57Co impurity-interstitial configurations in NbMo alloys observed by Mössbauer spectroscopy

Lattice defects in NbMo57Co alloys produced by neutron irradiation at 4.6 K and by cold working were investigated by Mössbauer spectroscopy. On isochronal annealing up to about 100 K, trapping of two different types of mobile interstitials at the57Co probe atoms was observed as additional lines in the spectra. These are characterized by centre shifts of +0.44 mm/s and +0.41 mm/s relative to57Co on substitutional lattice sites and by large quadrupole splittings of 1.50 mm/s. Above 640 K, vacancy trapping was observed. With the onset of recrystallization, dislocation pinning was found in both the neutron irradiated and the cold worked sample.