Effect of grain morphology on fracture behavior of alumina ceramics analyzed by in situ fluorescence microprobe spectroscopy
Okuda Hajime; Pezzotti Giuseppe; Muraki Naoki; Nishida Toshihiko
Abstract:An in situ fluorescence microprobe spectroscopy approach is applied to clarify the effect of grain morphology on fracture toughness of Al2O3 ceramics. Fluorescence spectroscopy enables to experimentally determine a map of the crack-wake bridging stress distribution with micrometer precision and, thus, to predict the R-curve and the crack opening displacement (COD) behavior of the material. Platelet-shape grain morphology was found to significantly enhance the bridging stresses in the neighborhood behind the crack tip, as compared to equiaxed Al2O3. A maximum bridging stress of about 350 MPa was found to arise from elastic bridging sites, according to microscopy observation. The experimentally determined bridging stress distribution produces a rising R-curve behavior and a COD profile consistent with those experimentally measured. Key Words:alumina ceramics, R-curve behavior, bridging stress, fluorescence microscope spectroscopy