Surface microstructure and B2 phase structural state induced in NiTi alloy by a high-current pulsed electron beam

L. L. Meisner, M. G. Ostapenko, A. I. Lotkov, A. A. Neiman

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12 Citations (Scopus)

Abstract

In the work, we studied structural phase states in surface layers of electron beam-irradiated nickel-titanium (NiTi) alloy depending on beam energy density. The surface of NiTi specimens was exposed to pulsed irradiation (pulse duration τ = 150 μs, number of pulses N = 5) by a low-energy high-current (I = 70 A) electron beam with surface melting at electron beam energy densities E1 = 15 J/cm2, E2 = 20 J/cm2, and E3 = 30 J/cm2. The surface layer structure was examined by X-ray diffraction analysis and transmission electron microscopy. It is found that in the NiTi specimens irradiated at E ≤ 20 J/cm the layer that contains a martensite phase resides not on the surface but at some depth from it. In the NiTi specimens irradiated at E = 30 J/cm, the entire modified surface zone is characterized by a two-phase state in which the B19′ phase dominates over the B2 phase. It is supposed that a barrier to B2 → B19′ martensite transformation in the melted NiTi layer irradiated at E ≤ 20 J/cm2 is high inhomogeneous residual stresses varying with depth from the irradiated surface.

Original languageEnglish
Pages (from-to)44-52
Number of pages9
JournalApplied Surface Science
Volume324
DOIs
Publication statusPublished - 1 Jan 2015

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Keywords

  • B19′ martensite phase
  • B2 phase
  • Low-energy high-current electron beams
  • Nickel-titanium alloy
  • Structural phase states
  • X-ray diffraction analysis

ASJC Scopus subject areas

  • Surfaces, Coatings and Films

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