Formation of metastable phase and its influence on the solidification microstructure of highly undercooled eutectic Fe₄₀Ni ₄₀B₂₀ alloy

Solidification of a highly undercooled eutectic Fe₄₀Ni ₄₀B₂₀ alloy melt has been studied by high-speed video in combination with an analysis of the temperature history. The metastable phase with a colony shape structure solidified primarily from the melt. DSC analysis confirmed the formation of the metastable phase. The metastable phase was re-melted, transformed or decomposed into stable phases during further solidification or cooling processes, and gave birth to the final as-solidified structures. On this basis, the effects of the metastable phase formation and transformation on evolution of the as-solidified structure is described.