Abstract
ZrO2 (3Y-TZP) matrix composites with 30 vol % Zr metallic particles were obtained by spark plasma sintering (SPS) using a colloidal processing method. The microstructure and mechanical properties of this novel ceramic–metal composite have been studied. The fracture toughness of composites is slightly higher than the values corresponding to monolithic zirconia. Scanning electron microscope (SEM) observations of the crack path show that the major contributions to toughening are the resulting crack blunting and branching that occurs at crack tips in the metallic particles before the onset of crack propagation. Plastic deformation of the metallic particles is strongly influenced by the constraint induced by the different phase arrangements. This system can be considered as a particulate composite with a periodic residual stress field, in which the metal phase is under strong compression due to the residual thermal stresses as a consequence of the coefficient of thermal expansion mismatch. Therefore, the plastic deformation of the metallic particles in this composite is likely to be reduced to a large extent.
Highlights
Zirconia (3Y-TZP) is an extensively used material for many structural and biomedical applications due to its excellent biocompatibility, chemical inertness and good tribological and mechanical performance [1,2,3,4]
Scanning electron microscope (SEM) observations of the crack path show that the major contributions to toughening are the resulting crack blunting and branching that occurs at crack tips in the metallic particles before the onset of crack propagation
This system can be considered as a particulate composite with a periodic residual stress field, in which the metal phase is under strong compression due to the residual thermal stresses as a consequence of the coefficient of thermal expansion mismatch
Summary
Zirconia (3Y-TZP) is an extensively used material for many structural and biomedical applications due to its excellent biocompatibility, chemical inertness and good tribological and mechanical performance [1,2,3,4]. When second phase metallic particles are incorporated into a brittle matrix, there are several toughening mechanisms that may operate, but the maximum benefit is derived from the plastic deformation of the metallic particles, i.e., crack blunting and bridging an advancing crack [5,6,7]. The bridging ligaments exert closure stresses, which reduce the stress intensity at the crack tip and offer resistance to further crack opening or propagation. The magnitude of these crack closure stresses on the crack wake is based upon a stress–strain relation of the metal ligaments, which is influenced by the properties of the reinforcing metal itself and Ceramics 2020, 3, 53–64; doi:10.3390/ceramics3010007 www.mdpi.com/journal/ceramics
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