Point defects in binary Laves phase alloys

Point defects in the binary C15 NbCr₂ and NbCo₂, and C14 NbFe₂ systems on both sides of stoichiometry were studied by bulk density and X-ray lattice parameter measurements. It was found that the vacancy concentrations in these systems after quenching from 1000°C are essentially zero. The constitutional defects on both sides of stoichiometry for these systems were found to be of the anti-site type in comparison with model predictions. Thermal vacancies exhibiting a maximum at the stoichiometric composition were observed in NbCr₂ Laves phase alloys after quenching from 1400°C. However, there are essentially no thermal vacancies in NbFe₂ alloys after quenching from 1300°C. Anti-site hardening was found on both sides of stoichiometry for all the three Laves phase systems studied. Neither the anti-site defects nor the thermal vacancies affect the fracture toughness of the Laves phases significantly.