Fabrication of Porous TiAl-Based Intermetallics through Solid-State Diffusion

초록

Since TiAl-based intermetallic compounds have a low density (3.8 g/cm3), high specific strength up to elevated temperature and high melting point, these alloys have been considered as light-weight high temperature materials. Actually, some practical applications of the TiAl-based intermetallics have been made in the field of transportation system including turbo charger rotor for automotive engine and low pressure turbine for aerospace engine. A proper incorporation of porous structure in the TiAl-based intermetallics could extend the application field of the intermetallics as not only light-weight structural materials but also functional materials having excellent thermal stability. In this study, a reactive sintering process was adopted to fabricate porous TiAl-based intermetallics. The reactive sintering process involved the mixing of elemental Ti and Al powders, extrusion of the mixtures and then sintering stage. During the sintering stage, diffusion and exothermic reaction (Ti + Al → TiAl) occurred between elemental powders in solid state. After sintering, porous TiAl-based intermetallics could be formed as the results of the exothermic reaction and Kirkendall porosity in solid-state diffusion. Also, various types of matrix microstructure and pore morphology could be developed in the reactive-sintered materials by controlling processing conditions. Detailed microstructural characteristics and mechanical properties of the porous TiAl-based intermetallics will be presented.