超细晶材料微成形尺度效应及热稳定性研究

针对传统金属材料在塑性微成形技术中存在成形性能差、尺寸精度低的问题，本项目提出采用超细晶（UFG）材料代替常规金属粗晶(CG)材料，利用实验和理论分析相结合的方法，研究毫米至微米多尺度范畴UFG材料的变形行为，分析外部尺寸、表层约束以及内部尺寸等对微塑性变形过程流动应力的相互影响，确定UFG材料微塑性变形机制，构建UFG材料晶界滑移主导的微塑性变形理论模型，揭示多尺度UFG材料微成形尺度效应机理。进一步研究UFG材料在塑性微成形过程的微观组织演变规律，建立UFG材料晶界扩散驱动力数学模型，揭示UFG材料的热稳定性机理，解决UFG材料在微小型腔填充、超细晶粒以及形状精度控制等若干相关问题，实现UFG材料微型换热器零件的高质量可控成形。项目的研究成果对于促进塑性微成形技术在微制造领域的实际应用具有重要意义，并为微型零件高质量可控成形提供理论依据。

In this proposal, ultrafine-grained (UFG) materials are chosen to overcome the limits of formability and dimensional accuracy of conventional coarse-grained (CG) materials. Micro plastic deformation behaviors in UFG materials will be investigated ranging from millimeter to micron scales using experimental and theoretical approaches.The discussions will be centered on the interplay of extrinsic size, surface layer restraint and intrinsic length on the flow stress during microforming. The micro deformation mechanism of UFG materials will be determined based on these findings. A theoretical model based on the grain-boundary slding dominated plasticity will be developed to explain the size effect mechanism in microfroming of UFG materials.In addition, the microstructural evolutions of UFG materials will be studied during microforming. The mathematical model of driving force for grain boundary diffusion will be constructed to predict the thermal stability of the UFG materials. Finally, the issues of filling quality for micro die cavity, ultrafine grains controlling and dimensional accuracy improvement shall be addressed and micro-heat exchangers will be fabricated with high quality using the UFG materials.The developments of this project are playing an important role in promoting the microforming for a protential application in micro-fabrication field and providing a basis theory for the controlled forming of microparts with high quality.