Heterogeneous nucleation mechanism in Al–Fe–Si amorphous alloys

Al70Fe13Si17 alloys were melt-spun with commercial grain refiner additions containing TiB2 and Al3Ti particles. X-ray diffraction, calorimetry and transmission electron microscopy revealed incomplete vitrification. The size and number density of Al crystals increased with decreasing quench rate. Full crystallisation led to formation of β-Al9FeSi2 and Al. In as-quenched samples nucleation events on TiB2 particles were surrounded by nanocrystalline α-Al particles embedded in amorphous phase. Boride particles were covered in a thin Ti-containing layer and surrounded by a featureless zone reminiscent of a peritectic reaction and they exhibited an orientation relationship to next neighbour Al particles.