Microstructure investigation of Cr and Cr alloys irradiated with heavy ions

The results of microstructure investigation of pure Cr and low- and high-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 range 550 to 800 C up to dose of 180 dpa are presented. Dislocation structure evolution in low-doped Cr alloys differs from that in α-Fe alloys: loop faulting disappears in the beginning of irradiation; perfect loops have mainly Burgers vector (a/3) left angle 112 right angle on {111} planes and appreciably less have Burgers vector (a/2) left angle 111 right angle on {110} planes. High stability for dislocation loops in Cr alloys irradiated to high dose levels was discovered. The temperature and dose dependences obtained allowed evaluation of swelling resistance in Cr alloys. It was established that the swelling behavior is similar to that for other refractory metals having a bcc lattice. The maximum value of swelling is 9% at an irradiation dose level of 180 dpa in the temperature range from 730 to 750 C. Voids in Cr alloys are formed at dose levels of 1-2 dpa, similar to other refractory metals having a bcc lattice. The voidage is characterized by a homogeneous distribution of fine voids. It was established that a preliminary heat treatment, CW or alloying with low additions do not have significant effects on either the void nucleation process or swelling response. Void lattice formation was observed in Cr alloyed with low additions of La, Ta and V. The homogeneous distribution of fine voids through the matrix may be the cause of loss in ductility of the material. Highly-alloyed Cr alloys undergo intensive solid solution decomposition leading to heterogeneous swelling. (orig.)