Hydride embrittlement and irradiation effects on the hoop mechanical properties of pressurized water reactor (PWR) and boiling-water reactor (BWR) ZIRCALOY cladding tubes: Part III. Mechanical behavior of hydride in stress-relieved annealed and recrystallized ZIRCALOYs at 20 °C and 300 °C

Abstract

This series of articles on the hydride embrittlement effect in ZIRCALOYs consists of three parts. Part III deals with the mechanical properties of some hydrides in some ZIRCALOYs at two temperatures (20 ЊC and 300 ЊC). The damage and fracture mechanisms were investigated by SEM in-situ testing. Based on the scanning electron microscopy (SEM) in-situ observations and the mechanical modeling, the mechanical behavior of hydrides confined within a matrix was determined. The hydrides can undergo significant plastic deformation under certain conditions. They have higher strength than the surrounding ZIRCALOY matrix. The radiation effect on hydrided ZIRCALOYs and the combined effect were also discussed. Part I is concerned with the general influence of hydrides on the mechanical properties and damage and fracture mechanisms of ZIRCALOYs at two temperatures (20 ЊC and 300 ЊC) and for hydrogen content up to 4500 ppm. In Part II, the morphology and crystallographic structure of hydrides in two ZIRCALOYs are examined at different magnifications and by different techniques (SEM, transmission electron microscopy (TEM), and X-ray diffraction) as a function of their pre-heat treatment and their hydrogen content.

Observations on the Zirconium Hydride Precipitation and Distribution in Zircaloy-4

“…This increase in the microhardness is ascribed to the matrix hardening effect induced by hydrides that are embedded in the Zr-4 matrix. [21] Besides, the considerably inhomogeneous hydride distribution in the 10-atmhydrided sample (Figure 3(b)) resulted in a significant fluctuation of microhardness (as reflected by the large error bar). In contrast, a relatively uniform distribution of the microhardness was achieved in the 20-atmhydrided sample on the RD-TD section because of the formation of homogenously dispersed hydrides (Figure 3(c)).…”

Fracture Strength of Embedded Hydride Precipitates in Zirconium and its Alloys

“…2. However, as recognized also by others in recent years [1,2,50], the latter type of tests involve the production of macroscopic hydride specimens having microstructures different from those of the hydride clusters embedded in a zirconium matrix. In addition, their macroscopic sizes likely make them more susceptible to fracture.…”

Microstructural evolution during gaseous hydrogen charging of Zircaloy-4 processed by high-pressure torsion: A comparative study

“…Hydride precipitation is an intricate process, controlled by several factors such as microstructure of Zr-4, the hydriding conditions, and the hydrogen contents, which have appreciable influences on the final morphology of hydrides [1]. Currently, investigations on the hydride precipitation behavior in Zr-4 have attracted considerable attention.…”