Surface alloying of Al films/Ti substrate based on high-current pulsed electron beams irradiation

Ti–Al surface alloy was fabricated using a cyclic pulsed liquid-phase mixing of predeposited 100 nm Al film with α-Ti substrate by low-energy high-current electron beam. Electron probe micro-analysis (EPMA), grazing incidence X-ray diffraction analysis (GIXRD), transmission electron microscopy (TEM), and nanoindentation were used to investigate the characterization of Ti–Al surface alloy. The experimental results show that the thickness of alloy layer is ~3 μm, and the content of Al in the ~1 μm thickness surface layer is ~60 at%. The tetragonal TiAl and TiAl₂ intermetallics were synthesized at the top surface, which have nanocrystalline structure. The main phase formed in the ~2.5 μm thick surface is TiAl, and there are few TiAl₂ and Ti₃Al phase for the alloy. Dislocation is enhanced in the alloyed layer. The nanohardness of Ti–Al surface alloy increased significantly compared with α-Ti substrate due to the nanostructure and enhanced dislocation. Since the e-beam remelted repeatedly, the Ti–Al surface alloy mixed sufficiently with Ti substrate. Moreover, there is no obvious boundary between the alloyed layer and substrate.