| Up to now, a variety of synthesis techniques have been developed for producing bulk nanocrystalline materials. However, difficulties still exist in forming 'ideal' samples(i. e. free of porosity and contamination, large dimensions, etc.), that are obstacles for the investigations and applications of nc materials.A nanostructured surface layer was fabricated on a 316L stainless steel by using supersonic fine particles bombarding (SFPB) technique. The microstructure and mechanics property of the surface layer of sample was characterized by means of X-ray diffraction, transmission electron microscope ,scan electron microscope, microhardness testing machine andsurface roughness testing machine. In this work, a 316L stainless steel treated by USSP was selected to be studied. The microstructural evolution was characterized by means of different techniques, and the grain refinement and the deformation behaviors were analyzed. In addition, effect of surface nanocrystallization on the fatigue properties of 316L stainless steel induced by USSP was also researched.The results also indicate that the nano-structured layer on the surface has high resistance to the fatigue-crack initiation, and the interior coarse grain can retard the growth of fatigue cracks, both of which evidently improved the fatigue lives of the specimens. Residual compressive stress makes great contribution to the improvement of the fatigue properties of 316L stainless steel. With observations to atigue fracture and experiment study on X-ray residual stress which made by SEM, it is consided that surface residual stress caused by upersonic fine particles bombarding (SFPB) x had done very important effect to the atigue life's increasing.
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