부산대학교 도서관

Nanoindentation experiments combined with atomic force microscopy imaging were performed on a two-phase Ni-base superalloy at various angles between indentation direction and crystallographic orientation. The nanohardness and the indentation modulus were extracted from the unloading part of the load –displacement curves recorded during the experiments. For small indentations close to or at interphase boundaries it was found that the indentation modulus was affected by the presence of the boundaries, compared to modulus values obtained from indentations far from the boundaries. The effect of the geometrical situation on the mechanical properties – specifically, the distance and angle between the indenter and the interphase boundary involved, and the contour shape of the boundary – were investigated. Moreover we tried to explain the modified moduli by a lattice rotation caused by the deformation of the material surrounding the indent. It turned out that a homogeneous lattice rotation alone cannot explain the experimental results.