Retained austenite

The austenite which has not transformed to martensite after certain steels have been hardened and cooled to room temperature.

Generally it is the high-carbon, high-alloy steels that suffer from retained austenite. The faster a steel is quenched, the less austenite will be retained. High alloy steels tend to be oil quenched rather than water quenched, which is required for hardening plain carbon steels.

Retained austenite can be transformed by sub-zero treating or tempering at temperatures above about 570ºC.

See also Mf temperature.