Corrosion mechanism and machinability of 7075-T6 aluminum alloy in high-speed cutting: With and without cryogenic treatment

This work aims to explore the effect of cutting parameters on the cutting force, surface quality, and corrosion resistance of 7075-T6 aluminum alloy after and without cryogenic treatment. Cryogenically treated (T6-C) and noncryogenically treated (T6) 7075-T6 aluminum alloy samples are experimentally cut and electrochemically corroded in a 3.5% NaCl solution. SEM, EDS, and electrochemical analysis are carried out to examine how cutting parameters affect the cutting force, surface quality, and corrosion resistance of cryogenically treated 7075-T6 aluminum alloy. The results show that after cryogenic treatment, under different cutting speeds, the cutting force is up to 39.8% smaller than without cryogenic treatment; under different cutting depths and feed rates, the cutting force is up to 136% and 21.54% smaller, respectively. Cryogenic treatment dramatically reduces the cutting force in the cutting process. As cutting speed increases, machined surface quality becomes better; fewer corrosion products and cracks are induced. When the cutting depth is 1.5 mm, there are fewer plows and micro-cracks on the machined surface than under other parameters, but cutting depth does not affect corrosion morphology significantly. The size of corrosion products is up to 55 mu m smaller. The electrochemical analysis finds that at the cutting speed of 1500 m/min, after cryogenic treatment, the current density is 59.4% smaller than without cryogenic treatment; polarization resistance is 1.68 x 10(5)omega center dot cm(2) larger. At the cutting depth of 1.5 mm, after cryogenic treatment, the current density is 66.16% smaller; self-corrosion potential shifts 0.19 V toward the positive pole. At the feed rate of 0.06 mm/z, after cryogenic treatment, self-corrosion potential shifts 0.18 V toward the positive pole; polarization resistance is 10.7% larger. These parameters correspond to the best corrosion resistance.