THE ANALYSIS OF THE MICROSTRUCTURE OF FOUR FCC METALS AFTER FRICTION IN LUBRICANT CONDITIONS

There are still many unresolved and outstanding issues associated with the effect of stacking fault energy (SFE) on deformation and fracture during severe plastic deformation (SPD). Since deformation structure of surface layers depends strongly on the SFE, it is natural to believe that SFE should play an important role on plastic deformation of fcc metals during friction. All friction tests were conducted under lubricant conditions using pin-on-disk rig. Pure fcc metals, Ag, Cu, Ni, and Al with different SFE (166, 125, 45, and 16 mJm^-2 for Al, Ni, Cu and Ag, respectively) were chosen as the materials for pins. Friction surfaces were carefully examined with a field emission scanning electron microscope (FE-SEM, Helios 460 F1Lite FEI). The cross sectional TEM lamellae were prepared from the multi-layered plate (pin) using a focused ion beam (FIB) (Helios 460 F1 Lite, FEI). Cross-sections were made along and perpendicular to the direction of friction. TEM analysis was performed using analytical high resolution scanning transmission electron microscope (STEM Techai F20 G2). In this work, friction and TEM investigations showing that, by increasing the SFE the grain size of surface layers is increased leading finally to dynamic recrystallization and to decreasing the friction and wear parameters. Dislocation structure and grain refinement are analyzed. The interaction between the microstructure and friction during lubricant conditions is discussed.