TRANSFORMATION BEHAVIOR OF NiTi SHAPE MEMORY ALLOYS TREATED BY THERMOMECHANICAL PROCESSING USING DSC

Abstract: In the present study the effect of thermomechanical treatment (cold work and annealing) on the transformation behavior of NiTi shape memory alloys was studied. Differential scanning calorimetry was used to determine transformation temperature and its relation to precipitates and defects. Three alloys including Ti-۵۰.۳at.% Ni, Ti-۵۰.۵at.% Ni (reclamated orthodontic wires) and ۵۰.۶at.% Ni alloy were annealed at ۶۷۳ K and ۷۷۳ K for ۳۰ and ۶۰ min after ۱۵% cold rolling. It was found that the transformation characteristics of these alloys are sensitive to annealing treatment and composition. The temperature range of transformation is broadened during cold working and after subsequent annealing, the intermediate phase was appeared. The peaks become sharper and close together on each cooling and heating cycle with increasing annealing temperature and time

کلیدواژه ها:

NiTi ، Shape memory alloy ، Thermomechanical treatment ، Cold working ، Annealing ، DSC.