Atomic Defects in Metals · Cr

This chapter discusses the properties of atomic defects in pure chromium (Cr). Only few results on point defects in chromium are known, and the available data raise some questions. In contrast to the other bcc metals of group VI B (Mo, W), chromium can be obtained only as relatively impure material. The solubility of interstitial impurity atoms H, O, N, C, is small near room temperature and these impurities are probably present as precipitates, at least partly. Material with RRR = 140···220 has been used for low temperature electron irradiation on polycrystals and on single crystals combined with recovery experiments (8 K···60 K). The low-temperature recovery spectrum shows prominent first-order recovery stages below 40 K, related to the annihilation of close Frenkel pairs, depending on energy and crystallographic direction of the incident electron beam. Properties of Frenkel defects (FD), self interstitial atoms (SIA), and vacancies (V) in chromium are tabulated. Resistivity recovery of electron irradiated chromium, recovery spectrum of single crystals, irradiated with different energies, and isochronal recovery of positron average lifetime chromium following electron irradiation at 20 K, are illustrated.