Hydrogen induced softening and hardening for hot workability of (TiB + TiC)/Ti-6Al-4V composites

(TiB + TiC)/Ti-6Al-4V composites were in situ synthesized and hydrogenated by melt hydrogenation technology (melting alloys in gas mixture of hydrogen and argon). Microstructure observation indicated that reinforcements were homogenously distributed in unhydrogenated composites, with the increase of hydrogen content, the reinforcements tend to locate at prior β grain boundaries to form near network structure. Results of high temperature deformation showed that the hot workability of titanium matrix composites was determined by the microstructure of titanium matrix and distribution of reinforcements. There was a competition between hydrogen induced hardening and softening effect. When deformed at 850 °C, hydrogen induced promotion of β phase content and dynamic recrystallization reduced the peak stress and lead to softening effect, below 850 °C, hydrogen induced near network structure caused hardening effect because the load bearing capacity of network structure was better than the homogenously distributed reinforcements.