Microstructurally Developed Toughening Mechanisms in Ceramics. Stress Induced Martensitic Reaction. II. Experiments in the ZrO2-Y2O3 System.
Abstract
Retention of the tetragonal phase was found to depend on both density and grain size. The dependence on density is consistent with the need for self-constraint and the concepts developed regarding the thermodynamics of the martensitic reaction in an elastically constrained system. The dependence on grain size and the effect of Y2O3 on the critical grain size is consistent with the theory relating the latent internal pressure (required to maintain equilibrium between the two structures) and the grain size to the thermodynamics of microcracking in a highly localized stress field. The contribution of the stress-induced transformation to the fracture toughness is significant and it is directly related to the volume fraction of the retained tetragonal phase. Theory developed to explain this contribution is in good agreement with experimental data validating the concept that the transformation's contribution lies with the work done by the crack's stress field to unconstrain the martensitic reaction. Fractography indirectly supports this concept and directly invalidates the concept of microcracking in advance of the primary crack as suggested by others. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1978
- Accession Number
- ADA057240
Entities
People
- F. F. Lange