Microstructure Evolution and Microhardness Analysis of Metastable Beta Titanium Alloy Ti-15V-3Cr-3Al-3Sn Consolidated Using Equal-Channel Angular Pressing from Machining Chips

摘要

Machining chips of Ti-15V-3Cr-3Al-3Sn metastable beta titanium alloy were consolidated using back pressure-assisted equal-channel angular pressing (BP-ECAP) using different processing conditions. Near fully dense specimens were obtained after multiple passes done at 500 degrees C with the aid of different back pressures. SEM and TEM observations show that ECAP resulted in a homogeneous formation of ultrafine equiaxed alpha grains (similar to 180 nm) in the beta matrix, due to the generation of an extensive amount of dislocations, vacancies and sub-grain boundaries during ECAP. Most of these alpha grains showed a random orientation with the beta matrix. In addition, the observed grain refinement, increase in dislocation density and age hardening caused by this process resulted in a significant microhardness enhancement in the obtained parts. The microhardness homogeneity was improved as the processing temperature and the number of ECAP passes were increased.