Characterization of zirconium hydrides in Zircaloy-4 cladding with respect to cooling rate

In order to characterize the habit planes and crystallographic relation between the alpha-matrix and various kinds of Zr hydrides, three different Zr hydrides including delta-hydride, gamma-hydride, and surface hydride are produced by controlling the cooling rate from 0.5 to 300 degrees C/min. Analysis of SAED patterns and TEM images of the Zr hydrides demonstrates representative habit planes and crystallographic relation according to the hydride morphologies. The macroscopic delta-hydride has two kinds of habit planes such as {10 (1) over bar7}(alpha) and {0002}(alpha), while microscopic delta-hydride has the habit plane of {0002}(alpha) at the cooling rate of 0.5-10 degrees C/min. The microscopic gamma-hydride has the major habit plane of {10 (1) over bar7}(alpha) at the cooling rate of 300 degrees C/min in which the crystallographic relation between the gamma-hydride and the alpha-Zr matrix as (11 (1) over bar)(gamma)parallel to(01 (1) over bar1)(alpha); (111)(gamma)parallel to(0001)(alpha); [1 (1) over bar0](gamma)parallel to[11 (2) over bar0](alpha). (C) 2015 Elsevier B.V. All rights reserved.