Microstructural characterisation of Ni_(75)Al_(25) and Ni_(31.5)5Al_(68.5) powder particles produced by gas atomisation

摘要

In this work the microstructures of gas atomised Ni_(75)Al_(25) and Ni_(31.5)Al_(68.5) at.% powder particles below 100 μm in size have been studied. The gas atomised Ni_(75)Al_(25) powder particles are mainly spherical. The solidification of this alloy is very fast, and its microstructure consists of a dendrite and lamellar structure of partially ordered γ-(Ni), γ'-Ni_3Al Ll_2 phase, and p-NiAl phase. The order increases with the powder particle size. The gas atomised Ni_(31.5)Al_(68.5) powder particles are also spherical in shape. The microstructure consists of Ni_2Al_3 dendrites with interdendritic peritectic NiAl_3 and eutectic NiAl-3 + α-Al. The amount of the Ni_2Al_3 increases as the cooling rate increases. NiAl phase is absent in the gas atomised Ni_(31.5)Al_(68.5) powder.