Ni50.1Mn24.1Ga20.3Fe5.5形状记忆合金多晶纤维的双程形状记忆效应

通过熔体抽拉技术制备Ni_50.1Mn_24.1Ga_20.3Fe_5.5多晶纤维,采用步进式热处理释放因快速凝固引起的内应力和缺陷,利用场发射扫描电子显微镜、透射电子显微镜、XRD衍射仪对其微结构和相结构进行表征,采用动态机械拉伸仪测试其相变行为和双程形状记忆性能。结果表明:热处理后原子有序度显著提高,孪晶界平直,在恒应力作用下一个热循环中母相和马氏体相的形状得到完全恢复。双程形状记忆曲线显示了热弹性马氏体相变的两个基本特征:可逆性和热滞性。在热循环实验中,纤维被加载到198 MPa时,其马氏体态总应变达到1.32%。根据热机械拉伸测量,发现相变温度遵循Clausius-Clapeyron关系式。与诸如Ti-Ni和Cu-Al-Ni的其他合金相比,Fe掺杂的纤维显示出较小的应变-应力依赖性,在恒应变输出的驱动中是有益的。

Two-way shape memory effect of Ni50.1Mn24.1Ga20.3Fe5.5 shape memory alloy polycrystalline fiber

Polycrystalline Ni-Mn-Ga-Fe fibers were prepared by melt-extraction technique.The internal stress and defects introduced by rapid solidification were modified by step-wise chemical ordering annealing.The microstructure and phase microstructure of fibers were characterized using Field Emission Scanning Electron Microscope(FESEM)and Transmission Electron Microscopy(TEM)and XRD diffraction technique.The phase transition behavior and two-way shape memory effect(TWSME)were tested using Dynamic Mechanical Analyzer(DMA).The results show that after heat treatment,the chemical ordering degree is increased,and the martensite twin boundaries are straight.Complete recoverable strains of parent and martensite phases during thermal cycles are achieved.During the two-way shape memory cycles,two characteristics of thermoelastic martensite transition are displayed in heat-treated fibers:reversibility and thermal hysteresis.In the thermal cycle test,the total strain reaches 1.32%when the fiber is loaded to 198 MPa.The thermomechanical tensile measurement shows that the phase transition temperature follows the Clausius-Clapeyron equation.Compared with other alloys such as Ti-Ni and Cu-Al-Ni,Fe-doped fiber exhibits a smaller strain-stress dependence,which is beneficial to the constant strain output.