Modeling the temperature and high strain rate sensitivity in BCC iron: Atomistically informed multiscale dislocation dynamics simulations

Multiscale discrete dislocation plasticity (MDDP) simulations are carried out to investigate the mechanical response and microstructure evolution of single crystal BCC iron subjected to high strain rate compression over a wide range of temperature. The simulations are conducted at temperatures ranging between 300 K and 900 K and strain rate ranging between 10(2) to 10(7) s(-1). Atomistically informed generalized mobility law was incorporated in MDDP to account for the effects of temperature and strain rate on dislocation mobility, lattice friction and elastic constants. MDDP based constitutive equations interrelating temperature and strain rate with the flow stress at high strain rate shock-less and shock conditions are proposed. The simulation results of the temperature and strain rate dependent yield strength and Hugoniot elastic limit are in good agreement with reported experimental results. Detailed investigations of the dislocation microstructure evolution show the formation of extended screw dislocation lines at temperatures below 340 K due to the large value of the lattice friction of the pure screw segments. Moreover, small sessile loops of radius in the order of few nanometers are formed. The formation of these sessile loops is facilitated by the easiness of multiple cross slip on available slip planes.