Thermal oxidation behaviour of bulk titanium with nanocrystalline surface layer

The oxidation behaviour of a novel Ti with a nanocrystalline (NC) surface layer, made by surface mechanical attrition treatment (SMAT Ti), has been investigated in air at 500 similar to 700 degrees C. SMAT Ti can react with oxygen and form oxide particles even at 500 degrees C, while that of coarse-grained Ti (CG Ti) is about 600 degrees C. Ti shows a different colour at each temperature, which is attributed to the light interference phenomena. The SMAT Ti shows a thicker, denser oxide layer as compared with that of CG Ti. It originates from the numerous grain boundaries and dislocations on the SMAT Ti surface