High-rate growth-mode transitions in Al-Si eutectics

Irregular eutectic growth in an aluminum-silicon alloy is investigated using directional solidification. The high-rate transition from flake to fiber morphology is characterized in term of the three dimensional microstructure. The transition is observed to occur over the velocity range from 100 to 1000 mm/s, and two regimes of behavior are observed using a characteristic length scale defined by the spatial variation in local volume fraction