Amorphization kinetics of Zr(Cr, Fe)2 under ion irradiation

Thin foils of Zircaloy-4 were irradiated with 350 keV 40Ar ions in the dual ion beam/HVEM facility at Argonne National Library at 300-650 K. The irradiation-induced amorphization of the intermetallic precipitates Zr(Cr, Fe)2 and Zr2(Ni, Fe) was studied in-situ. For Zr(Cr, Fe)2 precipitates the dose-to-amorphization was found to increase exponentially with temperature, with a critical temperature of about 650 K. The amorphization morphology was shown to be homogeneous, with no preferential site for nucleation, in contrast to neutron-irradiation amorphization, which started at the precipitate-matrix interface. For Zr2(Ni, Fe) precipitates it was found that amorphization occurred at 550 K and 600 K, whereas in neutron irradiation no amorphization has been observed at those temperatures. The results are discussed in the context of the previous experimental results of neutron and electron irradiation, and likely amorphization mechanisms are proposed. (author). 18 refs., 3 figs