Effects of electropulsing frequency on mechanical properties, corrosion behavior and microstructure of a creep-aged 7050 aluminum alloy

Abstract

In the experiment, the effects of electropulsing frequency (150 Hz, 300 Hz, 450 Hz, 600 Hz) on the creep age formability, mechanical properties and corrosion behavior of 7050 aluminum alloy were studied. The results show that the creep age formability of the alloy is improved as the electropulsing frequency increases from 150 Hz to 600 Hz. The tensile strength and yield strength of the 600 Hz sample are 627 MPa and 590 MPa, which correspondingly increased by 5.2% and 6.1% compared with the 150 Hz sample. In addition, the maximum corrosion depth of the 600 Hz sample is 25.9 μm while that of the 150 Hz sample is 61.9 μm. The application of higher frequency electropulsing promotes the dislocation movement, so the dislocation density decreases and the creep strain is larger. The electropulsing accelerates the precipitation by enhancing the movement of vacancy and solute atoms and the depletion of vacancy inhibits the growth of precipitates. Hence, the higher frequency electropulsing leads to finer and denser intragranular precipitates, which contributes to the optimized mechanical properties. The electropulsing frequency of 600 Hz results in the discontinuous distribution of grain boundary precipitates and the reduction in the width of PFZ, which are beneficial to improve the corrosion resistance of the alloy.