Strengthening mechanisms of iron micropillars

Abstract

We examine the size effect and strengthening mechanisms of bcc iron pillars. The single-crystal pillars were machined with focused ion beam and tested with a nanoindentation device with the compression axis along the $〈0,,0,,1〉$ crystallographic direction. We compare our test results with both older literature on whiskers and micro/macro specimens, and recent results from atomistic modelling. We find that the obtained results can be explained on the basis of current theories based on small-scale plasticity.

Keywords:

• SEM
• FIB
• pillar compression testing
• deformation mechanisms
• plastic deformation
• micromechanics
• size effect
• bcc iron

Acknowledgements

The authors would like to thank Dr Inga Gudem Ringdalen from SINTEF and Dr Afrooz Barnoush from NTNU for interesting discussions. We further acknowledge the cooperation with Saarland University in Germany for assistance and help with heat-treatment and electropolishing of samples. One of the authors (B.R.S. Rogne) wishes to thank NTNU for the funding of his PhD work. The Research Council of Norway is acknowledged for the support to the Norwegian Micro- and NanoFabrication Facility, NorFab (197411/V30).