High-temperature plasticity improvement by La addition during crack inhibition in laser powder bed fusion fabricated Haynes 230

This study investigates the high-temperature performance of Laser powder bed fusion (LPBF) – Haynes 230 alloy with trace La addition, addressing the issue of high-temperature ductility loss and establishing the relationship between microstructural evolution and mechanical properties at elevated temperatures. The La-containing deposited sample exhibited a 6% increase in tensile strength and a 27.2% improvement in elongation at room temperature. At 900°C, the elongation increased from 15.6% to 60.4% after hot isostatic pressing (HIP) treatment. The study also discusses the shift in deformation mechanisms, highlighting the formation of composite precipitates, nanotwins, and stacking faults. Notably, the stacking faults changed direction significantly when passing through annealing twin boundaries, which contributed to enhanced ductility. As the temperature increased, dislocation density decreased, and thermally stable La₂O₃ precipitated uniformly in the matrix. DFT calculations confirmed the formation of an amorphous layer at the La₂O₃ – matrix interface, which acted to pin dislocation sources, improving high-temperature ductility. The strengthening effect was primarily attributed to the inhibition of dislocation slip by the composite precipitates, annealing twins, and La₂O₃ precipitates. This study provides new insights into the optimisation of LPBF – Haynes 230 alloy for high-temperature applications.