Microstructure Invesitigation of Zr-0.8Sn-1Nb-0.3Fe Zr Alloys

Abstract:

The microstructure of two types of Zr-0.8Sn-1Nb-0.3Fe alloys prepared with different processes developed by Nuclear Power Institute of China was analyzed using optical microscope and transmission electron microscopy. The experiment results showed that with increasing of cold rolling and annealing times, the crystal grain of Zr alloy became much larger and much more non-uniformly in size. The average size of crystal grain grew from 3.9μm to 6.0μm. Further, the size of precipitates also became larger and the dispersion degree became much more non-uniformly, the average size of precipitates grew from 74.6nm to 89.6nm. Increaseing the cold rolling and annealing times could induce more Nb separating out from the matrix. The average of Nb/Fe ratio of precipitates increased from 1.17 to 1.39. Most of precipitates in Zr matrix were (Zr,Nb)2Fe compounds with FCC structure. Besides, a few of Zr(Nb,Fe)2 precipitates with HCP structure were also observed in the alloy increased of cold rolling and annealing times, but their size was much smaller. It was very important effect of the cold rolling and annealing processes on the microstructure of Zr alloys.

Key words:Zr alloys; Microstructure; Precipitates; Fule cladding