Critical crack-healing condition for SiC whisker reinforced alumina under stress

Abstract: Alumina reinforced by SiC whisker, called here “alumina(w)” was developed with the objective of improving fracture toughness and crack-healing ability. The composites were crack-healed at 1200°C for 8h in air under elevated static and cyclic stresses. The bending strength at 1200°C of the crack-healed composites were investigated. The threshold static stress during crack-healing of alumina(w) has been determined to be 250MPa, and the threshold cyclic stress was found to be 300MPa. Considering that the crack growth is time-dependent, the threshold stress of every condition during crack-healing of alumina(w) was found to be 250MPa. The results showed that the threshold stress intensity factor during crack-healing was 3.8MPam1/2. The same experiment conditions were applied to specimens cracked and annealed at 1300°C for 1h in Ar, to remove the tensile residual stress at a tip of the crack. Thus, the threshold stress intensity factor during crack-healing was found to be 3.2MPam1/2 for the specimens crack-healed with annealing. The threshold stress intensity factor during crack-healing of alumina(w) was chosen to be 3.2MPam1/2 to facilitate comparison with the values of the threshold stress intensity factor during crack-healing. The residual stress was slightly larger than the intrinsic value. [Copyright &y& Elsevier]