![]() ![]() B2-NiAl has a high yield stress, whereas the martensite phase deforms already at low stresses. Ni-rich NiAl transforms to martensite by rapid cooling. The intermetallic compound NiAl with B2 structure was studied in the composition range Ni55Al45–Ni64Al36 (at.%). A straightforward criterion that is proved to be applicable is used to distinguish brittle fracture from ductile fracture. Both isotropic and anisotropic critical stress intensity factors are derived and compared for different crack orientations. By examining different fracture behaviors, we find the surface energy and the available slip planes play a combined role in determining the fracture mechanisms near a crack tip. Particularly, some of these fracture mechanisms are found to be consistent with the latest experimental results. Initial crack deflection, brittle fracture by cleaving along low surface energy plane, ductile fracture as a result of dislocation emission and fracture accompanied by deformation twinning are all observed near crack tips of different crystal orientations. The quasicontinuum (QC) multiscale method is used to investigate anisotropic fracture behaviors of body-centered cubic (BCC) rare metal tantalum (Ta) loaded in Mode I and different fracture mechanisms are discussed from nanoscopic to continuum perspectives to have a deep understanding of brittle and ductile fracture. ![]()
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