| About this Abstract |
| Meeting |
MS&T24: Materials Science & Technology
|
| Symposium
|
Austenite Formation and Decomposition V: A Symposium in Memory of Prof. Mats Hillert
|
| Presentation Title |
Delta-Ferrite to Austenite Phase Transformation Pathways in 2205 Duplex Stainless Steels Manufactured via Laser Powder Bed Fusion |
| Author(s) |
Cindy He, Nima Haghdadi, Sophie Primig |
| On-Site Speaker (Planned) |
Sophie Primig |
| Abstract Scope |
Laser powder bed fusion (LPBF) facilitates near net-shaped production of complex engineering components from duplex stainless steels (DSSs). DSSs are employed in harsh environments due to their mechanical and corrosion properties and equilibrium microstructure of roughly equal phase fractions of delta-ferrite and austenite. However, LPBF results in a highly non-equilibrium as-built microstructure with >99% delta-ferrite, high dislocation density, and abundant Cr2N precipitates. Upon a short heat treatment, different types of austenite (intergranular, instability-induced, sympathetic, and intragranular) are formed, reattaining a refined equilibrium microstructure. We apply 3D electron back-scatter diffraction to reveal the mechanisms of the delta-ferrite to austenite phase transformation and interface evolution. We show that non-Kurdjumov-Sachs/Nishiyama-Wassermann interfaces have lower grain boundary curvature, and that ferrite habit planes deviate from crystallographically and/or energetically favourable planes. The kinetics of the phase transformation is controlled by strain rather than interfacial energy minimization. This provides opportunities for microstructure design to unlock desirable properties. |