M. Harper, Y. Kosaka, S. P. Fox, Timet, Henderson, NV
Heat tinting is a seldom-used metallographic technique whose usefulness may prove valuable when characterizing titanium alloys. Like other sample preparation techniques, heat tinting makes use of the differences in phase composition and crystal structure to gather information about microstructural features. Using a low temperature heat treatment to build an oxide film on a well-polished surface is the essence of this simple technique. The rate of film growth has been shown to vary with the crystallographic orientation of the underlying alpha and beta phases as well. Good color contrast is achieved when a heat tinted sample is viewed using polarized light. While the technique cannot reveal detailed orientation information, the result is a view of the effective structural unit size and shape of the material. These colorful results are compared to those of other characterization techniques to show that features such as texture bands may be seen without employing costly texture analysis. It is believed that the use of heat tinting as a quick and easy tool will provide supplemental information to typical microstructure characterization. In addition, the texture structure may be useful in further understanding the relationships of processing, microstructures, and properties.
Summary: Heat tinting is a simple metallographic technique characterized by developing an oxide film on a polished surface. The thickness of the oxide will reflect differences in phase orientation of the microstructure. Consequently, regions of simlarly oriented phases reflect similar colors when viewed using polarized light. This textural unit information is easily gained and useful when examining the process-property relationships of various product forms.