Characterisation of lattice damage formation in tantalum irradiated at variable temperatures

Summary The formation of radiation‐induced dislocation loops and voids in tantalum at 180(2), 345(3) and 590(5)°C was assessed by 3MeV proton irradiation experiments and subsequent damage characterisation using transmission electron microscopy. Voids formed at 345(3)°C and were arranged into a body centred cubic lattice at a damage level of 0.55 dpa. The low vacancy mobility at 180(2)°C impedes enough vacancy clustering and therefore the formation of voids visible by TEM. At 590(5)°C the Burgers vector of the interstitial‐type dislocation loops is a , instead of the a/2 Burgers vector characteristic of the loops at 180(2) and 345(3)°C. The lower mobility of a loops hinders the formation of voids at 590(5)°C up to a damage level of 0.55 dpa. Lay description High‐temperature metallic materials for demanding technological applications in radiation environments, such as future nuclear reactor systems and enhanced‐output targets for spallation sources, will be subject to the continuous bombardment of energetic particles at elevated temperatures. Tantalum constitutes an advanced candidate material for those applications due to its high radiation tolerance, ductility and water corrosion resistance. We have characterised the damage caused by proton bombardment to tantalum at variable temperatures using transmission electron microscopy. The results revealed significant differences in structural damage as a function of temperature and damage level, and therefore help to understand the formation, or otherwise, of voids induced by radiation. These results constitute unique evidence of the occurrence of structural damage and voids in tantalum, which will pave the way to reliable predictions of radiation‐induced swelling of tantalum‐based components in future applications.