Measuring the Fracture Toughness of TZM and ODS Molybdenum Alloys using Standard and Sub-Sized Bend Specimens

Oxide Dispersion Strengthened (ODS) and TZM molybdenum have excellent creep resistance and strength at high temperatures in inert atmospheres. Fracture toughness and tensile testing was performed at temperatures between -1 50°C and 450°C to characterize 6.35 mm thick plate material of ODS and TZM molybdenum. A transition from low fracture toughness values (5.8 to 29.6 MPaJm) to values > 30 MPaJm is observed for TZM molybdenum in the longitudinal orientation at 100°C and in the transverse orientation at 150°C. These results are consistent with data reported in literature for molybdenum. A transition to low fracture toughness values (c 30 MPaJm) was not observed for longitudinal ODS molybdenum at temperatures 2 150"C, while a transition to low fracture toughness values (12.6 to 25.4 MPaJm) was observed for the transverse orientation at room-temperature. The fine spacing of La-oxide precipitates that are present in ODS molybdenum result in a transition temperature that is significantly lower than any molybdenum alloy reported to date, with upper bound fracture toughness values that bound the literature data. A comparison of fracture toughness values obtained using a IT, 0.5T, and 0.25T Charpy shows that a 0.5T Charpy could be used as a sub-sized specimen geometry.