Indentation power-law creep of high-purity indium

Using a variety of depth-sensing indentation techniques, the creep response of high-purity indium, from room temperature to 75 degrees C, was measured. The dependence of the hardness on the variables of indentation strain rate (stress exponent for creep (n)) and temperature (apparent activation energy for creep (Q)) and the existence of a steady-state behavior in an indentation test with a Berkovich indenter were investigated. It was shown for the first time that the indentation strain rate ((h) over dot/h) could be held constant during an experiment using a Berkovich indenter, by maintaining the loading rate divided by the load ((P) over dot/P) constant. The apparent activation energy for indentation creep was found to be 78 kJ/mol, in accord with the activation energy for self-diffusion in the material. Finally, by performing (P) over dot/P change experiments, it was shown that a steady-state path independent of hardness could be reached in an indentation test with a geometrically similar indenter.