所属：Osaka University, Department of Mechanical Science and Bioengineering

概要：We have constructed an atomistically informed phase-field model for the quantitative energetic analysis of phase　transformations. In our model, to describe the general phase transformation with a non-linear correlation between　displacive and diffusive modes, we have defined two order parameters, and , which describe the lattice　distortion (displacive mode) and shuffling (diffusive mode), respectively. Our method provides a way to introduce　the energetics from atomistic simulations to the phase-field model, describes and in an atomic　model, and derives phase-field parameters from the free energy calculated by atomistic simulation. As an application　of our model, we used the energetics obtained from atomistic simulations using a density functional　theory potential, and we calculated the free energy change during the heterogeneous {101-2} twin migration of　hexagonally close-packed (HCP) Mg, which can be considered as a lattice distortion and shuffling mixed phase　transformation, by combining our phase-field model with the nudged elastic band method. The activation energy,　and the critical nucleus size of the heterogeneous {101-2} twin migration under a set stress were derived. The　critical c-axis tensile stress (athermal stress), at which the activation energy becomes zero, is consistent with the　experimental yield stress of {101-2} for the twinning deformation of HCP Mg nanopillars in tensile tests. The　critical nucleus size of the heterogeneous {101-2} twin migration is on the range of nanometers under several　hundred megapascals stress, which is consistent with the experimental observation of nanotwins.

論文掲載,発表実績:
（学術雑誌掲載論文）

• Akio Ishii, “Energetics of heterogeneous Mg{10-12} deformationtwinning migration using an atomisticallyinformed phase-field model”,Comput. Mater. Sci., 183, 109907, (2020).