An Experimental Investigation on the Fabrication of Micro/Meso Surface Features by Metallic Roll-to-Plate Imprinting Process

Abstract

Metallic components with large-area functional surface micro/mesostructures have been increasingly utilized in various industrial fields, such as friction/wear reduction, viscous drag reduction, and energy efficiency enhancement. Roll-to-plate (R2P) imprinting process is an efficient and economical method in fabricating micro/mesofeatures on the large-area surface of the metal parts. However, process design methods based on scale law cannot be directly used due to size effects. Its formability is greatly influenced by tool feature size and material grain size. In this study, a lab-scale R2P imprinting system was developed to fabricate the microsructures on the surface of metallic materials. The specimens of pure aluminum and pure copper with various size grains were prepared. Rigid die with geometric dimensions was fabricated and series of experiments were conducted. The microfeature height of the imprinted workpiece was measured to evaluate the effects of tool feature dimensions (width, spacing, and fillet) and metal grain sizes. It is found that the groove width and fillet had more significant effect on the microfeature formation among the die cavity geometric parameters. Wider groove could enhance the microforming ability and large fillet could improve the flowing ability. From the viewpoint of polycrystalline material, grain structures significantly affected the microfeature formation. When the grain size was smaller than the groove width, the material flowed more easily into the die cavity with increasing of the grain size because of the decrease of grain boundary strengthening effect.