This work presents a study of the development of the two-way shape memory effect (TWSME) by themomechanical training and its degradation due to working cycles in a shape memory alloys (SMAs) spring. A TWSME extension spring that could extend upon heating and contract upon cooling was obtained by constrained annealing and thermomechanical training. A stable TWSME recovery rate can reach 60-70% after training for 200 cycles. The investigation showed that constrained annealing temperature and the thermomechanical training procedure had a great effect on the TWSME. After 1000 working cycles, the TWSME recovery rate still maintained at 45% stably. The effect of the thermomechanical training on transformation characters was also investigated by differential scanning calorimetry (DSC). The inverse martensitic transformation temperatures increased and martensitic transformation temperatures decreased with increasing thermomechanical training cycles, which was attributed to the dislocations introduced into the TiNi shape memory alloys.

In this work, Ti-49.8 at.% Ni shape memory alloy (SMA) thin films were irradiated by 60-keV protons with two types of doses: 5

In this work, Ti-50.6 at.% Ni shape memory alloy were solution annealed at 800℃ for 20min and quenched in icy water, further annealing were done at 380℃ for 1h, and then irradiated with 1.7MeV electron at the fluence of 3.2×1020-12.8×1020m2. The evolution of transformation temperatures was studied by differential scanning calorimeter (DSC). Effect of annealing on the evolution of multiple-step transformation temperatures also investigated. Heat treatment and irradiation had a prominent effect on the transformation, but with different characteristics. The M1 (the first R-phasefimartensite transformation) showed little change after irradiation, but the M2 (the second R-phasefimartensite transformation) transformation temperature decreased with increasing electron fluence and disappeared at the fluence of 12.8×1020m2. Heat treatment causes the shift of R-phase transformation start/finish temperature (Rs=Rf ) to lower temperature and the shift of M1 and M2 transformation temperatures to higher temperature. The peaks of M1 and M2 almost merged into one peak with increasing annealing temperature. The effects of irradiation and annealing on the transformation characteristics are not exchangeable, so irradiation is also an important method for the study of condensed matter.

The effect of irradiation on the martensitic transformation of TiNi shape memory alloys was studied by transmission electron microscopy (TEM) with in situ observation and differential scanning calorimeter (DSC). The results of TEM and DSC measurements show that the microstructure of samples is R phase at room temperature. Electron irradiations were carried out using several different TEM with accelerating voltages of 200, 300, 400 and 1000kV. Also the accelerating voltage in the same TEM was changed to investigate the critical voltage for the effect of irradiation on phase transformation. It was found that a phase transformation occurred under electron irradiation above 350kV, but never appeared at 340kV or lower accelerating voltage. Such phase transformation took place in a few seconds of irradiation and was independent of atom diffusion. The mechanism of electron-irradiation-induced the martensitic transformation is due to displacements of atoms from their lattice sites produced by the acceleratedelectrons. The critical displacement energy of TiNi SMAs is B18 eV from the results.

TiNiCu shape memory alloy samples were irradiated by 400 keV Xe+ ions at room temperature. The in situ TEM observation showed that samples were amorphized at ～0.4dpa and the recrystallization after amorphization started when annealing at 550K and basically finished at 1023K.