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

Abstract

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 μm 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 × 10 5 Ω•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.