Atomistic investigation of interface adherence mechanism of structural indenter nanocoining single crystal aluminum

The utilization of nanoimprint technology has become widespread in various industries. Nanocoining, a new type of nanoimprinting technology, is essentially graphic copying. Ensuring the indenter's accuracy and the transfer's integrity is crucial. Structured tool (ST)-metal workpiece interface commonly exists in adherence phenomenon during the nanoimprint. To reduce the adherence of workpieces in ST, it is remarkable to illustrate the adhesion mechanism. The molecular dynamic simulation model for indenting aluminum with a diamond ST indenter was established, and the influence of critical process parameters on adhesion, including the indenter geometry, indenter temperature, and indenter speed, was investigated. The results demonstrate that various factors significantly influence adhesion, including the van der Waals force, surface energy, temperature, mechanical embedding, diffusion, and holding stage. The mechanism of adhesion can be composed of three parts: the mechanical embedding caused by the large range of cavity filling of the indenter, the slow thermal diffusion and thermal migration of aluminum atoms along the indenter and the combined effect of thermal-tensile stress in the demolding process. The intensity of adhesion is affected by several factors, namely the degree of plastic deformation during loading and unloading, atomic thermal migration caused by system temperature, and the magnitude of tensile stress during the demolding stage. The geometry of the indenter exerts the most significant influence on the van der Waals force, surface energy, imprinting force, and unloading force. Additionally, the omission of the holding stage during processing contributes to a reduction in adhesion. This study provides atomic-level insights into the adhesive properties of metallic materials in the nanocoining process.