Effect of prefatigue deformation on the uniaxial tensile properties of a dilute Cu-Al alloy

Abstract

To examine the influence of prefatigue on the uniaxial tensile properties of a Cu-3at%Al alloy with a high stacking fault energy (SFE), the prefatigued tests are carried out at different total strain amplitudes ranging from 1.0 × 10−3 to 5.0 × 10−3 up to the same accumulated plastic strain of 31, and uniaxially tensile tests are subsequently conducted on these prefatigued alloy specimens. With increasing strain amplitude, the induced fatigue dislocation structures change from elongated veins and planar stacking faults to dislocation walls and cells. For the Cu-3at%Al alloy specimen prefatigued at an intermediate Δεt/2 of 2.3 × 10−3, the induced microstructure consists of loose cells, walls and few ill-developed persistent slip bands, which allows for an increase in dislocation storage rate but nearly does not affect dislocation annihilation rate during tensile deformation, thus exhibiting a higher strain hardening capability; therefore, the tensile strength can be improved nearly without loss of uniform elongation compared to the unfatigued specimen. In a word, an appropriate low-cycle prefatigue treatment can cause, to some extent, a strengthening effect on the static mechanical properties of high SFE metals, but such a strengthening effect is not as significant as the case for low SFE metals.