Laser Zone-Remelted Alumina-Based Eutectic in situ Composite

摘要

Due to excellent oxidation and corrosion resistance at elevated temperature, oxide ceramic could be the preference served at high temperature oxidizing atmosphere over a long period of time. In recent years, alumina-based eutectic in situ composite prepared by various solidification techniques, which has superior properties even close to the melting point about 2100K, has been paid much attention. In this paper, Al_2O_3/YAG/ZrO_2 ternary eutectic and hypoeutectic ceramics are prepared from melt by laser zone-remelting technique, the rapid solidification characteristic and the mechanical property of the composites are investigated. The results show that: (1) Compared to sintered composite with the same composition, laser zone-remelted Al_2O_3/YAG/ZrO_2 eutectic in situ composite has different microstructure showing fine interpenetrated network with Al_2O_3, YAG and ZrO_2 phases continuously intergrown, while none of pores, grain boundaries and amorphous phases is found. (2) The scanning rate and the power density of the laser beam has strong effect on the microstructure morphology. When the power density is determined, the eutectic spacing is reduced with the scanning rate increased. The characteristic eutectic spacings and phase sizes of YAG and Al_2O_3 are about 2～3μm, and the characteristic dimension of ZrO_2 is less than 1μm. (3) The hardness and the room-temperature fracture toughness of Al_2O_3/YAG/ZrO_2 eutectic are respectively H_v=16.7±2.0 Gpa and K_(IC)=8.0±2.0 Mpam~(1/2), and those of hypoeutectic are respectively H_v=l5.8±2.0 Gpa and K_(IC)=3.9±1.0 Mpa m~(1/2).