THE USE OF COLOR in metallography has a long history, with color micrographs published over the past eighty-some years. A number of general articles (Ref 1–15) have been published reviewing methods and applications.
Natural color is of use in only a few classic metallographic applications. Prior to the development of wavelength-dispersive spectrometers and energy-dispersive spectrometers used on electron microprobe analyzers and scanning
electron microscopes, the color of inclusions using different illumination modes was part of the identification schemes used. However, natural color has limited applicability.
Color can be created by optical methods, such as with polarized light and differential interference contrast illumination. Polarized light examination is extremely useful for studying the structure of certain metals, without etching, that have noncubic crystal structures, such as beryllium, hafnium, -titanium, uranium, and zirconium.
In many cases, polarized light can be used with etched specimens, regardless of their crystal structure, to produce color. Differential interference contrast reveals height differences between constituents and the matrix, but in most cases, the color is of esthetic value only.