The possibility of extracting the strain rate sensitivity, activation volume and Helmholtz free energy (for dislocation activation) using just one indentation stress relaxation test was presened, and the approach was demonstrated using polycrystalline copper. The Helmholtz free energy measured from indentation relaxation agrees well with that from the conventional compression relaxation test, which validates the proposed approach. From the indentation relaxation test, the measured indentation strain rate sensitivity exponent was found to be slightly larger, and the indentation activation volume much smaller, than their counterparts from the compression test. The results indicate the involvement of multiple dislocation mechanisms in the indentation test.

Characterization of Strain Rate Sensitivity and Activation Volume using the Indentation Relaxation Test. B.Xu, Z.Yue, X.Chen: Journal of Physics D, 2010, 43[24], 245401