A new freeform fabrication method for intermetallics named Reactive Rapid Prototyping (RRP) has been developed. A 2D structure of nickel aluminde is fabricated by micro joining of the small elemental beads which is formed due to the exothermic synthesis reaction of the molten aluminum droplets injected onto the nickel powder bed eventually forming a 3D object through the layer by layer formation process. The RRP is systematically controlled by a computer. The effect of contact area between the aluminum droplet and the nickel powder bed with different nickel bed thicknesses was investigated. The reaction heat was controlled by replacing the pure aluminum to the aluminum alloy. The addition of fine alumina particles to the nickel powder bed effectively controlled the spreading of the bead formation. A thin line of the nickel aluminide synthesized, about 0.7mm, was drawn successfully. Joinings between adjacent beads and between layers were successfully performed without cracks and pores as well. The boundary region between layers was composed of NiAl phase, but the interior did not reach the stoichiometric composition.
