Evaluation of pre-transition oxide on Zr–0.4 Nb alloy by using the HVEM

The crystalline structure and morphology of zirconium oxide formed in a water at 360 °C and 18.9 MPa was investigated by using a high voltage electron microscopy (HVEM). The oxide thickness formed on the Zr–0.4 Nb alloy substrate was about 2.2 μm. In the thin oxide layer, the monoclinic and tetragonal phases were mixed with each other and a complex morphology of equiaxed and columnar grains were formed during the oxidation process. From the HVEM observation and the imaging process by using the DigitalMicrograph™ program, it was found that the correlation of a crystalline orientation between the equiaxed grain and the columnar grain was not formed in the oxide layer, and a defect such as a dislocation which had formed in the tetragonal phase could be extracted by the masking tool of the inverse fast Fourier transformation (IFFT).