Processing gamma-based TiAl sheet materials by cyclic cold roll bonding and annealing of elemental titanium and aluminum foils

Previous work by the authors investigated cold roll bonding followed by annealing as a simplistic method for processing Ti/TiAl3 multi-layered composites from elemental titanium and aluminum foils. In this study, the Ti/TiAl3 multi-layered composites were subjected to further processing at higher temperatures and increased cyclic cold rolling to promote the formation of gamma-based titanium aluminide (γ-TiAl). The resulting γ-TiAl phase was characterized using light microscopy equipped with digital image analysis, scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Vickers microhardness testing. The thermodynamics and kinetics of the diffusion reaction were investigated using differential scanning calorimetry (DSC) and enthalpy (H), entropy (S), and capacity (C) thermodynamic calculations. The physical, chemical, mechanical, and microstructure changes that accompanied the phase transformation to γ-TiAl was discussed.