Abstract:First-principles based calculations were carried out to explore the possible mechanisms of stress/strain aging in Al alloys. Potential effects of temperature and external stress/strain were evaluated on the solvus boundary of Al₃Sc in Al-Sc alloy, and the interface energy of Al/θ'''''''' in Al-Cu alloys. Results show that applying tensile strain/stress during conventional aging can significantly decrease the solubility entropy, by red-shifting the phonon DOS at high states. The resulted solvus boundary would shift up on the phase diagram, suggesting a reduced solubility limit and an increased maximum possible precipitation volume of Al₃Sc in Al-Sc alloy.Moreover, the applied strain/stress has different impacts on the formation energies of different orientated Al/θ'''''''' interfaces in Al-Cu alloys, which can be further exaggerated by the Poisson effect, and eventually affect the preferential precipitation orientation in Al-Cu alloy. Both mechanisms are expected to play important roles during stress/strain aging.

Key words: stress aging; solubility limit; interface energy; first-principles