Stress/strain aging mechanisms in Al alloys from first principles
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Lab of Nonferrous Materials of Ministry of Education, Central South University, Changsha 410083, China)
2. Key Lab of Nonferrous Materials of Ministry of Education, Central South University, Changsha 410083, China)
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