In this book, the microstructural evolution of aging strengthened aluminum alloy was simulated by using micro and continuous phase field models at atomic and mesoscopic scales respectively. Firstly, the segregation of solute atoms at grain boundarie (GB), cluster nucleation and structural transformation of ordered/disordered precipitated phase precursors in Al-Cu alloy were simulated by using microscopic phase field. Then, a multi-phase field model was developed to describe the evolution of aging precipitates in Al-Mg-Si alloy. The growth of β'' precipitates with the strongest aging strengthening benefit in Al-Mg-Si alloy was quantitatively simulated by coupling CALPHAD (calculation of phase diagram) database. The effects of different volume fraction, morphological and size of precipitated particles on grain growth were investigated by using continuous phase field model. Finally, the plastic deformation mechanism of polycrystalline materials with different scales under external force is studied.