The mechanical properties of the Fe2Nb Laves phase (C14 structure) in equilibrium with γ-Fe (fcc) changes substantially depending on the type of ternary solute atoms. Ni atoms replacing Fe atoms in Fe2 sublattice sites introduces basal planar faults and significantly softens the Fe-rich Laves phase; this suggests that Ni in solution may enhance the plastic deformability of the Laves phase. To demonstrate this possibility, we have examined mechanical properties of the Laves phases by uniaxial compression of ~2 μm diameter micropillars produced by focused ion beam milling from a Fe-Nb-Ni ternary alloy consisting of a two-phase microstructure of the Laves phase and γ-Fe. The Laves phase micropillars exhibit high strength of about 6 GPa (~G/30) approaching the theoretical shear strength of the material, followed by a burst of plastic strain and shear failure on the basal plane. If dislocation sources in the form of dislocation loops on a non-basal plane are introduced into the Laves phase micropillars by nanoindentation prior to compression, yielding occurs at a significantly lower stress level of about 3 GPa and plastic deformation by slip proceeds on a pyramidal plane close to (-1-122). Furthermore, if regenerative dislocation sources for basal slip are present in the micropillar, the Laves phase can be continuously plastically deformed in a stable manner to at least 5% strain with plastic deformation commencing at a significantly lower stress of 800 MPa. The corresponding critical resolve shear stress (CRSS) for moving these basal dislocations is ~310 MPa. We thus demonstrate an approach to examine/obtain fundamental plasticity parameters in traditionally brittle materials. Part of this study was carried under the research activities of “Advanced Low Carbon Technology Research and Development Program” (ALCA) in JST (Japan Science and Technology Agency).
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