Atom Probe Tomography of Nickel-Based Superalloys with Green or Ultraviolet Lasers: A Comparative Study

作者：Amouyal Yaron; Seidman David N^*

来源：Microscopy and Microanalysis, 2012, 18(5): 971-981.

DOI：10.1017/S1431927612001183

• atom probe tomography
• green-laser pulsing
• ultraviolet laser pulsing
• nickel-based superalloys
• signal-to-noise ratio
• mass-resolving power

Recent developments in the technology of laser-pulsed local-electrode atom-probe (LEAP) tomography include a picosecond ultraviolet (UV) laser system having a 355 nm wavelength and both external and in-vacuum optics. This approach ensures focusing of the laser beam to a smaller spot diameter than has heretofore been obtained using a green (532 nm wavelength) picosecond laser. We compare the mass spectra acquired, using either green or UV laser pulsing, from nickel-based superalloy specimens prepared either electrochemically or by lifting-out from bulk material using ion-beam milling in a dual-beam focused ion beam microscope. The utilization of picosecond UV laser pulsing yields improved mass spectra, which manifests itself in higher signal-to-noise ratios and mass-resolving power (m/Delta m) in comparison to green laser pulsing. We employ LEAP tomography to investigate the formation of misoriented defects in nickel-based superalloys and demonstrate that UV laser pulsing yields better accuracy in compositional quantification than does green laser pulsing. Furthermore, we show that using a green laser the quality of mass spectra collected from specimens that were lifted-out by ion milling is usually poorer than for electrochemically-sharpened specimens. Employing UV laser pulsing yields, however, improved mass spectra in comparison to green laser pulsing even for ion-milled microtips.

• 出版日期2012-10
• 单位西北大学