A study of cellular decay in austenite alloys using an applied eddy-current transducer

The eddy-current parameter f(0) of the N36K10T3 invar has been studied in t he range of aging temperatures from 600 to 900 degreesC. The maximal drop i n f(0) has been observed at the temperature T-ag = 800 degreesC and the dro p in this parameter was the larger, the longer the aging process. The drop in this parameter is caused by the cellular decay process in the solid solu tion, which depletes the austenite of nickel and titanium. The parameter f( 0) increases notably (from 4 to 46 kHz) when crystals of low-temperature ma rtensite (alpha -phase) are generated in samples of the N26T3 steel with 10 0% cellular decay. This high value (f(0) = 46 kHz) persists at T-ag < 400<d egrees>C and drops by a factor of 4.5 over the interval 400 < T-ag < 600 de greesC because the ferromagnetic alpha -phase transforms to the paramagneti c phase-hardened austenite (alpha --> gamma (ph)). Aging of the phase-harde ned austenite in the steel with cellular decay at T-ag = 700 degreesC incre ases the parameter f(0) by a factor of two (from 10 to 20 kHz) because the ferromagnetic alpha -phase is generated when the aged phase-hardened austen ite transforms to the martensite (gamma (ph) --> alpha) as a result of cool ing the steel from the aging to room temperature.