Abstract
A high–voltage transmission electron microscope (TEM) has been used to investigate the mechanism of friction. A single–pass sliding in air, the moat fundamental test system in tribology, was conducted using a copper single crystal. It was found that the greater the degree of deformation, the larger the friction coefficient; friction is thus primarily a resistance of deformation during sliding. A further TEM study on the cross-sections of a friction track clarified the microscopic constitution of the work-hardened layer to contain a texture, a distorted region, a compressed zone and an undisturbed matrix.