Electro-thermomechanical behaviour of a Ti-45.0Ni-5.0Cu (at.%) alloy during shape memory cycling

In the present paper, electrical resistance (ER) changes are measured simul taneously with the stress-assisted two-way memory effect (SATWME) in Ti-45. 0Ni-5.0Cu (at.%) wires during thermal cycling (max. 15 cycles) for several different stress levels. Interesting qualitative evolutions of the epsilon- ER-T loops during: cycling are observed as a function of the applied stress . On cooling, for stresses higher than 175 MPa, a clear deviation of the E- T curves is verified and the reversion of this anomaly is not observed duri ng heating. After some cycles, serrations are frequently observed on the ER -T loops essentially below M-f and above A(f), indicating an interaction be tween the formation and reversion of oriented martensite variants with the defects introduced during the thermomechanical cycling. A linear relationsh ip is observed between ER and a for the direct and reverse transformation r anges. The characteristic slope d(Delta R/R)/d epsilon is slightly dependen t on the applied stress and on the number of thermal cycles. (C) 1999 Elsev ier Science S.A. All rights reserved.