VAMAS TWA #3
Project #11: CEN/VAMAS Phase Volume Fraction Round Robin
Quantitative Microscopy II
Organized as a joint VAMAS/CEN TC 184 project by the Center for Technical Ceramics,
Eindhoven University (Drs. Dortmans, Hendrix, de With), and the National Physical Laboratory,
UK (Drs. Bennett, Morrell)
Objectives
- Evaluate manual and automated image analysis (AIA) methods for characterization of
phase volume fraction in ceramic microstructures.
- Verify that results are consistent to within industrially appropriate uncertainty levels.
- Compare consistencies of AIA systems.
Approach
Each lab analyzed a computer-drawn Dirichelet tessellation image, photographs and/or .TIF files of 4 micrographs
(2 materials). Ecah lab also polished, etched and photographed one alumina/zirconia specimen.
The materials were a two phase barium titatnate/itanium oxide (~50%-50%), and an alumina/zirconia (~5%-6% zirconia)
with a small amount of porosity.
SEM backscattered and/or secondary electron images were used.
Status
Round robin completed in 1998. 27 laboratories participated.
Final report completed and distributed.
Principal Findings
- Both the manual and automatic image analysis had statistically consistent and reproducible
results. The manual results were more precise.
- AIA on micrographs with clear contrast and distinguishable phases had scatter of Vf of
±4% volume fraction. More consistent results are obtained if the microstructures are
adjusted by the human eye, rather than using completely automatic means.
- Many other specific observations were made about specimen preparation, AIA
techniques, .TIF file formats and image cropping, and effects of pores and pull outs.
- In general, both the manual and automatic image analysis methods had statistically
consistent and reproducible results. Scatter increased with complexity of the
microstructure. Phase differentiation and discrimination were key controlling parameters.
The manual counting method was outstandingly consistent. An increase in scatter with
AIA was related to contrast distribution of the micrographs. In some cases the human eye
and brain could easily recognize and interpret phases, whereas the completely automated
computer analysis had more difficulty correctly differentiating the phases. Human
interaction (filtering, contrast adjustments, etc) with the AIA images is essential for best
results.
Standards Impact
This project will contribute to a draft CEN standard.
Publications
- E. G. Bennett, L. J. M. G. Dortmans, M. Hendrix, R. Morrell, and G. De With, "CEN/VAMAS
Study of Phase Volume Fraction Measurement - A Preliminary Review of Results," pp. 2111 -
2114 in Key Engineering Materials, Vols. 132-136 (1997) Trans Tech, Switzerland, presented at
the European Ceramic Society Conference, Versailles, France, June 1997.
- M. Hendrix, E. Bennett, R. Morrell, L.J.M.G. Dortmans, and G. de With, "CEN/VAMAS
Phase Volume Fraction Round Robin," VAMAS Report # 35, National Physical Laboratory,
Teddington, UK, May, 1988.
- M. Hendrix, E. Bennett, R. Morrell, L. J. M. G. Dortmans, and G. de With, "CEN/VAMAS Phase
Volume Fraction Round Robin,", British Ceramic Transactions, Vol. 97, No. 6 (1998), 293-300.
For more information or copies of the reports, contact:
Dr. L. Dortmans, CTK, Technische Universiteit Eindhoven, P.O. Box 5955600 AN Eindhoven, the NETHERLANDS , Tel: (+31) 40 445619,
email: dortmans@tpd.tno.nl
or
Dr. Roger Morrell, Bldg. 13,National Physical Laboratory, Teddington, Middlesex, TW11 OLW, UNITED KINGDOM, Tel: (+44) 181 943 6381,
email: rm@npl.co.uk
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