The microscopic arrangement of a material's grains, phases, and defects. In heat treating, manipulating the microstructure is the entire goal of the process, as the specific mixture of phases like martensite, bainite, or ferrite dictates the mechanical properties of the finished part. It is typically evaluated by cutting, polishing, and etching a sample, then examining it under an optical or electron microscope.
The lab report shows a fully martensitic microstructure at the case depth, so the quench was fast enough.
Related terms
Metallography
The scientific study of the physical structure and components of metals using microscopy.
Martensite
The hard, needle-like phase that forms when austenite is quenched fast enough to trap its carbon.
Grain size
The average size of the crystals in a metal, usually reported as an ASTM number where higher means finer.
Cut and etch
Shop phrase for sectioning a sample part and etching it to check case depth or structure.