Effect of Austenite Stability on the Hole Expansion Behavior of δ-TRIP Steels

Abstract This paper deals with the assessment of stability of retained austenite in δ-TRIP steels at two different isothermal holding time durations. Longer holding time leads to an improvement in austenite stability by greater carbon enrichment. This caused a significant increase in hole expansion ratio at a tensile strength of 800 MPa. Microstructure mediated approach was employed to characterize the difference arising from different holding durations. The deformation induced transformation of austenite into martensite mapped on the specimens after hole expansion proved that the austenite stability plays a significant role for the hole expandability of δ-TRIP steels.