Identification of lattice vacancies in the B2-phase region of Ni–Al system by positron annihilation

The point defects of B2-type intermetallic compound Ni–Al have been investigated as a function of different Ni compositions ranging from 47 to 55 at.% by means of positron lifetime and coincidence Doppler-broadening (CDB) measurements. The position lifetime of the annealed samples, expressed by single-component lifetime of τ = 170–180 ps, indicates positron saturation trapping at single vacancies in Ni–Al samples. The CDB measurements have been applied to identify these vacancy-type defects formed on the Ni sublattice in the B2-phase Ni–Al alloys.