Time-of-flight atom probe measurements on Ni3Al and Co3W

• Published in: Ultramicroscopy 2003-05, Vol.95 (1-4), p.207-213
• Main Authors: SOER, W. A, BRONSVELD, P. M, DE HOSSON, J. Th. M
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; Electron, positron and ion microscopes, electron diffractometers and related techniques; Exact sciences and technology; Impurities: concentration, distribution, and gradients; Impurity concentration, distribution, and gradients; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Physics; Structure of solids and liquids; crystallography
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/S0304-3991(02)00318-2

In this study, a VG FIM100 was taken into operation, consisting of a field-ion microscope (FIM), a time-of-flight atom probe (TOFAP) and an imaging atom probe. A tungsten specimen was used to calibrate the conversion of flight times to m/n values. The resulting relative mass resolution of the TOFAP was calculated to be m/Deltam approximately 500 FWHM. In time-of-flight measurements of homemade boron-doped Ni-rich Ni(3)Al, a so-called ladder diagram was constructed from the evaporation data of a pole. This ladder diagram revealed a very high degree of ordering in the alternating pure Ni and mixed Ni/Al planes: only 0.4% of the detected Al atoms were located on pure Ni planes. The number of null pulses to start a new plane was found to be much higher for Ni/Al planes (5 x 10(2)) than for Ni planes (1 x 10(2)). Moreover, the ladder diagram showed that boron was uniformly distributed through the matrix with nearly all boron found on pure Ni-planes. The suggestion that boron preferentially settles on these planes would be supported by reports of a strong Ni-B bond, since on Ni planes, B atoms can be accommodated on octahedral interstitial sites surrounded by only Ni atoms. Finally, we performed time-of-flight measurements on Co(3)W. The ion species observed in these measurements included a wide variety of WN(n)(2+) ions, with 0