Phase analysis of hydride blister in zirconium alloy

This paper mainly concerns phase analysis of hydride blister and phase transformation at elevated temperature with Zircaloy-4 cladding. With electron diffraction patterns from the blister sample, single delta phase hydride is selected, especially, to investigate the phase transformation of delta-hydride with TEM. Under the rapid cooling condition, single delta-hydride transforms to heterogeneous ultrafine lamellar-like structure with the delta and gamma-hydride phases. However, the phase transformation from delta-hydride to gamma-hydride has not been reported around delta-phase domain in the Zr-H phase diagram, and thus, we suggest that the gamma-hydride is able to be generated in the d phase domain as well as in the alpha+delta phase domain. It is also proven that the gamma phase tends to transform to the stable d phase with sufficient holding time at the elevated temperature during in-situ TEM experiment. (C) 2017 Elsevier B.V. All rights reserved.