• The melt-spun Ti70.5Fe29.5 eutectic alloy exhibits a unique three-layered microstructure: a thin amorphous–nanocrystalline (Am–NC) hybrid layer on the chilled side, a fully amorphous middle layer, and a nanocrystalline layer on the free side.
• Increasing wheel speed (cooling rate) promotes a thicker amorphous layer and Fe enrichment, highlighting the role of solute segregation in enhancing glass-forming ability.
• An unexpected metastable Ti4Fe2O phase forms within the nanocrystalline layer alongside β-Ti and B2-TiFe phases via a divorced eutectic growth mechanism.
• Rapid solidification combined with moderate oxygen contamination is essential for the formation of amorphous and metastable phases, offering insights for fabricating advanced Ti–Fe alloys.