AlB_2-C添加SiCの微細構造と高温での機械的特性

概要

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The microstructure of hot-pressed SiC added with AlB_2-C was analyzed by the microstructural observation and elemental analysis. According with the results of such analysis, the mechanical properties at high temperature were discussed. AlB_2-C mainly reacted to form Al_2O_3 and B_4C. A minor fraction on Al-Si-(B)-C-O phase, in which O was thought to be supplied from impurity SiO_2 in the raw SiC powder, was observed by transmission electron microscope. Al-C-O phase was detected as an intergranular phase. The flexural strength decreased from 660 MPa at room temperature to 530 MPa at 1450℃ and the fracture toughness with SEPB method increased from 4.5 MPa・m^<1/2> at room temperature to 10.9 MPa・m^<1/2> at 1500℃. The intergranular phase of Al-C-O is thought to cause strength degradation because of the phase softening at high temperature. From fracture surface observation after fracture toughness test, a fibrous texture on the fracture surface was observed. Auger electron analysis revealed that the fibers were composed of Al-C-N-O. The Al-C-O intergranular phase may become a highly viscous Al-C-N-O phase during toughness test at 1500℃ in N_2, enhancing the crack-face bridging effect.
社団法人日本セラミックス協会の論文
1998-12-01