Fracture toughness improvement of alumina with elongated grains

Mechanical properties and microstructure characteristics of hot-pressed and pressureless sintered Al2O3 ceramics were investigated. The materials were produced using α-alumina powder from calcined commercial aluminium hydroxide and seeded by wet-grinding abrasion α-Al2O3 milling medium. A microstructure of elongated U-Al2O3 grains was obtained by hot-pressing the alumina powder compacts. Elongated α-Al2O3 grain, however, could not be observed in the pressureless-sintered samples. In the pressureless sintered samples, only platelet grains and abnormal equiaxed grains were formed. It is thought that the elongated grains were developed from the fine α-Al2O3 abrasion seeds under suitable sintering conditions. Increased fracture toughness of 6 MPa.m1/2 and flexural strength of 547 MPa were achieved for the samples with the elongated grain structure hot-pressed at 1600 deg C. Copyright (2000) The Australian Ceramic Society