Metastable Miscibility Gap of Fe-Mo-Ni Ternary Alloy System

Phase decomposition and metastable miscibility gap in the Fe-Mo-Ni ternary system were investigated by means of transmission electron microscopy, X-ray diffraction and hardness measurement. The results obtained are as follows:(1) At 773 K, spinodal decomposition occurs in Fe-16 at%Mo-Ni alloys containing Ni more than 4 at%, in Fe-14 at%Mo-Ni alloys containing Ni more than 8 at% and in Fe-12 at%Mo-12 at%Ni alloy.(2) At 773 K, a plate-shaped zone appears by the nucleation and growth mechanism in Fe-16 at%Mo-Ni alloys containing 0∼2 at%Ni, Fe-14 at%Mo-Ni alloys containing 2∼6 at%Ni, Fe-12 at%Mo-Ni alloys containing 4∼10 at%Ni and Fe-10 at%Mo-10 at%Ni alloy.(3) The coherent spinodal temperatures of Fe-12 at%Mo-8 at%Ni, Fe-14 at%Mo-8 at%Ni and Fe-16 at%Mo-8 at%Ni alloys are estimated at 740, 790 and 845 K, respectively.(4) The coherent spinodal temperature of Fe-Mo binary system is raised about 15 K by the addition of 1 at%Ni.(5) The plate-shaped zone is formed in the temperature range of about 50∼100 K above the spinodal temperature.