The Shs Composite Pipe Liner (al <sub> 2 </ Sub> The O <sub> 3 </ Sub> + Of Zro <sub> 2 </ Sub>) Composite Ceramics The Microstructure And Toughness Behavior Analysis

Self-propagating High-temperature Synthesis (SHS) is a new technique by which material synthesis is achieved through the self-heating and self-conducting process making use of the heat from the chemical reaction between reactors. ZrO2(4mol%Y₂O₃) of various contents being introduced into the main combustion system, the composite pipe lined (Al₂O₃+ZrO₂) multi-phase ceramics can be fabricated with the SHS gravitational separation technique. In this paper the systematic research is made into the dynamics, microstructure and formation of the lined multi-phase ceramics and its toughening behavior; the best main combustion system and self-propagating synthesis technique are also investigated to achieve the transformation toughing and multi-phase toughing.When ZrO₂ content is 25wt%, the fracture toughness is up to its maximum, i.e. 15.96 MPa . m¹/2.A conclusion is drawn from SEM observation and EPMA analysis that multi-phase ceramics base consists of lamellar or rod-like eutecticum of ZrO₂ with Al₂O₃, that Al₂O₃ dendrite is distributed between (Al₂O₃+ZrO₂) eutecticum while ZrO₂ is distributed on boundary area in appearance of band and particles in the hypoeutectic multi-phaseceramics, whereas as for the hypereutectic multi-phase ceramics ZrO2 is distributed between (Al2O3+ZrO2) eutecticum in appearance of snowflake or fish-bone. During the cooling and solidifying process of the (Al2O3+ZrO2) multi-phase ceremics melts, as for the hypoeutectic multi-phase ceramics, AI2O3 will be first separated as the leading phase, the remaining liquid phases being solidified in the form of divorced eutectic and then symbiotic eutectic; whereas as for the hypereutectic multi-phase ceramics ZrO2 is separated as the leading phase, the remaining liquid phase is solidified in the form of symbiotic eutectic.In the (Al2O3+ZrO2) multi-phase ceramics, there exist four main toughening behaviors, i.e. base bridging toughening, ZrO2 transformation toughening, microcrack toughening and particle toughening. The hypoeutectic multi-phase ceramics is mainly based on base bridging and ZrO2 transformation toughening behaviors, with subsequent microcrack toughening functioning to achieve great combined toughening effect; however, the hypereutectic multi-phase ceramics is mainly based on microcrack and base bridging toughening behaviors, with subsequent ZrC>2 transformation toughening functioning to achieve great combined toughening effect.