Deformation processes at crack tips in NiAl single- and bicrystals

Fracture toughness and bond trapping of grain boundary cracks

“…The experimental determination of the fracture toughness of individual GBs is however challenging, as it requires the preparation of notched flat and defect-free GBs with defined misorientation. Therefore, only few measurements of GB fracture toughness exist [35,36]. Most experiments instead determine the fracture strength of GBs by measuring the tensile stress at which a GB fails in an uniaxial tensile test.…”

Local Fracture Toughness and Residual Stress Measurements on NiAl Bond Coats by Micro Cantilever and FIB- based Bar Milling Tests

“…Each H-bar is wide enough to provide enough space to cut two micro cantilevers (notches are indicated as white lines in Figure 2). [14,15,16]. It was reported that the grain orientation has an evident influence on fracture toughness.…”

A new method for fracture toughness determination of graded (Pt,Ni)Al bond coats by microbeam bend tests

“…Also NiAl is a highly ordered compound and shows significant elastic anisotropy, with an anisotropy ratio in modulus of $3.2 for stoichiometric NiAl [40]. It undergoes failure along well defined cleavage planes and has distinct hard and soft orientations [8]. Large anisotropy in mechanical properties like modulus and yield strength will influence crack kinking and branching, leading to toughening.…”

“…Bulk fracture toughness values from single crystal experiments are reported to lie anywhere between 5 and 14 MPa m 1/2 depending on the orientation of the crystals tested [8]. Tests on intergranular fracture in polycrystalline NiAl point out to low angle boundaries offering greater resistance to fracture than special and random grain boundaries [9].…”