Multi-scale phase analyses of strain-induced martensite in austempered ductile iron (ADI) using neutron diffraction and
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Multi-scale phase analyses of strain-induced martensite in austempered ductile iron (ADI) using neutron diffraction and transmission techniques Xiaohu Li1,* , Sergio Soria2, Weimin Gan1, Michael Hofmann2, Michael Schulz2, Markus Hoelzel2, Heinz-Gu¨nter Brokmeier3, and Winfried Petry2 1
German Engineering Materials Science Centre (GEMS) At Heinz Maier-Leibnitz Zentrum (MLZ), Helmholtz-Zentrum Geesthacht GmbH, Lichtenbergstr. 1, 85748 Garching, Germany 2 Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1, 85747 Garching, Germany 3 Institute of Materials Science and Engineering, TU Clausthal, 38678 Clausthal-Zellerfeld, Germany
Received: 24 August 2020
ABSTRACT
Accepted: 24 November 2020
The content of strain-induced martensite in austempered ductile iron has been quantitatively determined using three different kinds of neutron methods: (1) high-resolution powder diffraction with subsequent standard Rietveld refinement, (2) phase quantification using pole figure measurements and (3) Bragg edge neutron transmission. The accuracy and scope of applications of these neutron diffraction and imaging techniques for phase quantification have been compared and discussed in detail. Combination of these methods has been confirmed as effective for dealing with problems like peak overlap in multiphase materials and texture formation after plastic deformation. Further, the results highlight the potential of using single peak pole figure data for quantitative phase analysis with high accuracy.
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The Author(s) 2020
Introduction Austenite, ferrite and martensite are the most prominent phases in iron-based materials. Many different kinds of methods like diffraction (XRD, synchrotron/neutron diffraction), Bragg edge transmission (BET), magnetic balance measurements, image analysis (optical microscopy, EBSD) have been used for quantification of phase contents in ironHandling Editor: P. Nash.
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10853-020-05619-x
based materials over the last decades [1–5]. Image analysis depends crucially on the quality of sample preparation; it can provide fast phase quantification with accuracy of ± 2 vol. % only when the parameters of the whole sample preparation process are optimized [1]. However, its application is severely limited by the grain size of the material, as samples with a grain size of less than 250 nm are not accessible [6, 7]. The magnetic balance method requires the existence of a single magnetic phase in multi-phase
J Mater Sci
alloys for quantitative phase analysis. The theoretical magnetic saturation of a sample with known phase composition will be calculated using an empirical equation [1, 8] and is subsequently taken as reference sample [1]. Imperfections in magnetic field, inaccuracy in sample weight and variation in spring modulus of elasticity result in relatively large errors in the calculation. If powder reference samples are used for calibration, an accuracy of ± 4 vol. % in the phase quantification can
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