PRECIPITATION BEHAVIOUR AND HARDENING OF B2-ORDERED Ni(Al, Ta)
PRECIPITATION BEHAVIOUR AND HARDENING OFB2-ORDERED Ni(Al, Ta)

Precipitation of Ni2Al in supersaturated NiAl containing Ta and corresponding hardening have been investigated by hardness measurements and by transmission electron microscope observations. Selected area electron diffraction, high resolution electron microscopy and energy dispersive X-ray spectrometer analysis have shown that the Ni2Al with a hexagonal structure precipitates coherently in the B2-NiAl matrix. Ni2Al is an ordered phase with a. unit cell parameter, aNi2All=aNiAl and CNi2Al= aNiAl. The orientation relationship between the Ni2Al precipitate and the B2-NiAl matrix is (0001)Ni2Al (111)NiAl and 1120]Ni2Al110]NiAl. NiAlhardens appreciably by the precipitation of Ni2Al phase.