Surface plasticity and dislocation structures in oxide ceramics subjected to shot peening

This study investigates the plastic deformation behaviors and dislocation structure evolutions of oxide single crystals (9.8 mol% Y 2 O 3 -stabilized ZrO 2 , Al 2 O 3 , and SrTiO 3 ) subjected to shot peening at room temperature with varying pressures and durations. The deformation behaviors and subsurface microstructures were characterized via atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Surface plasticity during shot peening was mediated by the activity of dislocations belonging to specific slip systems comparable to those operating in small-scale mechanical testing, such as micropillar compression, at quasistatic strain rates. The AFM and TEM observations indicated that the ZrO 2 specimens deformed through orientation-dependent slip mechanisms: {111}< 1 ¯ 01 > and {001}<110> slips dominated during shot peening to the (001) and (111) surfaces, respectively; the Al 2 O 3 (0001) surface primarily deformed via { 1 ¯ 102 }< 1 1 ¯ 01 > rhombohedral slip; and the SrTiO 3 (001) surface deformed via {101}< 1 ¯ 01 > slip. The dislocation densities in the subsurface regions increased to an order of 10 13 –10 14 m −2 after shot peening. The dislocations introduced through shot peening also improved the post-mechanical properties, as characterized by indentation techniques. Crack shortening and hardness increase were strongly correlated with a higher dislocation density, as indicated by XRD peak broadening under harsher shot peening conditions. These results highlight the possibility of plastic forming in oxide ceramics by accumulating small-scale deformation and emphasize the significance of dislocation engineering for improving their mechanical properties.