Experimental (TEM and STEM) investigation and theoretical approach to the fatigue-induced dissolution of δ′ precipitates in a 2.5 wt% Al-Li alloy

The fatigue microstructure of an Al-2.5 wt%Li alloy with small δ' precipitates has been investigated both by TEM and STEM (nanodiffraction and electron energy-loss spectroscopy). Specific features of strain localization have been evidenced which are made of lithium-depleted precipitate-free bands. A model is proposed to explain the redissolution of δ' precipitates inside the bands, based on an increase of their free energy due to shear-induced antiphase boundaries.