Mechanisms Governing Cyclic Deformation and Damage During Elevated Temperature Fatigue of High Strength Aluminum Alloy 7055

Abstract

Abstract The cyclic stress response, deformation and damage characteristics of aluminum alloy 7055 was studied at ambient and an elevated temperature. The specimens were cyclically deformed using tension-compression loading under total strain-amplitude control. The alloy showed evidence of softening to failure at the two test temperatures. The degree of cyclic softening increased with an increase in test temperature. The presence of deformable matrix strengthening precipitates and particles in the T7751 microstructure results in a local decrease in resistance to the motion of ’mobile dislocations, causing a progressive loss of strengthening contributions to hardening. At the elevated temperature, localized oxidation and embrittlement at the grain boundaries are promoted by the applied cyclic stress and play an important role in accelerating crack initiation and subsequent crack propagation. The damage response of the alloy is discussed in terms of competing influences of intrinsic microstructural effects, matrix deformation characteristics arising from a combination of mechanical and microstructural contributions, cyclic plastic strain amplitude and concomitant response stress, and test temperature.