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).