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测定了热循环过程NiTi合金的电阻-温度曲线;研究了热循环周数,温度和应力复合作用以及冷加工等因素对NiTi合金相变行为的影响。结果表明:热循环及应力均能促进R相变,改变马氐体转变温度。在升降温过程中进行了X光衍射研究。在高温时,合金具有B2结构,晶格常数a_0=3.01.随着温度下降,在R相变范围B2(110)衍射线逐步宽散,最后分裂为d=2.144(I)及d=2.10(R)的衍射峰,同时出现马氏体衍射线.在马氏体转变温度以下仍保留一定数量的I相和R相。由此估计降温相变过程为:B2→I+R+M.
The resistance-temperature curve of NiTi alloy during thermal cycling was measured. The effects of the number of thermal cycles, the combination of temperature and stress and the cold working on the phase transition behavior of NiTi alloy were investigated. The results show that both thermal cycling and stress can promote R phase transformation and change the transition temperature of stirrup. X-ray diffraction studies were carried out during the rise and fall of temperature. At high temperature, the alloy has a B2 structure with a lattice constant a0 = 3.01. As the temperature decreases, the diffraction line of the B2 (110) phase is gradually broadened and finally divided into d = 2.144 (I) and d = 2.10 R) diffraction peaks appear at the same time as the martensite diffraction line.At the same time, a certain amount of I phase and R phase remain in the martensitic transformation temperature. Therefore, the process of estimating the phase transition temperature is: B2 → I + R + M.