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Effect of Crystallographic Orientation on The Fracture Toughness of NiAl Single Crystals

  • S. Shrivastava (a1) and F. Ebrahimi (a1)


In the present study, single-edge notched bend specimens of NiAl single crystals were tested in {100}<010>, {101}<101=, and {101}<010} orientations before and after heat-treating the notched specimens at 1000°C for one hour. The fracture toughness data for the non heat-treated specimens were found to be consistent with the previous results. An increase in the fracture toughness of NiAl was observed in all orientations studied upon heat-treating the notched specimens. The toughness ratio for the two orientations obtained from the heat-treated notched specimens was found to be 1.2. This ratio is in agreement with the reported stress analysis considering the crack kinking in {100} oriented specimens. A detailed SEM analysis revealed that the electric discharge machine (EDM) cutting of the notch caused the formation of sharp microcracks at the notch front and also created internal stresses in the vicinity of the notch. The increase in toughness upon heat treatment is attributed to the modification of EDM damage.



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