| Nanocrystalline materials have the unique mechanical, physical and chemical properties, which are different from the routine material owing to the particularity of structure. Most of failures of material begin from their surface, obviously a nanostructured layer can enhance the whole properties and behavior greatly by means of surface nanocrystallization. So surface nanocrystallization has been regarded as one of the most promising technologies.The surface nanocrystallization of commercial pure titanium and Ti6A14V was achieved by means of high-energy shot peening(HSP). X-Ray diffraction (XRD), the scanning electron microscope (SEM) and the transmission electron microscope (TEM) were used to study. It was demonstrated that the grain size of surface was about 20~40nm.The surface of commercially pure titanium and Ti6A14V after surface crystallization by HSP was observed and studied, and the results showed that there were impairments on the different degrees in the suface layer: The big flake-offs appeared when commercially pure titanium was peened for 15 minites, the micro-cracks appeared when peened for 30 minites, the bigger ones did when peened for 90 minites; The flake-offs appeared when Ti6A14V was peened for 15 minites, the micro-cracks appeared when peened for 90 minites,and there were no big ones; All of these micro-cracks did not cross over the layer of surface nanocrystallization.The surface roughness of commercially pure titanium and Ti6A14V after surface nanocrystallization was measured by the apparatus of surface topography, and the results showed that the surface roughness of commercially pure titanium increases after HSP, and it reacheed the maximum when peened for 10 minites and drived to stabilization stage when peened for 60 minites; the surface roughness of Ti6A14V increased after HSP, and it reached the maximum when peened for 30 minites and reached the minimum when peened for 60 minites, and drived to stabilization stage.
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