Effect of two-phase microstructure characteristics on high strain rate elastoplastic deformation of superalloys: A three-dimensional discrete dislocation dynamics study

The two-phase microstructure may bring excellent mechanical properties to materials such as superalloys used for advanced turbine engines. Experiments and continuum scale simulations focus on normal strain rate (<10¹ s⁻¹) deformation, while atomistic simulations focus on ultra-high strain rate (>10⁶ s⁻¹) deformation. The high strain rate regime in-between has attracted much less attention. In the present work, by developing a three-dimensional discrete dislocation dynamics with continuum description of two-phase microstructure, the effect of matrix channel, precipitate APB energy, precipitate volume fraction, matrix/precipitate coherent interface misfit on high strain rate (2 × 10³ s⁻¹) elastoplastic deformation of two-phase superalloys are systematically studied. The control variable approach of different two-phase microstructure characteristics, which is difficult to conduct in experiments, is strictly applied in the present work to reach quantitative simulations. The stress–strain response, evolution of dislocation density on each slip system, three-dimensional microstructure and three-dimensional stress field are analyzed in detailed to investigate the mechanisms behind. Some common elastoplastic features irrelevant to the distinction of two-phase microstructure characteristics, as well as some specific elastoplastic features closely relevant to different two-phase microstructure characteristics are revealed. The elastoplastic commonalities and distinctions between normal, high and ultra-high strain rates are also discussed. Some suggestion for improving the high temperature strength of superalloys is proposed.