Grain and geometry size effects on plastic deformation in roll-to-plate micro/meso-imprinting process

Abstract

Roll-to-plate (R2P) imprinting process is an efficient technique to fabricate functional surface microstructures on a metallic substrate, which is widely used in the fields of microfluid, heat and mass transfer, and friction/drag reduction. However, the plastic deformation of microfeatures is significantly influenced by size effects. In this paper, the effects of grain and geometry size on the plastic deformation in R2P micro/meso-imprinting process were investigated by experiments and numerical simulations. According to the characteristics of the R2P micro/meso-imprinting process, a numerical model of R2P micro/meso-imprinting process was established. The experiments with pure copper were conducted through a self-developed R2P micro/meso-imprinting system. The size effects were studied via the evaluation of the formed height, rolling force and microhardness distribution. It is concluded that the rolling load reduces because of the decrease of flow stress caused by the weakening of grain boundary strengthening effect when the grain size increases. The wider groove and larger fillet could enhance the microforming ability of material and reduce the forming loads. The effect of groove width is more significant than that of the fillet. The microhardness distribution shows that the coarse-grained material has higher hardness than the fine-grained material in the central regions of the cross-section for the formed feature due to the penetration effect of deformation. However, the hardness in the central regions dwindles with the increase of the groove width and fillet. It is also found that the profile irregularity and surface roughness of the formed feature increase with the grain size and rolling depth. The results would provide a basis for further exploration in R2P micro/meso-imprinting process.