Abstract
The impact test was carried out to investigate the intermediate temperature brittleness of single crystal Ni based superalloy. The samples were impacted at the velocity of ∼5 m s− 1. The results showed that the impact toughness also exhibited intermediate temperature brittleness, which is similar to the situation in tensile. The samples showed the highest impact toughness at 600°C but exhibited the lowest impact toughness at 760°C. Results showed that the variety of impact toughness was due to the deformation mechanism. At 600°C, a/2 < 110> dislocation slips on the {111} slip system were attributed to the high impact toughness; however, a/2 < 110> dislocation slips from octahedral {111} planes to cubic {100} planes resulted in significant work hardening, leading to the decrease of impact toughness.