Ferroelastic and Plastic Deformation of t′‐Zirconia Single Crystals

Abstract

Polydomain tetragonal (t) zirconia was deformed in compression along a ͗100͘ orientation at various temperatures between 500°and 1400°C. The stress-strain curves showed a plateau corresponding to ferroelastic deformation, followed by plastic deformation at a higher yield stress level. In both ranges, the strain-rate sensitivity of the stress was measured by stressrelaxation tests. The microstructure of the tetragonal domains after ferroelastic deformation and the dislocation substructure were studied by transmission electron microscopy in a highvoltage electron microscope. As expected, ferroelastic deformation suppressed the tetragonal variant with its c-axis parallel to the loading direction. The dislocation structure consisted of intersecting dislocations on different slip systems with strongly bowed-out segments. The microprocesses of deformation are discussed here by comparing the deformation data with those of cubic zirconia deformed in the same orientation and based on the observed microstructure. The particular microstructure of t zirconia seems to prevent recovery, so that the high flow stress of ϳ700 MPa is preserved up to 1400°C.

The influence of oxides on the performance of advanced gas turbines

“…[77][78][79] Upon crack extension, dissipation occurs through the formation (or switching) of nano-scale domains, resulting in toughening that scales with the tetragonality, c/a, and the coercive stress. 23,24,[77][78][79] The concept that the tetragonality governs the toughness of tetragonal oxides has led to the development of new compositions with appreciably higher toughness than 7-YSZ. 24,25,80 The most prominent example resides within the ZrO 2 -YO 1.5 -TiO 2 ternary phase field (Fig.…”

Effect of phase transformations on the fracture toughness of t′ yttria stabilized zirconia

“…Ferroelasticity [20][21][22] is the operating toughening mechanism in these materials. The motivation for studying the inherent fracture toughness of the TBC material stems from the coating failure mechanisms.…”

First-principles calculations of the high-temperature phase transformation in yttrium tantalate

“…In addition, an intriguing feature of materials that can undergo a ferroelastic phase transition is that they are capable of exhibiting toughening if the stress is sufficiently high to trigger the transformation from one variant to another 6,7 . This occurs, for instance, in yttria-stabilized zirconia [7][8][9][10] . In this oxide material, the high-temperature cubic phase undergoes a ferroelastic transformation to crystallographically equivalent tetragonal variants, which can be switched by an applied stress, dissipating energy and thereby producing toughening.…”