过渡元素掺杂NiTi合金的第一性原理研究

A First Principle Study On NiTi Alloyed With Transition Elements

摘要:

本文采用基于密度泛函理论的第一性原理方法系统的计算了3d、4d和5d过渡元素掺杂的NiTi合金晶格参数、形成能、弹性常数和电荷密度，探讨了合金元素的占位倾向以及对马氏体相变温度的影响。计算结果表明，V、Cr、Mn、Fe、Co、Pd、Cu倾向于占据Ni位；Sc、Y、Zr、Hf倾向于占据Ti位。V、Cr、Mn、Fe、Co各族元素和Pd、Pt取代Ni，V、Cr、Mn、Fe各族取代Ti能够不同程度的降低NiTi合金的相变温度Ms；Hf、Zr、Au、Ag取代Ni以及Sc、Y、Hf、Zr取代Ti为能够升高NiTi合金的相变温度Ms；Cu取代Ni则基本不改变NiTi合金的相变温度Ms。这些结果与实验结果一致，进而从微观角度解释了合金元素对相变温度的影响规律。

Abstract:

The lattice parameters, formation energy, elastic modulus and differential charge density of NiTi alloyed by transition elements have been calculated by using the first principle method based on density functional theory (DFT). Then we can discuss the site preference of transition elements in NiTi and the influence of them on the martensitic transformation temperature of NiTi. The results show that, when added to NiTi Alloy: (1) the groups of V, Cr, Mn, Fe, Co, Pd, Cu prefer the Ni-sites; (2) Sc, Y, Zr, Hf prefer the Ti-sites; (3) Zn and Cd can’t form a stable structure. In a martensitic phase transformation process, the bigger C44 /C’and stronger bonding interaction means the stronger transition resistance which lead to a lower transformation temperature. By analyzing the elastics modulus and the differential charge density map of NiTi, we can infer that: (1) the replace of Ni by the groups of V, Cr, Mn, Fe, Co or by Pd, Pt and replace of V, Cr, Mn, Fe for Ti will lower the transformation temperature; (2) Hf, Zr, Ag, Au substitute for Ni and Sc, Y, Hf, Zr substitute for Ti will increase the transformation temperature; (3) transformation temperature will almost be unchanged while Cu substitute for Ni. These results are consistent with the experimental ones and we can understand the influence of alloying elements on the phase transformation temperature of NiTi from the microscopic point of view.