The results are presented for an in situ synchrotron investigation of phase composition evolution during surface alloy synthesis. Surface alloys 3–5 µm thick are synthesized using pulsed melting with a microsecond low-energy, high-current electron beam. Three bilayer systems are studied: Ti(1000)/Zr, Y(1000)/Zr, and Mo(1000)/Zr, representing (1) alloys forming continuous solid solutions, (2) alloys with limited solubility and (3) alloys forming intermetallic compounds, respectively. In the first case, a surface alloy forms through the continuous solution of Ti in α-Zr as a homogeneous equilibrium substitutional solid solution with an average Ti concentration of 40 at.%. In the second case, gradual dissolution of Y in α-Zr forms an inhomogeneous metastable oversaturated solution with average and surface Y concentrations of 18 and 32 at.%, respectively. In the third case, an inhomogeneous metastable surface alloy forms, consisting of α- and β-Zr phases, with the latter predominating. The average and surface Mo concentrations are 30 and 42 at.%, respectively. Prior to the formation of β-Zr with a high Mo content, a nonequilibrium unidentified phase appears that could be referred to as a high-concentration solid solution of crystalline Mo with Zr embedded in it from the melt.

The paper presents the results of computer modeling of melting processes in a multilayer system consisting of ten alternating layers of B (360 nm) and Ti (140 nm) on a Ti substrate under the action of a low-energy high-current electron beam (LEHCEB). Numerical studies of the influence of energy characteristics of the electron-beam effect on the thickness and lifetime of the melt of the multilayer film B/Ti–substrate Ti system are carried out. It is shown that with an increase in the energy density of the LEHCEB the thickness of the melt of the multilayer B/Ti film and its lifetime increase. Based on the modeling results, optimal modes for the formation of multilayer composite coatings are obtained. It is found that for LEHCEB energy densities of 3.5, 4.5, and 5.5 J/cm², a coating with the following structure is formed: B-Ti surface alloy and a composite coating based on a titanium matrix with a reinforcing phase TiB₂; further from the surface there are alternating Ti and B films. For the energy densities of 3.5 and 4.5 J/cm² melting of the Ti substrate does not occur; therefore, for these modes, the martensitic structure of the substrate surface is preserved. Complete melting of the multilayer B/Ti film–Ti substrate system occurs at LEHCEB energy densities greater than 8.5 J/cm².