Joining and testing of alumina fibre reinforced YAG-ZrO2 matrix composites

Alumina (Nexte (TM) 610) fibre reinforced YAG-ZrO2 matrix composites were successfully joined by using different brazing alloys, metallic interlayers and a glass-ceramic. All joints were mechanically stable and free of cracks. Three commercial brazing alloys and a new alloy based on Ti/Cu/Al interlayers were selected to join these composites for applications in a non-oxidizing environment. A glass-ceramic based on SiO2-Al2O3-CaO-MgO was developed in case the joined component needs to be oxidation resistant. To evaluate the thermal stability, all joined composites were aged up to 100 h in air at 550 degrees C for brazing joints or 850 degrees C and 930 degrees C for glass-ceramic joints. The mechanical strength was measured using single lap and four point bending tests before and after ageing. Four point bending tests on glass-ceramic joined samples showed an average joint strength of about 70 MPa which is 35% of as-received composites.