Study of the flow behavior and defect formation in forming of axisymmetrically flanged and multi-scaled parts

In microforming, the quality of microparts is one of the most critical issues. Folding caused by the abnormal material flow is one of the most common flow-induced defects in macroforming process. The identified formation mechanism of flow-induced defects in macro-forming process could be affected by the so-called size effects when the part dimension is scaled down to micro scale. Therefore, it is necessary to investigate the influence of size effects on the material plastic flow and deformation behavior in multiscaled deformation scenarios. To explore the formation mechanism of flow-induced defects, FE simulation is used to simulate the forming process. On the other hand, the multi-scaled forming was designed. To study the relationship of the flow-induced defect and sizes effects, forming of the axisymmetric parts with flanged features and different scales was conducted. The microstructure and plastic flow behavior of the deformed parts are also revealed. Based on the experimental and FEM simulation results, the formation of folding defects is mainly affected by the geometries and the sizes of the deformed flanged parts instead of grain sizes. In the cases by using material with coarse grains, the folding defect can be significantly reduced.