The tensile and fracture toughness properties of a (TiBw + TiCp)/Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe composites after heat treatment

This study investigated the tensile and fracture toughness properties of a new (TiBw + TiCp)/Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe composite subjected to solution treatment at 800 °C for 1 h with air cooling followed by aging at 440 °C, 480 °C, and 520 °C for 8 h with air cooling. The composite grains were coarse with distinct boundaries after the solution treatment. As the temperature was increased, αp merged in triangle boundaries and αs became finer. The basket two-parallel αs phase comprised many substructures, which generated many dislocations. Finer αs corresponded to higher strength and fracture toughness. The ultimate tensile strength and yield strength after the solution treatment decreased by 12.5% and 11.3%, respectively. However, the strength significantly improved after aging heat treatment. The highest ultimate tensile strength of 1521 MPa with a 7.2% elongation was reached after aging at 440 °C. The ultimate KIC value was 65 MPa m1/2 after aging at 480 °C. The (TiBw + TiCp) reinforcements formed a streamline along the deformation direction, which enhanced the strength and fatigue toughness. The reinforcements improves the fracture toughness by hindering crack propagation to extend the expansion path and increase the amount of absorbed impact energy.