Consolidation of flaw-tolerant layered structures by the insertion of reactive layers

摘要

The processing parameters to obtain a laminate consisting of very thin alumina-aluminium titanate crack deflecting layered structures sandwiched between relatively thick load bearing alumina layers are described. The optimum processing conditions for the insertion of reactive layers to improve joining during sintering have been established. Pre-sintered alumina tapes were used as the load bearing components while the internal structures were shaped by a combination of electrophoretic deposition (EPD) and dipping. The dipped layers acted as reactive layers during sintering. The thickness of the dipped layers has to be controlled in order to avoid the disappearance of the EPD structure during sintering as well as the cracking of the coating during drying or handling. The specimens were mechanically tested in three points bending with the applied load perpendicular to the layers and the fracture surfaces were observed by scanning electron microscopy. The obtained structure presents crack deflection at the microstructural scale during fracture which confers it flaw tolerance.