Microstructural characteristics of TZP/Ni cermets plastically deformed at high temperature

The microstructure of 3 mol% Y2O3-stabilized tetragonal ZrO2/Ni (TZP/Ni) composites has been investigated for nickel concentrations of 20, 30 and 40 vol.% before and after creep tests conducted in argon atmosphere at 1250 °C under stresses between 9 and 14 MPa. The microstructures have been characterized using scanning, conventional and high-resolution transmission and analytical electron microscopy. Two types of microstructure were found depending on the presence/absence of percolation in the metal phase. The deformation process strongly affects the percolation threshold due to the elongation of metallic grains and subsequently formation of aggregates. TEM and HRTEM studies in as-received and deformed cermets show the lack of dislocation activity and the absence of secondary phases in both zirconia/zirconia and zirconia/nickel interfaces and triple junctions.