Optimization of Chemical Milling Process of 2195 Al-Li Alloy

2195 Al-Li alloy was machined by chemical milling in two chemical milling solutions (NaOH+Al³⁺+Na₂S+triethanolamine and NaOH+Al³⁺+Na₂S₂O₄5H₂O). The relatively suitable chemical milling solution was determined and its composition was optimized by orthogonal test. The tested alloy was machined by chemical milling in the optimal chemical milling solution. The effects of chemical milling temperature on the chemical milling rate and surface roughness were studied and the surface morphology and tensile property before and after chemical milling were compared. The results show that the chemical milling solution made up of NaOH, Al³⁺, Na₂S and triethanolamine had a better chemical milling effect on the tested alloy than that of NaOH, Al³⁺ and Na₂S₂O₄·5H₂O, and its optimal composition was listed as follows:210 g·L^-1 NaOH, 40 g·L^-1 Na₂S, 30 g·L^-1 Al³⁺ and 50 mL·L^-1 triethanolamine. In the optimal chemical milling solution, with rising chemical milling temperature, the chemical milling rate of the tested alloy increased whereas the etching ratio increased and then decreased. The chemical milling temperature was relatively suitable at 85-95℃. The surface of the tested alloy had no defects such as cracks and corrosion holes after chemical milling in the optimal chemical milling solution at 85℃ to the depth around 4.3 mm, and the tensile property after chemical milling at 85-95℃ to the depth around 3.0 mm was similar to that before chemical milling.