The Research On Ultra-precision Chemical Milling Process Of Aluminum Alloy

In this paper,the effects of main components and process parameters of two kinds of aluminum alloy（AS,AF）ultra-precision chemical milling and cutting baths on disk substrate on milling speed,surface roughness and machining accuracy are studied.The bath formulation and process parameters suitable for ultra-precision milling were screened by single factor experiments.The effect of aluminum alloy flake milling on the surface was studied.The experimental results show that the formula of high precision milling technology for aluminum alloy is: Na OH 110¹40 g/L,Na₂ S 20²5 g/L,TEA 30⁴0 g/L,RH101 0.5¹.0 g/L,mechanical stirring.The milling temperature for AS aluminum alloy is 50⁵5 °C,the maximum loading is 30 cm2/L,the milling speed is 7.86 μm/min,and Ra=0.210 μm.Suitable for AF aluminum alloy,the milling temperature is 50⁶5 °C,the maximum loading is 40 cm2/L,the milling speed is 5.52 μm/min,Ra=0.804 μm.By controlling the processing temperature and loading,the milling process can be Meet the accuracy requirements of 0.03 ± 0.003 mm.By performing EDS analysis on the surface of the alloy after the reaction,the surface of the AF aluminum alloy after chemical milling will have a Cr-rich phase distributed on the surface of the aluminum alloy in an irregular granular form,and a small amount of granular surface on the surface of the AS aluminum alloy with a higher Fe content.The substance is mainly rich in Fe phase.For the 2198-T8 new high-performance aluminum-lithium alloy commonly used in aircraft,through single-factor experiment,the milling process of aluminum-lithium alloy is screened by milling speed,surface roughness and processing precision,and the influence on the processing performance of the milling process is studied..According to the characteristics of the milling process and the action mechanism of the additive,the additives suitable for the processing of aluminum-lithium alloy milling are selected.The relationship between the processing performance of aluminum-lithium alloy milling and the Al³⁺ content in the bath was analyzed,and the adjustment method of the milling bath was determined.The distribution state of the alloying elements on the surface after milling is analyzed by EDS.The experimental screening process suitable for 2198-T8 aluminum-lithium alloy is: Na OH 160¹80 g/L,Na₂ S 15²0 g/L,TEA 35⁴5 g/L,RX 0.5¹.0 g/L,milling temperature It is 80⁹5 °C,the maximum loading is 22 cm2/L,Ra=1.22 μm,the milling speed is 30⁷1 μm/min,and the machining accuracy is 0.3±0.05 mm.EDS analysis of the surface after milling shows that the alloying elements Cu and Fe are enriched on the surface during the milling process,and the surface quality after milling is affected by the electrochemical process.In the 2198-T8 milling bath,when the Al³⁺ concentration is lower than 87.23g/L,the milling speed can be stabilized by adding Na OH;when the Al³⁺ concentration is higher than 87.23 g/L,the milling is improved.The processing temperature is maintained at the milling speed so that the solution can continue to be used until the Al³⁺ concentration reaches 90 g/L.At this time,the temperature increase will not be slow.When the concentration of Al³⁺ in the bath reaches 75 g/L,the addition of Na₂ S 11.23 g/L can reduce the surface roughness from 1.22 μm to 0.74 μm,and it is not necessary to continue to replenish Na₂ S during the bath life.No additional TEA and RX are required for the entire bath life.