Effect of titanium nitride nanoparticles on grain size stabilization and consolidation of cryomilled titanium

In this work, titanium nitride (TiN) nanoparticles (∼20 nm) were introduced during cryomilling of commercially pure titanium (CP Ti). Consolidation of cryomilled powders was performed using spark plasma sintering (SPS). Samples were analyzed and tested alongside cryomilled, SPS CP Ti not containing TiN nanoparticles. After cryomilling powders containing TiN nanoparticles and powders not containing TiN had a minimum grain size of ∼20 nm. Microstructure analysis after thermal processing of both samples revealed that grain size retention occurred due to the presence of TiN nanoparticles in CP Ti microstructure. In consolidated samples containing 5 vol% TiN nanoparticles, the minimum average grain size was retained to ∼250 nm, while in samples containing 0 vol% TiN nanoparticles, the minimum average grain size obtained was ∼750 nm. Microhardness testing showed an increased hardness of samples containing TiN nanoparticles due to the retention of smaller grains and the presence of TiN nanoparticles.