Intergranular δ-hydride nucleation and orientation in zirconium alloys

• Published in: Acta materialia Vol. 59; no. 18; pp. 7010 - 7021
• Main Authors: Qin, W., Kiran Kumar, N.A.P., Szpunar, J.A., Kozinski, J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2011; Elsevier
• Subjects: Applied sciences; Exact sciences and technology; Grain boundaries; Grain orientation; Hydrides; Metals. Metallurgy; Nucleation; Orientation; Precipitation; Zirconium; Zirconium base alloys; Grain boundaries; Hydrides; Nucleation; Orientation; Germination; Microstructure; Grain boundary
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2011.07.054

A theoretical understanding of the intergranular δ-hydrides is still lacking, although hydride-related degradation of the mechanical properties of zirconium alloys has been studied for many years. In this paper a thermodynamic model is developed to analyze the nucleation and orientation of intergranular δ-hydrides. The results show that the grain boundary structure and zirconium grain orientation simultaneously govern hydride precipitation. An electron backscatter diffraction study of hydrided Zircaloy-4 provides direct evidence supporting theoretical predictions. A criterion is proposed to reveal the inherent relation between hydride precipitation at the grain boundaries and in the zirconium grains. Stress-induced susceptibility to hydride precipitation at the radial grain boundaries of zirconium alloy tubes is theoretically analyzed. This work provides a general framework based on which the correlation between the grain boundary structure, the grain orientation, the stress and their effects on the nucleation and orientation of the intergranular δ-hydrides can be clarified.