Giant quasi-elastic responses in decomposed two-phase nanodispersions: Phase field modeling

Using the 3D and 2D computational prototyping of formation of precipitation hardened alloys with low symmetry (tetragonal) precipitates, we have demonstrated that coherent single-domain nano-precipitates of a low-symmetry phase can have low-hysteretic strain super responses to the applied fields and large blocking force. The modeling is based on the newly developed phase field theory of displacive transformations in strongly anharmonic decomposing alloys (Acta Mater 2011;59:4494). It is shown that the giant strain response is achieved by displacive field-induced anharmonic rotation of structural orientation of the domain state of the nanoprecipitates. The energy cost of such a rotation is described by structural anisotropy, a new concept proposed in that theory. The modeling is performed for the cases of low structural anisotropy. It is shown that in the limit case of vanishing structural anisotropy, special glass-like structural state with random orientation relations to the parent cubic phase is produced. The simulation results demonstrate special properties of precipitation hardened nanodispersions of the tetragonal phase and provide a guide for a development of this new class of super-responsive functional materials.