The strain-rate dependence of the nanoindentation stress of gold at 300 K: A deformation kinetics-based approach

Indentation tests involving a constant-loading rate stage followed by a constant-load stage were performed on annealed and 20% cold-worked Au to investigate the effect of indentation depth and initial dislocation density on the indentation deformation process. The indentation strain rate data were analyzed in terms of an obstacle-limited dislocation glide mechanism. The apparent activation energy was of the order of 0.16 μb3 and was neither a function of initial indentation depth nor cold work. The results of Haasen plot activation analysis and direct transmission electron microscopy (TEM) observations indicate that more mechanical work must be applied during the constant-loading rate stage due to the large amount of work hardening compared with the constant-load stage where considerably more dislocation recovery occurs.