Microstructural characterisation of Ni75Al25 and Ni31.5Al68.5 powder particles produced by gas atomisation

Highlight: ► Successful production of gas atomised Ni75Al25 and Ni31.5Al68.5 powder particles. ► Characterization of the as-solidified microstructure of < 100 mm powder particles. ► Complementing work carried out in the by magnetic levitation and impulse atomization. -- Abstract: In this work the microstructures of gas atomised Ni75Al25 and Ni31.5Al68.5 at.% powder particles below 100 μm in size have been studied. The gas atomised Ni75Al25 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′-Ni3Al L12 phase, and β-NiAl phase. The order increases with the powder particle size. The gas atomised Ni31.5Al68.5 powder particles are also spherical in shape. The microstructure consists of Ni2Al3 dendrites with interdendritic peritectic NiAl3 and eutectic NiAl3 + α-Al. The amount of the Ni2Al3 increases as the cooling rate increases. NiAl phase is absent in the gas atomised Ni31.5Al68.5 powder