Crystallization behavior of spray-formed and melt-spun Al₈₉ La₆Ni₅ hybrid composites with amorphous and nanostructured phases

The crystallization behavior of spray-formed and melt-spun Al₈₉La₆Ni₅ alloys was studied. Spray forming process could produce a bulk scale Al₈₉La₆ Ni₅ hybrid composite consisting of amorphous and nanostructured phases directly without the need of an amorphous precursor. The fraction of amorphous phase in the spray-formed composite was determined to be 36% by DSC, which came mostly from supercooled liquid droplets upon spray forming. Amorphous phase partially devitrified to nano-scale fcc-Al secondary crystals during deposition. Two significant primary crystals observed in the spray-formed bulk hybrid composite are Al₃Ni and Al₁₁La₃ (Ni), but their size is reduced to about 1 μm. Contrary to the microstructure of spray-formed deposit, the heat-treated and fully devitrified melt-spun ribbon hybrid composite consists of nano-scale fcc-Al, Al₃Ni, Al₁₁La₃ as well as some metastable Al₆Ni and Al₄LaNi phases with sizes of about 200 nm. Deformation twins were found in the Al₁₁ La₃(Ni) crystals in spray-formed deposit, but not in the fully devitrified ribbon. Finally, the microstructure structure evolution of spray-formed deposit and heat-treated ribbon are studied and proposed.