A TEM/EDS INVESTIGATION ON RADIATION-INDUCED COMPOSITION CHANGES OF Ni2Al3 AND NiAl3 UNDER BOMBARDMENT WITH Ar+IONS
氩离子轰击感生Ni2Al3和NiAl3成分变化的TEM/EDS研究

A rapidly solidified Ni-50%Al (mass fraction)alloy ribbon mainly consisting of Ni2Ala and NiAls phases was Ar+ ion etched with energies of 3, 5 and 7 keV respectively and the specimens were examined by high resolution electron microscopy (HREM) with super-thin-window EDS. The results show that under 3-7 keV Ar+ ion bombardment, the compositions of both NiaAla and NiAl3 change greatly and the Ni concentration is much higher than the corresponding stoichiometric one. With decreasing the ion energy the content of Ni in the phases increases. After 3 keV Ar+ ion bombardment the contents of Ni in these two phases are nearly the same, about 87% (atomic fraction), the original crystal structure of NiAls phase is kept, while the structure of Ni2Ala phase changes partly to a bcc structure.