Microstructure And Properties Of Surface Nanocrystallized CP-Ti Processed By SMAT

Surface nanocrystallization technique can be used to synthesize nanostructured surface layer on the engineering metallic materials through severe plastic deformation, therefore the surface (and whole) properties and behaviors of the materials can be enhanced significantly. The surface nanocrystallization is regarded as one of new important surface modification methods which have prospective applied future. Therefore, surface nanocrystallization technique and related basic research is a hot-spot topic in material science.The commercial pure titanium (CP-Ti) was selected to be treated by surface mechanical attrition treatment(SMAT) technique in this work, and a nanostructured surface layer was obtained. Then, vacuum annealing was carried out for the SMAT sample at different temperatures. The microstructural evolution of nanocrystal structures and the properties of the SMAT sample were analyzed by means of the X-ray diffraction(XRD), transmission electron microscope(TEM), optical microscope(OM) and scanning electron microscope(SEM). The conclusions can be summarized as follows: Performing surface nanocrystallization of CP-Ti by SMAT technique, of which the grain size is 17.35nm; The surface hardness of CP-Ti is HV218. The nanostructured surface layer is achieved by twinning cooperation with slip. After SMAT progress, the microhardness enhancement of CP-Ti surface layer is the action result of fine-crystal, high density of dislocation and twins. After SMAT progress, the self-corrosion potential of CP-Ti in 3.5% NaCl solution has got some increase and the corrosion resistance is improved, while the corrosion resistance in 0.5mol/L H₂SO₄ solution is worsened; the corrosion resistance of CP-Ti treated with SMAT (15 minutes) and low-temperature anneal(annealing temperature below 350℃) is strengthened in 3.5% NaCl solution and 0.5mol/L H₂SO₄. Microstructure and Properities of nanostructured surface have good stabilization when annealing temperature is below 350℃.