Hot Formability of Particle reinforced Ti - Alloys

Titanium alloys exhibit mechanical and physical properties that fit structural applications demanding light-weight, corrosion resistance and biocompatibility. Ceramic reinforcements can further improve some of these mechanical properties, such as wear resistance, specific stiffness and specific strength. In comparison to continuous reinforced titanium alloys, the particle reinforced alloys (PRTi) do not show anisotropies and are cheaper in production. Furthermore, a potential production route by hot working is more feasible for PRTi. The present work studies the mechanisms of hot deformation of the PRTi produced insitu by powder metallurgy of Ti-6Al-4V-powders with additions of a certain amount of B and C. Thus, TiB precipitates form as ceramic reinforcements in the Ti-6Al-4V-0.1C matrix. Hot compression tests on this PRTi and on conventional Ti64 were carried out at temperatures between 850°C and 1100°C, and at strain rates of 0.001s to 10s. The processing maps, which represent the efficiency of power dissipation as functions of strain rate and temperature at a chosen true strain value, were derived from flow curves produced by compression tests with the Gleeble®1500 device. These processing and instability maps are correlated to microstructural changes and compared with those of TiC-particle reinforced Ti662 produced by Cold-Hot Isostatic Pressing (CHIP). The mechanisms of energy dissipation by hot deformation are discussed.