Optimization of shape memory effect in NiTi alloy

They are known for their applications that thermomechanical variants such as heat, load, pre strain, and 3rd element addition etc. strongly affect on the thermoelastic martensitic transformations and transformation characteristics which are based on shape memory effect (SME) and pseudoelasticity (PE). Furthermore, the martensitic transformation behavior, morphology and transition temperatures in NiTi-based shape memory alloys (SMAs) are strongly influenced by thermo-mechanical treatments.The alterations in transformation temperatures of equal atomic NiTi SMA have been investigated using different thermo-mechanical processes. Experimental studies carried out in order to research the effects of different heating/cooling rates on transformation temperatures of NiTi SMA. Two way shape memory effect has been brought in NiTi alloy that has one way shape memory effect using novel thermo-mechanical training method. Experiments have been conducted for time-temperature-cycle relationship where two-way shape memory effect was optimum and results have been presented in a systematical order.It has been understood with differential scanning calorimeter (DSC) tests that upon thermo-mechanical treatment, specific transformation temperatures in NiTi SMA have changed. It has been observed that transformation specific characteristics like alterations in heating/cooling rates and transformation temperatures, absorbed and released heat amount during transformations, elastic and irreversible energy quantities have changed extensively. It has been noted that the magnitude of two-way shape memory effect varied with annealing temperature, annealing time, pre deformation and number of training cycles.Within the scope of other research projects besides doctoral study, manufacturing of NiTi SMA has been accomplished and similar experimental studies have been conducted with the samples prepared from manufactured NiTi alloy.