Development of austenite-based high strength steels
This structure is normally only stable at high temperatures (>910oC in pure iron) and will transform to the bcc structure on cooling. However the temperature at which this transformation occurs decreases as the alloy content, particularly carbon, is increased. This can result in the presence of some austenite in the final microstructure. When austenite is present this increases the ductility at a given strength level.
TRIP (Transformation Induced Plasticity) are alloyed with silicon or aluminium to promote the retention of up to 15% austenite in the final microstructure. Strain during forming operations causes the ductile austenite to transform to martensite which explains the excellent combinations of strength and ductility shown by these materials.