Simultaneously achieving high tensile strength and fracture toughness of Ti/Ti-Al multilayered composites

Ti/Ti-Al multilayered composites with different volume fractions of α-Ti layer were fabricated by hot press sintering. Microstructural observation indicates that the phase compositions in all the composites are α-Ti, Ti₃Al, TiAl, TiAl₂ and TiAl₃. The tensile strength and fracture toughness of Ti/Ti-Al multilayered composites are influenced by the volume fraction of α-Ti layer. The composite with 53 vol% Ti presents the highest tensile strength and suitable ductility at room temperature, and its fracture toughness can reach 47.6 MPam, which is much higher than that of TiAl intermetallic alloy and Ti/Al₃Ti composites. Fracture analysis reveals that a certain volume fraction of Ti layers can effectively prevent the crack propagation when the crack is extended to the interface, resulting in high tensile strength and acceptable ductility at the same time. The improvement of toughness is associated with crack deflection and crack bridging provided by the appropriate thickness of remaining α-Ti layer.