The effect of microstructure as a consequence of precipitation aging on the fracture behavior, deformation mechanisms, mechanical properties, and microstructures of aluminum-lithium was studied. The alloy studied was an aluminum-lithium-zirconium alloy. The precipitation response with aging time and temperature was studies in order to correlate the deformation response to the alloys to the heat treating, microstructure, and fracture surface characteristics and features. The primary focus of this study was to relate the variation in ductility with aging to the microstructural parameters and fracture mechanisms. An aluminum alloy containing 2.6wt.%Li and 0.09wt.% Zr exhibited very low tensile ductility consistently prior to the peak-aged strength independent of thermal treatment. A transition was characterized by very low ductility in the slightly underaged condition up to the near peak-aged condition, then followed by a substantial increase in ductility with aging after the peak-aged treatment. Based on the quantitative microscopy of the size of the precipitates, it was proposed that the increase in the ductility of the alloy after aging was a consequence of particle coarsening with aging and resulting in Orowan looping due to the transition from dislocation particle shearing to dislocation particle bypassing with increasing precipitate size. As the interparticle spacing increased with overaging, and the dislocations were impeded by and thus bypassed the larger particles, the amount of plastic deformation increased as was reflected by the strength and ductility experimental data.
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- Effect of Aging on the Microstructure and Fracture of Aluminum-Lithium
J. M. Fragomeni
- Springer Netherlands
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