Effect of the microstructure on the mechanical properties of a directionally solidified Y3Al5O12/Al2O3 eutectic fiber

The strength and fracture behaviors of a directionally solidified Y3Al5O12/ Al2O3 eutectic fiber were investigated. The fiber was grown continuously by an edge-defined film-fed growth (EFG) technique. The microstructure was ch aracterized using X-ray diffraction (XRD), scanning electron microscopy (SE M), and energy dispersive spectroscopy (EDS). The room temperature tensile strength and Weibull's modulus of the eutectic fiber before and after heat treatment at 1460 degreesC were measured. The fracture toughness and crack propagation behaviors were investigated using an indentation technique. Sig nificant coarsening of the lamellar microstructure was observed after heat treatment at 1460 degreesC in air. The degradation of the room temperature tensile strength in the Y3Al5O12/Al2O3 eutectic fiber after heat treatment was attributed to the development of surface grooves at the surface of the fiber. Also, the Y3Al5O12/Al2O3 eutectic fiber showed a radial (Palmqvist) crack type and exhibited an anisotropic crack propagation behavior during t he indentation tests. (C) 2001 Kluwer Academic Publishers.