Microstructural and mechanical properties of α-titanium sintered material via thermal decomposition of additive chromium oxide particles

The pre-mixed pure Ti and Cr2O3 powder was consolidated by spark plasma sintering (SPS) and hot extrusion to fabricate alpha-titanium (Ti) materials with oxygen (O) and chromium (Cr) elements by powder metallurgy (PM) process. The Cr2O3 particles were completely decomposed during SPS, and then O and Cr atoms were dissolved in alpha-Ti matrix. Oxygen atoms were remarkably improved the mechanical strength of PM Ti-O-Cr alloys by their solid solution hardening effect. The Cr solution and Ti4Cr precipitates had important roles to obstruct the grains coarsening behavior by the solute drag and Zener pinning effects, respectively. The solid solution strengthening effect by Cr atoms, however, was very limited due to a small Cr solubility of about 0.35 at% in alpha-Ti phase of Ti-O-Cr alloys. Since Ti4Cr precipitates with 10-20 mu m diameters were not so fine, they hardly contributed to the precipitation hardening of Ti-O-Cr alloys.