The effect of cooling rate and grain size on hydride formation in Zircaloy-4

TL;DR

This study investigates how cooling rate and grain size influence the formation, distribution, and morphology of zirconium hydrides in Zircaloy-4, revealing that these factors significantly affect hydride nucleation and growth.

Contribution

It provides new insights into the effects of cooling rate and grain size on hydride formation in Zircaloy-4, highlighting their roles in controlling hydride morphology and distribution.

Findings

Cooling rate and grain size control hydride phase and distribution.

Blocky alpha Zircaloy-4 has fewer grain boundaries affecting hydride nucleation.

Grain size influences the nucleation and growth behavior of hydrides.

Abstract

We explore the distribution, morphology and structure of zirconium hydrides formed using different cooling rates through the solid state Zr+[H] --> Zr + hydride transus, in fine and blocky alpha Zircaloy-4. We observe that cooling rate and grain size control the phase and distribution of hydrides. The blocky alpha (coarse grain, > 200 micrometer) Zircaloy-4, has a smaller grain boundary area to grain volume ratio and this significantly affects nucleation and growth of hydrides as compared to fine grain size (~11 micrometer) material.