| Popis: |
To explore the optimal hot ductility regimes of a low-carbon bearing duplex stainless steel, we conducted tensile tests using a Gleeble 3500 simulator within a temperature range spanning from 900 °C to 1250 °C and a strain rate of 10 s−1, mimicking industrial conditions. Analysis of mechanical properties revealed the presence of three distinct zones, each intricately linked to microstructural variations. Employing thorough two-dimensional (2D) characterization enabled detailed crack analyses, unveiling a decrease in crack density with rising temperatures. Interestingly, precipitation effects only became prominent at higher temperatures, contrasting with δ/γ interface decohesion as the primary cause of cracking at lower temperatures. Subsequent three-dimensional (3D) analyses corroborated these observations. Large-area (>1 mm2) electron backscatter diffraction (EBSD) mappings, along with grain orientation spread (GOS) analyses, shed light on dynamic recrystallization (DRX) and dynamic recovery (DRV) mechanisms in both ferrite and austenite phases. Contrary to prevailing theories, our findings suggest the coexistence of DRX and DRV for both phases. Notably, at higher deformation temperatures, DRX prevails in both ferrite and austenite, whereas at lower temperatures, DRV becomes more dominant in austenite, leading to strain buildups in austenite and strain incompatibility between δ/γ interfaces. The identification of a critical temperature at 1100 °C underscores the vulnerability of δ/γ interfaces to crack formation, potentially compromising the material's workability. These insights deepen our understanding of hot ductility behaviour in low-carbon bearing duplex stainless steel, offering valuable guidance for industrial applications and process optimization. |
