富Ti含量Ti-Ni合金负热膨胀本质机理及与马氏体相变的内在规律性研究

The present project focuses on the research of Ti-rich Ti-Ni alloys exhibiting unique negative thermal expansion behavior. The self-accommodation effect of martensite twin variants and the characteristics of negative thermal expansion responses of the alloy will be studied in detail, and a physical model will be built to quantitatively clarify the correlation between the macroscopic shape strains and the intrinsic crystal thermal expansions, lattice structure transitions and twin variant self-accommodations, thereby the intrinsic correlativity between the negative thermal expansion mechanism and martensitic phase transformations can be revealed. Further, studies will be performed to identify the effect of phase constituents and microstructure characteristics on martensitic phase transformations, and the negative thermal expansion behavior will be investigated deeply. Through establishing the inherent correlativity between the negative thermal expansion behavior and martensitic phase transformations, alloy design criterion and fabrication techniques featuring effectively control on the coefficient of thermal expansion will be obtained. Moreover, the isothermal and athermal nature of martensitic phase transformations of the alloys will be studied in detail, enabling the inherent law between the stability of negative thermal expansion and isothermal/athermal kinetics of martensitic phase transformations, under different thermal aging and thermal cycling conditions, to be found. It is expected that the present research will enrich the understandings and underlying principles of the negative thermal expansion behavior of Ti-rich Ti-Ni alloys, provide guidance for designing novel metallic materials with negative thermal expansion property, in the meanwhile, offer theoretical support for developing Ti-Ni alloys and composites with near zero thermal expansion behavior and controllable coefficient of thermal expansion.

本项目以具有独特负热膨胀行为的富Ti含量Ti-Ni合金为研究对象，采用实验表征与理论分析方法研究合金的马氏体孪晶变体自协作效应和热膨胀响应规律，建立温度变化时合金形状应变与晶体固有膨胀、点阵结构转变和孪晶变体自协作等因素间量化的物理模型，揭示其负热膨胀微观机理及与马氏体相变的本质关系；研究物相组成和微观组织变化等对合金马氏体相变及热膨胀行为的影响规律，阐明合金负热膨胀行为与马氏体相变的关联规律，获得能有效调控合金热膨胀系数的材料设计依据和制备工艺；研究合金马氏体相变过程的等/变温特征属性，掌握合金在经历不同温度时效及热循环条件下其负热膨胀稳定性与马氏体相变等/变温动力学行为的内在规律。本研究将丰富目前有限的关于Ti-Ni合金负热膨胀行为的认知和基础理论体系，为发展新型的具有负热膨胀性能的金属材料提供理论基础，并为开发具有近零膨胀行为或热膨胀系数可调控的Ti-Ni合金及复合材料提供理论指导。

在航空航天、精密光学器件和先进电子封装等温度敏感及对功能器件尺寸稳定性要求苛刻的领域，相邻部件间热膨胀不匹配及因温度改变而引起的热应力等对结构和器件的服役性能和可靠性有很大影响。研究开发出具有热膨胀系数可按需求进行调控的材料，其关键在于获得微观或宏观范畴上具有负热膨胀性能的调控体；目前对TiNi合金负热膨胀现象及行为本质的认知有限，深入研究TiNi合金的负热膨胀本质机理并全面厘清各种影响因素对其负热膨胀行为的协同作用机制具有重要的科学意义，并在开发具有近零膨胀行为或热膨胀系数可调控的新型精密合金方面具有重要的工程价值和应用前景。本项目系统研究了具有负热膨胀特性富Ti含量TiNi合金的马氏体相变与热膨胀行为，阐明了合金在温度变化过程中宏观形变与晶体结构转变之间的本质关系并根据拓扑理论建立了量化的物理模型，揭示了TiNi合金负热膨胀响应的微观机理，丰富了对金属材料负热膨胀的认知并为材料优化设计和制备提供依据；全面研究了温度循环条件下TiNi合金马氏体相变及负热膨胀响应的变化规律及微观机理，阐明了循环相变和温度作用下合金显微组织及位错结构演化特征，为TiNi合金用于温度敏感及对功能器件尺寸稳定性要求苛刻的领域提供理论指导与评价依据；研究了具有微纳米尺度调控第二相颗粒的TiNi合金基复合材料，阐明了调控相对复合材料热膨胀系数的影响规律并建立了定量计算模型，为热膨胀系数可控TiNi复合材料的设计和制备提供理论指导；研究了低温时效TiNi合金中出现的反常双程形状记忆效应，阐明了由反常向正常双程形状记忆效应转换的临界条件和微观机制，系统研究了TiNi合金高达三万次温度循环作用下的相变行为与显微组织演变，揭示了合金优异热循环稳定性的微观机理，为TiNi合金在高周循环温度场条件下的服役行为研究提供理论基础和功能疲劳评价依据。