The 9th International Conference on Multiscale Materials Modeling

Presentation information

Symposium

N. Towards Experimentally Relevant Time Scales: Methods for Extending Atomistic Simulation Times and Their Applications in Material Science

[SY-N2] Symposium N-2

Wed. Oct 31, 2018 11:15 AM - 12:15 PM Room4

Chair: Erik Bitzek(FAU Erlangen-Nuernberg, Germany)

[SY-N2] Using free energy calculations and statistical mechanics to probe the brittle to ductile transition of bcc metals

Invited

Thomas Swinburne1 (1.CINaM, CNRS/Aix-Marseille Univ., France)

The fracture response of bcc metals is known to be controlled by dislocation mobility, which in turn is dependent on the slow, thermally activated nucleation of kink pairs on <111> screw dislocations. We present a general, efficient scheme to calculate free energy barriers in large crystalline systems[1] which we apply to the kink nucleation process, finding significant anharmonic contributions at low homologous temperatures. A statistical mechanical approach is then used to study kink-limited dislocation motion through a field of obstacles[2]. We identify a crossover obstacle density below which the activation energy for plastic flow is half the free energy barrier for kink pair nucleation. Our results show striking agreement with fracture experiments across a wide range of bcc metals and are applied to interpret experimental data on irradiation induced embrittlement.
[1] TD Swinburne and M-C Marinica, Physical Review Letters 120 (13), 135503
[2] TD Swinburne and SL Dudarev, Physical Review Materials 2 (7), 073608