In this research, a method employing micro-extrusion was designed to produce the micro-scaled barrel-shaped parts with complex geometrical features to study the feasibility of the proposed microforming method and its grain size effect on the formability of the complicated internal features in terms of deformation behavior, material evolution, accuracy of dimensions and final components quality. The results reveal that the deformation behavior is highly affected by grain size and becomes unpredictable with increased grain size. In addition, assembly parameters including feature dimension, tolerance and coaxiality also vary with grain size, and the variation of grain size needs to be accommodated by different assembly types, viz., clearance fit or transition fit. From the microstructural evolution aspect, it was identified there were two dead zones and four shear bands, and the formation of these deformation zones was barely affected by the variation in grain size. Though bulges, cracks, and fracture induced voids were observed on the surface of the final components, tailoring the microstructure of the working material with finer grains could significantly avoid these defects. This study advances the understanding of forming microparts by extrusion processes and provides guidance for microforming of similar microparts.

在本研究中，设计了一种采用微挤压的方法来生产具有复杂几何特征的微型桶形零件，以研究所提出的微成形方法的可行性及其晶粒尺寸对复杂内部特征的可成形性的影响。变形行为、材料演变、尺寸精度和最终部件质量。结果表明，变形行为受晶粒尺寸的影响很大，并且随着晶粒尺寸的增加而变得不可预测。此外，包括特征尺寸、公差和同轴度在内的装配参数也随着晶粒尺寸的变化而变化，并且需要通过不同的装配类型（即间隙配合或过渡配合）来适应晶粒尺寸的变化。从微观结构演化来看，发现存在两个死区和四个剪切带，并且这些变形区的形成几乎不受晶粒尺寸变化的影响。尽管在最终部件的表面上观察到凸起、裂纹和断裂引起的空洞，但通过更细晶粒定制工作材料的微观结构可以显着避免这些缺陷。这项研究增进了对通过挤压工艺成型微型零件的理解，并为类似微型零件的微成型提供了指导。