Microstructure and mechanical properties of additive manufactured Inconel 718 alloy strengthened by oxide dispersion with 0.3 wt% Sc addition

Abstract

Additively manufactured superalloys have attracted increasing attention due to their inherent hierarchical microstructure, but have been impeded by anisotropic properties originating from columnar grains. In this work, we present a strategy for inhibiting the formation of columnar grains in which 0.3 wt% scandium (Sc) was introduced as an oxide dispersion strengthener (ODS) into the Inconel 718 (IN718) alloy fabricated via laser powder bed fusion (LPBF). The effects of Sc on the microstructure and mechanical properties of the IN718 were investigated, revealing the in-situ formation of Sc 2 O 3 nanoparticles as well as the cellular sub-grains microstructure with high-density of dislocations into the as-prepared IN718-Sc alloy. The addition of Sc disrupted the typical columnar grains generated by the LPBF process, resulting in, the strong (100) texture in pure IN718 alloy changing to the irregular orientation in IN718-Sc alloy. In addition, the average grain size and the aspect ratio also show decreases when Sc introduction. As a result, the as-designed IN718-Sc alloy achieved a higher yield strength of 1030 MPa at room temperature and 837 MPa at 650 ºC, respectively, which can be attributed to Zener pinning of grain boundaries by dispersed Sc 2 O 3 nanoparticles. Importantly, the insight into dispersing oxide particles to regulate microstructure and improve properties in this study could provide guidance for other alloy fabrication through powder additive manufacturing. • Generating in situ rare earth oxides as nucleating agent, the columnar grains trend was suppressed. • With Sc addition, the grain size was refined and Sc 2 O 3 was generated to pin dislocation. • IN718-Sc exhibited a 20% increase in yield strength at room temperature and high temperature.