Improved High Temperature Stability of Fe12Cr6Al by adding Ti during Laser Powder Bed Fusion

This study explores the effects of heat treatment (1200 °C-1h) on various in-situ synthesized nitride and oxide precipitates in Fe12Cr6Al alloys, without and with-Ti, produced via Laser Powder Bed Fusion (LPBF). Furthermore, the impact of the in-situ synthesis precipitates such as Al₂O₃, AlN-O, AlN, AlTi-N, TiN, and TiN@Al₂O₃ on the microstructure and mechanical properties of samples without-Ti and with-Ti was analyzed before and after heat treatment. Before heat treatment, the without-Ti sample contained Al₂O₃, AlN-O, and AlN nano-precipitates; however, only AlN nano-precipitates remained post-treatment. In contrast, the with-Ti sample exhibited a transformation of AlTiN precipitates into TiN and TiN@Al₂O₃ precipitates after heat treatment. Grain size analysis revealed a modest increase in the without-Ti sample, from 71 μm to 76 μm, whereas the with-Ti sample showed an increase from 12 μm to 26 μm. Additionally, the size of AlN nano-precipitates increased from 33 nm to 84 nm, while TiN nano-precipitates grew from 57 nm to 93 nm. Mechanically, heat treatment reduced the yield strength (YS) and ultimate tensile strength (UTS) of both samples. YS and UTS decreased by approximately 36% and 19% for the without-Ti sample, respectively, while the reductions were around 28% and 20% for the with-Ti sample. Despite these decreases, elongation improved, increasing by 3.5% in the without-Ti sample and by 4% in the with-Ti sample. The Vickers hardness (HV) also declined, with reductions of approximately 7% for the without-Ti sample and 10% for the with-Ti sample. This study offers comprehensive insights into the evolution of nitride and oxide nanoprecipitates during heat treatment and their influence on the properties of the Fe-12Cr-6Al alloy, contributing valuable knowledge to the existing literature.