【作者】 刘丽娟；

【导师】 霍永忠；

【作者基本信息】 四川大学 ， 材料学， 2002， 硕士

【摘要】 形状记忆合金由于特有的形状记忆效应和超弹性，在核反应堆等核环境下用作连接器和控制器已引起核材料科学家的关注。由于辐照会改变形状记忆合金的相变特性，研究其改变的规律及机理对形状记忆合金辐照环境下应用的可靠性和可行性是十分必要的。 本论文用1.7MeV电子辐照了经过适当热处理后的三种形状记忆合金(CuZnAl、NiTi和NiTiCu)，通过示差扫描量热仪(DSC)、正电子湮没分析(PAT)、X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)等实验方法研究了形状记忆合金的辐照效应。综合实验结果和辐照效应、相变热力学等理论，探讨了电子辐照对形状记忆合金的相变特性的影响机理。 现将研究结果总结如下： CuZnAl合金电子辐照后产生了马氏体稳定化，马氏体逆相变温度A_s向高温飘移，M_s的变化因辐照状态不同而呈现不同的变化趋势，辐照马氏体相(室温)使M_s点降低，而辐照母相(高温)使M_s升高。NiTi形状记忆合金辐照后A_s上升，M_s下降，但对R相变影响很小。电子辐照提高了NiTiCu合金的A_s点，但对M_s几乎没有影响。比较实验结果发现，电子辐照对CuZnAl的相变温度影响最大，对NiTi的影响最小，对NiTiCu的影响居中。CuZnAl、NiTi和NiTiCu形状记忆合金在低能量电子辐照条件下不会发生非晶化转变。 电子辐照影响形状记忆合金性能的机理主要是辐照产生点缺陷，增加缺陷浓度。缺陷的迁移和聚集并与样品中原有缺陷相互作用，钉扎相界面、影响马氏体变体应变场和改变材料的有序度等。电子辐照对不同合金的影响与原子的离位阈能、空位形成能和迁移能的大小有关。 形状记忆合金的相变特性与马氏体相变密切相关。我们从马氏体相变热力学的角度出发，利用过去理论工作中建立的马氏体相变热力学模型对相变中材料的内部能量的变化进行了初步分析。更多还原

【Abstract】 Coupling devices and actuators using shape memory alloys (SMAs) are attracting interest for applications in the fields of nuclear engineering and space technology on account of their shape memory effect and Pseudoelasticity. In view of the potential change of their phase transformation characteristics in irradiation,it is necessary to know the effect of irradiation on the shape memory behavior of the alloy.In this paper,Specimens of CuZnAl,NiTi and NiTiCu shape memory alloys were irradiated with an energy of 1.7MeV electron over different dose after respective heat treatments. Then,the irradiation effect on the transformation temperatures,the latent heat of phase transformation,the defect production and the microstructure of the specimens have been studied by means of differential scanning calorimeter (DSC),positron annihilation technology (PAT),X-ray diffraction (XRD),scan electron microscope (SEM) and transmission electron microscope (TEM). Summing up the experiment results and the theories of the irradiation effecU the thermodynamics of phase transformation,the influencing mechanism of the electron irradiation to the SMAs was discussed.Now the experiment results are summarized as follows:The phase transformation of the CuZnAl,NiTi and NiTiCu SMAs finally haven’t gone to the amorphization phase after low energy electron irradiation,but the transformation temperatures were altered. The martensite of CuZnAl alloy was stabilized by the irradiation in the sense that the reverse transformation temperature(As) was higher than before. However,the start temperature of martensitic transformation (AQ showed variety because of the irradiation states:the Ms of the specimen irradiated in high temperature (parent phase) increased and that,the Ms of the specimen irradiated in room temperature (martensitic phase) decreased. The As increased and Ms decreased of the NiTi alloy,but the R-phase transformation has little been changed. For the NiTiCu alloy,the irradiation raised the As,whereas had little influence to the Ms.The mechanism of the irradiation effect to the SMAs might be due to that the point defects induced by electron irradiation make the lattice distortion of martensitic phase and raise the defect concentration. The defects would congregate and migrate to the exiting twin boundaries of martensite,affect the strain enery of the martensitic variants and change the disordering of the crystallographic structure. The extend of irradiation effect to the three kinds of the SMAs are different,and it is related to their displacement energy vacancy forming-energy and vacancy moving-energy.The transformation behavior of the SMAs is tied up to the martensitic phase transformation. On the base of the former theory work,using developed thermodynamical modeling of the martensitic transformation,the shift of the interior energy is elementarily analyzed.更多还原