EXPERIMENTAL-STUDY OF STRESS-INDUCED LOCALIZED TRANSFORMATION PLASTICZONES IN TETRAGONAL ZIRCONIA POLYCRYSTALLINE CERAMICS

Stress-induced martensitic transformation plastic zones in ceria-stabi lized tetragonal zirconia polycrystalline ceramics (Ce-TZP), under loa ding conditions of uniaxial tension, compression, and three-point bend ing, are studied by experiments. The transformed monoclinic phase volu me fraction distribution and the corresponding plastic strain distribu tion and the surface morphology (surface uplift) are measured by means of moire interferometry, Raman microprobe spectroscopy, and the surfa ce measurement system. The experimental results from the above three k inds of specimens and methods consistently show that the stress-induce d transformation at room temperature of the above specimen is not unif orm within the transformation zone and that the plastic deformation is concentrated in some narrow band; i.e., macroscopic plastic flow loca lization proceeds during the initial stage of plastic deformation. Flo w localization phenomena are all observed in uniaxial tension, compres sion, and three-point bending specimens. Some implications of the flow localization to the constitutive modeling and toughening of transform ing thermoelastic polycrystalline ceramics are explored.