A statistical analysis was made of acoustic emission due to dislocation motion during the creep of single crystals. The acoustic waves provided an indirect measure of the inelastic energy which was dissipated during dislocation motion. Compression and torsion creep experiments indicated that viscoplastic deformation, even during steady-state (secondary) creep, was a complex and inhomogeneous process which was characterized by avalanches in the motion of dislocations. The distribution of the avalanche size (equivalent to acoustic wave amplitude or energy) was found to obey a power law, with a cut-off at large amplitudes which depended upon the creep stage. The results suggested that viscoplastic deformation might be described within the framework of non-equilibrium critical phenomena.

Complexity in Dislocation Dynamics - Experiments. J.Weiss, J.R.Grasso, M.C.Miguel, A.Vespignani, S.Zapperi: Materials Science and Engineering A, 2001, 309-310, 360-4