[SY-E9] Symposium E-9

[SY-E9] The motion of a single dislocation from molecular dynamics simulations and its physical interpretation

Invited

^○Yujie Wei^1,2, Shenyou Peng^1,2 (1.Chinese Academy of Sciences, China, 2.School of Engineering Sciences, University of Chinese Academy of Sciences, China)

The dependence of dislocation mobility on stress is the fundamental ingredient for the deformation in crystalline materials. Strength and ductility, the two most important properties characterizing mechanical behavior of crystalline metals, are in general governed by dislocation motion. Experimentally, recording the position of a moving dislocation in a short time window is still challenging, and direct observation to deduce the speed-stress relationship of dislocations is still missing. Here we report the motion of an obstacle-free twinning partial dislocation in face centred cubic crystals with spatial resolution at the angstrom scale and temporal picosecond temporal information. The dislocation exhibits two limiting speeds: The first is subsonic and occurs when the resolved shear stress is on the order of hundreds of megapascal. While the stress is raised to gigapascal level, an abrupt jump of dislocation velocity occurs, from subsonic to supersonic regime. The two speed limits are governed respectively by the local transverse and longitudinal phonons associated with the stressed dislocation, as the two types of phonons influence dislocation gliding at different stress levels. In contrast, the kinetics of a screw dislocation is distinct from that of edges. We demonstrate that a screw dislocation can move steadily at the speed of shear wave velocity, or even move supersonically.