Preparation of Multilayered Ti-Al Alloys by Solid Reaction

The multilayered materials with different combinations of Ti, Al and Ti-Al intermetallics were prepared by heat treatment and hot pressing (HP) with elemental foils. The microstructures and phase formation of the obtained samples were detected by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), energy dispersive spectroscopy (EDS) and X-ray diffractometer (XRD). When the HP is applied under the melt point of aluminum, aluminum is the only diffusive element across the oxide films on the surface of the initial foils; however, some unusual TiAl3 particles are found in the multilayered structure due to the broken of oxide films; after hot pressing for 4 hours, all the aluminum was consumed; many voids exist at the centerline of TiAl3 layers, which are mainly caused by Kirkendall effect and the difference of molar volumes between reactants and products; before the aluminum is completely consumed, TiAl3 is the only product in the solid reaction under the melting temperature of aluminum; however, other Ti-Al intermetallics like Ti3Al and TiAl are formed in the updated temperature diffusion after aluminum is consumed.