Quantitative Metallography in Test Method Standards and Product Specifications

Quantitative metallographic and stereological methods can be applied to microstructures observed with the light microscope. These methods, however, are not presently requested by product specifications, except in a few notable cases. For the most part, manually performed chart comparison methods, developed 50 to 60 years ago, are still specified.

Most laboratories that rely upon chart methods utilize poorly controlled metallographic procedures for specimen preparation. Image analysis using specimens prepared by these processes yield erratic, inaccurate and nonreproducible test results. Of course, this is attributed usually to the measurement method and equipment rather than to the specimen preparation procedures and their execution.

Specimen preparation, however, can be performed in a controlled, efficient manner with highly automated equipment. Image analysis measurements using specimens prepared with such equipment are accurate, precise, and reproducible. However, product specifications have not been updated to incorporate this new technology. In our quest for greater product quality, these methods are essential.