Mechanical Properties of 2Y-TZP Fabricated from Detonation Synthesized Powder

Yttria stabilized zirconia (Y-TZP) is frequently used in dental and engineering applications due to its high strength and fracture resistance. In this study, 2Y-TZP samples were manufactured from commercially available powder produced by detonation synthesis. Tests of the mechanical properties exhibited an unusual combination of both very high strength and toughness. The materials show a very weak correlation between toughness and grain size. The transformability, measurable by XRD, cannot explain the high toughness. Fractographic analysis revealed a broad transformation affected zone with secondary cracks and shear bands on the tensile side of bending bars which can be made responsible for the high toughness and non-linear stress–strain curves

Mechanical Properties and Electrical Discharge Machinability of Alumina-10 vol% Zirconia-28 vol% Titanium Nitride Composites

Electrical discharge machinable ceramics provide an alternative machining route independent on the material hardness which enables manufacturing of customized ceramic components. In this study a composite material based on an alumina/zirconia matrix and an electrically conductive titanium nitride dispersion was manufactured by hot pressing and characterized with respect to microstructure, mechanical properties and ED-machinability by die sinking. The composites show a combination of high strength of 700 MPa, hardness of 17–18 GPa and moderate fracture resistance of 4.5–5 MPa√m. With 40 kS/m the electrical conductivity is sufficiently high to ensure ED-machinability

Electrical Discharge Machinable Ytterbia Samaria Co-Stabilized Zirconia Tungsten Carbide Composites

Composite ceramics of stabilizer oxide coated ytterbia-samaria costabilized zirconia (1.5Yb1.5Sm-TZP) and 24–32 vol% of tungsten carbide as an electrically conductive dispersion were manufactured by hot pressing at 1300–1400 °C for 2 h at 60 MPa pressure. The materials were characterized with respect to microstructure, phase composition, mechanical properties and electrical discharge machinability by die sinking. Materials with a nanocomposite microstructure and a strength of up to 1700 MPa were obtained. An attractive toughness of 6–6.5 MPa√m is achieved as 40–50% of the zirconia transformed upon fracture. The materials show fair material removal rates of 1 mm³/min in die sinking. Smooth surfaces indicate a material removal mechanism dominated by melting

Mechanical properties and low temperature degradation of 1.5Y-1.5Nd-TZP-alumina composites produced by intensive co-milling

In this study toughness of alumina toughened zirconia (ATZ) was improved by co-stabilization by shifting from co-precipitated yttria stabilized zirconia powder to yttria neodymia co-stabilized starting powders in which the stabilizers were introduced by intensive milling. Alumina contents were varied between 0.5 and 20 ​vol.-%. Test samples were consolidated by hot pressing.Microstructure, phase composition, mechanical properties and LTD were studied. The results show that alumina addition leads to an increase in hardness and to a moderate increase in strength. Decreasing toughness with increasing alumina content is coupled with reduction in transformability. Alumina shows no grain growth inhibiting effect, the grain size is dominated by sintering temperature. An increase of sintering temperature causes a decrease of tetragonality of the zirconia matrix despite a rise of cubic phase content. Samples sintered at 1300 ​°C and 1350 ​°C are extremely ageing resistant while samples sintered at 1400 ​°C irrespective of alumina content exhibit poor LTD performance

Enhanced Mechanical Properties in ED-Machinable Zirconia-Tungsten Carbide Composites with Yttria-Neodymia Co-Stabilized Zirconia Matrix

The electrical discharge machining-process (EDM) is a smart solution to optimize the manufacturing chain of customized and complex shaped ceramic components. To comply with the high requirements for the machine and mold design, it is necessary to improve the mechanical properties of ED-machinable ceramics. In this study, ceramic composites with a tetragonal zirconia matrix and tungsten carbide as electrically conductive dispersion were investigated. To improve the toughness of this high strength material, co-stabilized zirconia coated with yttria and neodymia as dopants were used in the compositions with 1.5/1.5 and 1.75/1.25 mol %. These recipes were compared to commercial 3Y-TZP as a reference matrix material combined with the same WC raw powder. The electrically conductive phase content was varied from 20 to 28 vol %. For all compositions, the ceramic blanks were hot pressed at identical dwell and pressure, but with various sintering temperatures (1300 °C to 1450 °C) and then tested with respect to the mechanical and electrical properties. By variation of the stabilizer system, a significantly higher toughness of up to 11.3 MPa√m compared to 5.3 MPa√m for 3Y-TZP-20WC is achieved while the bending strength stays at a comparable high level of >1500 MPa

Yttria Ceria Co-Stabilized Zirconia Reinforced with Alumina and Strontium Hexaaluminate

Zirconia materials are frequently used in dental applications due to their excellent strength and their tooth-like aspect. Standard yttria stabilized zirconia (Y-TZP) ceramics suffer, however, from moderate toughness and vulnerability to low-temperature degradation. In this study, 1Y6Ce-TZP materials reinforced with different amounts of alumina and/or strontium hexaaluminate were manufactured by slip casting and pressureless sintering at different temperatures to assess their mechanical properties, microstructure, phase composition, and low-temperature degradation stability. Results show that these materials exhibit a high fracture resistance of 10⁻12 MPa√m, a bending strength between 700⁻950 MPa, and a Vickers hardness of 1100⁻1200 HV10. Strontium hexaaluminate (SA6) precipitates were formed in situ by reaction of alumina and strontium zirconate. Although crack deflection at SA6 platelets was clearly visible, a net toughening was not observed. Accelerated ageing tests at 134 °C/3 bar water vapor pressure showed best results for mixed alumina/SA6 reinforcements and a sintering temperature of 1500 °C. Mehl-Avrami-Johnson plots used to describe the ageing kinetics showed clear indications of different ageing mechanisms due to the introduction of the SA6 phase