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, α_p merged in triangle boundaries and α_s became finer. The basket two-parallel α_s phase comprised many substructures, which generated many dislocations. Finer α_s 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 K_IC value was 65 MPa m^1/2 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.