EXPERIMENTAL INVESTIGATION OF THE TRANSFORMATION ZONE OF TETRAGONAL ZIRCONIA POLYCRYSTALLINE CERAMICS

Stress-induced martensitic transformation plastic zones of ceria-stabi lized tetragonal zirconia polycrystalline ceramics, under some typical loading conditions, were studied by Moire interferometry. The full-fi eld fringe patterns, including u-fields and v-fields, were acquired. A ccording to these patterns, the transformation zone shape and transfor mation plasticity distributions of the specimens were obtained. The ex perimental results show that the stress-induced transformation at room temperature is concentrated in some narrow bands and the transformati on plasticity is not uniform within the transformation zone. Experimen ts also reveal that the transformation zone with a characteristic elon gated shape ahead of the notch, in a single-edge notch bending specime n, is obviously different from that resulting from some constitutive r elation of transformation. This work provides a significant experiment al foundation for establishing the theoretical models of transformatio n toughening.