Microstructure and mechanical properties of NiAl and NiAlB alloys produced by rapid solidification technique

Abstract

Abstract Rapidly solidified NiAl intermetallic ribbons were produced by chill-block melt spinning in the composition range 68–90 at.% Ni with and without small additions of boron (200, 2000, 4000 wt.ppm). The microstructures of the ribbons were investigated by X-ray diffraction and transmission electron microscopy. The results can be explained based on Norbaskhsh and Chen's metastable phase diagram, in the Ni3Al region. The microstructure in the hypoeutectic compositions shows an absence of anti-phase domain boundaries. The microstructure in the hypereutectic compositions shows a bimodal distribution of anti-phase domains. Composition effects in yield strength and ductility were investigated by uniaxial tensile tests at room temperature. It was noticed that the yield strength increases when boron content increases from 200 up to 2000 wt.ppm B. It was observed that the boron level at 200 and 2000 wt.ppm did not influence the ductility. Ribbons with 4000 wt.ppm B are brittle. The mechanical properties can be explained in terms of the observed microstructures.