RADIATION-DAMAGE OF NI3AL BY 100 KEV ELECTRONS

Radiation damage in the high-temperature intermetallic Ni3Al due to electron beam irradiation at 100 kV is reported. Preferential surface sputtering of aluminium is found to occur under conditions typical for microanalysis in an ultra-high-vacuum scanning transmission electron microscope. The overall sputtering cross-section is 20 b which implies a total loss rate of 7 monolayers per second. The subsequent nickel enrichment of the specimen can seriously affect attempts at determining the local chemistry of grain boundaries. Simple models for the mass loss are discussed, as are strategies for reducing the radiation damage. A b.c.c.-to-f.c.c. phase transition is expected to occur in radiation-damaged NiAl.