STUDY OF THE PRECIPITATE FORMATION IN COLD-WORKED AGING Fe—35.2 at %Ni—2.9 at %Ti ALLOY BY POSITRON ANNIHILATION SPECTROSCOPY AND RESIDUAL RESISTIVITY MEASUREMENT

In this work, positron annihilation spectroscopy and residual resistivity measurements was carried out to investigate the evolution of microstructure of cold-worked aging Fe—35.2 at %Ni—2.9 at %Ti alloy at step-wise annealing. It was found that nanoparticles of the intermetallic γ′-phase NiTi, formed at dislocations during annealing of vacancy defects, reduce the efficiency of positron trapping by dislocations and this effect depends on the degree of deformation. In particular, the magnitude of the positron trapping blocking effect is determined by the ratio of the number of deep positron traps to the number of precipitate particles present at dislocations.