Process control of reactive rapid prototyping for nickel-aluminides-II

Reactive rapid prototyping is a new freeform fabrication method for intermetallics which is a combined process of the combustion synthesis and rapid prototyping. Nickel-aluminide objects are built through microjoining of small nickel-aluminide beads which are formed by ejecting fused aluminum droplets onto a nickel powder bed. In order to obtain fine objects, it is necessary to minimize the bead size and control the productʹs composition. Nickel addition to aluminum was effective to reduce the reaction heat for a decrease in a bead size. Increasing temperature of aluminum droplets to 1000 °C tended to form beads being rich in NiAl phase. A newly developed nozzle with double orifices could eject aluminum droplets uniformly and continuously, resulting in forming a thin line of nickel-aluminide with ∼0.7 mm in width and a simple 2D structure with a few pores and cracks.