This list of terms, with accompanying photomicrographs where appropriate, is intended as a guide for use in the preparation of material specifications.

The terms and photomicrographs are intended to present definitions only; they do not define either acceptance limits or minimum standards of quality.

Listings are not grouped by specific alloys or conditions and represent the typical microstructures wherever they occur.

Etchants used for the microstructures shown are stated. Where "Krolls" is stated, the composition is 10 ml HF, 30 ml HNO₃, and 50 ml water (H₂O).

Other common etchants are listed in ASTM E 407, Microetching Metals and Alloys.