Quantifying the stress state in the vicinity of a δ-hydride in α-zirconium

In zirconium alloys, precipitation of a hydride generally introduces internal stresses in the surrounding matrix. This study aims at understanding the role of internal stresses on the formation, growth and arrangement of δ-hydrides in α-zirconium. To this end, a Fast Fourier Transform based discrete dislocation dynamics technique is used to quantify both internal stresses induced during the formation of a hydride and the relief of the internal stresses by dislocation nucleation from the hydride-matrix interface. This work reveals that stress relaxation is localized in very small regions around the δ-hydride (∼ 300 nm). Further, it is proposed that the dislocations nucleated from the hydride-matrix interface could act as loci for the nucleation of new hydrides, thereby rationalizing experimentally observed hydride stacks. Finally, quantifying the stress relaxation resulting from dislocation nucleation reveals that diagonal components of the internal stress inside the hydride remain very high, i.e., >3.0 GPa. This suggests that additional dissipative processes, intrinsic to the hydride, are necessary to diminish the aforementioned internal stress.