الفهرس 
INTRODUCTION And Aim of the Work
Al AlloysOnly 14 pages are availabe for public view
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Abstract
In the present investigation, the precipitation hardening and the precipitation kinetics have been characterized during heating the studied Al-Li-based alloys. In order to attain the supersaturated solid solutions, the alloys Al-Li(2090) (Al-2.7wt.%Cu- 2.2wt.%Li- 0.12wt.%Zr) and Al-Li(AF/C489) (Al-2.7wt.%Cu- 2.1wt.%Li- 0.3wt%Mg- 0.3wt.%Mn- 0.6wt.%Zn-0.05wt.%Zr) were solution heat treated for 30 min at 803 K (corresponding to the single a-phase region in the equilibrium phase diagram) and then quenched into iced water (~ 273 K). As the supersaturated solid solutions are subjected to continuous or step heating, they will undergo structural transformations via formation of strengthening precipitates such as d`-precipitates. The growth and coarsening of the precipitates have been followed by SEM and TEM examinations. The obtained results of DSC and microhardness (HV) measurements were confirmed by X-ray diffraction (XRD).
from the obtained results, the following conclusions can be drawn:
1-from the behavior of the DSC as a function of temperature, it has been observed that the peak temperature corresponding to developed precipitates is shifted towards higher temperatures with increasing the heating rate, which implies that the developed precipitates are thermally activated.
2- The micro hardness behavior during iso-chronal annealing shows the same precipitation peaks.
3- The SEM and TEM examination revealed the developed precipitates are δ(AL3Li) phase, T1 (Al2CuLi), T2 (Al6CuLi 3) and T8 (Al7Cu4Li).