Dimensional Changes Occurring During Reactive Sintering of Ni–Al–Mo Elemental Powder Mixtures

Abstract

Dimensional changes of elemental Ni–Al–Mo powder mixtures occurring during reaction sintering were investigated. Sintering treatments were conducted on powder compacts in a dilatometer at various heating rates. Heating rate is a crucial parameter affecting the dominant sintering mechanisms. Extensive shrinkage or swelling was observed for each investigated powder composition depending on the actual heating rate adopted during the dilatometric runs. From the dilatometric data and on the basis of the results of the microstructural characterisation, it was concluded that synthesis of alloy specimens by reaction sintering involves the initial formation of intermetallic aluminide phases, e.g. NiAl, by a highly exothermic solid state reaction. This process promotes the formation of an aluminium rich liquid phase which assists sintering. The influence of the processing parameters on the resulting microstructures is also discussed. PM/0774