Quantification and modelling of the microstructure/strength relationship by tailoring the morphological parameters of the T1 phase in an Al-Cu-Li alloy

We present a systematic study of the relationship between precipitate microstructure and resulting yield strength in an Al-Cu-Li alloy. By varying the thermomechanical ageing treatments applied to the AA2198 alloy (pre-deformation, heat treatment temperature and duration), T 1 microstructural parameters (thickness, diameter and volume fraction) are varied over a wide range, and the corresponding yield strength is determined. The resulting database of microstructure-strength relationships is used to establish a strengthening model based on interfacial and stacking fault strengthening. This model successfully describes the strength evolution from under-aged to over-aged conditions without the need for a transition from precipitate shearing to by-passing.