Kiyotaka Matsuura

Development of freeform fabrication method for Ti–Al–Ni intermetallics

Abstract A new droplet-based reactive rapid prototyping (RRP) method for making intermetallic parts is demonstrated. This method combines the processes of solid freeform fabrication (SFF) and combustion synthesis (CS). Intermetallic beads are produced by the CS reaction. These synthesized beads are assembled and joined by using the SFF technique with the aid of heat released from exothermic reactions. The intermetallic compound of Ti–Al–Ni is chosen to demonstrate this method. Ni was added to the Ti–Al system to enhance the reaction. Thermodynamics of the Ti–Al–X·NI (X=5, 10, 15 wt.%) system are calculated. The effects of the addition of Ni in powder bed and heating temperature of aluminum droplets on the width and thickness of the reacted area were investigated. As an example, a Ti–Al–Ni intermetallic bar with simple shape was fabricated as a demonstration of RRP.

Process control of reactive rapid prototyping for nickel aluminides

Abstract 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 products 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 1000xa0°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.