A simple method for producing fully dense Ni3Al by reactive sintering

The major problem to synthesize Ni[sub 3]Al components with common PM facilities is the large shrinkage porosity generated from reacted Ni and Al powders after being sintered, which are also found in many self-propagating high-temperature synthesis (SHS). Cold working to collapse the sintered pores, then healing followed by annealing treatment is found difficult to conduct on porous Ni[sub 3]Al products due to the great strength of this material. A multi-stage sintering with preliminary heating to cause reactive sintering of Al and Ni powders followed by cold working to collapse and to eliminate primary pores, then sintering at high temperature to heal the collapsed pores and to transform the phase to final Ni[sub 3]Al appears ideal. However, the primary product NiAl phase from reactive sintering was found too brittle to deform, as they authors discuss subsequently. Here they propose a possible approach to almost fully densified Ni[sub 3]Al PM products with simple laboratory facilities with a technique to decrease the temperature of a specimen during the preliminary reactive sintering process of Ni and Al compacted powders.