Uniaxial Ratcheting Behavior of 7075 Aluminum Alloy

The ratcheting behavior of 7075 aluminum alloy in the T651 heat treatment state was studied by uniaxial tension-compression cyclic tests under different mean stresses and stress amplitudes. The microstructure of the aluminum alloy before and after tests was observed and analyzed. The results show that the 7075 aluminum alloy presented apparent ratcheting strain accumulation characteristics under different cyclic loads. At the beginning of the cycle, the plastic deformation was obvious and the ratcheting strain rate was high, due to the increase of dislocation density, strengthening of dislocation elastic stress field and appearance of a large amount of dislocation tangle in the aluminum alloy. With the increase of the number of cycles, the plastic deformation accumulation decreased obviously and the ratcheting strain rate increased slowly in a near linear trend. The ratcheting strain accumulation increased with the increase of stress amplitude or mean stress.