Corrosion Behavior of Ultrafine Grained Pure Ti Processed by Equal Channel Angular Pressing

Titanium alloy has extensive applications in the field of chemical, biomedical and marine engineering due to high specific strength and excellent corrosion resistance. Ultrafine-grained (UFG) and nanocrystalline (NC) materials with unique properties processed by severe plastic deformation are widely studied in recent decades. In comparison with large number researches on mechanical behavior of UFG/NC materials, corrosion resistance is rarely studied and results indicated inconsistent, even within the same alloy system. In this work, ultrafine-grained pure Ti was fabricated by equal channel angular pressing (ECAP) with 2 similar to 4 passes. Grain size, crystallographic texture and grain boundary character distribution of samples were characterized by EBSD. At the same time, dynamic potential polarization and EIS methods were used to study corrosion resistance in simulated seawater. Results showed that grain size and basal texture strength of pure Ti decreased after 2 ECAP passes, but the fraction of low angle grain boundary (LAGB) increased drastically. With increasing of extrusion passes, grain size and the fraction of LAGB decreased for samples, meanwhile, basal texture strength increased at first and then decreased. Electrochemical experiments indicated that all UFG titanium have better corrosion resistance than coarse one. On the other hand, it was founded that corrosion resistance didn't increased monotonously with the development of ECAP passes, and 3 ECAP passes displayed optimum. This could be attributed to the interaction of grain size, basal texture and grain boundary character distribution, and basal texture strength occupied the domination.