Enhanced tensile strength and fracture toughness of a Ti-TiAl metal-intermetallic laminate (MIL) composite

摘要

High temperature titanium alloy/Ti-43Al-9V metal-intermetallic laminate composite was successfully fabricated by hot-pack rolling. The titanium alloy exhibits a lamellar structure and the TiAl alloy consists of B2 phase and elongated gamma phase. Due to the low rolling and annealing temperature, the TiAl alloy shows a low extent of dynamic recrystallization (69.3%) and a high dislocations density (17%). The composite shows an excellent combination of the enhanced tensile strength and fracture toughness. The tensile strength of composite at 25 degrees C and 700 degrees C are 845 MPa and 730 MPa respectively. The fracture toughness of composite are 29.4 MPa.m(1/2) and 26.6 MPa.m(1/2) in arrester orientation and divider orientation respectively, which are much higher than monolithic Ti-43Al-9V alloy. The strengthening of composite is mainly attributed to high density dislocations and sub -structures stored in composite and the toughening mechanisms of composite are crack deflection, secondary cracks and crack tip convolution.