B2+L12 2상 Ni­Al­Fe 합금의 미세조직 및 기계적 성질에 미치는 탄소 첨가의 영향

Abstract

Carbon and titanium were added in two-phase(B2+L1₂) Ni-Al-Fe alloys for carbides precipitation, and the additions of 0.2 wt.%C and 3 at.%Ti have been found to be the most adequate for the formation of carbides. Carbon-doped alloys showed more refined microstructure than other carbon free alloys. The carbides, which were formed in the as-cast microstructure showing equiaxed dendrites, appeared to play a role to suppress the grain growth and the coarsening of second phases. The NAF29-10 alloy including no carbides showed the lamellar type microstructure, while the NAF29-10-C alloy including carbides showed much more refined mesh type microstructure. When the carbon free alloys were quenched into water, cracks occurred at the grain boundaries probably due to martensitic transformation. However, these cracks were not observed in the carbon doped alloy. Therefore, the carbon doped alloys showed a good ductility at room temperature. They also showed much higher yield strength than other alloys without carbides through the whole temperature ranges.