塑性加工方式与晶粒细化机理研究

正应变和切应变分别主导的加工过程在实践中表现出晶粒细化能力的显著差异。已有的晶粒细化模型分别从微观位错机制和宏观塑性特征两个层面进行描述，没能将两个层面有机关联起来；剪切变形在经典塑性理论中，被人为地从非同轴过程“转变”成同轴过程，在微观上产生实际中不存在的“附加”晶粒转动，妨碍正确认识组织演变机理。.本申请拟建立非同轴剪切变形过程塑性理论模型，排除经典塑性理论中将非同轴问题“转变”成同轴问题带来的上述困扰，对等地认识正应变和切应变的塑性力学本质；将两种变形方式不同的本质特征与材料的微观变形和组织演变关联起来，探索两种变形方式的组织细化过程和细化能力，阐明正应变、切应变作用下各自的组织细化动力学过程和机理，建立具有正应变、切应变特征的组织细化模型。为揭示塑性变形驱动的材料组织细化物理本质和规律、设计和开发具有强组织细化能力的新加工方法、推动超细晶纳米晶材料的研究和应用提供模型和实验数据。

The modes of plastic working, dominated by normal strain and shear strain respectively, shows significant difference in grain refinement capability in practice. The existing grain refinement models describe the micro dislocation mechanism and the macro plastic deformation features respectively, and fail to associate the macro deformation modes with the micro dislocation mechanism; the shear deformation is artificially “transformed” from non-coaxial process to coaxial process in the classical plastic theory, which causes obstacles probing the role of the macro deformation modes on the microstructure evolution mechanism. .This proposal intends to build a plastic model based on the non-coaxial characteristics of shear deformation, overcome the potential obstacles brought by the classical theory of "transforming" the non-coaxial problem into the coaxial problem, and equally understand the plastic mechanical nature of normal strain and shear strain; associate the different characteristics of the two deformation modes with the micro deformation and microstructure evolution of materials, and explore structure refinement process and the capability of the two deformation modes respectively, elucidate the dynamic process and mechanism of microstructure refinement under the action of normal strain and shear strain respectively, and establish the model of microstructure refinement with the characteristics of normal strain and shear strain. .These works will be helpful to the understanding of the physical nature and laws of microstructure refinement driven by plastic deformation, designing and development of new processing methods with high capability of microstructure refinement, and promoting the research and application of ultrafine grained and nanocrystalline materials.