TiNi基块体记忆合金功能特性的循环稳定性已成为其满足长寿命航天器、弹热制冷等重要应用的最大障碍。申请人前期发现在适当成分的TiNiCu合金中添加Nb元素后，块体合金在热循环时表现出稳定的马氏体相变与良好的冷变形能力。因此，本项目选择不同成分的TiNiCuNb合金，研究冷加工TiNiCuNb合金微观组织演化规律，分析马氏体孪晶、β-Nb相与塑性变形诱发位错之间的交互作用，阐明合金非晶化的微观本质；明确晶粒尺寸与马氏体亚结构、Ti2Cu相析出之间的关系，获得TiNiCuNb合金微观组织调控机理；分析Ti2Cu相、β-Nb相与晶粒尺寸、晶体学相容性耦合作用对合金热诱发马氏体相变与超弹性循环稳定性的影响规律与机制，为发展具有稳定功能特性的TiNi基合金提供新思路。相关研究成果还将丰富母相与马氏体晶体学相容性理论，为发展其他高性能多铁性材料提供借鉴。

The cycling stability of functional characteristics has become the major problem for extending the applications of TiNi-based bulk shape memory alloys. The applicant previously found that after adding Nb in TiNiCu alloys with proper composition, the bulk alloy shows stable thermally-induced martensitic transformation during thermal cycling and good cold-work ability. Therefore, the present project selects the different TiNiCuNb alloys with different compositions and investigates the microstructural evolution of TiNiCuNb alloys during cold-work, and illustrates the amorphization mechanism by considering the interaction between martensite twin, β-Nb and dislocations introduced by cold-work. Secondly, the relationships between grain size and martensite substrate, precipitation behavior of Ti2Cu phase are revealed to establish the regulation mechanism of microstructure for TiNiCuNb alloys. In the last part, the coupling effect of Ti2Cu phase, β-Nb phase and grain size, crystallographic compatibility on the cycling stability of thermal-induced martensitic transformation and superelasticity is investigated and the mechanism behind is revealed. This may provide the new way to develop the TiNi-based bulk alloy with stable functional characteristics. The related results also enrich the theory of geometric compatibility between martensite and parent phase and provide helpful experiences for development of other high performance multiferroic materials.