Grain morphology and crystal structure of pre-transition oxides formed on Zircaloy-4

Grain morphology and crystal structure of pre-transition oxides formed on a Zircaloy-4 alloy were investigated. The results show that monoclinic columnar grains align tightly in inner oxides, whereas porous monoclinic equiaxed grains exist in outer oxides. Small-sized tetragonal equiaxed grains are embedded in monoclinic columnar grains, with tetragonal phase content declining from the inner to the outer oxides. The crystallographic orientation relationship of (111)(m)//(10 (1) over bar0)(alpha-zr) was identified, which explains well the formation of monoclinic texture on the zirconium substrate. This work advances the understanding of corrosion properties before transition of oxidation of zirconium alloys. (C) 2013 Elsevier Ltd. All rights reserved.