Mixing of Ta-Fe and Mo-Fe systems using a low-energy, high-current electron beam

Rutherford backscattering spectroscopy, Auger electron spectroscopy, conversion electron Mossbauer spectroscopy, transmission microscopy and scanning electron microscopy showed that treatment of a thin Ta or Mo film/alpha-Fe substrate system with a high-current electron beam (HCEB) of an energy density of 2.3-5.2 J cm(-2) resulted in a mixing of the system's components. In the energy range 2.3-3.3 J cm(-2) in the HCEB-irradiated Ta-Fe system, we found a mixed layer of a thickness of about 100 nm, which we relate to the formation of a stable compound (Fe2Ta, FeTa) and a non-equilibrium Fe5Ta2, compound. The irradiated surface is not uniform, being composed of Ta inclusions of a spherical form (300 nm diameter), solid-solution Fe(Ta) and amorphous-phase Fe-Ta. An increase in the pulse number results in the formation of the volume fraction FeTa and a dislocation density of 5 x 10(10) cm(-2). It has been shown that HCEB irradiation of the Mo-Fe system with energy flow densities of 2.3-3.3 J cm(-2) produced a mixed layer of a thickness of up to 150 nm, and a non-equilibrium Fe4Mo compound (Fe80Mo20) was formed. On increasing the energy density to 4.2 J cm(-2), we observed partial Mo ablation and the formation of a mixed compound with a Mo concentration of several at.%. (C) 1998 Elsevier Science S.A.