Strain bursts in plastically deforming molybdenum micro- and nanopillars

Abstract

Plastic deformation of micron and sub-micron scale specimens is characterized by intermittent sequences of large strain bursts (dislocation avalanches) which are separated by regions of near-elastic loading. In the present investigation we perform a statistical characterization of strain bursts observed in stress-controlled compressive deformation of monocrystalline molybdenum micropillars. We characterize the bursts in terms of the associated elongation increments and peak deformation rates, and demonstrate that these quantities follow power-law distributions that do not depend on specimen orientation or stress rate. We also investigate the statistics of stress increments in between the bursts, which are found to be Weibull distributed and exhibit a characteristic size effect. We discuss our findings in view of observations of deformation bursts in other materials, such as face-centred cubic and hexagonal metals.

Keywords:

• micropillars
• molybdenum
• dislocations
• nanomechanics
• plasticity of metals

Acknowledgements

We acknowledge support of the Commission of the European Communities under contract NEST-2005-PATH-COM-043386 and of EPSRC under Grant No. EP/E029825.