• Lamellarization (QLT) significantly improves cryogenic toughness of marine 10Ni5CrMoV steel, lowering ductile–brittle transition temperature from −116°C to −130°C.
• Film-like reversed austenite formed at martensite boundaries refines the microstructure and reduces equivalent grain size, enhancing toughness.
• Kinetic analysis using JMAK model reveals that isothermal transformation is growth-controlled, with maximum reversed austenite at 750°C.
• Reversed austenite reduces martensite proportion and hinders crack propagation via transformation-induced plasticity, improving machinability.