查看文章

In situ micro-cantilever tests were carried out to determine the anisotropic fracture toughness of NiAl single crystals. Notched micro-cantilever beams with a beam length of 8μm, 1.5μm thickness and 1.8μm width were milled in so-called “hard” and “soft” orientations of NiAl using a focused ion beam. These cantilevers were loaded in situ with the help of a cantilever-based nanoindenter mounted inside a scanning electron microscope. A fracture toughness of 3.52±0.29MPam^1/2 was obtained for the “soft” orientation and 5.12±0.50MPam^1/2 for the “hard” orientation, which is in good agreement with literature values on the fracture toughness of macroscopic NiAl specimens. Furthermore, nanoindentations were performed for studying the size effects occurring at small length scales for both orientations. The applicability of the small sample geometries for testing the fracture toughness is finally discussed in terms of size …