Centrifugal casting of Ni-Al intermetallic compounds produced by thermite-type combustion synthesis

Centrifugal precision casting of Ni-Al alloys produced by a thermite-type combustion synthesis has been examined. The compositions of the alloys were Ni-(25, 31, 37, 43 and 50) mol%Al. A graphite mold and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal easter. The mold had a cylindrical cavity (15-mm diameter and 10-mm length) with a slender sprue (4-mm diameter). When the combustion synthesis reaction was induced in the centrifugal force field, the synthesized molten Ni-Al alloy flew into the mold. This process was successfully applied in casting the synthesized Ni-Al alloys. On the other hand, the alloys did not flow into the mold under 1G. The formation of pores in the centrifugally cast alloy varied depending on the alloy composition: (1) The Ni-25 mol%Al and Ni-31 mol%Al alloys had very little porosity. (2) The Ni-37 mol%Al alloy had numerous micropores. (3) The Ni-43 mol%Al and Ni-50 mol%Al alloys had many macroscopic pores.