Rutile single-crystal surfaces, with (001) and (100) orientations, were indented with hemispherical indenters with radii of 13.5, 5 and 1.4μm. By converting the load-displacement data to nano-indentation stress-strain curves, together with microscopic post-indentation observations, it was concluded that in the (001) orientation, plastic deformation occurred by the activation of all four {101}<10¯1> slip systems. In the (100) orientation, only two of the four {101}<10¯1> slip systems, along with {100}<10¯1> slip, were activated. Because the four {101}<10¯1> slip systems in the (001) orientation intersected, the surface was harder and exhibited higher hardening rates after the nucleation of dislocations. The latter were manifested by pop-ins, some of which were large. The pop-in stresses were adequately described by Weibull statistics and were significantly higher for the (001) orientation. The elastic moduli, determined from spherical nano-indentation stiffness versus contact radii plots, were 349 and 229GPa for (001) and (100) orientations, respectively. Fully spontaneous reversible, stress-strain hysteretic curves, manifested only in the (100) orientation, were attributed to the to-and-fro motion of dislocations comprising incipient kink bands in the {100}<10¯1> slip system.

Microscale Deformation of (001) and (100) Rutile Single Crystals under Spherical Nanoindentation. Basu, S., Elshrief, O.A., Coward, R., Anasori, B., Barsoum, M.W.: Journal of Materials Research, 2012, 27[1], 53-63