A Study on Microstructure Evolution of 7055 Aluminum Alloy Based Under Extreme Environment

Abstract

In order to fill the mechanism of microstructure evolution and corrosion resistance of 7055 aluminum alloy in extreme environment, the 7055 aluminum alloy Which was subjected to T6I4 heat treatment was selected as the research object. High speed machining experiments were performed at low temperature (-60°C) and high temperature (350°C). The dislocation density, grain size, TEM microstructure and corrosion resistance of the cutting layer of 7055 aluminum alloy were investigated at low temperature (-60°C) and high temperature (350°C). The experimental results show that the dislocation density at low temperature is higher than that at high temperature under the same cutting speed and feed rate, and the grain size at low temperature is higher than that at high temperature too. In the low temperature environment, the continuous of the grain boundary is enhanced with the cutting speed increases, and the precipitation phase in the crystal is reduced and the precipitation phase on the grain boundary is obviously increased. Under the high temperature environment, with the increasing cutting speed, the degree of fibrosis of the grains is weakened and the dynamic recrystallization is obviously enhanced. Microstructures show significant dynamic recrystallization after high temperature cutting. And when the feed rate is 0.05 mm, the microstructure of 7055 aluminum alloy exists part of the sub-crystal; The larger the feed amount, the finer and longer the fibrous grains of the metallographic structure of cutting layer metal of 7055 aluminum alloy. There is a lot of dislocations in the cutting layer of 7055 aluminum alloy in low temperature environment. The higher the cutting speed, the smaller the dislocation density. No dislocations were found in the microstructure of the 7055 aluminum alloy cutting layer in the high temperature environment,and, the higher the cutting speed is, the less the number of precipitated phases is, and the GP region and η ‘phase were transformed into η phase.