The Special Features of the Phase Formation and Distribution in the Titanium Nickelide Surface Layers Treated by Electron Beams

The special features inherent in the formation of the structural-phase states on the surface of titanium nickelide samples subjected to multiple low-energy high-current variable energy density pulsed electron beam irradiation are investigated. The parameters of the electron beam operated in the fivefold surface melting regime are as follows: pulse duration τ = 150 μs, current I = 70 А, and energy densities Е<inf>1</inf>, Е<inf>2</inf>, and E<inf>3</inf> = 15, 20, and 30 J/сm², respectively. The surface layer structure was examined by methods of the x-ray diffraction analysis and transmission electron microscopy. It is found that in the irradiated TiNi samples with Е ≤ 20 J/сm², the layer containing a martensite phase lies at a certain depth below the surface rather than on the surface. In the irradiated TiNi sample with E<inf>3</inf> = 30 J/сm², the subsurface region is in a two-phase state (B2 + B19′), with the В19′ phase being predominant. It appears that the lower is the energy density, the smaller is the amount of the martensite phase.