温度和应变率对NiTi记忆合金相变转化率的影响

为了探讨温度和应变率对NiTi记忆合金相变转换率的影响,本文利用准静态试验机和分离式Hopkinson压杆的恒应变率技术对板条状和圆柱状试样进行了不同应变率的试验,同时通过改变温度检查相变转换的速度,结果表明:在较低的10-2/s应变率下,NiTi记忆合金伪弹性变形过程自身就会有6.5℃温升,这意味着在高应变率下其性能是温度与率的耦合效应;随外界环境温度的增加,NiTi记忆合金的相变恢复速率由递增趋于一稳态值,当温度超过365K时,恢复速率趋缓至约0.014mm/s;随应变率增加,相变转换率会趋于极限,即应力诱发的奥氏体向马氏体相转化阶段在应变率超过6000/s时基本不变,表明更高的应变率已不能引起NiTi相变转换。     

Surface treatment of NiTi shape memory alloy by modified advanced oxidation process

A modified advanced oxidation process(AOP) utilizing a UV/electrochemically-generated peroxide system was used to fabricate titania films on chemically polished NiTi shape memory alloy(SMA). The microstructure and biomedical properties of the film were characterized by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), inductively-coupled plasma mass spectrometry(ICPMS), hemolysis analysis, and blood platelet adhesion test. It is found that the modified AOP has a high processing effectiveness and can result in the formation of a dense titania film with a Ni-free zone near its top surface. In comparison, Ni can still be detected on the outer NiTi surface by the conventional AOP using the UV/H2O2 system. The depth profiles of O, Ni, Ti show that the film possesses a smooth graded interface structure next to the NiTi substrate and this structure enhances the mechanical stability of titania film. The titania film can dramatically reduce toxic Ni ion release and also improve the hemolysis resistance and thromboresistance of biomedical NiTi SMA.     

A study on the variations of the electrical resistance for NiTi shape memory alloy wires during the thermo-mechanical loading

In order to use NiTi wires as strain or stress sensors, the variations of electrical resistance of Ti-50.8 at%Ni wires during thermo-mechanical loading are studied in this paper. The results show that it is possible to use the NiTi wires as strain sensors, but it is difficult to use NiTi wires as stress sensors.     

形状记忆合金相变温度常用测量方法的比较研究

采用差示扫描量热法(DSC)、电阻法和应用负载法对热处理后的NiTi记忆合金丝试样的相变温度进行了测试对比,探讨了3种测量方法的准确性、一致性和适用性.结果表明,电阻法和应用负载法测得的相变温度相近,而DSC测得的相变温度与它们相差超过20℃.同时,测试次数对前2种方法的测量结果有一定影响,而负载大小和形变模式与应用负载法的测量结果相关.     

NiTi SMA电沉积电流密度对耐蚀性的影响

系统研究了在不同电流密度下阴极电沉积法制得的Ti-O膜改性膜的表面形貌及耐腐蚀性能。得出在电流密度5 mA/cm2下阴极沉积得到的Ti-O膜非常均匀致密,有较小的裂纹;但电流密度为20mA/cm2下沉积的试样有较好的热力学稳定性和较优异的耐腐蚀性能。     

NiTi合金的应力—温度相图

借助了SMA-1型形状记忆合金综合性能测试仪的（ε-R-T）曲线,绘制成50.8%（原子）Ni-Ti合金应力一温度相图,进而讨论了该相图的特性及其应用。     

应力诱发相变的电子显微镜动态研究方法

利用透射电镜（ＴＥＭ）和扫描电镜（ＳＥＭ）用加载样品台的手段,并结合ＮｉＴｉ形状记忆合金中的应力诱发相变,简单介绍了动态研究的基本方法。     

THE CRYSTALLIZATION KINETICS OF AN AMORPHOUS Ti-RICH NiTi FILM

1. IntroductionIn recent years, many studies have been made on shape memory alloys (SMA) concentrating in its martensitic transformation, shape memory effect (SME) and superplasticity[1--4].SMA film is an excellent candidate of actuator for MEMS (microelectromechanic systems)because it is capable of generating high strain and force compared with other actuationmaterial used as mic.oactuators[5]. Now, the research on SMA film is mainly concentratedon Ni-Ti or Ni-Ti-X alloys, which posse…     

纳米SrFe12O19磁性能对NiTi合金、316L不锈钢血液相容性的影响

用溶胶凝胶法制备纳米SrFe12O19磁性粉末,并用磁强计检测SrFe12O19粉末的磁性能,在NiTi合金、316L不锈钢表面用溶胶凝胶法制备含SrFe12O19磁性粉末的TiO2薄膜,并用X射线衍射仪分析薄膜成分.测试不同层数薄膜的微磁场强度,并对这些薄膜测定动态凝血时间和溶血率,以研究不同的表面微磁场强度对材料血液相容性的影响.结果表明:材料表面的微磁场强度愈高,材料血液相容性愈好.     

Porous Metal Sheets of NiTi made by Wet Powder Spraying

As a promising method to produce thin porous NiTi sheets, Wet Powder Spraying (WPS) is applied for NiTi powders. Layers with a thickness of 150 μm are obtained from pre‐alloyed NiTi powders with a particle size of < 12 μm. Optimized process control for spraying and sintering was used. Microstructure and phase formation is characterized. The sheets with a porosity of 15 % show a high pseudoelastic flexibility at room temperature. Phase transformation temperatures are determined by Differential scanning calorimetry (DSC). The one way effect could be demonstrated.