The role of austenite stability on the change of fracture mode in a dual-phase medium Mn steel having a lamellar microstructure

Overcoming the strength–formability trade-off in high strength steels via cryogenic treatment

“…After baking, both IA725-LN 2 and IA735-LN 2 specimens show increases in YS (by 71 MPa and 143 MPa for the IA725-LN 2 and IA735-LN 2 specimens, respectively) and elongation (by 6.9% and 4.1% for the IA725-LN 2 and IA735-LN 2 specimens, respectively). Previous studies showed that there is no apparent changes in the fraction of austenite in medium Mn TRIP steels subjected to baking treatments 29 , 30 . TEM analysis of the baked IA725-LN 2 specimen, however, shows that there is a precipitation of ε-carbide in martensite (Fig.…”

Nanosized Lamellar Structures and Tensile Properties of Intercritical‐Annealed Medium Mn Steels Containing Multiphases

“…Our previous study showed that the austenite and α ′ martensite in this alloy shared the K–S orientation relationship (OR). [ 29 ] Given the variant selection, there are 24 possible K–S orientations for the fresh α ′ martensite to form from the parent austenite; most of them will result in the new α ′ martensite orientations. However, in this study, it appears that the fresh α ′ martensite variant, which possesses a similar orientation with neighbor tempered‐ α ′ martensite, was preferentially chosen.…”

“…Naturally, this led to the increase in the effective α ′ martensite size of dislocation pileup, i.e., a summation of sizes of tempered‐ α ′, quenched‐ α ′, and DIM‐ α ′ martensite, inducing larger pileup stress at the high‐angle boundaries, especially the PAG boundaries. [ 29 ]…”

“…Finally, both samples were subjected to an additional baking treatment at 200 °C for 10 min to enhance the stability of retained austenite by carbon partitioning, followed by air cooling. [28,29] Specimens before and after baking are denoted as IA8 and IA16, IA8-baked and IA16-baked, respectively. All heat treatments were performed using quartz tube sealing in a box furnace, and the thermomechanical treatment process is schematically illustrated in Figure 2.…”

“…Nevertheless, an additional increase of the YS obtained by baking treatment should be considered for the baked specimens. During baking, C partitioned to the retained austenite and stabilized it; [28,29,42] C also segregated at the interphase boundaries, [42] strengthening the baked specimens. These beneficial effects of baking treatment on YS have been demonstrated in previous studies on various medium Mn steels even though the baking treatments were performed at relatively low temperatures (170 °C [42] and 200 °C [28,29] ) and for a short time.…”