Phase Equilibria between γ-Fe (A1) and Fe_2Ti Laves (C14) Phases and Microstructure in Fe-Ti-Ni Ternary System at Elevated Temperatures

摘要

The phase equilibria among α-Fe, γ-Fe and Fe_2Ti phases in Fe-Ti-Ni ternary system at 1473 K and 1373 K with Ni (γ former element) addition were examined, by paying attention to the γ+Fe_2 Ti two-phase region. The Fe_2Ti single-phase region extends toward the equal-titanium concentration direction up to about 30 at% Ni, and the Laves phase becomes in equilibrium with γ-Fe by 12 at% Ni addition, but the γ+Fe_2Ti two-phase region is limited because of the formation of liquid phase by further Ni addition at 1473 K. With decreasing temperature, a ternary eutectic reaction (L→γ-Fe+Fe_2Ti+Ni_3Ti) occurs, making the two-phase region wider just below the invariant reaction at 1373 K, and the region becomes narrower again by the enlargement of the three-phases region toward Fe-rich side.