Microstructural evolution in spray-formed and melt-spun Al₈₅Nd₅Ni₁₀ bulk hybrid composites

Microstructure evolutions in the spray-formed and melt-spun Al₈₅Nd₅Ni₁₀ alloys were studied. The spray forming process has shown to be capable of directly producing a bulk scale Al₈₅Nd₅Ni₁₀ hybrid composite consisting of amorphous and nanostructured phases without the need of using an amorphous precursor. The spray-formed overspray flakes were partially amorphous, and the amorphous phase came from the undercooled liquid droplets upon deposition. The as-spray-formed deposit was completely crystallized due to the devitrification of the retained amorphous phase to nanoscale secondary crystals upon deposition. In the deposit and flake, the primary crystals were micro-scaled Al₆NdNi₂, and the secondary crystals devitrified from the amorphous phase during spray forming process were nanoscaled Al₃Ni and Al₆NdNi₂, dispersed in nanoscaled α-Al matrix. The completely devitrified melt-spun ribbon composite consisted of secondary crystals Al₃Ni, Al₁₁Nd₃ and Al₆NdNi₂ with nanoscale sizes, dispersed in the nanoscaled α-Al matrix. Deformation twins were observed in the primary Al₆NdNi₂ crystal in the as-spray-formed flake and deposit, but were not found in the secondary Al₆NdNi₂ crystals in the completely devitrified ribbon.