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

摘要

Structural-phase conditions, nano- and microhardness of the Ti_(49.5)Ni_(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 A (initial a_(B2) = 3.0129 ± 0.0005 A), 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.