Processing and mechanical behavior of laminated titanium-titanium tri-aluminide (Ti-Al3Ti) composites

Ti-Al3Ti laminated composites have been fabricated through reactive sintering in vacuum using Ti and Al foils with different initial thickness. The aluminum layer was completely consumed resulting in microstructures of well-bonded metal-intermetallic layered composites with Ti residual metal layers alternating with the aluminide intermetallic layers. The MIL composites exhibit a very high degree of microstructural design and control. Microstructure characterization by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and energy dispersive spectroscopy (EDX) has shown that Al3Ti is the only titanium aluminide phase due to the thermodynamics and phase selection of the reaction between Ti and Al through mass diffusion in the presence of liquid Al. The mechanical properties and fracture behavior of the fabricated laminated composites were examined through three-point bending test. The results indicated that the composites exhibited anisotropic features. When the load perpendicular to the laminates was applied, they displayed a step-like or saw-tooth load-displacement response and superior flexural strength as well as fracture toughness, which is also dependent on the number and thickness of individual layers. A non-catastropic fracture was observed in the laminated composites due to the deflection of cracks along the Ti/Al3Ti interface. The Ti layer failed by cleavage mode, showing extensive plastic deformation during the bending process.