Effect of structure of aging metastable austenitic steels on the signal from an eddy-current transducer

Eddy-current parameterf ₀ of the N26T3 steel has been studied as a function of both the aging temperatureT _ag=20–800°C and the time τ of exposure to a constant temperature of 550 and 600°C up to 6h. In the initial state, the steel had two phases: (1) cooling-induced martensite+austenite (α+γ) or (2) strain-induced martensite+austenite (α′+γ). The parameterf ₀ drops monotonically as τ increases, and this drop is the faster, the higherT _ag. The parameterf ₀ changes nonmonotonically with the aging temperature. In addition to the initial two-phase structures, the one-phase γ structure has also been studied. The parameterf ₀ grows monotonically with the plastic cold strain and changes nonmonotonically with the aging temperature (20–800°C). Observed changes inf ₀ have been explained.