Correlation between grain orientation and the shade of color etching

P. Szabó, I. Kardos

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Color etching is an extremely effective metallographic technique not only for making grains well visible, but also for making them distinguishable for automated image analyzers. During color etching, a thin film is formed on the surface of the specimen. The thickness of this layer is in the order of magnitude of the visible light and since both the metal-film boundary and the film surface reflect light, an interference occurs. A wavelength-component of the white line is eliminated and its complementary color will be seen on the surface. As the thickness changes, the colors also change grain by grain. The thickness of the film is dependent on several factors, mostly on the type of the phase. However, different color shades can be observed on the surfaces of single phase materials, which phenomenon is caused by the different crystallographic orientations of the grains. This paper shows a combined color etching electron backscatter diffraction (EBSD) investigation of cast iron. An area of the surface of a gray cast iron specimen was etched. Colors were characterized by their luminescence and their red, green and blue intensity. An EBSD orientation map was taken from the same area and the orientations of the individual grains were determined. Results showed that a strong correlation was found between the luminescence and the R, G, B intensity of the color and the angle between the specimen normal and the <100> direction, while such correlation was not observed between the color parameters and the <110 > and <111> directions, respectively. This indicates that film thickness is sensitive to the <100> direction of the crystal.

Original languageEnglish
Pages (from-to)814-817
Number of pages4
JournalMaterials Characterization
Volume61
Issue number8
DOIs
Publication statusPublished - Aug 2010

Fingerprint

shades
Etching
etching
Color
color
Cast iron
Electron diffraction
Luminescence
casts
luminescence
iron
Light interference
metal films
diffraction
Film thickness
analyzers
electrons
film thickness
Metals
interference

Keywords

  • Color etching
  • EBSD
  • Orientation
  • Spheroidic graphite steel

ASJC Scopus subject areas

  • Mechanical Engineering
  • Mechanics of Materials
  • Materials Science(all)
  • Condensed Matter Physics

Cite this

Correlation between grain orientation and the shade of color etching. / Szabó, P.; Kardos, I.

In: Materials Characterization, Vol. 61, No. 8, 08.2010, p. 814-817.

Research output: Contribution to journalArticle

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