Preparation and characterization of a dispersion toughened ceramic for thermomechanical uses (ZTA). Part II: Thermomechanical characterization. Effect of microstructure and temperature on toughening mechanisms

Abstract According to the composition and processing conditions, different microstructures of zirconia toughened alumina (ZTA) materials can be obtained (as shown in Part I of this paper). The mechanical behavior of the different ZTA materials was determined at room and high temperatures: fracture strength and toughness ( σ f , K Ic ), slow crack growth resistance ( K 1 − v ). Zirconia toughened alumina composites present improved fracture properties compared to pure alumina. Thermal fatigue resistance is also improved compared to pure Al 2 O 3 or ZrO 2 (Y-TZP) materials. The decrease of hardness by increasing addition of ZrO 2 particles is counterbalanced in part by toughening effects and the wear resistance can be improved for some compositions. Two predominant and interacting toughening mechanisms are operative at low temperature: stress-induced phase transformation toughening (TT) and microcracking toughening (MT). Both toughening mechanisms are temperature dependent, but at different rates. The toughening and strengthening effects are discussed on the basis of transformation of metastable zirconia particles depending on ZrO 2 and stabilizing agent (Y 2 O 3 ) contents, on the particle size and on the temperature.