The surface nano-treatment of 7075-T651 aluminum alloy was realized by surface mechanical rolling treatment (SMRT) method. Electron backscatter diffraction (EBSD) results show that a 500 μm thick gradient nano-layer is formed on the surface of SMRT sample, the thickness of the surface nano-crystal layer is about 50 μm and the average grain size is about 200 nm. The thickness of the subsurface deformation grain layer is about 450 μm, and the average grain size is about 2 µm. The base metal shows typical rolling grain characteristics, and the average grain size is about 5 µm. The tensile test results show that the tensile strength, yield strength and elongation of the original 7075-T651 aluminum alloy are 545 MPa, 506 MPa and 17.3% respectively. After SMRT, the tensile strength, yield strength and elongation are 620 MPa, 536 MPa and 13.4% respectively. The strength of the sample significantly improves, and the toughness does not significantly decrease. Gradient nanostructures are introduced into the surface layer of the material by SMRT. This special structure has excellent matching of strength and plasticity, which is the main reason for the improvement of mechanical properties.
7075 aluminum alloygradient nanostructuresurface mechanical rolling treatmentsurface nano-treatment
Tian F Q，Li N K，Cui J Z.Research and Development of Ultra High Strength Aluminum Alloys［J］.Light Alloy Fabrication Technology，2005，33（12）：1-9.
Bakhshi R，Farshidi M H，Sajjadi S A.Streng-thening of aluminium alloy 7005 through imposition of severe plastic deformation supplemented by different ageing treatments［J］.Transactions of Nonferrous Metals Society of China，2021，31（10）：2909-2921.
Huang H W，Wang Z B，Lu J，et al.Materialia Fatigue behaviors of AISI 316L stainless steel with a gradient nanostructured surface layer［J］.Acta Materialia，2015，87：150-160.
Liu X C，Zhang H W，Lu K.Formation of nano-laminated structure in nickel by means of surface mechanical grinding treatment［J］.Acta Materialia，2015， 96：24-36.
Xu W，Liu X C，Lu K.Strain-induced microstructure refinement in pure Al below 100 nm in size［J］.Acta Materialia，2018，152：138-147.
Long J Z，Pan Q S，Tao N R，et al.Abnormal grain coarsening in cyclically deformed gradient nanograined Cu［J］.Scripta Materialia，2018，145：99-103.
Zhang K，Wang Z B，Lu K.Enhanced fatigue property by suppressing surface cracking in a gradient nanostructured bearing steel［J］.Materials Research Letters，2017，5（4）：258-266.
Lu K.Making strong nanomaterials ductile with gradients［J］.Science，2014，345：1455-1456.