Interactive effects of specimen size and current density on tribological behavior of electrically-assisted micro-forming in TC4 titanium alloy

In this paper, electrically-assisted (EA) micro-ring compression tests were carried out to investigate the tribological behavior. It was found that the lubricity of conductive greases was outstanding in the moderate current density range, in which the ablation and oxidation induced by current were almost suppressed. Moreover, the presence of current would reduce the frictional size effects, and this trend increased with the increase of current density. It was attributed to the affects of the joule heating effect induced by current. Finally, a new friction model was put forward to quantify the influence of specimen scale and current by introducing the scale factor and current density, which could effectively predict the friction coefficient and explain the mechanism of friction size effects.