Effects of high-temperature air and vacuum exposure on tensile properties and fracture of ODS alloy MA6000

The effects of air and vacuum exposure at 1100 °C on tensile mechanical properties, notch fracture toughness, and fracture toughness at room temperature of MA6000 were investigated. By air exposure in the range of 2–1000 h, yield strength and ultimate tensile strength were decreased slightly, while fracture strain decreased significantly (40–50% of the as-received (as-rec.)). Also, notch fracture toughness was reduced by air exposure to ~75% of the as-rec. This decrease in strain and toughness was due to the occurrence of subsurface void formation zones, where fractures initiate. The mechanical properties and notch fracture toughness of the MA6000 vacuum-exposed for 24 and 240 h were almost the same as the as-rec.. even though there were slight subsurface void formations. Fracture toughness of the pre-fatigue-cracked compact tension specimen was not reduced by either air exposure or vacuum exposure.