Structural Changes during Thermal and Radiation Impacts in a Stainless Steel Alloyed with Titanium

Abstract

Radiation and structural-phase transformations in Fe–16% Cr–15% Ni–3% Mo austenitic steel in the initial and the titanium-alloyed states were studied by measuring the residual electrical resistance after irradiation with 5-MeV electrons and isochronous annealing. Vacancies migrate at temperatures below 320 K and form vacancy clusters upon irradiation. Due to the migration of vacancies during irradiation and upon the dissociation of vacancy clusters during isochronous annealing above 400 K, the separation of the solid solution occurs, which is accompanied by an increase in the electrical resistance. At temperatures above 700 K, the state of the steels, non-irradiated among them, approaches equilibrium due to thermal diffusion. In this case, all the dependences of the electrical resistance on temperature for each alloy irradiated at different temperatures or non-irradiated converge to a common dependence in the region of high temperatures. Doping with titanium inhibits ordering. Intermetallic compounds of Ni₃Ti composition were formed thermally upon annealing above 850 K in the alloys doped with titanium, which is accompanied by a decrease in the electrical resistance to below the initial level.