Failure mode and dynamic behavior of nanophase iron under compression

The compressive deformation behavior and failure mode of near full-density elemental Fe with an average grain size of 80 nm are studied. While body centered cubic (bcc) Fe is known to exhibit strong rate sensitivity, the tests indicate that strain rate sensitivity is weak in 80 nm Fe. This new observation can be attributed to the unusual deformation and failure modes in ultrafine grained and nanophase materials under compression. This deformation mode appears to bear close similarity to amorphous materials. Nanophase Fe also shows high strength, appreciable elongation to failure localized in shear bands, and no shear hardening. The deformation mode and rate sensitivity of the flow stress are strongly dependent on grain size.