Acoustic emission during thermoelastic martensitic transformations in titanium nickelide under isothermal loading

Acoustic emission during thermoelastic martensitic transformations in titanium nickelide is investigated. Phase transitions are initiated by loading the specimen to 200 MPa under isothermal conditions. It is found out that deformation buildup and acoustic emission in the loading-unloading cycles are observed in the first cycle only, during further cycles the acoustic emission is comparable to the background, while the deformation buildup and recovery are not associated with martensitic transformations. It is shown that recovery of the deformation built up during loading occurs due to heating to 600 °C, with the major part of accumulated deformation undergoing recovery already at 250 °C and recovery of its minor part observed at 400 °C. This behavior of acoustic emission and accumulation and recovery of deformation provide evidence of martensitic phase stabilization during cycling of martensitic transformations under conditions of thermo-mechanical cycling. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 89–94, February, 2008.