Undercooled solidification of Ni-3.3wt.%B alloy

Ni-3.3wt.%B alloy solidified at different undercooling by glass fluxing has been studied. The as-solidified structure is mainly controlled by the undercooling for eutectic solidification, ΔT ₂, instead of ΔT ₁, the undercooling for primary solidification. For ΔT ₂<145±5K, two recalescence peaks appear in the cooling curves, while for ΔT ₂ ≥145±5K, three recalescence peaks appear in cooling curves. If ΔT ₂<145±5 K, the primary α-Ni and Ni-Ni ₃B eutectic phases occur, whereas, if ΔT ₂≥145±5 K, two kinds of dot phases occur. Further analysis declares that, the regularly distributed dot phases with larger size come from the transformation L→Ni ₂₃B ₆+Ni, whereas, the irregularly distributed ones with smaller size come from Ni ₂₃B ₆→Ni ₃B+Ni. Both of them have a contribution to strengthen the mechanical property.