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

Eddy-current parameter f(0) of the N26T3 steel has been studied as a functi on of both the aging temperature T-ag = 20-800 degreesC and the time tau of exposure to a constant temperature of 550 and 600 degreesC up to 6 h. In t he initial state, the steel had two phases: (1) cooling-induced martensite + austenite (alpha + gamma) or (2) strain-induced martensite + austenite (a lpha' + gamma). The parameter f(0) drops monotonically as tau increases, an d this drop is the faster, the higher T-ag. The parameter f(0) changes nonm onotonically with the aging temperature. In addition to the initial two-pha se structures, the one-phase gamma structure has also been studied. The par ameter f(0) grows monotonically with the plastic cold strain and changes no n-monotonically with the aging temperature (20-800 degreesC). Observed chan ges in f(0) have been explained.