Evaluation of fracture toughness of (0001) twist boundary using alumina bicrystal

Alumina bicrystals with (0001) twist boundary were fabricated by joining two alumina single crystals at 1900 degrees C in Ar flow in a tungsten furnace. Single edge V-notched plate tension method was applied to evaluate the fracture toughness of the twist boundaries of the bicrystals. The fracture toughness of glass and single crystal alumina was also measured to make sure the validity of this method. The measured fracture toughness of (0001) twist boundaries were 3.6 MPa root m at 0 degrees twist angle, 2.8 MPa root m at 10 degrees, 2.1 MPa root m at 28 degrees, 1.8 MPa root m at 38 degrees and 2.7 MPa root m at 60 degrees, respectively. The dependence of twist angle of fracture toughness of grain boundary of alumina was discussed with changes in surface energy, boundary energy and plastic dissipative energy.