MICROSTRUCTURE INVESTIGATION OF CR AND CR ALLOYS IRRADIATED WITH HEAVY-IONS

The results of microstructure investigation of pure Cr and low- and hi gh-doped Cr alloys (Cr with low additions of La, Ta, Re; Cr doped with low additions of La, Ta, V; Cr alloyed with low additions of Fe, La; and 66Fe33CrAl, 33Fe66CrAl) irradiated by Cr ions in the temperature r ange 550 to 800 degrees C up to dose of 180 dpa are presented. Disloca tion structure evolution in low-doped Cr alloys differs from that in a lpha-Fe alloys: loop faulting disappears in the beginning of irradiati on; perfect loops have mainly Burgers vector (alpha/3)[112] on {111} p lanes and appreciably less have Burgers vector (alpha/2)[111] on {110} planes. High stability for dislocation loops in Cr alloys irradiated to high dose levels was discovered. The temperature and dose dependenc es obtained allowed evaluation of swelling resistance in Cr alloys. It was established that the swelling behavior is similar to that for oth er refractory metals having a bcc lattice. The maximum value of swelli ng is 9% at an irradiation dose level of 180 dpa in the temperature ra nge from 730 to 750 degrees C. Voids in Cr alloys are formed at dose l evels of 1-2 dpa, similar to other refractory metals having a bcc latt ice. The voidage is characterized by a homogeneous distribution of fin e voids. It was established that a preliminary heat treatment, CW or a lloying with low additions do not have significant effects on either t he void nucleation process or swelling response. Void lattice formatio n was observed in Cr alloyed with low additions of La, Ta and V. The h omogeneous distribution of fine voids through the matrix may be the ca use of loss in ductility of the material. Highly-alloyed Cr alloys und ergo intensive solid solution decomposition leading to heterogeneous s welling.