Effect of annealing treatment on the microstructure evolution and mechanical properties of commercial purity titanium after processing by equal channel angular pressing

In this study the influence of annealing temperature on the microstructural evolution and microhardness of of ECAP-ed CP Ti investigated. It was revealed that after processing by 10 passes ECAP the initial coarse-grained CP-Ti with average grain size of 20 μm was refined to ultrafine grain/nano structure with a mean size of ~200 nm. A good thermal stability of the UFG structure was found below 400 °C, and thereafter recrystallization and grain growth occurred with increasing annealing temperature. The microhardness of ECAP-ed samples showed a sudden drop after annealing at 400 °C, whereas it decreased slightly up to 300 °C. These findings are analyzed in the context of the changes in the microstructural characteristics induced by annealing treatment.