Microscopic Phase-field Simulation Of Binary Alloys Precipitation Process

The precipitation process of binary model system was simulated using microscopic phase-field method. The precipitation process without coherent elastic strain was simulated firstly; the effects of alloy composition and aging temperature on precipitation were studied emphatically. Based on which the precipitation process under coherent elastic strain was simulated combining with microscopic elasticity mechanical theory. The precipitation of Al-Cu alloys was simulated at last, with the effective interaction energy calculated by Quasichemical method and Electronegativity method.In the case of precipitation without coherent elastic strain, the precipitation mechanism of precipitated phase was non-classical nucleation, the morphology was isotropic sphericity. The lower the alloy concentration and the aging temperature, the longer the nucleation incubation period, the slower the rate of nucleation and growth, the longer the time of the number of precipitations achieving maximum, the disperser the size distribution of precipitation phase, the faster the rate of coursing.When the coherent elastic strain energy was considered, the precipitation phase separated out along the elastically soft directions, the shape changed from sphericity to short bar. The bigger the absolute of elastic strain energy, the shorter the nucleation incubation period, the more the number of crystal nucleus, the bigger the slenderness of precipitation phase, the faster the rate of coursing. When the alloys composition is low and the elastic strain energy is big, GP zone can be formed.In the case of Al-Cu alloy, the GP zone first separated out along {100} crystal plane, its morphology is disk and the thickness is bout 1 atom layer, then the GP zone grown up along the separated direction, when the diameter of the disk arriving 15 atom, the neighboring precipitation phase connected at the corner and formedθ′phase. The higher the aging temperature, the longer the nucleation incubation period, the slower the precipitation process. When the aging temperature is 190?C, the structure of the precipitation phase is ordered, similar with GP II zone.