Micro-cantilever fracture testing has been proven to be a very reliable method to determine the fracture toughness at the very small scale. In the work by Ast et al.[1] the influence of the specimen size on the fracture behavior of single and polycrystalline tungsten has been investigated in detail from which it can be concluded that the fracture toughness as analysed with the J-integral approach slightly increases with the specimen size.
Here we focus on the brittle-to-ductile transition and the influence of pre-deformation and He irradiation on W single crystals. The fracture toughness is analysed in a temperature regime from 233 K up to 353 K with a FemtoTools in-situ nanoindentation system. Pre-deformation by compression in the <110>direction led to a population of specific glide systems. The results show depending on the sample orientation an increase of the hardness and a slightly higher fracture toughness at low temperatures. Irradiation by He+ ions clearly lead to a decrease of the fracture toughness although the hardness increases. The experimental results will be discussed in comparison with modelling results.

[1]     J. Ast, M. Göken, K. Durst, Acta Materialia 138 (2017) 198-211