Crystallization behavior of spray-formed and melt-spun Al89La6Ni5 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 Al89La6Ni5 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 Al11La3(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.