镍钛基轻稀土合金薄膜的组合纳米量热与微结构研究

Ternary NiTi-based shape memory alloys have been shown to achieve a higher phase transition temperature, which can be used in high temperature environment. But a higher phase transition temperature will need to add a lot of third precious metals. Industrial applications need to develop new shape memory alloy system with characters of low costs and high phase transition temperature. China, especially the Inner Mongolia Autonomous Region have a very rich rare earth resources. But the primary rare earth products are still raw light rare earth. The development of the rare earth industrial needs to strengthen the basic research of the rare earth and extend the application of the rare earth. The practices have proven that the performance of a metal alloy can be greatly improved by adding a small amount of rare earth. But the rare earth has not yet been applied to the shape memory alloy field. In this proposal, the crystallization, the phase transition, the thermal fatigue and other thermodynamic properties of the NiTi-based light rare earth alloy films with multi-component and a variety of rare earth elements will be studied by using the combinatorial nanocalorimetry. The micro-structure of the films will be also studied by using the X-ray diffraction and the transmission electron microscopy. The microscopic mechanism of the performance change of the NiTi alloy will be explored. And the relationship between the number and concentration of the valence electrons in the NiTi-based light rare earth alloy systems and the phase transition temperature will be studied. The NiTi-based light rare earth alloy thin film with best performance will be found. This research will provide a theoretical and experimental basis for the application of the shape memory alloys and the rare earth.

三元镍钛基形状记忆合金已经被证明可以达到较高的相变温度，从而可以应用于高温环境，但是较高的相变温度需要添加大量的第三元贵金属，工业应用的扩展需要发展低值的、高相变温度的形状记忆合金系统。我国尤其是内蒙古自治区拥有非常丰富的稀土资源，但是稀土产品仍以轻稀土初级原料为主，稀土工业的发展需要加强稀土的基础研究并扩展稀土的应用。大量实践证明，少量添加稀土就可以大大地改善金属合金的性能，但是稀土还没有被应用于形状记忆合金领域。本项目拟采用组合纳米量热法研究多组分、多种稀土元素添加的镍钛基轻稀土合金薄膜的晶化、相转变、热疲劳等热力学性能，采用X射线衍射和透射电子显微镜研究合金薄膜的微结构，探讨稀土添加所导致的镍钛基合金热力学性能变化的微观机制，分析镍钛基轻稀土合金系统中价电子的数量和浓度与相转变温度的关系，最终获得性能最优的镍钛基轻稀土合金薄膜，为形状记忆合金和稀土的应用研究提供理论和实验基础。

我国尤其是内蒙古自治区拥有非常丰富的稀土资源，但是稀土产品仍以轻稀土初级原料为主，稀土工业的发展需要加强稀土的基础研究并扩展稀土的应用。大量实践证明，少量添加稀土就可以大大地改善金属合金的性能，但是稀土还没有被应用于形状记忆合金领域。.本研究制备了多组分的添加轻稀土镧、钕、镨的三元镍钛基合金，使用能量色散谱仪测定了合金的化学成分，采用差示扫描量热法研究了合金的晶化、相变、热疲劳等热力学性能，使用X射线衍射仪、扫描电子显微镜和透射电子显微镜分析了合金的微结构；另外还分析了镍钛基轻稀土合金中价电子的数量及浓度与合金马氏体相变温度的关系。发现镍钛基轻稀土合金的微结构都是由近等原子比镍钛二元合金基体和镍稀土二元合金夹杂相组成的复合结构，随着稀土含量的增加，镍钛镧Ni50Ti50-xLax（x = 0.1 ~ 0.9）和镍钛镨Ni50Ti50-xPrx（x = 0.1 ~ 0.9）的马氏体相变温度逐渐降低，而镍钛钕Ni50Ti50-xNdx（x = 1 ~ 20）的马氏体相变温度略有升高。镍钛基轻稀土合金中价电子的数量及浓度与合金的相变温度无关，由于本研究保持基体中的镍含量为50 at.%，所以镍的含量也不影响镍钛基轻稀土合金的马氏体相变温度，因而推断镍钛二元合金基体与镍稀土二元合金夹杂之间的应力场是导致合金马氏体相变温度改变的原因。.此外，本研究还制备了镍钛铪合金薄膜，发现溅射态的镍钛铪合金薄膜经过加热晶化处理后，薄膜由分散在非晶相中的大的镍钛铪三元合金晶粒和小的(Ti, Hf)2Ni夹杂相组成，随着热循环次数的增加，晶化逐渐完成，马氏体相变温度逐渐降低。本研究还制备了镍钛二元合金薄膜，发现经过热处理后的镍钛二元合金薄膜中可以形成一种纳米尺度的B2相和R相的互织结构。本研究还研制了一套组合纳米量热装置，能够实现纳米厚度合金薄膜相变温度的测量。