Temperature-dependent nanoindentation and activation volume in high-purity body-centered cubic chromium

The thermally activated dislocation plasticity of body-centered cubic (BCC) metals is controlled by the nucleation of dislocation kink pairs at low temperatures. We probed this deformation mechanism with high-temperature nanoindentation in chromium using very fine temperature increments. The established kink pair nucleation models are modified for the high-temperature nanoindentation method and applied to characterize the deformation behavior of high-purity BCC chromium from room temperature to 698 K. The measured hardness, strain rate sensitivity, and apparent activation volume are compared with a modified kink-pair nucleation model based on Seeger’s work. A change in the apparent slip plane from {110} to {112} with increasing temperature is inferred from self-consistent predictions and experimental measurements of the hardness-dependent activation volume from temperature-dependent hardness measurements using the line tension model for kink-pair nucleation.