Structural-phase condition, unelastic and plastic behavior and nanohardness of the TiNi surface layers modified by an ion- and electron irradiation

Abstract

Structural-phase conditions, nano- and microhardness of the Ti 49.5Ni 50.5 alloy surface layers modified by the high-dose ion implantation (HDII) and the pulsed low-energy high-current electron beam (LEHCEB) were studied by Auger electron spectroscopy, grazing incidence X-ray diffraction analysis and the CSEM Nano Hardness Tester. It was found that the Ni-depleted surface layer (>160 nm) was observed for the samples treated by LEHCEB at pressure ∼10 −4 mbar. Irradiation in oil-less vacuum does not change the Ni, Ti and O concentration depth profiles. The influence by means LEHCEB and then by HDII (by Zr + or Ti + ions) leads to the formation of a Ti–Zr–(Ni < 20 at.%)–O and Ti–(Ni < 20 at.%)–O surface layer. Due to fast (∼10 9 K/s) quenching from the melt the single-phase (B2) structure in the surface layer of thickness 1–5 μm is formed. The new B2-phase has the grain size 1–5 μm, the lattice parameter a = 3.0072 ± 0.0005 Å (initial a B2 = 3.0129 ± 0.0005 Å), the coherent-scattering region size D csr ≈ 10–20 nm. Within the outer layer (∼300 nm in depth) modified by LEHCEB microhardness are twice as higher as of the initial sample.