A direct comparison of high temperature nanoindentation creep and uniaxial creep measurements for commercial purity aluminum

Abstract

Measuring the uniaxial creep response from nanoindentation has been of great interest to the small scale mechanics community. However, several experimental and modeling challenges pose obstacles to direct comparison of indentation and uniaxial results. In this work, new experimental procedures are developed to improve the precision and accuracy of high temperature nanoindentation tests. Indentation creep experiments are performed on commercial purity aluminum alloy at a number of temperatures up to 550 °C. The activation energy for creep was found to be 140.2KJ/mol/K, matching the value determined with high temperature uniaxial creep experiments extremely well. Uniaxial power-law creep parameters (stress exponent and pre-exponential term) are calculated from the indentation data for direct comparison of results to the uniaxial data. The results are in good agreement with the literature values for uniaxial compression/torsion tests over a wide range of strain rates and temperatures demonstrating the capabilities of high temperature indentation creep experiments. The relative contributions and interplay of indentation size effect, strain rate and temperature on the creep response is also explored.