Insights into the role of retained austenite stability in TRIP-aided steel: Ductilizing and toughening

This study investigates the tensile and impact property of TRIP (transformation-induced plasticity)-aided steel with different retained austenite (RA) stability at different temperatures. The RA stability of experimental steels processed by hot rolling-coiling at 450 °C, short tempering and long duration tempering followed the sequence: un-temper (C450) < short (C450-ST) < long duration tempering (C450-LT). With the tempering time increases, the stability of RA gradually improves. The improvement of RA stability with different degrees resulted in significant improvements in ductility and toughness, respectively. These findings emphasize that maintaining uniform distribution of stable RA during different stages of tensile straining promotes continuous TRIP effect, resulting in an increased level of strain hardening and enhanced ductility. However, RA with higher stability experienced plastic deformation followed by TRIP effect during impact deformation, which effectively blunts the crack tips thereby inhibiting brittle fracture and leading to higher impact toughness. RA stability had a dual and important effect on ductility and toughness. Continuous and gradual TRIP effect enhanced ductility, while extensive and short-lived TRIP effect was detrimental to toughness.