delta' phase is determined as 82.433 kJ/mol. Whereas the energy of their dissolution is 139.78 kJ/mol. The activation energy associat ed with the formation of the S' phase is determined as 106.88 kJ/mol. In addition, the microstructural examination of the samples after vari ous aging temperatures revealed that the resultant precipitates are in tergranular.