| A nanocrystallized microstructure was generated on the surface of 36CrNiMo4 by sever plastic deformation induced by ultrasonic processing. The grain refinement mechanism of surface nanocrystallization was analyzed by optical microscope (OM), transmission electron microscopy (TEM), X-ray diffractometer (XRD), microhardness, and roughness test. The results show that the average grain size on the surface layer is about 25 nm after the surface ultrasonic processing, and the nanocrystallines present an equiaxed shape. The grain size increases gradually from the surface to the inside with the weakening of ultrasonic processing. The surface roughness is decreased and the hardness is increased significantly. |
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