Tensile and fracture toughness properties of unirradiated and neutron irradiated titanium alloys

In the unirradiated condition the Ti6Al4V (α+β) alloy has slightly higher tensile strength and noticeably lower ductility compared to that of the Ti5Al2.5Sn (α) alloy both at 50 and 350 °C. The fracture toughness behaviour of both alloys is similar at ambient temperature. At 350 °C, on the other hand, the fracture toughness of the (α) alloy is lower compared to that of the (α+β) alloy. Neutron irradiation at 50 °C to a dose level of 0.3 dpa caused hardening, plastic instability and a substantial reduction in fracture toughness of both alloys. Irradiation at 350 °C resulted in a substantial hardening and a significant decrease in the fracture toughness in the (α+β) alloy due to irradiation induced precipitation whereas only minor changes in the tensile and fracture toughness behaviour were observed in the (α) alloy. The tensile and fracture toughness properties of the (α+β) alloy are more strongly affected by neutron irradiation compared to that of the (α) alloy.