Influence of pre-stretching and aging processes on comprehensive performance of aluminum alloy

摘要

The influence of pre-stretching and aging treatment on the mechanical properties and corrosion behavior of 7050 alloy were studied by tensile testing, potentiodynamic polarization, and intergranular corrosion (IGC) testing associated with optical microscopy (OM), scanning electron microscopy, and transmission electron microscopy. The results exhibit both strength and elongation of T6 are higher than T74. The strength of retrogression and re-aging (RRA) samples are equal to or even in excess of T6 sample, especially, the strength of RRA-60 sample increased by 5.7% at the sacrifice of its elongation. Both yield strength of T651 and RRA51-60 samples with 4% pre-stretching are enhanced while their elongation decreased too much. The fracture feature of T6 and T651 samples are majorly intergranular fracture, while the fracture mode of RRA samples are mainly transgranular fracture. The corrosion resistance of T74 could be significantly improved through IGC tests and electrochemical polarization tests. Also, RRA treatment leads to the most remarkable improvement. The reason is that the grain boundary precipitated phases become coarser, also the precipitation free zones of RRA-60 and T74 are wider than T6 aged sample. Furthermore, the corrosion resistance of pre-stretched samples are worse than those without pre-stretching.