In this study, a commercially pure titanium (CP Ti) sheet was produced by the ARB process. Then, the mechanical properties of monolithic and nanocomposites specimens manufactured using 0.1, 0.3, and 0.5 wt% TiO2 nanoparticles as the reinforcement were investigated at different ARB cycles. The results showed improvement in the mechanical properties of specimens with the addition of TiO2 nanoparticles, as their yield strength and ultimate tensile strength were increased by increasing the TiO2 nanoparticles percent. In this regard, the ultimate tensile strength of the monolithic specimen reached to 810 MPa, while it was 980 MPa, 1040 MPa, and 1085 MPa after applying 8 ARB cycles for 0.1 wt%, 0.3 wt% and 0.5 wt% nanocomposite specimens, respectively. However, the ultimate tensile strength of the as-received CP Ti sheet was 285 MPa. Moreover, the yield strength and the ultimate tensile strength were increased by increasing the number of ARB cycles and the total elongation; on the other hand, in the monolithic and nanocomposite specimens, it was decreased by increasing the number of ARB cycles. Grain refinements due to severe strain, work hardening and TiO2 nanoparticles reinforcements were the main causes accounting for the improved mechanical properties. Recovery and dynamic recrystallization were two phenomena observed via TEM studies in the ARB process, leading to the development of equiaxed grains in the final ARB cycles. By adding TiO2 nanoparticles, mechanical properties and work hardening coefficient were found to be increased, as compared to those of the monolithic samples. TiO2 nanoparticles, after being distributed in titanium matrix through the ARB process, caused pin dislocations. As clearly shown in TEM images, dislocation tangles around TiO2 nanoparticles acted as the main mechanism improving the work hardening coefficient.
