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.