Reaction Process and Pore Structure Control of Porous NiAl Intermetallic Compounds via Thermal Explosion

Porous NiAl intermetallics were synthesized from Ni-50at.%Al powder compact using an energy-saving and facile method of thermal explosion (TE). The effect of preheating treatment at 470 °C for 2 h on exothermic behavior, macroscopic appearance, phase composition and microstructures are investigated. Results shown that the combustion temperature decreases from 1645 to 1516 °C and the synthesized porous NiAl compounds possess a complete cylindrical shape. Some Ni 2 Al 3 and NiAl 3 phases preferentially generate in the preheating process through the solid-phase diffusion reaction. Afterward, the eutectic reaction of Al-NiAl 3 and the melting of Al promote the occurrence of an obvious exothermic reaction even at a low temperature. After TE reaction, three-dimensional interconnected pore channels are formed among the product skeletons with a high porosity of 60%, indicating the pore structures of porous NiAl sintered compact can be well controlled. The oxidation kinetics curve suggests that porous NiAl compounds exhibit excellent oxidation resistance at high temperature.