Combined Effect of Silicon Content, Prior Deformation and Partitioning Conditions on Retained Austenite and Mechanical Properties of a Quenched and Partitioned 0.4% C Advanced High-Strength Steel

Quenching and Partitioning (Q mechanical behavior was evaluated via tensile testing. The high Si content effectively suppressed cementite precipitation and bainite formation, enabling higher RA fractions of ∼20 vol.% at 300 °C and ∼17 vol.% at 250 °C, with 1000 s identified as the optimal partitioning time. In the low-Si steel, ∼14 vol.% RA was obtained at 250 °C after 1000 s, and 17 vol.% after 10000 s. Applied deformation resulted in higher RA fractions compared to non-deformed Q&P steels. However, up to 23 vol.% bainite formed in the low-Si steel at 300 °C, consuming the available austenite. Both steels exhibited pronounced TRIP behavior. The high-Si steel partitioned at 300 °C (1000 s) achieved an excellent strength–ductility balance (1822 MPa and 9.3% elongation), while the low-Si steel partitioned at 250 °C also demonstrated competitive performance, highlighting the positive role of deformation. • DQ&P processing increases retained austenite stability compared with Q&P • High Si (1.5 wt.%) suppresses cementite and bainite, stabilizing up to ∼20 vol.% RA • Prior deformation refines austenite grains and enhances RA stability in low-Si steel • Optimal properties achieved: UTS ≈ 1.8–2.0 GPa with ∼8–9% elongation