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用透射电镜、正电子湮没和电阻测量,研究了NiTi形状记忆合金的组织结构与相变滞后的关系。结果表明,经不同时效制度处理的组织,其相变温度滞后大小的顺序是:片状马氏体>R相>束状马氏体。Ti11Ni14相质点周围的共格应力场对这些相的可逆转变起障碍作用。正电子湮没多普勒展宽能谱S参数值与试样的温度滞后值之间存在线性关系,从而确认Ti11Ni14相析出的错配位错密度及由此而建立的晶体中弹性应力场分布是决定NiTi合金相变温度滞后的主要因素。
The relationship between microstructure and phase transformation delay of NiTi shape memory alloy was studied by transmission electron microscopy, positron annihilation and resistance measurement. The results show that the order of the phase transition temperature hysteresis of the organizations treated by different aging systems is: sheet martensite> R phase> bundle martensite. The coherent stress field around the Ti11Ni14 phase particles has an impediment to the reversible transformation of these phases. There is a linear relationship between the S-parameter value of positron annihilation Doppler spread spectrum and the temperature hysteresis of the sample, so as to confirm the misfit dislocation density of Ti11Ni14 phase precipitates and the elastic stress distribution in the crystal NiTi alloy phase transition temperature hysteresis of the main factors.