Zohreh Ebrahimi - Assistant Professr, Department of Mechanical Engineering, Payame Noor University, PO BOX ۱۹۳۹۵- ۳۶۹۷ Tehran, Iran

In this paper, a phase-field model is utilized to investigate the nano-structural evolution of 3 Al Sc precipitates in an Al-Sc system. We study the elastic contributions arising during the precipitation of nano-scale 3 Al Sc phase-particles. Since the precipitates of 3 Al Sc phase are fully coherent to the Al matrix, the elastic energy will have an influence on the resulting nono-structure. In the phase-field concept the interfacial conditions are avoided by introducing a set of smooth variables, the so-called phase-field variables, which characterize time and spacial evolutions of bulk phases in the underlying system. The elastic stresses and strains, during the shape evolution of 3 Al Sc phase, are investigated by solving the mechanical equilibrium equations together with the phase-field equations. We have observed that the simulated nano-structures evolve from a spherical to cubic shapes. The equilibrium shape of the coherent phase was found to be determined by minimizing the sum of the elastic and interfacial energies through the phase-field equations. A coherency loss is detected when the size of precipitates reaches about 40 nm in diameter. Finally, the effects of elastic interactions on shape evolution of nano-structuralevolution of 3 Al Sc precipitates are investigated.

Al3 Sc precipitate, elastic energy, phase-field model, nano-structural evolution