Improving creep properties of 7075 aluminum alloy by laser shock peening

Effects of laser shock peening (LSP) treatment on the creep properties and microstructural evolution of the surface of 7075 aluminum alloy were investigated in this work. The microstructures of the LSP-treated and untreated specimens before creep were characterized by transmission electron microscopy (TEM) and scanning electron microscope (SEM). Creep rupture was then investigated. After creep, electron backscatter diffraction (EBSD) was conducted to analyze the peaks of the misorientation angle for the as-machined and LSP-treated samples. SEM was performed to observe the fracture surface. Above results proved that LSP could enhance the steady-stage creep life by 97% at 350 MPa/200 degrees C, 307% at 350 MPa/200 degrees C, and 120% at 300 MPa/200 degrees C. The mechanism for the improved creep properties of 7075 aluminum alloy by LSP was analyzed by TEM observation. Moreover, the creep process and mechanism of the variation of their microstructures were discussed. LSP had a beneficial effect on the improvement of surface microstructure comprised of the increase of dislocation density and the refinement of dispersoids, which would hinder the dislocation movement, decrease the growth of tensile texture and cracks and lower the creep rate. So LSP can effectively enhance the creep resistance of 7075 aluminum at the elevated temperature and working stress.