The effects of sintering temperature on mechanical and electrical properties of Al2O3/Ti composites

Al2O3-based composites containing 20 vol% Ti were fabricated at various sintering temperatures and the effects of Al2O3 grain size (R-Al2O3) and Ti particle size (R-Ti) on mechanical and electrical properties were studied. Results indicated that toughening effects caused by Ti were enhanced with the growth of Ti particles while the large Al2O3 matrix grains showed a reverse effect on toughening. Composite containing adequate R-Al2O3 and R-Ti (both below 2 pm) exhibited the highest flexural strength and fracture toughness when sintered at 1500 degrees C. For R-Al2O3 below 2 pm, electrical resistivity dropped as R-Ti increased. But for R-Al2O3 over 2 pm, electrical resistivity relied on the size of both matrix grains and metal particles. Percolation threshold volume of Ti varied with size ratio R-Al2O3/R-Ti. It is speculated that when R-Al2O3/R-Ti is close to 1, percolation threshold in Al2O3-Ti system might reach the lowest value. By controlling R-Al2O3/R-Ti similar to 1 and R-Al2O3 < 2 pm, it is possible to fabricate conductive ceramic-metal composites with excellent mechanical properties containing metal phase with relatively low content. For the composites prepared from starting materials with various sizes, this study has important guiding significance.