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Abstract

In this study, multi-phase field and molecular dynamics simulations have been applied to study grain growth mechanisms on the nanoscale. In our multi-phase field model the combination of grain boundary expansion and vacancy diffusion has been considered, which realize experimental observations. The atomistic mechanism of boundary movement and the free volume redistribution during the growth process have been investigated using molecular dynamics simulations. According to the multi-phase field results, the linear growth process is due to the diffusion-limited motion of grain boundaries, which is temperature-dependent. In molecular dynamics simulations, a constant grain boundary velocity has also been observed. The activation energy of grain boundary motion in this regime has been determined to be on the order of one tenth of the self-diffusion activation energy, which is consistent with experimental data. Based on the simulation results, the transition from linear to normal grain growth is discussed in detail and diffusion-limited grain boundary motion is proposed as the transition criterion.