https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Tue, 21 Apr 2026 13:58:36 GMT 2026-04-21T13:58:36Z http://hdl.handle.net/10985/26542 In Situ Monitoring of Retained Austenite Decomposition During Tempering of High-Strength Tool Steels DUMONT, Myriam; MESSAADI, Maha; LACHAL, Marine; QUIDORT, David; PERRUCHOT, Maxime; MALARD, Benoît; SCHELL, Norbert; MAAWAD, Emad; DELAGNES, Denis; DEHMAS, Moukrane This study investigates the decomposition of retained austenite (RA) in tool steels for plastic molding in correlation with the alloy chemical composition and the tempering parameters. Two grades differing in their silicon content with initial mixed bainitic/martensitic microstructures were investigated using in situ synchrotron high-energy X-ray diffraction (HEXRD) during tempering in the 550 °C to 600 °C temperature range for one-hour holding time. Results indicated carbide formation during heating or isothermal holding; however, retained austenite remained untransformed up to the end of the tempering holding time in all investigated conditions for both grades. In situ HEXRD provides direct evidence of the transformation of retained austenite into fresh martensite on cooling from the tempering stage. This behavior is correlated to the evolution of carbon enrichment of retained austenite and the effect of silicon is discussed. Thu, 19 Jun 2025 00:00:00 GMT http://hdl.handle.net/10985/26542 2025-06-19T00:00:00Z DUMONT, Myriam MESSAADI, Maha LACHAL, Marine QUIDORT, David PERRUCHOT, Maxime MALARD, Benoît SCHELL, Norbert MAAWAD, Emad DELAGNES, Denis DEHMAS, Moukrane This study investigates the decomposition of retained austenite (RA) in tool steels for plastic molding in correlation with the alloy chemical composition and the tempering parameters. Two grades differing in their silicon content with initial mixed bainitic/martensitic microstructures were investigated using in situ synchrotron high-energy X-ray diffraction (HEXRD) during tempering in the 550 °C to 600 °C temperature range for one-hour holding time. Results indicated carbide formation during heating or isothermal holding; however, retained austenite remained untransformed up to the end of the tempering holding time in all investigated conditions for both grades. In situ HEXRD provides direct evidence of the transformation of retained austenite into fresh martensite on cooling from the tempering stage. This behavior is correlated to the evolution of carbon enrichment of retained austenite and the effect of silicon is discussed.