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

Abstract

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 Y 2 O 3 @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° 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. • The Y-containing pre-alloyed powder was prepared by nitrogen atomization. • Primary precipitates in the powder were characterized by FIB and TEM. • Residual oxygen participated in the alloying reaction in the molten metal. • Formation mechanisms of oxides and cubic texture were revealed.