PUBLICATION: MATERIALS CHARACTERIZATION

AUTHORS: Lei, T; Jiang, L; Ye, XX; Li, CW; Liang, JP; Liu, F; Li, ZJ

 

The effects of W/Mo ratio on the microstructures of as-cast Nb-modified Hastelloy N alloys have been investigated systematically in this study. It was found that the dendritic morphologies are independent on W/Mo ratio, but the microsegregation behaviors and the primary precipitates in the interdendritic regions are greatly affected. The electron probe microanalyses revealed that W segregates to dendrite core regions, while Mo, Cr, Nb and C to the interdendritic regions. The microsegregation of elements becomes more severe with the W/Mo ratio increasing. The primary precipitates in the interdendritic regions were identified as MC/? eutectic phases in all alloys, and the MC carbide lamellae in the eutectic phases can be categorized into two types, namely thin (Nb, Mo)C ones in the three Mo-contained alloys and thick NbC ones in the Mo-free alloy. The sizes of MC/? eutectic phases change with the W/Mo ratio in the same manner as the solidification temperature region, and their number densities gradually increase with the W/Mo ratio increasing. Based on the thermodynamic calculations and solidification theory, the influencing mechanism of W/Mo ratio on the microstructures of as-cast Nbmodified Hastelloy N alloys was briefly discussed.

 

LINKS: http://dx.doi.org/10.1016/j.matchar.2021.111075