Effect of nanocrystallization on the mechanical behavior of Fe-Ni-based amorphous alloys

Melt-quenched amorphous alloys Fe₅₈Ni₂₅B₁₇, Fe₅₀Ni₃₃B₁₇, and Ni₄₄Fe₂₉Co₁₅B₁₀Si₂ are used to study the effect of the structural parameters of the nanocrystalline phases precipitating at the first stage of crystallization on the strength characteristics of the alloys in an amorphous-nanocrystalline state. It is shown that, at a constant nanoparticle size, the dependence of microhardness H _V on the volume fraction (V _V ) or the volume density (N _V ) of these nanoparticles can be described by the relation HV = K(V _V ) ⁿ , where n = 1/3. A relation HV = f(d) that is analogous to the Hall-Petch relation is detected at a fixed volume density of nanoparticles and their average size d > 80–100 nm. At d < 70–80 nm, HV decreases anomalously with decreasing d.