Micromechanical toughness test applied to NiAl

A microscratch technique for determining the fracture toughness of brittle intermetallics is presented. Advantages include very small sample sizes and multiple tests on a single, flat polished surface. The fracture toughnesses of single-crystal NiAl in {001}〈100〉, {001}〈110〉, {110}〈110〉, and {110}〈100〉 crack orientations were evaluated using this technique. The results of the scratch testing are compared with measurements on small compact tension samples. Also, transmission electron microscopy is used to help explain the dislocation character of the resulting plastic zones in samples tested. Lastly, a model for determining the dislocation velocity during nanoindentation is presented to help understand the ductile-brittle transition temperature of semibrittle materials.