Creep of Zirconia/Nickel Composites

High-temperature plastic behavior of reaction-bonded CuO and TiO2 co-doped alumina–zirconia

“…Results from X-ray diffraction analysis show that the samples consist mainly of monoclinic zirconia and ␣-alumina; some traces of tetragonal zirconia can also be distinguished [7]. These data are consistent with a complete dissolution of the dopants into the alumina lattice, being the resulting material two-phase.…”

“…These calibration curves were used to convert the relaxation data from the testing samples into instantaneous length versus time curves. From these it is straightforward to get strain rate versus stress curves by numerical differentiation; the details can be found in reference [7].…”

Anomalous high activation energy for creep in nanostructured 3YTZP/Ni cermets

“…5 The existence of a threshold stress has been confirmed byε versus (σ − σ 0 ) 2 plots of our experimental data accepting that the ceramic phase controls the creep properties. 4,5 Therefore, the creep rate of 3YTZP/n-Ni composites is correctly described by the following constitutive equation instead of equation (1): where σ 0 is similar to the threshold stress reported in high-purity YTZP polycrystals of the same average grain size 12 and also in 3YTZP/-Ni cermets. 5 Yttrium segregation towards grain boundaries, making GBS difficult, has been pointed out at the origin of the threshold stress.…”

“…Available studies conclude that creep is exclusively controlled by the zirconia matrix. 4,5 Recently, Esteban-Betegon et al 6 have prepared 3YTZP/n-Ni nanocrystalline composites by precipitation, reduction and sinterization of nickel salts on zirconia powder. These composites that have small amounts of nickel exhibit strong metal-ceramic bonds 7,8 and a remarkable hardening effect.…”

Correlación entre la microestructura y el comportamiento plástico a alta temperatura de compuestos TZP-Ni (40% vol.)

“…Estos parámetros, junto con los valores de e medidos, permiten asegurar que se trata de un material de alta pureza -de acuerdo con el contenido de impurezas tan bajo de los polvos de partida-, del que ya se ha estudiado su comportamiento mecánico en amplias revisiones (9,10 valores de n = 2.6 ± 0.1 y de Q = 670 ± 40 kJ/mol similares a los anteriores (figura 5). Hay que destacar que el esqueleto se fractura para e ≈ 15% en contraste con el comportamiento del cermet, que alcanzó una deformación del 30% sin signos macroscópicos de daño (8). También hay que señalar que para temperaturas por debajo de 1000 ºC no existen resultados previos sobre la fluencia de compuestos a base de circona.…”