Advances in Synthesizing Methods of Ti-based Intermetallics from Elemental Powders

초록

Powder metallurgy has been successfully adopted in synthesizing intermetallic compounds based on Ti-Al and Ti-Si. Direct hot extrusion of elemental powder mixtures resulted in rods of about 2cm in diameter with the compositions based on Ti-46.6Al-1.4Mn-2Mo (all in at.%). Among the processing parameters, degassing scheme, heating rate, extrusion can and die design, extrusion temperature and extrusion ratio were found to be crucial to ensure the sound mechanical properties such as tensile properties and creep strength. Further improvement in the mechanical properties was obtained by modifying the chemical composition with C or Y, which were effective in refining the microstructure, thus enhancing the tensile strength at elevated temperature. Electro-pressure sintering was also evaluated as an alternative consolidation route for Ti5Si3-(Cu-Nb-C). Through a balanced control of the heating scheme, sintering temperature and pressure, near full density state of the two Ti-based intermetallic compounds was obtained, in which a high fracture toughness and absence of porosity, respectively, were realized.