超细晶孕育剂变质细化铜基形状记忆合金的制备及力学与阻尼性能研究

Cu-based shape memory alloys (SMAs) as a kind of important damping materials have incontrovertible performance advantage and objective demand. However, intergranular fracture due to coarse grains is one of main factors to restrict their practical application. This project prepares to take the CuAlMn SMA as the research object and to significantly refine its grains by the refining effect of ultra-fine grain inoculants. By phase analysis and microscopic observation, the effects of grain refinement of the parent phase on the phase composition, and the morphology, size, lamellar spacing, microstructure and slip characters of interfaces of the martensite and twin substructure of the CuAlMn SMA after the martensitic transformation are clarified. On this foundation, the tensile property and fracture characteristics of the alloy are investigated to evaluate the influence of grain refinement on tensile strength of the alloy. As a result, the mechanism on the fracture and improved mechanical property of the alloy after refinement are revealed from the rotation and mutual coordination of grains, stress concentration, etc. The damping response characteristics of the alloy after refinement are systematically obtained in terms of internal friction measurement. The damping response rule of the alloy on grain size and corresponding microstructure evolution is disclosed from following two aspects: the number change of sliding interface per unit volume and the interface sliding characteristic controlled by lamellar spacing and grain boundary constraint. Finally, the relationship and its mechanism between the mechanical and damping properties of the refined alloy are elucidated. The present research will provide new ideas for developing novel Cu-based SMAs with high strength and high damping properties.

铜基形状记忆合金是一类重要的阻尼材料，拥有明确的性能优势和目标需求，但晶粒粗大导致的沿晶断裂是其实用性受限的主要因素之一。本项目以CuAlMn形状记忆合金为研究对象，设计新型超细晶孕育剂，通过其显著的变质细化作用实现合金的晶粒细化。开展物相分析和微观组织观察，阐明晶粒细化对马氏体相变后合金的相组成，以及马氏体和孪晶亚结构的形态、尺寸、片层厚度、界面微结构、界面滑移性的影响规律。在此基础上，考察材料的拉伸性能和断裂特性，评估晶粒细化对材料拉伸强度的影响，从晶粒转动及相互间协调，应力集中等角度揭示断裂机理及力学性能提高机制；进行内耗测试，获得材料系统的阻尼响应特征，从晶粒细化后单位体积滑移界面数量的变化及界面滑移性受片层厚度、晶界约束两个角度，揭示晶粒尺寸及相应微结构的变化对材料阻尼性能的响应规律。最后，阐明力学与阻尼性能的关联规律与机理。此研究可为高强高阻尼铜基形状记忆合金的开发提供新思路。

铜基形状记忆合金是一类重要的阻尼材料，拥有明确的性能优势和目标需求，但晶粒粗大导致的沿晶断裂是其实用性受限的主要因素之一。本项目以CuAlMn形状记忆合金为研究对象，设计新型超细晶孕育剂，通过其显著的变质细化作用实现了合金的晶粒细化。设计并制备了Cu-Zr及Al-La-B孕育剂，并分别采用此两种孕育剂成功地对Cu-Al-Mn形状记忆合金的晶粒进行了细化，分析了两种孕育剂对Cu-Al-Mn形状记忆合金的细化效果，揭示了细化机理。进行了变质细化Cu-Al-Mn 形状记忆合金的轧制及热处理，同时对热轧前后以及热处理前后样品的微观组织进行了观察，并对其形成机理进行了分析。开展了不同平均晶粒尺寸Cu-Al-Mn形状记忆合金阻尼行为的系统测试与分析， 同时亦考察与分析了晶粒尺寸、母相时效、机械轧制对Cu-Al-Mn形状记忆合金马氏体相变行为及力学性能影响的规律与机理，并从相界面、孪晶界面以及晶界的密度的变化、马氏体以及孪晶尺度的变化、界面滑移性的变化、位错滑移性的变化等角度综合分析了Cu-Al-Mn形状记忆合金的强韧化对阻尼性能影响的机制。揭示了变质细化 Cu-Al-Mn 形状记忆合金阻尼行为变化及阻尼本领提高的机理，明确了变质细化 Cu-Al-Mn 形状记忆合金阻尼性能与力学性能间相互作用规律与机理。经过孕育细化及后续的热处理或热加工，Cu-Al-Mn形状记忆合金的力学及阻尼性能均获得了大幅度提高。目前该合金的制备工艺成熟，综合性能优异，本项目研究团队正在积极推进所得成果的转化与应用，此外，此研究又可为高强高阻尼铜基形状记忆合金的开发提供新思路。本项目基金支持下，在SCI/EI收录国际知名期刊发表学术论文11篇，同时获授权中国发明专利3项。