Effect of preheating treatment at 575 °C of green compacts on porous NiAl

The effect of preheating treatment on NiAl compacts was systematically investigated. The preheating treatment of green compacts at 575 °C preserves their original shapes. The formation of porous NiAl alloys usually accompanies with the volume expansion due to the formation of Ni2Al3 during the preheating treatment. The pore structures of porous NiAl alloys strongly depended on the preheating duration. The volume expansion, porosity and the maximum pore size increased with prolonged preheating treatment duration. Whereas the maximum pore size of final product decreased with increased preheating treatment duration. It has been found that the pore structures especially the maximum pore size strongly depend on the volume expansion determined by the intensity of exothermic reaction from the preheating temperature to the finally sintering temperature.