Ferroelastic and plastic deformation of t '-zirconia single crystals

Polydomain tetragonal (t ') zirconia was deformed in compression along a < 100 > orientation at various temperatures between 500 degrees and 1400 degr eesC. The stress-strain curves showed a plateau corresponding to ferroelast ic deformation, followed by plastic deformation at a higher yield stress le vel. In both ranges, the strain-rate sensitivity of the stress was measured by stress-relaxation tests. The microstructure of the tetragonal domains a fter ferroelastic deformation and the dislocation substructure were studied by transmission electron microscopy in a high-voltage electron microscope. As expected, ferroelastic deformation suppressed the tetragonal variant wi th its c-axis parallel to the loading direction. The dislocation structure consisted of intersecting dislocations on different slip systems with stron gly bowed-out segments. The microprocesses of deformation are discussed her e by comparing the deformation data with those of cubic zirconia deformed i n the same orientation and based on the observed microstructure. The partic ular microstructure of t ' zirconia seems to prevent recovery, so that the high flow stress of similar to 700 MPa is preserved up to 1400 degreesC.