Research on Thermally and Electrically Assisted Tribological Behavior and Microstructural Evolution of 7075 Aluminum Alloy

Electrically assisted forming is an up-and-coming forming method. Thermally and electrically assisted friction and wear tests were conducted on 7075 aluminum alloy sheets using a self-developed thermal and electrical assisted tribometer to investigate friction behavior and post-wear microstructural evolution. The microstructure and composition of the 7075 aluminum alloy after electrically assisted friction tests were analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results indicate that after pulsed current application, the surface temperature of the sheet increases, and the friction coefficient between the sheet and the tool steel first decreases and then increases, reaching its minimum value at 12 A/mm2, at which the sheet attains optimal forming conditions. Pulsed current promotes the formation of surface compounds on the aluminum alloy, with grain size initially refining and subsequently coarsening, showing a positive correlation with grain boundary density. A comparative analysis with thermal forming processes reveals that as the current density increases, athermal effects begin to dominate the process. Under electrically assisted conditions, grain refinement is more pronounced than in thermally assisted processes, accompanied by the precipitation of MgZn2 strengthening phases (η'-metastable phases), which collectively enhance resistance to plastic deformation and improve wear resistance. However, at high current densities, the influence of athermal effects on microstructural evolution is significantly lower than that of thermal effects.