Influence of Retained Austenite on the Fatigue Crack Growth Behavior of C‐Si‐Mn TRIP Steel

ABSTRACT Retained austenite is prevalently observed in advanced high‐strength steels and significantly affects the mechanical properties via transformation‐induced plasticity (TRIP) effect. How the characteristics of retained austenite, including the volume fraction, stability, and distribution of retained austenite on the fatigue crack growth behavior is of critical importance in practical applications and needs to be explored. In this paper, typical C‐Si‐Mn TRIP steels were quenched at different temperatures to obtain retained austenite of different volume fractions. Higher volume fractions and higher stability of retained austenite with lower spacing are all beneficial to improving fatigue cracking resistance. The austenite of high plasticity contributes to a high fatigue crack growth threshold, and while moderate TRIP effect would generate plasticity‐induced crack closure, the decrease of interfacial mismatch and local stress concentration relief step by step slow down the fatigue crack growth rate by eliminating early cracking induced by easy and abundant transformation of blocky austenite.