Laser-based powder bed fusion of pre-alloyed oxide dispersion strengthened steel containing yttrium

In this study, the pre-alloyed powder Fe-22Cr-5.1Al-0.5Ti-0.26Y (wt%) was prepared by nitrogen atomization and characterized with the aid of focused ion beam (FIB) and transmission electron microscopy (TEM). The oxide dispersion strengthened (ODS) bulk material was successfully fabricated using laser-based powder bed fusion (PBF-LB). Micro-scale Y-Al-O complex oxides and nanoscale Y2O3 @TiN core-shell structures were found in the as-built material. The importance of the presence of residual oxygen in the atomization system and the building chamber for the formation of dual-scale secondary phases was revealed. In addition, the formation mechanism of the dual-scale secondary phases was elucidated by investigating the phase and composition of the as-built ODS steel. Columnar crystals with {001} < 100 > cubic alignments grew epitaxially from the bottom of the molten pool during the PBF-LB process, forming a weak cubic texture in the as-built material. This cubic texture led to anisotropic tensile properties of the as-built material, where the room-temperature ultimate tensile strength in the XY-45 degrees direction was higher than that in the building direction (Z). Our work provides a feasible scheme to shorten the preparation process of ODS alloys, which is usually carried out using complicated means.

Automated summary

In this study, a pre-alloyed Fe-22Cr-5.1Al-0.5Ti-0.26Y (wt%) powder was prepared using nitrogen atomization and characterized using FIB and TEM. An oxide dispersion strengthened bulk material was successfully fabricated using laser-based powder bed fusion. Micro-scale Y-Al-O complex oxides and nanoscale Y2O3 @TiN core-shell structures were observed in the fabricated material. The presence of residual oxygen in the atomization system and building chamber was found to be important for the formation of dual-scale secondary phases. The formation mechanism of the dual-scale secondary phases was elucidated through phase and composition analysis of the fabricated ODS steel. Epitaxial growth of columnar crystals with {001} < 100 > cubic alignments from the bottom of the molten pool during the PBF-LB process led to a weak cubic texture in the fabricated material. This cubic texture resulted in anisotropic tensile properties of the fabricated material.