Ti-Ni 形狀記憶合金의 마르텐사이트 變態에 미치는 時效 및 加工熱處理의 影響 = Effects of Aging and Thermo-mechanical Treatment on the Martensitic Transformation of Ti-Ni Shape Memory Alloys

다국어 초록 (Multilingual Abstract)

Effects of heat treatment conditions on the martensitic transformation behavior and precipi-tation processes in Ti-49.6 at. % Ni and Ti-51.5 at . % Ni shape memory alloys were investigated by electrical resistance measurement, X-ray diffraction, microscopy and SEM(EDAX). The Ms tem-perature was little affected by the cooling rate and aging temperature in Ti-49.6 Ni alloy, while that of Ti-51.5 Ni alloy was found to be remarkably altered due to the quenching effect. The Ms temperature of Ti-49.6 Ni alloy annealed after 30% cold rolling increased with increasing annealing temperature. This was attributed to the rearrangement and annihilation of a high density of dislocations introduced by cold work. However, the Ms temperature of Ti-51.5 Ni alloy was decreased with increasing annealing temperature, because it was significantly influenced by the quenching effect rather than dislocations. There was no change in microstructure of Ti-49.6 Ni alloy in spite of the variation of aging times at various temperatures. In case of Ti-51.5 Ni alloy, However, the volume fraction of the precipitate phases such as Ti_11 Ni_14, Ti_2Ni_3 and TiNi_3 was increased with increasing aging times at 600℃
after solution treatment. And also, the diffusional transformations took place, similar to those in supersaturated alloys.