Atomistic simulation of adhesion and adhesive transfer at metal/metal-oxide interfaces

Adhesion and adhesive metal transfer in aluminum forming processes are often the cause of many process and product related problems. Consequently, an enormous amount effort has been invested in lubricant and tool surface coating development to provide the means for adhesion reduction or elimination. Unfortunately, the kinematics of the tooling/workpiece interface are often such that the interface becomes depleted of lubricant. If the natural oxide of the aluminum is fractured, then nascent aluminum, which is highly reactive, will bond to the tool surface in the absence of a lubricant film leading to the formation an aluminum wear layer or coating on the tool surface. Tool surface coatings consisting of various metallic or refractory materials are often employed to prevent adhesion. Unfortunately, these are selected primarily on an empirical basis since there is no quantitative methodology that would allow one to "tune" a tool surface to the material properties of the aluminum and the tribological aspects of a forming process. It is therefore the purpose of the present work to present a methodology based upon the density functional method for the calculation adhesion energies and prediction of adhesive metal transfer at selected metal-metal oxide interfaces. We specifically address adhesion between Al(100)MiO(100) and Al(100)/Fe(100) slabs. We also report the first calculation of slab-on-slab adhesive metal transfer between Al(111) and alpha-Al2O3(0001).