Abstract
The influences of non-isothermal aging (the temperature range is 150–180 °C, and the heating rate is 5 and 20 °C/h alternately), single-peak aging (aging at 120 °C for 24 h, then water quenched was followed at room temperature), and two-stage aging (aging at 105 °C for 8 h first, then increasing aging temperature to 135 °C and keeping for 12 h, followed by water quenching at room temperature) on the corrosion resistance and microstructure of the 7N01 aluminum alloy under 3.5 wt.% NaCl were investigated using electric polarization curve test and exfoliation corrosion. After aging, the hardness of samples was measured by a Vickers micro-hardness tester, and the electrical conductivities were obtained using the eddy current method. The results show that the steady phase η and metastable phase η′ are precipitated in the grain boundary of 7N01 aluminum alloy after non-isothermal aging, and their distribution is discontinuous. The hardness of the alloy can reach 136.9 HV1 and the electrical conductivity can reach 35.8% IACS, which is close to the hardness of single-peak aging and the conductivity of two-stage aging, respectively. Compared with single-peak aging, the corrosion current density of non-isothermal aging is reduced by 15.5%, and that of two-stage aging is reduced by 28.9%.
Highlights
High-speed rail has gradually become the main mode of transportation in various countries
The electrical conductivity performance is often positively related to the corrosion resistance of the material
We initially concluded that the non-isothermal aging could attain the mechanical properties of single-peak aging and corrosion resistance of two-stage aging
Summary
High-speed rail has gradually become the main mode of transportation in various countries. Problems regarding the inconsistent temperatures between inner and surface of large size profiles during the rapid changes of the temperature and heat treatment result in an inhomogeneous microstructure and properties, but these can be solved. Xiao et al investigated the corrosion resistance properties of 7050 Al-alloy by non-isothermal aging [25]. To the authors0 knowledge, no work concerning the corrosion resistance properties of 7N01 aluminum alloy by non-isothermal aging has been reported. The purpose of this investigation was to study on the corrosion resistance properties of 7N01 aluminum alloy by non-isothermal aging
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