Tem Study Of Zirconium Hydrides Precipitated In Zr-4 Alloy

The type, morphology and orientation relationship of the hydride precipitates in a hydrogen absorbed Zr-4 alloy have been studied by transmission electron microscopy (TEM). The results show that delta-ZrH1.6 and epsilon-ZrH1.8 hydrides are found to precipitate successively with the increase of hydrogen absorption. The 8-Zr111.6 hydrides are mainly in the form of lath and precipitate in the orientation relationship of (0001)(alpha)//(001)(delta) and [2 (1) over bar (1) over bar0](alpha)//[110](delta) with the alpha-Zr matrix, while the epsilon-ZrH1.8 hydrides are in acicular morphology and precipitate in the orientation relationship of ((1) over bar 1 (1) over bar)(delta)//((1) over bar 1 (1) over bar)(epsilon) and [(1) over bar 12](delta)//[011](epsilon) with the delta-ZrH1.6 hydrides. The close-packed planes of these two hydrides are identified to be parallel. High-resolution TEM observation shows that there exists a great deal of distortion inside the crystal lattice of the delta-ZrH1.6 and epsilon-ZrH1.8 hydrides, indicating a large stress concentration produced during their precipitation.