Macrostructure refers to the large-scale internal features of a metal component, such as grain flow, porosity, segregation, and deep cracks. Inspectors evaluate it by cutting a section, polishing it, and applying a heavy acid etch. Examining the macrostructure reveals how forging, casting, or heavy heat treating has shaped the bulk properties of the material.
Heard on the job
The macrostructure on this forged billet shows terrible grain flow near the flange.
Do not mix it up with
- Microstructure: Macrostructure is evaluated at 10X magnification or less to see bulk flow, while microstructure requires high magnification to see individual phases and grains.
Related terms
Microstructure
The internal arrangement of phases and grains in a metal visible only under magnification.
Cut and etch
Shop phrase for sectioning a sample part and etching it to check case depth or structure.
Grain size
The average size of the crystals in a metal, usually reported as an ASTM number where higher means finer.