A surface gradient nanocrystalline structure (SGNS) was obtained by shot peening (SP) on the TA17 near α titanium alloy to improve its surface properties. The effect of shot peening time was investigated by characterizing the grain size of the surface nanocrystalline layer, the thickness of the severe plastic deformation (SPD) layer, the microstructure evolution of the SGNS and the hardness change. The experimental results show that the grains of TA17 titanium alloy can be refined to a nano-scale of about 22 to 26 nm when shot peened at 0.6 MPa pressure for 5 to 10 minutes. The thickness of the SPD layer increases from 55 to 88 μm with the SP duration from 5 to 10 minutes and tends to be saturated afterward. The SGNS is composed of a surface nanocrystalline layer and a transition layer. During the SP treatment, the coarse grains are first divided into small blocks by intersection of twins, then dislocation walls, dislocation tangles and dislocation bands lead to the formation of low-angle grain boundaries, which subdivide the subgrains into a finer scale until nanograins with a stable size are obtained. The topmost surface hardness can be improved significantly to twice the hardness of the matrix due to both grain refinement and work-hardening.

通过在TA17附近α钛合金上进行喷丸处理（SP）获得表面梯度纳米晶体结构（SGNS），以改善其表面性能。通过表征表面纳米晶层的晶粒尺寸，严重塑性变形（SPD）层的厚度，SGNS的微观结构演变和硬度变化，研究了喷丸硬化时间的影响。实验结果表明，当在0.6 MPa压力下喷丸处理5至10分钟时，TA17钛合金的晶粒可以细化为约22至26 nm的纳米级。SPD层的厚度从55增至88μm的SP持续时间为5至10分钟，此后趋于饱和。SGNS由表面纳米晶体层和过渡层组成。在SP处理期间，粗晶粒首先通过孪晶相交而被分成小块，然后位错壁，位错缠结和位错带导致低角度晶界的形成，这将亚晶粒细分为更细的尺度，直到纳米晶粒具有获得稳定的尺寸。由于晶粒细化和加工硬化，最高表面硬度可以显着提高到基体硬度的两倍。