Temperature dependence of plastic instability in Al alloys: A nanoindentation study

Abstract

An elevated temperature nanoindentation based method for characterizing the thermal dependence of plastic instability and assessing the activation energies associated with the phenomenon in Al alloys is presented in this work. The method exploits the nanoscale force–displacement resolution capabilities of the Nanoindenter, precludes the ambiguities inherent in the uniaxial testing based methods and offers increased reliability because of the statistical significance of the data achieved. The activation energies estimated for an Al—Mg and an Al—Li alloy with the proposed method were found to be 0.59 ± 0.07 eV and 0.72 ± 0.01 eV, respectively, and are consistent with values derived with other methods. The rate controlling mechanisms associated with these activation energies are described in terms of existing models for plastic instability in these alloy systems.