Microstructure and mechanical property of thin-wall Al2O3-YAG composite ceramics built by laser engineered net shaping

Thin-wall ceramics were built by Laser engineered net shaping (LENS) with coaxial feeding Al2O3-Y2O3 powder. The microstructure, phase and element of the sample were characterized by scanning electron microscopy, X-ray diffraction and electron probe microanalysis, respectively. The microhardness and fracture toughness of the sample were examined via indentation tests. The results show that the Al2O3-YAG composite ceramics can be built directly by LENS with coaxial feeding Al2O3-Y2O3 powder. The ceramics are mainly composed of Al2O3 and YAG phases with a little metastable phase-YAP or YAM. The microstructure of the sample is composed of rich YAG primary phase and Al2O3/YAG eutectic organization. As Al2O3 is volatile, the melting times of different heights in the sample affect the relative volatilization of Al, leading to the different ratios of the two phase at different points, and the size and proportion of rich YAG primary phase increase from top to bottom. Besides, the high temperature of the sample in the process makes the metastable phase transforming to YAG, exacerbating the increase of rich YAG phase. The sample built by LENS has a good performance, i.e., the microhardness of 16 GPa and the fracture toughness of 2.89 MPa·m1/2. ©, 2015, Chinese Ceramic Society. All right reserved.