Experimental Evidence that the Onset of Mechanical Softening in Nanocrystalline Metals is Strain Rate Dependent

摘要

This paper reports on the influence of strain rate on the onset of mechanical softening of nanocrystalline gold at room temperature. Micro-tensile testing was performed with applied strain rates on the order of 10~(-4) s~(-1) to 10~(-6) s~(-1). Our results indicated that above a strain rate of 1.5 × 10~(-4) s~(-1) plastic deformation appeared to be dominated by dislocation processes and at rates below this influenced by one or more other deformation mechanisms in an increasing fashion. Furthermore, the data suggested that the critical grain size for inverse Hall-Petch behavior was strain rate sensitive.