金属材料超塑成形关键技术基础研究

The project is on the basis of the grain sizes and the proportion of phases, and systematic studies their coordinating roles on the super-plasticity and the microstructural evolution. Besides, the theory about super-plasticity of the ultrafine-grain materials at high strain rate is explored. From the aspect of energy, we analyze the microscopic changes, such as grain boundary slip, diffusion creep, nucleation and growth of the cavity, deformation and failure, et al. An energy law of superplastic deformation is established, and thus the regulation of super-plasticity deformation and defect formation could be explained scientifically. According to the difficulties in the superplastic forming and diffusion bonding of aluminum alloy, we propose a new diffusion bonding method, and clarify how the parameters and mechanism about the boundary diffusion bonding and atom diffusion. Furthermore, we solve the key problems about superplastic forming and superplastic diffusion bonding, and provide the theory basis for the cavity grow and refrain, uniformity of wall thickness controlling, low productivity and aluminum diffusion bonding.

本项目以晶粒尺寸与相比例协同调控为基点，系统研究晶粒尺寸与相比例协同调控机制对超塑性能及其微观演变过程的影响规律，探索超细晶材料在高应变速率条件下的超塑性变形新理论，并从能量的角度解析超塑变形过程的诸多微观过程如晶界滑动、晶内滑移、扩散蠕变、空洞形核与长大、变形失稳等，建立超塑变形能量法解析理论，更为科学的解释超塑变形规律与缺陷形成规律；在此基础上，针对铝合金超塑成形/扩散连接较为困难的现状，提出高能率施压的扩散连接新方法，阐明高能量施压过程参数及其他外场参数协同加载对扩散连接界面结合及原子扩散能力的影响规律与机理。解决制约金属材料超塑成形及超塑成形扩散连接技术发展的关键科学问题，为调控或解决超塑成形及超塑成形/扩散连接过程的空洞演变与抑制、壁厚均匀性控制、生产效率低以及铝合金扩散连接等问题提供更为科学的理论依据。

本项目以晶粒尺寸与相比例协同调控为基点，系统研究了2205双相不锈钢、TC4钛合金和7B04铝合金的晶粒尺寸与相比例协同调控机制对超塑性能及其微观演变过程的影响规律；通过搅拌摩擦加工方法制备了超细晶材料，探索了超细晶的低温高速超塑性能；深入研究了7B04铝合金超塑变形过程中空洞形核、长大与演化规律，探索了脉冲电流对空洞的抑制作用。基于晶体塑性理论对TC4钛合金的超塑变形开展了数值模拟，建立了铝合金超塑变形空洞演变机理图和能量耗散模型，从能量的角度解释了超塑变形过程的诸多微观过程如晶界滑动、晶内滑移、扩散蠕变、空洞形核与长大、变形失稳等；设计并搭建了高能率施压超塑扩散连接试验平台，开展了铝合金的超塑扩散连接试验，阐明了脉冲强磁场和温度场耦合作用对扩散连接界面结合及原子扩散能力的影响规律与机理。从而解决了制约金属材料超塑成形及超塑成形扩散连接技术发展的关键科学问题，为创新超塑成形及超塑成形/扩散连接技术提供了强有力的理论支撑。