Stress-dependent deformation behaviour in bulk nanocrystalline titanium-nickel alloys

In this study, the deformation mechanisms operating with stress in bulk nanocrystalline (NC) titanium-nickel with an average grain size below a critical size of 10-20 nm have been investigated. We demonstrate a sequential variation of the deformation mechanism from grain boundary (GB) sliding and grain rotation to grain growth and dislocation activity with the increase of the deformation stress. These deformation mechanisms are different from the previous understanding that below a critical grain size of 10-20 nm, GB sliding and grain rotation govern plastic deformation of NC materials.