Synthesis of Al<sub>2</sub>O<sub>3</sub>/AlB<sub>12</sub>/Al Composite Ceramic Powders by a New Laser-Induction Complex Heating Method and a Study of their Mechanical Properties

Abstract

Based on the combined toughening principle, pure Al2O3/AlB12/Al composite ceramic powders have been synthesized using a new laser-induction complex heating method. This method starts from Al and B2O3 powder mixtures, after which Al2O3/AlB12/AlN composite ceramics were fabricated by hot-press sintering at 1600°C for 2h under the protection of a N2 atmosphere. XRD and SEM techniques were used to characterize the phases and morphologies of the powders and the ceramics. The bending strength and the fracture toughness of the ceramics were measured by the three-point bending method and the indentation fracture method, respectively. The results show that the pure Al2O3/AlB12/Al composite ceramic powders can be successfully synthesized by this new laser-induction complex heating method because the adiabatic temperature of Al-B2O3 system is more than 1800K. Al2O3 and AlB12 phases were formed by the liquid-liquid reaction mechanism and the liquid-solid reaction mechanism, respectively. The bending strength and the fracture toughness of the Al2O3/AlB12/AlN composite ceramics were 551.44MPa and 6.04MPa.m1/2, respectively. These values are 57.55% and 51% greater than those of the pure Al2O3 ceramic (350MPa and 4MPa.m1/2) due to the reinforcing and toughening in-situ formation of small AlN particles.