Effect of post-annealing temperature on the microstructure, texture, and mechanical properties of a deformed ferrite-martensite stainless steel

This research explores the impact of annealing on the microstructure, texture, and mechanical behavior of asymmetrically rolled dual-phase stainless steel. A dual-phase (ferrite-martensite) stainless steel sheet, 4 mm in thickness, underwent 60 % asymmetric cold rolling, followed by annealing at 600 °C, 700 °C, and 800 °C for 30 min. The findings revealed that at 600 °C, partial recrystallization took place, while at 800 °C, complete recrystallization and martensite island decomposition were observed. The presence of martensite islands contributed to a highly uniform microstructure across both the near-surface and mid-thickness regions. Texture analysis showed that as the annealing temperature increased, α-fiber ({hkl}<110>) and γ-fiber ({111}<uvw>) textures became predominant. Mechanical tests demonstrated a reduction in macrohardness and microhardness with increasing annealing temperature. Tensile tests indicated a trade-off between decreasing strength and increasing ductility at higher annealing temperatures. Work hardening rate analysis suggested a smoother hardness reduction at elevated temperatures, attributed to enhanced strain accommodation resulting from martensite decomposition and a decrease in defect density. Fractographic analysis showed that fracture surfaces evolved from heterogeneous structures at lower temperatures to a fully ductile morphology at 800 °C, characterized by deeper and more uniformly distributed dimples, signifying improved microstructural homogeneity. Among the examined samples, the 600-30 specimen exhibited the most favorable mechanical properties owing to its superior combination of high strength (∼1 GPa) and good ductility (∼15 %).