A transition of the deformation mode, from shearing to Orowan looping, was investigated in ternary Al-2.0Li-0.4wt%Ag single crystals by means of transmission electron microscopy. The critical loop size which corresponded to the critical planar particle size for the transition and the dislocation pair spacing were particularly small when compared with those in an Al-Li binary single crystal. The antiphase boundary energy of the δ' phase was correspondingly large (about 123mJ/m2) when compared with that for a binary crystal (about 100mJ/m2). The marked increase in the antiphase boundary energy of the δ' phase in a Ag-containing crystal was suggested to be due to a significant enrichment of the δ' phase with Ag.

Transition Behaviour of Deformation Mode from Shearing to Looping in an Al-Li-Ag Ternary Single Crystal. B.C.Lee, J.K.Park: Philosophical Magazine Letters, 1997, 76[6], 383-9