Effects of surface gradient nanostructuring on the fatigue behavior of the friction stir welded AlZnMgCu alloy

Surface gradient nanostructuring was performed on the friction stir welded joints of high strength AlZnMgCu alloy by means of surface mechanical rolling treatment (SMRT). Uniaxial symmetric tension-tension fatigue tests (R = 0.1) showed that two orders of magnitude extension in fatigue lifetime was achieved on the FSW joint of the AlZnMgCu alloy, exhibiting the transition of fatigue crack initiation mode from surface to interior. The enhanced fatigue mechanism was discussed based on the measured in-depth distribution hardness and compress residual stress, as well as the observed microstructure modifications. (C) 2019 Elsevier B.V. All rights reserved.