Study of the lattice defects in NiAl by positron annihilation

The structural defects, quenching defects and electron-irradiation defects in the intermetallic compounds NiAl have been studied with the positron annihilation technique. The recovery behaviour of quenching defects and irradiation defects have been inverstigated. Two distinct recovery stages have been found, one at about 28 deg C and the other at about 500 deg C. The experimental results show that the low-temperature stage is due to the annealing out of the divacancies and the high-temperature stage is due to the annealing out of the vacancies; and the density of the conduction electrons at the vacancies and the lattice interstitial sites are nearly equal to each other, but the momentum of the conduction electrons at the vacancies is lower than that at the latties interstitial sites in NiAl