Effect of heat treatments on microstructure and property of a high strength/toughness Ti-8V-1.5Mo-2Fe-3Al alloy

The influence of solution and aging parameters on the microstructures and mechanical properties of Ti-8V-1.5Mo-2Fe-3Al alloy was studied through microstructural observation and mechanical property test. It is a newly designed near beta titanium alloy for high strength and toughness on the basis of Ti-10V-2Fe-3Al alloy. According to microstructural observation, the shape and volume fraction of primary α phase is found to be determined by the solution treatment, while aging parameters control the precipitation behavior of secondary α platelets. Moreover, the effect of aging time on tensile properties is slighter compared with that of aging temperature. Tensile test reveals the dependence of mechanical properties on the heat treatment parameters, according to which the tensile strength and elongation can be controlled in a range of 1230-1435 MPa and 9-13%. It is a little superior to the Ti-1023 alloy, the alloy solution treated at 800-820 °C for 1 h and aged at 550-600 °C for 2-8 h has well balanced combination of strength and ductility. At the same strength level, the Ti-8V-1.5Mo-2Fe-3Al alloy has higher toughness and higher ductility than the Ti-1023 alloy, the reason is unknown and should be studied further. Morphological features of the fracture surfaces are consistent with the tensile test result and provide further information on the intragranular fracture behavior when solution treated above the β-transus.