Formation of porous Ni-Al intermetallics through pressureless reaction synthesis

Pressureless reaction synthesis method was used to produce porous NiAl and Ni₃Al intermetallics using elemental Ni and Al powder mixture in this investigation. The sintering behavior of Ni and Al mixed powder compacts was investigated by applying XRD, SEM and EDS in the temperature range of 510-1000 °C. It has been found that the formation of porous Ni₃Al and NiAl was accompanied by the volume expansion due to the formation of intermediates and pores during the reaction synthesis procedure. The intensive reaction and phase transformation procedures were similar in the Ni-14 wt% Al and Ni-30 wt% Al. However, the maximum pore size, expansion ratio and porosity have been found to be varied with the sintering temperature and Al content in the compacts. The Al content in the green compacts could effectively influence the volume expansion and pores of the products: the volume expansion and maximum pore size of NiAl are much higher than that of Ni₃Al under the same sintering procedure.